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

A possible relationship between transforming growth factor β receptor type I (TβRI) and type II (T®II) protein expression in human granulosa cells and the quality of preimplantation embryo development in vitro was studied using immunoblot analysis of TβRI and TβRII 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. TβRI and TβRII 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 TβRI and TβRII are expressed in the soluble and membrane fractions of granulosa cells. Most notably, the zygote always developed into a grade I quality preimplantation embryo when the oocyte originated from a follicle that expressed a low amount of TβR protein in the granulosa cell membrane. Reduced expression of TβR in the granulosa cell membrane may form a mechanism critically regulating TGFβ action on granulosa cells, and the latter in turn precisely control oocyte development, hence, the subsequent cleavage potential.