216. c-kit Expression study: timing of onset in rodent testis and irradiated rat testis model

Abstract

Primordial germ cell and spermatogonial cell function is essential for normal male fertility. These cells require Sertoli–germ cell interactions, specifically somatic cell-derived stem cell factor (SCF) that acts through the c-kit receptor to govern primordial germ cell migration in the foetus, spermatogonial differentiation during puberty and adulthood, and Leydig cell steroidogenesis. We performed a comprehensive study of the c-kit mRNA expression profile in the pre- and post-pubertal mouse and rat testes by in situ hybridisation. Expression of c-kit mRNA was first visualised in germ cells after birth, with the levels concordant with the number and appearance of the differentiated spermatogonial subtypes in both the rat and the mouse. We also studied c-kit expression in the irradiated adult rat testis, in which only undifferentiated spermatogonia are present. After treatment with Cetrorelix, GnRH antagonist (3 days, 1, 2 and 4 weeks) germ cell maturation is re-initiated. Expression of c-kit messenger RNA was observed in the undifferentiated spermatogonia in both untreated and treated testes sections. In contrast, c-kit protein expression was undetectable until 4 weeks of hormone treatment. This suggests that c-kit mRNA and protein expression are differentially regulated and that protein expression relates to somatic cell function.