Polysaccharide from Prinsepia utilis Royle maintains the skin barrier by mediating differentiation, lipid metabolism and tight junction of keratinocyte.

Prinsepia utilis Royle (PUR) exhibits moisturizing, antioxidative, and antibacterial properties, supporting skin barrier integrity. Nevertheless, the molecular mechanisms underlying these effects remain unclear. This study investigates the role of polysaccharide from PUR (PUR-P) in keratinocyte differentiation, lipid metabolism, tight junction, and skin barrier repair, focusing on PPARα involvement. Cytotoxicity of PUR-P in keratinocytes was assessed using CCK-8, EdU staining, and flow cytometry. Marker expression associated with differentiation (K1 and K10), proliferation (K16 and K17), sebum synthesis (CERS3, FAS and HMGCS2), and tight junction (ZO-1, Occludin and Claudin-1) were measured via western blot and qRT-PCR. The FulKutis skin model was used to assess the effects of PUR-P and PPARα on the skin barrier. PUR-P induced cytotoxicity in keratinocytes above 10 mg/mL (48 h) and 5 mg/mL (72 h). At 10 mg/mL, PUR-P upregulated K1, K10, CERS3, FAS, ZO-1, Occludin, Claudin-1, PPARα, and PPARβ/δ at both mRNA and protein levels. These effects were mediated by PPARα, as inhibition by Norathyriol or PPARα shRNA lentiviruses reduced PUR-P's efficacy. In the FulKutis skin model, PUR-P mitigated sodium lauryl sulfate-induced stratum corneum damage, restoring transepithelial electrical resistance, reducing FITC-Dextran permeability, and improving protein expression levels, effects dependent on PPARα. PUR-P enhances skin barrier integrity by promoting keratinocyte differentiation, lipid metabolism, and tight junctions, which is associated with PPARα up-regulated K1, K10, K16, K17, CERS3, FAS, HMGCS2, ZO-1, Occludin, Claudin-1, FLG, INV, and LOR expression. These findings underscore the potential of PUR-P as a therapeutic agent for skin barrier-related disorders.