DNA hypermethylation in hyperhomocysteinemia contributes to abnormal extracellular matrix metabolism in the kidney

Complex Pathophysiology of Acute Kidney Injury (AKI) in Aging: Epigenetic Regulation, Matrix Remodeling, and the Healing Effects of H2S

The kidney is an essential excretory organ that works as a filter of toxins and metabolic by-products of the human body and maintains osmotic pressure throughout life. The kidney undergoes several physiological, morphological, and structural changes with age. As life expectancy in humans increases, cell senescence in renal aging is a growing challenge. Identifying age-related kidney disorders and their cause is one of the contemporary public health challenges. While the structural abnormalities to the extracellular matrix (ECM) occur, in part, due to changes in MMPs, EMMPRIN, and Meprin-A, a variety of epigenetic modifiers, such as DNA methylation, histone alterations, changes in small non-coding RNA, and microRNA (miRNA) expressions are proven to play pivotal roles in renal pathology. An aged kidney is vulnerable to acute injury due to ischemia-reperfusion, toxic medications, altered matrix proteins, systemic hemodynamics, etc., non-coding RNA and miRNAs play an important role in renal homeostasis, and alterations of their expressions can be considered as a good marker for AKI. Other epigenetic changes, such as histone modifications and DNA methylation, are also evident in AKI pathophysiology. The endogenous production of gaseous molecule hydrogen sulfide (H2S) was documented in the early 1980s, but its ameliorative effects, especially on kidney injury, still need further research to understand its molecular mode of action in detail. H2S donors heal fibrotic kidney tissues, attenuate oxidative stress, apoptosis, inflammation, and GFR, and also modulate the renin-angiotensin-aldosterone system (RAAS). In this review, we discuss the complex pathophysiological interplay in AKI and its available treatments along with future perspectives. The basic role of H2S in the kidney has been summarized, and recent references and knowledge gaps are also addressed. Finally, the healing effects of H2S in AKI are described with special emphasis on epigenetic regulation and matrix remodeling.

Advances in the role of epigenetics in homocysteine-related diseases

Homocysteine has a wide range of biological effects. However, the specific molecular mechanism of its pathogenicity is still unclear. The diseases induced by hyperhomocysteinemia (HHcy) are called homocysteine-related diseases. Clinical treatment of HHcy is mainly through folic acid and B-complex vitamins, which are not effective in reducing the associated end point events. Epigenetics is the alteration of heritable genes caused by DNA methylation, histone modification, noncoding RNAs and chromatin remodeling without altering the DNA sequence. In recent years the role of epigenetics in homocysteine-associated diseases has been gradually discovered. This article summarizes the latest evidence on the role of epigenetics in HHcy, providing new directions for its prevention and treatment.

ROS promote hyper-methylation of NDRG2 promoters in a DNMTS-dependent manner: Contributes to the progression of renal fibrosis

Renal fibrosis is the common histopathological feature of chronic kidney diseases (CKD), and there is increasing evidence that epigenetic regulation is involved in the occurrence and progression of renal fibrosis. N-myc downstream-regulated gene 2 (NDRG2) is significantly down-regulated in renal fibrosis, the mechanism of which remains unclear. Previous studies have confirmed that the inhibition of NDRG2 expression in tumor cells is related to hyper-methylation, mainly regulated by DNA methyltransferases (DNMTS). Herein, we explored the expression of NDRG2 and its epigenetic regulatory mechanism in renal fibrosis. The results showed that the expression of NDRG2 was significantly inhibited in vivo and in vitro, while the overexpression of NDRG2 effectively alleviated renal fibrosis. Meanwhile, we found that the expression of DNMT1/3A/3B was significantly increased in hypoxia-induced HK2 cells and Unilateral Ureteral Obstruction (UUO) mice accompanied by hyper-methylation of the NDGR2 promoter. Methyltransferase inhibitor (5-AZA-dC) corrected the abnormal expression of DNMT1/3A/3B, reduced the methylation level of NDRG2 promoter and restored the expression of NDRG2. The upstream events that mediate changes in NDRG2 methylation were further explored. Reactive oxygen species (ROS) are important epigenetic regulators and have been shown to play a key role in renal injury due to various causes. Accordingly, we further explored whether ROS could induce DNA-epigenetic changes of the expression of NDRG2 and then participated in the development of renal fibrosis. Our results showed that mitochondria-targeted antioxidants (Mito-TEMPO) could reverse the epigenetic inhibition of NDRG2 in a DNMT-sensitive manner, showing strong ability of DNA demethylation, exhibiting epigenetic regulation and anti-fibrosis effects similar to 5-AZA-dC. More importantly, the anti-fibrotic effects of 5-AZA-dC and Mito-TEMPO were eliminated in HK2 cells with NDRG2 knockdown. These findings highlight that targeting ROS-mediated hyper-methylation of NDRG2 promoter is a potentially effective therapeutic strategy for renal fibrosis, which will provide new insights into the treatment of CKD.

5-Aza-2′-Deoxycytidine (5-Aza-dC, Decitabine) Inhibits Collagen Type I and III Expression in TGF-β1-Treated Equine Endometrial Fibroblasts

Endometrosis negatively affects endometrial function and fertility in mares, due to excessive deposition of type I (COL1) and type III (COL3) collagens. The pro-fibrotic transforming growth factor (TGF-β1) induces myofibroblast differentiation, characterized by α-smooth muscle actin (α-SMA) expression, and collagen synthesis. In humans, fibrosis has been linked to epigenetic mechanisms. To the best of our knowledge, this has not been described in mare endometrium. Therefore, this study aimed to investigate the in vitro epigenetic regulation in TGF-β1-treated mare endometrial fibroblasts and the use of 5-aza-2′-deoxycytidine (5-aza-dC), an epigenetic modifier, as a putative treatment option for endometrial fibrosis. Methods and Results: The in vitro effects of TGF-β1 and of 5-aza-dC on DNA methyltransferases (DNMT1, DNMT3A, and DNMT3B), COL1A1, COL3A1, and α-SMA transcripts were analyzed in endometrial fibroblasts, and COL1 and COL3 secretion in a co-culture medium. TGF-β1 upregulated DNMT3A transcripts and collagen secretion. In TGF-β1-treated endometrial fibroblasts, DNA methylation inhibitor 5-aza-dC decreased collagen transcripts and secretion, but not α-SMA transcripts. Conclusion: These findings suggest a possible role of epigenetic mechanisms during equine endometrial fibrogenesis. The in vitro effect of 5-aza-dC on collagen reduction in TGF-β1-treated fibroblasts highlights this epigenetic involvement. This may pave the way to different therapeutic approaches for endometrosis.

The potential impact of a probiotic: Akkermansia muciniphila in the regulation of blood pressure—the current facts and evidence

Akkermansia muciniphila (A. muciniphila) is present in the human gut microbiota from infancy and gradually increases in adulthood. The potential impact of the abundance of A. muciniphila has been studied in major cardiovascular diseases including elevated blood pressure or hypertension (HTN). HTN is a major factor in premature death worldwide, and approximately 1.28 billion adults aged 30–79 years have hypertension. A. muciniphila is being considered a next-generation probiotic and though numerous studies had highlighted the positive role of A. muciniphila in lowering/controlling the HTN, however, few studies had highlighted the negative impact of increased abundance of A. muciniphila in the management of HTN. Thus, in the review, we aimed to discuss the current facts, evidence, and controversy about the role of A. muciniphila in the pathophysiology of HTN and its potential effect on HTN management/regulation, which could be beneficial in identifying the drug target for the management of HTN.

Prevalence of hyperhomocysteinemia (HHcy) and its major determinants among hypertensive patients over 35 years of age

OBJECTIVE

Hyperhomocysteinemia (HHcy) and hypertension are associated with cardiovascular events. However, effects of Hcy-lowing interventions on cardiovascular outcome were conflicting. Serum folate level was proposed to be a possible determinant of efficacy of extra folate supplementation on cardiovascular outcome. The aims of the present study were to describe representative information on the levels of serum homocysteine and folate in hypertensive patients, and to explore the major determinants of HHcy.

METHODS

11,007 participants with hypertension were analyzed in this cross-sectional study. Blood pressure and serum levels of biochemical indicators were measured. Multivariate logistic regression model was used to assess the associated factors of HHcy.

RESULTS

Geometric mean of serum total homocysteine was 14.1 (95% CI: 13.9, 14.4) μmol/L and prevalence of HHcy was 36.1 (95% CI: 34.0, 38.1) % in hypertensive patients. HHcy was strongly associated with factors including male sex, older age, elevated serum creatinine (SCr), lower serum folate and vitamin B12, and uncontrolled blood pressure in hypertensive patients. Elevated SCr attributed to HHcy with the etiologic fraction of 0.29. The change of the odds ratio of HHcy associated with folate was significantly higher in patients with elevated SCr compared with that of patients with normal SCr.

CONCLUSION

The results suggested the protection of female sex and higher levels of folate and vitamin B12 from HHcy and attribution of older age and elevated SCr to HHcy. Restoring renal function deserved attention for hypertensive patients to benefit from Hcy-lowing measures.

Homocysteine promotes cardiac fibrosis by regulating the Akt/FoxO3 pathway

Background

Evaluated plasma homocysteine (Hcy) is an independent risk factor for cardiac fibrosis which is a common feature of cardiovascular disease, although the mechanisms are still unclear. This study aims to explore the mechanism of Hcy-induced cardiac fibrosis.

Methods

The mRNA and protein levels of Forkhead box O3 (FoxO3) and differentiation markers were detected in primary cardiac fibroblasts (CFs) after 300 µM Hcy treatment. Scratch and transwell migration assay were used to determine the effect of Hcy on proliferation and migration in CFs. The protein levels involved in the fibrotic processes in mice fed with high methionine diet (HMD) for 4 or 8 weeks were investigated by western blot. CFs were infected with FoxO3 recombinant adenovirus to explore the potential role of FoxO3 in Hcy-induced cardiac dysfunction.

Results

Hcy treatment significantly promoted the differentiation, proliferation and migration of CFs, while FoxO3 activity were decreased in CFs. In HMD hearts, the protein levels of TIMP1, Fibronectin and α-SMA were increased after 4 or 8 weeks, but the FoxO3 activity was decreased. Moreover, the HMD hearts had a higher level of Bcl2 but lower of Bax and LC3II protein. In addition, FoxO3 overexpression attenuates Hcy-induced dysfunction in CFs.

Conclusions

Hcy promotes myofibroblast activation and resistance to autophagy and apoptosis in CFs, and eventually results in cardiac fibrosis by regulating the Akt/FoxO3 pathway. Thus, FoxO3 is a promising therapeutic target to prevent cardiac remodeling.

Matrix metalloproteinases and tissue inhibitors of matrix metalloproteinases in kidney disease

Matrix metalloproteinases (MMPs) are a group of zinc and calcium endopeptidases which cleave extracellular matrix (ECM) proteins. They are also involved in the degradation of cell surface components and regulate multiple cellular processes, cell to cell interactions, cell proliferation, and cell signaling pathways. MMPs function in close interaction with the endogenous tissue inhibitors of matrix metalloproteinases (TIMPs), both of which regulate cell turnover, modulate various growth factors, and participate in the progression of tissue fibrosis and apoptosis. The multiple roles of MMPs and TIMPs are continuously elucidated in kidney development and repair, as well as in a number of kidney diseases. This chapter focuses on the current findings of the significance of MMPs and TIMPs in a wide range of kidney diseases, whether they result from kidney tissue changes, hemodynamic alterations, tubular epithelial cell apoptosis, inflammation, or fibrosis. In addition, the potential use of these endopeptidases as biomarkers of renal dysfunction and as targets for therapeutic interventions to attenuate kidney disease are also explored in this review.

IL-15 Prevents Renal Fibrosis by Inhibiting Collagen Synthesis: A New Pathway in Chronic Kidney Disease?

Chronic kidney disease (CKD), secondary to renal fibrogenesis, is a public health burden. The activation of interstitial myofibroblasts and excessive production of extracellular matrix (ECM) proteins are major events leading to end-stage kidney disease. Recently, interleukin-15 (IL-15) has been implicated in fibrosis protection in several organs, with little evidence in the kidney. Since endogenous IL-15 expression decreased in nephrectomized human allografts evolving toward fibrosis and kidneys in the unilateral ureteral obstruction (UUO) model, we explored IL-15's renoprotective role by pharmologically delivering IL-15 coupled or not with its soluble receptor IL-15Rα. Despite the lack of effects on myofibroblast accumulation, both IL-15 treatments prevented tubulointerstitial fibrosis (TIF) in UUO as characterized by reduced collagen and fibronectin deposition. Moreover, IL-15 treatments inhibited collagen and fibronectin secretion by transforming growth factor-β (TGF-β)-treated primary myofibroblast cultures, demonstrating that the antifibrotic effect of IL-15 in UUO acts, in part, through a direct inhibition of ECM synthesis by myofibroblasts. In addition, IL-15 treatments resulted in decreased expression of monocyte chemoattractant protein 1 (MCP-1) and subsequent macrophage infiltration in UUO. Taken together, our study highlights a major role of IL-15 on myofibroblasts and macrophages, two main effector cells in renal fibrosis, demonstrating that IL-15 may represent a new therapeutic option for CKD.

Epigenetics in kidney diseases

Epigenetics examines heritable changes in DNA and its associated proteins except mutations in gene sequence. Epigenetic regulation plays fundamental roles in kidney cell biology through the action of DNA methylation, chromatin modification via epigenetic regulators and non-coding RNA species. Kidney diseases, including acute kidney injury, chronic kidney disease, diabetic kidney disease and renal fibrosis are multistep processes associated with numerous molecular alterations even in individual kidney cells. Epigenetic alterations, including anomalous DNA methylation, aberrant histone alterations and changes of microRNA expression all contribute to kidney pathogenesis. These changes alter the genome-wide epigenetic signatures and disrupt essential pathways that protect renal cells from uncontrolled growth, apoptosis and development of other renal associated syndromes. Molecular changes impact cellular function within kidney cells and its microenvironment to drive and maintain disease phenotype. In this chapter, we briefly summarize epigenetic mechanisms in four kidney diseases including acute kidney injury, chronic kidney disease, diabetic kidney disease and renal fibrosis. We primarily focus on current knowledge about the genome-wide profiling of DNA methylation and histone modification, and epigenetic regulation on specific gene(s) in the pathophysiology of these diseases and the translational potential of identifying new biomarkers and treatment for prevention and therapy. Incorporating epigenomic testing into clinical research is essential to elucidate novel epigenetic biomarkers and develop precision medicine using emerging therapies.

Methylation-dependent antioxidant-redox imbalance regulates hypertensive kidney injury in aging

The prevalence of hypertension increases with age, and oxidative stress is a major contributing factor to the pathogenesis of hypertension-induced kidney damage in aging. The nicotinamide adenine dinucleotide phosphate (NADPH) family is one of the major sources of reactive oxygen species (ROS) generation, and several NADPH oxidase isoforms are highly expressed in the kidney. Although epigenetic protein modification plays a role in organ injury, the methylation of the oxidant-antioxidant defense system and their role in hypertension-induced kidney damage in aging remains underexplored. The present study investigated the role of NADPH oxidase 4, superoxide dismutases (SODs), catalase, and NOS in Ang-II induced kidney damage in aging. Wild type (WT, C57BL/6J) mice aged 12-14 and 75-78 weeks were used and treated with or without Ang-II (1000 ng/kg/min) for 4 weeks with control mice receiving saline. Aged mice with or without Ang-II exhibited higher mean BP, lower renal blood flow, and decreased renal vascular density compared to young mice. While superoxide, 4-HNE, p22^phox, Nox4, iNOS were increased in the aged kidney, the expression of eNOS, MnSOD, CuSOD, catalase, Sirt1, and -3 as well as the ratio of GSH/GSSG, and activities of SODs and catalase were decreased compared to young control mice. The changes further deteriorated with Ang-II treatment. In Ang-II treated aged mice, the expressions of DNMTs were increased and associated with increased methylation of SODs, Sirt1, and Nox4. We conclude that hypermethylation of antioxidant enzymes in the aged kidney during hypertension worsens redox imbalance leading to kidney damage.

Vitamin B Supplementation and Nutritional Intake of Methyl Donors in Patients with Chronic Kidney Disease: A Critical Review of the Impact on Epigenetic Machinery

Cardiovascular morbidity and mortality are several-fold higher in patients with advanced chronic kidney disease (CKD) and end-stage renal disease (ESRD) than in the general population. Hyperhomocysteinemia has undoubtedly a central role in such a prominent cardiovascular burden. The levels of homocysteine are regulated by methyl donors (folate, methionine, choline, betaine), and cofactors (vitamin B6, vitamin B12,). Uremia-induced hyperhomocysteinemia has as its main targets DNA methyltransferases, and this leads to an altered epigenetic control of genes regulated through methylation. In renal patients, the epigenetic landscape is strictly correlated with the uremic phenotype and dependent on dietary intake of micronutrients, inflammation, gut microbiome, inflammatory status, oxidative stress, and lifestyle habits. All these factors are key contributors in methylome maintenance and in the modulation of gene transcription through DNA hypo- or hypermethylation in CKD. This is an overview of the epigenetic changes related to DNA methylation in patients with advanced CKD and ESRD. We explored the currently available data on the molecular dysregulations resulting from altered gene expression in uremia. Special attention was paid to the efficacy of B-vitamins supplementation and dietary intake of methyl donors on homocysteine lowering and cardiovascular protection.

Homocysteine Disrupts Balance between MMP-9 and Its Tissue Inhibitor in Diabetic Retinopathy: The Role of DNA Methylation

High homocysteine is routinely observed in diabetic patients, and this non-protein amino acid is considered as an independent risk factor for diabetic retinopathy. Homocysteine biosynthesis from methionine forms S-adenosyl methionine (SAM), which is a major methyl donor critical in DNA methylation. Hyperhomocysteinemia is implicated in increased oxidative stress and activation of MMP-9, and in diabetic retinopathy, the activation of MMP-9 facilitates capillary cell apoptosis. Our aim was to investigate the mechanism by which homocysteine activates MMP-9 in diabetic retinopathy. Human retinal endothelial cells, incubated with/without 100 μM homocysteine, were analyzed for MMP-9 and its tissue inhibitor Timp1 expressions and interactions, and ROS levels. Timp1 and MMP-9 promoters were analyzed for methylated and hydroxymethylated cytosine levels (5mC and 5hmC respectively) by the DNA capture method, and DNA- methylating (Dnmt1) and hydroxymethylating enzymes (Tet2) binding by chromatin immunoprecipitation. The results were confirmed in retinal microvessels from diabetic rats receiving homocysteine. Homocysteine supplementation exacerbated hyperglycaemia-induced MMP-9 and ROS levels and decreased Timp1 and its interactions with MMP-9. Homocysteine also aggravated Dnmts and Tets activation, increased 5mC at Timp1 promoter and 5hmC at MMP-9 promoter, and suppressed Timp1 transcription and activated MMP-9 transcription. Similar results were obtained from retinal microvessels from diabetic rats receiving homocysteine. Thus, hyperhomocysteinemia in diabetes activates MMP-9 functionally by reducing Timp1-MMP-9 interactions and transcriptionally by altering DNA methylation-hydroxymethylation of its promoter. The regulation of homocysteine could prevent/slow down the development of retinopathy and prevent their vision loss in diabetic patients.

Faulty homocysteine recycling in diabetic retinopathy

Background

Although hyperglycemia is the main instigator in the development of diabetic retinopathy, elevated circulating levels of a non-protein amino acid, homocysteine, are also associated with an increased risk of retinopathy. Homocysteine is recycled back to methionine by methylenetetrahydrofolate reductase (MTHFR) and/or transsulfurated by cystathionine β-synthase (CBS) to form cysteine. CBS and other transsulfuration enzyme cystathionine-γ-lyase (CSE), through desulfuration, generates H₂S. Methionine cycle also regulates DNA methylation, an epigenetic modification associated with the gene suppression. The aim of this study was to investigate homocysteine and its metabolism in diabetic retinopathy.

Methods

Homocysteine and H₂S levels were analyzed in the retina, and CBS, CSE and MTHFR in the retinal microvasculature from human donors with established diabetic retinopathy. Mitochondrial damage was evaluated in retinal microvessels by quantifying enzymes responsible for maintaining mitochondrial dynamics (fission-fusion-mitophagy). DNA methylation status of CBS and MTHFR promoters was examined using methylated DNA immunoprecipitation technique. The direct effect of homocysteine on mitochondrial damage was confirmed in human retinal endothelial cells (HRECs) incubated with 100 μM L-homocysteine.

Results

Compared to age-matched nondiabetic control human donors, retina from donors with established diabetic retinopathy had ~ 3-fold higher homocysteine levels and ~ 50% lower H₂S levels. The enzymes important for both transsulfuration and remethylation of homocysteine including CBS, CSE and MTHFR, were 40–60% lower in the retinal microvasculature from diabetic retinopathy donors. While the mitochondrial fission protein, dynamin related protein 1, and mitophagy markers optineurin and microtubule-associated protein 1A/1B-light chain 3 (LC3), were upregulated, the fusion protein mitofusin 2 was downregulated. In the same retinal microvessel preparations from donors with diabetic retinopathy, DNA at the promoters of CBS and MTHFR were hypermethylated. Incubation of HRECs with homocysteine increased reactive oxygen species and decreased transcripts of mtDNA-encoded CYTB.

Conclusions

Compromised transsulfuration and remethylation processes play an important role in the poor removal of retinal homocysteine in diabetic patients. Thus, regulation of their homocysteine levels should ameliorate retinal mitochondrial damage, and by regulating DNA methylation status of the enzymes responsible for homocysteine transsulfuration and remethylation, should prevent excess accumulation of homocysteine.

Epigenetic Modification as a Regulatory Mechanism for Spatiotemporal Dynamics of ANO1 Expression in Salivary Glands

Anoctamin1 (ANO1), a calcium activated chloride channel, is known to play a critical role in salivary secretion. In the salivary gland, ANO1 is expressed exclusively in the acinar cells, with no expression in the ductal cells. However, the mechanisms that determine this distinctive cell type-dependent expression pattern of ANO1 remain unknown. In this study, we discovered that the cell-dependent expression of ANO1 during salivary gland organogenesis is regulated by DNA methylation of ANO1 CpG islands. ANO1 CpG islands in e12 embryonic submandibular glands (eSMG) are highly methylated, but those in e14 eSMG or adult SMG are significantly unmethylated. The differential expression pattern of ANO1 in duct and acini is defined at e14. Artificial demethylation by treatment with the demethylating agent 5-aza-2'-deoxycytidine (5-Aza-CdR), induced the expression of ANO1 in both the ductal cell line Human Submandibular Gland (HSG) and in the duct cells of adult mouse SMG. During the trans-differentiation in Matrigel of duct-origin HSG cells into acinar-like phenotype, significant demethylation of ANO1 CpG islands is observed. This may be due to the reduced expression of DNA methyltransferase (DNMT) 3a and 3b. These results suggest that the differential expression of ANO1 in salivary glands during organogenesis and differentiation is mainly regulated by epigenetic demethylation of the ANO1 gene.

Chronic mild hyperhomocysteinemia induces anxiety-like symptoms, aversive memory deficits and hippocampus atrophy in adult rats: New insights into physiopathological mechanisms

In the last decade, increased homocysteine levels have been implicated as a risk factor for neurodegenerative and psychiatric disorders. We have developed an experimental model of chronic mild hyperhomocysteinemia (HHcy) in order to observe metabolic impairments in the brain of adult rodents. Besides its known effects on brain metabolism, the present study sought to investigate whether chronic mild HHcy could induce learning/memory impairments associated with biochemical and histological damage to the hippocampus. Adult male Wistar rats received daily subcutaneous injections of homocysteine (0.03 μmol/g of body weight) twice a day, from the 30th to the 60th day of life or saline solution (Controls). After injections, anxiety-like and memory tests were performed. Following behavioral analyses, brains were sliced and hippocampal volumes assessed and homogenized for redox state assessment, antioxidant activity, mitochondrial functioning (chain respiratory enzymes and ATP levels) and DNA damage analyses. Behavioral analyses showed that chronic mild HHcy may induce anxiety-like behavior and impair long-term aversive memory (24 h) that was evaluated by inhibitory avoidance task. Mild HHcy decreased locomotor and/or exploratory activities in elevated plus maze test and caused hippocampal atrophy. Decrease in cytochrome c oxidase, DNA damage and redox state changes were also observed in hippocampus of adult rats subjected to mild HHcy. Our findings show that chronic mild HHcy alters biochemical and histological parameters in the hippocampus, leading to behavioral impairments. These findings might be considered in future studies aiming to search for alternative strategies for treating the behavioral impairments in patients with mild elevations in homocysteine levels.

Dynamic decreased expression and hypermethylation of secreted frizzled-related protein 1 and 4 over the course of pulmonary fibrosis in mice

Aberrantly activated Wnt signaling pathway and dysregulation of extracellular antagonists of Wnt signaling have been revealed in pulmonary fibrosis. In this study we evaluated the expression of secreted frizzled-related proteins (SFRPs) and their aberrant promoter methylation to investigate the involvement of epigenetic regulation in pulmonary fibrosis. The pulmonary fibrosis induced by intratracheal injection of bleomycin (BLM) into mice was adopted. The transcription and relative protein expression of SFRPs were detected at Day 7 (D7), D14, and D21. DNA methylation analysis was performed by methylation-specific polymerase chain reaction (MSP). A DNA methyltransferase (DNMT) inhibitor (5-aza-2'-deoxycytidine; 5-aza) was used for demethylation and the relative β-catenin expression levels were measured to assess overactivity of the canonical Wnt signaling pathway. The transcription and protein expression of SFRP1 significantly decreased at D14 and D21, whereas the transcription and protein expression of SFRP4 significantly decreased at D7 and stayed downregulated until D21. The significantly hypermethylated promoters of SFRP1 and SFRP4 resulted in impaired transcription and decreased expression during pulmonary fibrosis in mice. Besides, reactivation of SFRP1 and SFRP4 by 5-aza reduced β-catenin mRNA and protein expression in vivo and in vitro. Animal experiments confirmed that 5-aza could significantly alleviate bleomycin-induced pulmonary fibrosis in mice. Thus, changes of promoter hypermethylation might downregulate SFRP1 and SFRP4 at different stages of pulmonary fibrosis, and the finding supports the usefulness of DNMT inhibitors, which might effectively reverse activation of β-catenin and reduce pulmonary fibrosis in mice. These data provide a possible new direction in the research on pulmonary fibrosis treatments.

Role of Endothelial Cells in Renal Fibrosis

Renal fibrosis has been regarded as the common pathway of end-stage renal failure. Understanding the fundamental mechanism that leads to renal fibrosis is essential for developing better therapeutic options for chronic kidney diseases. So far, the main abstractions are on the injury of tubular epithelial cells, activation of interstitial cells, expression of chemotactic factor and adhesion molecule, infiltration of inflammatory cells and homeostasis of ECM. However, emerging studies revealed that endothelial cells (ECs) might happen to endothelial-to-mesenchymal transition (EndMT) dependent and/or independent endothelial dysfunction, which were supposed to accelerate renal fibrosis and are identified as new mechanisms for the proliferation of myofibroblasts as well. In this chapter, we are about to interpret the role of ECs in renal fibrosis and analyze the related molecules and pathways of both EndMT and EndMT independent endothelial dysfunction.

Epigenetic Modification Mechanisms Involved in Inflammation and Fibrosis in Renal Pathology

The growing incidence of obesity, hypertension, and diabetes, coupled with the aging of the population, is increasing the prevalence of renal diseases in our society. Chronic kidney disease (CKD) is characterized by persistent inflammation, fibrosis, and loss of renal function leading to end-stage renal disease. Nowadays, CKD treatment has limited effectiveness underscoring the importance of the development of innovative therapeutic options. Recent studies have identified how epigenetic modifications participate in the susceptibility to CKD and have explained how the environment interacts with the renal cell epigenome to contribute to renal damage. Epigenetic mechanisms regulate critical processes involved in gene regulation and downstream cellular responses. The most relevant epigenetic modifications that play a critical role in renal damage include DNA methylation, histone modifications, and changes in miRNA levels. Importantly, these epigenetic modifications are reversible and, therefore, a source of potential therapeutic targets. Here, we will explain how epigenetic mechanisms may regulate essential processes involved in renal pathology and highlight some possible epigenetic therapeutic strategies for CKD treatment.

Modeling epigenetic modifications in renal development and disease with organoids and genome editing

Understanding epigenetic mechanisms is crucial to our comprehension of gene regulation in development and disease. In the past decades, different studies have shown the role of epigenetic modifications and modifiers in renal disease, especially during its progression towards chronic and end-stage renal disease. Thus, the identification of genetic variation associated with chronic kidney disease has resulted in better clinical management of patients. Despite the importance of these findings, the translation of genotype-phenotype data into gene-based medicine in chronic kidney disease populations still lacks faithful cellular or animal models that recapitulate the key aspects of the human kidney. The latest advances in the field of stem cells have shown that it is possible to emulate kidney development and function with organoids derived from human pluripotent stem cells. These have successfully recapitulated not only kidney differentiation, but also the specific phenotypical traits related to kidney function. The combination of this methodology with CRISPR/Cas9 genome editing has already helped researchers to model different genetic kidney disorders. Nowadays, CRISPR/Cas9-based approaches also allow epigenetic modifications, and thus represent an unprecedented tool for the screening of genetic variants, epigenetic modifications or even changes in chromatin structure that are altered in renal disease. In this Review, we discuss these technical advances in kidney modeling, and offer an overview of the role of epigenetic regulation in kidney development and disease.

Polyamine Metabolism and Gene Methylation in Conjunction with One-Carbon Metabolism

Recent investigations have revealed that changes in DNA methylation status play an important role in aging-associated pathologies and lifespan. The methylation of DNA is regulated by DNA methyltransferases (DNMT1, DNMT3a, and DNMT3b) in the presence of S-adenosylmethionine (SAM), which serves as a methyl group donor. Increased availability of SAM enhances DNMT activity, while its metabolites, S-adenosyl-l-homocysteine (SAH) and decarboxylated S-adenosylmethionine (dcSAM), act to inhibit DNMT activity. SAH, which is converted from SAM by adding a methyl group to cytosine residues in DNA, is an intermediate precursor of homocysteine. dcSAM, converted from SAM by the enzymatic activity of adenosylmethionine decarboxylase, provides an aminopropyl group to synthesize the polyamines spermine and spermidine. Increased homocysteine levels are a significant risk factor for the development of a wide range of conditions, including cardiovascular diseases. However, successful homocysteine-lowering treatment by vitamins (B6, B12, and folate) failed to improve these conditions. Long-term increased polyamine intake elevated blood spermine levels and inhibited aging-associated pathologies in mice and humans. Spermine reversed changes (increased dcSAM, decreased DNMT activity, aberrant DNA methylation, and proinflammatory status) induced by the inhibition of ornithine decarboxylase. The relation between polyamine metabolism, one-carbon metabolism, DNA methylation, and the biological mechanism of spermine-induced lifespan extension is discussed.

Hydrogen sulfide improves postischemic neoangiogenesis in the hind limb of cystathionine-β-synthase mutant mice via PPAR-γ/VEGF axis

Neoangiogenesis is a fundamental process which helps to meet energy requirements, tissue growth, and wound healing. Although previous studies showed that Peroxisome proliferator-activated receptor (PPAR-γ) regulates neoangiogenesis via upregulation of vascular endothelial growth factor (VEGF), and both VEGF and PPAR-γ expressions were inhibited during hyperhomocysteinemic (HHcy), whether these two processes could trigger pathological effects in skeletal muscle via compromising neoangiogenesis has not been studied yet. Unfortunately, there are no treatment options available to date for ameliorating HHcy-mediated neoangiogenic defects. Hydrogen sulfide (H2 S) is a novel gasotransmitter that can induce PPAR-γ levels. However, patients with cystathionine-β-synthase (CBS) mutation(s) cannot produce a sufficient amount of H2 S. We hypothesized that exogenous supplementation of H2 S might improve HHcy-mediated poor neoangiogenesis via the PPAR-γ/VEGF axis. To examine this, we created a hind limb femoral artery ligation (FAL) in CBS+/- mouse model and treated them with GYY4137 (a long-acting H2 S donor compound) for 21 days. To evaluate neoangiogenesis, we used barium sulfate angiography and laser Doppler blood flow measurements in the ischemic hind limbs of experimental mice post-FAL to assess blood flow. Proteins and mRNAs levels were studied by Western blots and qPCR analyses. HIF1-α, VEGF, PPAR-γ and p-eNOS expressions were attenuated in skeletal muscle of CBS+/- mice after 21 days of FAL in comparison to wild-type (WT) mice, that were improved via GYY4137 treatment. We also found that the collateral vessel density and blood flow were significantly reduced in post-FAL CBS+/- mice compared to WT mice and these effects were ameliorated by GYY4137. Moreover, we found that plasma nitrite levels were decreased in post-FAL CBS+/- mice compared to WT mice, which were mitigated by GYY4137 supplementation. These results suggest that HHcy can inhibit neoangiogenesis via antagonizing the angiogenic signal pathways encompassing PPAR-γ/VEGF axis and that GYY4137 could serve as a potential therapeutic to alleviate the harmful metabolic effects of HHcy conditions.

Ten-eleven translocation 2 demethylates the MMP9 promoter, and its down-regulation in preeclampsia impairs trophoblast migration and invasion

Preeclampsia is the most common clinical disorder in pregnancy and might result from disordered uterine environments caused by epigenetic modifications, including deregulation of DNA methylation/demethylation. Recent research has indicated that 5-hydroxymethylcytosine (5hmC), a DNA base derived from 5-methylcytosine (5mC) via oxidation by ten-eleven translocation (TET) enzymes, is involved in DNA methylation-related plasticity. Here, we report that TET2 expression and 5hmC abundance are significantly altered in the placentas from preeclampsia patients. shRNA-mediated TET2 knockdown (shTET2) reduced trophoblast migration and invasion when cultured in Matrigel. Both real-time PCR of matrix metalloproteinase (MMP)-related transcripts and a human angiogenesis antibody array indicated that TET2 knockdown in trophoblasts inhibits the expression of MMP transcript, of which MMP9 represented one of the most significant TET2 downstream targets. Using an established shTET2 HTR-8/SVneo cell model, we further confirmed alterations of 5hmC levels and MMP9 expression at both mRNA and protein levels. In particular, we found that TET2 bound to and removed 5mC modifications at the MMP9 promoter region. Interestingly, in TET2 knockdown cells, both MMP9 expression and the compromised trophoblast phenotype could be rescued by vitamin C, an activator of TET enzyme activity. Finally, TET2 expression correlated with MMP9 levels in placenta samples from the preeclampsia patients, indicating that TET2 deregulation is critically involved in the pathogenesis of preeclampsia through down-regulation of MMP9 expression. Our findings highlight a critical role of TET2 in regulating trophoblast cell migration through demethylation at the MMP9 promoter, and suggest that down-regulation of the TET2-MMP9-mediated pathway contributes to preeclampsia pathogenesis.

SMYD2 promoter DNA methylation is associated with abdominal aortic aneurysm (AAA) and SMYD2 expression in vascular smooth muscle cells

Background

Abdominal aortic aneurysm (AAA) is a deadly cardiovascular disease characterised by the gradual, irreversible dilation of the abdominal aorta. AAA is a complex genetic disease but little is known about the role of epigenetics. Our objective was to determine if global DNA methylation and CpG-specific methylation at known AAA risk loci is associated with AAA, and the functional effects of methylation changes.

Results

We assessed global methylation in peripheral blood mononuclear cell DNA from 92 individuals with AAA and 93 controls using enzyme-linked immunosorbent assays, identifying hyper-methylation in those with large AAA and a positive linear association with AAA diameter (P < 0.0001, R² = 0.3175).We then determined CpG methylation status of regulatory regions in genes located at AAA risk loci identified in genome-wide association studies, using bisulphite next-generation sequencing (NGS) in vascular smooth muscle cells (VSMCs) taken from aortic tissues of 44 individuals (24 AAAs and 20 controls). In IL6R, 2 CpGs were hyper-methylated (P = 0.0145); in ERG, 13 CpGs were hyper-methylated (P = 0.0005); in SERPINB9, 6 CpGs were hypo-methylated (P = 0.0037) and 1 CpG was hyper-methylated (P = 0.0098); and in SMYD2, 4 CpGs were hypo-methylated (P = 0.0012).RT-qPCR was performed for each differentially methylated gene on mRNA from the same VSMCs and compared with methylation. This analysis revealed downregulation of SMYD2 and SERPINB9 in AAA, and a direct linear relationship between SMYD2 promoter methylation and SMYD2 expression (P = 0.038). Furthermore, downregulation of SMYD2 at the site of aneurysm in the aortic wall was further corroborated in 6 of the same samples used for methylation and gene expression analysis with immunohistochemistry.

Conclusions

This study is the first to assess DNA methylation in VSMCs from individuals with AAA using NGS, and provides further evidence there is an epigenetic basis to AAA. Our study shows that methylation status of the SMYD2 promoter may be linked with decreased SMYD2 expression in disease pathobiology. In support of our work, downregulated SMYD2 has previously been associated with adverse cardiovascular physiology and inflammation, which are both hallmarks of AAA. The identification of such adverse epigenetic modifications could potentially contribute towards the development of epigenetic treatment strategies in the future.

5-aza-2'-deoxycytidine, a DNA methylation inhibitor, attenuates hyperoxia-induced lung fibrosis via re-expression of P16 in neonatal rats

BackgroundP16 methylation plays an important role in the pathogenesis of hyperoxia-induced lung fibrosis. 5-aza-2'-deoxycytidine (5-aza-CdR) is a major methyltransferase-specific inhibitor. In this study, the effects of 5-aza-CdR on a hyperoxia-induced lung fibrosis in neonatal rats were investigated.MethodsRat pups were exposed to 85% O₂ for 21 days of and received intraperitoneal injections of 5-aza-CdR or normal saline (NS) once every other day. Survival rates and lung coefficients were calculated. Hematoxylin-eosin staining was performed to analyze the degree of lung fibrosis. Collagen content and TGF-β1 levels were determined. A methylation-specific polymerase chain reaction and western blotting were performed to determine P16 methylation status and P16, cyclin D1, and E2F1 protein expression.Results5-aza-CdR treatment during hyperoxia significantly improved the survival rate and weight gain, while it decreases the degree of lung fibrosis and levels of hydroxyproline and TGF-β1. Hyperoxia induced abnormal P16 methylation and 5-aza-CdR effectively reversed the hypermethylation of P16. Expression of the P16 protein in lung tissues was enhanced, while cyclin D1 and E2F1 protein were reduced by 5-aza-CdR treatment during hyperoxia.ConclusionThese data show that 5-aza-CdR attenuated lung fibrosis in neonatal rats exposed to hyperoxia by lowering hydroxyproline and TGF-β1 expression and via re-expression of P16 in neonatal rats.

Epigenetic modifications in hyperhomocysteinemia: potential role in diabetic retinopathy and age-related macular degeneration

To study Hyperhomocysteinemia (HHcy)-induced epigenetic modifications as potential mechanisms of blood retinal barrier (BRB) dysfunction, retinas isolated from three- week-old mice with elevated level of Homocysteine (Hcy) due to lack of the enzyme cystathionine β-synthase (cbs^-/- , cbs^+/- and cbs^+/+ ), human retinal endothelial cells (HRECs), and human retinal pigmented epithelial cells (ARPE-19) treated with or without Hcy were evaluated for (1) histone deacetylases (HDAC), (2) DNA methylation (DNMT), and (3) miRNA analysis. Differentially expressed miRNAs in mice with HHcy were further compared with miRNA analysis of diabetic mice retinas (STZ) and miRNAs within the exosomes released from Hcy-treated RPEs. Differentially expressed miRNAs were further evaluated for predicted target genes and associated pathways using Ingenuity Pathway Analysis. HHcy significantly increased HDAC and DNMT activity in HRECs, ARPE-19, and cbs mice retinas, whereas inhibition of HDAC and DNMT decreased Hcy-induced BRB dysfunction. MiRNA profiling detected 127 miRNAs in cbs^+/- and 39 miRNAs in cbs^-/- mice retinas, which were significantly differentially expressed compared to cbs^+/+ . MiRNA pathway analysis showed their involvement in HDAC and DNMT activation, endoplasmic reticulum (ER), and oxidative stresses, inflammation, hypoxia, and angiogenesis pathways. Hcy-induced epigenetic modifications may be involved in retinopathies associated with HHcy, such as age-related macular degeneration and diabetic retinopathy.

Cholesterol lowering treatment restores blood global DNA methylation in chronic kidney disease (CKD) patients

BACKGROUND AND AIMS

Chronic kidney disease (CKD) is characterized by increased oxidative stress (OS). In consideration of the well-known link between OS and DNA methylation we assessed DNA methylcytosine (mCyt) concentrations in CKD patients at baseline and during cholesterol lowering treatment.

METHODS AND RESULTS

DNA methylation and OS indices (malonyldialdehyde, MDA; allantoin/uric acid ratio, All/UA) were measured in 30 CKD patients randomized to three cholesterol lowering regimens for 12 months (simvastatin 40 mg/day, ezetimibe/simvastatin 10/20 mg/day, or ezetimibe/simvastatin 10/40 mg/day) and 30 age- and sex-matched healthy controls. DNA methylation was significantly lower in CKD patients vs. controls (4.06 ± 0.20% vs. 4.27 ± 0.17% mCyt, p = 0.0001). Treatment significantly increased mCyt DNA concentrations in all patients (4.06 ± 0.04% at baseline; 4.12 ± 0.03% at 4 months; 4.17 ± 0.03% at 8 months; and 4.20 ± 0.02% at 12 months, p = 0.0001 for trend). A trend for a greater effect on DNA methylation was observed with combined treatment ezetimibe/simvastatin 10/40 mg/day (+5.2% after one year treatment). The treatment-associated mCyt increase was significantly correlated with the concomitant reduction in MDA concentrations and All/AU ratios.

CONCLUSION

Our results demonstrate that CKD patients have a lower degree of DNA methylation and that cholesterol lowering treatment restores mCyt DNA concentrations to levels similar to healthy controls. The treatment-associated increase in DNA methylation is correlated with a concomitant reduction in OS markers. The study was registered at clinicaltrials.gov (NCT00861731).

Toll-like receptor 4 mediates vascular remodeling in hyperhomocysteinemia

Although hyperhomocysteinemia (HHcy) is known to promote downstream pro-inflammatory cytokine elevation, the precise mechanism is still unknown. One of the possible receptors that could have significant attention in the field of hypertension is toll-like receptor 4 (TLR-4). TLR-4 is a cellular membrane protein that is ubiquitously expressed in all cell types of the vasculature. Its mutation can attenuate the effects of HHcy-mediated vascular inflammation and mitochondria- dependent cell death that suppresses hypertension. In this review, we observed that HHcy induces vascular remodeling through immunological adaptation, promoting inflammatory cytokine up-regulation (IL-1β, IL-6, TNF-α) and initiation of mitochondrial dysfunction leading to cell death and chronic vascular inflammation. The literature suggests that HHcy promotes TLR-4-driven chronic vascular inflammation and mitochondria-mediated cell death inducing peripheral vascular remodeling. In the previous studies, we have characterized the role of TLR-4 mutation in attenuating vascular remodeling in hyperhomocysteinemia. This review includes, but is not limited to, the physiological synergistic aspects of the downstream elevation of cytokines found within the vascular inflammatory cascade. These events subsequently induce mitochondrial dysfunction defined by excessive mitochondrial fission and mitochondrial apoptosis contributing to vascular remodeling followed by hypertension.

Hydrogen sulfide alleviates hypertensive kidney dysfunction through an epigenetic mechanism

Hypertension is a major risk factor for chronic kidney disease (CKD), and renal inflammation is an integral part in this pathology. Hydrogen sulfide (H₂S) has been shown to mitigate renal damage through reduction in blood pressure and ROS; however, the exact mechanisms are not clear. While several studies have underlined the role of epigenetics in renal inflammation and dysfunction, the mechanisms through which epigenetic regulators play a role in hypertension are not well defined. In this study, we sought to identify whether microRNAs are dysregulated in response to angiotensin II (ANG II)-induced hypertension in the kidney and whether a H₂S donor, GYY4137, could reverse the microRNA alteration and kidney function. Wild-type (C57BL/6J) mice were treated without or with ANG II and GYY4137 for 4 wk. Blood pressure, renal blood flow, and resistive index (RI) were measured. MicroRNA microarrays were conducted and subsequent target prediction revealed genes associated with a proinflammatory response. ANG II treatment significantly increased blood pressure, decreased blood flow in the renal cortex, increased RI, and reduced renal function. These effects were ameliorated in mice treated with GYY4137. Microarray analysis revealed downregulation of miR-129 in ANG II-treated mice and upregulation after GYY4137 treatment. Quantitation of proteins involved in the inflammatory response and DNA methylation revealed upregulation of IL-17A and DNA methyltransferase 3a, whereas H₂S production enzymes and anti-inflammatory IL-10 were reduced. Taken together, our data suggest that downregulation of miR-129 plays a significant role in ANG II-induced renal inflammation and functional outcomes and that GYY4137 improves renal function by reversing miR-129 expression.NEW & NOTEWORTHY We investigated epigenetic changes that occur in the hypertensive kidney and how H₂S supplementation reverses adverse effects. Inflammation, aberrant methylation, and dysfunction were observed in the hypertensive kidney, and these effects were alleviated with H₂S supplementation. We identify miR-129 as a potential regulator of blood pressure and H₂S regulation.

Functional and Molecular Insights of Hydrogen Sulfide Signaling and Protein Sulfhydration

Hydrogen sulfide (H2S), a novel gasotransmitter, is endogenously synthesized by multiple enzymes that are differentially expressed in the peripheral tissues and central nervous systems. H2S regulates a wide range of physiological processes, namely cardiovascular, neuronal, immune, respiratory, gastrointestinal, liver, and endocrine systems, by influencing cellular signaling pathways and sulfhydration of target proteins. This review focuses on the recent progress made in H2S signaling that affects mechanistic and functional aspects of several biological processes such as autophagy, inflammation, proliferation and differentiation of stem cell, cell survival/death, and cellular metabolism under both physiological and pathological conditions. Moreover, we highlighted the cross-talk between nitric oxide and H2S in several bilogical contexts.

Role of galectin-3 in autoimmune and non-autoimmune nephropathies

Galectins are evolutionary conserved β-galactoside binding proteins with a carbohydrate-recognition domain (CRD) of approximately 130 amino acids. In mammals, 15 members of the galectin family have been identified and classified into three subtypes according to CRD organization: prototype, tandem repeat-type and chimera-type galectins. Galectin-3 (gal-3) is the only chimera type galectin in vertebrates containing one CRD linked to an unusual long N-terminal domain which displays non-lectin dependent activities. Although recent studies revealed unique, pleiotropic and context-dependent functions of gal-3 in both extracellular and intracellular space, gal-3 specific pathways and its ligands have not been clearly defined yet. In the kidney gal-3 is involved in later stages of nephrogenesis as well as in renal cell cancer. However, gal-3 has recently been associated with lupus glomerulonephritis, with Familial Mediterranean Fever-induced proteinuria and renal amyloidosis. Gal-3 has been studied in experimental acute kidney damage and in the subsequent regeneration phase as well as in several models of chronic kidney disease, including nephropathies induced by aging, ischemia, hypertension, diabetes, hyperlipidemia, unilateral ureteral obstruction and chronic allograft injury. Because of the pivotal role of gal-3 in the modulation of immune system, wound repair, fibrosis and tumorigenesis, it is not surprising that gal-3 can be an intriguing prognostic biomarker as well as a promising therapeutic target in a great variety of diseases, including chronic kidney disease, chronic heart failure and cardio-renal syndrome. This review summarizes the functions of gal-3 in kidney pathophysiology focusing on the reported role of gal-3 in autoimmune diseases.

Homocysteine and hydrogen sulfide in epigenetic, metabolic and microbiota related renovascular hypertension

Over the past several years, hydrogen sulfide (H₂S) has been shown to be an important player in a variety of physiological functions, including neuromodulation, vasodilation, oxidant regulation, inflammation, and angiogenesis. H₂S is synthesized primarily through metabolic processes from the amino acid cysteine and homocysteine in various organ systems including neuronal, cardiovascular, gastrointestinal, and kidney. Derangement of cysteine and homocysteine metabolism and clearance, particularly in the renal vasculature, leads to H₂S biosynthesis deregulation causing or contributing to existing high blood pressure. While a variety of environmental influences, such as diet can have an effect on H₂S regulation and function, genetic factors, and more recently epigenetics, also have a vital role in H₂S regulation and function, and therefore disease initiation and progression. In addition, new research into the role of gut microbiota in the development of hypertension has highlighted the need to further explore these microorganisms and how they influence the levels of H₂S throughout the body and possibly exploiting microbiota for use of hypertension treatment. In this review, we summarize recent advances in the field of hypertension research emphasizing renal contribution and how H₂S physiology can be exploited as a possible therapeutic strategy to ameliorate kidney dysfunction as well as to control blood pressure.

Abnormally activated one-carbon metabolic pathway is associated with mtDNA hypermethylation and mitochondrial malfunction in the oocytes of polycystic gilt ovaries

Polycystic ovarian syndrome (PCOS) is associated with hyperhomocysteinemia and polycystic ovaries (PCO) usually produce oocytes of poor quality. However, the intracellular mechanism linking hyperhomocysteinemia and oocyte quality remains elusive. In this study, the quality of the oocytes isolated from healthy and polycystic gilt ovaries was evaluated in vitro in association with one-carbon metabolism, mitochondrial DNA (mtDNA) methylation, and mitochondrial function. PCO oocytes demonstrated impaired polar body extrusion, and significantly decreased cleavage and blastocyst rates. The mitochondrial distribution was disrupted in PCO oocytes, together with decreased mitochondrial membrane potential and deformed mitochondrial structure. The mtDNA copy number and the expression of mtDNA-encoded genes were significantly lower in PCO oocytes. Homocysteine concentration in follicular fluid was significantly higher in PCO group, which was associated with significantly up-regulated one-carbon metabolic enzymes betaine homocysteine methyltransferase (BHMT), glycine N-methyltransferase (GNMT) and the DNA methyltransferase DNMT1. Moreover, mtDNA sequences coding for 12S, 16S rRNA and ND4, as well as the D-loop region were significantly hypermethylated in PCO oocytes. These results indicate that an abnormal activation of one-carbon metabolism and hypermethylation of mtDNA may contribute, largely, to the mitochondrial malfunction and decreased quality of PCO-derived oocytes in gilts.