Dysregulated post‑translational modifications in granulosa cells drive ovarian dysfunction and potential infertility applications (Review).

GCs are the specialized somatic cells of the sex cord-stromal lineage found within the mammalian ovarian follicle, where they typically form either a monolayer or a multilayer around the oocyte to facilitate follicular development and steroid hormone synthesis ( 1 ). During follicular development, GCs differentiate into two functionally distinct subpopulations: Mural GCs, which align with the basal lamina to constitute the follicular wall, and cumulus cells, which maintain communication with the central oocyte ( 2 ). These cells also establish gap junction-mediated communication with the oocyte, providing essential nutrient support and regulating the microenvironment necessary for oocyte maturation ( 3 , 4 ). The proper proliferation and differentiation of GCs are imperative for the correct formation of follicles and the subsequent quality of the embryo, both of which are key determinants of female fertility ( 5 ). Infertility has increasingly been acknowledged as a considerable global public health issue. Female factors contribute to >50% of infertility cases, predominantly driven by environmental degradation and adverse lifestyle conditions ( 6 ). Dysfunctions in GCs include a range of pathophysiological processes, such as imbalances in proliferation and differentiation, abnormalities in cellular senescence and apoptosis, and disturbances in hormone synthesis ( 7 , 8 ). The mechanisms contributing to these dysfunctions are complexly associated with excessive oxidative stress, mitochondrial dysfunction, abnormal inflammatory responses and endoplasmic reticulum stress (ERS) ( 8 - 11 ). Such dysfunctions can markedly compromise female fertility through various molecular pathways, including the premature depletion of the primordial follicle pool ( 12 ), disrupted folliculogenesis ( 13 ), ovulation disorders ( 14 ) and embryo implantation failures ( 15 ). Given the pivotal role of GCs in folliculogenesis, a comprehensive understanding of their regulatory mechanisms is indispensable. Acquiring this knowledge is key for identifying potential biomarkers for the early diagnosis of infertility and could lay the groundwork for the development of GC-targeted therapeutic strategies, thereby advancing precision medicine in the management of clinical infertility. PTMs of proteins refer to the process of adding or removing chemical groups from amino acid residues in the polypeptide chains of proteins. These modifications, defined as the side chain modification of amino acids that occur after protein synthesis ( 16 , 17 ), provide a powerful means to augment and regulate protein function. PTMs are essential cellular mechanisms that regulate protein activity, stability and subcellular localization through reversible covalent modifications. As fundamental regulatory mechanisms, PTMs carry out a pivotal role in orchestrating diverse biological processes ( 18 ). Within GCs, PTMs meticulously regulate cellular proliferation, differentiation, apoptosis and hormone secretion by modulating signaling pathways, epigenetic landscapes, proteostasis and metabolic modifications ( 7 , 19 , 20 ). Canonical PTMs, including phosphorylation, methylation, ubiquitination and acetylation, are important in regulating the functions of GCs. For example, PTM-mediated activation of the PI3K/AKT/FOXO3 signaling pathway is essential for primordial follicle activation, underscoring the fundamental role of PTMs in folliculogenesis ( 21 ). Additionally, dynamic histone modifications, particularly H3K4me3, H3K9me and H3K27me3, act as epigenetic switches that precisely regulate progesterone production during luteinization ( 20 ). Advancements in high-resolution mass spectrometry have revealed several novel PTMs including lactylation ( 22 ), crotonylation ( 23 ), neddylation ( 24 ), lysine succinylation ( 25 ) and lysine β-hydroxybutyrylation ( 26 ), which notably influence GC. Accumulating evidence suggests that aberrant PTM patterns in GCs are a principal factor contributing to infertility. Thus, elucidating the PTM profiles in GCs not only enhances the understanding of the pathogenesis of infertility but also aids in the development of therapeutic strategies targeting specific PTM enzymes. Assisted reproductive technology (ART) serves as an important intervention for fertility preservation. Dysfunctional GCs impair oocyte quality, maturation and embryo viability, thereby reducing the success rates of ART ( 5 , 27 , 28 ). Almeida et al ( 5 ) suggested that a pre-ART evaluation of GC quality could enhance the selection of oocytes and embryos. Notably, ovarian hyperstimulation syndrome (OHSS), a severe complication of ovarian stimulation during ART, may benefit from therapeutic approaches involving PTMs in the future. Zheng et al ( 29 ) demonstrated that melatonin mitigates reactive oxygen species (ROS)-induced apoptosis in GCs via the phosphorylation regulation of the SESN2-AMPK-mTOR axis, suggesting considerable clinical potential for OHSS therapy. Furthermore, a clinical study on polycystic ovary syndrome (PCOS) indicated that Myo-Inositol supplementation improves steroidogenesis, oocyte maturation, fertilization rates and embryo quality through phosphorylation-dependent modulation of the ERK1/2 and AKT pathway in cumulus cells ( 30 ). Concurrently, Zhang et al ( 31 ) confirmed that electro-acupuncture improves ovarian function in a premature ovarian failure (POF) mouse model through phosphorylation-mediated regulation of the PI3K/AKT/mTOR signaling cascade. Collectively, these studies underscore that PTM-targeted interventions in GCs represent a promising therapeutic approach for treating female infertility. However, current reviews on PTMs in female infertility focus on physiological processes such as folliculogenesis ( 32 ), oocyte meiotic maturation and embryonic development ( 33 , 34 ) or are restricted to one specific pathological context, such as POF ( 35 ), unexplained recurrent pregnancy loss ( 36 ), recurrent spontaneous abortion ( 37 ), PCOS ( 38 , 39 ) and endometriosis ( 40 ). Although PTMs have been confirmed to be involved in GCs, the majority of studies are fragmented, focusing largely on a single class of modifications, without integrating how different PTM pathways interact ( 41 - 43 ). Comprehensive elucidation of the dynamic interplay between the full spectrum of PTMs and GC physiology remains limited. From the perspective of GCs, the present review integrates studies on how various PTMs regulate diverse vital activities of GCs, including proliferation, differentiation, apoptosis and steroid hormone secretion, evaluates their potential for therapeutic targeting and ultimately aims to establish a novel framework for understanding the regulatory networks of GCs, thereby facilitating PTM-based clinical interventions for infertility.

Infertility is increasingly recognized as a considerable global challenge affecting female reproductive health ( 166 ). As a fundamental regulatory mechanism of protein function, PTMs meticulously orchestrate protein networks within GCs and carry out a key role in reproductive pathologies. Emerging evidence suggests that PTM dysregulation in GCs is a key determinant in the pathogenesis of female infertility, offering novel mechanistic insights and therapeutic targets for clinical intervention. Notably, with the rise in global environmental pollution, exposure to toxins such as heavy metals, radiation and hazardous chemicals may disrupt physiological PTMs in GCs, leading to autophagy or apoptosis of these cells, ultimately exacerbating infertility ( 43 , 167 , 168 ). However, the molecular mechanisms underlying the interactions between environmental factors and reproductive health remain elusive, representing a notable area of scientific and clinical interest for the prevention and treatment of infertility amid increasing environmental pollution. As the primary treatment modality for infertility, the long-term safety of ART necessitates further evaluation. Current evidence suggests that offspring conceived via ART may be at increased risk for rare imprinting disorders, potentially associated with aberrant epigenetic reprogramming in gametes or embryos ( 169 ). With the widespread adoption of ART, understanding its intergenerational health impacts is imperative. Notably, dynamic PTMs in GCs during ART have been shown to markedly influence the success of clinical pregnancies ( 30 ). However, few studies have explored whether in vitro manipulations disrupt embryonic epigenetic programming via PTM dysregulation in GCs. Thus, elucidating the molecular causality in the 'ART/PTM remodeling/embryonic development' pathway is crucial for optimizing ART procedures and ensuring intergenerational health. Although targeted PTM therapy has achieved clinical success in oncology ( 170 - 173 ), its application in reproductive medicine remains in its early stages. While considerable progress has been made in mapping the PTM landscape of GCs, clinical application is constrained by several persistent challenges. Current evidence relies heavily on preclinical models, necessitating validation in large-scale human cohorts to establish pathological relevance. Additionally, the inherent dynamism and precisely timed fluctuations of PTMs across the follicular developmental continuum present a fundamental challenge for therapeutic targeting ( 87 ). Moreover, effective and ovary-specific drug delivery remains a pronounced technological barrier, requiring improved precision, kinetics and biocompatibility of delivery systems to minimize off-target effects ( 174 , 175 ). Future research should focus more on transitioning from individualized single-omics approaches to multi-omics strategies. Building a comprehensive PTM-omics database for GCs and associating it with large-scale clinical data will provide a key foundation for facilitating high-throughput drug screening ( 45 , 156 , 176 ). In conclusion, the present review systematically assessed the dynamic regulatory networks of both canonical and novel PTMs in the proliferation, differentiation, apoptosis and hormone synthesis of GCs. It elucidates the pathological mechanisms of aberrant PTMs in female infertility, and comprehensively assesses the translational medical value of targeted PTM therapy for GCs. By integrating epigenetic regulation with clinical applications, this work aims to provide novel insights into precision diagnosis and treatment strategies for female infertility.