Expression Of HIF-1α In Mouse Testis And Its Effect On Sex Hormones Levels And Apoptosis Of Spermatogenic Cells In Simulated Altitude Of5000m Hypoxia Environment

Plain population into the plateau region (altitude3000m above) are prone to acute mountain sickness (mild acute altitude sickness, pulmonary edema and cerebral edema). The health of the male reproductive system could be affected by high altitude hypoxia environment, which could reduce the sperm density and sperm motility, increase sperm malformation rate, reduce testosterone level in the blood. Hypoxia could induce spermatogenic cell apoptosis in animals. However, the mechanism of hypoxia environment in promoting apoptosis of spermatogenic cells is not yet clear.In this study, hypoxia animal model was replicated in hypobaric chamber with simulation altitude5000m. Animals were randomly divided into3,7,14and28days normoxic and hypoxic groups. The level of serum testosterone (T), free testosterone (FT), follicle-stimulating hormone (FSH) and luteinizing hormone (LH) was analyzed by ELISA method. Sperm count, motility rate and sperm deformity rate of epididymal sperm suspension were detected. Spermatogenesis was analyzed by flow cytometry method. The apoptotic cells in the testis were determined using TUNEL method. Immunohistochemical staining, RT-PCR and Western blot were used to analyzed HIF-1α, VEGF and EPO expression in testicular tissue. Microvascular density (MVD) in testicular tissue was determined using immunohistochemical detection with CD31.Compared with corresponding normoxic groups, serum T, FT, FSH and LH concentrations in hypoxia3d group were higher (P<0.05); T and LH concentrations in hypoxia14d group were lower (P<0.05). Sperm count and motility rate in hypoxia7d and14d groups declined (P<0.05); sperm deformity rate in all hypoxia groups increased (P<0.05). Relative quantity of hypo-haploid cells increased (P<0.01), haploid cells decreased (P<0.05), cells between diploid and tetraploid cells increased (P<0.05), tetraploid cells decreased (P<0.05) in hypoxia3d group mice. The apoptosis index (AI) of germ cells in hypoxia7,14and28d groups increased (P<0.05). Immunohistochemistry showed that HIF-la expression was increasd in every hypoxia group (P<0.05), VEGF expression was increased in hypoxia7,14and28d groups (P<0.05), EPO expression was increased in hypoxia7d group (P<0.05), MVD was increased in hypoxia7d and14d groups (P<0.05). RT-PCR showed that HIF-1α mRNA transcription levels was increased in hypoxia28d group, VEGF mRNA transcription levels was increasd in every hypoxia group, EPO mRNA was increased in hypoxia3d and7d groups and decreased in hypoxia14d and28d groups (P<0.05); Western blot showed that HIF-1α protein expression in hypoxia7,14and28d groups was increased (P<0.05), VEGF protein expression in every hypoxia group was increased (P<0.05), EPO protein did not significantly change. Pearson correlation analysis showed:HIF-la protein expression and serum T was negatively correlated in hypoxia3d group (r=-0.999, P=0.035), sperm deformity rate and AI was positively correlated in hypoxia14d group (r=0.933, P=0.007), HIF-1α protein expression and AI was positively correlated in hypoxia28d group (r=0.791, P=0.042), FT and sperm motility was positively correlated in hypoxia28d group (r=0.680, P=0.044).In simulated altitude of5000m hypoxia environment, the increased release of mice hypothalamus-pituitary-testicular axis hormones could promote spermatogenesis and production of deformed sperm in acute hypoxia environment; the high expression of HIF-1α protein in mice testis could induce germ cell apoptosis in chronic hypoxia environment.