Background: Atopic dermatitis (AD) and psoriasis are the two most common chronic inflammatory skin diseases. Both of these diseases have distinct clinical findings and specific inflammatory cell infiltrates. Previous reports have focused individually on one or two genes or gene products in the lesions of both skin diseases. However, they have not captured the complex gene expression that must occur to induce specific cellular infiltrates in the skin lesions of these two diseases. DNA microarray studies allow the simultaneous comparison of thousands of messenger RNAs that may identify the disease-specific pattern of tissue inflammatory responses.
Objective: To compare the complex gene expression pattern of AD versus psoriasis skin lesions.
Methods: RNA was extracted from skin biopsy specimens of 6 patients with AD and 7 patients with psoriasis and analyzed with the use of Hu-U95Av.GeneChip microarrays. To confirm GeneChip results, real-time PCR of selected genes were performed.
Results: In AD skin, a total of 18 genes including the CC chemokines, CCL-13/MCP-4, CCL-18/PARC, and CCL-27/CTACK showed a statistically significant, >2-fold increase of gene expression compared with psoriasis. In psoriasis skin, a total of 62 genes including CCL-4/MIP-1beta, CCL-20/MIP-3alpha, CXCL-2/GRO-beta CXCL-8/IL-8, and CXCR2/IL-8R showed a >2-fold increase of gene expression compared with AD skin. Real-time PCR confirmed several of these GeneChip results.
Conclusions: These results show a very distinctive gene expression pattern in AD as compared with psoriasis that may explain several features of AD and psoriasis including the specific inflammatory cell infiltrates observed in these disorders, that is, T(H)2 cells, eosinophils, and mast cells in AD and T(H)1 cells and neutrophils in psoriasis. Such observations may contribute to a characteristic "signature" for these two skin diseases.