[Experimental approach to leiomyomatosis peritonealis disseminata--progesterone-induced smooth muscle-like cells in the subperitoneal nodules produced by estrogen (author's transl)].

Our previous report attempted to verify the pathogenesis and histogenesis of leiomyomatosis peritonealis disseminata (LPD) resulted in the production of multiple subperitoneal nodules simulating the disseminated pattern of LPD, when guinea pigs were treated with various doses of estradiol benzoate (E) [40, 80, 100, 200 micrograms/day, thrice a week, intramuscular injection (i.m.)] for a minimum of three months. Ultrastructurally, the nodules were considered to be composed of the cells resembling fibroblast. However, the nodules of clinically observed LPD were considered to contain not only fibroblasts but also smooth muscle and decidua-like cells. Therefore, for the purpose of inducing smooth muscle and decidua-like cells in the previously prepared nodules in the guinea pig, progesterone treatments were added. Guinea pigs pretreated with E (100 micrograms/day, thrice a week, i.m.) for three months followed by the combination treatment E and progesterone (P) [0.5, 1.0 mg/day, once a week, i.m.] for one to three months produced the nodules similar to that produced by estrogen alone. Ultrastructurally, these nodules were considered to be composed of the cells resembling smooth muscle and decidual cell. From these results, I assumed that estrogen differentiates and proliferates the cells of the features of fibroblast-like cells from subcoelomic mesenchyme which have further capacity to differentiate into smooth muscle and endometrial stroma, and they are differentiated into smooth muscle-like cells and decidua-like cells under both influences of estrogen and progesterone, resulting in the production of multiple subperitoneal nodules.