IMMUNOCYTOCHEMICAL LOCALIZATION OF GROWTH-FACTORS AND INTERMEDIATE FILAMENTS DURING THE ESTABLISHMENT OF THE PORCINE PLACENTA

The immunocytochemical. localization of insulin-like growth factor I ( IGF-I) and platelet-derived growth factor A (PDGF-A) chain ligands, PD GF-chain receptors, and the intermediate filaments cytokeratin, desmin , and vimentin in the tissue reorganization and development during the establishment of the porcine epitheliochorial placenta was studied at Light and electron microscopic levels in sections of endometrial and/ or placenta of gilts during early pregnancy up to day 40 postmating. T he endometrial epithelia (surface and glandular) as well as the tropho blast showed PDGF-A and IGF-I labelling. The only temporal difference was seen regarding IGF-I labelling, this being more uniform in the gla nds during precontact and early contact stages (days 7-12) compared to later stages. Cytokeratin labelling was conspicuous in all epithelia, including the trophoblast. The endometrial stroma showed strong label ling for the PDGF receptors and the intermediate filament vimentin, st aining being enhanced along with the increase in the vascular bed duri ng the establishment of the placenta. The maternal endothelium immunor eacted to IGF-I, to both PDGF-A and PDGF receptors, to vimentin and to von Willebrand factor (Factor VIII). Desmin was also expressed in the capillary bed underneath the maternal surface epithelium. In larger b lood vessels, desmin was detected in the smooth muscle layer but not i n the endothelium. The vascular smooth muscle also reacted with IGF-T, PDGF-A, and PDGF-receptor antibodies. The results suggest the involve ment of both growth factors, IGF-I and PDGF, in the early nutrition of the pig embryo and the tissue reorganization that encompasses placent ation. IGF-I appears to be related to the secretory tissue compartment (formation of histotrophe), whereas PDGF might play a role in the reo rganization of the stroma, particularly during placental angiogenesis. Desmin and van Willebrand factor immunolabelling appears to be useful to monitor the development of the subepithelial capillary bed in the porcine placenta. (C) 1997 Wiley-Liss, Inc.