Expression of matrix metalloproteinase 8 in the serum and skin lesions of patients with psoriasis vulgaris

Objective: To assess the role of matrix metalloproteinase 8 in the inflammation of psoriasis vulgaris (PV). Methods: According to the psoriasis area and severity index (PASI), twenty PV patients were grouped into mild (n=6), moderate (n=6), and severe (n=8) groups. Serum levels of MMP-8, measured with ELISA, were compared among PV groups and the controls (n=12), while expression levels of MMP-8 mRNA were compared between lesional sites and their adjacent normal skin by qPCR. Localization of MMP-8 positive cells in the skin was determined by immunohistochemistry. Results: Serum MMP-8 concentration was significantly lower in the mild PV than in both the severe PV (t=2.69, P=0.020) and the controls (t=2.54, P=0.022). Expression levels of MMP-8 mRNA in the lesional sites were significantly higher than that in their adjacent normal skins (t=2.91, P=0.009). Moreover, expression levels of MMP-8 mRNA were significantly higher in the lesions of severe PV than that of mild (t=3.45, P=0.005) and moderate (t=2.74, P=0.018) PV. MMP-8 positive cells were mainly localized in the basal and spinous layers of the lesional skin, while in their adjacent normal skin, MMP-8 positive cells mainly located in the basal layer. In the dermis, high intensity of MMP-8 staining was observed in endothelial cells of papillary vessels. Conlusions: Increased expression of MMP-8 in inflammatory site of PV suggests the involvements of MMP-8 in immunoregulation and pro-angiogenesis.