ONTOGENY OF THE SKIN AND THE TRANSITION FROM SCAR-FREE TO SCARRING PHENOTYPE DURING WOUND-HEALING IN THE POUCH YOUNG OF A MARSUPIAL, MONODELPHIS-DOMESTICA

The marsupial Monodelphis domestica provides a versatile model for the study of ''fetal'' wound healing. The pouch young of this species hav e been used to perform a systematic histological study of wound healin g and skin development throughout pouch life; from Pouch Day 0 to Pouc h Day 30 with comparisons drawn against adults. We have demonstrated t hat pouch young heal without macroscopic scars if wounded before Pouch Day 9 and that a transition into a scarring healing phenotype occurs around the ninth pouch day. The inflammatory reaction of wounds and as pects of skin differentiation such as dermal collagen organisation, ad ipose layer development, hair follicle growth, and epithelial maturati on have been documented using simple ranking scales to highlight trend s through pouch life. Inflammation was noted to become prominent after Pouch Day 9. There was also a general temporal correlation between th e other aspects of differentiation and the transition into a scarring phenotype. It is concluded that although fetal wounds may have differe nt cytokine profiles due to the differences of inflammatory reaction c ompared to adults, other aspects of skin development play a role in de termining the healing phenotype. (C) 1995 Academic Press, Inc.