Bioluminescence Imaging of Transplanted Mesenchymal Stem Cells by Overexpression of Hepatocyte Nuclear Factor4α: Tracking Biodistribution and Survival.

PURPOSE: The purposes of this study were to construct immortalized human bone marrow mesenchymal stem cells (UE7T-13) with overexpression of the hepatocyte nuclear factor4α (hHNF4α) and luciferase2-mKate2 dual-fusion reporter gene, further investigate their impact on treating acute liver injury (ALI) in rats, and track their biodistribution and survival by bioluminescence imaging (BLI).

PROCEDURES: The hHNF4α and luciferase2-mKate2 genes were transduced by a lentiviral vector into UE7T-13 cells (named E7-hHNF4α-R cells), and expression was verified by immunofluorescence, RT-PCR, and flow cytometry. E7-hGFP-R cells expressing the luciferase2-mKate2/hGFP gene served as a negative group. A correlation between the bioluminescence signal and cell number was detected by BLI. The ALI rats were established and divided into three groups: PBS, E7-hGFP-R, and E7-hHNF4α-R. After transplantation of 2.0 × 106 cells, BLI was used to dynamically track their biodistribution and survival. The restoration of biological functions was assessed by serum biochemical and histological analyses.

RESULTS: Stable high-level expression of hHNF4α and mKate2 protein was established in the E7-hHNF4α-R cells in vitro. The E7-hHNF4α-R cells strongly expressed hGFP, hHNF4α, and mKate2 proteins, and the hHNF4α gene. hGFP-mKate2 dual-positive cell expression reached approximately 93 %. BLI verified that a linear relationship existed between the cell number and bioluminescence signal (R2  = 0.9991). The cells improved liver function in vivo after transplantation into the ALI rat liver, as evidenced by the fact that AST and ALT temporarily returned to normal levels in the recipient ALI rats. The presence of the transplanted E7-hGFP-R and E7-hHNF4α-R cells in recipient rat livers was confirmed by BLI and immunohistochemistry. However, the cells were cleared by the immune system a short time after transplantation into ALI rats with a normal immune system.

CONCLUSION: Our data revealed that the E7-hHNF4α-R cells can transiently improve damaged liver function and were rapidly cleared by the immune system. In addition, BLI is a useful tool to track transplanted cell biodistribution and survival.