DISTRIBUTION OF FIBROBLAST GROWTH-FACTOR (FGF)-2 AND FGF RECEPTOR-1 MESSENGER-RNA EXPRESSION AND PROTEIN PRESENCE IN THE MIDTRIMESTER HUMANFETUS

Fibroblast growth factors (FGF) are known to have key roles in embryon ic growth and morphogenesis, but their presence and contributions to f etal development are unclear. In particular, little information exists as to the relevance of FGF and their specific receptors to human feta l development. We studied the anatomical distribution of messenger RNA encoding FGF-2 and one of its high affinity receptors, FGFR1, using i n situ hybridization in a variety of human fetal tissues in early seco nd trimester. Corresponding protein distributions were determined by i mmunohistochemistry. Both FGF-2 and FGFR1 mRNA and proteins were found to be present in every organ and tissue examined, but with defined ce llular localizations. In skeletal muscle, both FGF-2 and FGFR1 mRNA an d peptides were present in differentiated fibers, and both co-localize d to proliferating chondrocytes of the epiphyseal growth plate. FGF-2 and FGFR1 mRNA and peptides were also present within cardiac or gastro intestinal smooth muscle. Within the gastrointestinal tract FGF-2 mRNA and peptide were located in the submucosal tissue, whereas FGFR1 was expressed within the overlying mucosa. Similarly, in skin, FGF-2 was e xpressed within the dermis whereas FGFR1 mRNA and peptide were most ap parent in the stratum germinativum of the epidermis. In kidney and lun g, FGFR1 mRNA was located in the tubular and alveolar epithelia respec tively, whereas FGF-2 was expressed in both epithelial and mesenchymal cell populations. Both growth factor and receptor were widespread in both neuroblasts and glioblasts in the cerebral cortex of the brain. I mmunoreactivity for FGF-2 and FGFR1 was seen in all vascular endotheli al cells of major vessels and capillaries. Within the skin, kidney, lu ng, and intestine FGF-2 immunoreactivity was found in basement membran es underlying epithelia, and was associated with the extracellular mat rix and plasma membranes of many cell types. The results show that FGF -2 and one of its receptors are widely expressed anatomically in the m id-trimester human fetus.