Characterization of bovine ovarian surface epithelium and stromal cells: identification of secreted proteins.

The majority of ovarian cancers are derived from a single layer of epithelial cells that covers the surface of the ovary termed the ovarian surface epithelium (OSE). Ovarian surface stromal cells underlie the OSE and have a morphology distinct from that of the interstitial stromal cells between follicles. Because of the similarities between bovine and human ovarian physiology, and to allow an adequate supply of tissue and cells, bovine OSE and stromal cell cultures were established to investigate the cell biology of these cell types. Morphological analysis of bovine ovarian sections revealed that several layers of ovarian surface stromal cells can be identified and are structurally distinct from interstitial stromal cells. Both OSE and stromal cells can be isolated and cultured for weeks in the absence of presence of serum. The cell populations were found, through use of a keratin immunocytochemical stain for OSE, to be highly purified. To investigate the functional properties of the two cell types, radiolabeled secreted proteins were collected and electrophoretically analyzed. The radiolabeled secreted protein profiles of OSE and stromal cells were found to be distinct with a discrete number of secreted proteins. Major OSE secretory products were obtained from serum-free concentrated conditioned medium, electrophoretically separated, blotted, and sequenced. Two OSE secretory products of 28 kDa and 40 kDa were sequenced and found to match a sequence in the computerized database. The 28-kDa OSE protein was identified as a tissue inhibitor of metalloproteinase, TIMP. The 40-kDa OSE protein was identified as the insulin-like growth factor (IGF) binding protein-2 (IGFBP2).(ABSTRACT TRUNCATED AT 250 WORDS)