The genus Prinsepia, a member of the Rosaceae family, consists of five distinct species predominantly found across the Himalayas, spanning regions such as China, Pakistan, India, Nepal, and Bhutan. Notably, P. utilis Royle thrives in uncultivated terrains and is commonly observed alongside streams and within shrubbery at elevations ranging from 1000 to 2560 m. In China, its primary habitats span provinces like Yunnan, Sichuan, Tibet and Guizhou. (Editorial Committee of Flora of China, 1986). The plant usually blooms in winter, while its fruits begin to ripen from April to June. Its tender tips and seed oil have long been used as vegetables and cooking oil respectively by ethnic groups such as Naxi, Mosuo, and Tibetan in Yunnan province. The seeds of P. utilis contain approximately 30% oil, whose composition interestingly shares similarities with Mediterranean olive oil, featuring fatty acids such as oleic, linoleic, palmitic, and linolenic (Maikhuri et al., 2021; Wang et al., 2013). This oil exhibits therapeutic benefits, including alleviating arthritis symptoms, reducing high blood pressure, and combating atherosclerosis (Gupta et al., 2015). In addition to these edible and medicinal functions, indigenous people have historically employed the oil for skincare and hair care practices to prevent skin dryness and wrinkling, maintain skin tenderness, and keep hair black and lustrous (Zhang, 2008). Currently, it has been developed as a cosmetic additive and is widely used in functional cosmetics within China.

As the market demand grows, substantial industrial biowastes are generated during the oil extraction process. Notably, hydroxynitrile glucosides with weak α-glucosidase inhibitory activity have been isolated from the oil cakes of P. utilis (Shi et al., 2021). The aqueous extract derived from the oil residue of P. utilis has exhibited noteworthy in vitro anti-mutagenic, anti-aging, and sun protective activities (Kewlani et al., 2022), while it is reported that the oil cakes’ paste has been used to treat conditions like ringworm or eczema (Manandhar, 1995). Further research has also highlighted the rich polysaccharide content in P. utilis seeds, showcasing potential health benefits such as reducing blood sugar levels, modulating lipid imbalances, and protecting the liver and kidneys in diabetic mice (Chen et al., 2007; Lv et al., 2014).

In our preliminary studies, the water extract of P. utilis oil cakes (WEPUOC) demonstrated a significant reduction in transepidermal water loss (TEWL) in animal models of acute epidermal permeability disruption (Fig. S1). However, the underlying mechanism by which WEPUOC repairs the epidermal barrier has yet to be elucidated.

The epidermal barrier, a sophisticated system composed of keratinocytes, the cornified envelope (CE), intercellular lipids, and intercellular connections like tight junctions (TJs) and desmosomes, plays a vital role in skin integrity (Stamatas et al., 2012). The CE relies on the interplay among transglutaminase-crosslinked proteins such as filaggrin (FLG), loricrin (LOR), and involucrin (INV) to function normally. Intercellular lipids, consisting of ceramides, cholesterol, and free fatty acids, are pivotal in maintaining epidermal barrier function (Landmann, 1988; Uchida and Celli, 2020). Tight junctions regulate the paracellular transport of water and solutes, influencing skin hydration and skin barrier function (Brandner, 2016; Schrader et al., 2012). Impaired barrier function is associated with inflammatory skin conditions like psoriasis and atopic dermatitis (AD) (Ghadially et al., 1996; Tsakok et al., 2019). In various disease diagnosis and treatment guidelines, it is emphasized that the restoration of the epidermal barrier is a vital aspect of managing skin disorders (Armstrong and Read, 2020; Wollenberg et al., 2019). To maximize the use of resources, this study aims to assess the efficacy of WEPUOC in repairing both acute and chronic damage to the epidermal permeability barrier caused by tape-stripping and acetone wiping. Furthermore, the study seeks to elucidate the potential mechanism underlying this reparative effect.