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.