Growth stimulation of ovarian and extraovarian mesothelial cells by corpus luteum extract

Ovarian (OM) and extraovarian (EM) mesothelia represent a common source of gynecologic malignancies with yet unclear pathogenesis. Ovulation triggers a finite wave of DNA synthesis and morphogenesis only in native OM cells, probably through the activation of intraovarian growth factors. To evaluate their growth response to such factors, OM and EM cells were obtained from estrous New Zealand white rabbits by enzymatic dispersion and unit gravity sedimentation. Cell cultures were maintained in serumless, fibronectin-rich, HL-1 medium without or with rabbit corpora lutea tissue extracts (CLE). The growth effects of CLE were evaluated by measuring percent changes in cell number relative to controls (CCN), cell population doublings (CPD), cell population doubling time in hours (CPDT). After 7.5 days, CLE enhance (P < 0.001) the growth of both OM and EM cells, which exhibited, respectively, a CCN of 214 and 257%; a CPD of 2.89 and 2.87; and a CPDT of 54.39 and 59.49. CLE-treated OM and EM cells were smaller, formed more cohesive monolayers, and exhibited more frequent and diffuse microvilli than control cells. These data show a similar in vitro response of OM and EM cells to luteal growth factors, suggesting that the lack of postovulatory morphogenesis in native extraovarian mesothelia is due to the spatially restricted activity of intraovarian growth factors.