| Objective Oxygen is an indispensable element for the survival of most animals on the Earth.The body has various corresponding changes to adapt to a hypoxia environment.With an increasing number of women going to the plateau,people pay more attention to the influences this special environment brings them.Compared with males,females have unique physiological characteristics,which bring some difficulties to the research;therefore,there are few studies on the effects of altitude hypoxia on the female reproductive system.This study was conducted to understand the effects of the hypoxic environment on HIF-1expression in mouse ovaries and on mouse reproductive function and offspring development.Methods In this study,a low pressure hypoxic animal experimental chamber was used to establish a simulated altitude of 6500 m.150 female mice were randomly divided into plateau group and plain group according to body weight,the plateau groups divided into 3-day plateau group,5-day group,10-day group and 15-day group,30 mice in each group.The HIF-1α level in the mouse ovary were tested by immunohistochemistry and Western Blot,evaluated ovarian tissue hypoxia condition;the ovary index(ovarian index=weight of bilateral ovaries of mouse/weight of mouse × 100%)were tested,and the changes in ovarian tissue morphology and follicle number were observed by HE staining;enzyme-linked immunosorbent assay were detected to get the serum values of anti-Müllerian hormone(AMH),follicle stimulating hormone(FSH),luteinizing hormone(LH),estradiol(E2)and progesterone(PROG);mating tests were done to get the gestational litter numbers,neonatal mouse weight,fertility rate(fertility rate=number of mouse in delivery offsprings/total number of female mouse×100%),mating period(the mating time required for a successful pregnancy).ResultsI.The expression of HIF-1α: immunohistochemistry showed that the ratio of HIF-1αpositive cells(the ratio of HIF-1α positive cells=number of cells which expressed HIF-1α/total number of cells×100%)increased with the extension of hypoxia.Western Blot showed that HIF-1α protein expression in the plateau groups were increased,the 3-day group and the 5-day group all had significant differences(P<0.05),the 10-day group and the 15-day group had the significant differences(P<0.01).II.Ovarian index: compared with the plain group,the ovarian index was decreased in the plateau group,the plateau 5-day group,plateau 10-day group and plateau 15-day group had significant differences(P<0.01).III.Ovarian histological changes: HE staining indicated that compared with the plain group,the numbers of ovarian follicles decreased,the granulosa cells were apoptotic with venous vascular expansion.IV.Reproductive hormone indicators:1.AMH: compared with the plain group,the AMH level decreased in each plateau groups,the 10-day group had the significant difference(P<0.05),the 5-day group and the 15-day group had significant differences too(P<0.01);2.FSH: compared with the plain group,the FSH level slightly increased in the plateau3-day group,considering for the acute stress response in mice exposed to the hypoxic environment,the 5-day group,10-day group and 15-day group all decreased,the 5-day group had significant difference compared with the plain group(P=0.029),the 10-day group and the 15-day group had significant differences compared with the plain group(P<0.001);3.LH: compared with the plain group,the LH levels increased in the plateau 3-day group,decreased in the 5-day group,10-day group and 15-day group,the 10-day group and15-day group had significant differences compared with the plain group(P respectively was0.005,<0.001);4.E2: compared with the plain group,the E2 levels in the plateau 5-day group and the15-day group were significantly different(P respectively was 0.038,<0.001);5.PROG: compared with the plain group,all of the PROG levels of the plateau groups were decreased and the differences were significant(P<0.001).V.Variation in reproductive capacity and condition of the offsprings:1.The fertility rate: the fertility rate of the 10-day group and the 15-day group were lower than the plain group,the difference was significant(P=0.007);2.The mating period: compared with the plain group,all of the mating periods prolonged in the plateau groups,the 5-day group,the 10-day group and the 15-day group had the significant differences(P<0.01).3.The numbers of gestational litters: compared with the plain group,the numbers of gestational litters decreased in the plateau 3-day group,the 10-day group and the 15-day group,the differences were significant(P<0.05).4.Neonatal mouse weight: there were no significant differences in neonatal mouse weight between the groups.Conclusions This study showed that the exposure to a simulated altitude of 6500 m hypoxia environment enhanced the expression of HIF-1α in ovaries of mouse,which showed the ovarian tissue hypoxia.With prolonged hypoxia,the ovarian index of the mouse reduced,ovarian volume atrophied,the levels of growth follicles reduced,and more corpora atreticas.The mouse fertility rate decreased;the mating period required for pregnancy became longer,the numbers of gestational litters decreased.The plateaus low pressure and hypoxic environment is proven to have adverse effects on the reproductive function of female mice and offsprings development;furthermore,providing a theoretical basis for our next research on the protection of female fertility.In addition,the results of this experiment suggest that the serum reproductive hormone in mice show a downward trend with prolonged hypoxia exposure.Whether this phenomenon is related to the adverse effects of high altitude hypoxic environment on the reproductive function of mice is still unclear,further research is needed in the future. |
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