Expression of c-kit messenger ribonucleic acid in human oocyte and presence of soluble c-kit in follicular fluid

The c-kit protooncogene receptor and its ligand stem cell factor (SCF) regulate the proliferation and survival of germ cells as well as hematopoietic cells and melanocytes. In adult rodent ovary, c-kit and SCF play important roles in follicular development. However, little information about c-kit in the human ovary is available. In this study, we examined the expressions of c-kit messenger ribonucleic acid (mRNA) and c-kit protein in human oocytes, granulosa cells, and follicular fluid obtained from the women who underwent in vitro fertilization or laparoscopic examination. Expression of c-kit mRNA was detected by RT-PCR in the oocytes and granulosa cells. Western blot analysis showed the presence of soluble c-kit protein in the follicular fluid, and lower levels of c-kit protein were detected in the granulosa cells and the supernatant of granulosa cell cultures. The concentration of soluble c-kit in follicular fluid measured by enzyme-linked immunosorbent assay showed significant correlation with fluid volume and follicular fluid concentrations of estradiol, testosterone, and androstenedione. In summary, we found for the first time the presence of c-kit mRNA and soluble c-kit protein in human oocytes and follicular fluid. The results suggested that in human ovary, c-kit may play an important role in follicular development.