Gene profiling of keloid fibroblasts shows altered expression in multiple fibrosis-associated pathways

Abstract

Keloids are benign tumors of the dermis that form during a protracted wound healing process. Susceptibility to keloid formation occurs predominantly in people of African and Asian descent. The key alteration(s) responsible for keloid formation has not been identified and there is no satisfactory treatment for this disorder. The altered regulatory mechanism is limited to dermal wound healing, although several diseases characterized by an exaggerated response to injury are prevalent in individuals of African ancestry. We have observed a complex pattern of phenotypic differences in keloid fibroblasts grown in standard culture medium or induced by hydrocortisone (HC). In this study Affymetrix-based microarray was performed on RNA obtained from fibroblasts cultured from normal scars and keloids grown in the absence and presence of HC. We observed differential regulation of approximately 500 genes of the 38,000 represented on the Affymetrix chip. Of particular interest was increased expression of several IGF-binding and IGF-binding-related proteins and decreased expression of a subset of Wnt pathway inhibitors and multiple IL-1-inducible genes. Increased expression of connective tissue growth factor and insulin-like growth factor binding protein-3 was observed in keloid fibroblasts only in the presence of HC. These findings support a role for multiple fibrosis-related pathways in the pathogenesis of keloids.

Figure 1

Unsupervised hierarchical clustering was performed on 19 samples of normal and keloid fibroblasts grown with and without hydrocortisone, using a subset of genes (n = 7303) whose expression varied by at least two-fold relative to the average normal strain in at least two of the 19 samples. Gene expression of cell strains grown in medium with and without (control) 1.5 μM hydrocortisone supplementation fell into four distinguishable groups relative to gene expression in the average normal strain grown in control medium. From right to left are 5 normal strains in control medium, 4 normal strains with hydrocortisone (one strain lost in processing), 5 keloid strains in control medium, five keloid strains with hydrocortisone. Red indicates increased expression, blue indicates reduced expression, and yellow indicates no difference in expression.