HVEGF165 increases survival of transplanted hepatocytes within portal radicles: suggested mechanism for early cell engraftment

The history and use of human hepatocytes for the treatment of liver diseases: the first 100 patients

Orthotopic liver transplantation remains the only curative treatment for many end-stage liver diseases, yet the number of patients receiving liver transplants remains limited by the number of organs available for transplant. There is a need for alternative therapies for liver diseases. The transplantation of isolated hepatocytes (liver cells) has been used as an experimental therapy for liver disease in a limited number of cases. Recently, the 100th case of hepatocyte transplantation was reported. This review discusses the history of the hepatocyte transplant field, the major discoveries that supported and enabled the first hepatocyte transplants, and reviews the cases and outcomes of the first 100 clinical transplants. Some of the problems that limit the application or efficacy of hepatocyte transplantation are discussed, as are possible solutions to these problems. In conclusion, hepatocyte transplants have proven effective particularly in cases of metabolic liver disease where reversal or amelioration of the characteristic symptoms of the disease is easily quantified. However, no patients have been completely corrected of a metabolic liver disease for a significant amount of time by hepatocyte transplantation alone. It is likely that future developments in new sources of cells for transplantation will be required before this cellular therapy can be fully implemented and available for large numbers of patients.

Cellularized biosynthetic microhydrogel polymers for intravascular liver tissue regeneration therapy

INTRODUCTION

The liver is the natural microenvironment for hepatocytes transplantation but unfortunately engraftment efficiency is low. Cell-laden microhydrogels made of fibrinogen attached to poly(ethylene glycol) (PEG)-diacrylate side chains, were used as a cell carrier, for intravascular transplantation. This approach may reduce shear stress and immediate immunological pressure after intravascular transplantation and provide biomatrix for environmental support.

AIMS

In vitro assessment of HuH-7 viability and function after polymerization within PEGylated fibrinogen-hydrogel. In vivo assessment of intraportal transplantation of cell-laden microhydrogels with rat adult parenchymal cells.

METHODS

(1) In vitro assessment of HuH-7 cell viability and function, after cell-laden hydrogel (hydrogel volume 30 μL) fabrication, by propidium iodide (PI)/fluorescein diacetate (FDA), and MTT assays, albumin concentration and CYP1A activity. (2) Fabrication of cell-laden microhydrogels and their intraportal transplantion. Engraftment efficiency in vivo was evaluated by real-time qPCR of Y chromosome (SRY gene) and histology.

RESULTS

The viability of cells in hydrogels in culture was comparable to viability of not embedded cells during the first 48 h. However, the viability of cells in hydrogels was reduced after 72 h compared with not embedded cells. Activity of CYP1A in hydrogel was comparable to that of not embedded cells (4.33±1 pmole/μg DNA/4 h vs. 5.13±1 pmole/μg DNA/4 h, respectively). Albumin concentration increased at day 3 in hydrogels to 1.4±0.6 μg/10(4)/24 h and was greater to that of free cells, 0.3±0.1 μg/10(4)/24 h. Cell-laden microhydrogels at a size of 150-150-600 μm (6×10(6) cells/rat) showed better engraftment efficiency at 21 days post-transplantation, compared with isolated cell transplantation (54.6%±5% vs. 1.8%±1.2%, p<0.001).

CONCLUSIONS

The in vitro HuH-7 viability and function after polymerization in PEGylated fibrinogen hydrogel was comparable to cells without the hydrogel. Long-term survival and engraftment efficiency of intravascular transplanted adult hepatocytes is much better in within cell-laden microhydrogels compared with isolated cells. The overall efficiency of the procedure needs to be improved.

Liver cell transplantation for Crigler-Najjar syndrome type I: Update and perspectives

Liver cell transplantation is an attractive technique to treat liver-based inborn errors of metabolism. The feasibility and efficacy of the procedure has been demonstrated, leading to medium term partial metabolic control of various diseases. Crigler-Najjar is the paradigm of such diseases in that the host liver is lacking one function with an otherwise normal parenchyma. The patient is at permanent risk for irreversible brain damage. The goal of liver cell transplantation is to reduce serum bilirubin levels within safe limits and to alleviate phototherapy requirements to improve quality of life. Preliminary data on Gunn rats, the rodent model of the disease, were encouraging and have led to successful clinical trials. Herein we report on two additional patients and describe the current limits of the technique in terms of durability of the response as compared to alternative therapeutic procedures. We discuss the future developments of the technique and new emerging perspectives.

Stem cells for liver tissue repair: Current knowledge and perspectives

Stem cells from extra- or intrahepatic sources have been recently characterized and their usefulness for the generation of hepatocyte-like lineages has been demonstrated. Therefore, they are being increasingly considered for future applications in liver cell therapy. In that field, liver cell transplantation is currently regarded as a possible alternative to whole organ transplantation, while stem cells possess theoretical advantages on hepatocytes as they display higher in vitro culture performances and could be used in autologous transplant procedures. However, the current research on the hepatic fate of stem cells is still facing difficulties to demonstrate the acquisition of a full mature hepatocyte phenotype, both in vitro and in vivo. Furthermore, the lack of obvious demonstration of in vivo hepatocyte-like cell functionality remains associated to low repopulation rates obtained after current transplantation procedures. The present review focuses on the current knowledge of the stem cell potential for liver therapy. We discuss the characteristics of the principal cell candidates and the methods to demonstrate their hepatic potential in vitro and in vivo. We finally address the question of the future clinical applications of stem cells for liver tissue repair and the technical aspects that remain to be investigated.

VEGF signaling inhibitors: more pro-apoptotic than anti-angiogenic

The vascular endothelial growth factor (VEGF) family of polypeptide growth factors regulates a family of VEGF receptor (VEGFR) tyrosine kinases with pleiotropic downstream effects. Angiogenesis is the best known of these effects, but additional VEGF-dependent actions include increased vascular permeability, paracrine/autocrine growth factor release, enhancement of cell motility, and inhibition of apoptosis. In theory, therapeutic inhibition of angiogenesis should reduce tumor perfusion and thus increase tumor hypoxia and chemoresistance, but in clinical practice the VEGF antibody bevacizumab acts as a broad-spectrum chemosensitizer. Since VEGFR expression occurs in many tumor types, such chemosensitization is more readily explained by direct inhibition of tumor cell survival signals than by indirect stromal/vascular effects. The emerging model of anti-VEGF drug action being mediated primarily by tumoral (as distinct from endothelial) VEGFRs has clinically important implications for optimizing the anti-metastatic efficacy of this expanding drug class.

The effects of immunosuppressive agents on the function of human hepatocytes in vitro

Calcineurin inhibitors (tacrolimus) and steroids continue to be an important component of hepatocyte transplantation protocols, despite reports of hepatotoxicity and inhibitory effects of steroids on cell proliferation. The aim of the study was to investigate whether isolated human hepatocytes were more vulnerable to the toxicity of these agents and also to investigate their effects on hepatocyte VEGF secretion, a vascular permeability factor suggested to be involved in the cell engraftment process. Human hepatocytes were isolated from donor livers/segments rejected or unused for orthotopic liver transplantation using a collagenase perfusion technique. Hepatocytes were plated for cell function tests and to determine VEGF production. Tacrolimus (0-50 ng/ml) and methylprednisolone (0-500 ng/ml) were added to the culture media and cells incubated for 24 h. Cell metabolic activity was assessed using the MTT assay, cell number using the SRB assay, and cell attachment from hepatocyte total protein content and protein synthesis using [14C]leucine incorporation. VEGF in culture supernatants was measured by ELISA. Tacrolimus and methylprednisolone had no statistically significant inhibitory effects on metabolic activity or protein synthesis compared to controls at all concentrations of the agents tested when added after plating. There were also no significant effects on cell attachment when tacrolimus or methylprednisolone was added at the time of cell plating. There were no differences in the responses obtained when either fresh or cryopreserved hepatocytes were used. The amount of VEGF secreted by untreated hepatocytes was highly variable (0-1400 pg/10(6) cells/24 h). VEGF levels in the culture supernatant from hepatocytes isolated from < or = 20-year-old donors (687 +/- 59 pg/10(6) cells/24 h) was significantly greater than from older donors (61 +/- 7 pg/10(6) cells/24 h; p = 0.003). Tacrolimus and methylprednisolone did not significantly affect VEGF secretion by hepatocytes. Tacrolimus and methylprednisolone did not have detrimental effects on the metabolic function of human hepatocytes, cell attachment, or VEGF secretion after cell isolation.

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.