Summary: | Objective To investigate the damage of seminiferous tubules in mice exposed to hypoxia and the effects of hypoxia on apoptosis of mouse spermatocytes in the seminiferous tubules. Methods Forty 3-week-old male Balb/c mice were randomly assigned into a normoxia group (housed in a normoxic condition at an altitude of 300 m) and 3 hypoxia groups exposed to hypoxia for 15, 30 or 60 d in a hypobaric chamber simulating the condition at an altitude of 6 000 m. After hypoxic exposures, the mice were euthanized and the testicular tissues were examined for pathological changes in the seminiferous tubules using HE and TUNEL staining. A mouse spermatocyte-derived cell line, GC-2spd, was also cultured in a normoxic condition or a hypoxic condition (1% O2 and 5% CO2) for 48, 60, or 72 h, and the cell apoptosis was detected using flow cytometry and TUNEL staining and by examining LDH, caspase-3, caspase-8, and caspase-9 levels in the culture medium. Results The apoptotic rates of the spermatocytes in the testicular seminiferous tubules of the mice increased significantly after hypoxic exposure for 15, 30 and 60 d as compared with the apoptosis rate of (4.6±1.4)% in the normoxia group (P < 0.01). In cultured GC-2spd cells, hypoxic exposure for 48, 60 and 72 h also significantly increased the cell apoptotic rate to (15.43±1.47)%, (44.10±14.10)% and (63.36±12.74)%, as compared with the rates of (4.18±1.40)%, (5.45%±2.30)%, and (14.47±8.21)% in the normoxia group, respectively (P < 0.01). Microscopically, the numbers of apoptotic spermatocytes per field were 22±3, 55±5, and 82±12 in the hypoxia group at 48, 60 and 72 h, respectively, significantly greater than those in the normoxia group (5±1, 8±2, and 15±4, respectively; P < 0.01). The absolute value of LDH activity in cultured GC-2spd cells at 48 h was significantly higher in the hypoxia group than in the normoxia group (1.28±0.18 vs 0.48±0.09, P < 0.01); the values of caspase-3/8/9 in the hypoxia group at 48 h were 12.20±0.40, 22.73±0.60, and 10.90±0.40, respectively, significantly higher than those in the normoxia group (7.67±0.45, 16.20±0.56, and 7.03±0.25, respectively, P < 0.01). Conclusion Exposure to hypoxia simulating the condition at an altitude of 6 000 m for 15 d can cause decreased spermatogenesis and increased apoptosis of the spermatogenic cells in mice, suggesting that spermatocyte apoptosis is one of the mechanisms by which hypobaric hypoxia reduces spermatogenesis.
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