Characterization of Long-Term Survival of Syngeneic Hepatocytes in Rat Peritoneum

Primary Hepatocyte Isolation and Cultures: Technical Aspects, Challenges and Advancements

Hepatocytes are differentiated cells that account for 80% of the hepatic volume and perform all major functions of the liver. In vivo, after an acute insult, adult hepatocytes retain their ability to proliferate and participate in liver regeneration. However, in vitro, prolonged culture and proliferation of viable and functional primary hepatocytes have remained the major and the most challenging goal of hepatocyte-based cell therapies and liver tissue engineering. The first functional cultures of rat primary hepatocytes between two layers of collagen gel, also termed as the "sandwich cultures", were reported in 1989. Since this study, several technical developments including choice of hydrogels, type of microenvironment, growth factors and culture conditions, mono or co-cultures of hepatocytes along with other supporting cell types have evolved for both rat and human primary hepatocytes in recent years. All these improvements have led to a substantial improvement in the number, life-span and hepatic functions of these cells in vitro for several downstream applications. In the current review, we highlight the details, limitations and prospects of different technical strategies being used in primary hepatocyte cultures. We discuss the use of newer biomaterials as scaffolds for efficient culture of primary hepatocytes. We also describe the derivation of mature hepatocytes from other cellular sources such as induced pluripotent stem cells, bone marrow stem cells and 3D liver organoids. Finally, we also explain the use of perfusion-based bioreactor systems and bioengineering strategies to support the long-term function of hepatocytes in 3D conditions.

Liver tissue engineering and cell sources: issues and challenges

Liver diseases are of major concern as they now account for millions of deaths annually. As a result of the increased incidence of liver disease, many patients die on the transplant waiting list, before a donor organ becomes available. To meet the huge demand for donor liver, alternative approaches using liver tissue engineering principles are being actively pursued. Even though adult hepatocytes, the primary cells of the liver are most preferred for tissue engineering of liver, their limited availability, isolation from diseased organs, lack of in vitro propagation and deterioration of function acts as a major drawback to their use. Various approaches have been taken to prevent the functional deterioration of hepatocytes including the provision of an adequate extracellular matrix and co-culture with non-parenchymal cells of liver. Great progress has also been made to differentiate human stem cells to hepatocytes and to use them for liver tissue engineering applications. This review provides an overview of recent challenges, issues and cell sources with regard to liver tissue engineering.

Growth factors improve gene expression after lentiviral transduction in human adult and fetal hepatocytes

BACKGROUND

Lentiviral vectors may be vectors of choice for transducing liver cells; they mediate integration in quiescent cells and offer potential for long-term expression. In adult liver, hepatocytes are generally mitotically quiescent. There has been controversy as to the necessity for lentiviral vector target cells to be in the cell cycle; currently, there is consensus that effective transduction can be achieved in quiescent hepatocytes, by using virus at high titre. However, transduction approaches which reduce the multiplicities of infection (MOIs) required provide potential benefit of cost and safety for therapeutic use.

METHODS

We used two late-generation HIV-based lentiviral vector systems (pHR-SIN-cppT SGW and pRRLSIN.cPPT.PGK.WPRE) encoding LacZ/GFP reporter genes to transduce adult and fetal human hepatocytes in vitro + /- growth factors, hepatocyte growth factor (HGF) and epidermal growth factor (EGF). Green fluorescent protein (GFP) expression was observed microscopically, and quantified by fluorescence spectrometry for protein expression, fluorescence-activated cell sorting (FACS) analysis to identify the proportion of cells expressing GFP, and real-time quantitative polymerase chain reaction (PCR) for number of integrations.

RESULTS

Gene expression following lentiviral transduction of human liver cells in vitro was markedly enhanced by the growth factors HGF and EGF. In adult cells growth factors led to a greater proportion of cells expressing more GFP per cell, from more integration events. In human fetal cells, the proportion of transduced hepatocytes remained identical, but cells expressed more GFP protein.

CONCLUSIONS

This has implications for the design of regimes for liver cell gene therapy, allowing marked reduction of MOIs, and reducing both cost and risk of viral-mediated toxicity.

Hepatocyte transplantation: A review of laboratory techniques and clinical experiences

Orthotopic liver transplantation (OLT) is standard clinical practice for patients with severe and end-stage chronic liver disease. However, the chronic shortage of donor livers and parallel growth of the transplant waiting list mean that a substantial proportion of patients die while waiting for a donor liver. Attempts to reduce the waiting list by use of split-liver and living-related live donor techniques have had some impact, but additional approaches to management are vital if the death rate is to be significantly reduced. Extensive laboratory research work and limited clinical trials have shown that hepatocyte transplantation may be useful in bridging some patients to OLT. A major limiting factor has been the shortage of mature functioning human hepatocytes, which are currently mostly obtained from livers rejected for OLT. This review examines potential hepatocyte sources, hepatocyte isolation methods and preservation protocols that have been successfully established, along with an overview of clinical results.

Hepatocytes transplantation in rats with acute hepatic failure

AIM: To study the effect of allogeneic hepatocytes transplantation (HcT) intraperitoneally, intrasplenically or through vena portae in rats with acute hepatic failure (AHF) induced by D-galactosamine (D-gal).

METHODS: AHF rats were induced by D-gal. HcT was carried out 60h after intoxication, and all rats were divided into six groups: GroupⅠ received 2×10¹⁰/L hepatocytes 1 mL intraperitoneally with cyclosporin A (CsA) at 10 mg/kg simultaneously; Group Ⅱ received 1 mL normal saline (NS) intraperitoneally with CsA10 mg/kg; Group Ⅲ received 2×10¹⁰/L hepatocytes 1 mL through vena portae; Group Ⅳreceived 1mL NS through vena portae; Group Ⅴreceived 2×10¹⁰/L hepatocytes 1 mL intrasplenically; Group Ⅵ received 1 mL NS intrasplenically. After 1 wk the survival rates, liver function and liver histology of all rats were observed.

RESULTS: The survival rate of Group Ⅰ was higher than that of GroupⅡ (60 % vs 20%, P < 0.01), and their liver function and liver histology were obviously improved as compared with GroupⅡ. Similarly, the survival rate of Group Ⅴ was higher than that of Group Ⅵ (47% vs 20%, P < 0.05), and the liver function and liver histology were also improved in GroupⅤas compared with Group Ⅵ. On the other hand, the survival rate of Group Ⅲ was similar to that of GroupⅥ (20% vs 13.3%, P > 0.05), and their liver function and liver histology were also not improved significantly as compared with Group Ⅱ.

CONCLUSION: After HcT intraperitoneally or intrasplenically, the survival rates of AHF rats intoxicated with D-gal are increased, and the liver function and histology are also improved. On the contrary, the survival rate, liver function and liver histology of AHF rats through vena portae HcT are not improved.