Prospect of stem cells conditioned medium (secretome) in ligament and tendon healing: A systematic review

Background Tendon or ligament tears can decrease patients' quality of life. Many therapeutic interventions are available to treat such injuries. Mesenchymal stem cells (MSCs) have been shown to be effective in treating tendon or ligament tears; however, the use of stem cell‐conditioned medium (CM) requires further investigation. This review focused on the use of stem cell CM as treatment for tendon or ligament tears. Methods A systematic literature search was performed on PubMed (MEDLINE), OVID, EMBASE, the Cochrane Library, Scopus, Web of Science, and Science Direct with the terms conditioned media or conditioned medium or secretome or microvesicle or extracellular vesicle or exosome, and tendon or ligament as the search keywords. A total of 852 articles were reviewed. Five articles were identified as relevant for this systematic review. Results Meta‐analysis could not be performed because of the high heterogeneity of the reviewed studies; however, the results of this study support a positive effect of conditioned media in tendon and ligament treatment. Conclusion This review provides evidence of improvement in the tendon and ligament healing process with stem cell CM therapy in preclinical studies. The secretome or stem cells conditioned medium comprises of soluble proteins and secreted extracellular vesicles. The proteins include biologically active factors such as cytokines, chemokines, and growth factors. The vesicular factors include exosomes and microvesicles (Driscoll J, Patel T. The mesenchymal stem cell secretome as an acellular regenerative therapy for liver disease. J Gastroenterol. 2019;54(9):763‐773. doi: 10.1007/s00535‐019‐01599‐1).