Abstract

Objectives: Lymphatic vessels are essential for skin health but their function deteriorates with aging and stress. We screened a library of 2200 natural plant extracts for the ability to promote lymphatic activity, using a 3D phenotype-based assay with human lymphatic endothelial cells. We identified 5 hits that were further characterized for their efficacy and underlying mechanisms involved in promoting lymphatic function in vitro. The feasibility to deliver tangible results using a combination of the lymphatic activators was confirmed in vivo, revealing efficacy against periorbital edema/puffy eyes. Introduction: The lymphatic system governs fluid homeostasis, immune surveillance and the elimination of the skin’s metabolites and inflammatory mediators, thus playing a critical role in skin health and appearance. UV-exposure, stress and aging result in reduced function and rarefication of the lymphatic network with compromised drainage efficiency, thereby leading to impaired skin function and repair, wrinkles, sagging skin and puffiness. Given the importance of an efficient lymphatic system for healthy skin, we dedicated our work to the discovery of natural lymphatic activators. Materials / method: Cryopreserved human lymphatic endothelial cells (LECs) were used, isolated as previously described (Hirakawa et al., 2003). The screening of the extracts was performed using our 3-D lymphangiogenic sprouting assay, measuring lymphatic sprouts as surrogate parameter for lymphangiogenesis. Stack-images and quantification were performed automatically. The positive hits were further validated using elaborate in vivo and ex vivo culture systems including RNAseq analysis. Additionally, clinical studies were performed to assess the effectiveness of formulations containing the extracts in vivo. Results: With the lymphangiogenic sprouting assay we screened 2200 plant extracts and identified 5 hits, which in combination activated LECs by more than 270%. Culture of ageing LECs in the presence of this combination was found to induce the major lymphatic survival, maintenance and activity genes. Treatment of human skin explants visibly improved lymphatic morphology. A clinical study with the extract combination in a cosmetic formulation, conducted by an external provider, confirmed an improved lymphatic function through the significant reduction of periorbital edema. Conclusion: Here we report the discovery of the first natural lymphatic activators, using a phenotype-based screening assay and a plant extract library. The identified hits synergistically induced lymphatic activation by more than 270% in vitro, coupled with an improved vascular phenotype and an induction of critical molecular pathways. The implementation of lymphatic activators in a clinical study using a cosmetic formulation led to significantly decreased periorbital puffiness and improve skin quality. Thus, lymphatic activators present a new dimension in functional skincare.