Differential expression of F-actin in in utero fetal wounds.

Fetal skin possesses the capacity to heal a wound by a process of regeneration rather than repair, resulting in the absence of scar formation. The actin cytoskeleton may be involved in this process of scar-free wound healing. The effect of wounding on the expression of contractile filamentous actin (F-actin) was investigated in utero in mice between embryonic day 16 (E16) and embryonic day 18 (E18). Increased F-actin staining in the epidermis of the E16 fetal wounds was observed as early as 3 hours post-wounding, peaking in intensity after 24 hours. By 48 hours the intensity of staining had returned to background levels. In marked contrast, E18 fetal wounds did not show increased epidermal F-actin fluorescence, instead increased staining was observed in cells lying perpendicular to the wound margin within the dermis. This developmental switch from epidermal actin expression in "scar-free" fetal wounds to dermal actin expression in late "scar-forming" gestation wounds may be important in fetal wound contraction and scar-free wound repair.