In vitro, follicle-stimulating hormone prevents apoptosis and stimulates deoxyribonucleic acid synthesis in the rat seminiferous epithelium in a stage-specific fashion.

Abstract

The effects of FSH on stage-specific apoptosis and DNA synthesis in the adult rat seminiferous epithelium were studied in vitro. Seminiferous tubular segments from stages I, V, VIIa, and VIII-IX were cultured for 24, 48, and 72 h in different concentrations of FSH. Apoptotic cells were detected by in situ end labeling of DNA strands and quantified from squash preparations. After 48 h of culture, a FSH concentration of 2 ng/ml prevented apoptosis of early (steps 1-3) spermatids. In stage VIII-IX tubules cultured for 72 h, FSH decreased the apoptosis of pachytene spermatocytes. An apoptotic type of cell death of germ cells was confirmed by DNA laddering, electron microscopy, supravital acridine orange staining, and phase contrast microscopy of unstained living cells. The effects of FSH on stage-specific DNA synthesis were studied using the same culture system. FSH increased [3H]thymidine incorporation specifically at stages I and VIII-IX, and autoradiography confirmed stimulation of mitotic and meiotic DNA synthesis in type B spermatogonia and preleptotene spermatocytes, respectively. Increased thymidine incorporation also suggested that FSH stimulated DNA synthesis of type A and intermediate spermatogonia. Most effects exerted by FSH were seen in stages containing high levels of FSH receptors and FSH-stimulated cAMP production. In conclusion, the results suggest that FSH, probably acting via Sertoli cells, has a regulatory function in spermatogenic apoptosis and DNA synthesis in stages previously demonstrated to be preferentially dependent on FSH stimulation.