Temperature control of spermatogenesis and prospect of male contraception.

Artificial cryptorchidism or local testicular heat treatment could induce reversible oligospermia or azoospermia in monkeys via germ cell apoptosis. A single exposure of rat or monkey testes at 43 degrees centigrade resulted in selective and reversible damage to seminiferous epithelium. Local warming monkey testes at 43 degrees centigrade water for consecutive two days (30 minutes per day) showed that the sperm amount in the semen decreased up to 80% at 28 days and is completely reversible. Furthermore, the heat treatment in combination with testosterone, the sperm account reduced to zero in 2 month time. Withdrawing the testosterone implant, the density of semen sperms recovered to the normal levels after 2-3 months. Apoptosis induced by testosterone occurs mainly at stages 7-8, while testicular "heat stress" induces germ cell apoptosis mostly at stages 1- 4 and 10-12, an additive reversible germ cell apoptosis could be achieved. These findings have provided an important theoretical basis for designing combined male contraceptives. This present review summarized progress on the mechanism of heat-induced germ cell apoptosis.