Conditioned Medium from Muramyl Dipeptide-Primed Mesenchymal Stem Cells Enhances Therapeutic Efficacy in Experimental Rheumatoid Arthritis.

Objective: Rheumatoid arthritis (RA) is a chronic autoimmune disease that causes joint inflammation, disability, and reduced quality of life. Current mesenchymal stem cell (MSC) therapies face limitations due to cell variability and lack of standardization, highlighting the need for effective, cell-free alternatives that replicate MSCs' immunomodulatory functions. This study aimed to enhance MSC secretion of regulatory factors to modulate inflammation in an RA model. Materials and Methods: administration. RA was induced in male Wistar rats (160-180 g) via intradermal injection of Freund's complete adjuvant. Treatments with CM derived from either untreated MSCs or MDP-pulsed MSCs (MDP-CM) were initiated on day 7 post-induction and repeated after 5 days via intraperitoneal injection (n=10 per group). Results: compared with RA rats receiving CM. Conclusion: The CM derived from appropriately primed MSCs may represent a more potent and standardized "off-theshelf" alternative to direct stem cell transplantation.