Cirrhosis is the terminal stage of hepatic diseases and is prone to develop into hepatocyte carcinoma. Increasing evidence suggests that the transplantation of dental pulp stem cells (DPSCs) may promote recovery from cirrhosis, but the key regulatory mechanisms involved remain to be determined. In this study, we overexpressed human hepatocyte growth factor (hHGF) in primary rat DPSCs and evaluated the effects of HGF overexpression on the biological behaviors and therapeutic efficacy of grafted DPSCs in cirrhosis. Liver cirrhosis was induced via the intraperitoneal injection of CCl4 twice weekly for 12 weeks and was verified through histopathological and serological assays. HGF was overexpressed in DPSCs via transduction with a hHGF-lentiviral vector and confirmed based on the elevated expression and secretion of HGF. The HGF-overexpressing DPSCs were transplanted into rats intravenously. The HGF-overexpressing DPSCs showed increased survival and hepatogenic differentiation in host liver tissue at 6 weeks after grafting. They also exhibited a significantly greater repair potential in relation to cirrhosis pathology and impaired liver function than did DPSCs expressing HGF at physiological levels. Our study may provide an experimental basis for the development of novel methods for the treatment of liver cirrhosis in clinical practice.
Cirrhosis, characterized by diffuse degeneration and the death of hepatocytes, followed by nodular regeneration, extensive fibrosis and the consequent collapse of the normal liver architecture, is the terminal stage of a variety of chronic liver diseases, resulting in irreversible impaired liver function, portal hypertension and the potential to develop into hepatocellular carcinoma1,2. Epidemiological data show that liver cirrhosis is the 14th most common cause of death worldwide but the fourth in central Europe3. Because of the lack of effective anti-fibrotic methods currently available in clinical practice3,4,5, liver transplantation remains the only chance of a cure for patients with liver cirrhosis and is severely restricted by the source of donor organs. Hence, alternative therapeutic strategies are needed.
Mesenchymal stem cell (MSC) transplantation, which has shown notable potential for repairing hepatic architecture and function in preclinical studies, may represent a prospective therapy for liver fibrosis6. Dental pulp stem cells (DPSCs) are a unique type of dental pulp-enriched MSC that hold promise for use in tissue engineering and regenerative therapies. DPSCs are widely available, proliferate rapidly and thus easily amplified, have preserved multipotency, are able to survive during long-term cryopreservation and have minimal immune rejection when autografted7,8,9,10. Grafted DPSCs show an effective regenerative capacity in cardiac injury following ischemia-reperfusion as well as central nervous system injury, without teratoma formation11,12. Recently, DPSCs have been reported to differentiate into functional hepatocyte-like cells and express hepatic markers in vitro and in vivo13,14. However, the determinant induction of hepatic differentiation of DPSCs and the therapeutic efficacy of DPSC grafting for cirrhosis remain poorly understood.
Hepatocyte growth factor (HGF), which is mainly secreted by mesenchymal cells, functions as a cell growth, motility, morphogenic and antiapoptotic factor by activating c-Met receptor/tyrosine kinase signaling in many cell types and plays critical roles in embryonic organogenesis, adult organ regeneration and wound healing15,16. HGF has also been verified to show anti-fibrotic activity in both the onset and progression of liver fibrosis/cirrhosis17,18. However, high exogenous HGF protein levels cannot be maintained, as the protein is extremely unstable (half-life <15 min)19. Therefore, the selection of a vehicle for the long-term transfer of therapeutic genes is important. For liver regeneration, MSCs are promising candidate. For example, transplantation of bone marrow mesenchymal stem cells (BMMSCs) and umbilical cord blood-derived mesenchymal stem cells (UCB-MSCs) overexpressing HGF in a rat model of liver fibrosis was shown to ameliorate liver injury induced by the hepatotoxin carbon tetrachloride (CCl4)20,21. However, the impact of HGF on DPSCs and the therapeutic efficacy of DPSCs in cirrhosis are still elusive.
Therefore, in the present study, we overexpressed human HGF (hHGF) in rat-derived primary DPSCs through the transduction of a hHGF-expressing lentiviral vector and evaluated the effects of elevated HGF expression on the survival, fate determination and regenerative capacity of grafted DPSCs in a rat model of cirrhosis to provide an experimental basis for the development of a novel anti-cirrhosis therapy.