The effect of microgravity on tissue structure and function of rat testis.

To explore whether an environment of weightlessness will cause damage to the reproductive system of animals, we used the tail-suspension model to simulate microgravity, and investigated the effect of microgravity on the tissue structure and function of the testis in sexually mature male rats. Forty-eight male Wistar rats weighing 200-250 g were randomly assigned to three groups (N = 16 each): control, tail traction, and tail suspension. After the rats were suspended for 7 or 14 days, morphological changes of testis were evaluated by histological and electron microscopic methods. The expression of HSP70, bax/bcl-2 and AR (androgen receptor) in testis was measured by immunohistochemistry. Obvious pathological lesions were present in the testis after the rats were suspended for 7 or 14 days. We detected overexpression of HSP70 and an increase of apoptotic cells, which may have contributed to the injury to the testis. The expression of AR, as an effector molecule in the testis, was significantly decreased in the suspended groups compared to control (P < 0.01). We also observed that, with a longer time of suspension, the aforementioned pathological damage became more serious and some pathological injury to the testis was irreversible. The results demonstrated that a short- or medium-term microgravity environment could lead to severe irreversible damage to the structure of rat testis.