Granulosa cells were prepared from follicular aspirates obtained at oocyte collection for in-vitro fertilization (IVF) and maintained in culture. Substantial loss of cells from the culture surface occurred in the absence of gonadotrophin when cells were maintained on a thin layer of extracellular matrix (ECM) using a defined, serum-free medium. This cell loss was clearly and significantly reduced in the presence of human chorionic gonadotrophin (HCG) by days 4-6 of culture, and occurred in conjunction with loss of ECM. Analysis of culture medium by zymography using gelatin as substrate demonstrated the presence of metalloproteinases (MMP), MMP-9 (gelatinase B) appearing as the predominant band. Measurement of overall gelatinase activity in culture media revealed a progressive fall in gelatinase expressed on a per cell basis in media from HCG-treated cultures and this was less marked in controls. This suppression of gelatinase activity was consistent with an observed increase in production of tissue inhibitor of metalloproteinase-1 (TIMP-1) by HCG-treated cells, which was significant by days 6-8 of culture. We speculate that stabilization of the ECM may be an important aspect of HCG action in the corpus luteum.
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Aston et al. (1996) studied this question.