The Functions and Regulation of Cell Populations Comprising the Corpus Luteum during the Ovarian Cycle

This chapter discusses the functions and regulation of cell populations in the corpus luteum during the ovarian cycle. Significant advances in research are increasing the understanding of cell-cell interactions and the role of local factors in mediating or modulating the actions of luteotropic and luteolytic hormones in the corpus luteum. For example, it is now clear that recently discovered endothelial-specific growth factors (for example,vascular endothelial growth factors [VEGFs] and angiopoietins [Angs]) are produced by luteinizing cells in response to the luteinizing hormone (LH) surge and play a vital role in the neovascularization and development of the functional corpus luteum. Conversely, it appears that the endothelin (ET-1) system, involving endothelial synthesis of ET-1 precursor, luteal cell activation, and ET-1 receptor signaling, plays a role in prostaglandin (PG) F_2α-induced luteal regression. In addition, resident or migrating immune cells may play a vital role in the tissue reorganization that occurs during development and dissolution of the corpus luteum; again, chemokines (for example,monocyte chemotactic protein-1 [MCP-1]) produced by luteal and nonluteal cells appear to promote these processes. Nevertheless, significant differences between species likely existin cell-cell interactions and roles of local and hormonal factors.