Aging and DNA methylation. BMC Biol. 2015;13:7. [PMID: 25637097 PMCID: PMC4311512 DOI: 10.1186/s12915-015-0118-4]

Exercise and bone health across the lifespan

With ageing, bone tissue undergoes significant compositional, architectural and metabolic alterations potentially leading to osteoporosis. Osteoporosis is the most prevalent bone disorder, which is characterised by progressive bone weakening and an increased risk of fragility fractures. Although this metabolic disease is conventionally associated with ageing and menopause, the predisposing factors are thought to be established during childhood and adolescence. In light of this, exercise interventions implemented during maturation are likely to be highly beneficial as part of a long-term strategy to maximise peak bone mass and hence delay the onset of age- or menopause-related osteoporosis. This notion is supported by data on exercise interventions implemented during childhood and adolescence, which confirmed that weight-bearing activity, particularly if undertaken during peripubertal development, is capable of generating a significant osteogenic response leading to bone anabolism. Recent work on human ageing and epigenetics suggests that undertaking exercise after the fourth decade of life is still important, given the anti-ageing effect and health benefits provided, potentially occurring via a delay in telomere shortening and modification of DNA methylation patterns associated with ageing. Exercise is among the primary modifiable factors capable of influencing bone health by preserving bone mass and strength, preventing the death of bone cells and anti-ageing action provided.

High-level dietary cadmium exposure is associated with global DNA hypermethylation in the gastropod hepatopancreas

5-methylcytosine (5mC) is a key epigenetic mark which influences gene expression and phenotype. In vertebrates, this epigenetic mark is sensitive to Cd exposure, but there is no information linking such an event with changes in global 5mC levels in terrestrial gastropods despite their importance as excellentecotoxicological bioindicators of metal contamination. Therefore, we first evaluated total 5mC content in DNA of the hepatopancreas of adult Cantareus aspersus with the aim to determine whether this epigenetic mark is responsive to Cd exposure. The experiment was conducted under laboratory conditions and involved a continuous exposure, multiple dose- and time-point (14, 28, and 56 days) study design. Hepatopancreas cadmium levels were measured using Flame Atomic Absorption Spectrometry and the percentage of 5-mC in samples using an ELISA-based colorimetric assay. Snail death rates were also assessed. Our results, for the first time, reveal the presence of 5mC in C. aspersus and provide evidence for Cd-induced changes in global 5mC levels in DNA of gastropods and mollusks. Although less sensitive than tissue accumulation, DNA methylation levels responded in a dose- and time-dependent manner to dietary cadmium, with exposure dose having a much stronger effect than exposure duration. An obvious trend of increasing 5mC levels was observed starting at 28 days of exposure to the second highest dose and this trend persisted at the two highest treatments for close to one month, when the experiment was terminated after 56 days. Moreover, a strong association was identified between Cd concentrations in the hepatopancreas and DNA methylation levels in this organ. These data indicate an overall trend towards DNA hypermethylation with elevated Cd exposure. No consistent lethal effect was observed, irrespective of time point and Cd-dosage. Overall, our findings suggest that the total 5mC content in DNA of the hepatopancreas of land snails is responsive to sublethal Cd exposure and give new insights into invertebrate environmental epigenetics.

Increased DNA methylation in the parvalbumin gene promoter is associated with methamphetamine dependence

Aim: The parvalbumin (PV)-containing subgroup of GABAergic neurons is particularly affected in schizophrenia and animal models of psychosis, including after methamphetamine (METH) administration. We investigated whether METH dependence and METH-induced psychosis may involve an effect on DNA methylation of the PVALB promoter. Materials & methods: The methylation of a PVALB promoter sequence was determined in 100 METH-dependent and 102 control subjects using pyrosequencing. Results: A significant increase in PVALB methylation was observed in METH dependence and METH-induced psychosis. No significant effect on long interspersed nucleotide element-1 methylation, a measure of global DNA methylation, was observed. Conclusion: These results demonstrate a specific association between elevated PVALB methylation and METH-induced psychosis. This finding may contribute to the GABAergic deficits associated with METH dependence.

The association between Alu hypomethylation and severity of type 2 diabetes mellitus

Background

Cellular senescence due to genomic instability is believed to be one of the mechanisms causing health problems in diabetes mellitus (DM). Low methylation levels of Alu elements or Alu hypomethylation, an epigenomic event causing genomic instability, were commonly found in aging people and patients with aging phenotypes, such as osteoporosis.

Results

We investigate Alu methylation levels of white blood cells of type 2 DM, pre-DM, and control. The DM group possess the lowest Alu methylation (P < 0.001, P < 0.0001 adjusted age). In the DM group, Alu hypomethylation is directly correlated with high fasting blood sugar, HbA1C, and blood pressure.

Conclusion

Genome-wide hypomethylation may be one of the underlining mechanisms causing genomic instability in type 2 DM. Moreover, Alu methylation levels may be a useful biomarker for monitoring cellular senescence in type 2 DM patients.

Electronic supplementary material

The online version of this article (10.1186/s13148-017-0395-6) contains supplementary material, which is available to authorized users.

Implications of DNA Methylation in Parkinson's Disease

It has been 200 years since Parkinson’s disease (PD) was first described, yet many aspects of its etiopathogenesis remain unclear. PD is a progressive and complex neurodegenerative disorder caused by genetic and environmental factors including aging, nutrition, pesticides and exposure to heavy metals. DNA methylation may be altered in response to some of these factors; therefore, it is proposed that epigenetic mechanisms, particularly DNA methylation, can have a fundamental role in gene–environment interactions that are related with PD. Epigenetic changes in PD-associated genes are now widely studied in different populations, to discover the mechanisms that contribute to disease development and identify novel biomarkers for early diagnosis and future pharmacological treatment. While initial studies sought to find associations between promoter DNA methylation and the regulation of associated genes in PD brain tissue, more recent studies have described concordant DNA methylation patterns between blood and brain tissue DNA. These data justify the use of peripheral blood samples instead of brain tissue for epigenetic studies. Here, we summarize the current data about DNA methylation changes in PD and discuss the potential of DNA methylation as a potential biomarker for PD. Additionally, we discuss environmental and nutritional factors that have been implicated in DNA methylation. Although the search for significant DNA methylation changes and gene expression analyses of PD-associated genes have yielded inconsistent and contradictory results, epigenetic modifications remain under investigation for their potential to reveal the link between environmental risk factors and the development of PD.

Epigenetic effects of environmental chemicals: insights from zebrafish

Zebrafish have been extensively used for studying vertebrate development and modeling human diseases such as cancer. In the last two decades, they have also emerged as an important model for developmental toxicology research and, more recently, for studying the developmental origins of health and disease (DOHaD). It is widely recognized that epigenetic mechanisms mediate the persistent effects of exposure to chemicals during sensitive windows of development. There is considerable interest in understanding the epigenetic mechanisms associated with DOHaD using zebrafish as a model system. This review summarizes our current knowledge on the effects of environmental chemicals on DNA methylation, histone modifications and noncoding RNAs in the context of DOHaD, and suggest some key considerations in designing experiments for characterizating the mechanisms of action.

Increased DNA Methylation and Reduced Expression of Transcription Factors in Human Osteoarthritis Cartilage

OBJECTIVE

To analyze the methylome of normal and osteoarthritic (OA) knee articular cartilage and to determine the role of DNA methylation in the regulation of gene expression in vitro.

METHODS

DNA was isolated from human normal (n = 11) and OA (n = 12) knee articular cartilage and analyzed using the Infinium HumanMethylation450 BeadChip array. To integrate methylation and transcription, RNA sequencing was performed on normal and OA cartilage and validated by quantitative polymerase chain reaction. Functional validation was performed in the human TC28 cell line and primary chondrocytes that were treated with the DNA methylation inhibitor 5-aza-2'-deoxycytidine (5-aza-dC).

RESULTS

DNA methylation profiling revealed 929 differentially methylated sites between normal and OA cartilage, comprising a total of 500 individual genes. Among these, 45 transcription factors that harbored differentially methylated sites were identified. Integrative analysis and subsequent validation showed a subset of 6 transcription factors that were significantly hypermethylated and down-regulated in OA cartilage (ATOH8, MAFF, NCOR2, TBX4, ZBTB16, and ZHX2). Upon 5-aza-dC treatment, TC28 cells showed a significant increase in gene expression for all 6 transcription factors. In primary chondrocytes, ATOH8 and TBX4 were increased after 5-aza-dC treatment.

CONCLUSION

Our findings reveal that normal and OA knee articular cartilage have significantly different methylomes. The identification of a subset of epigenetically regulated transcription factors with reduced expression in OA may represent an important mechanism to explain changes in the chondrocyte transcriptome and function during OA pathogenesis.

Neuronal DNA Methyltransferases: Epigenetic Mediators between Synaptic Activity and Gene Expression?

DNMT3A and 3B are the main de novo DNA methyltransferases (DNMTs) in the brain that introduce new methylation marks to non-methylated DNA in postmitotic neurons. DNA methylation is a key epigenetic mark that is known to regulate important cellular processes in neuronal development and brain plasticity. Accumulating evidence disclosed rapid and dynamic changes in DNA methylation of plasticity-relevant genes that are important for learning and memory formation. To understand how DNMTs contribute to brain function and how they are regulated by neuronal activity is a prerequisite for a deeper appreciation of activity-dependent gene expression in health and disease. This review discusses the functional role of de novo methyltransferases and in particular DNMT3A1 in the adult brain with special emphasis on synaptic plasticity, memory formation, and brain disorders.

Age-Related Changes in DNA Methylation Associated with Shifting Th1/Th2 Balance

This study was conducted in order to explore age-related changes in the production of Th1 and Th2 cytokines and determine the corresponding status of DNA methylation. The plasma IL-4 and IFN-γ levels and expression of Th-related cytokines and transcription factors in CD4+ splenocytes were observed in mice at different weeks of age. The DNA methylation levels of IL-4 and IFN-γ promoters and the related regulatory regions in CD4+ splenocytes of mice at different weeks of age were analyzed. The DNA methyltransferase (DNMT) levels in CD4+ splenocytes of mice were analyzed. Changes in plasma IL-4 and IFN-γ levels after 5-AZA injection were evaluated. Plasma IL-4 and IL-4 expression in CD4+ splenocytes declined with increasing age, while the IFN-γ expression levels increased. Th-related transcription factors showed no differences in mice at different weeks of age. The DNMT1 and DNMT3b mRNA expression did not show significant changes in CD4+ splenocytes, whereas the DNMT3a mRNA expression increased with age. DNA methylation in the IL-4 promoter was increased, while DNA methylation in the IFN-γ promoter was decreased. The methylation of RSH7, CNS-1, and HSV increased significantly with age. Age-related changes in DNA methylation may be associated with the shift in Th1/Th2 balance.

Environmental Deflection: The Impact of Toxicant Exposures on the Aging Epigenome

Epigenetic drift and age-related methylation have both been used in the literature to describe changes in DNA methylation that occurs with aging. However, ambiguity remains regarding the exact definition of both of these terms, and neither of these fields of study explicitly considers the impact of environmental factors on the aging epigenome. Recent twin studies have demonstrated longitudinal, pair-specific discordance in DNA methylation patterns, suggesting an effect of the environment on age-related methylation and/or epigenetic drift. Supporting this idea, other new reports have shown clear environment- and toxicant-mediated shifts away from the baseline rates of age-related methylation and epigenetic drift within an organism, a process we now term "environmental deflection." By defining and delineating environmental deflection, this contemporary review aims to highlight the effects of specific toxicological factors on the rate of DNA methylation changes that occur over the life course. In an effort to inform future epigenetics-based toxicology studies, a field of research now classified as toxicoepigenetics, we provide clear definitions and examples of "epigenetic drift" and "age-related methylation," summarize the recent evidence for environmental deflection of the aging epigenome, and discuss the potential functional effects of environmental deflection.

DNA methylation signatures in peripheral blood strongly predict all-cause mortality

DNA methylation (DNAm) has been revealed to play a role in various diseases. Here we performed epigenome-wide screening and validation to identify mortality-related DNAm signatures in a general population-based cohort with up to 14 years follow-up. In the discovery panel in a case-cohort approach, 11,063 CpGs reach genome-wide significance (FDR<0.05). 58 CpGs, mapping to 38 well-known disease-related genes and 14 intergenic regions, are confirmed in a validation panel. A mortality risk score based on ten selected CpGs exhibits strong association with all-cause mortality, showing hazard ratios (95% CI) of 2.16 (1.10–4.24), 3.42 (1.81–6.46) and 7.36 (3.69–14.68), respectively, for participants with scores of 1, 2–5 and 5+ compared with a score of 0. These associations are confirmed in an independent cohort and are independent from the ‘epigenetic clock'. In conclusion, DNAm of multiple disease-related genes are strongly linked to mortality outcomes. The DNAm-based risk score might be informative for risk assessment and stratification.

DNA methylation is modulated by environmental factors and has a role in many complex diseases. Here, the authors find that methylation at specific DNA sites is associated with all-cause mortality, and a methylation-based risk score may be informative for risk assessment and stratification.

Aberrant methylation of tumour suppressor genes WT1, GATA5 and PAX5 in hepatocellular carcinoma

BACKGROUND

Aberrant hypermethylation of tumour suppressor genes (TSGs) occurring in hepatocellular carcinoma (HCC) could provide a mean of molecular characterisation of this cancer. The aim of this study was to investigate promoter methylation and gene expression of selected TSGs in HCC to identify candidate genes for further validation as potential biomarkers.

METHODS

Methylation-specific multiplex ligation-dependent probe amplification method was used to measure the methylation status of 25 TSGs in 49 HCC samples and 36 corresponding non-cancerous liver tissue samples. Relative expression of the differentially methylated genes was assessed at the mRNA level using quantitative PCR.

RESULTS

We observed a significantly higher methylation in genes WT1, PAX5, PAX6, PYCARD and GATA5 in HCC compared with control samples. The expression of PAX5 was significantly decreased by methylation; conversely methylation of WT1 was associated with higher mRNA levels. Methylation of GATA5 was significantly associated with overall survival and methylation of WT1 and PAX5 significantly varied between patients with ALBI score 1 vs. 2+3. Moreover, PAX5 was significantly more methylated in patients with tumour grade 2+3 vs. grade 1, and methylation of the PAX5 correlated with the patient's age at the time of diagnosis.

CONCLUSIONS

HCC evince aberrant promoter methylation of WT1, PAX5, PAX6, PYCARD and GATA5 genes. Correlation between GATA5, WT1 and PAX5 methylation and clinical/histological parameters is suggestive of applicability of these markers in non-invasive (epi)genetic testing in HCC.

Marked for death: targeting epigenetic changes in cancer

In the past few years, it has become clear that mutations in epigenetic regulatory genes are common in human cancers. Therapeutic strategies are now being developed to target cancers with mutations in these genes using specific chemical inhibitors. In addition, a complementary approach based on the concept of synthetic lethality, which allows exploitation of loss-of-function mutations in cancers that are not targetable by conventional methods, has gained traction. Both of these approaches are now being tested in several clinical trials. In this Review, we present recent advances in epigenetic drug discovery and development, and suggest possible future avenues of investigation to drive progress in this area.

Conserved effect of aging on DNA methylation and association with EZH2 polycomb protein in mice and humans

In humans, DNA methylation at specific CpG sites can be used to estimate the 'epigenetic clock', a biomarker of aging and health. The mechanisms that regulate the aging epigenome and level of conservation are not entirely clear. We performed affinity-based enrichment with methyl-CpG binding domain protein followed by high-throughput sequencing (MBD-seq) to assay DNA methylation in mouse samples. Consistent with previous reports, aging is associated with increase in methylation at CpG islands that likely overlap regulatory regions of genes that have been implicated in cancers (e.g., C1ql3, Srd5a2 and Ptk7). The differentially methylated regions in mice have high sequence conservation in humans and the pattern of methylation is also largely conserved between the two species. Based on human ENCODE data, these sites are targeted by polycomb proteins, including EZH2. Chromatin immunoprecipitation confirmed that these regions interact with EZH2 in mice as well, and there may be reduction in EZH2 occupancy with age at C1ql3. This adds to the growing evidence that EZH2 is part of the protein machinery that shapes the aging epigenome. The conservation in both sequence and methylation patterns of the age-dependent CpGs indicate that the epigenetic clock is a fundamental feature of aging in mammals.

Antibodies specific for nucleic acid modifications

Nucleotide modifications constitute marks in RNA and DNA that contribute to gene regulation, development and other cellular processes. The understanding of their intricate molecular roles has been hampered by the high number of different modifications, the lack of effective methods and tools for their detection and quantification as well as by their complex structure-function relationship. The recent development of RNA and DNA immunoprecipitation followed by high-throughput sequencing (RIP- and DIP-seq) initiated detailed transcriptome- and genome-wide studies. Both techniques depend on highly specific and sensitive antibodies to specifically enrich the targeted modified nucleotides without background or potential biases. Here, we review the challenges and developments when generating and validating antibodies targeting modified nucleotides. We discuss antibody-antigen interactions, different strategies of antigen generation and compare different binder formats suitable for state-of-the-art high resolution mapping and imaging technologies.

The Ageing Brain: Effects on DNA Repair and DNA Methylation in Mice

Base excision repair (BER) may become less effective with ageing resulting in accumulation of DNA lesions, genome instability and altered gene expression that contribute to age-related degenerative diseases. The brain is particularly vulnerable to the accumulation of DNA lesions; hence, proper functioning of DNA repair mechanisms is important for neuronal survival. Although the mechanism of age-related decline in DNA repair capacity is unknown, growing evidence suggests that epigenetic events (e.g., DNA methylation) contribute to the ageing process and may be functionally important through the regulation of the expression of DNA repair genes. We hypothesize that epigenetic mechanisms are involved in mediating the age-related decline in BER in the brain. Brains from male mice were isolated at 3-32 months of age. Pyrosequencing analyses revealed significantly increased Ogg1 methylation with ageing, which correlated inversely with Ogg1 expression. The reduced Ogg1 expression correlated with enhanced expression of methyl-CpG binding protein 2 and ten-eleven translocation enzyme 2. A significant inverse correlation between Neil1 methylation at CpG-site2 and expression was also observed. BER activity was significantly reduced and associated with increased 8-oxo-7,8-dihydro-2'-deoxyguanosine levels. These data indicate that Ogg1 and Neil1 expression can be epigenetically regulated, which may mediate the effects of ageing on DNA repair in the brain.

Health, Health Care, and Systems Science: Emerging Paradigm

Health is a continuum of an optimized state of a biologic system, an outcome of positive relationships with the self and others. A healthy system follows the principles of systems science derived from observations of nature, highlighting the character of relationships as the key determinant.

Relationships evolve from our decisions, which are consequential to the function of our own biologic system on all levels, including the genome, where epigenetics impact our morphology. In healthy systems, decisions emanate from the reciprocal collaboration of hippocampal memory and the executive prefrontal cortex.

We can decide to change relationships through choices. What is selected, however, only represents the cognitive interpretation of our limited sensory perception; it strongly reflects inherent biases toward either optimizing state, making a biologic system healthy, or not. Health or its absence is then the outcome; there is no inconsequential choice.

Public health effort should not focus on punitive steps (e.g. taxation of unhealthy products or behaviors) in order to achieve a higher level of public’s health. It should teach people the process of making healthy decisions; otherwise, people will just migrate/shift from one unhealthy product/behavior to another, and well-intended punitive steps will not make much difference.

Physical activity, accompanied by nutrition and stress management, have the greatest impact on fashioning health and simultaneously are the most cost-effective measures. Moderate-to-vigorous exercise not only improves aerobic fitness but also positively influences cognition, including memory and senses. Collective, rational societal decisions can then be anticipated.

Health care is a business system principally governed by self-maximizing decisions of its components; uneven and contradictory outcomes are the consequences within such a non-optimized system.

Health is not health care. We are biologic systems subject to the laws of biology in spite of our incongruous decisions that are detrimental to health. A biologic system/a human body originates from structural, deterministic genes as well as shared epigenetic memory of our ancestors affecting our bodily function and structure. The political governing systems’ vertical hierarchy has control over money and laws, neither of which materially affect individual lifestyle/behavioral choices toward health. Improved health comes from focusing on enhancing the biologic age and not the chronologic one, which simply represents a linear time from a birth certificate to a death certificate and is applicable only in its extremes. “Age-related diseases” are simply reflections of a given culture. Biologic age, reflecting the actual state of health, could be used in all health-related assessments including health-life insurance premiums, licensing of job categories, etc., all with a broader and healthy societal impact.

Cerebral white matter hyperintensities on MRI and acceleration of epigenetic aging: the atherosclerosis risk in communities study

Background

Cerebral white matter hyperintensities (WMH) on magnetic resonance imaging (MRI) are part of the spectrum of brain vascular injury accompanying aging and are associated with a substantial risk of stroke and dementia. We investigated the association of cerebral WMH burden on MRI with a DNA methylation-based biomarker of aging, termed DNA methylation age acceleration, which represents the deviation of the DNA methylation-predicted age from the chronologic age.

Results

In this cross-sectional observational study of 713 African-American participants of the Atherosclerosis Risk in Communities study, aged 51–73 years, estimates of predicted age were obtained based on two algorithms (Hannum et al. and Horvath) from DNA methylation measured using the Illumina HM450 array on genomic DNA extracted from blood. Age acceleration, calculated as the residual values from the regression of each of the predicted age measures onto the chronologic age, was significantly associated with WMH burden after accounting for chronologic age and sex, body mass index, systolic blood pressure, hypertension, diabetes, current smoking, and blood cell composition, and results were similar for either Hannum et al.- or Horvath-derived estimates (P = 0.016 and 0.026). An age acceleration increase by 1 year was associated with an increase of WMH burden by ~1 grade. To shed light on possible biological mechanisms underlying this association, we conducted a genome-wide association study of age acceleration and identified four loci harboring genes implicated in hemostasis, cell proliferation, protein degradation, and histone methylation. However, none of these loci were associated with WMH burden.

Conclusions

In this population-based study of middle-aged to older African-American adults, we report an association between accelerated epigenetic aging and increased WMH burden, independent of known risk factors, including chronologic age. Additional studies are needed to clarify whether DNA methylation age reflects biological mechanisms implicated in the aging of the cerebral white matter.

Electronic supplementary material

The online version of this article (doi:10.1186/s13148-016-0302-6) contains supplementary material, which is available to authorized users.

Investigating the specific core genetic-and-epigenetic networks of cellular mechanisms involved in human aging in peripheral blood mononuclear cells

Aging is an inevitable part of life for humans, and slowing down the aging process has become a main focus of human endeavor. Here, we applied a systems biology approach to construct protein-protein interaction networks, gene regulatory networks, and epigenetic networks, i.e. genetic and epigenetic networks (GENs), of elderly individuals and young controls. We then compared these GENs to extract aging mechanisms using microarray data in peripheral blood mononuclear cells, microRNA (miRNA) data, and database mining. The core GENs of elderly individuals and young controls were obtained by applying principal network projection to GENs based on Principal Component Analysis. By comparing the core networks, we identified that to overcome the accumulated mutation of genes in the aging process the transcription factor JUN can be activated by stress signals, including the MAPK signaling, T-cell receptor signaling, and neurotrophin signaling pathways through DNA methylation of BTG3, G0S2, and AP2B1 and the regulations of mir-223 let-7d, and mir-130a. We also address the aging mechanisms in old men and women. Furthermore, we proposed that drugs designed to target these DNA methylated genes or miRNAs may delay aging. A multiple drug combination comprising phenylalanine, cholesterol, and palbociclib was finally designed for delaying the aging process.

Genetic and Epigenetic Regulation of Aortic Aneurysms

Aneurysms are characterized by structural deterioration of the vascular wall leading to progressive dilatation and, potentially, rupture of the aorta. While aortic aneurysms often remain clinically silent, the morbidity and mortality associated with aneurysm expansion and rupture are considerable. Over 13,000 deaths annually in the United States are attributable to aortic aneurysm rupture with less than 1 in 3 persons with aortic aneurysm rupture surviving to surgical intervention. Environmental and epidemiologic risk factors including smoking, male gender, hypertension, older age, dyslipidemia, atherosclerosis, and family history are highly associated with abdominal aortic aneurysms, while heritable genetic mutations are commonly associated with aneurysms of the thoracic aorta. Similar to other forms of cardiovascular disease, family history, genetic variation, and heritable mutations modify the risk of aortic aneurysm formation and provide mechanistic insight into the pathogenesis of human aortic aneurysms. This review will examine the relationship between heritable genetic and epigenetic influences on thoracic and abdominal aortic aneurysm formation and rupture.

Direct Reprogramming of Mouse Fibroblasts toward Leydig-like Cells by Defined Factors

Leydig cells (LCs) play crucial roles in producing testosterone, and their dysfunction leads to male hypogonadism. LC transplantation is a promising alternative therapy for male hypogonadism. However, the source of LCs limits this strategy for clinical applications. Here, we report our success in reprogramming mice fibroblasts into LCs by expressing three transcriptional factors, Dmrt1, Gata4, and Nr5a1. The induced Leydig-like cells (iLCs) expressed steroidogenic genes, had a global gene expression profile similar to that of adult LCs, and acquired androgen synthesis capabilities. When iLCs were transplanted into rats or mice testes that were selectively depleted of endogenous LCs, the transplanted cells could survive and function in the interstitium of testis, resulting in the restoration of normal levels of serum testosterone. These findings demonstrate that the fibroblasts were able to be directly converted into iLCs by few defined factors, which may facilitate future applications in regenerative medicine.

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Direct reprogramming of fibroblasts into Leydig cell fate by defined factors

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Induced Leydig-like cells (iLCs) exhibit adult Leydig cell characterizations

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Conversion process toward iLCs did not pass through a mitotic cell state

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Transplantation of iLCs could survive and function in the interstitium of testis

Aging related methylation influences the gene expression of key control genes in colorectal cancer and adenoma

AIM

To analyze colorectal carcinogenesis and age-related DNA methylation alterations of gene sequences associated with epigenetic clock CpG sites.

METHODS

In silico DNA methylation analysis of 353 epigenetic clock CpG sites published by Steve Horvath was performed using methylation array data for a set of 123 colonic tissue samples [64 colorectal cancer (CRC), 42 adenoma, 17 normal; GEO accession number: GSE48684]. Among the differentially methylated age-related genes, secreted frizzled related protein 1 (SFRP1) promoter methylation was further investigated in colonic tissue from 8 healthy adults, 19 normal children, 20 adenoma and 8 CRC patients using bisulfite-specific PCR followed by methylation-specific high resolution melting (MS-HRM) analysis. mRNA expression of age-related “epigenetic clock” genes was studied using Affymetrix HGU133 Plus2.0 whole transcriptome data of 153 colonic biopsy samples (49 healthy adult, 49 adenoma, 49 CRC, 6 healthy children) (GEO accession numbers: GSE37364, GSE10714, GSE4183, GSE37267). Whole promoter methylation analysis of genes showing inverse DNA methylation-gene expression data was performed on 30 colonic samples using methyl capture sequencing.

RESULTS

Fifty-seven age-related CpG sites including hypermethylated PPP1R16B, SFRP1, SYNE1 and hypomethylated MGP, PIPOX were differentially methylated between CRC and normal tissues (P < 0.05, Δβ≥ 10%). In the adenoma vs normal comparison, 70 CpG sites differed significantly, including hypermethylated DKK3, SDC2, SFRP1, SYNE1 and hypomethylated CEMIP, SPATA18 (P < 0.05, Δβ≥ 10%). In MS-HRM analysis, the SFRP1 promoter region was significantly hypermethylated in CRC (55.0% ± 8.4 %) and adenoma tissue samples (49.9% ± 18.1%) compared to normal adult (5.2% ± 2.7%) and young (2.2% ± 0.7%) colonic tissue (P < 0.0001). DNA methylation of SFRP1 promoter was slightly, but significantly increased in healthy adults compared to normal young samples (P < 0.02). This correlated with significantly increased SFRP1 mRNA levels in children compared to normal adult samples (P < 0.05). In CRC tissue the mRNA expression of 117 age-related genes were changed, while in adenoma samples 102 genes showed differential expression compared with normal colonic tissue (P < 0.05, logFC > 0.5). The change of expression for several genes including SYNE1, CLEC3B, LTBP3 and SFRP1, followed the same pattern in aging and carcinogenesis, though not for all genes (e.g., MGP).

CONCLUSION

Several age-related DNA methylation alterations can be observed during CRC development and progression affecting the mRNA expression of certain CRC- and adenoma-related key control genes.

Integrative modelling of tumour DNA methylation quantifies the contribution of metabolism

Altered DNA methylation is common in cancer and often considered an early event in tumorigenesis. However, the sources of heterogeneity of DNA methylation among tumours remain poorly defined. Here we capitalize on the availability of multi-platform data on thousands of human tumours to build integrative models of DNA methylation. We quantify the contribution of clinical and molecular factors in explaining intertumoral variability in DNA methylation. We show that the levels of a set of metabolic genes involved in the methionine cycle is predictive of several features of DNA methylation in tumours, including the methylation of cancer genes. Finally, we demonstrate that patients whose DNA methylation can be predicted from the methionine cycle exhibited improved survival over cases where this regulation is disrupted. This study represents a comprehensive analysis of the determinants of methylation and demonstrates the surprisingly large interaction between metabolism and DNA methylation variation. Together, our results quantify links between tumour metabolism and epigenetics and outline clinical implications.

Altered DNA methylation is a feature of cancer and between-patient variability is prevalent. Here, the authors integrate data on thousands of human tumours, and find that expression levels of methionine metabolism genes are predictive of methylation features, and that the breakdown of this relationship is a negative prognostic marker.

Epigenetic regulation of L-type voltage-gated Ca2+ channels in mesenteric arteries of aging hypertensive rats

Accumulating evidence has shown that epigenetic regulation is involved in hypertension and aging. L-type voltage-gated Ca²⁺ channels (LTCCs), the dominant channels in vascular myocytes, greatly contribute to arteriole contraction and blood pressure (BP) control. We investigated the dynamic changes and epigenetic regulation of LTCC in the mesenteric arteries of aging hypertensive rats. LTCC function was evaluated by using microvascular rings and whole-cell patch-clamp in the mesenteric arteries of male Wistar-Kyoto rats and spontaneously hypertensive rats at established hypertension (3 month old) and an aging stage (16 month old), respectively. The expression of the LTCC α1C subunit was determined in the rat mesenteric microcirculation. The expression of miR-328, which targets α1C mRNA, and the DNA methylation status at the promoter region of the α1C gene (CACNA1C) were also determined. In vitro experiments were performed to assess α1C expression after transfection of the miR-328 mimic into cultured vascular smooth muscle cells (VSMCs). The results showed that hypertension superimposed with aging aggravated BP and vascular remodeling. Both LTCC function and expression were significantly increased in hypertensive arteries and downregulated with aging. miR-328 expression was inhibited in hypertension, but increased with aging. There was no significant difference in the mean DNA methylation of CACNA1C among groups, whereas methylation was enhanced in the hypertensive group at specific sites on a CpG island located upstream of the gene promoter. Overexpression of miR-328 inhibited the α1C level of cultured VSMCs within 48 h. The results of the present study indicate that the dysfunction of LTCCs may exert an epigenetic influence at both pre- and post-transcriptional levels during hypertension pathogenesis and aging progression. miR-328 negatively regulated LTCC expression in both aging and hypertension.

Prostate Cancer: Epigenetic Alterations, Risk Factors, and Therapy

Prostate cancer (PCa) is the most prevalent urological cancer that affects aging men in South Africa, and mechanisms underlying prostate tumorigenesis remain elusive. Research advancements in the field of PCa and epigenetics have allowed for the identification of specific alterations that occur beyond genetics but are still critically important in the pathogenesis of tumorigenesis. Anomalous epigenetic changes associated with PCa include histone modifications, DNA methylation, and noncoding miRNA. These mechanisms regulate and silence hundreds of target genes including some which are key components of cellular signalling pathways that, when perturbed, promote tumorigenesis. Elucidation of mechanisms underlying epigenetic alterations and the manner in which these mechanisms interact in regulating gene transcription in PCa are an unmet necessity that may lead to novel chemotherapeutic approaches. This will, therefore, aid in developing combination therapies that will target multiple epigenetic pathways, which can be used in conjunction with the current conventional PCa treatment.

Blood DNA methylation age is not associated with cognitive functioning in middle-aged monozygotic twins

The epigenetic clock, also known as DNA methylation age (DNAmAge), represents age-related changes of DNA methylation at multiple sites of the genome and is suggested to be a biomarker for biological age. Elevated blood DNAmAge is associated with all-cause mortality, with the strongest effects reported in a recent intrapair twin study where epigenetically older twins had increased mortality risk in comparison to their co-twins. In the study presented here, we hypothesize that DNAmAge in blood is associated with cross-sectional and longitudinal cognitive abilities in middle-aged individuals. In 486 monozygotic twins, we investigated the association of DNAmAge, difference between DNAmAge and chronological age and age acceleration with cognition. Despite using a powerful paired twin design, we found no evidence for association of blood DNAmAge with cognitive abilities. This observation was confirmed in unpaired analyses, where DNAmAge initially correlated with cognitive abilities, until adjusting for chronological age. Overall, our study shows that for middle-aged individuals DNAmAge calculated in blood does not correlate with cognitive abilities.

Prostate Cancer: Is It a Battle Lost to Age?

Age is often considered an important non-modifiable risk factor for a number of diseases, including prostate cancer. Some prominent risk factors of prostate cancer include familial history, ethnicity and age. In this review, various genetic and physiological characteristics affected due to advancing age will be analysed and correlated with their direct effect on prostate cancer.

The Molecular and Cellular Effect of Homocysteine Metabolism Imbalance on Human Health

Homocysteine (Hcy) is a sulfur-containing non-proteinogenic amino acid derived in methionine metabolism. The increased level of Hcy in plasma, hyperhomocysteinemia, is considered to be an independent risk factor for cardio and cerebrovascular diseases. However, it is still not clear if Hcy is a marker or a causative agent of diseases. More and more research data suggest that Hcy is an important indicator for overall health status. This review represents the current understanding of molecular mechanism of Hcy metabolism and its link to hyperhomocysteinemia-related pathologies in humans. The aberrant Hcy metabolism could lead to the redox imbalance and oxidative stress resulting in elevated protein, nucleic acid and carbohydrate oxidation and lipoperoxidation, products known to be involved in cytotoxicity. Additionally, we examine the role of Hcy in thiolation of proteins, which results in their molecular and functional modifications. We also highlight the relationship between the imbalance in Hcy metabolism and pathogenesis of diseases, such as cardiovascular diseases, neurological and psychiatric disorders, chronic kidney disease, bone tissue damages, gastrointestinal disorders, cancer, and congenital defects.

Methylation pattern of CDH1 promoter and its association with CDH1 gene expression in cytological cervical specimens

Cervical cancer is the fourth leading cause of cancer mortality in females worldwide. Infection with high-risk human papillomavirus (HPV) is essential but insufficient to cause cervical cancer, and the clearance of HPV infection is mediated by the immune system. The deficit of molecules responsible for adhesion may play a role in the development of cervical cancer. E-cadherin is encoded by the cadherin 1 (CDH1) gene, and is involved in cell adhesion by forming adherens junctions. The aim of present study was to investigate the methylation pattern of the CDH1 promoter and to identify the association between CDH1 promoter hypermethylation, CDH1 gene expression and HPV infection in cervical specimens obtained from 93 patients with low-grade squamous intraepithelial lesions (SILs), high-grade SILs or squamous cell carcinomas, and from 47 patients with normal cervical cytology (HPV-negative). The methylation pattern of the CDH1 promoter was investigated by methylation-specific polymerase chain reaction and quantitative pyrosequencing. CDH1 gene expression was measured by relative quantification. CDH1 methylation was significantly higher in both types of lesions and in cervical cancer than in normal samples, and CDH1 gene expression was significantly reduced during SIL progression (P=0.0162). However, the influence of HPV infection or HPV E6 expression on the methylation pattern of the CDH1 gene or its gene expression levels could not be confirmed. The present results support that the methylation of the CDH1 gene is age-related in patients with cervical lesions (P=0.01085), and therefore, older patients could be more susceptible to cancer than younger patients. The important methylation of the CDH1 promoter occurred near the transcription factor binding sites on nucleotides -13 and +103, which are close to the translational start codon. These results suggest that methylation at these sites may be an important event in the transcriptional regulation of E-cadherin, and in patients harboring these methylated cytosines, this event may facilitate HPV-driven carcinogenesis.

Methylation of LOXL1 Promoter by DNMT3A in Aged Human Skin Fibroblasts

Lysyl oxidase-like 1 (LOXL1) is an amino-oxidase involved in maturation of elastic fibers. Its downregulation has been associated with elastic fibers repair loss in aging aorta, lung, ligament, and skin. Several evidences of LOXL1 epigenetic silencing by promoter methylation were reported in cancer and cutis laxa syndrome. We hypothesized that this mechanism could be implicated in skin aging process, as far as elastic fibers are also concerned. Anti-DNMT3A chromatin immunoprecipitation was conducted with nuclear extracts from skin fibroblasts isolated from young and elderly individuals, and showed a higher level of DNMT3A protein binding to the LOXL1 promoter in older cells concomitantly to the decrease of LOXL1 mRNA expression and the increase of LOXL1 promoter methylation. Using luciferase reporter assay driven by LOXL1 promoter in HEK293 cells, we demonstrated that LOXL1 transcriptional activity was dramatically reduced when a recombinant DNMT3A was concomitantly overexpressed. LOXL1 promoter transcriptional activity was restored in the presence of a broad-spectrum inhibitor of DNMT activity, 5-aza-2'-deoxycytidine. Finally, to assess whether the interplay between DNMT3A and LOXL1 promoter could be targeted to increase LOXL1 mRNA expression level, an Origanum majorana extract was selected among 43 plant extracts as a new inhibitor of human DNMT3A activity to restore LOXL1 secretion without cytotoxicity in aged skin fibroblasts.

Association between reduced white matter integrity in the corpus callosum and serotonin transporter gene DNA methylation in medication-naive patients with major depressive disorder

Previous evidence suggests that the serotonin transporter gene (SLC6A4) is associated with the structure of brain regions that are critically involved in dysfunctional limbic-cortical network activity associated with major depressive disorder (MDD). Diffusion tensor imaging (DTI) and tract-based spatial statistics were used to investigate changes in white matter integrity in patients with MDD compared with healthy controls. A possible association between structural alterations in white matter tracts and DNA methylation of the SLC6A4 promoter region was also assessed. Thirty-five medication-naive patients with MDD (mean age: 40.34, male/female: 10/25) and age, gender and education level matched 49 healthy controls (mean age: 41.12, male/female: 15/34) underwent DTI. SLC6A4 DNA methylation was also measured at five CpG sites of the promoter region, and the cell type used was whole-blood DNA. Patients with MDD had significantly lower fractional anisotropy (FA) values for the genu of the corpus callosum and body of the corpus callosum than that in healthy controls (family-wise error corrected, P<0.01). Significant inverse correlations were observed between SLC6A4 DNA methylation and FA (CpG3, Pearson's correlation: r=-0.493, P=0.003) and axial diffusivity (CpG3, Pearson's correlation: r=-0.478, P=0.004) values of the body of the corpus callosum in patients with MDD. These results contribute to evidence indicating an association between epigenetic gene regulation and structural brain alterations in depression. Moreover, we believe this is the first report of a correlation between DNA methylation of the SLC6A4 promoter region and white matter integrity in patients with MDD.

Comparison of pre-processing methodologies for Illumina 450k methylation array data in familial analyses

Background

Human methylome mapping in health and disease states has largely relied on Illumina Human Methylation 450k array (450k array) technology. Accompanying this has been the necessary evolution of analysis pipelines to facilitate data processing. The majority of these pipelines, however, cater for experimental designs where matched ‘controls’ or ‘normal’ samples are available. Experimental designs where no appropriate ‘reference’ exists remain challenging. Herein, we use data generated from our study of the inheritance of methylome profiles in families to evaluate the performance of eight normalisation pre-processing methods. Fifty individual samples representing four families were interrogated on five 450k array BeadChips. Eight normalisation methods were tested using qualitative and quantitative metrics, to assess efficacy and suitability.

Results

Stratified quantile normalisation combined with ComBat were consistently found to be the most appropriate when assessed using density, MDS and cluster plots. This was supported quantitatively by ANOVA on the first principal component where the effect of batch dropped from p < 0.01 to p = 0.97 after stratified QN and ComBat. Median absolute differences between replicated samples were the lowest after stratified QN and ComBat as were the standard error measures on known imprinted regions. Biological information was preserved after normalisation as indicated by the maintenance of a significant association between a known mQTL and methylation (p = 1.05e-05).

Conclusions

A strategy combining stratified QN with ComBat is appropriate for use in the analyses when no reference sample is available but preservation of biological variation is paramount. There is great potential for use of 450k array data to further our understanding of the methylome in a variety of similar settings. Such advances will be reliant on the determination of appropriate methodologies for processing these data such as established here.

Electronic supplementary material

The online version of this article (doi:10.1186/s13148-016-0241-2) contains supplementary material, which is available to authorized users.

Epigenetics and aging

Over the past decade, a growing number of studies have revealed that progressive changes to epigenetic information accompany aging in both dividing and nondividing cells. Functional studies in model organisms and humans indicate that epigenetic changes have a huge influence on the aging process. These epigenetic changes occur at various levels, including reduced bulk levels of the core histones, altered patterns of histone posttranslational modifications and DNA methylation, replacement of canonical histones with histone variants, and altered noncoding RNA expression, during both organismal aging and replicative senescence. The end result of epigenetic changes during aging is altered local accessibility to the genetic material, leading to aberrant gene expression, reactivation of transposable elements, and genomic instability. Strikingly, certain types of epigenetic information can function in a transgenerational manner to influence the life span of the offspring. Several important conclusions emerge from these studies: rather than being genetically predetermined, our life span is largely epigenetically determined; diet and other environmental influences can influence our life span by changing the epigenetic information; and inhibitors of epigenetic enzymes can influence life span of model organisms. These new findings provide better understanding of the mechanisms involved in aging. Given the reversible nature of epigenetic information, these studies highlight exciting avenues for therapeutic intervention in aging and age-associated diseases, including cancer.

Epigenetic perturbations in aging stem cells

Stem cells maintain homeostasis in all regenerating tissues during the lifespan of an organism. Thus, age-related functional decline of such tissues is likely to be at least partially explained by molecular events occurring in the stem cell compartment. Some of these events involve epigenetic changes, which may dictate how an aging genome can lead to differential gene expression programs. Recent technological advances have made it now possible to assess the genome-wide distribution of an ever-increasing number of epigenetic marks. As a result, the hypothesis that there may be a causal role for an altered epigenome contributing to the functional decline of cells, tissues, and organs in aging organisms can now be explored. In this paper, we review recent developments in the field of epigenetic regulation of stem cells, and how this may contribute to aging.

Host Resistance and Immune Aging

Human immune system aging results in impaired responses to pathogens or vaccines. In the innate immune system, which mediates the earliest pro-inflammatory responses to immunologic challenge, processes ranging from Toll-like Receptor function to Neutrophil Extracellular Trap formation are generally diminished in older adults. Dysregulated, enhanced basal inflammation with age reflecting activation by endogenous damage-associated ligands contributes to impaired innate immune responses. In the adaptive immune system, T and B cell subsets and function alter with age. The control of cytomegalovirus infection, particularly in the T lineage, plays a dominant role in the differentiation and diversity of the T cell compartment.

Transgenerational epigenetic inheritance in mammals: how good is the evidence?

Epigenetics plays an important role in orchestrating key biologic processes. Epigenetic marks, including DNA methylation, histones, chromatin structure, and noncoding RNAs, are modified throughout life in response to environmental and behavioral influences. With each new generation, DNA methylation patterns are erased in gametes and reset after fertilization, probably to prevent these epigenetic marks from being transferred from parents to their offspring. However, some recent animal studies suggest an apparent resistance to complete erasure of epigenetic marks during early development, enabling transgenerational epigenetic inheritance. Whether there are similar mechanisms in humans remains unclear, with the exception of epigenetic imprinting. Nevertheless, a distinctly different mechanism-namely, intrauterine exposure to environmental stressors that may affect establishment of the newly composing epigenetic patterns after fertilization-is often confused with transgenerational epigenetic inheritance. In this review, we delineate the definition of and requirement for transgenerational epigenetic inheritance, differentiate it from the consequences of intrauterine exposure, and discuss the available evidence in both animal models and humans.-Van Otterdijk, S. D., Michels, K. B. Transgenerational epigenetic inheritance in mammals: how good is the evidence?

Contributions of Nonhuman Primates to Research on Aging

Aging is the biological process of declining physiologic function associated with increasing mortality rate during advancing age. Humans and higher nonhuman primates exhibit unusually longer average life spans as compared with mammals of similar body mass. Furthermore, the population of humans worldwide is growing older as a result of improvements in public health, social services, and health care systems. Comparative studies among a wide range of organisms that include nonhuman primates contribute greatly to our understanding about the basic mechanisms of aging. Based on their genetic and physiologic relatedness to humans, nonhuman primates are especially important for better understanding processes of aging unique to primates, as well as for testing intervention strategies to improve healthy aging and to treat diseases and disabilities in older people. Rhesus and cynomolgus macaques are the predominant monkeys used in studies on aging, but research with lower nonhuman primate species is increasing. One of the priority topics of research about aging in nonhuman primates involves neurologic changes associated with cognitive decline and neurodegenerative diseases. Additional areas of research include osteoporosis, reproductive decline, caloric restriction, and their mimetics, as well as immune senescence and chronic inflammation that affect vaccine efficacy and resistance to infections and cancer. The purpose of this review is to highlight the findings from nonhuman primate research that contribute to our understanding about aging and health span in humans.

Frailty is associated with the epigenetic clock but not with telomere length in a German cohort

Background

The epigenetic clock, in particular epigenetic pre-aging quantified by the so-called DNA methylation age acceleration, has recently been suggested to closely correlate with a variety of disease phenotypes. There remains a dearth of data, however, on its association with telomere length and frailty, which can be considered major correlates of age on the genomic and clinical level, respectively.

Results

In this cross-sectional observational study on altogether 1820 subjects from two subsets (n = 969 and n = 851; mean ± standard deviation age 62.1 ± 6.5 and 63.0 ± 6.7 years, respectively) of the ESTHER cohort study of the elderly general population in Germany, DNA methylation age was calculated based on a 353 loci predictor previously developed in a large meta-study, and the difference-based epigenetic age acceleration was calculated as predicted methylation age minus chronological age. No correlation of epigenetic age acceleration with telomere length was found in our study (p = 0.63). However, there was an association of DNA methylation age acceleration with a comprehensive frailty measure, such that the accumulated deficits significantly increased with increasing age acceleration. Quantitatively, about half an additional deficit was added per 6 years of methylation age acceleration (p = 0.0004). This association was independent from age, sex, and estimated leukocyte distribution, as well as from a variety of other confounding variables considered.

Conclusions

The results of the present study suggest that epigenetic age acceleration is correlated with clinically relevant aging-related phenotypes through pathways unrelated to cellular senescence as assessed by telomere length. Innovative approaches like Mendelian randomization will be needed to elucidate whether epigenetic age acceleration indeed plays a causal role for the development of clinical phenotypes.

Electronic supplementary material

The online version of this article (doi:10.1186/s13148-016-0186-5) contains supplementary material, which is available to authorized users.

Aging and computational systems biology

Aging research is undergoing a paradigm shift, which has led to new and innovative methods of exploring this complex phenomenon. The systems biology approach endeavors to understand biological systems in a holistic manner, by taking account of intrinsic interactions, while also attempting to account for the impact of external inputs, such as diet. A key technique employed in systems biology is computational modeling, which involves mathematically describing and simulating the dynamics of biological systems. Although a large number of computational models have been developed in recent years, these models have focused on various discrete components of the aging process, and to date no model has succeeded in completely representing the full scope of aging. Combining existing models or developing new models may help to address this need and in so doing could help achieve an improved understanding of the intrinsic mechanisms which underpin aging.

Accelerated epigenetic aging in brain is associated with pre-mortem HIV-associated neurocognitive disorders

HIV infection leads to age-related conditions in relatively young persons. HIV-associated neurocognitive disorders (HAND) are considered among the most prevalent of these conditions. To study the mechanisms underlying this disorder, researchers need an accurate method for measuring biological aging. Here, we apply a recently developed measure of biological aging, based on DNA methylation, to the study of biological aging in HIV+ brains. Retrospective analysis of tissue bank specimens and pre-mortem data was carried out. Fifty-eight HIV+ adults underwent a medical and neurocognitive evaluation within 1 year of death. DNA was obtained from occipital cortex and analyzed with the Illumina Infinium Human Methylation 450K platform. Biological age determined via the epigenetic clock was contrasted with chronological age to obtain a measure of age acceleration, which was then compared between those with HAND and neurocognitively normal individuals. The HAND and neurocognitively normal groups did not differ with regard to demographic, histologic, neuropathologic, or virologic variables. HAND was associated with accelerated aging relative to neurocognitively normal individuals, with average relative acceleration of 3.5 years. Age acceleration did not correlate with pre-mortem neurocognitive functioning or HAND severity. This is the first study to demonstrate that the epigenetic age of occipital cortex samples is associated with HAND status in HIV+ individuals pre-mortem. While these results suggest that the increased risk of a neurocognitive disorder due to HIV might be mediated by an epigenetic aging mechanism, future studies will be needed to validate the findings and dissect causal relationships and downstream effects.

Does reducing gamete co-incubation time improve clinical outcomes: a retrospective study

PURPOSE

The objective of this retrospective study was to determine whether patients undergoing in vitro fertilization (IVF) benefit from reducing the gamete co-incubation time.

METHODS

Patients (n = 570) were enrolled, including 281 patients in the reduced incubation time group (2-h incubation) and 289 patients in the standard IVF group (18-h incubation).

RESULTS

The observed outcomes, including the clinical pregnancy rate (CPR), implantation rate (IR), live birth rate (LBR), and miscarriage rate (MR), were similar between the two groups. When the data were divided into two subgroups based on the maternal age (≤30 and >30 years), the rates of top-quality embryos (30.83 vs. 25.89 %; p = 0.028), CPR (66.67 vs. 42.11 %; p = 0.013), and IR (41.90 vs. 31.25 %, p = 0.019) of the 2-h incubation group were significantly higher in the younger subgroup. However, for older patients, only a lower MR (7.59 vs. 20.83 %; p = 0.019) was achieved. Reducing the time of incubation still improved the CPR (OR = 1.993, 95 % CI 1.141-3.480) and MR (OR = 3.173, 95 % CI 1.013-9.936) in the younger and older subgroups, respectively, after it was adjusted for potential confounders.

CONCLUSIONS

Reducing incubation time improves the clinical results of IVF, although the LBR is not statistically different between the 2- and 18-h incubation time groups. And the specific clinical outcomes of reducing incubation time varied between the >30-year-old and the ≤30-year-old.