The steroid-driven cyclic growth, differentiation, and breakdown of the human endometrium represents perhaps the most dynamic interplay of endocrine, paracrine and autocrine systems among any normal adult tissue. As such, the normal endometrium is an excellent model system to study the role of specific hormones and growth factors in individual cell behavior, cell-cell interactions and, ultimately, tissue formation and function. We and others have demonstrated that the growth factor transforming growth factor-beta (TGF-beta) is produced by cells of the reproductive tract and serves a regulatory role on the growth and differentiation of specific cell types. Other growth factors such as epidermal growth factor (EGF) often antagonize the action of TGF-beta. We have identified a number of molecular markers associated with the proliferative and differentiated state of the human menstrual cycle in vivo, including several matrix- degrading metalloproteinases (MMPs) which are expressed exclusively in proliferative and menstrual endometrium. Our preliminary studies suggest the hypothesis that the estrogen-driven growth and expression of MMPs involves an indirect effect mediated through stromal cell expression of EGF and subsequent paracrine-autocrine actions. We hypothesize that progesterone-driven growth abatement, the expression of differentiation- related proteins, and the inhibition of MMP expression involves an indirect effect on stromal cells through the expression of TGF-beta which antagonizes the estrogen/EGF effect and promotes cell differentiation in an autocrine/paracrine fashion. We have developed specific techniques for the isolation and culture of the principal human endometrial cell types. Using this in vitro model system, we propose the following specific aims to test these hypotheses: 1) to determine the cellular localization and temporal patterns of EGF and TGF-beta mRNA and protein expression during the normal human menstrual cycle; 2) to determine in vitro ability of intact endometrium and isolated endometrial cell types to produce TGF-beta and EGF mRNAs and proteins in response to specific endocrine signals; 3) to determine the in vitro role of EGF and TGF-beta on endometrial stromal and epithelial cell growth and the expression of the growth-related MMPs, and on differentiation as manifest by the secretion of differentiation- related proteins; and 4) to determine the requirement for EGF and TGF-beta in mediating the steroid responsiveness of stromal specific MMPs. Information from our studies should provide insight into the language by which cells communicate at the local tissue level, and how the failure of normal control systems could lead to abnormal conditions such as infertility or cancer.
