Transforming growth factor beta receptor expression in hyperstimulated human granulosa cells and cleavage potential of the zygotes

A possible relationship between transforming growth factor beta receptor type I (TbetaRI) and type II (TbetaRII) protein expression in human granulosa cells and the quality of preimplantation embryo development in vitro was studied using immunoblot analysis of TbetaRI and TbetaRII in hyperstimulated granulosa cells and morphological assessment of the cleavage potential of the zygotes in vitro. Washed granulosa cells were collected from </= 35-yr-old women with either tubal defects or mild endometriosis who were undergoing controlled ovarian hyperstimulation prior to oocyte retrieval for in vitro fertilization. TbetaRI and TbetaRII were immunoprecipitated from 100 000 g soluble and crude membrane fractions using receptor-specific antibodies and analyzed by Western immunoblotting, and the relative expression was quantitated from the luminographs. The gross morphology (embryo grade) of the preimplantation embryos developed in vitro was determined using a stereomicroscope. Both TbetaRI and TbetaRII are expressed in the soluble and membrane fractions of granulosa cells. Most notably, the zygote always developed into a grade 1 quality preimplantation embryo when the oocyte originated from a follicle that expressed a low amount of TbetaR protein in the granulosa cell membrane. Reduced expression of TbetaR in the granulosa cell membrane may form a mechanism critically regulating TGFbeta action on granulosa cells, and the latter in turn precisely control oocyte development, hence, the subsequent cleavage potential.