Spatial expressions of fibronectin and integrins by human and rodent dermal fibroblasts

Summary Background  Human skin shows various morphological characteristics, depending on the body site. As these distinct phenotypes have been explained on the basis of the variance in epidermal keratinocytes and the presence of skin appendages, the spatial distinction of the dermal components has not been fully elucidated. Objectives  To identify and characterize the profiles of mRNAs that are abundantly or specifically expressed by fibroblasts derived from trunk skin, but not from palmoplantar skin or oral mucosa. Methods  In order to identify the distinct mRNA expression by trunk skin fibroblasts, a subtraction cDNA screening was performed first, followed by Northern blotting, Western blotting and immunohistochemistry for cultured human and rat dermal fibroblasts and those skin tissues. Finally, whole mount in situ hybridization (WISH) was performed to examine the differences in the expression of the corresponding gene during the developmental stage of mouse embryos. Results  We identified three cDNA clones encoding fibronectin (FN), pregnancy-specific β1-glycoprotein 5 and β-actin, respectively, whose mRNAs were abundantly or specifically expressed by trunk skin fibroblasts. FN and some integrins were further confirmed to be expressed more selectively in human and rat trunk skin fibroblasts, both in terms of the RNA and the protein levels, compared with the fibroblasts derived from plamoplantar skin and oral mucosa. WISH demonstrated that FN was localized around the hair follicles of mouse embryos. Conclusions  FN, one of most potent extracellular matrix molecules, was demonstrated to be spatially transcribed depending on the body sites. The distinct expression of FN was suggestive of the essential commitment in the process of cutaneous development and morphogenesis of appendages originated from hair germ. The paucity of FN in palmoplantar skin and oral mucosa might explain the characteristics of these skin phenotypes.