In Vivo Tracking and Comparison of the Therapeutic Effects of MSCs and HSCs for Liver Injury

BACKGROUND: Mesenchymal stem cells (MSCs) and hematopoietic stem cells (HSCs) have been studied for damaged liver repair; however, the conclusions drawn regarding their homing capacity to the injured liver are conflicting. Besides, the relative utility and synergistic effects of these two cell types on the injured liver remain unclear. METHODOLOGY/PRINCIPAL FINDINGS: MSCs, HSCs and the combination of both cells were obtained from the bone marrow of male mice expressing enhanced green fluorescent protein(EGFP)and injected into the female mice with or without liver fibrosis. The distribution of the stem cells, survival rates, liver function, hepatocyte regeneration, growth factors and cytokines of the recipient mice were analyzed. We found that the liver content of the EGFP-donor cells was significantly higher in the MSCs group than in the HSCs or MSCs+HSCs group. The survival rate for the MSCs group was significantly higher than that of the HSCs or MSCs+HSCs group; all surpassed the control group. After MSC-transplantation, the injured livers were maximally restored, with less collagen than the controls. The fibrotic areas had decreased to a lesser extent in the mice transplanted with HSCs or MSCs+HSCs. Compared with mice in the HSCs group, the mice that received MSCs had better improved liver function. MSCs exhibited more remarkable paracrine effects and immunomodulatory properties on hepatic stellate cells and native hepatocytes in the treatment of the liver pathology. Synergistic actions of MSCs and HSCs were most likely not observed because the stem cells in liver were detected mostly as single cells, and single MSCs are insufficient to provide a beneficial niche for HSCs. CONCLUSIONS/SIGNIFICANCE: MSCs exhibited a greater homing capability for the injured liver and modulated fibrosis and inflammation more effectively than did HSCs. Synergistic effects of MSCs and HSCs were not observed in liver injury.