Tissue repair in the fetal intestinal tract occurs with adhesions, fibrosis, and neovascularization

Abstract

Cutaneous wound healing in the fetus can occur in a nonfibrotic, regenerative manner. However, other fetal tissues such as bone and stomach heal with scar formation. In light of potential ramifications for adult hollow visceral scarring (biliary and intestinal strictures), this study was undertaken to determine if tubular visceral tissue repair in the fetus is regenerative or fibrotic. Fetal rabbits underwent laparotomy on day 24 of gestation, during which a controlled intestinal enterotomy was created and suture repaired immediately using microsurgical techniques. Maternal rabbits and adult male rabbits also underwent enterotomy and repair. After 5 days all animals were sacrificed and the wounds analyzed histologically by a pathologist in a blinded fashion. All animals demonstrated a similar degree of peri-intestinal adhesion formation. Fetal and maternal wounds contained fibroblastic and smooth muscle cell proliferation, mild inflammatory infiltration, and new blood vessel formation. The male adult wounds demonstrated a more pronounced fibrovascular healing response. Immunohistochemical staining for CD31 (endothelial cell marker) was quantitated on a scale of 0 to 4+, indicating degree of neovascularization. The mean scores for the fetal and maternal groups were similar (1.70 +/- 0.68 and 1.23 +/- 1.07 respectively), but were significantly greater for male adults (2.93 +/- 0.12; p = 0.001 by analysis of variance). The results of this study indicate that hollow visceral tissue repair in the fetal rabbit intestine occurs in a similar fibrotic manner as adult healing. This provides further evidence that regenerative healing in the fetus is not ubiquitous. Differences in the degrees of fibrosis and neovascularization between adult male and pregnant female wounds deserve further investigation.