{"paper_id":"0a4040b9-8ed0-4774-9149-c128c4c3a760","body_text":"short review\nmemo (2020) 13:416–420\nhttps://doi.org/10.1007/s12254-020-00626-9\nFuture perspectives of fertility preservation in women\nBettina Böttcher · Katharina Winkler-Crepaz\nReceived: 3 April 2020 / Accepted: 28 May 2020 / Published online: 23 June 2020\n© The Author(s) 2020\nSummary Fertility preservation in women has be-\ncome well established over the last two decades. Nev-\nertheless, options for cancer survivors need to be im-\nproved to regain ovarian fun ctioning, ideally leading\nto pregnancy and live birth. T echniques to protect\nthe ovary from the damage of cytotoxic agents, to im-\nprove the survival of follicles in the ovarian graft, and\nto minimize the risk of re-seeding malignant cells after\novarian tissue transplantation are the object of current\nresearch all over the world. The demand for fertility\npreservation procedures in patients with benign dis-\neases like systemic lupus erythematosus before cyto-\ntoxic therapy, in patients with endometriosis before\nsurgery, and in patients with genetic predispositions\nwhich can lead to a premature ovarian failure will fur-\nther increase in coming years. In this short review,\nthese future perspectives are presented.\nKeywords Cancer survivors · Artificial ovary · In vitro\nmaturation · Follicular survival · Ovarian tissue\ncryopreservation\nIntroduction\nDespite rapid progress in fertility preservation tech-\nniques, existing applications need to be improved.\nWorldwide research continues to focus on develop-\ning agents which could protect the ovaries during\ncytotoxic therapy and m inimize gonadal damage\nB. Böttcher, MD, MA (/envelopeback)\nDepartment of Gynecological Endocrinology and\nReproductive Medicine, Medical University of Innsbruck,\nAnichstraße 35, 6020 Innsbruck, Austria\nbettina.boettcher@i-med.ac.at\nK. Winkler-Crepaz, MD\nDepartment of Obstetrics and Gynecology, Paracelsus\nMedical University, Müllner Hauptstraße 48, 5020 Salzburg,\nAustria\n(Sect. Gonadoprotective agents ), on enhancing fol-\nlicular survival after implantation of the ovarian graft\n(Sect. Increasing follicular survival after implantation\nof the ovarian graft ) and on reducing the risk of re-\nimplanting malignant cells which might be present\nin the ovarian graft (Sect. Reducing the risk of re-im-\nplanting malignant cells ). This risk could possibly\nbe reduced by two different methods: a system of\nin vitro growth (IVG) for primordial follicles (Sect. In\nvitro growth and maturation of primordial follicles )\nand the transplantation of an artificial ovary contain-\ning isolated follicles which are embedded in a ma-\ntrix (Sect. Artificial ovary ). In addition, stem cells\n(Sect. Stem cells) and allografting and xenotransplan-\ntation of ovarian tissue (Sect. Allografting and xeno-\ntransplantation) might offer completely new options.\nBenign diseases which require cytotoxic therapy, ge-\nnetic predispositions leading to a diminished ovarian\nreserve or trans*persons before hormone therapy rep-\nresent further indications for procedures of fertility\npreservation which will be more and more asked\nfor (Sect. Further indications for fertility preservation ).\nFuture enhancements are to be expected in methods\noffered to prepuberal girls.\nGonadoprotective agents\nThe mechanism of potential gonadoprotective agents\nis based on the theory that follicle loss induced by\nchemotherapy is caused by apoptosis of large follicles\nand, simultaneously, by activation of dormant folli-\ncle growth. Therefore, the focus of current research\nis on agents with anti-apoptotic characteristics or be-\ning able to prevent follicle activation: sphingosine-\n1-phosphate (S1P) was found to block apoptosis in-\nduced by certain cytotoxic drugs and to protect folli-\ncles against radiation in animal studies via inhibition\nof the ceramide-promoted pathway [ 1–3]. However,\n416 Future perspectives of fertility preservation in women K\n\nshort review\nthis agent can currently not be administered systemi-\ncally due to its short half-life, which limits its use [ 4].\nImatinib is a c-Abl tyrosine kinase inhibitor which\nwas found to protect ovarian follicles in mice when\nco-administered with cisplatin [ 5].\nT amoxifen, a selective estrogen receptor modulator\nis well known in the field of treating estrogen-sensi-\ntive cancers like breast cancer. After co-administra-\ntion with doxorubicin and cyclophosphamide in rats,\ntamoxifen was found to reduce follicle loss and oocyte\nfragmentation [ 6]. It also had an effect on radiother-\napy-induced follicular loss in rats by acting via stabi-\nlizing the anti- Mullerian hormone (AMH) level, in-\ncreasing insulin-like growth factor (IGF-1) and coun-\nteracting oxidative stress mediating apoptosis [ 7].\nThe immune modulator AS101 prevents follicle\nactivation by inhibiting the PI3K/PTEN/Akt signaling\npathway and thereby prevents the “burnout” effect\nof chemotherapy . AS101 has been co-administered\nwith cyclophosphamide in mice: primordial folli-\ncle activation was inhibited and follicle reserve was\npreserved. Interestingly, the efficacy of cyclophos-\nphamide on breast cancer cells was increased [ 8].\nMelatonin, ghrelin and mTOR inhibitors have also\nbeen found to inhibit accele rated activation of pri-\nmordial follicles in co-adm inistration with cisplatin\n[9]. T wo different pharmacologic approaches to in-\nhibit the mTOR pathway—everolimus (RAD001) and\nrapamycin—have been shown to preserve the ovarian\nreserve. These promising results with the established\ndrug everolimus were obtained in mice treated with\ncisplatin in which the PI3K/PTEN/Akt pathway was\ninvolved [9].\nIncreasing follicular survival after implantation of\nthe ovarian graft\nCryopreservation of ovarian tissue and later trans-\nplantation to the ovary has become a promising\ntechnique with over 130 live births worldwide [ 10].\nNevertheless, after transpla ntation extensive follicu-\nlar loss has been observed. It is hypothesized that\nslow graft revascularization leads to ischemia which\ncauses follicular loss [ 11]. Therefore, several novel\ntechniques are being explored to increase vascular-\nization with angiogenic a nd antiapoptotic agents.\nThe following substances have been administered\nto the frozen–thawed ovarian tissue with promis-\ning results: a combination of melatonin, vitamin E,\nhyaluronan, and vascular endothelial growth factor A\n(VEGF-A) increased neovascularization and reduced\napoptosis [ 11]. Furthermore, experimental designs\nwith erythropoietin, VEGF 111, fibroblast growth fac-\ntor, simvastatin, and a subcutaneous pump with S1P\nhave shown promising results in decreasing follicular\napoptosis [ 4]. T wo pregnancies and one live birth\nhave been reported after transplantation of ovarian\ntissue with a decellularized e xtracellular matrix (ECM)\nwhich led to the survival of primordial follicles [ 12].\nReducing the risk of re-implanting malignant\ncells\nIn vitro growth and maturation of primordial follicles\nTransplantation of frozen–thawed ovarian tissue con-\ntains the risk of re-seeding malignant cells into the\npatient. In vitro growth (IVG) of follicles and in vitro\nmaturation (IVM) of oocytes minimizes this risk. The\naim of IVG is to accomplish the entire follicular growth\nin vitro, ending with oocytes which can be fertilized.\nT o date, follicular IVG has led to live births in mice\nonly [ 13, 14]. Several culture systems have been de-\nveloped for ovarian tissue and follicles [ 13, 15–18].\nAs different follicular stages require different culture\nenvironments, the development of a well-functioning\nculture system remains challenging. Furthermore, the\nmorphology of the follicles an d critical cell–cell inter-\nactions need to be maintained [ 19]. The ideal matrix\nfor the growth of primordial follicles is still unknown.\nAlthough different growth factors have been added to\nthe culture systems, the development of follicles often\nstopped at early second ary follicle stage [ 4].\nA two-step culture system was established by T elfer\net al. [ 17]. This system first initiates the growth of\nprimordial follicles and afterwards cultures secondary\nfollicles which have been isolated in an individual cul-\nture, allowing growth until the preantral/early antral\nstage. The same research group recently presented\nthe growth of human metaphase II oocytes in a multi-\nstep culture system [ 20]. Other promising results were\nbased on implementing a three-dimensional alginate\nhydrogel matrix which allowed the follicles to main-\ntain their physiologic structure. Secondary follicles\nwere isolated and cultured up to 40 days, oocytes were\nisolated and in vitro maturated [ 21]. However, IVG of\nmeiotically competent human oocytes from preantral\nfollicles has not been achieved [ 21].\nFurther research has shown that follicle activation\ncan be achieved by interrupting the Hippo signaling\npathway and/or inhibiting the PI3K-PTEN-Akt signal-\ning pathway in prepuberal patients and women with\npremature ovarian insufficiency (POI) [ 22]. As PTEN\nexpression was reduced after xenografting of human\novarian tissue, it was hypothesized that primordial fol-\nlicle loss after ovarian transplantation might be due to\ndisruption of PI3K/Akt signaling [ 23]. These two sig-\nnaling pathways seem to play key roles in the activa-\ntion of primordial follicles. The PI3K-PTEN-Akt path-\nway takes part in the regulation of follicle dormancy\nby keeping high levels of the secondary messenger\nphosphatidylinositol-4,5-bisphosphate (PIP2) in re-\nlation to lower levels of phosphatidylinositol-3,4,5-\ntriphosphate (PIP3). Incubation of frozen–thawed\ntissue with substances which elevate PIP3 levels has\nled to three clinical pregnancies after implanting the\novarian graft [ 24–26].\nThe Hippo pathway is involved in cell proliferation,\napoptosis, follicular devel opment, and is essential for\nK Future perspectives of fertility preservation in women 417\n\nshort review\norgan size control [22, 27]. If the pathway is disrupted,\ncell growth and proliferation is promoted as it occurs\nduring the slicing procedure of ovarian tissue. This\nfragmentation led to the development of preantral fol-\nlicles [22] and, after administration of Akt stimulators\nto the culture system, to the growth of primordial fol-\nlicles in patients suffering from POI [ 24].\nIn conclusion, although these are promising results,\nit remains to be confirmed that the in vitro maturated\noocytes are competent to complete maturation pro-\ncesses and genomic imprinting procedures [ 19]a n d ,\nin the end, safe for clinical implications.\nArtificial ovary\nThe generation of a transplantable artificial ovary is\nanother alternative to the in vitro culture of follicles\nin order to obtain mature oocyte and to minimize\nthe risk of re-seeding malignant cells. For this tech-\nnique, primordial follicles need to be isolated and\ntransferred onto a three-dimensional scaffold with al-\nginate, fibrin, gelatin, or polyethylene glycol [ 28–32].\nPreantral follicles were embedded in an alginate beads\nand grafted to immunocompetent mice. It could be\nshown that antral follicles were capable of growing in\nthis matrix [ 31]. The artificial ovary requires stroma\ncells which might still bear the risk of containing can-\ncer cells: fresh human medullary cells turned out to\nbe an efficient source [ 33].\nStem cells\nThe use of embryonic stem cells or induced pluripo-\ntent stem cells might be another source of gametes\nbut it is still questionable whether these cells would\nbe able to cope with complex mechanisms involved\nin genomic imprinting and epigenetic procedures [ 10,\n34, 35].\nAllografting and xenotransplantation\nTransplantation of ovarian tissue between two differ-\nent individuals—under caut ion of compatibility also\napplying to transplantation of other organs—could be\nanother potential option to regain ovarian function\nand possibly natural conception. This procedure has\nbeen performed between two sisters and led to the\nfirst published live birth afte r allografting ovarian tis-\nsue [36]. Another option to minimize the risk of trans-\nplanting malignant cells wo uld be the xenotransplan-\ntation of cryopreserved tissue into another species in\norder to maturate oocytes and to transfer them to pa-\ntients after fertilization [ 37].\nFurther indications for fert ility preservation\nAutoimmune diseases which might require cytotoxic\ntherapy like systemic lupus erythematosus are fur-\nther indications for fertility preservation procedures.\nFurthermore, genetic predispositions like Turner syn-\ndrome can lead to premature ovarian failure. In\nthese women procedures could be offered before the\novarian reserve is diminished. Due to the rapid ad-\nvancements in improving tec hniques, it is assumable\nthat more options will soon be available for prepu-\nberal girls. Before surgery including the resection of\novarian tissue in patients w ith endometriosis, women\nc o u l db ec o u n s e l l e da b o u tf ertility preservation tech-\nniques. In addition, the demand for cryopreservation\nof oocytes or ovarian tissue by trans*persons before\nthe start of hormone therapy is increasing.\nT ake home message\n/CIRCLEGonadoprotective agents aim to prevent the\nchemotherapy-induced loss of follicles mainly by\nanti-apoptotic characteristics or prevention of folli-\ncle activation.\n/CIRCLEIncreasing follicular survival after implantation of\nthe frozen–thawed ovarian tissue can possibly be\nachieved by co-administration of different sub-\nstances like VEGF , S1P or with an extracellular ma-\ntrix.\n/CIRCLEThe risk of re-seeding malignant cells after frozen–\nthawed ovarian tissue transplantation might be min-\nimized by in vitro growth and maturation of primor-\ndial follicles and oocytes or generation of an artificial\novary.\n/CIRCLEHowever, it remains to be confirmed that in vitro mat-\nurated oocytes are competent to complete matura-\ntion processes and genomic imprinting procedures\nand safe for clinical implications.\nFunding Open access funding provided by University of Inns-\nbruck and Medical University of Innsbruck.\nConflict of interest B. Böttcher and K. Winkler-Crepaz declare\nthat they have no competing interests.\nOpen Access This article is licensed under a Creative Com-\nmons Attribution 4.0 International License, which permits\nuse, sharing, adaptation, distribution and reproduction in\nany medium or format, as long as you give appropriate credit\nto the original author(s) and the source, provide a link to\nthe Creative Commons licence, and indicate if changes were\nmade. The images or other third party material in this article\nare included in the article’ s Creative Commons licence, unless\nindicated otherwise in a credit line to the material. If material\nis not included in the article’ s Creative Commons licence and\nyour intended use is not permitted by statutory regulation or\nexceeds the permitted use, you will need to obtain permis-\nsion directly from the copyright holder. T o view a copy of this\nlicence, visit http://creativecommons.org/licenses/by/4.0/.\nReferences\n1. 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Fertility preservation for patients\nwith malignant disease. Guideline of the DGGG, DGU and\nDGRM (S2k-level, AWMF registry no. 015/082, November\n2017)—recommendations and statements for girls and\nwomen. Geburtshilfe Frauenheilkd. 2018;78:567–84.\nPublisher’s Note Springer Nature remains neutral with regard\nto jurisdictional claims in published maps and institutional\naffiliations.\n7 For latest news from interna-\ntional oncology congresses see: \nhttp://www.springermedizin.at/\nmemo-inoncology\n420 Future perspectives of fertility preservation in women K","source_license":"CC0","license_restricted":false}