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

Authors

Sayed Amin Mirdamadian, Seyyed Meysam M Abtahi Froushani

Published in

Cell journal. Volume 28. Issue 1. Pages 1-9. Jun 29, 2026. Epub Jun 29, 2026.

Abstract

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.
In this experimental study, MSCs were isolated from mouse bone marrow and characterized by CD73 expression and lack of CD45/CD80. MSCs were treated with Muramyl dipeptide (MDP; 0 and 10 μg/mL) for 24 hours, followed by washing and further culture for 48 hours to obtain conditioned medium (CM). The resulting CM from untreated MSCs and MDP-primed MSCs (MDP-CM) was collected for subsequent in vivo 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).
MDP did not affect MSC viability but significantly altered the CM's immunological profile: MDP-CM had lower levels of IFN-γ, IL-6, and IL-1β, and higher levels of indoleamine 2,3-dioxygenase, TGF-β, and IL-10 compared to control CM. in vivo administration of MDP-CM significantly attenuated RA severity and promoted body weight recovery more effectively than CM alone. In addition, MDP-CM significantly reduced systemic inflammatory markers , such as TNF-α, IL-1β, myeloperoxidase, nitric oxide, and C-reactive protein (CRP), and more strongly modulated T-cell- associated gene expression in joint tissue, evidenced by upregulation of FOXP3 and downregulation of T-bet, Gata3, and Rorc compared with RA rats receiving CM.
The CM derived from appropriately primed MSCs may represent a more potent and standardized "off-theshelf" alternative to direct stem cell transplantation.

PMID:
42366930
Bibliographic data and abstract were imported from PubMed on 29 Jun 2026.

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