The mRNA expression and promoter methylation status of the p16 gene in colony-forming cells with high proliferative potential in patients with psoriasis.

BACKGROUND: Psoriasis is a chronic and relapsing inflammatory disease of the skin associated with various immune abnormalities. It is tempting to speculate that the dysfunctional immunity may influence the haematopoietic microenvironment or haematopoiesis in psoriasis. However, direct evidence of involvement of bone-marrow haematopoietic cells in the pathogenesis of psoriasis is lacking. AIM: To investigate the proliferative activity of haematopoietic cells of patients with psoriasis and a link between the promoter methylation status and transcriptional activity of the p16 gene and the colony-forming ability of high proliferative potential colony-forming cells (HPP-CFCs).
METHODS: Marrow mononuclear cells were isolated from the bone marrow of patients with psoriasis and normal controls by density gradient centrifugation. A comparison of HPP-CFC colony formation counts between patients with psoriasis and normal controls was carried out by colony-forming assays of HPP-CFCs in methylcellulose semisolid culture medium in vitro. Subsequently, genomic DNA and RNA in HPP-CFCs were isolated, and mRNA expression and p16 promoter methylation status were studied by reverse transcriptase PCR and methylation-specific PCR (MSP), respectively.
RESULTS: In comparison with normal controls, patients with psoriasis showed less HPP-CFC colony formation in the methycellulose semisolid culture system, and showed upregulated mRNA transcriptional level and downregulated promoter methylation of p16.
CONCLUSIONS: Our data demonstrate for the first time the abnormal proliferative activity of haematopoietic cells in patients with psoriasis and a profound link between the promoter methylation status and transcriptional activity of p16 and the colony-forming ability of HPP-CFCs, suggesting that haematopoietic cells are involved in psoriasis.