Background:

Mesenchymal stem cells (MSCs) have been widely used for inflammatory diseases like acute liver injury (ALI) and COVID-19 diseases. However, most MSCs instead of the cell-matrix are cultured in 2 D plates, resulting in degeneration of some key functions along with a limited understanding of the immune response in tissue repairing. Herein, we obtained the human umbilical cord MSCs grown on microcarriers in 3 D suspension culture (3 D hUCMSCs) that proved more appreciative than 2 D hUCMSCs for the ALI therapy. Methods hUCMSCs were isolated and respectively cultured in 2 D plates and 3 D microcarriers in vitro , and acute liver injury model in mice was used to evaluate tissue repairing ability of the transplanted hUCMSCs. Nitric oxide production, cell proliferation and the relative protein expression level were comprehensively evaluated. Besides, the cytokine expression level in the of serum mice was detected by quantitative RT-PCR and cytokine antibody chip. Results When transplanted with 3 D hUCMSCs in ALI mice, the injured liver tissues have a significantly-increased histological scores and enhanced animal’s body/liver weight, superior to the 2 D hUCMSCs and control group. Pro-inflammatory cytokines (IL-6, IL-1β, IL-17, IL-22 and TNF-α), apoptosis promoter IFN-g, and NO production declined when transplanted with 3D hUCMSCs compared to the control group. Besides, anti-inflammatory cytokines (IL-10) was up-regulated. Conclusion Both the 3 D hUCMSCs and the conditioned medium were more favorable for the therapy of acute liver injury (ALI). Triple regulatory roles of the 3 D hUCMSCs include the effective promotion of M1/M2 macrophage switch through increased secreting of anti-inflammatory cytokines, ameliorating proliferation and NO downregulation of macrophage. A balance of these cytokines in the conditioned medium of 3 D hUCMSCs played a key role in ALI repairing. It was proven that the 3 D hUCMSCs could trigger the mitogen-activated protein kinases (MAPKs) and STAT3 signaling pathways. Conclusively, the revelation of the superior moderating effect of 3 D hUCMSCs and possible regulatory mechanisms will improve the clinical efficacy of stem cell therapy for inflammatory and immunological diseases.