Oral whole-leaf matcha partially attenuates UV-induced dermoepidermal disruption and collagen phenotype alterations in a rat model of repeated photoaging

Background Repeated ultraviolet (UV) exposure promotes oxidative stress, extracellular matrix remodeling, and disruption of dermoepidermal architecture, all of which contribute to skin photoaging. Although green tea derivatives have been investigated for photoprotective effects, the impact of oral whole-leaf matcha powder on cumulative UV-induced skin changes remains insufficiently characterized. The aim of this study was to investigate whether oral whole-leaf matcha powder was associated with attenuation of UV-induced dermoepidermal disruption, collagen phenotype alterations, and skin surface changes in a rat model of repeated UV exposure. Methods Thirty-two female Sprague–Dawley rats were randomly assigned to Control, UV, Matcha, and UV + Matcha groups ( n = 8/group). Matcha was administered orally at 50 mg/kg/day for 30 days. Experimental photoaging was induced using a repeated UV exposure protocol comprising 15 sessions over 4 weeks. Histomorphometric evaluation of dermoepidermal architecture, collagen phenotype, and elastic fiber parameters was performed together with serum antioxidant enzyme measurements and macroscopic skin surface analyses. Results Compared with controls, repeated UV exposure increased epidermal thickness ( p = 0.001), reduced the interdigitation index ( p = 0.002), decreased type I collagen and the type I/III collagen ratio ( p < 0.001 and p = 0.001, respectively), increased type III collagen ( p = 0.016), and reduced glutathione reductase activity ( p < 0.001). UV exposure was also associated with higher surface texture indices, including FFT roughness and local variance (both p < 0.001), as well as an increased fine wrinkle percentage ( p < 0.001). Compared with the UV group, the UV + Matcha group showed attenuated epidermal thickening ( p = 0.029), higher dermal papilla thickness ( p = 0.036) and epidermal rete ridge thickness ( p < 0.001), higher superoxide dismutase activity ( p = 0.031), a lower local variance index ( p = 0.037), and reduced fine wrinkle percentage ( p = 0.001). Conclusion Oral whole-leaf matcha powder was associated with partial attenuation of UV-induced phenotypic changes, including dermoepidermal structural alterations, collagen phenotype shifts, and surface deterioration, in this rat model of repeated photoaging. These findings suggest a potential adjunctive photoprotective effect, although further molecular-level validation and clinical studies are required to clarify the underlying pathways and translational relevance.