Changes in insulin-like growth factor-binding protein-3 messenger ribonucleic acid in endothelial cells of the human corpus luteum: A possible role in luteal development and rescue

In the human menstrual cycle, extensive angiogenesis accompanies luteinizat ion; and the process is physiologically important for corpus luteum (CL) fu nction. During luteolysis, the vasculature collapses, and the endothelial c ells die. In a conceptual cycle, the CL persists both functionally and stru cturally beyond the luteoplacental shift. Although luteal rescue is not ass ociated with increased angiogenesis, endothelial survival is extended. Desp ite the central role of the luteal vasculature in fertility, the mechanisms regulating its development and demise are poorly understood. There is incr easing evidence that insulin-like growth factors (IGFs) and their binding p roteins (IGFBPs) may be important effecters of luteal function. Here, we ha ve found that IGFBP-3 messenger RNA is expressed in the endothelium of the human CL and that the levels of message change during luteal development an d rescue by human CG. The signal was strong during the early luteal phase, but it showed significant reduction during the mid and late luteal phases. Interestingly, administration of human CG caused a marked increase in the l evels of IGFBP-3 messenger RNA in luteal endothelial cells that was compara ble to that observed during the early luteal phase. We conclude that endoth elial cell IGFBP-3 expression is a physiological property of the CL of mens truation and pregnancy. These observations raise the intriguing possibility that the regulated expression of endothelial IGFBP-3 may play a role in co ntrolling angiogenesis and cell responses in the human CL by autocrine/para crine mechanisms.