The transient disappearance of cytokeratin in human fetal and adult ovaries

Cells from the inner and outer granulosa cell layers of the ovarian follicl es differ in function, probably because of their different origins from the surface epithelium and from the rete. This suggestion has not so far been thoroughly investigated in the human ovary. We examined fetal ovaries from the early, middle and late gestational periods, ovaries from fertile women, and preovulatory follicular cells obtained from patients under in vitro fe rtilization therapy (TVF). Indirect immunohistology and immunocytology were used to detect the presence of cytokeratin (CK)-positive epithelial cells. In fetal ovaries from the early gestational period, prominent rete tubules (sometimes with oocytes) appeared to be fused with the sex cords and primo rdial follicles. Both showed CK-positively, detected with the pan-CK antibo dy Lu-5. Cytokeratin 19 was clearly expressed in the fusion area. In the fe tal and adult ovaries. CK-positive follicular or granulosa cells were noted in the primordial and primary follicles as well as the preovulatory follic les. Cytokeratin was not detected in the granulosa cells of growing follicl es, CK-positive and -negative luteal cells were identified in the developin g corpus luteum. We conclude for the human ovary: (1) the heterogeneous mor phology of granulosa cells may be explained by their twofold origin from th e surface epithelium and the rete, (2) the rete tubules appear to be involv ed in folliculogenesis, (3) the transient absence of CK expression in growi ng follicles compared to resting and mature follicles or to the developing corpus luteum indicates a particular role of CK-positive cells at the perio vulatory period.