In vitro and in vivo analysis of the inability of fetal rabbit wounds to contract.

Fetal rabbit wounds that are sutured show excellent repair without obvious scarring. In contrast, an unsutured wound in a rabbit fetus does not close, and it appears that the process of wound contraction does not occur. Experiments were carried out to illustrate the mechanisms responsible for the noncontraction of open fetal rabbit wounds. Results showed that the lack of wound contraction was not an artifact caused by rapid fetal growth. With regard to the ability of cultured fetal fibroblasts to show cytoplasmic muscle-induced cell contraction, we found that, in cultured fetal fibroblasts, cell contraction was induced by adenosine triphosphate. Contractile abilities of fetal-derived fibroblasts were equivalent to those of adult-derived fibroblasts. The fetal fibroblasts also demonstrated the generation of superior contractile activity when examined in a fibroblast-populated collagen lattice model. Finally, the ability of amniotic fluid to alter wound contraction was addressed by means of the fibroblast-populated collagen lattice in vitro model. Increasing concentrations of amniotic fluid inhibited fetal fibroblast lattice contraction. Therefore, rabbit amniotic fluid contains an inhibitor that may be partially responsible for the noncontraction of fetal rabbit wounds in utero.