The effect of suppressing discoidin domain receptor expression on keloid formation and proliferation .

UNLABELLED  BACKGROUND Discoidin domain receptors (DDR) with tyrosine kinase activity have been identified as novel receptors for modulating collagen production and organization in scar tissue. The purpose of this study was to explore the effect of blocking discoidin domain receptor 1 (DDR1), signaling of keloid fibroblast cells on the inhibition of keloid formation, and proliferation, by means of gene therapy. METHODS The expression of DDR1 in keloid tissues was investigated by immunohistology and the expression of DDR1 protein in keloid fibroblasts was examined by Western blot analysis. Keloid dermal fibroblasts were infected in vitro with modified phosphorothioate and liposome-encapsulation DDR1-antisense oligodeoxynucleotide (ASODN). Northern blot was used to analyze gene expression of DDR1 in infected keloid dermal fibroblasts and the effect on type I and type III collagen gene expression. Extracellular matrix production in infected fibroblasts was analyzed by [3H] proline incorporation. RESULTS In keloid tissues, the expression of DDR1 was observed to be widely and strongly distributed. The expression of DDR1 protein was also highly increased in keloid fibroblasts compared to normal skin fibroblasts. This was markedly downregulated in lipid-encoding DDR1-ASODN infected fibroblasts compared to lipid encoding DDR1-NSODN infected fibroblasts and lipid-infected fibroblasts. Type I and type III collagen gene expression and extracellular matrix production also were downregulated markedly in DDR1 ASODN infected fibroblasts. Moreover, the ratio of type I and type III collagen was significantly improved. CONCLUSION An intrinsic functional difference exists between normal human dermal and keloid fibroblasts in terms of higher DDR1 gene expression in keloid fibroblasts. The quality and quantity of collagen can be improved by downregulating the expression of DDR1 using ASODN. This intervention is potentially useful in controlling fibrosis and keloid formation in clinical settings. .