Influence of preservation solution on the isolation and culture of human hepatocytes from liver grafts

Hepatocyte transplantation program: Lessons learned and future strategies

This review aims to share the lessons we learned over time during the setting of the hepatocyte transplantation (HT) program at the Hepatic Cell Therapy Unit at Hospital La Fe in Valencia. New sources of liver tissue for hepatocyte isolation have been explored. The hepatocyte isolation and cryopreservation procedures have been optimized and quality criteria for assessment of functionality of hepatocyte preparations and suitability for HT have been established. The results indicate that: (1) Only highly viable and functional hepatocytes allow to recover those functions lacking in the native liver; (2) Organs with steatosis (≥ 40%) and from elderly donors are declined since low hepatocyte yields, viability and cell survival after cryopreservation, are obtained; (3) Neonatal hepatocytes are cryopreserved without significant loss of viability or function representing high-quality cells to improve human HT; (4) Cryopreservation has the advantage of providing hepatocytes constantly available and of allowing the quality evaluation and suitability for transplantation; and (5) Our results from 5 adults with acute liver failure and 4 from children with inborn metabolic diseases, indicate that HT could be a very useful and safe cell therapy, as long as viable and metabolically functional human hepatocytes are used.

Microengineered liver tissues for drug testing

Drug-induced liver injury (DILI) is a leading cause of drug attrition. Significant and well-documented differences between animals and humans in liver pathways now necessitate the use of human-relevant in vitro liver models for testing new chemical entities during preclinical drug development. Consequently, several human liver models with various levels of in vivo-like complexity have been developed for assessment of drug metabolism, toxicity, and efficacy on liver diseases. Recent trends leverage engineering tools, such as those adapted from the semiconductor industry, to enable precise control over the microenvironment of liver cells and to allow for miniaturization into formats amenable for higher throughput drug screening. Integration of liver models into organs-on-a-chip devices, permitting crosstalk between tissue types, is actively being pursued to obtain a systems-level understanding of drug effects. Here, we review the major trends, challenges, and opportunities associated with development and implementation of engineered liver models created from primary cells, cell lines, and stem cell-derived hepatocyte-like cells. We also present key applications where such models are currently making an impact and highlight areas for improvement. In the future, engineered liver models will prove useful for selecting drugs that are efficacious, safer, and, in some cases, personalized for specific patient populations.

Metabolomics discloses donor liver biomarkers associated with early allograft dysfunction

BACKGROUND & AIMS

Early allograft dysfunction (EAD) dramatically influences graft and patient outcome after orthotopic liver transplantation and its incidence is strongly determined by donor liver quality. Nevertheless, objective biomarkers, which can assess graft quality and anticipate organ function, are still lacking. This study aims to investigate whether there is a preoperative donor liver metabolomic biosignature associated with EAD.

METHODS

A comprehensive metabolomic profiling of 124 donor liver biopsies collected before transplantation was performed by mass spectrometry coupled to liquid chromatography. Donor liver grafts were classified into two groups: showing EAD and immediate graft function (IGF). Multivariate data analysis was used to search for the relationship between the metabolomic profiles present in donor livers before transplantation and their function in recipients.

RESULTS

A set of liver graft dysfunction-associated biomarkers was identified. Key changes include significantly increased levels of bile acids, lysophospholipids, phospholipids, sphingomyelins and histidine metabolism products, all suggestive of disrupted lipid homeostasis and altered histidine pathway. Based on these biomarkers, a predictive EAD model was built and further evaluated by assessing 24 independent donor livers, yielding 91% sensitivity and 82% specificity. The model was also successfully challenged by evaluating donor livers showing primary non-function (n=4).

CONCLUSIONS

A metabolomic biosignature that accurately differentiates donor livers, which later showed EAD or IGF, has been deciphered. The remarkable metabolomic differences between donor livers before transplant can relate to their different quality. The proposed metabolomic approach may become a clinical tool for donor liver quality assessment and for anticipating graft function before transplant.

Clinical outcome of hepatocyte transplantation in four pediatric patients with inherited metabolic diseases

Hepatocyte transplantation (HT) has become an effective therapy for patients with metabolic inborn errors. We report the clinical outcome of four children with metabolic inborn errors that underwent HT, describing the cell infusion protocol and the metabolic outcome of transplanted patients. Cryopreserved hepatocytes were used as this allows scheduling of treatments. Functional competence (viability, cell attachment, major cytochrome P450 and UDP-glucuronosyltransferase 1A1 activities, and urea synthesis) and microbiological safety of cell batches were assessed prior to clinical use. Four pediatric patients with liver metabolic diseases [ornithine transcarbamylase (OTC) deficiency, Crigler-Najjar (CNI) syndrome, glycogen storage disease Ia (GSD-Ia), and tyrosinemia type I (TYR-I)] underwent HT. Indication for HT was based on severity of disease, deterioration of quality of life, and benefits for the patients, with the ultimate goal to improve their clinical status whenever liver transplantation (LT) was not indicated or to bridge LT. Cells were infused into the portal vein while monitoring portal flow. The protocol included antibiotic prophylaxis and immunosuppressant therapy. After HT, analytical data on the disease were obtained. The OTC-deficient patient showed a sustained decrease in plasma ammonia levels and increased urea production after HT. Further cell infusions could not be administered given a fatal nosocomial fungus sepsis 2 weeks after the last HT. The CNI and GSD-Ia patients improved their clinical status after HT. They displayed reduced serum bilirubin levels (by ca. 50%) and absence of hypoglycaemic episodes, respectively. In both cases, the HT contributed to stabilize their clinical status as LT was not indicated. In the infant with TYR-I, HT stabilized temporarily the biochemical parameters, resulting in the amelioration of his clinical status while diagnosis of the disease was unequivocally confirmed by full gene sequencing. In this patient, HT served as a bridge therapy to LT.

Human hepatocyte transplantation in patients with hepatic failure awaiting a graft

BACKGROUND

Hepatocyte transplantation (HT) has the potential to become a promising treatment to temporarily support liver function in patients with liver failure.

METHODS

Two patients, who had already received a liver transplant (LT) in the past, with an end-stage liver disease due to recurrent hepatitis C virus cirrhosis, suffering acute-on-chronic liver failure while on the waiting list for an LT, received HT as a bridge to whole-organ retransplantation. After HT and during intensive care unit admission, blood tests and ammonia levels were determined every 12 and 24 h, respectively, before and after each hepatocyte infusion.

RESULTS

The present study describes monitoring of analytical and clinical parameters and improvement of liver function following HT. In both patients, we managed to lower the blood ammonia levels and clinically improve the degree of hepatic encephalopathy, thus serving as a bridge to liver retransplantation in 1 patient.

CONCLUSIONS

We believe that this therapy may be an alternative treatment in patients with chronic liver disease who suffer episodes of acute decompensation as a bridge to conventional LT.

Evaluation of cytochrome P450 activities in human hepatocytes in vitro

Major hepatic cytochrome P450 activities (CYP1A2, CYP2A6, CYP2B6, CYP2C9, CYP2C19, CYP2D6, CYP2E1, and CYP3A4) can be simultaneously examined in human hepatocytes by incubation with a cocktail of multiple specific probes. Cocktail strategy in combination with mass spectrometry is shown to be a robust, fast, and sensitive procedure for P450 activity assessment. This procedure allows a drastic reduction of the number of cells required in the assay and sample analysis time and increases throughput and reproducibility. Major applications of the probe cocktail strategy are P450 phenotyping of hepatocytes and induction studies.

Bone marrow mesenchymal stem cells as a treatment for acute liver failure

Bone marrow mesenchymal stem cells (BM-MSCs) are a kind of multipotent stem cells that have the capacity to undergo self-renewal and multi-lineage differentiation. In an appropriate microenvironment, BM-MSCs can differentiate into bone, cartilage, fat, nerve, liver or other cells. Based on this characteristic, BM-MSCs might be used as new seed cells for orthotopic liver transplantation and bioartificial liver support system. This paper reviews the recent advances in research on the use of BM-MSCs as a treatment for acute liver failure.

Bone marrow stem cells and liver regeneration

Development of new approaches to treat patients with hepatic diseases that can eliminate the need for liver transplantation is imperative. Use of cell therapy as a means of repopulating the liver has several advantages over whole-organ transplantation because it would be less invasive, less immunogenic, and would allow the use, in some instances, of autologous-derived cells. Stem/progenitor cells that would be ideal for liver repopulation would need to have characteristics such as availability and ease of isolation, the ability to be expanded in vitro, ensuring adequate numbers of cells, susceptibility to modification by viral vector transduction/genetic recombination, to correct any underlying genetic defects, and the ability of restoring liver function following transplantation. Bone marrow-derived stem cells, such as hematopoietic, mesenchymal and endothelial progenitor cells possess some or most of these characteristics, making them ideal candidates for liver regenerative therapies. Here, we will summarize the ability of each of these stem cell populations to give rise to functional hepatic elements that could mediate repair in patients with liver damage/disease.

Hypothermic storage of isolated human hepatocytes: a comparison between University of Wisconsin solution and a hypothermosol platform

Until now little is known about the functional integrity of human hepatocytes after hypothermic storage. In order to address this limitation, we evaluated several commercially available hypothermic preservation media for their abilities to protect freshly isolated hepatocytes during prolonged cold storage. Human hepatocytes were isolated from non-transplantable/rejected donor livers and resuspended in ice-cold University of Wisconsin solution (UW), HypoThermosol-Base (HTS-Base), or HypoThermosol-FRS (HTS-FRS) with or without the addition of fetal bovine serum. Cells were stored at 4 degrees C for 24-72 h, and evaluated for hepatocyte viability (trypan blue exclusion, or labeling with fluorochromes), cell attachment, and function. The energy status of hepatocytes was evaluated by measurement of intracellular adenosine 5'-triphosphate. To determine whether the test cells expressed metabolic functions of freshly isolated cells, the activities of major phase I (cytochromes P450, FMO) and phase II (UGT, ST) drug-metabolizing enzymes were examined. Although hepatocytes are shown to be satisfactory after 24 h storage in all of the tested solutions, the cell viability, energy status, and xenobiotic metabolism following cold preservation in HTS-FRS was consistently and, in some cases, markedly higher when compared with other systems. The same metabolites for each of the tested substrates were detected in all groups of cells. Moreover, the use of HTS-FRS eliminates the need for serum in preservation solutions. HTS-FRS represents an improved solution compared to HTS-Base and UW for extending the shipping/storage time of human hepatocytes.

Functional assessment of the quality of human hepatocyte preparations for cell transplantation

Hepatocyte transplantation is an alternative therapy to orthotopic liver transplantation for the treatment of liver diseases. Good quality freshly isolated or cryopreserved human hepatocytes are needed for clinical transplantation. However, isolation, cryopreservation, and thawing processes can seriously impair hepatocyte viability and functionality. The aim of the present study was to develop a fast and sensitive procedure to estimate the quality of hepatocyte preparations prior to clinical cell infusion. To this end, cell viability, attachment efficiency, and metabolic competence (urea synthesis and drug-metabolizing P450 activities) were selected as objective criteria. Viability of hepatocyte suspension was estimated by trypan blue staining. DNA content of attached cells 50 min after hepatocyte platting to fibronectin/collagen-coated dishes was quantified to estimate adherence capacity. Urea production was determined after incubating hepatocyte suspensions with 2 mM C1NH4 for 30 min. The cytochrome P450 function was assayed by a 30-min incubation of hepatocyte suspension with a cocktail mixture containing selective substrates for seven individual P450 activities (CYP1A2, 2A6, 2C9, 2C19, 2D6, 2E1, and 3A4). The assay can be applied to both freshly isolated and cryopreserved hepatocyte suspensions, and the results are available within 1 h, which could help to make short-term decisions: 1) to assess the suitability for cell transplantation of a preparation of freshly isolated hepatocytes or a particular batch of thawed cells, or 2) to estimate the convenience of banking a particular cell preparation.

Liver cell culture techniques

Different sources of hepatic tissue, including whole or split livers from organ donors or from cadavers, waste liver from therapeutic hepatectomies or small-sized surgical biopsies, can be successfully used to prepare human hepatocytes cultures. The two-step collagenase perfusion remains the most effective way to isolate high yields of viable hepatocytes from human liver samples that express many typical hepatic functions, among them drug-metabolising (detoxification) enzymes, when placed in primary culture. Once isolated, human hepatocytes cultured in monolayer in chemically defined conditions (serum-free) survive for limited periods of time gradually losing their differentiated phenotype, in particular the drug-metabolising enzymes. Supplementation of chemically defined media with growth factors, hormones and other specific additives has been used with variable success to extend hepatocyte survival and functionality in culture. Other culture improvements include the use of extracellular components to coat plates or to entrap cells. Conditions for short-term monolayer cultures, allowing the maintenance of liver-specific functions for approximately 1 week, are now well established. Cultures on plastic dishes coated with extracellular matrix components (i.e. Matrigel(TM), collagen, fibronectin or mixture of collagen and fibronectin) do meet many of the requirements for short-term incubation experiments, without adding too much complexity to the system. Practical details on how to carry out these cultures and to assess their functionality (CYP activity and ureogenesis) are discussed in this chapter.

Cryopreservation of rat, dog and human hepatocytes: influence of preculture and cryoprotectants on recovery, cytochrome P450 activities and induction upon thawing

Several cryopreservation protocols for hepatocytes have been proposed over the past few years, but their effectiveness varies greatly as a function of the characteristics of the method used. One factor in the success of cryopreservation is the quality of cells before freezing. The results suggest that the cryopreservation of hepatocytes in a medium containing polyvinylpyrrolidone (PVP), in addition to DMSO, constitutes a convenient means of long-term storage of hepatocytes for preparing primary cultures to be used in drug metabolism studies. The combined use of the two cryoprotectants is particularly critical for low-viability cell suspensions. An interesting alternative to increase cell viability is the preculture of hepatocytes before cryopreservation. By the use of this procedure, high-quality cells, estimated in terms of post-thaw recovery, viability, adaptation of hepatocytes to culture, drug-metabolizing capability and cytochrome P450 induction, are obtained. Therefore, cryopreserved hepatocytes can provide a regular source of metabolically competent cells for in vitro investigations of the metabolic profile of new drugs and drug-drug interactions in pharmaco-toxicological research.