In order to identify wound contraction and scar formation during palatal mucoperiosteal wound healing in growing rats, the temporal and spatial distribution of myofibroblasts and matrix components were determined immunohistochemically. Myofibroblasts were found in the mucosal part of the palatal wound tissue between 4 and 22 days, with the highest density at 8 days post-wounding. The number of collagen type I and type III fibers gradually increased until about 8 days postwounding, and thereafter the staining intensity of collagen type III decreased. At 60 days post-wounding there were more transversely oriented collagen type I fibers and less type III fibers and elastin present in the submucosa than in normal tissue. The results suggest that in this model wound contraction mainly takes place in the mucosa between 4 and 22 days postwounding. Furthermore, palatal wounds made in young rats heal with distinct scar tissue formation. Therefore, this model is useful to test the effects of therapies that aim to reduce wound contraction and scarring after cleft palate surgery.

Wound contraction and scar formation after cleft palate surgery impair maxillary growth and dentoalveolar development. Since myofibroblast numbers and scar formation are reduced by interferon-gamma (IFN-gamma) in the healing of dermal wounds, the hypothesis was tested that local administration of IFN-gamma reduces the numbers of myofibroblasts and the elevated amount of collagen during palatal mucoperiosteal wound healing. Standardized mucoperiosteal excision wounds were made in the palatal mucoperiosteum of young rats. Either IFN-gamma or vehicle alone (sham group) was repeatedly injected into the wound site between 4 and 29 days post-wounding. The results were compared with unmanipulated control wounds. Samples of wound tissue were prepared for biochemical and microscopic analysis. The hydroxyproline, sulfated glycosaminoglycan and DNA contents of the wound tissues were analyzed biochemically. The degree of re-epithelialization, tissue thickness, the numbers of myofibroblasts, and the amounts of elastin and collagen types I and III were evaluated on histological sections. Injection of vehicle alone affected almost all healing parameters, compared with the controls, and delayed the wound-healing process. IFN-gamma stimulated re-epithelialization and decreased the numbers of myofibroblasts when compared with vehicle-treated wounds. It also decreased the hydroxyproline and glycosaminoglycan contents of 60-day-old wound tissue, but the histological characteristics of scar tissue persisted. Therefore, IFN-gamma is able to reduce the numbers of myofibroblasts and the collagen content of scar tissue after palatal wound healing. It may be a promising pharmaceutical agent for the reduction of wound contraction and scarring after cleft palate surgery.

The objective of this study was to analyze the changes in tissue architecture and matrix composition during healing of palatal wounds of immature rats, and to compare this with rats of the same age that did not receive mucoperiosteal wounds. Wounds were made in the mucoperiosteum of the palate of 35-d-old rats. Samples were evaluated histologically at numerous points in time after wounding. The DNA, hydroxyproline and sulphated glycosaminoglycan contents were determined at 8, 15, 30, and 60 d post-wounding. Eight-d-old granulation tissue contained 43% less hydroxyproline, and 100% more glycosaminoglycans and cells than unwounded palatal tissue of 43-d-old rats. Sixty-d-old wounds contained 100% more DNA and 39% more hydroxyproline than unwounded tissue of 95-d-old rats. At the same time, densely packed and transversely aligned collagen fibres were present. It is concluded that palatal mucoperiosteal wounds made in 35-d-old rats heal with distinct scar tissue formation. The scar contains more collagen than non-wounded palatal tissue of rats of the same age. Therefore, this model may be of use for the development of therapies aiming to reduce palatal scarring.

No abstract

IFN-beta might be suitable to stimulate re-epithelialization but it does not reduce scar tissue formation in rat palatal wound healing. The injection of agents into palatal wounds might severely impair the healing process.