TRANSLATE

The ligand of the c-kit receptor promotes oocyte growth.

Packer AI, Hsu YC, Besmer P, Bachvarova RF

Dev Biol 1994 Jan 161:1 194-205

Abstract

Both genetic and descriptive studies have implicated the c-kit receptor and its ligand, KL, in the process of oocyte growth in the postnatal mouse ovary. In order to test the hypothesis that KL is an oocyte growth factor, we used an oocyte culture system to study its effects in vitro. Initial experiments established that both ovarian c-kit and KL are biologically active.

An immune complex kinase assay demonstrated that ovarian c-kit, found primarily on oocytes, has autophosphorylation activity, and a bone marrow-derived mast cell coculture assay indicated that granulosa cells produce functional KL. The addition of 10 ng/ml KL to growing follicles cultured in collagen gels resulted in a 67% increase in the rate of oocyte growth, and a doubling of the rate was achieved at around 50 ng/ml.

ACK2, a monoclonal antibody against c-kit, severely inhibited the growth of late fetal and neonatal oocytes in coculture with ovarian cells and had less effect on growing oocytes cultured in follicles from 10- to 11-day-old mice.

Genistein, an inhibitor of tyrosine kinases, including c-kit, blocked oocyte growth and disrupted follicle morphology.

In initial studies on the regulation of KL production in granulosa cells, we found that both dibutyryl cyclic AMP and growing oocytes were able to induce increased KL mRNA accumulation in granulosa cell monolayers as assessed by Northern analysis. These studies demonstrate that c-kit and KL are required for maintenance of oocyte growth in vitro.

Excerpts

Ín the presence of genistein, many of the follicles became disorganized and the oocytes became partially denuded (Fig. 6B). There also appeared to be less granulosa cell proliferation compared to the control follicles. This result suggests that tyrosine phophorylation is important for granulosa cell proliferation and follicle organization, as well as for oocyte growth.

Evidence is accumulating that the oocyte is important for normal granulosa cell proliferation and differentiation. they were consuming soy protein isolate.