Apoptosis Occurs in Isolated and Banked Primary Mouse Hepatocytes

Cryopreservation of the whole testes of Asian sea bass (Lates calcarifer) and its effects on apoptosis, germ cell-specific gene expression, germ cell transplantability, and DNA methylation

Cryopreservation of spermatogonia could be a useful tool to preserve the genetic resources of fish, which could be further restored via germ cell transplantation. In this study, the protocol for the cryopreservation of the spermatogonia of Asian sea bass (Lates calcarifer), an economically important fishery resource in the Indo-West Pacific, was optimised. The impact of the cryopreservation technique on cell viability and apoptosis, expression of several genes related to immature germ cell markers, transplantability in allogeneic recipients, and global DNA methylation was evaluated. The slow-freezing method was performed for the cryopreservation of immature testis tissue, which contains a high proportion of spermatogonia. The optimal condition that yielded the highest recovery rate of post-thawed spermatogonia included a cryomedium containing Leibovitz's (L-15) medium and 10 % dimethyl sulfoxide, ice equilibration for 60 min before freezing, and subsequent thawing at 4 °C for 8 min. Moreover, a higher number of early and late apoptotic cells was detected in the cryopreserved than in the fresh testes, suggesting that apoptosis could result in reduced viability. The expression levels of dazl decreased in the cryopreserved testes; however, there were no significant differences in the expression levels of nanos2 or nanos3 between the fresh and cryopreserved testes. Although qRT-PCR showed lower vasa expression in cryopreserved testicular cells, in situ hybridisation showed expressed vasa in the cryopreserved testicular cells. Post-thawed spermatogonia could be incorporated into the genital ridge of allogeneic recipients, suggesting that cryopreserved spermatogonia exhibit transplantability characteristics. Compared with fresh testes, significant changes in the proportion of DNA methylation (decreased 5-mC and 5-caC) were observed in cryomedium-free testicular cells, whereas those of the cryopreserved cells were not significantly different. Therefore, the method we developed for the cryopreservation of the spermatogonia of Asian sea bass enabled post-thaw cells to retain several stemness characteristics and maintain their epigenetic stability.

Image-guided Ablative Procedures

Various image-guided ablative procedures include chemical and thermal ablation techniques and irreversible electroporation. These have been used for curative intent for small tumours and palliative intent for debulking, immunogenicity and pain control. Understanding these techniques is critical to avoiding complications and achieving superior clinical outcomes. Additionally, combination with immunotherapy and chemotherapies is rapidly evolving. There are numerous opportunities in interventional radiology to advance ablation techniques and seamlessly integrate into current treatment regimens for both benign and malignant tumours.

Parallelized Droplet Vitrification Enables Single-Run Vitrification of the Whole Rat Liver Hepatocyte Yield

Drug discovery pipelines rely on the availability of isolated primary hepatocytes for investigating potential hepatotoxicity prior to clinical application. These hepatocytes are typically isolated from livers rejected for transplantation and subsequently cryopreserved for later usage. The gold-standard cryopreservation technique, slow-freezing, is a labor-intensive process, with significant post-storage viability loss. In this work, we introduce parallelized droplet vitrification, a technique for high-volumetric, rapid vitrification of suspended cells. We show the utility of this technique through the single-run vitrification of the whole-rate liver hepatocyte yield, resulting in a 1600% increase in single-batch vitrification and a 500% increase in droplet generation rate compared to previous droplet vitrification approaches. Additionally, we showed that these implementations maintained improved post-preservation outcomes in primary rat hepatocytes.

Cryopreservation of assay-ready hepatocyte monolayers by chemically-induced ice nucleation: preservation of hepatic function and hepatotoxicity screening capabilities

Cell culture plays a critical role in biomedical discovery and drug development. Primary hepatocytes and hepatocyte-derived cell lines are especially important cellular models for drug discovery and development. To enable high-throughput screening and ensure consistent cell phenotypes, there is a need for practical and efficient cryopreservation methods for hepatocyte-derived cell lines and primary hepatocytes in an assay-ready format. Cryopreservation of cells as adherent monolayers in 96-well plates presents unique challenges due to low volumes being susceptible to supercooling, leading to low recovery and well-to-well variation. Primary cell cryopreservation is also particularly challenging due to the loss of cell viability and function. In this study, we demonstrate the use of soluble ice nucleator materials (IN) to cryopreserve a hepatic-derived cell line (HepG2) and primary mouse hepatocytes, as adherent monolayers. HepG2 cell recovery was near 100% and ∼75% of primary hepatocytes were recovered 24 hours post-thaw compared to just 10% and 50% with standard 10% DMSO, respectively. Post-thaw assessment showed that cryopreserved HepG2 cells retain membrane integrity, metabolic activity, proliferative capacity and differentiated hepatic functions including urea secretion, cytochrome P450 levels and lipid droplet accumulation. Cryopreserved primary hepatocytes exhibited reduced hepatic functions compared to fresh hepatocytes, but functional levels were similar to commercial suspension-cryopreserved hepatocytes, with the added benefit of being stored in an assay-ready format. In addition, normal cuboidal morphology and minimal membrane damage were observed 24 hours post-thaw. Cryopreserved HepG2 and mouse hepatocytes treated with a panel of pharmaceutically active compounds produced near-identical dose-response curves and EC50 values compared to fresh hepatocytes, confirming the utility of cryopreserved bankable cells in drug metabolism and hepatotoxicity studies. Cryopreserved adherent HepG2 cells and primary hepatocytes in 96 well plates can significantly reduce the time and resource burden associated with routine cell culture and increases the efficiency and productivity of high-throughput drug screening assays.

Establishment of a Serum-Free Hepatocyte Cryopreservation Process for the Development of an "Off-the-Shelf" Bioartificial Liver System

To use hepatocytes immediately when necessary for hepatocyte transplantation and bioartificial liver (BAL) systems, a serum-free cryopreservation protocol ensuring the high survival of hepatocytes and maintenance of their functions should be developed. We established a serum-free protocol for the cryopreservation of primary hepatocytes, hepatocyte spheroids, and hepatocyte spheroid beads in liquid nitrogen. The serum-free cryopreservation solutions showed a significantly higher performance in maintaining enhanced viability and ammonia removal, urea secretion, and the albumin synthesis of hepatocyte spheroids and spheroid beads. The serum-free thawing medium, containing human serum albumin (HSA) and N-acetylcysteine (NAC), was compared with a fetal bovine serum-containing thawing medium for the development of a serum-free thawing medium. Our results show that hepatocyte spheroids and spheroid beads thawed using a serum-free thawing medium containing HSA and NAC exhibited increased hepatocyte viability, ammonia removal, urea secretion, and albumin synthesis compared to those thawed using the serum-containing medium. Finally, we evaluated the liver functions of the cryopreserved BAL system-applied serum-free cryopreservation process compared to the fresh BAL system. The ammonia removal efficiency of the cryopreserved hepatocyte spheroids BAL was lower than or similar to that of the fresh BAL system. Additionally, the urea concentrations in the media of all three BAL systems were not significantly different during BAL system operation. This cryopreserved spheroid-based BAL system using a serum-free process will be a good candidate for the treatment of patients.

Assessment of the Impact of Post-Thaw Stress Pathway Modulation on Cell Recovery following Cryopreservation in a Hematopoietic Progenitor Cell Model

The development and use of complex cell-based products in clinical and discovery science continues to grow at an unprecedented pace. To this end, cryopreservation plays a critical role, serving as an enabling process, providing on-demand access to biological material, facilitating large scale production, storage, and distribution of living materials. Despite serving a critical role and substantial improvements over the last several decades, cryopreservation often remains a bottleneck impacting numerous areas including cell therapy, tissue engineering, and tissue banking. Studies have illustrated the impact and benefit of controlling cryopreservation-induced delayed-onset cell death (CIDOCD) through various “front end” strategies, such as specialized media, new cryoprotective agents, and molecular control during cryopreservation. While proving highly successful, a substantial level of cell death and loss of cell function remains associated with cryopreservation. Recently, we focused on developing technologies (RevitalICE™) designed to reduce the impact of CIDOCD through buffering the cell stress response during the post-thaw recovery phase in an effort to improve the recovery of previously cryopreserved samples. In this study, we investigated the impact of modulating apoptotic caspase activation, oxidative stress, unfolded protein response, and free radical damage in the initial 24 h post-thaw on overall cell survival. Human hematopoietic progenitor cells in vitro cryopreserved in both traditional extracellular-type and intracellular-type cryopreservation freeze media were utilized as a model cell system to assess impact on survival. Our findings demonstrated that through the modulation of several of these pathways, improvements in cell recovery were obtained, regardless of the freeze media and dimethyl sulfoxide concentration utilized. Specifically, through the use of oxidative stress inhibitors, an average increase of 20% in overall viability was observed. Furthermore, the results demonstrated that by using the post-thaw recovery reagent on samples cryopreserved in intracellular-type media (Unisol™), improvements in overall cell survival approaching 80% of non-frozen controls were attained. While improvements in overall survival were obtained, an assessment on the impact of specific cell subpopulations and functionality remains to be completed. While work remains, these results represent an important step forward in the development of improved cryopreservation processes for use in discovery science, and commercial and clinical settings.

Control of stress-induced apoptosis by freezing tolerance-associated wheat proteins during cryopreservation of rat hepatocytes

Cryopreservation is used for long-term storage of cells and tissues. Cryoprotectants such as dimethyl disulfoxide (DMSO) are used to protect cells against freeze-thaw damage. Despite the use of cryoprotectants, hepatocytes are sensitive to stresses imposed by freeze and thaw processes, which cause physical damage, loss of functionality, or cell death. As an alternative, we have developed new technology using several recombinant wheat proteins as cryoprotectants: TaENO (enolase), TaBAS1 (2-Cys peroxiredoxin), and a combination of WCS120 (dehydrin) with TaIRI-2 (inhibitor of ice recrystallization). This study aims to understand the mechanisms by which these plant proteins protect rat hepatocytes against cell death incurred during cryopreservation. Our analysis revealed that for cells cryopreserved with DMSO, cell death occurred by apoptosis and necrosis. Apoptosis was detected by activation of effector caspases-3 and -7, PARP cleavage, and nuclear chromatin condensation. These apoptotic events were inhibited when hepatocytes were cryopreserved with the different plant proteins. Cryopreservation with DMSO activated apoptosis through the mitochondrial pathway: the Bax/Bcl-2 protein ratio increased, mitochondrial membrane potential decreased, and initiator caspase-9 was activated. Furthermore, the endoplasmic reticulum pathway of apoptosis was activated: levels of the chaperone Bip/GRP78 decreased, pro-apoptotic transcription factor CHOP was induced, and initiator caspase-12 was activated. Activation of the mitochondrial and endoplasmic reticulum pathways of apoptosis was attenuated when hepatocytes were cryopreserved with the different recombinant proteins. This study improves understanding of mechanisms of cryoprotection provided by these plant proteins during freezing stress. These proteins are natural products and show promising potential by decreasing cell death during cryopreservation of hepatocytes.

Generation of fully functional hepatocyte-like organoids from human induced pluripotent stem cells mixed with Endothelial Cells

Despite advances in stem cell research, cell transplantation therapy for liver failure is impeded by a shortage of human primary hepatocytes (HPH), along with current differentiation protocol limitations. Several studies have examined the concept of co-culture of human induced pluripotent cells (hiPSCs) with various types of supporting non-parenchymal cells to attain a higher differentiation yield and to improve hepatocyte-like cell functions both in vitro and in vivo. Co-culturing hiPSCs with human endothelial cells (hECs) is a relatively new technique that requires more detailed studies. Using our 3D human embryoid bodies (hEBs) formation technology, we interlaced Human Adipose Microvascular Endothelial Cells (HAMEC) with hiPSCs, leading to a higher differentiation yield and notable improvements across a wide range of hepatic functions. We conducted a comprehensive gene and protein secretion analysis of our HLCs coagulation factors profile, showing promising results in comparison with HPH. Furthermore, a stage-specific glycomic analysis revealed that the differentiated hepatocyte-like clusters (HLCs) resemble the glycan features of a mature tissue rather than cells in culture. We tested our HLCs in animal models, where the presence of HAMEC in the clusters showed a consistently better performance compared to the hiPSCs only group in regard to persistent albumin secretion post-transplantation.

Primary hepatocytes and their cultures for the testing of drug-induced liver injury

Drug-induced liver injury is a major reason for discontinuation of drug development and withdrawal of drugs from the market. Intensive efforts in the last decades have focused on the establishment and finetuning of liver-based in vitro models for reliable prediction of hepatotoxicity triggered by drug candidates. Of those, primary hepatocytes and their cultures still are considered the gold standard, as they provide an acceptable reflection of the hepatic in vivo situation. Nevertheless, these in vitro systems cope with gradual deterioration of the differentiated morphological and functional phenotype. The present paper gives an overview of traditional and more recently introduced strategies to counteract this dedifferentiation process in an attempt to set up culture models that can be used for long-term testing purposes. The relevance and applicability of such optimized cultures of primary hepatocytes for the testing of drug-induced cholestatic liver injury is demonstrated.

Engraftment and Function of Intrasplenically Transplanted Cold Stored Rat Hepatocytes

Hepatocellular transplant may potentially be efficacious for the treatment of selected liver metabolic disorders and acute hepatic failure. On the other hand, the use of hepatocyte cold preservation techniques in these transplantation protocols would allow to have available cells at the right time and place and, consequently, make an optimal use of scarce human hepatocytes. In our experiments we evaluated the biodistribution and functionality of cold preserved hepatocytes transplanted in the spleen of syngeneic rats. Isolated hepatocytes were labeled with the fluorescent dye 5(6)-carboxyfluorescein diacetate succinimidyl-ester, cold-preserved in modified University of Wisconsin (UW) solution for 48 or 96 h, and then transplanted into the spleen. Recipient animals were euthanized at 0 and 3 h, and at 1, 2, 3, 5, 10, and 14 days after transplantation for tissue analysis. Labeled hepatocytes were clearly identifiable in the recipient tissues up to 14 days later. Fluorescence microscopy also showed no significant differences in biodistribution when either cold stored or freshly isolated hepatocytes were transplanted. In addition, functional activity of transplanted cells was demonstrated by immunohistochemical detection of albumin at levels comparable to those found in normal hepatocytes. Our findings establish that cold preserved hepatocytes appear morphologically and biochemically normal after intrasplenic transplantation. Consequently, it indicates that modified UW solution makes it possible to safety preserve hepatocytes for up to 96 h before transplantation, perhaps providing sufficient time for hepatocyte allocation and potential recipient preparation, if applicable clinically.

Maintenance of Hepatic Functions in Primary Human Hepatocytes Cultured on Xeno-Free and Chemical Defined Human Recombinant Laminins

Refined methods for maintaining specific functions of isolated hepatocytes under xeno-free and chemical defined conditions is of great importance for the development of hepatocyte research and regenerative therapy. Laminins, a large family of heterotrimeric basement membrane adhesion proteins, are highly cell and tissue type specific components of the extracellular matrix and strongly influence the behavior and function of associated cells and/or tissues. However, detailed biological functions of many laminin isoforms are still to be evaluated. In this study, we determined the distribution of laminin isoforms in human liver tissue and isolated primary human hepatocytes by western blot analysis, and investigated the efficacy of different human recombinant laminin isoforms on hepatic functions during culture. Protein expressions of laminin-chain α2, α3, α4, β1, β3, γ1, and γ2 were detected in both isolated human hepatocytes and liver tissue. No α1 and α5 expression could be detected in liver tissue or hepatocytes. Hepatocytes were isolated from five different individual livers, and cultured on human recombinant laminin isoforms -111, -211, -221, -332, -411, -421, -511, and -521 (Biolamina AB), matrigel (extracted from Engelbreth-Holm-Swarm sarcoma), or collagen type IV (Collagen). Hepatocytes cultured on laminin showed characteristic hexagonal shape in a flat cell monolayer. Viability, double stranded DNA concentration, and Ki67 expression for hepatocytes cultured for six days on laminin were comparable to those cultured on EHS and Collagen. Hepatocytes cultured on laminin also displayed production of human albumin, alpha-1-antitrypsin, bile acids, and gene expression of liver-enriched factors, such as hepatocyte nuclear factor 4 alpha, glucose-6-phosphate, cytochrome P450 3A4, and multidrug resistance-associated protein 2. We conclude that all forms of human recombinant laminin tested maintain cell viability and liver-specific functions of primary human hepatocytes, and that recombinant laminin is a promising xeno-free and chemical defined strategy for preservation of hepatocyte specific function in vitro.

Implications of differential stress response activation following non-frozen hepatocellular storage

Hepatocytes are critical for numerous cell therapies and in vitro investigations. A limiting factor for their use in these applications is the ability to process and preserve them without loss of viability or functionality. Normal rat hepatocytes (NHEPs) and human hepatoma (C3A) cells were stored at either 4°C or 37°C to examine post-processing stress responses. Resveratrol and salubrinal were used during storage to determine how targeted molecular stress pathway modulation would affect cell survival. This study revealed that storage outcome is dependent upon numerous factors including: cell type, storage media, storage length, storage temperature, and chemical modulator. These data implicate a molecular-based stress response that is not universal but is specific to the set of conditions under which cells are stored. Further, these findings allude to the potential for targeted protection or destruction of particular cell types for numerous applications, from diagnostic cell selection to cell-based therapy. Ultimately, this study demonstrates the need for further in-depth molecular investigations into the cellular stress response to bioprocessing and preservation.

Biobanking: The Future of Cell Preservation Strategies

With established techniques cryopreservation is often viewed as an "old school" discipline yet modern cryopreservation is undergoing another scientific and technology development growth phase. In this regard, today's cryopreservation processes and cryopreserved products are found at the forefront of research in the areas of discovery science, stem cell research, diagnostic development and personalized medicine. As the utilization of cryopreserved cells continues to increase, the demands placed on the biobanking industry are increasing and evolving at an accelerated rate. No longer are samples providing for high immediate post-thaw viability adequate. Researchers are now requiring samples where not only is there high cell recovery but that the product recovered is physiologically and biochemically identical to its pre-freeze state at the genominic, proteomic, structural, functional and reproductive levels. Given this, biobanks are now facing the challenge of adapting strategies and protocols to address these needs moving forward. Recent studies have shown that the control and direction of the molecular response of cells to cryopreservation significantly impacts final outcome. This chapter provides an overview of the molecular stress responses of cells to cryopreservation, the impact of the apoptotic and necrotic cell death continuum and how studies focused on the targeted modulation of common and/or cell specific responses to freezing temperatures provide a path to improving sample quality and utility. This line of investigation has provided a new direction and molecular-based foundation guiding new research, technology development and procedures. As the use of and the knowledge base surrounding cryopreservation continues to expand, this path will continue to provide for improvements in overall efficacy and outcome.

Targeting cryopreservation-induced cell death: a review

Despite marked developments in the field of cryopreservation of cells and tissues for research and therapeutic applications, post-thaw cell death remains a significant drawback faced by cryobiologists. Post cryopreservation apoptosis and necrosis are normally observed within 6 to 24 h after post-thaw culture. As a result, massive loss of cell viability and cellular function occur due to cryopreservation. However, in this new generation of cryopreservation science, scientists in this field are focusing on incorporation of apoptosis and necrosis inhibitors (zVAD-fmk, p38 MAPK inhibitor, ROCK inhibitor, etc.) to cryopreservation and post-thaw culture media. These inhibitors target and inhibit various proteins such as caspases, proteases, and kinases, involved in the cell death cascade, resulting in reduced intensity of apoptosis and necrosis in the cryopreserved cells and tissues, increased cell viability, and maintenance of cellular function; thus improved overall cryopreservation efficiency is achieved. The present article provides an overview of various cell death pathways, molecules mediating cryopreservation-induced apoptosis and the potential of certain molecules in targeting cryopreservation-induced delayed-onset cell death.

Mitochondrial staining allows robust elimination of apoptotic and damaged cells during cell sorting

High-speed fluorescence-activated cell sorting is relevant for a plethora of applications, such as PCR-based techniques, microarrays, cloning, and propagation of selected cell populations. We suggest a simple cell-sorting technique to eliminate early and late apoptotic and necrotic cells, with good signal-to-noise ratio and a high-purity yield. The mitochondrial potential dye, TMRE (tetramethylrhodamine ethyl ester perchlorate), was used to separate viable and non-apoptotic cells from the cell sorting samples. TMRE staining is reversible and does not affect cell proliferation and viability. Sorted TMRE(+) cells contained a negligible percentage of apoptotic and damaged cells and had a higher proliferative potential as compared with their counterpart cells, sorted on the basis of staining with DNA viability dye. This novel sorting technique using TMRE does not interfere with subsequent functional assays and is a method of choice for the enrichment of functionally active, unbiased cell populations.

Primary hepatocytes and their cultures in liver apoptosis research

Apoptosis not only plays a key role in physiological demise of defunct hepatocytes, but is also associated with a plethora of acute and chronic liver diseases as well as with hepatotoxicity. The present paper focuses on the modelling of this mode of programmed cell death in primary hepatocyte cultures. Particular attention is paid to the activation of spontaneous apoptosis during the isolation of hepatocytes from the liver, its progressive manifestation upon the subsequent establishment of cell cultures and simultaneously to strategies to counteract this deleterious process. In addition, currently applied approaches to experimentally induce controlled apoptosis in this in vitro setting for mechanistic research purposes and thereby its detection using relevant biomarkers are reviewed.

Evaluating the Effects of Dithiothreitol and Fructose on Cell Viability and Function of Cryopreserved Primary Rat Hepatocytes and HepG2 Cell Line

BACKGROUND

Hepatocytes are used as an in vitro model to evaluate drug metabolism. Human hepatocyte transplant has been considered as the temporary treatment of acute liver failure. Optimization freezing methods is very important to preserve both cell viability and function which are achieved by cryopreservation mostly always.

OBJECTIVES

The present study aimed to investigate the cryoprotective effect of DTT and fructose on primary rat hepatocytes and HepG2 cells.

MATERIALS AND METHODS

Both fresh rat hepatocytes and HepG2 cell line were incubated with fructose (100 and 200 mM) and dithiothreitol (DTT) (25, 50, 100, 250, and 500 μM) at 37°C for 1 and 3 hours, respectively. The preincubated hepatocytes were cryopreserved for two weeks. Hepatocytes viability and function were determined post thawing and the results were compared with the control group.

RESULTS

The viability of both rat hepatocytes and HepG2 cells were significantly increased after one hour preincubation with fructose 200 mM. Preincubation with DTT (50 μM, 100 μM. 250 μM and 500 μM) improved the viability and function upon thawing in both cell types (P < 0.001). In rat hepatocytes, no significant change was observed in albumin, urea production, and LDH leakage after preincubation with fructose or DTT. In HepG2 cells, albumin and urea production were significantly increased after preincubation with DTT (500 μM, 1 hour). The GSH content was significantly increased in DTT (250 and 500 μM, 1 hour) groups in both rat hepatocyte and HepG2 cells.

CONCLUSIONS

Incubation of hepatocytes with fructose and DTT prior to the cryopreservation can increase the cell viability and function after thawing.

Influence of platelet lysate on the recovery and metabolic performance of cryopreserved human hepatocytes upon thawing

BACKGROUND

Storage of human hepatocytes is essential for their use in research and liver cell transplantation. However, cryopreservation and thawing (C/T) procedures have detrimental effects on the viability and functionality compared with fresh cells. The aim of this study was to upgrade the standard C/T methodology to obtain better quality hepatocytes for cell transplantation to improve the overall clinical outcome.

METHODS

Human hepatocytes isolated from donor livers were cryopreserved in University of Wisconsin solution with 10% dimethyl sulfoxide (standard medium), which was supplemented with 10% or 20% of platelet lysate. Thawing media supplemented with up to 30 mM glucose was also investigated. The effects on cell viability, adhesion proteins (e-cadherin, β-catenin, and β1-integrin) expression, attachment efficiency, apoptotic indicators, Akt signaling, ATP levels, and cytochrome P450 activities have been evaluated.

RESULTS

The results indicate that the hepatocytes cryopreserved in a medium supplemented with platelet lysate show better recovery than those preserved in the standard medium: higher expression of adhesion molecules, higher attachment efficiency and cell survival; decreased number of apoptotic nuclei and caspase-3 activation; maintenance of ATP levels; and drug biotransformation capability close to those in fresh hepatocytes. Supplementation of thawing media with glucose led to a significant decrease in caspase-3 activation and to increased adhesion molecules preservation and Akt signal transduction after C/T. Minor nonsignificant changes in cell viability and attachment efficiency were observed.

CONCLUSIONS

These promising results could lead to a new cryopreservation procedure to improve human hepatocyte cryopreservation outcome.

Current development of bioreactors for extracorporeal bioartificial liver (Review)

The research and development of extracorporeal bioartificial liver is gaining pace in recent years with the introduction of a myriad of optimally designed bioreactors with the ability to maintain long-term viability and liver-specific functions of hepatocytes. The design considerations for bioartificial liver are not trivial; it needs to consider factors such as the types of cell to be cultured in the bioreactor, the bioreactor configuration, the magnitude of fluid-induced shear stress, nutrients' supply, and wastes' removal, and other relevant issues before the bioreactor is ready for testing. This review discusses the exciting development of bioartificial liver devices, particularly the various types of cell used in current reactor designs, the state-of-the-art culturing and cryopreservation techniques, and the comparison among many today's bioreactor configurations. This review will also discuss in depth the importance of maintaining optimal mass transfer of nutrients and oxygen partial pressure in the bioreactor system. Finally, this review will discuss the commercially available bioreactors that are currently undergoing preclinical and clinical trials.

Use of a clinically approved iron oxide MRI contrast agent to label human hepatocytes

Reliable noninvasive methods are needed to monitor cell engraftment and graft survival after hepatocyte transplantation. Superparamagnetic iron oxide nanoparticles (SPIOs) have been shown to accumulate in various types of cells, and are currently the labeling agent of choice for cellular magnetic resonance imaging (MRI). However, for successful clinical translation to hepatocyte transplantation, it is important that hepatocytes maintain their viability and synthetic function after labeling. In this study, primary human hepatocytes were incubated with increasing concentrations of clinical grade SPIOs for different time intervals. SPIOs uptake was confirmed by light and fluorescence microscopy, and intracellular iron content quantified by a colorimetric ferrozine-based assay. Studies were performed to determine if labeling affected cell viability and function. Intracellular iron concentrations increased in a time- and dose-dependent manner after incubation with SPIOs. Labeling had minimal short-term effects on cell attachment and mitochondrial function. However, exposure of hepatocytes to SPIOs resulted in a dose- and time-dependent reduction in protein synthesis. Cell labeling for 16 h had no significant effect on hepatocyte-specific function, but longer periods of incubation resulted in a dose-dependent decrease in albumin production. Hepatocytes incorporated SPIOs at sufficient levels for in vitro detection on a 7-T MRI imaging system, with a minimum of 2,000 SPIO-labeled cells/μl detected by a decreased T2 relaxivity compared to controls. Intrasplenic transplantation of human hepatocytes labeled with 50 μg Fe/ml of SPIOs was performed in nonobese diabetic/severe combined immune deficiency (NOD-Scid) mice. Recipient livers showed a clear decrease in signal intensity on T2*-weighted MR images when compared to controls, allowing detection of hepatocytes. With further experiments to optimize the conditions for labeling human hepatocytes, it should be possible to apply this technique to track hepatocyte transplantation in patients with liver disease.

Mushroom lectin protects arsenic induced apoptosis in hepatocytes of rodents

Acute and chronic arsenic exposure result in toxicity both in human and animal beings and cause many hepatic and renal manifestations. The present study stated that mushroom lectin prevents arsenic-induced apoptosis. Apoptosis was measured by morphological alterations, cell proliferation index (CPI), phagocytic activity (nitro blue tetrazolium index; NBT), nitric oxide (NO) production, terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay, DNA fragmentation and caspase-3 activity. Arsenic exposure at 5 μM in the form of sodium arsenite resulted in significant elevation of deformed cells, NO production, TUNEL stained nuclei of hepatocytes, DNA fragmentation and caspase-3 activity. But the CPI and NBT index were significantly declined in arsenic-treated hepatocytes. The beneficial effect of mushroom lectin at 10 μg/mL, 20 μg/mL and 50 μg/mL) showed increased CPI and phagocytic activity. Mushroom lectin at those concentrations reduced deformed cells, NO production, DNA fragmentation and caspase-3 activity of hepatocytes. But significant better protection was observed in 50 μg/mL mushroom lectin-treated hepatocytes. This finding may be of therapeutic benefit in people suffering from chronic arsenic exposure.

Inhibition of oxidative stress and apoptosis enables extended maintenance of integrity and function of isolated hepatocytes in suspension

AIMS

Isolated hepatocytes in suspension may offer an alternative culture system for bioartificial liver devices. However, maintenance of isolated hepatocyte suspensions in conventional media leads to rapid loss of cell integrity. The aim of this study was to develop a modified medium to better maintain hepatocyte integrity.

METHODS

Isolated rat hepatocytes were prepared by collagenase digestion. Hepatocytes were purified in a Percoll gradient, suspended in bicarbonate buffered isotonic saline supplemented with d-alpha-tocopherol succinate and glucose and medium changed at 24 h (modified medium). The properties of cells treated this way were compared with those prepared by collagenase digestion and suspension in bicarbonate buffered isotonic saline (basic medium). Both media were maintained at 30 degrees C for 48 h on an orbital shaker. Markers for oxidative stress, apoptosis and metabolic function were measured enzymatically. Cell morphology was assessed by electron microscopy.

RESULTS

When compared to collagenase-isolated hepatocytes maintained in basic medium, hepatocytes purified by Percoll (Amersham Biosciences, Castle Hill, Australia) and maintained in modified medium demonstrated significantly increased glutathione (GSH) and GSH : glutathione disulphide (GSSH) ratios, decreased lipid peroxidation product formation, decreased caspase-3 protease activity, reduced uptake of trypan blue and loss of lactate dehydrogenase (LDH) and increase preservation of cellular adenosine triphosphate concentration ([ATP]), urea synthesis, ammonia removal and glycogen content. Cell morphology was substantially preserved following 48 h of maintenance in the modified medium.

CONCLUSIONS

The use of Percoll and modified medium reduces cell injury and apoptosis and greatly improves maintenance of cell function and morphology. The modifications reported here and the use of isolated hepatocyte suspensions in bioartificial liver devices are worthy of further investigation.

Differential effects of curcumin on cryopreserved versus fresh primary human hepatocytes

Curcumin (CUR) is a major component of a dietary spice derived from the roots of Curcuma longa. It has strong antioxidant activities and hepatoprotective properties. Primary human hepatocytes are clinically used in transplantation or in bioartificial liver devices for the treatment of patients with liver failure. Fresh and cryopreserved hepatocytes are also used in vitro for the study of drugs in pharmacotoxicology. We aimed to assess whether CUR could improve human liver cell viability and prevent oxidative damage responsible for large cell loss during cell preparation. Our study showed beneficial effects of CUR (25 microM) on freshly isolated human hepatocytes, increasing significantly metabolic activity of viable attached cells when seeded with CUR for 24 h. However CUR added during the cell isolation process did not have any significant impact on cell isolation outcomes or on cryopreservation outcomes. Conversely, CUR added during the thawing of frozen cells had a negative effect on the cell attachment capacity of hepatocytes that were cryopreserved in the presence or absence of CUR. In conclusion, although having positive effects on viability and challenge of oxidative stress on cultured human hepatocytes, CUR had no beneficial effect on cell isolation or cryopreservation outcomes.

The Effect of Cryopreservation on Umbilical Cord Blood Endothelial Progenitor Cell Differentiation

Endothelial progenitor cells (EPCs) has been shown to be present in umbilical cord blood (UCB) in addition to hematopoietic stem cells. Cryopreservation is the accepted method for long-term storage of UCB. However, whether EPCs can be derived from cryopreserved UCB samples is unclear. The aim of this study was to investigate the differentiation potential of EPCs from cryopreserved CB samples. CD34+ cells were isolated from fresh or frozen and thawed UCB using magnetic beads. Cells were then cultured on fibronectincoated plates containing endothelial differentiation medium. After 4–5 weeks in culture, endothelial-like cells were generated from fresh UCB samples, but not cryopreserved UCB samples. Examining this further, both fresh and frozen/thawed UCB MNCs were stained with Annexin V-PE and 7-actinomycin D (7-AAD) using flow cytometry. We found that there were a significant number of apoptotic cells in cryopreserved UCB samples compared to fresh UCB samples. In conclusion, cryopreservation induced UCB cell apoptosis and impaired EPC differentiation.

Comparison of University of Wisconsin and ET-Kyoto preservation solutions for the cryopreservation of primary human hepatocytes

Primary human hepatocytes are clinically used for transplantation or in bioartificial liver devices for the treatment of patients with liver failure. We aimed to assess whether an organ preservation solution containing trehalose, namely ET-Kyoto solution (ETK), could improve human liver cell viability when used for cryopreservation in comparison to the University of Wisconsin solution (UW). Our study showed beneficial effects of ETK when used in combination with other cryoprotectants on the viability of thawed hepatocytes. Indeed, no significant difference was seen between the viability of freshly isolated cells and cryopreserved cells when cryopreserved with ETK combined with other cryoprotectants. In contrast, a significant decrease of viability was observed in cells cryopreserved with UW or ETK combined with dimethysulfoxide (DMSO) only, or with UW combined with other cryoprotectants, compared to freshly isolated cells. No significant difference was observed between the four different groups of cryopreserved hepatocytes with regards to cell recovery rate or cell attachment after thawing. However, a significant decrease in cell metabolic activity was found in cells cryopreserved with UW 10% DMSO compared to the other groups. In conclusion, our study confirms the beneficial effect of ETK for the cryopreservation of human hepatocytes in combination with other cryoprotective agents.

Cryopreservation-induced nonattachment of human hepatocytes: role of adhesion molecules

Good quality cryopreserved human hepatocytes are becoming an important source for clinical hepatocyte transplantation. However, the process of cryopreservation leads to both structural and functional impairment of hepatocytes. The aim of this study was to investigate the mechanisms of cryopreservation-induced nonattachment in human hepatocytes. Hepatocytes were cryopreserved after isolation from unused donor liver tissue. Cell attachment to collagen-coated plates was measured. A cDNA gene array system for 96 cell adhesion-related molecules was used to determine mRNA expression in fresh and cryopreserved hepatocytes. Two cell adhesion molecule proteins were investigated further: beta1-integrin, a cell-matrix adhesion molecule, and E-cadherin, a cell-cell adhesion molecule. Attachment efficiency was significantly decreased after cryopreservation of human hepatocytes. Twenty-two genes were downregulated after cryopreservation including integrins, cadherins, catenins, and matrix metalloproteinases (MMPs). Beta1-Integrin gene and protein expression were significantly decreased in cultured cryopreserved hepatocytes compared to fresh hepatocytes. There was a significant correlation between loss of beta1-integrin and attachment in cryopreserved cells. Degradation of E-cadherin was increased in cryopreserved hepatocytes. The process of cryopreservation leads to downregulation of cell adhesion molecules at the gene and the cellular level. New cryopreservation protocols are needed to prevent these effects on cell attachment.

Sub-lethal concentration of arsenic interferes with the proliferation of hepatocytes and induces in vivo apoptosis in Clarias batrachus L

We studied the hepatocellular alterations induced by sub-lethal concentrations (0.50 muM) of arsenic in Indian catfish Clarias batrachus L. Sub-lethal arsenic exposure altered serum aspartate aminotransferase and alkaline phosphatase levels and brought about significant changes in different serum biochemical parameters. Arsenic exposure reduced total hepatocyte protein content and suppressed the proliferation of hepatocytes in a time-dependent manner. Routine histological studies on liver documented arsenic-induced changes characterized by dilated sinusoids, formation of intracellular edema, megalocytosis, vacuolation and appearance of hepatic cells with distorted nuclei. Transmission electron microscopy of hepatocytes further revealed hyperplasia and hypertrophy of mitochondria, development of dilated rough endoplasmic reticulum and changes in peroxisome size with duration of arsenic exposure. Degeneration of mitochondrial cristae and condensation of chromatin was also evident in arsenic-exposed hepatocytes. A significant number of hepatocytes isolated from arsenic-exposed fish stained with annexin V and demonstrated DNA ladder characteristic of apoptosis. Single-cell gel electrophoresis of exposed hepatocytes also revealed the development of comets usually seen in apoptotic cells. Using specific inhibitors it was determined that the arsenic-induced apoptosis of hepatocytes was caspase-mediated, involving the caspase 3 pathway.

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.

Cryopreservation of isolated human hepatocytes for transplantation: State of the art

Hepatocytes isolated from unused donor livers are being used for transplantation in patients with acute liver failure and liver-based metabolic defects. As large numbers of hepatocytes can be prepared from a single liver and hepatocytes need to be available for emergency and repeated treatment of patients it is essential to be able to cryopreserve and store cells with good thawed cell function. This review considers the current status of cryopreservation of human hepatocytes discussing the different stages involved in the process. These include pre-treatment of cells, freezing solution, cryoprotectants and freezing and thawing protocols. There are detrimental effects of cryopreservation on hepatocyte structure and metabolic function, including cell attachment, which is important to the engraftment of transplanted cells in the liver. Cryopreserved human hepatocytes have been successfully used in clinical transplantation, with evidence of replacement of missing function. Further optimisation of hepatocyte cryopreservation protocols is important for their use in hepatocyte transplantation.

The effect of antioxidants and a caspase inhibitor on cryopreserved rat hepatocytes

Hepatocyte transplantation and use of bioartificial liver support systems have been suggested as potential therapies for fulminant hepatic failure. Cryopreservation in liquid nitrogen is presently the major method of long-term storage of isolated hepatocytes. However, cryopreservation can result in low cell recovery and reduction in differentiated function. Several possible mechanisms of cell death during cryopreservation have been proposed. The most important mechanisms appear to be oxidative stress and apoptosis. In this study, we isolated fresh rat hepatocytes and cryopreserved them in three media: University of Wisconsin (UW) solution, an antioxidant-containing medium, and medium containing a caspase inhibitor. Viability and function of hepatocytes cryopreserved in these media were examined. Cryopreservation conditions had no effect on hepatocyte viability after thawing. However, after culture we found significant improvements in viability and function in both antioxidant- and caspase inhibitor-treated hepatocytes at 6 and 24 h.

Role of apoptotic signaling pathway in metabolic disturbances occurring in liver tissue after cryopreservation: Study on rat precision-cut liver slices

Precision-cut liver slices in culture (PCLS) appears as a useful and widely used model for metabolic studies; the interest to develop an adequate cryopreservation procedure, which would allow maintaining cell integrity upon incubation, is needed to extend its use for human tissues. We have previously shown that cryopreservation of rat PCLS leads to caspase-3 activation and early alterations of their K+ content upon incubation. In this study, we tested the hypothesis that counteracting intracellular K+ loss and/or interfering with cell death signaling pathways could improve the viability of cryopreserved PCLS. PCLS were prepared from male Wistar rat liver and cryopreserved by rapid freezing before incubation. The addition of a caspase inhibitor-Z-DEVD-FMK (2.5 microM)-in the culture medium did not improve viability of cryopreserved PCLS. Incubation of cryopreserved PCLS in a K+ rich medium (135 mM) increased K+ content and avoided caspase-3 activation, but did not improve cell viability. Caspase-3 inhibition, a decrease in cell lysis, and improvement of glycogen content were observed in cryopreserved PCLS after addition of LiCl (100 mM) in the incubation medium. These results indicate that, even if caspase-3 activation is linked to the K+ loss in cryopreserved PCLS, its inhibition does not allow restoring the metabolic capacities. LiCl, acting on a target upstream of caspase-3 inhibition, improves cell viability and allows glycogen accumulation when added in culture medium of cryopreserved PCLS; and could thus be considered as an interesting adjuvant in the culture of cryopreserved PCLS.

Hypothermia inhibits Fas-mediated apoptosis of primary mouse hepatocytes in culture

Apoptosis occurs during the isolation and even short-term storage and culture of hepatocytes, and in the pathogenesis of liver diseases, such as hepatic failure and hepatitis. Therapeutic hypothermia has beneficial effects in experimental models of fulminant hepatic failure. The mechanisms underlying the potential benefits of mild hypothermia on the liver have not been well investigated. We examined the effects of temperature on soluble Fas ligand-induced apoptosis in freshly isolated mouse hepatocytes. Decreasing the culture temperature from 37 degrees C to 32 degrees C produced significant suppression of Fas-mediated apoptosis in cultured hepatocytes over a 12-h period. This observation was supported by cell morphology, flow cytometry analysis of cellular DNA content, and Annexin V-FITC staining of membrane phosphatidylserine translocation. In hypothermic conditions, Fas-mediated cytochrome c release from mitochondria of hepatocytes and the proximate downstream activation of caspase-9 were suppressed under mild hypothermic conditions. Effector caspase-7 activity was also inhibited at 32 degrees C. In contrast, the activation of initiator caspase-8 and cleavage of Bid were not affected after Fas-ligand stimulation. These findings suggest that mild hypothermia suppresses Fas-mediated apoptosis of liver cells by the partial inhibition of signaling events including mitochondrial damage, cytochrome c release, and subsequent apoptosome formation and effector caspase activation.

Optimization of conditions for clinical human hepatocyte infusion

Cytotoxicity and apoptosis are common problems in the isolation and storage of human hepatocytes. In vitro environments of hepatocytes during cell infusion may be critical to reducing cellular damage and enhancing cell viability. We examined the effects of donor liver histology (40-50% steatosis vs. normal), incubation time, temperature, and three solutions for infusion on banked primary human hepatocytes, by studying: trypan blue exclusion, AST release, LDH release, MTT assay, detection of DNA ladder, and a hepatocyte proliferation assay. In addition, the microstructure functions of the endoplasmic reticulum and mitochondria of the intact hepatocytes were determined by measuring correlates of UGT 1A1 and cytochrome P-450 3A (CYP3A4) activity. In general, hepatocyte viability decreased significantly within 60 min after thawing. Cells suspended in 5% dextrose lactated Ringers solution (D5LR) maintained greater cell viability. Hepatocytes from normal liver donors showed less AST and LDH enzyme leak in comparison with cells from fatty liver donors. Mild hypothermic temperature (32 degrees C) inhibited cellular damage that otherwise significantly increased at 60 min. Hepatocytes did not proliferate until 12 h from thaw, regardless of supernatant or conditions of suspension. CYP3A4 activity and a marker for UGT 1A1 activity in hepatocytes from normal donor livers were higher than those from steatotic donor livers. These findings suggest that hepatocytes suspended for infusion after isolation from normal liver donors have normal biological functions and less cellular damage/necrosis in contrast with those isolated from fatty liver donors. These damages are inhibited significantly by maintaining hepatocytes at a mild hypothermic temperature (32 degrees C). D5LR alone maintained the best cell viability for up to 60 min. Media of D5LR + adenosine and HMM were able to partially inhibit hepatocyte apoptosis in hepatocytes from steatotic livers.

CD154-CD40 interactions drive hepatocyte apoptosis in murine fulminant hepatitis

The CD154-CD40 interaction is a critical costimulatory pathway modulating the cellular immune response. Moreover, fulminant hepatitis of various etiologies is characterized by a hepatic influx of CD154-expressing T cells and an upregulation of CD40 expression on Kupffer cells and hepatocytes, implicating this pathway in the pathogenesis of fulminant hepatitis. In this study, we used a murine model of fulminant hepatitis induced by concanavalin A (con A) and documented a significant influx of CD154-expressing T cells into the livers of mice treated with con A, in association with markedly increased expression of CD40 restricted mainly to hepatocytes in damaged areas of the liver. Furthermore, con A hepatitis in CD154-deficient mice was significantly attenuated compared with that in wild-type controls and was associated with a decrease in hepatic tumor necrosis factor alpha (TNF-alpha) levels and hepatocyte death. We next determined the role of the CD154-CD40 pathway in hepatocyte death in vitro. These in vitro studies demonstrated that TNF-alpha induces CD40 expression in hepatocytes and that subsequent activation of CD40 results in hepatocyte apoptosis mediated at least in part by enhanced hepatocyte expression of FasL. In conclusion, CD154 stimulation of CD40 plays a central role in hepatocyte death in fulminant hepatitis through direct and indirect pathways that may have direct therapeutic implications in humans. Supplementary material for this article can be found on the HEPATOLOGY website (http://interscience.wiley.com/jpages/0270-9139/suppmat/index.html).

Ultrastructural and functional investigations of adult hepatocyte spheroids during in vitro cultivation

Cultivation of primary adult hepatocytes creates a challenge because of their loss of hepatocellular functions if prevented from attaining polarized cell-cell and cell-matrix interactions. Thus, when hepatocytes are seeded in nonadhesive porous alginate scaffolds, they form 100-microm-diameter spheroids with enhanced cell-cell interactions. Using transmission electron microcopy (TEM), histology, and functional studies, we investigated the state of hepatocyte spheroids during in vitro cultivation. TEM of day 3 spheroids revealed multiple cell layers, with tight junctions between adjacent cells and microvillus-lined channels that resembled bile canaliculi, both structurally and functionally. When copper ions were added to the external medium, the spheroidal hepatocytes performed endocytosis and eventually secreted the heavy metal ions into the bile lumens. From day 8 on, however, there was a rapid decline in cell viability. Histology and TEM analysis of day 13 spheroids revealed a necrotic center, with one viable cell layer on the outskirts. The absence of DNA laddering and negative results in TUNEL assay indicated that apoptosis is not the main process leading to cell death. Cell necrosis may be a result of accumulated bile secretions in the compacted spheroids. Collectively, our results suggest that spheroids derived from adult hepatocytes may have limited utility in long-term applications.

Toward the survival and function of xenogeneic hepatocyte grafts

Xenogeneic hepatocyte transplantation might offer an unobtrusive alternative to whole liver allotransplantation. Having previously found that the immune response to such grafts can be controlled by immunosuppression, we sought approaches to collection and delivery that would optimize survival and function after transplantation. Porcine hepatocytes were isolated by a 2-step collagenase technique and then: 1) used immediately; 2) stored in University of Wisconsin (UW) solution at 4 degrees C; 3) cultured in supplemented Williams E medium; or 4) cryopreserved in UW solution with 10% dimethyl sulfoxide (DMSO). The fate and function of the hepatocytes was determined after they were injected into the spleens of immunodeficient mice. Freshly isolated hepatocytes had better viability (92.2 +/- 1.9%) than hepatocytes cultured for 24 hours (78.4 +/- 6.3%), hypothermically preserved in UW solution for 24 hours (85.8 +/- 3.1%), or cryopreserved (65.0 +/- 2.6%). Freshly isolated hepatocytes secreted more albumin after transplantation than hepatocytes that were cultured, hypothermically stored, or cryopreserved. In conclusion, culture and storage profoundly compromises the function of isolated hepatocytes after transplantation. Freshly isolated hepatocytes are the preferred source for transplantation.

IFN-gamma promotes Fas ligand- and perforin-mediated liver cell destruction by cytotoxic CD8 T cells

To study liver cell damage by CTL, CD8 T cells from P14 TCR transgenic (tg) mice specific for the gp33 epitope of lymphocytic choriomeningitis virus with either deficiency in IFN-gamma (P14.IFN-gamma(null)), functional Fas ligand (P14.gld), or perforin (P14.PKO) were transferred into H8 tg mice ubiquitously expressing gp33 Ag. Treatment of H8 recipient mice with agonistic anti-CD40 Abs induced vigorous expansion of the transferred P14 T cells and led to liver cell destruction determined by increase of glutamate dehydrogenase serum levels and induction of caspase-3 in hepatocytes. Liver injury was mediated by the Fas/Fas ligand (FasL) pathway and by perforin, because P14.gld and P14.PKO T cells failed to induce increased glutamate dehydrogenase levels despite strong in vivo proliferation. In addition, H8 tg mice lacking Fas were resistant to the pathogenic effect of P14 T cells. Besides FasL and perforin, IFN-gamma was also required for liver cell damage, because P14.IFN-gamma(null) T cells adoptively transferred into H8 mice failed to induce disease. Moreover, Fas expression on hepatocytes from H8 recipient mice was increased after transfer of wild-type compared with P14.IFN-gamma(null) T cells, and wild-type P14 T cells expressed higher levels of FasL than P14 T cells lacking IFN-gamma. Thus, our data suggest that IFN-gamma released by activated CD8 T cells upon Ag contact facilitates liver cell destruction.

Long-term function of cryopreserved rat hepatocytes in a coculture system

The goal of this study was to investigate postpreservation long-term function of cryopreserved primary rat hepatocytes using the hepatocyte/3T3-J2 fibroblast coculture system. The long-term function of thawed hepatocytes cocultured with fibroblasts was evaluated and compared with hepatocytes cultured without fibroblasts. Fresh isolated primary rat hepatocytes were frozen at a controlled rate (-1 degrees C/min) up to -80 degrees C, and then stored in liquid nitrogen for up to 90 days. Thawed hepatocytes were thereafter cocultured with 3T3-J2 murine fibroblasts and cocultivation was monitored for 14 days. The viability of fresh isolated hepatocytes was 91.4%, and that of cryopreserved hepatocytes was 82.1%. Cellular morphology and polarity, which were determined by the localization of actin filaments and connexin-32, were successfully maintained in cryopreserved hepatocytes following cryopreservation. Albumin and urea synthesis reached the maximum level and became stable after day 7 in coculture in both fresh and cryopreserved hepatocytes. Urea synthesis of cryopreserved hepatocytes was maintained 89.0% of nonfrozen fresh control, and albumin production of cryopreserved hepatocytes was 63.7% of control in coculture. Cytochrome P450 activity, which was measured by deethylation of ethoxyresorufin, was also maintained in cryopreserved hepatocytes at 88.6% of nonfrozen fresh control in coculture. The retention of synthetic and detoxification activities was verified to be well preserved during extended low-temperature storage (90 days). Both fresh control and cryopreserved hepatocytes cultured without fibroblast did not retain their synthetic and detoxification functions in long-term culture. These data illustrate that, through the utilization of our cryopreservation procedure, primary hepatocyte function was successfully maintained when placed into coculture configuration following thawing.

Anoikis: roadblock to cell transplantation?

Cell therapy, in particular liver cell transplantation, holds great therapeutic potential and is partially hindered by the high rate of apoptosis during cell isolation, cryopreservation, and engraftment. Apoptosis occurring due to cell detachment from the extracellular matrix is a phenomenon termed "anoikis." The purpose of this review is to describe signaling mechanisms pertinent to anoikis in both immortalized cell lines, but particularly in primary normal epithelial cells. The mechanisms described include integrin signaling and survival molecules, caspase activation, and the role of mitochondrial proteins in anoikis. Strategies to prevent anoikis during isolation and cryopreservation of hepatocytes are discussed.

A novel method for liver repopulation: Heterografting of micro-liver slices in a rat model

The field of hepatocyte transplantation is developing, with encouraging results. However, current approaches are still unsuitable for human cell therapy, and safer and more applicable methods need to be developed. We recently successfully transplanted pieces of liver tissue (slices), cut from a wild-type Fischer 344 dipeptidyl peptidase IV (DPP IV)-positive rat and introduced into the liver of a DPP IV-deficient Fischer 344 rat. One month after the procedure, positive DPP IV enzymatic activity was detected in transplanted liver slices. These results suggest that transplantation of tissue slices is feasible and safe and could serve as a promising alternative to hepatocyte transplantation.

Multidisciplinary utilization of dimethyl sulfoxide: pharmacological, cellular, and molecular aspects

DMSO is an amphipathic molecule with a highly polar domain and two apolar methyl groups, making it soluble in both aqueous and organic media. It is one of the most common solvents for the in vivo administration of several water-insoluble substances. Despite being frequently used as a solvent in biological studies and as a vehicle for drug therapy, the side-effects of DMSO (undesirable for these purposes) are apparent from its utilization in the laboratory (both in vivo and in vitro) and in clinical settings. DMSO is a hydrogen-bound disrupter, cell-differentiating agent, hydroxyl radical scavenger, intercellular electrical uncoupler, intracellular low-density lipoprotein-derived cholesterol mobilizing agent, cryoprotectant, solubilizing agent used in sample preparation for electron microscopy, antidote to the extravasation of vesicant anticancer agents, and topical analgesic. Additionally, it is used in the treatment of brain edema, amyloidosis, interstitial cystitis, and schizophrenia. Several systemic side-effects from the use of DMSO have been reported, namely nausea, vomiting, diarrhea, hemolysis, rashes, renal failure, hypertension, bradycardia, heart block, pulmonary edema, cardiac arrest, and bronchospasm. Looking at the multitude of effects of DMSO brought to light by these studies, it is easily understood how many researchers working with DMSO (or studying one of its specific effects) might not be fully aware of the experiences of other groups who are working with it but in a different context.