Heat stress causes testicular germ cell apoptosis in adult mice.

An investigation was undertaken to determine whether the germ-cell loss associated with exposure of the testis to abdominal temperature occurs by apoptosis. Using an adult-mouse model of experimental unilateral cryptorchidism, it was observed that DNA fragmentation, consistent with apoptosis, was observed on day 6 in the cryptorchid testis, with subsequent loss of testicular weight, histologic evidence of germ-cell loss, and histochemical staining of apoptotic germ cells observed on day 7. Vacuolization of the germinal epithelium and the appearance of multinucleated giant cells was noted synchronously with the onset of germ-cell loss. Histochemical staining for apoptosis was noted most frequently among the primary spermatocytes and round spermatids. These results indicate that the testicular germ-cell loss observed with exposure to abdominal heat stress occurs by apoptosis. Further investigation of the biochemical mechanisms involved in testicular apoptosis may provide strategies to address a variety of male reproductive issues such as contraception and infertility.