ANALYSIS OF MESSENGER-RIBONUCLEIC-ACID AND PROTEIN FOR THE LIGANDS AND RECEPTORS OF THE PLATELET-DERIVED GROWTH-FACTOR SIGNALING PATHWAY INTHE PLACENTA, EXTRAEMBRYONIC MEMBRANES, AND UTERUS DURING THE LATTER HALF OF MURINE GESTATION

Previous investigation of ligand and receptor messenger RNA (mRNA) exp ression implicated the platelet-derived growth factor (PDGF) pathway a s a participant in the maintenance of pregnancy and fetal development during the first half of murine gestation. We extended these studies u sing Northern and in situ RNA hybridization and immunohistochemical de tection of protein to evaluate the expression kinetics and cell-specif ic localization of PDGF-A, PDGF-B, PDGF alpha-receptor, and PDGF beta- receptor in mouse placenta, extraembryonic membranes, and uterus durin g the second half of gestation (days 9.5-18.5). Northern blotting expe riments reveal that mRNAs for the PDGF signaling components exhibit un ique time-dependent and tissue-specific expression in the placenta and uterus, being progressively and coordinately up-regulated as gestatio n proceeds. Cell-specific localization of mRNA and protein by in situ hybridization and immunohistochemistry demonstrates widespread express ion in multiple cell types of the placenta, gravid uterus, and extraem bryonic membranes. Abundant PDGF protein and mRNA expression is exhibi ted in the nucleated fetal erythroid progenitor cells that originate i n the extraembryonic membranes and circulate throughout the developing conceptus. Our data together with those of previous studies demonstra te that PDGF ligands and receptors are globally expressed in many cell types within fetal and maternal tissues during murine gestation and, thus, imply a potential role for PDGF in fetal development and materna l-fetal interactions.