Fetal cleft lip repair in rabbits: histology and role of hyaluronic acid.

This study examines the histologic and biochemical features of wound healing in a cleft lip model in the mid-third-trimester fetal rabbit. At days 1, 2, and 4 after the procedure, control, unrepaired, and repaired fetal heads were obtained, sectioned, and stained for histologic examination. The localization of hyaluronic acid in the wound was documented using a cartilage-derived hyaluronic acid-binding protein. In both repaired and unrepaired wounds, the fetal cleft healed without inflammatory cell infiltration or scar formation. Six months after birth, the repaired cleft showed complete regeneration of muscle across the wound and the collagen fibers were of normal density and orientation. Decreased hyaluronic acid deposition was observed in unrepaired clefts as compared with adjacent tissue; no such difference was detected in repaired clefts. Our findings support the hypothesis that a cleft lip repaired in utero heals without the scarring that accompanies postnatal repair. This may explain the lack of maxillary growth restriction after in utero cleft lip repair.