Cryopreservation of Hepatocytes

Messenger RNA Expression of Albumin, Transferrin, Transthyretin, Asialoglycoprotein Receptor, Cytochrome P450 Isoform, Uptake Transporter, and Efflux Transporter Genes as a Function of Culture Duration in Prolonged Cultured Cryopreserved Human Hepatocytes as Collagen-Matrigel Sandwich Cultures: Evidence for Redifferentiation upon Prolonged Culturing

Hepatic gene expression as a function of culture duration was evaluated in prolonged cultured human hepatocytes. Human hepatocytes from seven donors were maintained as near-confluent collagen-Matrigelsandwich cultures, with messenger RNA expression for genes responsible for key hepatic functions quantified by real-time polymerase chain reaction at culture durations of 0 (day of plating), 2, 7, 9, 16, 23, 26, 29, 36, and 43 days. Key hepatocyte genes were evaluated, including the differentiation markers albumin, transferrin, and transthyretin; the hepatocyte-specific asialoglycoprotein receptor 1 cytochrome P450 isoforms CYP1A2, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, CYP3A4, and CYP3A7; uptake transporter isoforms SLC10A1, SLC22A1, SLC22A7, SLCO1B1, SLCO1B3, and SLCO2B1; efflux transporter isoforms ATP binding cassette (ABC)B1, ABCB11, ABCC2, ABCC3, ABCC4, and ABCG2; and the nonspecific housekeeping gene hypoxanthine ribosyl transferase 1 (HPRT1). The well established dedifferentiation phenomenon was observed on day 2, with substantial (>80%) decreases in gene expression in day 2 cultures observed for all genes evaluated except HPRT1 and efflux transporters ABCB1, ABCC2, ABCC3 (<50% decrease in expression), ABCC4 (>400% increase in expression), and ABCG2 (no decrease in expression). All genes with a >80% decrease in expression were found to have increased levels of expression on day 7, with peak expression observed on either day 7 or day 9, followed by a gradual decrease in expression up to the longest duration evaluated of 43 days. Our results provide evidence that cultured human hepatocytes undergo redifferentiation upon prolonged culturing. SIGNIFICANCE STATEMENT: This study reports that although human hepatocytes underwent dedifferentiation upon 2 days of culture, prolonged culturing resulted in redifferentiation based on gene expression of differentiation markers, uptake and efflux transporters, and cytochrome P450 isoforms. The observed redifferentiation suggests that prolonged (>7 days) culturing of human hepatocyte cultures may represent an experimental approach to overcome the initial dedifferentiation process, resulting in "stabilized" hepatocytes that can be applied toward the evaluation of drug properties requiring an extended period of treatment and evaluation.

Prolonged cultured human hepatocytes as an in vitro experimental system for the evaluation of potency and duration of activity of RNA therapeutics: Demonstration of prolonged duration of gene silencing effects of a GalNAc-conjugated human hypoxanthine phosphoribosyl transferase (HPRT1) siRNA

We report here the evaluation of a novel in vitro experimental model, prolonged cultured human hepatocytes (PCHC), as an experimental system to evaluate the potency and duration of effects of oligonucleotide therapeutics. A novel observation was made on the redifferentiation of PCHC upon prolonged culturing based on mRNA profiling of characteristic hepatic differentiation marker genes albumin, transferrin, and transthyretin. Consistent with the known de-differentiation of cultured human hepatocytes, decreases in marker gene expression were observed upon culturing of the hepatocytes for 2 days. A novel observation of re-differentiation was observed on day 7 as demonstrated by an increase in expression of the marker genes to levels similar to that observed on the first day of culture. The expression of the differentiation marker genes was highest on day 7, followed by a gradual decrease but remained higher than that on day 2 for up to the longest culture duration evaluated of 41 days. The redifferentiation phenomenon suggests that PCHC may be useful for the evaluation of the duration of effects of oligonucleotide therapeutics on gene expression in human hepatocytes. A proof of concept study was thereby conducted with PCHC with a GalNAc-conjugated siRNA targeting human hypoxanthine phosphoribosyl transferase1 (HPRT1). HPRT1 mRNA expression in siRNA-treated cultures decreased to 21% of that in untreated hepatocytes on day 1, <10% from days 2 to 12, <20% from days 16 to 33, and eventually recovered to 64% by day 41. Our results suggest that PCHC represent a clinically-relevant cost- and time-efficient experimental tool to aid in the evaluation of GalNAc-siRNA silencing activity, providing information on both efficacy and duration of efficacy. PCHC may be applicable in the drug development setting as a species- and cell type-relevant experimental tool to aid the development of oligonucleotide therapeutics.

Emerging Models of Drug Metabolism, Transporters, and Toxicity

This commentary summarizes expert mini-reviews and original research articles that have been assembled in a special issue on novel models of drug metabolism and disposition. The special issue consists of research articles or reviews on novel static or micro-flow based models of the intestine, liver, eye, and kidney. This issue reviews static intestinal systems like mucosal scrapings and cryopreserved intestinal enterocytes, as well as novel bioengineered or chemically engineered intestinal models derived from primary human tissue, iPSCs, enteroids, and crypts. Experts have reviewed hepatic systems like cryopermeabilized Metmax hepatocytes and longer term, hepatocyte coculture system from HµREL, yielding in vivo-like primary and secondary drug metabolite profiles. Additional liver models, including micropattern hepatocyte coculture, 3D liver spheroids, and microflow systems, applicable to the study of drug disposition and toxicology have also been reviewed. In this commentary, we have outlined expert opinions and current efforts on hepatic- and nephrotoxicity models. Ocular disposition models including corneal permeability models have been included within this special issue. This commentary provides a summary of in vivo mini-reviews of the issue, which have discussed the applications and drawbacks of pig and humanized mice models of P450, UGT, and rat organic anionic transporting polypeptide 1a4. While not extensively reviewed, novel positron emissions tomography imaging-based approaches to study the distribution of xenobiotics have been highlighted. This commentary also outlines in vitro and in vivo models of drug metabolism derived from breakthrough genetic, chromosomal, and tissue engineering techniques. The commentary concludes by providing a futuristic view of the novel models discussed in this issue.

Hepatocyte-induced CD4+ T cell alloresponse is associated with major histocompatibility complex class II up-regulation on hepatocytes and suppressible by regulatory T cells

Hepatocyte transplantation is a promising therapeutic approach for various liver diseases. Despite the liver's tolerogenic potential, early immune-mediated loss of transplanted cells is observed, and longterm acceptance has not been achieved yet. Patients deemed tolerant after liver transplantation presented an increased frequency of regulatory T cells (Tregs), which therefore also might enable reduction of posttransplant cell loss and enhance longterm allograft acceptance. We hence characterized hepatocyte-induced immune reactions and evaluated the immunomodulatory potential of Tregs applying mixed lymphocyte cultures and mixed lymphocyte hepatocyte cultures. These were set up using peripheral blood mononuclear cells and primary human hepatocytes, respectively. Polyclonally expanded CD4⁺ CD25^high CD127^low Tregs were added to cocultures in single-/trans-well setups with/without supplementation of anti-interferon γ (IFNγ) antibodies. Hepatocyte-induced alloresponses were then analyzed by multicolor flow cytometry. Measurements indicated that T cell response upon stimulation was associated with IFNγ-induced major histocompatibility complex (MHC) class II up-regulation on hepatocytes and mediated by CD4⁺ T cells. An indirect route of antigen presentation could be ruled out by use of fragmented hepatocytes and culture supernatants of hepatocytes. Allospecific proliferation was accompanied by inflammatory cytokine secretion. CD8⁺ T cells showed early up-regulation of CD69 despite lack of cell proliferation in the course of coculture. Supplementation of Tregs effectively abrogated hepatocyte-induced alloresponses and was primarily cell contact dependent. In conclusion, human hepatocytes induce a CD4⁺ T cell alloresponse in vitro, which is associated with MHC class II up-regulation on hepatocytes and is susceptible to suppression by Tregs. Liver Transplantation 24 407-419 2018 AASLD.

The Optimization of Short-Term Hepatocyte Preservation Before Transplantation

Background

No optimal methods for short-term hepatocyte preservation have been established. We have recently developed a prominent oxygen-permeable bag (Tohoku Device [TD]) for pancreatic islet culture and transplantation. In this study, we investigated whether TD is also effective for hepatocyte preservation and tried to optimize other conditions.

Methods

Hepatocytes were preserved in the following conditions, and their outcomes were observed. First, the effectiveness of TD was investigated. Second, hepatocyte medium (HM) and organ preservation solutions with or without fetal bovine serum (FBS) were compared. Third, as supplementations, FBS and human serum albumin (HSA) were compared. Fourth, low, room and high temperature were compared. And finally, hepatocytes preserved in various conditions were transplanted into the subrenal capsule space of nonalbumin rats and engrafted areas were assessed.

Results

The survival rate of hepatocytes preserved in TD tended to be higher and their viability and function were maintained significantly greater than those of non-TD group. Irrespective of FBS supplementation, the survival rate of HM group was significantly higher than those of organ preservation solution group while viabilities and plating efficiency were similar among them. Although survival rates of groups without FBS were extremely low, results of HSA supplemented group were not inferior to FBS supplemented group. Hepatocytes preserved at high temperature had the worst results. The engrafted area of TD group tended to be higher than those of other groups.

Conclusions

TD is effective for short-term hepatocyte preservation. HSA is a useful substitute for FBS, and preserving in HM at low temperature is recommended.