Analysis of hypertrophic and normal scar gene expression with cDNA microarrays

Hypertrophic scar is one form of abnormal wound healing. Previous studies h ave suggested that hypertrophic scar formation results from altered gene ex pression of extracellular matrix molecules. A broadscale evaluation of gene expression in hypertrophic scars has not been reported. To better understa nd abnormalities in hypertrophic scar gene expression, we compared messenge r RNA expression in hypertrophic scars, normal scars, and uninjured skin wi th the use of complementary (c)DNA microarrays. Total RNA was extracted fro m freshly excised human hypertrophic scars, normal scars, or uninjured skin and reverse transcribed into cDNA with the incorporation of [P-33] deoxycy tidine triphosphate. The resulting radioactive cDNA probes were hybridized onto cDNA microarrays of 4000 genes. Hybridization signals were normalized and analyzed. In the comparison of tissue samples, mean intensities were ca lculated for each gene within each group (hypertrophic scars, normal scars, and uninjured skin). Ratios of the mean intensities of hypertrophic scars to normal scars, hypertrophic scars to uninjured skin, and normal scars to uninjured skin were generated. A ratio that was greater than 1 indicated up regulation of any particular gene and a ratio that was less than 1 indicate d downregulation of any particular gene. Our data indicated that 142 genes were overexpressed and 50 genes were underexpressed in normal scars compare d with uninjured skin, 107 genes were overexpressed and 71 were underexpres sed in hypertrophic scars compared with uninjured skin, and 44 genes were o verexpressed and 124 were underexpressed in hypertrophic scars compared wit h normal scars. Our analysis of collagen, growth factor, and metalloprotein ase gene expression confirmed that our molecular data were consistent with published biochemical and clinical observations of normal scars and hypertr ophic scars. cDNA microarray analysis provides a powerful tool for the inve stigation of differential gene expression in hypertrophic scar samples and either uninjured skin or normal scars. Our data validate the use of this te chnology for future studies on gene expression during repair processes of n ormal and abnormal wounds.