Midkine is a Potential Novel Biomarker for Acro-osteolysis in Systemic Sclerosis

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Donato, and 4 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4207415/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Background: Digital acro-osteolysis can result from ischemia and is a complication of systemic sclerosis (SSc). Midkine (MK) is an angiogenic growth factor that plays a key role in bone remodeling. The objective of this study was to examine serum MK level as a biomarker of acro-osteolysis in SSc. Methods: The study population consisted of patients who consented to undergo ethics approval at two institutions and had Raynaud's phenomenon (RP), abnormal capillaroscopy, and hand radiographs. Age- and sex-matched healthy controls without hypertension, Raynaud phenomenon, or digital lesions were included. Serum MK concentration was measured using an enzyme-linked immunosorbent assay. An analysis of variance test assessed the differences in MK concentrations among SSc patients with acro-osteolysis, SSc patients without acro-osteolysis, and age-and sex-matched healthy controls. Results: A total of 54 SSc registry patients and 20 age-sex matched healthy controls were included in the cross-sectional analysis of MK levels. Except for digital ulcers, there were no sociodemographic or clinical features that were statistically significantly associated with the presence of acro-osteolysis. There were significantly higher MK levels between SSc without acro-osteolysis than in acro-osteolysis (p=0.0001), as well as in SSc without acro-osteolysis and in healthy controls (p=0.01). There were no significant differences between SSc patients with acro-osteolysis and healthy controls (p=0.31). Conclusions: Our study suggests that MK may maintain an intact digital tip in SSc patients. A reduction in serum MK level is associated with progressive digital vasculopathy,defined by the presence of acro-osteolysis. Author Contributions: TMF, VG, GA, AJD, SW, RZ contributed to the design and implementation of the research analysis of the results and to the writing of the manuscript. TMF conceived the original and supervised the project. Systemic sclerosis Vasculopathy Acro-osteolysis Biomarker Midkine Figures Figure 1 Introduction Osteolysis of the distal phalanges of the hands and feet can affect the terminal tuft or the shaft of the distal phalanx. Digital acro-osteolysis can result from ischemia, digital calcinosis, or severe sensory neuropathy. Acro-osteolysis is associated with occupational activities, such as exposure to polyvinyl chloride, infections such as leprosy, endocrinopathies such as hyperparathyroidism, genetic disorders, lysosomal storage disorders, and rheumatic diseases, such as systemic sclerosis (SSc), which is an autoimmune disease characterized by progressive vasculopathy with resultant fibrosis [ 1 ]. Unfortunately, there is a paucity of data on the effective treatment of acro-osteolysis, especially in the context of recurrent ischemia-reperfusion injury, which is important for the pathogenesis of SSc [ 2 ]. It is of critical importance in SSc to identify when a digital tip is at risk of resorption prior to end-stage damage. Severe Raynaud’s phenomenon (RP), which is a vasospasm in the digits that is universally present in SSc, can result in digital complications, such as calcinosis, digital ischemia, and acro-osteolysis. The presence of calcinosis and digital ischemia have been reported to predict acro-osteolysis [ 2 ]. Vasodilators have been prescribed for the management of RP. Acro-osteolysis is the likely result of bone damage due to inadequate vasodilator response or sub-optimally treated vasculopathy. However, acro-osteolysis can occur despite pharmacologically controlled symptomatic RP, highlighting the importance of biomarkers for identifying acro-osteolysis [ 4 ]. The extraarticular location and lack of inflammation suggest that the mechanism underlying SSc-related acro-osteolysis may be hypoxia generated and pathologic bone remodeling [ 3 ]. Longitudinal studies assessing prognostic factors and predictors of SSc-acro-osteolysis are needed [ 2 ]. Plain radiography of the hands is the gold standard for the detection of acro-osteolysis, which is most often reported as present or absent, as none of the existing radiographic scales to grade osteolysis have been validated [ 2 ]. Ultrasonography is more sensitive for the detection of acro-osteolysis in patients with SSc. An increased Doppler signal adjacent to acro-osteolytic lesions in SSc may reflect the active process of osteogenesis [ 5 ]. In response to damage, bone remodeling requires coordinated activity of bone-forming osteoblasts and bone-resorbing osteoclasts to maintain bone mass and strength. Bone turnover markers, which are protein derivative biomarkers released during bone remodeling by osteoblasts or osteoclasts, are used as an adjunct for osteoporosis diagnosis and therapeutic monitoring and have been reported in SSc when compared to controls.[ 6 ] However, earlier menopause, corticosteroid use, malabsorption, and inflammation may be confounders in studies using bone turnover markers in SSc [ 7 ]. Therefore, predictive biomarkers that capture vascular and bone pathogenesis in ischemic digital lesions are needed [ 8 ]. There is increasing preclinical evidence that heparin/endothelial glycocalyx-binding molecule midkine (MK) plays a pathological role in hypertension, vascular disease, and bone pathology [ 9 ]. Although MK gene expression is generally weak in physiological homeostasis, it is strongly induced during acute oxidative stress, inflammation, and tissue repair [ 10 ]. Inflammatory cell recruitment by MK causes a variety of pathological changes, and blood levels of MK are reported to be potentially helpful markers of pathological disease activity [ 11 ]. MK may play an adaptive role in acute ischemia versus chronic disease states [ 9 ] and is considered an angiogenic growth factor that plays a key role in bone remodeling as a negative modulator of osteoblast function, and it is expressed during fracture repair [ 12 ]. Evidence suggests that MK acts as an internal modulator of autocrine and paracrine signals that maintain immune suppression, suggesting that the MK-modulated microenvironment is critically important for determining levels [ 13 ]. The objective of this study was to examine whether the serum MK level is a biomarker associated with acro-osteolysis in SSc. Methods Informed consent to participate was obtained from all of the participants in the study under Ethics Approval at the University of Utah (IRB #38705) and Tennessee Valley Healthcare System (IRB #1618579). The study population consisted of SSc registry patients who fulfilled the classification criteria set by the American College of Rheumatology (ACR) and European League Against Rheumatism (EULAR) [ 14 ] with Raynaud's phenomenon and abnormal capillaroscopy as part of disease classification and had hand radiographs consented under ethics approval at two institutions. Additionally, age-and sex-matched healthy controls from the University of Utah without hypertension, RP, or digital lesions were included (Utah IRB# 38705). Patients with hyperparathyroidism, exposure to polyvinyl chloride, and a history of other bone-related disorders or recent fractures were excluded to ensure that MK levels were primarily influenced by RP-mediated acro-osteolysis. All the enrolled participants underwent routine clinical assessment and serum collection. The Utah Translation Vascular Physiology Laboratory analyzed the concentration of MK using enzyme-linked immunosorbent assay (ELISA). The Human MK ELISA is a sandwich enzyme immunoassay. The incubation of standards and samples was carried out using microplate wells pre-coated with polyclonal anti-human MK antibody. After the standards and 1:2 diluted samples were incubated for 2.5 hours at room temperature (RT) with gentle shaking and washed, biotin labelled detection antibody was added and incubated with the captured MK for 1 h at RT with gentle shaking. Streptavidin-HRP conjugate was then added, followed by 45 min of incubation, and washing. The remaining HRP conjugate was allowed to react with the substrate solution (TMB) after 30 min of incubation at RT in the dark with gentle shaking. The reaction was halted by the addition of a stop solution, and a proportionate colored product was developed in relation to the amount of human MK present in the sample or standard. The absorbance was measured at 450 nm. A standard curve was generated from known concentrations of recombinant MK standards, and human MK concentrations were determined. An ANOVA test was used to assess the differences in midkine concentrations among SSc patients with acro-osteolysis, SSc patients without acro-osteolysis, and age-matched healthy controls. All samples were run simultaneously to avoid batch effects. Statistical significance was set at P < 0.05. Results There were 54 SSc registry patients with hand radiographs and 20 age-and sex-matched healthy controls included in the cross-sectional analysis of MK levels. The clinical features of patients with SSc are shown in Table 1 . Most participants were Caucasian females. All patients had a positive antinuclear antibody (ANA), and most had an SSc-specific autoantibody. Except for a history of digital ulcers, no sociodemographic or clinical features were significantly associated with the presence of acro-osteolysis. Nine participants had longitudinal data with repeat radiographs and follow-up serum samples available for the cohort. All longitudinal data were obtained from the Utah cohort. Table 1 Clinical features of the Systemic Sclerosis Population SSc Clinical Feature: SSc total population (n = 54) Acro-osteolysis (n = 30) No Acro-osteolysis (n = 24) P value Age (years), Mean (SD) 57 (11) 56 (9) 58 (15) 0.43 Sex: Female 44 (81%) 23 21 0.31 Race: • White • Black • Asian • Other 46 (85%) 5 (9%) 1 (2%) 2 (4%) 28 1 0 1 18 4 1 1 0.12 Disease duration (years) for non-Raynaud’s, Mean (SD) 12 (9) 13 (8) 12 (5) 0.61 Cutaneous Subset • Limited • Diffuse 37 (69%) 17 (31%) 19 10 18 7 0.76 ANA positive SSc autoantibody Subset • Centromere • RNA polymerase III • Topoisomerase 48 (100%) 21 (39%) 9 (17%) 3 (6%) 30 11 5 2 24 10 4 1 Digital Ulcers 23 (43%) 16 7 0.048 Calcinosis 12 (25%) 9 3 0.17 The MK levels of 20 healthy controls, 30 SSc patients with acro-osteolysis, and 24 SSc patients without acro-osteolysis are shown in Fig. 1 . There were significantly higher MK levels between SSc without acro-osteolysis compared to those with acro-osteolysis (p = 0.0001), as well as between SSc without acro-osteolysis and healthy controls (p = 0.01). There were no significant differences between SSc patients with acro-osteolysis and healthy controls (p = 0.31). Three of the 9 participants who had repeat hand radiographs available for review developed acro-osteolysis during the follow-up period. In this longitudinal cohort, three 3 participants that developed acro-osteolysis, as well as two participants without acro-osteolysis on follow-up imaging, had a decline in serum MK noted over the course. The other 4 participants without acro-osteolysis on follow-up imaging had stable or increased levels at the second assessment. While this sample size was too small for analysis, it is hypothesis-generating regarding the role of MK in osteoclastogenesis in the setting of ischemia. Conclusions The serum level of MK was different in patients with SSc with and without acro-osteolysis; higher levels correlated with an intact digital tip on radiography. This finding may reflect the disease activity of the digital vasculopathy in this patient population. Serum differences may be because MK is an angiogenic growth factor that plays a key role in bone remodeling. The association of elevated serum MK level with an intact digital tip may reflect the MK-modulated microenvironment of the digital tip prior to the presence of end-stage damage. Like other diseases, MK may be a driver of an immune evasive microenvironment, with high MK indicating an active inflammatory process with neo-angiogenesis [ 13 , 15 ]. A dynamic change may be indicative of an evolving disease, but further longitudinal studies are needed to draw this conclusion. Our study suggests that serum MK levels may be a biomarker of acro-osteolysis in SSc patients with RP and abnormal nailfold capillaroscopy at two SSc centers. While we did not have patterns of early, active, and late nailfold capillaroscopy patterns or patient-reported outcome data on RP severity in this cohort, we did have hand radiographs of all the analyzed participants. A musculoskeletal ultrasound protocol is planned in the future to allow better characterization of acro-osteolysis. We also did not have bone turnover markers or bone density measurements for our participants; this was also planned. Reliable biomarkers that can predict disease evolution are an unmet need in SSc, and deciding whether to treat the earliest vasculopathy phase of the disease is of critical importance [ 16 ]. The ability to identify a digit at risk for acro-osteolysis would greatly impact this disease, which places vascular injury critical to pathogenesis [ 17 ]. A study of the effects of vasodilators used to treat RP and acro-osteolysis on serum MK levels is indicated [ 9 ]. There are potentially important implications of serum MK levels as a biomarker of vasculopathy. The ability to identify the transition state of an intact digital tip to acro-osteolysis in SSc could impact clinical decision making. In the setting of ischemia-reperfusion injury, MK may initially act as a potent recruiter of leukocytes and promote cytotoxic T cell activation [ 18 ] but, this sustained response may inhibit bone formation. Thus, it is possible that after an acute increase in MK, the subsequent reduction in serum MK levels is indicative of a chronic, persistent injury. The effect of MK on the transcriptome and secretome of osteoblasts and its potential therapeutic impact in the context of immunomodulation are unclear in our study but are relevant in other studies of the disease microenvironment [ 13 ]. In conclusion, our study supports serum MK as a possible biomarker for understanding SSc digital vasculopathy, as well as normal bone physiology, which is an active area of research for diseases with similar features. Abbreviations ACR: American College of Rheumatology; ELISA: enzyme-linked immunosorbent assay; EULAR: European League Against Rheumatism; MK: Midkine; RP: Raynaud’s phenomenon: SSc: Systemic Sclerosis; VUMC: Vanderbilt University Medical Center Declarations Ethics approval and consent to participate: Informed consent to participate was obtained from all of the participants in the study under Ethics Approval at the University of Utah (IRB #38705) and Tennessee Valley Healthcare System (IRB #1618579) Consent for publication: Not applicable. Availability of data and materials: The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request. Competing Interests: None Funding: This work was supported by the Veterans’ Health Administration Merit: 5I01CX002111-03 (TMF). Authors' contributions: VRG, GA, AD, SW, AP, RZ, and TMF all had substantial contributions to the conception or design of the work; or the acquisition, analysis, or interpretation of data for the work; AND Drafting the work or reviewing it critically for important intellectual content; AND Final approval of the version to be published; AND Agreement to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. Acknowledgement: This work was supported by the Veterans’ Health Administration (VHA) Merit: 5I01CX002111-03 (TMF). Conflicts of Interest: None declared. References Botou A, Bangeas A, Alexiou I, Sakkas LI: Acro-osteolysis . Clin Rheumatol 2017, 36 :9-14. Guerra MG, Rodrigues M, Agueda A, Rodrigues J, Marona J, Violante A, Oliveira M: Osteolysis in Systemic Sclerosis: A Scoping Review . J Rheumatol 2023, 50 :863-872. Park JK, Fava A, Carrino J, Del Grande F, Rosen A, Boin F: Association of Acroosteolysis With Enhanced Osteoclastogenesis and Higher Blood Levels of Vascular Endothelial Growth Factor in Systemic Sclerosis . Arthritis Rheumatol 2016, 68 :201-209. Dourado E, Valido A: Progressive Acro-Osteolysis . J Clin Rheumatol 2023, 29 :e13. Freire V, Bazeli R, Elhai M, Campagna R, Pessis E, Avouac J, Allanore Y, Drape JL, Guerini H: Hand and wrist involvement in systemic sclerosis: US features . Radiology 2013, 269 :824-830. Atteritano M, Sorbara S, Bagnato G, Miceli G, Sangari D, Morgante S, Visalli E, Bagnato G: Bone mineral density, bone turnover markers and fractures in patients with systemic sclerosis: a case control study . PLoS One 2013, 8 :e66991. Loucks J, Pope JE: Osteoporosis in scleroderma . Semin Arthritis Rheum 2005, 34 :678-682. Chora I, Guiducci S, Manetti M, Romano E, Mazzotta C, Bellando-Randone S, Ibba-Manneschi L, Matucci-Cerinic M, Soares R: Vascular biomarkers and correlation with peripheral vasculopathy in systemic sclerosis . Autoimmun Rev 2015, 14 :314-322. Campbell VK, Gately RP, Krishnasamy R, Burg D, Robertson GR, Gray NA: Midkine and chronic kidney disease-associated multisystem organ dysfunctions . Nephrol Dial Transplant 2021, 36 :1577-1584. Zhang R, Pan Y, Fanelli V, Wu S, Luo AA, Islam D, Han B, Mao P, Ghazarian M, Zeng W, et al.: Mechanical Stress and the Induction of Lung Fibrosis via the Midkine Signaling Pathway . Am J Respir Crit Care Med 2015, 192 :315-323. Muramatsu T, Kadomatsu K: Midkine: an emerging target of drug development for treatment of multiple diseases . Br J Pharmacol 2014, 171 :811-813. Liedert A, Schinke T, Ignatius A, Amling M: The role of midkine in skeletal remodelling . Br J Pharmacol 2014, 171 :870-878. Cerezo-Wallis D, Contreras-Alcalde M, Troule K, Catena X, Mucientes C, Calvo TG, Canon E, Tejedo C, Pennacchi PC, Hogan S, et al.: Midkine rewires the melanoma microenvironment toward a tolerogenic and immune-resistant state . Nat Med 2020, 26 :1865-1877. van den Hoogen F, Khanna D, Fransen J, Johnson SR, Baron M, Tyndall A, Matucci-Cerinic M, Naden RP, Medsger TA, Jr., Carreira PE, et al.: 2013 classification criteria for systemic sclerosis: an American college of rheumatology/European league against rheumatism collaborative initiative . Ann Rheum Dis 2013, 72 :1747-1755. Guzel S, FB SC, Guzel EC, Kucukyalcin V, Kiziler AR, Cavusoglu C, Gulyasar T, Cinemre H, Aydemir B: Midkine levels and its relationship with atherosclerotic risk factors in essential hypertensive patients . Niger J Clin Pract 2018, 21 :894-900. Bellando-Randone S, Matucci-Cerinic M: Very early systemic sclerosis . Best Pract Res Clin Rheumatol 2019, 33 :101428. Fleming JN, Nash RA, Mahoney WM, Jr., Schwartz SM: Is scleroderma a vasculopathy? Curr Rheumatol Rep 2009, 11 :103-110. Masuda T, Maeda K, Sato W, Kosugi T, Sato Y, Kojima H, Kato N, Ishimoto T, Tsuboi N, Uchimura K, et al.: Growth Factor Midkine Promotes T-Cell Activation through Nuclear Factor of Activated T Cells Signaling and Th1 Cell Differentiation in Lupus Nephritis . Am J Pathol 2017, 187 :740-751. Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-4207415","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":306983138,"identity":"cd5cb73e-d828-43c5-8b3b-49352c4c1e60","order_by":0,"name":"Venkateswara R Gogulamudi","email":"","orcid":"","institution":"Veterans Affairs Medical Center-Salt Lake City","correspondingAuthor":false,"prefix":"","firstName":"Venkateswara","middleName":"R","lastName":"Gogulamudi","suffix":""},{"id":306983139,"identity":"6b4ec4b9-0570-4c71-9d2c-7f3ce2cc4ae8","order_by":1,"name":"Ganiat Adeogun","email":"","orcid":"","institution":"Vanderbilt University Medical Center","correspondingAuthor":false,"prefix":"","firstName":"Ganiat","middleName":"","lastName":"Adeogun","suffix":""},{"id":306983140,"identity":"e9e60098-36fd-491d-8d94-42bd06d88aaf","order_by":2,"name":"Anthony J. Donato","email":"","orcid":"","institution":"University of Utah","correspondingAuthor":false,"prefix":"","firstName":"Anthony","middleName":"J.","lastName":"Donato","suffix":""},{"id":306983141,"identity":"c61a9cd1-551a-4aa6-b7a3-f5280da0dab1","order_by":3,"name":"Aaron Petrey","email":"","orcid":"","institution":"University of Utah Molecular Medicine Program","correspondingAuthor":false,"prefix":"","firstName":"Aaron","middleName":"","lastName":"Petrey","suffix":""},{"id":306983142,"identity":"eb8137b6-01f2-424b-bb2a-55140691376d","order_by":4,"name":"Sarah Wood","email":"","orcid":"","institution":"Vanderbilt University Medical Center","correspondingAuthor":false,"prefix":"","firstName":"Sarah","middleName":"","lastName":"Wood","suffix":""},{"id":306983143,"identity":"8022e6eb-6368-453f-8863-12fc2d0f54b7","order_by":5,"name":"Roy Zent","email":"","orcid":"","institution":"Tennessee Valley Health Care System Veterans Affairs","correspondingAuthor":false,"prefix":"","firstName":"Roy","middleName":"","lastName":"Zent","suffix":""},{"id":306983144,"identity":"7f04d80b-7b85-4e4b-a082-38063f59ad30","order_by":6,"name":"Tracy M. Frech","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA2klEQVRIiWNgGAWjYPACOSDmYXxAlFoeCGUMYjIbkKyFTYIoLfbShx9+5mEwyOdnP3usmrdtmzwDe+/jF3ht4UszlgZqsZzZk5d2m7fttmEDz3EzC7xaeBjMmHkY/hgY3OAxuzmz7XYCg0QaG15P8fCwfwNqMTCwB2opJFILjxlYi4EEjxnDR4gW5gd4tZzhKZacA9JxJsdY4sO524ZtPMfY8OlgYO9h3/jhTYWBAX/7GcMPCWW35fnZ25g/4NUDBEw8yG4HWkE4ghh/oAkQtmUUjIJRMApGFAAAhZY5+3XvvNoAAAAASUVORK5CYII=","orcid":"","institution":"Tennessee Valley Health Care System Veterans Affairs","correspondingAuthor":true,"prefix":"","firstName":"Tracy","middleName":"M.","lastName":"Frech","suffix":""}],"badges":[],"createdAt":"2024-04-02 14:32:17","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4207415/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4207415/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":57448936,"identity":"20d485c7-fd38-4e57-a2de-eabb2bbae545","added_by":"auto","created_at":"2024-05-30 20:02:23","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":27860,"visible":true,"origin":"","legend":"\u003cp\u003eMidkine levels in Healthy Controls (n=20), and Systemic Sclerosis patients with (n=30) and without acro-osteolysis (n=24)\u003c/p\u003e","description":"","filename":"1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-4207415/v1/eeeb1c73c76b4cfba48808e7.jpg"},{"id":61194809,"identity":"37c6b09f-ad9b-40b9-bc94-c3c3b2218ca5","added_by":"auto","created_at":"2024-07-26 21:31:26","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":678993,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4207415/v1/555f17f8-3529-483f-bf6e-3d7f7182de79.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Midkine is a Potential Novel Biomarker for Acro-osteolysis in Systemic Sclerosis","fulltext":[{"header":"Introduction","content":"\u003cp\u003eOsteolysis of the distal phalanges of the hands and feet can affect the terminal tuft or the shaft of the distal phalanx. Digital acro-osteolysis can result from ischemia, digital calcinosis, or severe sensory neuropathy. Acro-osteolysis is associated with occupational activities, such as exposure to polyvinyl chloride, infections such as leprosy, endocrinopathies such as hyperparathyroidism, genetic disorders, lysosomal storage disorders, and rheumatic diseases, such as systemic sclerosis (SSc), which is an autoimmune disease characterized by progressive vasculopathy with resultant fibrosis [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Unfortunately, there is a paucity of data on the effective treatment of acro-osteolysis, especially in the context of recurrent ischemia-reperfusion injury, which is important for the pathogenesis of SSc [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eIt is of critical importance in SSc to identify when a digital tip is at risk of resorption prior to end-stage damage. Severe Raynaud\u0026rsquo;s phenomenon (RP), which is a vasospasm in the digits that is universally present in SSc, can result in digital complications, such as calcinosis, digital ischemia, and acro-osteolysis. The presence of calcinosis and digital ischemia have been reported to predict acro-osteolysis [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Vasodilators have been prescribed for the management of RP. Acro-osteolysis is the likely result of bone damage due to inadequate vasodilator response or sub-optimally treated vasculopathy. However, acro-osteolysis can occur despite pharmacologically controlled symptomatic RP, highlighting the importance of biomarkers for identifying acro-osteolysis [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. The extraarticular location and lack of inflammation suggest that the mechanism underlying SSc-related acro-osteolysis may be hypoxia generated and pathologic bone remodeling [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. Longitudinal studies assessing prognostic factors and predictors of SSc-acro-osteolysis are needed [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e].\u003c/p\u003e \u003cp\u003ePlain radiography of the hands is the gold standard for the detection of acro-osteolysis, which is most often reported as present or absent, as none of the existing radiographic scales to grade osteolysis have been validated [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Ultrasonography is more sensitive for the detection of acro-osteolysis in patients with SSc. An increased Doppler signal adjacent to acro-osteolytic lesions in SSc may reflect the active process of osteogenesis [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. In response to damage, bone remodeling requires coordinated activity of bone-forming osteoblasts and bone-resorbing osteoclasts to maintain bone mass and strength. Bone turnover markers, which are protein derivative biomarkers released during bone remodeling by osteoblasts or osteoclasts, are used as an adjunct for osteoporosis diagnosis and therapeutic monitoring and have been reported in SSc when compared to controls.[\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e] However, earlier menopause, corticosteroid use, malabsorption, and inflammation may be confounders in studies using bone turnover markers in SSc [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. Therefore, predictive biomarkers that capture vascular and bone pathogenesis in ischemic digital lesions are needed [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThere is increasing preclinical evidence that heparin/endothelial glycocalyx-binding molecule midkine (MK) plays a pathological role in hypertension, vascular disease, and bone pathology [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. Although MK gene expression is generally weak in physiological homeostasis, it is strongly induced during acute oxidative stress, inflammation, and tissue repair [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. Inflammatory cell recruitment by MK causes a variety of pathological changes, and blood levels of MK are reported to be potentially helpful markers of pathological disease activity [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. MK may play an adaptive role in acute ischemia versus chronic disease states [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e] and is considered an angiogenic growth factor that plays a key role in bone remodeling as a negative modulator of osteoblast function, and it is expressed during fracture repair [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. Evidence suggests that MK acts as an internal modulator of autocrine and paracrine signals that maintain immune suppression, suggesting that the MK-modulated microenvironment is critically important for determining levels [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. The objective of this study was to examine whether the serum MK level is a biomarker associated with acro-osteolysis in SSc.\u003c/p\u003e"},{"header":"Methods","content":"\u003cp\u003e \u003cstrong\u003eInformed consent\u003c/strong\u003e \u003cp\u003e to participate was obtained from all of the participants in the study under Ethics Approval at the University of Utah (IRB #38705) and Tennessee Valley Healthcare System (IRB #1618579). The study population consisted of SSc registry patients who fulfilled the classification criteria set by the American College of Rheumatology (ACR) and European League Against Rheumatism (EULAR) [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e] with Raynaud's phenomenon and abnormal capillaroscopy as part of disease classification and had hand radiographs consented under ethics approval at two institutions. Additionally, age-and sex-matched healthy controls from the University of Utah without hypertension, RP, or digital lesions were included (Utah IRB# 38705). Patients with hyperparathyroidism, exposure to polyvinyl chloride, and a history of other bone-related disorders or recent fractures were excluded to ensure that MK levels were primarily influenced by RP-mediated acro-osteolysis. All the enrolled participants underwent routine clinical assessment and serum collection.\u003c/p\u003e \u003c/p\u003e \u003cp\u003eThe Utah Translation Vascular Physiology Laboratory analyzed the concentration of MK using enzyme-linked immunosorbent assay (ELISA). The Human MK ELISA is a sandwich enzyme immunoassay. The incubation of standards and samples was carried out using microplate wells pre-coated with polyclonal anti-human MK antibody. After the standards and 1:2 diluted samples were incubated for 2.5 hours at room temperature (RT) with gentle shaking and washed, biotin labelled detection antibody was added and incubated with the captured MK for 1 h at RT with gentle shaking. Streptavidin-HRP conjugate was then added, followed by 45 min of incubation, and washing. The remaining HRP conjugate was allowed to react with the substrate solution (TMB) after 30 min of incubation at RT in the dark with gentle shaking. The reaction was halted by the addition of a stop solution, and a proportionate colored product was developed in relation to the amount of human MK present in the sample or standard. The absorbance was measured at 450 nm. A standard curve was generated from known concentrations of recombinant MK standards, and human MK concentrations were determined. An ANOVA test was used to assess the differences in midkine concentrations among SSc patients with acro-osteolysis, SSc patients without acro-osteolysis, and age-matched healthy controls. All samples were run simultaneously to avoid batch effects. Statistical significance was set at P\u0026thinsp;\u0026lt;\u0026thinsp;0.05.\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003eThere were 54 SSc registry patients with hand radiographs and 20 age-and sex-matched healthy controls included in the cross-sectional analysis of MK levels. The clinical features of patients with SSc are shown in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. Most participants were Caucasian females. All patients had a positive antinuclear antibody (ANA), and most had an SSc-specific autoantibody. Except for a history of digital ulcers, no sociodemographic or clinical features were significantly associated with the presence of acro-osteolysis. Nine participants had longitudinal data with repeat radiographs and follow-up serum samples available for the cohort. All longitudinal data were obtained from the Utah cohort.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eClinical features of the Systemic Sclerosis Population\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"5\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSSc Clinical Feature:\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eSSc total population (n\u0026thinsp;=\u0026thinsp;54)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eAcro-osteolysis (n\u0026thinsp;=\u0026thinsp;30)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eNo Acro-osteolysis\u003c/p\u003e \u003cp\u003e(n\u0026thinsp;=\u0026thinsp;24)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eP value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eAge (years), Mean (SD)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e57 (11)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e56 (9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e58 (15)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.43\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eSex: Female\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e44 (81%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e23\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e21\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.31\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eRace:\u003c/p\u003e \u003cp\u003e\u0026bull; White\u003c/p\u003e \u003cp\u003e\u0026bull; Black\u003c/p\u003e \u003cp\u003e\u0026bull; Asian\u003c/p\u003e \u003cp\u003e\u0026bull; Other\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e46 (85%)\u003c/p\u003e \u003cp\u003e5 (9%)\u003c/p\u003e \u003cp\u003e1 (2%)\u003c/p\u003e \u003cp\u003e2 (4%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e28\u003c/p\u003e \u003cp\u003e1\u003c/p\u003e \u003cp\u003e0\u003c/p\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e18\u003c/p\u003e \u003cp\u003e4\u003c/p\u003e \u003cp\u003e1\u003c/p\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.12\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDisease duration (years) for non-Raynaud\u0026rsquo;s,\u003c/p\u003e \u003cp\u003eMean (SD)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e12 (9)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e13 (8)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e12 (5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.61\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCutaneous Subset\u003c/p\u003e \u003cp\u003e\u0026bull; Limited\u003c/p\u003e \u003cp\u003e\u0026bull; Diffuse\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e37 (69%)\u003c/p\u003e \u003cp\u003e17 (31%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e19\u003c/p\u003e \u003cp\u003e10\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e18\u003c/p\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.76\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eANA positive\u003c/p\u003e \u003cp\u003eSSc autoantibody Subset\u003c/p\u003e \u003cp\u003e\u0026bull; Centromere\u003c/p\u003e \u003cp\u003e\u0026bull; RNA polymerase III\u003c/p\u003e \u003cp\u003e\u0026bull; Topoisomerase\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e48 (100%)\u003c/p\u003e \u003cp\u003e21 (39%)\u003c/p\u003e \u003cp\u003e9 (17%)\u003c/p\u003e \u003cp\u003e3 (6%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e30\u003c/p\u003e \u003cp\u003e11\u003c/p\u003e \u003cp\u003e5\u003c/p\u003e \u003cp\u003e2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e24\u003c/p\u003e \u003cp\u003e10\u003c/p\u003e \u003cp\u003e4\u003c/p\u003e \u003cp\u003e1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDigital Ulcers\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e23 (43%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e16\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e7\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.048\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eCalcinosis\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e12 (25%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e9\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.17\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eThe MK levels of 20 healthy controls, 30 SSc patients with acro-osteolysis, and 24 SSc patients without acro-osteolysis are shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e. There were significantly higher MK levels between SSc without acro-osteolysis compared to those with acro-osteolysis (p\u0026thinsp;=\u0026thinsp;0.0001), as well as between SSc without acro-osteolysis and healthy controls (p\u0026thinsp;=\u0026thinsp;0.01). There were no significant differences between SSc patients with acro-osteolysis and healthy controls (p\u0026thinsp;=\u0026thinsp;0.31). Three of the 9 participants who had repeat hand radiographs available for review developed acro-osteolysis during the follow-up period. In this longitudinal cohort, three 3 participants that developed acro-osteolysis, as well as two participants without acro-osteolysis on follow-up imaging, had a decline in serum MK noted over the course. The other 4 participants without acro-osteolysis on follow-up imaging had stable or increased levels at the second assessment. While this sample size was too small for analysis, it is hypothesis-generating regarding the role of MK in osteoclastogenesis in the setting of ischemia.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eThe serum level of MK was different in patients with SSc with and without acro-osteolysis; higher levels correlated with an intact digital tip on radiography. This finding may reflect the disease activity of the digital vasculopathy in this patient population. Serum differences may be because MK is an angiogenic growth factor that plays a key role in bone remodeling. The association of elevated serum MK level with an intact digital tip may reflect the MK-modulated microenvironment of the digital tip prior to the presence of end-stage damage. Like other diseases, MK may be a driver of an immune evasive microenvironment, with high MK indicating an active inflammatory process with neo-angiogenesis [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. A dynamic change may be indicative of an evolving disease, but further longitudinal studies are needed to draw this conclusion.\u003c/p\u003e \u003cp\u003eOur study suggests that serum MK levels may be a biomarker of acro-osteolysis in SSc patients with RP and abnormal nailfold capillaroscopy at two SSc centers. While we did not have patterns of early, active, and late nailfold capillaroscopy patterns or patient-reported outcome data on RP severity in this cohort, we did have hand radiographs of all the analyzed participants. A musculoskeletal ultrasound protocol is planned in the future to allow better characterization of acro-osteolysis. We also did not have bone turnover markers or bone density measurements for our participants; this was also planned.\u003c/p\u003e \u003cp\u003eReliable biomarkers that can predict disease evolution are an unmet need in SSc, and deciding whether to treat the earliest vasculopathy phase of the disease is of critical importance [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. The ability to identify a digit at risk for acro-osteolysis would greatly impact this disease, which places vascular injury critical to pathogenesis [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. A study of the effects of vasodilators used to treat RP and acro-osteolysis on serum MK levels is indicated [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThere are potentially important implications of serum MK levels as a biomarker of vasculopathy. The ability to identify the transition state of an intact digital tip to acro-osteolysis in SSc could impact clinical decision making. In the setting of ischemia-reperfusion injury, MK may initially act as a potent recruiter of leukocytes and promote cytotoxic T cell activation [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e] but, this sustained response may inhibit bone formation. Thus, it is possible that after an acute increase in MK, the subsequent reduction in serum MK levels is indicative of a chronic, persistent injury. The effect of MK on the transcriptome and secretome of osteoblasts and its potential therapeutic impact in the context of immunomodulation are unclear in our study but are relevant in other studies of the disease microenvironment [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. In conclusion, our study supports serum MK as a possible biomarker for understanding SSc digital vasculopathy, as well as normal bone physiology, which is an active area of research for diseases with similar features.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003eACR: American College of Rheumatology; ELISA: enzyme-linked immunosorbent assay; EULAR: European League Against Rheumatism; MK: Midkine; RP: Raynaud\u0026rsquo;s phenomenon: SSc: Systemic Sclerosis; VUMC: Vanderbilt University Medical Center\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003eEthics approval and consent to participate: Informed consent to participate was obtained from all of the participants in the study under Ethics Approval at the University of Utah (IRB #38705) and Tennessee Valley Healthcare System (IRB #1618579)\u003c/p\u003e\n\u003cp\u003eConsent for publication: Not applicable.\u003c/p\u003e\n\u003cp\u003eAvailability of data and materials: The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.\u003c/p\u003e\n\u003cp\u003eCompeting Interests: None\u003c/p\u003e\n\u003cp\u003eFunding: This work was supported by the Veterans\u0026rsquo; Health Administration Merit: 5I01CX002111-03 (TMF). \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp; \u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAuthors\u0026apos; contributions: VRG, GA, AD, SW, AP, RZ, and TMF all \u0026nbsp;had substantial contributions to the conception or design of the work; or the acquisition, analysis, or interpretation of data for the work; AND Drafting the work or reviewing it critically for important intellectual content; AND Final approval of the version to be published; AND Agreement to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.\u003c/p\u003e\n\u003cp\u003eAcknowledgement: This work was supported by the Veterans\u0026rsquo; Health Administration (VHA) Merit: 5I01CX002111-03 (TMF).\u003c/p\u003e\n\u003cp\u003eConflicts of Interest: None declared.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eBotou A, Bangeas A, Alexiou I, Sakkas LI: \u003cstrong\u003eAcro-osteolysis\u003c/strong\u003e. \u003cem\u003eClin Rheumatol \u003c/em\u003e2017, \u003cstrong\u003e36\u003c/strong\u003e:9-14.\u003c/li\u003e\n\u003cli\u003eGuerra MG, Rodrigues M, Agueda A, Rodrigues J, Marona J, Violante A, Oliveira M: \u003cstrong\u003eOsteolysis in Systemic Sclerosis: A Scoping Review\u003c/strong\u003e. \u003cem\u003eJ Rheumatol \u003c/em\u003e2023, \u003cstrong\u003e50\u003c/strong\u003e:863-872.\u003c/li\u003e\n\u003cli\u003ePark JK, Fava A, Carrino J, Del Grande F, Rosen A, Boin F: \u003cstrong\u003eAssociation of Acroosteolysis With Enhanced Osteoclastogenesis 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risk factors in essential hypertensive patients\u003c/strong\u003e. \u003cem\u003eNiger J Clin Pract \u003c/em\u003e2018, \u003cstrong\u003e21\u003c/strong\u003e:894-900.\u003c/li\u003e\n\u003cli\u003eBellando-Randone S, Matucci-Cerinic M: \u003cstrong\u003eVery early systemic sclerosis\u003c/strong\u003e. \u003cem\u003eBest Pract Res Clin Rheumatol \u003c/em\u003e2019, \u003cstrong\u003e33\u003c/strong\u003e:101428.\u003c/li\u003e\n\u003cli\u003eFleming JN, Nash RA, Mahoney WM, Jr., Schwartz SM: \u003cstrong\u003eIs scleroderma a vasculopathy?\u003c/strong\u003e \u003cem\u003eCurr Rheumatol Rep \u003c/em\u003e2009, \u003cstrong\u003e11\u003c/strong\u003e:103-110.\u003c/li\u003e\n\u003cli\u003eMasuda T, Maeda K, Sato W, Kosugi T, Sato Y, Kojima H, Kato N, Ishimoto T, Tsuboi N, Uchimura K, et al.: \u003cstrong\u003eGrowth Factor Midkine Promotes T-Cell Activation through Nuclear Factor of Activated T Cells Signaling and Th1 Cell Differentiation in Lupus Nephritis\u003c/strong\u003e. \u003cem\u003eAm J Pathol \u003c/em\u003e2017, \u003cstrong\u003e187\u003c/strong\u003e:740-751.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Systemic sclerosis, Vasculopathy, Acro-osteolysis, Biomarker, Midkine","lastPublishedDoi":"10.21203/rs.3.rs-4207415/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4207415/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eBackground:\u003c/strong\u003e Digital acro-osteolysis can result from ischemia and is a complication of systemic sclerosis (SSc). Midkine (MK) is an angiogenic growth factor that plays a key role in bone remodeling. The objective of this study was to examine serum MK level as a biomarker of acro-osteolysis in SSc.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMethods: \u003c/strong\u003eThe study population consisted of patients who consented to undergo ethics approval at two institutions and had Raynaud's phenomenon (RP), abnormal capillaroscopy, and hand radiographs. Age- and sex-matched healthy controls without hypertension, Raynaud phenomenon, or digital lesions were included. Serum MK concentration was measured using an enzyme-linked immunosorbent assay. An analysis of variance test assessed the differences in MK concentrations among SSc patients with acro-osteolysis, SSc patients without acro-osteolysis, and age-and sex-matched healthy controls.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults:\u003c/strong\u003e A total of 54 SSc registry patients and 20 age-sex matched healthy controls were included in the cross-sectional analysis of MK levels. Except for digital ulcers, there were no sociodemographic or clinical features that were statistically significantly associated with the presence of acro-osteolysis. There were significantly higher MK levels between SSc without acro-osteolysis than in acro-osteolysis (p=0.0001), as well as in SSc without acro-osteolysis and in healthy controls (p=0.01). There were no significant differences between SSc patients with acro-osteolysis and healthy controls (p=0.31).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusions:\u003c/strong\u003e Our study suggests that MK may maintain an intact digital tip in SSc patients. A reduction in serum MK level is associated with progressive digital vasculopathy,defined by the presence of acro-osteolysis.\u003c/p\u003e\n\u003cp\u003eAuthor Contributions: TMF, VG, GA, AJD, SW, RZ contributed to the design and implementation of the research analysis of the results and to the writing of the manuscript. TMF conceived the original and supervised the project.\u003c/p\u003e","manuscriptTitle":"Midkine is a Potential Novel Biomarker for Acro-osteolysis in Systemic Sclerosis","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-05-30 20:02:18","doi":"10.21203/rs.3.rs-4207415/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"3fbe648c-a39a-4c0f-8e1d-acfbf1416ecc","owner":[],"postedDate":"May 30th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2024-07-26T21:23:20+00:00","versionOfRecord":[],"versionCreatedAt":"2024-05-30 20:02:18","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-4207415","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4207415","identity":"rs-4207415","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}