Temporal and spatial expression of neurotrophins and their receptors during male germ cell development.

Spermatogenesis is a stepwise cellular differentiation process involving proliferation and commitment to differentiate in spermatogonia, meiosis in spermatocytes, and morphological changes in round spermatids. The whole process is regulated by intercellular communication between the germ cells and the supporting cells. In order to investigate whether neurotrophin family and their receptors contribute to the intercellular communication, we examined the expression of neurotrophins and their receptors in testis during spermatogenesis. One of neurotrophin family, NT-3 was expressed in spermatocytes and spermatogonia while its high affinity receptor, TrkC was found mainly in late spermatids and their low affinity receptor, TrkA in spermatocytes and round spermatids. On the other hand, BDNF immunoreactivity was found in Sertoli cells while its high affinity receptor, TrkB was found in spermatogonia. The temporally and spatially regulated expression of neurotrophins, NT-3 and BDNF, and their receptors, TrkC and TrkB, during male germ cell development suggests that neurotrophins play as the paracrine factors in the intercellular communication between the germ cells and the supporting somatic cells to control germ cell development.