Background: The fibroblast growth factors (FGFs) and their receptors have a wide range of biologic actions in a variety of systems. The best characterized are the prototypical acidic and basic FGFs, both of which have the property of binding to the flg gene product, fibroblast growth factor receptor-1/FGFR-1. Although much is known at the molecular level, the available information about the in vivo distribution of FGFs and their receptors in human tissues is limited. Detailed characterization of the spatial distribution of ligands and receptors is a necessary prerequisite for understanding their function.
Experimental design: Using immunohistochemical techniques, we have defined the tissue specific cellular location of both FGFR-1 and basic and acidic FGFs in serial sections of a broad range of normal human adult tissues. Immunodetection was performed using highly specific polyclonal antibodies to FGFR-1, acidic FGF, and basic FGF and the avidin-biotin immunoperoxidase method.
Results: Immunoreactive acidic and basic FGFs were present in almost all tissues examined. A distinct spatial pattern of distribution of these ligands was observed in the kidney, skin, liver, ureter, and the vasculature. FGFR-1 expression tended to be confined to the tissue microvasculature. Interestingly, marked numbers of FGFR-1 reactive vessels were observed in the stomach, salivary glands, lung, and appendix. Intense FGFR-1 positivity was observed in the basal epithelial cell layer of the cervix, palatine tonsil, and respiratory tract as well as breast myoepithelial cells, and the pitutary gland.
Conclusions: We have been able to define the distribution of FGFR-1 and its ligands in normal human tissues. The results will be useful for determining the function of these growth factors and their receptors under both normal physiologic and pathologic conditions.