The role of periostin and thymic stromal lymphopoietin in psoriasis vulgaris and their clinical correlations

Psoriasis is a chronic, inflammatory, immüne-mediated, and genetically predisposed multisystemic disease with variable prevalence. Although it can occur at any age, it typically exhibits a bimodal age distribution. The disease pathogenesis primarily involves the Th1/Th17 axis. In recent years, studies have begun to explore the roles of Th2-related molecules such as thymic stromal lymphopoietin (TSLP) and periostin (POSTN) in the pathogenesis of psoriasis. POSTN is an extracellular matrix protein implicated in various physiological and pathological processes, with a well-established role in allergic diseases like atopic dermatitis. TSLP is a key cytokine of the Th2 pathway and plays a central role in the development of allergic inflammation. Based on this background, our study aimed to investigate the roles of these molecules in psoriasis pathogenesis and to evaluate their associations with clinical parameters. The study included 35 patients with psoriasis vulgaris (23 males, 12 females) who had not received systemic treatment within the past 6 months or topical treatment within the past month, along with 35 age- and sex-matched healthy controls without allergic disease. Serum samples were obtained from all participants, and lesional and perilesional skin biopsies were collected from the patient group. We evaluated the expression levels of TSLP and POSTN, which are associated with Th2 responses, along with IFN-γ, TNF-α, IL-17, IL-22, and IL-23 key mediators of the Th1/Th17 axis—in lesional and non-lesional skin, as well as their serum levels in both groups. The results were analyzed in relation to demographic, physical, and clinical parameters using appropriate statistical methods. There were no significant differences between the patient and control groups in terms of age, sex, smoking status, or body mass index. Serum levels of POSTN, IL-22, IL-23, and IFN-γ were significantly higher in the patient group compared to controls. Serum POSTN levels also showed significant variation across clinical subgroups and were positively correlated with serum IL-22 levels. In lesional skin, POSTN expression was negatively correlated with IL-17 expression and positively correlated with IL-23 expression. A negative correlation was also observed between TSLP and IL-23 expression in lesional skin. When comparing lesional and non-lesional tissues, IL-17 expression was significantly higher in non-lesional skin, whereas IL-23 expression was significantly higher in lesional skin. Additionally, lesional POSTN expression was positively correlated with IL-23 expression. Among the molecules studied, serum POSTN demonstrated the highest diagnostic accuracy in ROC analysis, indicating its potential as a serum biomarker. To our knowledge, this is the first study to concurrently evaluate both POSTN and TSLP in patients with psoriasis, examining their expression at both serum and tissue levels. These findings are believed to contribute novel insights into the pathogenesis of psoriasis. In particular, they may help pave the way for the development of personalized therapeutic strategies and enhance our understanding of the underlying disease mechanisms. Keywords: Periostin, Psoriasis Vulgaris, Thymic Stromal Lymphopoietin