Hyssopus officinalis L. (Lamiaceae) Cell Culture Extract Modulates Epidermal Lipid-Related and Differentiation Markers.

The skin barrier is essential for maintaining epidermal homeostasis and preventing transepidermal water loss (TEWL). This study investigated the ability of a Hyssopus officinalis cell culture hydroethanolic extract to support epidermal barrier function by modulating ceramide-related enzymes and structural proteins. Hydroethanolic extracts from cell cultures grown under light and dark conditions were characterized by high-resolution mass spectrometry. Dark-grown cultures accumulated higher levels of rosmarinic acid, hydroxytyrosol glycosides, and polymethoxyflavones than light-grown cultures and intact plants. In keratinocytes, the extract from dark-grown cells (HoEx) at 0.002% w/v exhibited significant antioxidant activity (20% ROS reduction) and increased β-glucocerebrosidase (GBA) activity (25%) as well as the expression of β-glucocerebrosidase (44%), serine palmitoyltransferase (34%), involucrin (17%), and filaggrin (44%) compared with control. In human skin explants, 0.5% w/w HoEx increased ceramide content (36%) and total epidermal lipid levels (99%) relative to control. In a clinical study involving 10 volunteers with mechanically stressed skin, 0.5% w/w HoEx increased GBA activity by 30% and reduced TEWL by 15%, whereas placebo treatment led to a 55% decrease in GBA activity and a 25% increase in TEWL. Collectively, these findings indicate that HoEx modulates multiple epidermal pathways involved in lipid processing and differentiation under in vitro, ex vivo, and stressed in vivo conditions. While the study was not designed to establish mechanistic causality, the coordinated modulation of ceramide-related enzymes, structural proteins, and TEWL suggests that HoEx may support epidermal barrier function within the limits of the tested models. HoEx therefore represents a standardized source of bioactive compounds with potential relevance for dermocosmetic applications.