VEGFA splicing: divergent isoforms regulate spermatogonial stem cell maintenance.

Despite being well-known for regulating angiogenesis in both normal and tumorigenic environments, vascular endothelial growth factor A (VEGFA) has been recently implicated in male fertility, namely in the maintenance of spermatogonial stem cells (SSC). The VEGFA gene can be spliced into multiple distinct isoforms that are either angiogenic or antiangiogenic in nature. Although studies have demonstrated the alternative splicing of VEGFA, including the divergent roles of the two isoform family types, many investigations do not differentiate between them. Data concerning VEGFA in the mammalian testis are limited, but the various angiogenic isoforms appear to promote seminiferous cord formation and to form a gradient across which cells may migrate. Treatment with either antiangiogenic isoforms of VEGFA or with inhibitors to angiogenic signaling impair these processes. Serendipitously, expression of KDR, the primary receptor for both types of VEGFA isoforms, was observed on male germ cells. These findings led to further investigation of the way that VEGFA elicits avascular functions within testes. Following treatment of donor perinatal male mice with either antiangiogenic VEGFA165b or angiogenic VEGFA164 isoforms, seminiferous tubules were less colonized following transplantation with cells from VEGFA165b-treated donors. Thus, VEGFA165b and possibly other antiangiogenic isoforms of VEGFA reduce SSC number either by promoting premature differentiation, inducing cell death, or by preventing SSC formation. Thus, angiogenic isoforms of VEGFA are hypothesized to promote SSC self-renewal, and the divergent isoforms are thought to balance one another to maintain SSC homeostasis in vivo.

Loss of vascular endothelial growth factor A (VEGFA) isoforms in granulosa cells using pDmrt-1-Cre or Amhr2-Cre reduces fertility by arresting follicular development and by reducing litter size in female mice.

Because VEGFA has been implicated in follicle development, the objective of this study was to determine the effects of granulosa- and germ cell-specific VEGFA loss on ovarian morphogenesis, function, and female fertility. pDmrt1-Cre mice were mated to floxed VEGFA mice to develop granulosa-/germ cell-specific knockouts (pDmrt1-Cre;Vegfa-/-). The time from mating to first parturition was increased when pDmrt1-Cre;Vegfa-/- females were mated to control males (P = 0.0008) and tended to be longer for heterozygous females (P < 0.07). Litter size was reduced for pDmrt1-Cre;Vegfa-/- females (P < 0.007). The time between the first and second parturitions was also increased for heterozygous females (P < 0.04) and tended to be increased for pDmrt1-Cre;Vegfa-/- females (P < 0.07). pDmrt1-Cre;Vegfa-/- females had smaller ovaries (P < 0.04), reduced plasma estradiol (P < 0.007), fewer developing follicles (P < 0.008) and tended to have fewer corpora lutea (P < 0.08). Expression of Igf1r was reduced (P < 0.05); expression of Foxo3a tended to be increased (P < 0.06); and both Fshr (P < 0.1) and Sirt6 tended to be reduced (P < 0.06) in pDmrt1-Cre;Vegfa-/- ovaries. To compare VEGFA knockouts, we generated Amhr2-Cre;Vegfa-/- mice that required more time from mating to first parturition (P < 0.003) with variable ovarian size. Both lines had more apoptotic granulosa cells, and vascular staining did not appear different. Taken together these data indicate that the loss of all VEGFA isoforms in granulosa/germ cells (proangiogenic and antiangiogenic) causes subfertility by arresting follicular development, resulting in reduced ovulation rate and fewer pups per litter.

Progressive obesity alters the steroidogenic response to ovulatory stimulation and increases the abundance of mRNAs stored in the ovulated oocyte.

Obese women who are able to attain pregnancy are at increased risk for early-pregnancy loss due, in part, to reduced oocyte quality. We and others have demonstrated that female Lethal Yellow (LY) mice and female C57BL/6 mice fed a high fat diet (B6-HFD) exhibit phenotypes consistent with human obesity. These studies also showed that zygotes collected from LY and B6-HFD females have reduced developmental competence. The current hypothesis is that LY and B6-HFD females exhibit an abnormal response to gonadotropin stimulation compared to C57BL/6 controls fed normal rodent chow (B6-ND), resulting in the ovulation of oocytes with an altered molecular phenotype which may contribute to its reduced developmental competence. To test this hypothesis, age-matched B6-ND, B6-HFD, and LY females were stimulated with exogenous gonadotropins, then circulating hormone levels and the phenotypes of ovulated oocytes were analyzed. There was no difference in ovulation rate or in the percentage of morphologically abnormal oocytes collected from the oviduct of any females. Progesterone and progesterone/estradiol ratios, however, were increased in B6-HFD and LY compared to B6-ND females 16 hr post-human chorionic gonadotropin treatment. The transcript abundance of several candidate oocyte genes was also increased in B6-HFD- and LY-derived oocytes compared to B6-ND-derived oocytes. These data suggest that increased insulin and leptin levels of obese females elevated circulating progesterone concentrations, altered transcriptional activity during oocyte growth, and/or impaired mechanisms of RNA translation and degradation during oocyte maturation. These changes in mRNA abundance likely contribute to reduced oocyte quality and the subsequent poor embryogenesis associated with obesity.

Loss of vascular endothelial growth factor A (VEGFA) isoforms in the testes of male mice causes subfertility, reduces sperm numbers, and alters expression of genes that regulate undifferentiated spermatogonia.

Vascular endothelial growth factor A (VEGFA) isoform treatment has been demonstrated to alter spermatogonial stem cell homeostasis. Therefore, we generated pDmrt1-Cre;Vegfa(-/-) (knockout, KO) mice by crossing pDmrt1-Cre mice to floxed Vegfa mice to test whether loss of all VEGFA isoforms in Sertoli and germ cells would impair spermatogenesis. When first mated, KO males took 14 days longer to get control females pregnant (P < .02) and tended to take longer for all subsequent parturition intervals (9 days; P < .07). Heterozygous males sired fewer pups per litter (P < .03) and after the first litter took 10 days longer (P < .05) to impregnate females, suggesting a more progressive loss of fertility. Reproductive organs were collected from 6-month-old male mice. There were fewer sperm per tubule in the corpus epididymides (P < .001) and fewer ZBTB16-stained undifferentiated spermatogonia (P < .003) in the testes of KO males. Testicular mRNA abundance for Bcl2 (P < .02), Bcl2:Bax (P < .02), Neurog3 (P < .007), and Ret was greater (P = .0005), tended to be greater for Sin3a and tended to be reduced for total Foxo1 (P < .07) in KO males. Immunofluorescence for CD31 and VE-Cadherin showed no differences in testis vasculature; however, CD31-positive staining was evident in undifferentiated spermatogonia only in KO testes. Therefore, loss of VEGFA isoforms in Sertoli and germ cells alters genes necessary for long-term maintenance of undifferentiated spermatogonia, ultimately reducing sperm numbers and resulting in subfertility.

KDR-LacZ-expressing cells are involved in ovarian and testis-specific vascular development, suggesting a role for VEGFA in the regulation of this vasculature.

Our objectives were to evaluate kinase insert domain protein receptor (KDR)-ß-galactosidase (LacZ) expression as a marker for vascular development during gonadal morphogenesis and to determine whether any novel non-angiogenic KDR-LacZ expression was present in mouse testes or ovaries. Gonads were collected from mice expressing LacZ driven by the Kdr promoter (KDR-LacZ) from embryonic day 11 (E11) through postnatal day 60 (P60). At E11.5, mesonephric cells expressing KDR-LacZ seemed to migrate into the developing testis and surrounded developing seminiferous cords. Cells expressing KDR-LacZ appeared in the ovary with no apparent migration from the adjacent mesonephros, suggesting a different origin of endothelial cells. Testis organ cultures from E11 mice were treated with 8 µM VEGFR-TKI, a vascular endothelial growth factor A signal transduction inhibitor; subsequently, the amount of KDR-LacZ staining was reduced by 66%-99% (P<0.002), and the ability of KDR-expressing cells to form a densely organized vascular network was inhibited. Novel non-angiogenic KDR-LacZ staining was detected in the testis on specific subsets of germ cells at E16, E17, P4, P20, P30, and P60. In ovaries, staining was present on oocytes within oocyte cysts at E17 and within late secondary follicles of postnatal mice. Thus, KDR is an excellent marker for analyzing vascular development in the gonads. Inhibition of VEGFA signal transduction prevents the development of testis-specific vasculature. Furthermore, non-vascular KDR-LacZ staining suggests that KDR directly affects both spermatogenesis and somatic-oocyte interactions during gametogenesis.

FAS and FASLG polymorphisms and susceptibility to idiopathic azoospermia or severe oligozoospermia.

FAS, together with FASLG, triggers germ cell apoptosis, which occurs in various stages of mammalian testicular development. Single nucleotide polymorphisms (SNP) in the promoter regions of these two genes can influence their transcriptional activities and result in abnormal cell apoptosis, thus leading to spermatogenesis impairment. Therefore, it is reasonable to postulate that FAS and FASLG SNP may be associated with idiopathic azoospermia or severe oligozoospermia. To test this hypothesis, the distributions of FAS -1377G/A and -670A/G SNP and FASLG -844C/T SNP were studied in Han Chinese men. These SNP were genotyped by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) in 203 infertile men with idiopathic azoospermia or severe oligozoospermia and in 246 proven fertile controls. Frequencies of FASLG -844CC, CT and TT genotypes among infertile men were significantly different from those among controls (P = 0.024). Men with FASLG -844TT genotype had an increased risk of idiopathic azoospermia or severe oligozoospermia compared with those with CC and CT genotype (odds ratio 2.72, 95% confidence interval 1.25-5.93). The results suggest that FASLG -844C/T SNP may be a genetic predisposing factor of idiopathic azoospermia or severe oligozoospermia among Han Chinese men.

XPC gene polymorphisms and risk of idiopathic azoospermia or oligozoospermia in a Chinese population.

A retrospective case-control study was carried out in the Han-Chinese population to determine the polymorphisms of xeroderma pigmentosum complementation group C (XPC) gene on the risk of idiopathic azoospermia or oligozoospermia. The Ala499Val (C>T) and Lys939Gln (A>C) polymorphism of XPC gene were genotyped by polymerase chain reaction-restriction fragment length polymorphism in three groups of infertile men (172 patients of azoospermia, 25 patients of severe oligozoospermia, 55 patients of oligozoospermia) and 228 fertile men. Increased risk of idiopathic azoospermia, but not oligozoospermia was associated with the XPC variant genotypes of Ala499Val (C>T) [adjusted odds ratio (OR) = 1.67, 95% confidence interval (CI) = 1.04-2.68 for CT heterozygote and adjusted OR = 2.03, 95% CI = 1.10-3.75 for TT homozygote] compared with CC homozygous wide-type. The Lys939Gln (A>C) polymorphism was not related to spermatogenic failure. The combined risk alleles analysis and haplotype analysis showed that ORs increased as the number of the risk alleles increased and the 499T-939C haplotype had a significantly increased risk of idiopathic azoospermia (OR = 7.97; 95% CI = 3.51-18.07) compared with other haplotypes. The results suggest that XPC Ala499Val (C>T) polymorphism is correlated with high risk of idiopathic azoospermia in the Han-Chinese population.

The relation between urinary metabolite of pyrethroid insecticides and semen quality in humans.

OBJECTIVE: To explore the possible association between internal exposure levels of 3-phenoxybenzoic acid (3-PBA), an urinary metabolite of pyrethroids, and altered semen quality in Chinese men. DESIGN: A retrospective case-control study. SETTING: Center of clinical reproductive medicine. PATIENT(S): Three hundred seventy-six men with nonobstructive infertility. MAIN OUTCOME MEASURE(S): Urinary 3-PBA concentration, semen volume, sperm concentration, sperm number per ejaculum, sperm motility, sperm progression, and motion parameters. RESULT(S): The median 3-PBA concentration was 0.879 microg/g of creatinine. There was suggestive association between increased creatinine-adjusted 3-PBA quartiles and sperm concentration (odd ratios for the first, second, third, and fourth quartiles were 1.00, 1.31, 1.73, and 2.04, respectively), whereas sperm volume, sperm number per ejaculum, and sperm motility were weakly or nonsignificantly associated with 3-PBA quartiles. The sperm progression and motion parameters associated with creatinine-adjusted 3-PBA levels were straight line velocity (VSL) and curvilinear velocity (VCL). CONCLUSION(S): These observed associations between 3-PBA levels and some altered semen quality indicated the reproductive effects of pyrethroid exposure on adult men.

Polymorphisms in CYP1A1 gene are associated with male infertility in a Chinese population.

Cytochrome P4501A1 (CYP1A1) is a key enzyme in phase I bioactivation of polycyclic aromatic hydrocarbons (PAHs), which have potential reproductive toxicity. The aim of this study was to investigate the association of the CYP1A1 polymorphisms with male infertility in a Han-Chinese population. We genotyped two polymorphisms, CYP1A1*2A and CYP1A1*2C, using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay in a hospital-based case-control study including 192 infertile patients with non-obstructive azoospermia or severe oligozoospermia and 226 fertile controls. We found that the genotype distribution of CYP1A1*2C was significantly different between the patients and the controls (p = 0.019). Analysis showed that CYP1A1*2C AG genotype was associated with a significantly decreased risk of male infertility [odds ratio (OR) = 0.56, 95% confidence interval (95% CI) = 0.36-0.86, p = 0.005] compared with the AA genotype. A statistically significantly decreased risk of male infertility was found to be associated with the CYP1A1*2C AG genotype plus GG genotype compared with CYP1A1*2C AA genotype (OR = 0.60, 95% CI = 0.40-0.91, p = 0.011). No significant association was detected between CYP1A1*2A polymorphism and male infertility. Haplotypic analysis showed a significantly increased risk of male infertility associated with the C-A haplotype compared with the T-A haplotype (OR = 1.98, 95% CI = 1.27-3.09), indicating a synergic effect of the two polymorphisms. Our results suggest that the CYP1A1 polymorphisms may contribute to the pathogenesis of male infertility in the Han-Chinese population.

Association of XRCC1 gene polymorphisms with idiopathic azoospermia in a Chinese population.

AIM: To assess the possible role of genetic polymorphisms in DNA repair gene XRCC1 (X-ray repair cross-complementing group 1) during spermatogenesis by investigating the associations of one promoter polymorphism (T-77C) and two exonic polymorphisms (Arg194Trp and Arg399Gln) in XRCC1 gene with risk of idiopathic azoospermia in a Chinese population. METHODS: The genotype and allele frequencies of three observed polymorphisms were examined by polymerase chain reaction-restriction fragment length polymorphism based on a Chinese population consisting of 171 idiopathic azoospermia subjects and 247 normal-spermatogenesis controls. RESULTS: In our study, all the observed genotype frequencies were in agreement with Hardy-Weinberg equilibrium. The 399A (GA+AA) allele frequency for idiopathic azoospermia subjects and controls was 0.216 and 0.269, respectively. Compared with GG genotype, the AA genotype of Arg399Gln showed a significant association with a decreased risk of idiopathic azoospermia (odds ratio = 0.315; 95% confidence interval = 0.12-0.86). However, no significant differences were found between the cases and controls for T-77C and Arg194Trp polymorphisms. The major haplotypes of XRCC1 gene were TCG, TTG and TCA, whereas no haplotypes appeared to be significantly associated with idiopathic azoospermia based on the cutoff of P < 0.05. CONCLUSION: In a selected Chinese population, AA genotype of Arg399Gln appears to contribute to a decreased risk of idiopathic azoospermia, while we have not any evidence of involvement of XRCC1 T-77C and Arg194Trp polymorphisms in idiopathic azoospermia.

DNA repair gene XRCC1 and XPD polymorphisms and the risk of idiopathic azoospermia in a Chinese population.

Genetic polymorphisms in DNA repair genes may influence individual variation in DNA repair capacity and further influence the risk of developing cancer. However, little information is available on these polymorphisms in infertility. To investigate whether polymorphisms in DNA repair genes, X-ray repair cross-complementing group 1 (XRCC1) and xeroderma pigmentosum group D (XPD), alone or in combination, are associated with the risk of developing idiopathic azoospermia, the genotype and allele frequencies of three observed polymorphisms (XRCC1 Arg194Trp and Arg399Gln, and XPD Lys751Gln) were examined by polymerase chain reaction-restriction fragment length polymorphism based on a Chinese population consisting of 171 idiopathic azoospermia patients and 247 normal-spermatogenesis fertile controls. Associations between the polymorphisms and the idiopathic azoospermia risk were estimated by logistic regression, and the Statistical analysis system was used to test the gene-gene joint effects. All observed polymorphisms were in agreement with Hardy-Weinberg equilibrium. The XPD 751Gln allele seemed to be a risk allele for azoospermia, with a frequency of 11.40% in the cases and 5.67% in the controls (p=0.004). Compared with the Lys/Lys genotype, the XPD 751 Lys/ increased 5.100- or 3.064-fold, respectively, when combined with the XRCC1 194 Arg/Arg or 399 Arg/Arg genotype. In conclusion, our study provided the first evidence that the XPD and XRCC1 polymorphisms contributed to the risk of developing idiopathic azoospermia in a selected Chinese population.

The association of Y chromosome haplogroups with spermatogenic failure in the Han Chinese.

A significant proportion of male infertility is accompanied by an abnormal semen analysis, azoospermia or severe oligozoospermia, which is generally assumed to be the result of spermatogenic failure. The genetic contribution in the process of spermatogenesis, particularly the role of the Y chromosome in determination of semen quality, is still obscure. In order to explore the relationship between Y chromosome haplogroup and spermatogenic failure, we collected 285 idiopathic infertile males with azoo-/oligozoospermia and 515 fertile men, adopted 12 binary markers and recruited the subjects (cases and controls) in the same region to test whether there is a possible susceptibility of certain Y haplogroups to spermatogenic failure in the Han Chinese population. The results indicated that the prevalences of hg K in the control and the case population were 0.78% (4/515) and 2.80% (8/285), respectively. The difference between the frequencies of the hg K in the infertile males and the normal control population was significant [odds ratio (OR) = 3.69; 95% confidence interval (CI) = 1.10-12.36] (P = 0.028). However, in the other haplogroups no significant differences were found. In conclusion, Y haplogroup-K might bear a risk factor of male infertility, and the individuals in the haplogroup need to be further examined.

[Association of FASL-844 polymorphism with the risk of idiopathic azoospermia and severe oligozoospermia].

OBJECTIVE: To study the distribution of FASL-844 polymorphism in southern Chinese males of Han nationality and examine the contribution of the polymorphism to susceptibility of idiopathic azoospermia and oligozoospermia. METHODS: FASL-844 polymorphism was genotyped by polymerase chain reaction and restriction fragment length polymorphism(PCR-RFLP) in 184 infertile patients with idiopathic azoospermia or severe oligozoospermia 236 normal fertile male controls. RESULTS: Frequencies of FASL-844 CT and TT genotypes of the patients were significantly different from those of the controls (P = 0.024; P = 0.008). Males with FASL-844 TT genotype had an increased risk of idiopathic azoospermia or severe oligozoospermia compared with those with CC genotype (OR 2.76, 95% CI: 1.20-6.35), and even a higher risk when compared with those with CC and CT genotypes (OR 2.90, 95% CI: 1.28-6.58). CONCLUSION: FASL-844 polymorphism appears to be a genetic predisposing factor of idiopathic azoospermia or severe oligozoospermia among southern Chinese Han males.