Total saponin extracts of Pseudostellaria heterophylla ameliorates meibomian gland dysfunction through SCD1/SPT1/ceramide axis.

Ethnopharmacological Relevance: Pseudostellaria heterophylla (Tài Zǐ Shēn, TZS) is a traditional Chinese medicine with spleen and qi benefits. Its immunomodulatory, anti-fatigue, anti-stress, and lipid metabolism regulation effects have been clinically confirmed, but its role in meibomian gland dysfunction (MGD) is still unclear.

Aim Of The Study: This study aims to investigate the effect and mechanism of action of TZS in treating MGD.

Material And Methods: Several therapeutic agents were used to predict MGD treatment using the "Disease-Syndrome-TCM" network mechanism. We then performed a network pharmacology analysis to identify possible targets and pathways for drug treatment of the disease. It was then validated by in vitro experiments. The animal models were taken and analyzed by slit lamp and stereo microscope. HE and ORO staining analysis were then performed. Next, the expressions of key protein indicators were tested by IF, and finally the metabolism of key substances such as lipids and ceramides were detected by SRS imaging.

Results: The "Disease-Syndrome-TCM" network mechanism was used to predict several therapeutic agents for MGD treatment including TZS et al. Network pharmacology analysis revealed that the targets of active components in the total saponins of TZS (PHS) were significantly enriched in the pathways of PPAR and AMPK. Subsequently, seven targets of PHS were identified, which were enriched in signaling pathways associated with lipid metabolism and inflammation. Furthermore, in vivo experiments showed that PHS alleviated meibomian glands (MG) obstruction and atrophy induced by A939, a SCD1 inhibitor. PHS treatment significantly increased PPAR-γ proteins in MGs, contributing to the normal differentiation of acini. Additionally, PHS treatment resulted in a reduction in the number of K10-positive cells, which partially prevented keratinization and abnormal differentiation of acinar cells. TUNEL assay results indicated that PHS mitigated apoptosis in MGs. Detailed exploration using Raman spectroscopy imaging showed that PHS could enhance the expression of SCD1 protein and the unsaturation degree of fatty acids, which in turn downregulated SPT1 protein and endogenous ceramides de novo biosynthesis.

Conclusion: This study elucidated the effects of PHS in alleviating MGD and highlighted the pharmacological mechanisms involved, specifically the upregulation of SCD1 and inhibition of de novo ceramides biosynthesis. These findings provided a research basis for advancing its clinical application in MGD treatment.