EXPRESSION OF C-KIT AND ITS LIGAND, STEM-CELL FACTOR, IN NORMAL AND SUBFERTILE HUMAN TESTICULAR TISSUE

The c-KIT proto-oncogene encodes for a transmembrane receptor and is a ssociated with maturation of several cell types, including germ cells. The ligand of the receptor has been identified as stem cell factor (S CF). Loss or alteration of the expression of either of these factors l eads to anemia, albinism, and/or sterility in mice. We examined the ex pression of c-KIT and SCF by immunohistochemistry in specimens from no rmal and infertile human testis. All specimens were obtained in tile e valuation of male subfertility. We were able to demonstrate staining f or c-KIT in Leydig cells in all specimens. Normal testis stained for c -KIT in the cytoplasm of early spermatogenic cells, as well as the acr osomal granules of the round spermatids and the acrosome of testicular spermatozoa. However, staining in testis demonstrating maturation arr est failed to demonstrate acrosomal staining, and Sertoli-only specime ns demonstrated staining for cKIT in Leydig cells only. The results fo r SCF demonstrated an overall uniform staining of Leydig cells in all specimens. The intensity of staining of Sertoli cells increased from n ormal to maturation arrest to Sertoli-only specimens. Germ cell staini ng was consistently negative. We hypothesize that these staining patte rns for SCF are due to either lack of staining of the receptor-ligand complex or overexpression of the kit ligand in tissue that does not ex press the kit receptor. It appears that the c- kit receptor is express ed in the acrosome of developing germ cells, as well as in Leydig cell s and early spermatogenic cells, suggesting a role in the acrosome rea ction, as well as germ cell maturation and differentiation.