Dose-response immunomodulatory effects of Mesenchymal stem cell-derived culture-conditioned media in acute Graft-versus-Host Disease

Background

Mesenchymal stem cell-based therapy faces challenges that have driven interest in MSCs-derived culture-conditioned media (CCM) as a cell-free alternative. Our study aims to optimize the dose and collection timing of CCM to enhance its therapeutic efficacy in aGVHD, while also standardizing co-culture conditions for CD3⁺ T-cell interaction with CCM.

Material and methods

Human MSCs were isolated from BM and WJ and subsequently preconditioned under hypoxic conditions (1 % O₂) for 24 h in a tri-gas incubator. Culture-conditioned media (CCM) were collected from both naive (MSCs) and hypoxia-preconditioned MSCs (MSCs^HYP) at 24, 48, and 72 h and filtered using a 0.2 μm membrane filter. CD3⁺ T-cell were isolated from PBMNCs derived from aGVHD patients. These T-cell were co-cultured at varying densities (2∗10⁶, 5∗10⁶, and 10∗10⁶ cells/ml) with different concentrations of CCM (25 %, 50 %, and 100 %), and cell proliferation was assessed using the MTS assay. Furthermore, CD3⁺ T-cell proliferation and activation status were evaluated in a 2D co-culture model of CD3⁺ T-cell and CCM using flow cytometry.

Results

Our findings revealed that CCM collected at 48 h, at a 50 % concentration, exerted the most pronounced inhibitory effect on CD3⁺ T-cell proliferation, particularly at a density of 5∗10⁶ cells/ml, irrespective of the MSCs source. Hypoxia preconditioning significantly enhanced the immunomodulatory effects, with WJ-MSCs^HYP-CCM demonstrating superior efficacy in suppressing T-cell proliferation, increasing the CD4⁺/CD8⁺ T-cell ratio, and reducing CD4⁺ T-cell activation compared to BM-MSCs^HYP-CCM.

Conclusion

These results emphasize the critical role of optimizing CCM collection timing and concentration to maximize therapeutic potential. Our study paves the way for the development of standardized, scalable, and effective cell-free therapies for aGVHD.