RESUMEN
BACKGROUND: A definitive conclusion on the efficacy of mesenchymal stromal cells-derived conditioned medium (MSCs-CM) in pulmonary fibrosis has not yet been reached. Therefore, the present meta-analysis intends to investigate the efficacy of MSCs-CM administration on improvement of pulmonary fibrosis. METHODS: An extensive search was performed on the Medline, Embase, Scopus and Web of Science databases by the end of August 2019. Outcomes in the present study included pulmonary fibrosis score, lung collagen deposition, lung collagen expression, transforming growth factor ß1 (TGF-ß1) expression and interleukin-6 expression. Finally, the data were pooled and an overall standardized mean difference (SMD) with a 95% confidence interval (CI) was reported. RESULTS: Data from seven studies were included. Analyses showed that administration of MSCs-CM significantly improved pulmonary fibrosis (SMD = -2.36; 95% CI: -3.21, -1.51). MSCs-CM administration also attenuated lung collagen deposition (SMD = -1.70; 95% CI: -2.18, -1.23) and decreased expression of type I collagen (SMD = -6.27; 95% CI: -11.00, -1.55), type III collagen (SMD = -5.16; 95% CI: -9.86, -0.47), TGF- ß1 (SMD = -3.36; 95% CI: - 5.62, -1.09) and interleukin-6 (SMD = -1.69; 95% CI: - 3.14, -0.24). CONCLUSION: The present meta-analysis showed that administration of MSCs-CM improves pulmonary fibrosis. It seems that the effect of MSCs-CM was mediated by reducing collagen deposition as well as inhibiting the production of inflammatory chemokines such as TGF-ß1 and interleukin 6 (IL-6). Since there is no evidence on the efficacy of MSCs-CM in large animals, further studies are needed to translate the finding to clinical studies.