Background

Immunocytochemical localization of cytoplasmic and nuclear intermediate filaments in the bovine ovary during folliculogenesis

The cellular cytoskeleton is composed of three fibrillar systems, namely actin microfilaments, microtubules and intermediate filaments (IFs). It not only is a structural system, which mediates functional compartmentalization, but also contributes to many cellular processes such as transport, mitosis, secretion, formation of cell extensions, intercellular communication and apoptosis. In this study, we have examined the distribution of four groups of IFs [cytokeratins (CKs), vimentin, desmin and lamins] in the somatic and germinal cells of the bovine ovary using RT-PCR and immunohistochemical techniques. Using RT-PCR, specific transcripts for all intermediate proteins studied (CK8, CK18, desmin, vimentin, lamin A/C and lamin B1) were detected. A characteristic immunohistochemical staining pattern was observed for the different IFs within the ovary. In this study, we used antibodies against type I CK (acidic CKs: CK14, CK18 and CK19) and type II CK (basic CKs: CK5 and CK8). Among these, only antibodies against CK18 gave a characteristic pattern of immunostaining in the ovary, which included the surface epithelium, the follicle cells, the endothelium of blood vessels and rete ovarii. Antibodies against all other CKs resulted in a weak staining of a limited number of cellular structures (CK5 and CK19) or were completely negative (CK8 and CK14, apart from the surface epithelium). Vimentin antibodies resulted occasionally in a weak staining of the granulosa cells of primary and secondary follicles. In late secondary follicles, the basal and the most apical follicle cells contacting the zona pellucida usually showed a marked immunostaining for vimentin. In antral follicles, three different immunostaining patterns for vimentin were observed. Desmin immunostaining was confined to the smooth muscle cells of blood vessels. Although mRNA for lamin A/C and lamin B1 could be demonstrated using RT-PCR, no immunostaining was found for lamins, neither in the follicle cells nor in the oocytes.

Ovarian surface epithelium in patients with severe ovarian infertility: a potential source of cells expressing markers of pluripotent/multipotent stem cells

The aim of this study was to confirm the presence of stem cells in the ovarian surface epithelium of patients with premature ovarian failure and no mature follicles and oocytes. In these patients, small round cells of unknown origin expressing SOX-2 marker of pluripotency were observed among the epithelial cells just after the ovarian surface epithelium scraping. These cells were an integral part of the ovarian surface epithelium. When the scraped cells were cultured in a medium with added follicular fluid to provide some ovarian niche, primitive oocyte-like cells and typical round-shaped cell clusters positively stained on alkaline phosphatase, and markers of pluripotency, such as SOX-2 and SSEA-4, were developed. These markers were expressed early and also later in the culture. Single oocyte-like cells expressed genes OCT4A, SOX-2, NANOG, NANOS, STELLA, CD9, LIN28, KLF4, GDF3, and MYC, characteristic for pluripotent stem cells. The results of this study confirmed the presence of putative stem cells in the ovarian surface epithelium of these patients and provided some basis to create a stem cell line in the future.