KERATINOCYTE GROWTH-FACTOR AND ITS RECEPTOR IN THE RHESUS MACAQUE PLACENTA DURING THE COURSE OF GESTATION

Keratinocyte growth factor (KGF) is synthesized and secreted exclusive ly by mesenchymal cells, and acts through its receptor (KGFR) to stimu late epithelial proliferation. In vivo, KGF and KGFR comprise a mesenc hymal-epithelial cell paracrine system that can mediate epithelial cel l mitosis. In preliminary work, we noted that KGF was expressed in the rhesus monkey placenta, and we now report on the expression of placen tal KGF and KGFR mRNAs during the course of gestation in this species. In-situ hybridization revealed that during early gestation, KGF mRNA was strongly expressed in placental mesenchymal cells. These cells, wh ich were also immunoreactive for vimentin, were mainly located on the periphery of the mesenchymal cores of both anchoring and floating vill i. KGFR mRNA was expressed in the adjacent trophoblastic epithelium, w hich was immunoreactive for cytokeratin. In-situ hybridization reveale d that KGF mRNA expression was very high in the youngest placentae (34 -days gestation) and decreased gradually to minimal levels by late ges tation (157 days). Northern blot analysis indicated also that the KGF MRNA signal was strongest in early gestation samples and weakest by la te gestation. Analysis for KGFR mRNA by a reverse transcriptase-polyme rase chain reaction technique showed that KGFR mRNA expression could b e detected at all stages. However, in-situ hybridization indicated tha t KGFR mRNA expression was highest in early gestation placentae and le ast in the oldest placentae. Autoradiographs of frozen sections of pla centa that had been incubated with [I-125]KGF to detect receptor bindi ng showed that grain density over the trophoblast was highest in the y oungest and least in the oldest placentae. PCNA and Ki-67 expression f ollowed this same temporal trend. We conclude that the KGF/KGFR system may be important in proliferation of the placental trophoblast during early- to mid-pregnancy in rhesus monkeys. (C) 1996 W. B. Saunders Co mpany Ltd