The immunoregulation effect of bone marrow mesenchymal stem cells on liver regeneration of rats with acute liver failure

Objective To study the immunoregulation effect of bone marrow mesenchymal stem cells (BMMSC) transplantation on liver regeneration of rats with acute liver failure (ALF). Methods The ALF model of rats was induced by D-galactosamine (D-GalN). Then the ALF rats were randomly divided into ALF model group and BMMSC transplantation group at 24 h after the injection of D-GalN. Rats in ALF model group were injected with 0.9% saline via tail vein, while those in BMMSC transplantation group were injected with 1 mL BMMSC cell suspension containing 1×106 cells. Blood and liver tissue specimens of ALF rats were collected at day 1, 2, 3, 7 and 14, respectively after transplantation. Another six healthy rats were enrolled as control group. The levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were detected by automatic biochemistry analyzer. Tumor necrosis factor (TNF)-α and interleukin (IL)-6 in serum were detected by enzyme-linked immunosorbent assay (ELISA). The changes of liver pathology were observed with hematoxylin-eosin (HE) staining. The expression of proliferating cell nuclear antigen (PCNA) protein was detected by immunohistochemistry method. The ratio of regulatory T lymphocyte (Treg) cells to CD4+ T cells in PBMC was assayed by flow cytometry. Continuous variables were compared using Student t test, while categorical variables were compared using χ2 test. Results The mean survival time of rats in BMMSC transplantation group was (38.71±5.73) h, which was significantly longer than that in ALF model group ([29.90±6.17] h, t=2.92, P<0.05). Compared with ALF model group, the peak ALT level in transplantation group decreased significantly (t=2.76, P<0.05), and the levels of AST on 1, 2, 3 d after transplantation in transplantation group were all significantly lower than model group (t=3.22, 3.22, and 3.79; all P<0.05). The levels of TNF-α in transplantation group were decreased more obviously than those in model group (t=3.81, 6.44, 4.13, and 5.38; all P<0.05). The changes of IL-6 were as similar as TNF-α (t=8.10, 3.80, 3.92, and 4.37; all P<0.05). Moreover, the improvement of liver pathology was also pronounced than that in model group. At the same time, the expressions of PCNA protein on 1, 2, 3, 7, 14 d after transplantation in transplantation group were all increased significantly compared to those in model group (t=3.13, 6.37, 12.60, 2.31 and 6.20; all P<0.05). The ratio of Treg cells to CD4+ T cells increased significantly in ALF model rats. But the increases were more pronounced in transplantation group on 1, 2, 3, 7 d after transplantation (t=3.30, 4.13, 3.34, and 3.89; all P<0.05). Conclusions BMMSC transplantation in ALF rats is effective in inhibiting inflammation, which is favorable to improve liver function and regeneration. The negative immunoregulation role of BMMSC may be mediated, at least in part, through the regulation of Treg cells. Key words: Bone marrow mesenchymal stem cells; Immunoregulation; Liver failure, acute; T-lymphocytes, regulatory; Proliferating cell nuclear antigen