Expression of the insulin‐like and platelet‐derived growth factor genes in human uterine tissues

Abstract

The human uterus repeatedly exhibits cyclic biochemical and cytological changes during the reproductive period of life. These changes are the result of a well‐characterized endocrine network involving the hypothalamus, pituitary, and ovary. The exact nature of the mechanism(s) by which the sex steroids act on the uterus remains to be elucidated. Possible local mediators of hormonal action on the uterus include polypeptide growth factors. Using the method of RNA transfer blot hybridization, we have analyzed tissue samples from the cycling human endometrium and tissue samples of human myometrium and myometrial benign tumor (leiomyoma) for the presence of platelet‐derived growth factor (PDGF) and insulin‐like growth factor (IGF) RNA. All the uterine tissues examined possessed RNA for PDGF‐B chain and IGF‐I and ‐II. Two transcripts were observed for PDGF‐B chain, four were observed for IGF‐I, and eight were observed for IGF‐II. Overall, the relative abundance of PDGF‐B chain RNA was consistent in all of the uterine tissues examined. In contrast, IGF RNA relative abundance varied. IGF‐I RNA was highest in late proliferative stage endometrium, and IGF‐II RNA was highest in early proliferative stage endometrium. Both IGF‐I and IGF‐II RNAs were greater in amount in leiomyoma than in myometrium. The increased IGF‐I RNA in late proliferative–stage human endometrium correlates with the known elevation of estradiol secretion by the ovary and the increased concentration of uterine estradiol receptors during this stage of the menstrual cycle. Furthermore, these data are consistent with reports of increased IGF‐I RNA in the rat uterus in response to administration of estradiol. Elevated levels of IGF RNA in leiomyomas may be related to the genesis and/or progression of these myometrial tumors.