Luteal hypoplasia and in vitro granulosa cells proliferation in cows

Two groups of cows were set up. In one group ovulation was induced, leading to luteal hypoplasia (FSH non-injection group or group 1). In the other group ovulation was induced and FSH injected simultaneously to improve luteinization (FSH injection group or group 2). Granulosa cells were collected from the ovarian follicles of the cows of the two groups immediately before ovulation. Their ability to proliferate and secrete progesterone in vitro was compared between the two groups. Granulosa cells proliferated in vitro more rapidly in group 2 than in group 1. Therefore, FSH injection was proved to be very effective for the proliferation of these cells. Cultured granulosa cells showed the same morphology, regardless of the FSH injection. They presented changes from fibroblast-like cells to epithelioid cells after adhering to a coverslip. They were transformed to epithelioid cells, however, earlier in group 2 than in group 1. Their ability to secrete progesterone in vitro was essentially the same between the two groups. Progesterone secretion decreased gradually in amount in both groups with the advance in culture. Therefore, it was considered that luteal hypoplasia might have been caused by a low ability of granulosa cells, which would be transformed to lutein cell, to proliferate.