Extensive analysis of mitochondrial DNA quantity and sequence variation in human cumulus cells and assisted reproduction outcomes.

STUDY QUESTION: Are relative mitochondrial DNA (mtDNA) content and mitochondrial genome (mtGenome) variants in human cumulus cells (CCs) associated with oocyte reproductive potential and assisted reproductive technology (ART) outcomes? SUMMARY ANSWER: Neither the CC mtDNA quantity nor the presence of specific mtDNA genetic variants was associated with ART outcomes, although associations with patient body mass index (BMI) were detected, and the total number of oocytes retrieved differed between major mitochondrial haplogroups. WHAT IS KNOWN ALREADY: CCs fulfil a vital role in the support of oocyte developmental competence. As with other cell types, appropriate cellular function is likely to rely upon adequate energy production, which in turn depends on the quantity and genetic competence of the mitochondria. mtDNA mutations can be inherited or they can accumulate in somatic cells over time, potentially contributing to aging. Such mutations may be homoplasmic (affecting all mtDNA in a cell) or they may display varying levels of heteroplasmy (affecting a proportion of the mtDNA). Currently, little is known concerning variation in CC mitochondrial genetics and how this might influence the reproductive potential of the associated oocyte. STUDY DESIGN, SIZE, DURATION: This was a prospective observational study involving human CCs collected with 541 oocytes from 177 IVF patients. mtDNA quantity was measured in all the samples with a validated quantitative PCR method and the entire mtGenome was sequenced in a subset of 138 samples using a high-depth massively parallel sequencing approach. Associations between relative mtDNA quantity and mtGenome variants in CCs and patient age, BMI (kg/m2), infertility diagnosis and ART outcomes were investigated. PARTICIPANTS/MATERIALS, SETTING, METHODS: Massively parallel sequencing permitted not only the accurate detection of mutations but also the precise quantification of levels of mutations in cases of heteroplasmy. Sequence variants in the mtDNA were evaluated using Mitomaster and HmtVar to predict their potential impact. MAIN RESULTS AND THE ROLE OF CHANCE: The relative mtDNA CC content was significantly associated with BMI. No significant associations were observed between CC mtDNA quantity and patient age, female infertility diagnosis or any ART outcome variable. mtGenome sequencing revealed 4181 genetic variants with respect to a reference genome. The COXI locus contained the least number of coding sequence variants, whereas ATPase8 had the most. The number of variants predicted to affect the ATP production differed significantly between mitochondrial macrohaplogroups. The total number of retrieved oocytes was different between the H-V and J-T as well as the U-K and J-T macrohaplogroups. There was a non-significant increase in mtDNA levels in CCs with heteroplasmic mitochondrial mutations. LARGE SCALE DATA: N/A. LIMITATIONS, REASONS FOR CAUTION: Although a large number of samples were analysed in this study, it was not possible to analyse all the CCs from every patient. Also, the results obtained with respect to specific clinical outcomes and macrohaplogroups should be interpreted with caution due to the smaller sample sizes when subdividing the dataset. WIDER IMPLICATIONS OF THE FINDINGS: These findings suggest that the analysis of mtDNA in CCs is unlikely to provide an advantage in terms of improved embryo selection during assisted reproduction cycles. Nonetheless, our data raise interesting biological questions, particularly regarding the interplay of metabolism and BMI and the association of mtDNA haplogroup with oocyte yield in ovarian stimulation cycles. STUDY FUNDING/COMPETING INTEREST(S): This study was funded by National Institutes of Health grant 5R01HD092550-02. D.J.N. and C.R. co-hold patent US20150346100A1 and D.J.N. holds US20170039415A1, both for metabolic imaging methods. D.W. receives support from the NIHR Oxford Biomedical Research Centre. The remaining authors have no conflicts of interest to declare.

Metabolic imaging of human cumulus cells reveals associations among metabolic profiles of cumulus cells, patient clinical factors, and oocyte maturity.

OBJECTIVE: To determine whether fluorescence lifetime imaging microscopy (FLIM) detects differences in metabolic state among cumulus cell samples and whether their metabolic state is associated with patient age, body mass index (BMI), and antimüllerian hormone (AMH) level and maturity of the oocyte. DESIGN: Prospective observational study. SETTING: Academic laboratory. PATIENT(S): Cumulus cell (CC) clusters from cumulus-oocyte complexes were collected from patients undergoing assisted reproductive technology treatment after oocyte retrieval and vitrified. INTERVENTION(S): Cumulus cell metabolism was assessed using FLIM to measure autofluorescence of nicotinamide adenine (phosphate) dinucleotide and flavine adenine dinucleotide, endogenous coenzymes essential for cellular respiration and glycolysis. Patient age, BMI, and AMH level and the maturity of the corresponding oocytes were recorded. MAIN OUTCOME MEASURE(S): Quantitative information from FLIM was obtained regarding metabolite concentrations from fluorescence intensity and metabolite enzyme engagement from fluorescence lifetimes. Associations were investigated between each FLIM parameter and oocyte maturity and patient age, BMI, and AMH. Variance between CC clusters within and between patients was determined. RESULT(S): Of 619 CC clusters from 193 patients, 90 were associated with immature oocytes and 505 with metaphase II oocytes. FLIM enabled quantitative measurements of the metabolic state of CC clusters. These parameters were significantly correlated with patient age and AMH independently, but not with BMI. Cumulus cell nicotinamide adenine (phosphate) dinucleotide FLIM parameters and redox ratio were significantly associated with maturity of the enclosed oocyte. CONCLUSION(S): FLIM detects variations in the metabolic state of CCs, showing a greater variance among clusters from each patient than between patients. Fluorescence lifetime imaging microscopy can detect CC metabolic associations with patient age and AMH and variations between mature and immature oocytes, suggesting the potential utility of this technique to help identify superior oocytes.

Identification of circulating small non-coding RNAs in relation to male subfertility and reproductive hormones.

Male subfertility is often associated with sub-optimal health status and traditional semen and hormone analysis reveal only limited information about the reduced fertility potential. Circulating small non-coding RNAs (sncRNAs) are paracrine and endocrine messengers, with prognostic potential. Here, we utilised small RNA-Seq to identify novel cell-free circulating sncRNAs that could act as potential biomarkers of male subfertility. We analysed sera from twelve subfertile men and four controls. The subfertile men were further sub-divided into the three groups based on reproductive hormone levels: group 1 (n = 4): hormone levels similar to the controls, group 2 (n = 4) showing elevated FSH levels, and group 3 (n = 4) with low total testosterone (TT). Total RNA was extracted from serum and sequenced to identify miRNAs and piRNAs. Selected sncRNAs were qPCR validated in a larger and independent cohort of subfertile men (n = 57) and normozoospermic controls (n = 19). RNA-Seq resulted in the identification of 1123 and 330 circulating miRNAs and piRNAs, respectively. Several miRNAs and piRNAs were differentially (p = 0.05) present between controls and subfertile men. Subfertile men with low TT appeared to have a distinct sncRNA profile, compared to group 1 and 2. Validation of two miRNAs (hsa-miR-542-5p and hsa-let-7i-3p) and one piRNA (hsa-piR-26399) in an independent cohort confirmed a significant difference in circulating levels between subfertile and control men. Enrichment analysis of the putative miRNA targets showed association with steroid biosynthesis pathway highlighting a potential regulatory role of these miRNAs. We propose that circulating sncRNAs may represent new important functional biomarkers in male reproductive endocrinology.

The paternal genome and the health of the assisted reproductive technology child.

As a number of children born by assisted reproductive technology (ART) are increasing each year across the developed world, the health of such offspring is a matter of public concern. Does the integrity of the paternal genome impact on offspring health? In societal terms, as birth rates fall, and the Western population become unsustainable, do the benefits outweigh the costs of creating and providing for this ART conceived subpopulation? There are little data to date to answer these questions. The long-term health of such children has largely been ignored, and success measured only by early (prebirth) outcomes such as embryo quality or pregnancy. However, there are powerful paradigms such as ageing and smoking that give vital clues as to the potential impact of unhealthy spermatozoa on disease risk, mental and physical health, fertility and mortality of these offspring.

Novel insights into the genetic and epigenetic paternal contribution to the human embryo.

The integrity of the sperm genome and epigenome are critical for normal embryonic development. The advent of assisted reproductive technology has led to an increased understanding of the role of sperm in fertilization and embryogenesis. During fertilization, the sperm transmits not only nuclear DNA to the oocyte but also activation factor, centrosomes, and a host of messenger RNA and microRNAs. This complex complement of microRNAs and other non-coding RNAs is believed to modify important post-fertilization events. Thus, the health of the sperm genome and epigenome is critical for improving assisted conception rates and the birth of healthy offspring.

Novel insights into the genetic and epigenetic paternal contribution to the human embryo

The integrity of the sperm genome and epigenome are critical for normal embryonic development. The advent of assisted reproductive technology has led to an increased understanding of the role of sperm in fertilization and embryogenesis. During fertilization, the sperm transmits not only nuclear DNA to the oocyte but also activation factor, centrosomes, and a host of messenger RNA and microRNAs. This complex complement of microRNAs and other non-coding RNAs is believed to modify important post-fertilization events. Thus, the health of the sperm genome and epigenome is critical for improving assisted conception rates and the birth of healthy offspring.

Predictive value of DNA integrity analysis in idiopathic recurrent pregnancy loss following spontaneous conception.

PURPOSE: Standard semen parameters are poor predictors of fertility potential. To date, apart from, paternal karyotyping sperm factors are not evaluated in recurrent pregnancy loss (RPL), only recent studies have emphasized the role of sperm factors in early embryonic development as sperm transcribes genes critical for early embryonic development. Sperm DNA integrity is useful diagnostic and prognostic marker and has clinical implications in idiopathic recurrent pregnancy loss (iRPL) following spontaneous conception. The aim of this study was to assess DNA integrity in cases experiencing iRPL following spontaneous conception. METHODS: Semen samples from 45 patients and 20 controls were analyzed as per WHO 1999 guidelines and sperm chromatin structure assay (SCSA) was used to measure DNA fragmentation index (DFI). RESULTS: By applying receiver operating curve (ROC) analysis, sperm DFI of approximately 26 % was found in male partner of couples experiencing iRPL. CONCLUSIONS: Our data indicate that sperm from men with a history of iRPL have a higher percentage of DNA damage as compared to control group, and this can explain pregnancy loss in these patients. Men with higher DFI are infertile whereas men with lower DFI (26 %) are able to conceive but experience recurrent pregnancy loss. Thus it is important to evaluate sperm DFI in couples experiencing iRPL to understand exact aetiology of RPL and determine prognosis and management.

PAX6 gene analysis in irido-fundal coloboma.

PURPOSE: To screen the paired box gene 6 (PAX6) gene in irido-fundal coloboma. METHODS: The entire coding region of PAX6 including intron-exon boundaries was amplified from cases (n=30) and controls (n=30). All sequences were analyzed against the ensemble sequence (ENSG00000007372) for PAX6. RESULTS: DNA sequence analysis of patients and controls revealed a total of three nucleotide changes (g.31815391Cytosine>Thymine; Glycine72Glycine and g.31812215Thymine>Guanine) of which one was neutral/synonymous change and the remaining two were intronic changes. Of these 3 changes, 2 were novel and one was already reported change. All these changes were non-pathogenic, according to in silico analysis. CONCLUSIONS: In our study no pathogenic PAX6 mutation were identified. This suggests involvement of other coloboma genes. This study expands the SNP spectrum of PAX6, only rare variations which are not causative have been found. Since this is a pilot study in the north Indian population, results should be confirmed in different populations by similar studies. Familial cases are required for determining the underlying genetic loci accounting for this clinical phenotype and may lead to better understanding of disease pathogenesis.

Idiopathic recurrent pregnancy loss: role of paternal factors; a pilot study.

BACKGROUND: This case-control study was designed with the aim of evaluating the role of sperm, oxidative stress and DNA damage in idiopathic recurrent pregnancy loss (iRPL). This pilot study is the first study done on the Indian population which reports the association between DFI, TAC and ROS in couples experiencing iRSA. METHODS: Twenty infertile men with a history of iRPL and 20 fertile controls (having fathered a child a year earlier) were included in the study which was performed in Laboratory for Molecular Reproduction and Genetics, India, from March 2010 to July 2011. The female partners of the participants were normal on gynaecological examination and had normal endocrine and blood profiles. Conventional semen analysis was performed (concentration, motility, morphology; WHO criteria, 2010) within 1 hour of sample collection. Levels of reactive oxygen species (ROS) were assessed by luminol-dependant chemiluminescence. The total antioxidant capacity (TAC) was quantified by ELISA. The Sperm chromatin structure assay (SCSA) was performed by flow cytometry to determine DNA fragmentation Index (DFI). Statistical analysis was performed using SPSS version 15 and parameters were compared by Mann-Whitney test. Pearson correlation test was used to find the correlation between parameters and a p-value <0.05 was considered significant. Receiver operating characteristics (ROC) curve analysis was applied to find out the cut-off value of DNA fragmentation index. RESULTS: No significant differences in age, seminal volume, liquefaction time, pH and sperm concentration were observed between the male partner of iRPL cases and the controls, but sperm morphology and motility were significantly (p <0.05) lower in the male partner of cases with idiopathic recurrent spontaneous abortion (RSA). The mean ROS levels observed were 47427.00 relative light unit (RLU)/min/20 million sperm in the male partners as compared to 13644.57 RLU/ min/20 million sperm in the controls (normal <15000 RLU/min/20 million). The mean TAC levels in the controls (6.95 mM trolox) were significantly (p <0.05) higher as compared to the male partners of women with IRPL (2.98 mM trolox). The average mean DFI of male partners were found to be 23.37±9.9 and the mean DFI of controls was 13.89±5.40. The mean DFI was significantly (p <0.05) higher when compared to the controls. The range of DFI in male partners was 8.50-44.07. However, in the controls the range was 7.70-23.50. CONCLUSION: Sperm DNA integrity is critical for normal embryonic development and birth of healthy offspring. Oxidative stress due to the imbalance between raised free radical levels and low total antioxidant capacity is one of the critical causes of DNA damage. Thus assay of oxidative stress and sperm genomic integrity is essential in couples with iRSA following natural and spontaneous conception.

DAZL 260A > G and MTHFR 677C > T variants in sperm DNA of infertile Indian men.

DAZL (deleted in azoospermia-like) 260A > G and MTHFR (methylene tetrahydrofolate reductase) 677C > T are two important autosomal variants associated with impaired spermatogenesis. In this study, we investigated DAZL 260A > G and MTHFR 677C > T variants in sperm DNA and their frequency in oligozoospermic infertile men of Indian origin. The study on sperm DNA was performed, since it is more prone to oxidative stress-induced damage and mutation. One hundred oligozoopsermic infertile men having normal chromosomal complement with intact Y chromosome and 100 age- and ethnically-matched fertile controls were investigated for these variants in their sperm genome. Spermatozoa were separated by gradient centrifugation and DNA was isolated and analyzed for the single nucleotide polymorphisms (SNPs) by polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP). The results showed no significant differences in the frequency of DAZL AG (P = 0.58) and MTHFR CT (P = 0.44) between oligozoospermic infertile men and controls. However, 8% (8/100) oligozoospermic infertile men harbored both the variants and showed significantly (P < 0.0001) lower sperm count (3.28 +/- 1.1 vs 12.50 +/- 4.09) compared to infertile men with either of the single variant. None of the fertile controls showed the presence of the both variants. In conclusion, the combined effect of both DAZL 260A > G and MTHFR 677C > T variants may have role in compromised sperm count. However, further studies are required to find the pathological role of these combined variants in male infertility.