Dynamic reciprocity refers to the continuous bidirectional interaction between cells and their ECM-dominated microenvironment. Remodelling of the ECM exerts mechanical forces on cells and modifies biochemical mediators near the cell membrane, thereby initiating intracellular signalling cascades that are transmitted to the nucleus via the cell membrane and cytoskeleton, leading to changes in gene transcription and chromatin conformation (22,23). The main components of the ovarian ECM include collagen, elastin, fibronectin and laminin (24), which maintain the homeostasis and mechanical properties of ovarian tissue and provide physical support for follicular development (25).

Studies have shown that both the Hippo and phosphatidylinositol 3-kinase/protein kinase B (AKT)/mammalian target of rapamycin pathways are involved in the activation of primordial follicles in humans and mice, induced by mechanical forces on the ovarian ECM (26). During follicular development, when the angle of collagen fibres is <50˚, the ECM induces directional remodelling that ensures a higher degree of contact between fibres and maintains the stability of the ovarian topological structure (27). Before ovulation, the surge of luteinizing hormone (LH) stimulates antral follicles to degrade the connective tissue of the apical follicle via upregulating matrix metalloproteinases, leading to follicular rupture (28). During corpus luteum formation, type IV collagen is replaced by type I collagen, which also depends on precise periodic remodelling of the ECM (29).

In addition to supporting folliculogenesis, the ECM plays a notable role in ovarian reproductive dysfunction diseases. In polycystic ovary syndrome (PCOS), excessive deposition of ECM components and dense collagenisation aggravate ovarian tissue fibrosis, resulting in impaired follicular development, follicular atresia and ovulatory dysfunction (30). With ovarian aging, the levels of collagen, laminin and proteoglycans markedly, whereas the levels of elastin and fibronectin decrease (31). Coupled with the progressive accumulation of advanced glycation end products, the loss of ECM enzymatic hydrolysis required for tissue homeostasis (32) disrupts the assembly process of primordial follicles in patients with premature ovarian insufficiency (POI).

Acylation modifications can serve as sensors for mechanical stimulation. When the mechanotransduction signalling pathway is activated or inhibited, the acylation status of downstream target proteins changes correspondingly, thereby forming a regulatory feedback loop (33). Furthermore, mechanical stress treatment can globally elevate chromatin accessibility in mouse cumulus cells (CCs), which is accompanied by a markedly enhanced reprogramming efficiency of somatic cell nuclear transfer. This demonstrates that mechanotransduction can directly regulate the epigenetic state independent of metabolic changes and promote cell fate conversion (34).

The main immune cells in the ovary include macrophages, T lymphocytes and B lymphocytes, among which macrophages are the most prominent type. Immune cytokines are mainly composed of tumour necrosis factor (TNF)-α, interleukin (IL)-1, IL-6, IL-8 and transforming growth factor (TGF)-β (20). Macrophages play a marked role in ovarian physiological events such as follicular growth and development, ovulation, corpus luteum formation and regression (35,36) Most related studies focus on the polarisation and dynamic transition of pro-inflammatory M1-type macrophages and tissue-remodelling M2-type macrophages (37-39).

Macrophages reside in the entire hypothalamic-pituitary-gonadal axis and play a notable role in hormonal output processes (such as ovulation, testosterone production, insulin resistance and adipokine release) and endocrine homeostasis (40). PCOS is characterised by systemic, chronic, low-grade inflammation and the ovarian tissue of patients with PCOS often show increased macrophage levels (41). A previous study showed that ovarian macrophages promote GC apoptosis and soluble CD163 secretion by upregulating the expression of the inflammatory marker CD163, which may be associated with the pathogenesis of PCOS (42). Through single-cell RNA sequencing of human ovaries, Zhou et al (43) identified four ovarian macrophage subtypes, namely C1QC+ tissue-resident macrophages (TRMs), HLA-DQA1+ TRMs, SPP1+ TRMs and VCAN+ monocyte-derived macrophages (MDMs). Functionally, the TRM subsets were mainly associated with immune regulation, tissue homeostasis and apoptotic cell elimination, whereas VCAN+ MDMs exhibited prominent inflammatory and pyroptosis-related features, thereby contributing to a pro-inflammatory microenvironment and exacerbating ovarian aging.

To date, there remains a research gap regarding how acylation modifications regulate the ovarian immune system through mechanisms involving metabolic reprogramming and protein relocalization, which could represent a promising direction for future investigation.

The ovarian vascular network is primarily composed of blood vessels and lymphatic vessels. Blood vessels provide oxygenation, transport hormonal nutrients, enable immune surveillance and clear waste products, whereas lymphatic vessels return extravascular fluid and proteins to the bloodstream and participate in immune cell transport (20). Small arteries extending to the cortical region activate the recruitment of dormant primordial follicles by increasing blood supply (44). When follicles reach the preantral stage, follicle-stimulating hormone (FSH) stimulates the surrounding theca cells to produce and release pro-angiogenic factors, leading to the formation of two concentric vascular networks (inner and outer) in the thecal sheath layer around the follicles (45). This active angiogenesis persists and reaches its peak in the mid-luteal phase (46).

Vascular endothelial growth factor (VEGF), particularly the proangiogenic isoforms VEGF120a and VEGF164a, together with VEGFR1, VEGFR2 and the soluble receptor sVEGFR2, contributes to the regulation of ovarian angiogenesis and thereby influences ovarian blood flow status during follicular development (47). Notably, VEGF exhibits opposite expression trends in PCOS and POI; VEGF levels are increased in the follicular fluid of patients with PCOS (48) but are decreased in the ovarian GCs of patients with POI (49). This suggests that VEGF may serve as a biomarker for predicting ovarian reserve function. Furthermore, VEGF polymorphisms may interfere with angiogenesis during embryo implantation, resulting in recurrent implantation failure (RIF) (50).

Histone deacetylase 6 (HDAC6) is notably expressed in most dormant primordial follicles. Its overexpression delays the activation rate of primordial follicles, thereby extending the reproductive lifespan of mice (54). Zhang et al (55) found that HDAC6 can directly act on the nerve growth factor (NGF) protein, downregulate the acetylation modification of NGF and accelerate its ubiquitin-mediated degradation. Low NGF expression levels maintain the metabolic quiescence of primordial follicles; conversely, reduced HDAC6 expression increases NGF expression, promoting the growth and development of primordial follicles, which provides clinical guidance for fertility preservation. In addition to HDAC6, forkhead box O3A (FOXO3A), a transcriptional regulator, can inhibit the excessive activation of primordial follicles by inducing cell cycle arrest when localised in the nucleus (56). The nuclear export of FOXO3A plays a marked role in POI pathogenesis (57); studies have shown that silent information regulator 1 (an NAD⁺-dependent histone deacetylase)-mediated deacetylation of FOXO3A enhances its nuclear expression, maintains its nuclear localisation, inhibits excessive activation of primordial follicles and anti-apoptosis, and thus protects ovarian reserve in mice (58). Mitochondrial alanyl-tRNA synthetase 2 (AARS2) is one of the key genes governing ovarian aging (59). By altering the mitochondrial targeting sequence, AARS2 mediates the hyperlactylation of carnitine palmitoyltransferase 2, a mitochondrial-associated protein, thereby inhibiting its enzymatic activity, leads to free fatty acid accumulation and the activation of peroxisome proliferator-activated receptor γ; this releases a large amount of lactic acid signals into the ovarian microenvironment, triggering FSH to initiate primordial follicle development and accelerating follicle exhaustion. Targeted inhibition of AARS2 can alleviate POI occurrence in mice (60).

The quiescence mechanism that protects the follicle pool is a double-edged sword; excessive metabolic quiescence inhibits the necessary cellular self-renewal, leading to DNA damage, organelle aging and errors in epigenetic marks. Oocyte aging is accompanied by an increase in reactive oxygen species (ROS) (21). Spindle assembly is a key step in oocyte maturation, and a well-formed spindle is an indicator for evaluating oocyte quality (61). During meiosis of aged oocytes, ROS-induced palmitoyl-protein thioesterase 1 (PPT1) localises to the spindle, and its overexpression causes tubulin depalmitoylation and spindle defects, resulting in decreased oocyte quality. However, melatonin rescues PPT-induced low palmitoylation state of aged oocytes (62).

Metabolic state transition accompanying follicle activation. Compared with young women with normal ovarian function, the expression levels of mitochondrial deacetylase SIRT3 and its target protein glutamate dehydrogenase (GDH) are decreased in GCs and CCs of women with diminished ovarian reserve or advanced age. The resulting hyperacetylation of GDH may reduce its enzymatic activity in granulosa and cumulus cells, thereby disturbing mitochondrial amino acid metabolism and compromising the metabolic support these follicular cells provide to the oocyte, which may contribute to an unfavorable follicular microenvironment (63). Follicular development relies on the dynamic proliferation of GCs; Zhou et al (64) proposed that the acetylation of lysine 27 on histone H3 (H3K27ac) induces the upregulation of growth differentiation factor-8, which in turn accelerates cell cycle transition from the G1 phase to the S phase through the activin-like kinase 5-extracellular signal-regulated kinase signalling pathway, thereby promoting GC proliferation. Another study found that when AGO2 formed a complex with the FOXO3 promoter, nuclear-enriched miR-195-5p upregulated FOXO3 expression in granulosa cells, likely through promoter-associated histone acetylation and demethylation, thereby influencing follicular development and atresia (65). Beyond the maintenance of nuclear localization, nucleocytoplasmic shuttling also serves a notable function in coupling metabolic status with follicular development. Lactylation of the transcription factor cAMP response element-binding protein (CREB) at residue K136 facilitates CREB phosphorylation, the assembly of the transcription complex and its translocation into the cytoplasm, thereby directly activating the transcription of genes implicated in granulosa cell proliferation and differentiation (66). This demonstrates that lactylation drives the subcellular relocation of key factors, transducing metabolic signals into transcriptional regulation to directly modulate granulosa cell function, thereby contributing to the remodelling of the ovarian microenvironment.

In patients with PCOS, metabolic pathways such as glycolysis, fatty acid β-oxidation, branched-chain amino acid catabolism and the tricarboxylic acid cycle are upregulated, whereas lactate dehydrogenase (LDH) activity is decreased in follicular fluid and serum. Abnormal levels of these intermediate metabolites exacerbate SIRT protein family dysfunction, leading to reduced downstream deacetylation activity. This further leads to mitochondrial dysfunction, redox imbalance and increased oxidative stress, which may disturb local intermediary metabolism, impair the metabolic and antioxidant support provided by cumulus and granulosa cells to the oocyte, and promote an inflammatory and metabolically unfavorable follicular microenvironment, thereby compromising follicle and oocyte development and reinforcing a vicious cycle (67-69). In addition to abnormalities in energy and oxidative metabolism, hyperandrogenism in PCOS alters CK2α nuclear translocation in granulosa cells, which is associated with increased HDAC2 phosphorylation, reduced H3K27ac and decreased expression of cell proliferation-related genes such as CCND1, CCND3 and PCNA, thereby disrupting normal follicular development (70). The desuccinylase SIRT5 is notably expressed in PCOS (71); silencing SIRT5 promotes GCs proliferation and inhibits their apoptosis by increasing the succinylation of GLI family zinc finger 1 protein at the lysine 232 site, suggesting that SIRT5 may be a new target for PCOS treatment (72). In premature ovarian failure (POF), ac4C modification of P16 mRNA is increased in ovarian granulosa cells. Electroacupuncture reduces ac4C modification of P16 mRNA, downregulates P16 and NAT10, upregulates CDK6 and CCND1, increases ovarian weight and peripheral estrogen levels, and decreases the proportion of atretic follicles in POF mice, thereby improving the follicular microenvironment associated with ovarian dysfunction (73).

Metabolic coupling between oocytes and somatic cells. During the window of follicular development, inhibition of histone deacetylases leads to increased levels of specific histone epigenetic marks. Specifically, this is characterised by increased levels of histone H3 lysine 9 acetylation (H3K9ac), H4ac and trimethylation of lysine at position 4 of histone H3 (H3K4me3), along with decreased H3K9me3 (74,75). This may result in inefficient and erroneous DNA repair, disrupting the transition from somatic cells to germline. Consequently, the number of primordial, primary and secondary follicles decreases, ultimately leading to the atrophy of ovarian oocyte reserve (76). The nuclear translocation of CK2α induced by the ovulatory signal LH or human chorionic gonadotropin (hCG) enhances HDAC2 activity. HDAC2 is preferentially localised in CCs and mural GCs adjacent to follicular fluid. Through the deacetylation of a series of non-histone proteins such as signal transducer and activator of transcription 3 and SMAD family member 7, it promotes the transcription of ovulation-related genes and the expansion of cumulus-oocyte complexes, thereby triggering ovulation (77). A recent study found that the overall protein acetylation level in the ovarian tissue of mice induced by a high-fat diet was markedly reduced (78). This negatively regulates the downstream phosphatase and tensin homolog/AKT/FOXO3 signalling pathway, downregulates the expression of growth differentiation factor-9 and bone morphogenetic protein-15 and disrupts the normal operation of the oocyte-GC regulatory loop in the microenvironment.

Over the past decade, research on oocyte derivation has markedly advanced. Granulosa cells (GCs) can be reprogrammed into induced pluripotent stem cells (iPSCs) using only two transcription factors, Oct4 and Sox2, and this strategy has also contributed to advances in animal cloning research (79,80). GCs isolated from the ovaries of adult mice can be robustly induced to generate germline-competent PSCs (gPSCs) using purely chemical methods (81). These gPSCs can continuously and directionally differentiate into primordial germ cell-like cells, which further develop into functional oocytes. Thus, gPSCs modified by crotonylation and their derived germ cells exhibit longer telomeres and higher genomic stability, providing sufficient evidence for the safety and efficacy of chemical induction (81).

Presetting metabolite preparation for embryonic development. The accumulation of metabolites for embryonic development starts around the time of ovulation, continues through corpus luteum formation and concludes at the maternal-foetal interface. During the process of hCG-induced ovulation and corpus luteum formation, the hypoxic environment that is generated can stimulate lactate production. The accumulation of lactate leads to the lactylation of H3K18, which upregulates the transcription of cytochrome P450 family 11 subfamily A member 1 and steroidogenic acute regulator, thereby promoting the expression of luteinization markers in GCs (82). Liu et al (83) found that a maternal high-fat diet during pregnancy in mice causes mitochondrial dysfunction in the germ cells of offspring. However, vitamin B1 supplementation converts pyruvate into acetyl-CoA, which upregulates histone acetylation in the nuclei of GCs from newborn mice, increases the chromatin accessibility of promoters of cell cycle-related genes and enhances mitochondrial function in the GCs of the offspring. Maternal intrauterine exposure to high glucocorticoid levels forces the glucocorticoid receptor to translocate into the nucleus and upregulates the expression of HDAC10. This, in turn, reduces the H3K27ac level of insulin-like growth factor 1 and decreases oestradiol synthesis. This could potentially be the intrauterine origin mechanism underlying ovarian dysfunction and multi-organ developmental abnormalities in some offspring (84) (Fig. 1).

The stiffness of the ECM restricts follicle expansion and oocyte maturation, keeping primordial follicles in a quiescent state. When growing follicles migrate to the ovarian medulla, they encounter a softer ECM, which expands their developmental space (85). Through transcriptome data analysis of GCs, Li et al (86) identified a cytoplasmically expressed trans-regulatory long non-coding RNA in actin gamma 1 (ACTG1) (TRLA). Mediated by H3K4ac, TRLA interacts with ACTG1 mRNA; it participates in follicular development by regulating GCs migration, increases oestrogen and progesterone secretion and promotes sexual maturation. In PCOS, the TGF-β/Smad signalling pathway upregulates the expression of the acetylation reader bromodomain-containing protein 4 (BRD4). BRD4 binds to histone 3/4 promoters to activate the androgen receptor, accelerating ovarian fibrosis; therefore, targeted inhibition of BRD4 is a promising intervention strategy (87).

Blood vessels. In the ovaries of mice with PCOS, the expression of histone deacetylase 5 (HDAC5) is compensatorily increased, accompanied by a state of high oxidative stress. HDAC5 overexpression downregulates the acetylation of VEGF receptor 2 (VEGFR2), inhibits the activation of the hypoxia-inducible factor-1α/VEGF factor A/VEGFR2 signalling pathway, reduces ovarian angiogenesis, improves abnormalities in ovarian morphology and serum hormone levels, decreases the level of ROS and increases the activities of catalase and superoxide dismutase. These findings reveal that HDAC5 exerts a protective role in PCOS by inhibiting ovarian angiogenesis, providing a candidate molecule for PCOS treatment (88).

Hormones. The S-palmitoylation modification of heat shock protein-90α mediated by zinc finger DHHC-type palmitoyltransferase 17 (ZDHHC17) generally upregulates the expression of CYP19A1. However, in the hyperandrogenic environment of PCOS, ZDHHC17 is downregulated, leading to impaired conversion of androgens to oestrogens and a vicious cycle of hyperandrogenism (89). The development of ZDHHC17-specific agonists may be beneficial for treating PCOS in the future (Table I).

In conclusion, in the regulation of the ovarian microenvironment, it is most accurate to summarize the relationship between acylation modification and metabolic reprogramming as a strong synergistic association with intertwined causality. First, Metabolic reprogramming alters the abundance and ratio of key metabolites such as acyl-CoA and succinyl-CoA, which serve as essential substrates or cofactors for acylation modifications (such as acetylation and succinylation) of proteins. In turn, acylation modification, acting as a rapid molecular switch, can directly regulate the activity, localization and stability of metabolic enzymes, thereby guiding metabolic pathways. Second, both acylation modification and metabolic reprogramming can be coordinated by upstream endocrine signals. In ovarian granulosa cells, FSH signaling can reshape histone H3 phosphorylation and acetylation, whereas metabolic reprogramming alters the availability of acyl-CoA metabolites that serve as donors for protein acylation. Conversely, acylation modification can regulate the activity, localization and stability of metabolic enzymes, thereby forming a bidirectional feedback loop between metabolism and acylation status (90-92). Furthermore, in diseases such as PCOS and POI/POF, abnormalities in acylation modification are frequently accompanied by metabolic disorders, including mitochondrial dysfunction and imbalances in glucose and lipid metabolism (73,93,94). These abnormalities jointly disrupt the ovarian microenvironment and represent different expressive levels of the same pathophysiological process.

The present review provides a conceptual framework for developing strategies to improve ovarian function and follicle quality, prevent adverse developmental outcomes in offspring and guide interventions for reproductive dysfunction-related diseases. Paired homeodomain transcription factor-2 (PITX2) is one of the key factors promoting tumourigenesis and progression. A study showed that in ovarian cancer cells overexpressing PITX2, LDH-A is transiently localised in the nucleus and produces high concentrations of lactate (95). The accumulation of intranuclear lactate leads to decreased expression of HDAC1/2 and increased H3/H4ac, accelerating cancer cell proliferation. This suggests that targeting PITX2 or inducing the nuclear export of LDHA may be potential anti-cancer approaches. In drug-resistant ovarian cancer, under a lactate-accumulating microenvironment, Lu et al (96) found that niraparib resistance may involve the upregulation of H4K12 lactylation, which mediates the abnormal expression of RAD23 homolog A (RAD23A) via super-enhancers. This enhances the DNA damage repair capacity of ovarian cancer cells, indicating that RAD23A can serve as a potential therapeutic target.

Thus, targeting core proteins (such as transcription factors, signalling molecules and acylation-modifying enzymes) in the ovarian microenvironment or directionally inducing their re-localisation by intervening in any metabolic reprogramming pathway may represent an effective clinical therapeutic strategy in the future.