Normal dermal mesenchymal stem cells improve the functions of psoriatic keratinocytes by inducing autophagy.

Objective: Psoriasis is a chronic inflammatory skin disease characterized by excessive proliferation and abnormal differentiation of keratinocytes. Although stem cell-based therapies have shown promise in treating psoriasis, the underlying mechanisms remain unclear. This study aimed to established a psoriatic cell model to investigate the effect of normal dermal mesenchymal stem cell (DMSCs) on keratinocyte proliferation, inflammation responses and the associated mechanism.

Methods: To create an in vitro model of psoriasis, HaCaT cells were stimulated with a mixture of five inflammatory cytokines including IL-17A, IL-22, oncostatin M, IL-1α, and TNF-α (M5). A transwell co-culture system was employed to assess the influence of normal DMSCs on proliferation and inflammation response of HaCaT cells. Cell viability was assessed using the CCK-8 assay and EDU incorporation assay. The expression levels of mRNA for inflammatory cytokines (IL-8, IL-17A and TNF-α) in HaCaT cells co-cultured with either normal or psoriatic DMSCs were quantified by qRT-PCR. Apoptosis was evaluated by annexin V-FITC/PI double staining and TUNEL/DAPI staining assay. Autophagy was detected by immunostaining, RT-PCR and western blotting. Additionally, the expression levels of mRNA and protein of both Akt and mammalin target of rapamycin(mTOR) were also determined.

Results: Normal DMSCs were found to decrease the viability and promote apoptosis of HaCaT cells treated with M5. Furthermore, DMSCs reduced the secretion of proinflammatory cytokines, such as IL-8, IL-17A and TNF-α. Importantly, normal DMSCs were shown to induced autophagy in HaCaT cell. Pretreatment of HaCaT cells with autophagy inhibitor 3-methyladenine (3-MA) reversed the anti-psoriatic effect of normal DMSCs. Notably, DMSCs promote autophagy in M5-treated HaCaT cells by inhibition of p-Akt/Akt and p-mTOR/mTOR ratio.

Conclusion: Normal mesenchymal stem cells promote autophagy through the inhibition of Akt/mTOR signaling pathway, leading to the alleviation of psoriasis in vitro. These findings provide insights into the potential mechanisms by which DMSCs may exert therapeutic effects in psoriasis and support further investigation into their clinical applications.