Human endometrial peptides: a review of their potential role in implantation and placentation

This paper reviews human endometrial peptide synthesis and discusses the biological function of these peptides in relation to implantation and placentation. Despite the substantial literature on quantitative and qualitative peptide synthesis by the endometrium, it has not been possible to define the function of most of these substances. Various aspects of endometrial morphology, especially the endometrial leukocytes, are discussed in an attempt to relate cellular structure and function. A number of serum proteins are produced by the endometrial glandular epithelium and may play a role in early embryo development. Extracellular matrix proteins produced by stromal cells are important for endometrial structure and integrity but also provide a site for trophoblast attachment. Several hormones and binding proteins are also produced by stromal cells and probably influence endometrial metabolism. Complement factors and secretory component may have a role in maintaining a sterile intrauterine environment. Many other endometrial proteins have been less well characterized and their role in endometrial physiology at present remains uncertain. Perhaps the most exciting advance has been the realization that a number of peptide regulatory factors (cytokines and growth factors) are not only produced by the endometrium but play an integral part in the mediation of oestrogen-induced growth and differentiation of the endometrium and with the local metabolic and physiological processes.