A study on the extracellular matrix in the artificially created cleft lip wound healing of rabbit fetuses

Yang, Won Sik; Baek, Seung Hak

Abstract

Adult wound healing is accompanied with inflammation and eventual scar formation, whereas fetal wounds heal rapidly by mesenchymal proliferation without significant inflammatory cell participation and with minimal or no scar formation. The cellular mechanisms underlying these differing forms of wound healing are unknown but the extracellular matrix, through its effects on cell function, may play a key role. Therefore the purpose of this study is to investigate the spatial and temporal deposition of several component of extracellular matrix, which are known to be involved with scar formation, in the artificially created cleft lip wound healing of fetuses. The author had undergone hysterotomy and created cleft lip-like defects on fetuses of New Zealand White Rabbit in mid-third trimester(24 days). Fetuses were divided into the repaired group, the unrepaired group and the sham-operated control group. At 1, 2, 3, 5, 7 days after procedure, fetuses were obtained by Caeserean section. After documenting the viability of fetuses, they were photographed to compare size and facial morphology and sectioned for histological examination by H & E stain and spatial and temporal deposition of collagen type I. III, IV, V and fibionectin, laminin by immunohistochemical method. The findings are summarized as follows: 1. There were lack of inflammation in the repaired and the unrepaired group during experimental periods. 2. The reepithelialization of the unrepaired group was slower than that of the repaired group. 3. Collagen I, III, V were found from post-op. third day. There were no difference of distribution in the control, the repaired and the unrepaired group. Collagen types I, III, V were present in all groups with restoration of the normal collagen pattern in the fetus. This implies that lack of scarring in fetal wounds is due to the difference of collagen organization pattern within wound and not simply lack of collagen formation. 4. Collagen IV was slightly increased at post-op. third day and decreased after post-op, fifth day. Eventually there were no differences in the control, the repaired and the unrepaired group. Laminin was found at post-op. fifth day and maintained staining density until post-op. seventh day. There were no differences in the control, the repaired and the unrepaired group. According to staining of laminin and collagen type IV in epithelial basement membrane, formation of epithelial basement membrane was not completed until reepithelialization was finished. 5. According to staining of laminin and collagen type IV, there were no increase of neovascularity in the repaired and the unrepaired group. 6. Fbbronectin was increased until post-op. third day at fibrin clot, wound base and margin and decreased after post-op. fifth day. Eventually, there were no differences in the control, the repaired and the unrepaired group, So it implies fibronectin plays a role as provisional matrix for fetal wound healing