The regulation of collagen in fetal skin wounds: mRNA localization and analysis

The deposition of collagen in fetal skin wounds has been shown in several animal models. The authors used a radiolabeled RNA antisense probe, complementary to the mRNA for the alpha-1 chain of human procollagen type I, to assess regulation of this collagen species in fetal and adult rabbit wounds. Dorsal skin wounds were placed on fetal and maternal animals at the beginning of the third trimester, and were harvested 3, 5, and 7 days later. In situ RNA RNA hybridization was performed on suitable specimens, and morphometric analysis was carried out with a computerized LECO image analyzer. Fetal wounds exhibited an inflow of mesenchymal cells that produced collagen type I at levels higher than the surrounding tissue; this activity was highest on days 3 and 5 after wounding. Adult wounds had increased fibroblast presence by day 7, producing collagen type I at levels higher than those of adjacent unwounded tissue. Morphometric analysis of the signal produced by in situ hybridization and of the number of cells producing the signal in a given field showed that fetal wounds appear to produce collagen type I by an increase in the number of cells in the area of the wound-not by induction of the gene for procollagen type I. In contrast, adult wounds had both fibroblast migration and induction of procollagen type I mRNA synthesis. These findings imply multilevel regulation of collagen production in the adult and posttranslational regulation in the fetus.