Hepatocyte growth factor induces rat ovarian surface epithelial cell mitosis or apoptosis depending on the presence or absence of an extracellular matrix

The present studies showed that sequential treatment with equine CG (eCG) a nd hCG not only induced an increase in ovarian weight, but also caused an e stimated 4.6-fold increase in the number of ovarian surface epithelial cell s. In addition, eCG-hCG treatment increased ovarian hepatocyte growth facto r (HGF) messenger RNA levels. These studies also demonstrated that rat prim ary ovarian surface epithelial cells as well as a cell line derived from ra t ovarian surface epithelium (i.e. ROSE-179 cells) do not express the LH (h CG) receptor. Both of these cells express c-Met, the receptor for HGF. To a ssess the effects of hCG and HGF on ovarian surface epithelial cell mitosis , ROSE-179 cells were cultured for 24 h in serum-supplemented medium on eit her glass or the synthetic fibronectin-like extracellular matrix protein, p ronectin (RGD). The cells were then cultured for 24 h in serum-free medium in the presence or absence of hCG or HGF. The numbers of cells at 2, 24, an d 48 h of culture were determined. The percentage of apoptotic cells was as sessed by in situ DNA staining at 48 h of culture. In the serum-supplemente d medium in the presence or absence of RGD, the number of ROSE-179 cells do ubled. In serum-free medium, cell proliferation was reduced, and the percen tage of apoptotic nuclei ranged between 10-15% regardless of the substrate. Neither mitosis nor apoptosis was influenced by hCG in the presence or abs ence of RGD. For ROSE-179 cells cultured in serum-free medium on RGD, HGF i nduced mitosis, resulting in a 2.8 +/- 0.2-fold increase in cell number com pared with the 24 h control values. On a glass substrate in serum-free medi um, HGF did not induce mitosis, but increased the percentage of apoptotic n uclei. Time-lapse photographic analysis revealed that on RGD, cells undergo ing HGF-induced mitosis showed a transient reduction in cell contact. On gl ass, HGF caused many cells to completely lose contact and separate from eac h other. Collectively, these data suggest that in vivo gonadotropins stimul ate HGF expression and ovarian surface epithelial cell proliferation. Based on in vitro studies, it is likely that the mitogenic action of hCG is medi ated by HGF. However, HGF only induces mitosis in the presence of an extrac ellular matrix.