Scarless wound healing in the mammalian fetus.

Fetal wound healing is a remarkable process that is fundamentally different than postnatal healing. Healing of primarily closed, linear wounds occurs rapidly and without scarring. In late gestational age fetal sheep, a transition to adult-like healing occurs as evidenced by minimal scar formation. Acute inflammation is not involved, fibroblast recruitment and proliferation is minimal, the matrix of the wounds is enriched with HA and collagen deposition is highly organized so that scarring is minimal or nonexistent. Open wounds in several species do not contract, an observation that may be because of an inhibitor of contraction in amniotic fluid. The underlying mechanisms that regulate fetal wound repair are currently not well understood. An altered supply or activity of growth factors may be instrumental. Fibroblasts may preferentially produce HA secondary to a factor present within the fetal system, and HA may influence cellular and matrix events within the wound. As greater knowledge of the biologic factors of scarless healing in the fetus is gained, applications to abnormal adult healing may be developed. As the age of fetal surgery is approaching, it is essential to understand the injury response in these new patients.