Improved cryopreservation of human hepatocytes using a new xeno free cryoprotectant solution

Comparative cryopreservation of bovine and porcine primary hepatocytes

The isolation of primary hepatocytes from liver tissue of farm animals yields a very high number of cells, and a part of them can be stored by cryopreservation for future experiments. As no experience exists with the cryopreservation of hepatocytes from cattle, our study aimed at the cryopreservation of bovine hepatocytes by use of different protocols compared with the cryopreservation of hepatocytes from pig. We tested different freezing media (William's Medium E vs. University of Wisconsin solution), cryoprotectants (dimethyl sulfoxide with vs. without trehalose as additional additive), freezing systems (standard freezing container vs. controlled-rate freezer) and freezing times (4 vs. 28 d). These tests identified a general influence of species and freezing systems, whereas the influence of freezing media, trehalose additive and freezing time was less or not obvious. In this regard, we determined a mean recovery of 30% of bovine hepatocytes and 55% of porcine hepatocytes cryopreserved in a controlled-rate freezer, whereas the rates were about 10% less when hepatocytes were frozen in a standard freezing container. In accordance with this observation, the cultivation of cryopreserved hepatocytes from cattle was less effective than that of porcine hepatocytes. Hepatocytes from cattle can be successfully cryopreserved and partially cultured after cryopreservation but with lower percentage than porcine hepatocytes.

Procurement and Evaluation of Hepatocytes for Transplantation From Neonatal Donors After Circulatory Death

Hepatocyte transplantation is a promising treatment for liver failure and inborn metabolic liver diseases, but progress has been hampered by a scarcity of available organs. Here, hepatocytes isolated from livers procured for a neonatal hepatocyte donation program within a research setting were assessed for metabolic function and suitability for transplantation. Organ donation was considered for infants who died in neonatal intensive care in the Stockholm region during 2015–2021. Inclusion was assessed when a decision to discontinue life-sustaining treatment had been made and hepatectomy performed after declaration of death. Hepatocyte isolation was performed by three-step collagenase perfusion. Hepatocyte viability, yield, and function were assessed using fresh and cryopreserved cells. Engraftment and maturation of cryopreserved neonatal hepatocytes were assessed by transplantation into an immunodeficient mouse model and analysis of the gene expression of phase I, phase II, and liver-specific enzymes and proteins. Twelve livers were procured. Median warm ischemia time (WIT) was 190 [interquartile range (IQR): 80–210] minutes. Median viability was 86% (IQR: 71%–91%). Median yield was 6.9 (IQR: 3.4–12.8) x10⁶ viable hepatocytes/g. Transplantation into immunodeficient mice resulted in good engraftment and maturation of hepatocyte-specific proteins and enzymes. A neonatal organ donation program including preterm born infants was found to be feasible. Hepatocytes isolated from neonatal donors had good viability, function, and engraftment despite prolonged WIT. Therefore, neonatal livers should be considered as a donor source for clinical hepatocyte transplantation, even in cases with extended WIT.

Drug metabolic stability in early drug discovery to develop potential lead compounds

Knowledge of the metabolic stability of a new drug substance eliminated by biotransformation is essential for envisaging the pharmacokinetic parameters required for deciding drug dosing and frequency. Strategies aimed at modifying lead compounds may improve metabolic stability, thereby reducing the drug dosing frequency. Replacement of selective hydrogens with deuterium can effectively enhance the drug's metabolic stability by increasing the biological half-life. Further, cyclization, change in ring size, and chirality can substantially improve the metabolic stability of drugs. The microsomal t_1/2 approach for measuring drug in vitro intrinsic clearance by automated LC-MS/MS offers sensitive high-throughput screens with reliable data. The obtained in vitro intrinsic clearance from metabolic stability data helps predict the drug's in vivo total clearance using different scaling factors and hepatic clearance models. This review summarizes all the recent approaches and technological advancements in metabolic stability studies for narrowing down the potential lead compounds in drug discovery. Further, we summarized the potential pitfalls and assumptions made during the in vivo intrinsic clearance estimation from in vitro intrinsic clearance.

Human serum albumin and chromatin condensation rescue ex vivo expanded γδ T cells from the effects of cryopreservation

Clinical applications of gamma delta (γδ) T cells have advanced from initial interest in expanding γδ T cells in vivo to the development of a manufacturing process for the ex vivo expansion. To develop an "off-the-shelf" allogeneic γδ T cell product, the cell manufacturing process must be optimized to include cryopreservation. It is known that cryopreservation can dramatically reduce viability of primary cells and other cell types after thawing, although the exact effects of cryopreservation on γδ T cell health and functionality have not yet been characterized. Our aim was to characterize the effects of a freeze/thaw cycle on γδ T cells and to develop an optimized protocol for cryopreservation. γδ T cells were expanded under serum-free conditions, using a good manufacturing practice (GMP) compliant protocol developed by our lab. We observed that cryopreservation reduced cell survival and increased the percentage of apoptotic cells, two measures that could not be improved through the use of 5 GMP compliant freezing media. The choice of thawing medium, specifically human albumin (HSA), improved γδ T cell viability and in addition, chromatin condensation prior to freezing increased cell viability after thawing, which could not be further improved with the use of a general caspase inhibitor. Finally, we found that cryopreserved cells had depolarized mitochondrial membranes and reduced cytotoxicity when tested against a range of leukemia cell lines. These studies provide a detailed analysis of the effects of cryopreservation on γδ T cells and provide methods for improving viability in the post-thaw period.

Cryopreservation of peripheral blood mononuclear cells using uncontrolled rate freezing

Peripheral blood mononuclear cells are widely used as source material for anticancer immunotherapies. The conventional cryopreservation method for peripheral blood mononuclear cells is time-consuming and expansive, which involves controlled rate freezing followed by storage in liquid nitrogen. Instead, the convenient uncontrolled rate freezing cryopreservation method had been reported successfully in peripheral blood hematopoietic stem cells and peripheral blood progenitor cells. Therefore, we hypothesized that uncontrolled rate freezing cooling method maybe also applied to peripheral blood mononuclear cells cryopreservation. In this study, we evaluated the performance of uncontrolled rate freezing and controlled rate freezing cooling methods through cell recovery rate, viability, differentiation potential into cytokine-induced killer cells and the cellular properties of the cultured cytokine-induced killer cells. The results showed similar post-thaw viability and recovery rate in both controlled rate freezing and uncontrolled rate freezing cryopreserved peripheral blood mononuclear cells. Importantly, the uncontrolled rate freezing cryopreserved peripheral blood mononuclear cells exhibited higher growth ratio and earlier cell clustering during ex-vivo cytokine-induced killer cell culture than the controlled rate freezing ones. These two groups of expanded cytokine-induced killer cells also exhibited similar effector cell subset ratio and tumoricidal activity. In general, the performance of cryopreserved peripheral blood mononuclear cells using uncontrolled rate freezing cooling method, with the commercial cryoprotective agent CellBanker 2, was equal or better than the controlled rate freezing method. Our study implied that the combined use of cryoprotective agent CellBanker 2 and uncontrolled rate freezing could be a convenient cryopreservation method for peripheral blood mononuclear cells.

Improved in vivo efficacy of clinical-grade cryopreserved human hepatocytes in mice with acute liver failure

Clinical hepatocyte transplantation short-term efficacy has been demonstrated; however, some major limitations, mainly due to the shortage of organs, the lack of quality of isolated cells and the low cell engraftment after transplantation, should be solved for increasing its efficacy in clinical applications. Cellular stress during isolation causes an unpredictable loss of attachment ability of the cells, which can be aggravated by cryopreservation and thawing. In this work, we focused on the use of a Good Manufacturing Practice (GMP) solution compared with the standard cryopreservation medium, the University of Wisconsin medium, for the purpose of improving the functional quality of cells and their ability to engraft in vivo, with the idea of establishing a biobank of cryopreserved human hepatocytes available for their clinical use. We evaluated not only cell viability but also specific hepatic function indicators of the functional performance of the cells such as attachment efficiency, ureogenic capability, phase I and II enzymes activities and the expression of specific adhesion molecules in vitro. Additionally, we also assessed and compared the in vivo efficacy of human hepatocytes cryopreserved in different media in an animal model of acute liver failure. Human hepatocytes cryopreserved in the new GMP solution offered better in vitro and in vivo functionality compared with those cryopreserved in the standard medium. Overall, the results indicate that the new tested GMP solution maintains better hepatic functions and, most importantly, shows better results in vivo, which could imply an increase in long-term efficacy when used in patients.

Effect of cryopreservation on the appearance and liver function of hepatocyte-like cells in cultures of cirrhotic liver of biliary atresia

Previously, we reported that non-parenchymal cell (NPC) fractions from cirrhotic liver of biliary atresia (BA) may contain stem/progenitor cells, and clusters of hepatocyte-like cells appear via hepatocyte growth factor/c-Met signaling in primary cultures of NPCs. BA is a rare and serious liver disease, and procurement of BA cells is difficult. Therefore, cryopreservation of BA liver cells is an unavoidable challenge. In this study, we examined the appearance and liver function of hepatocyte-like cells in cultures of BA liver-derived NPC fractions after cryopreservation for 1 or 6 mo using a chemically defined cryopreservation solution, STEM-CELLBANKER. Although a decrease in cell viability was observed in recovered cells after 1 mo of cryopreservation, clusters of hepatocyte-like cells appeared in the culture of cells that had been cryopreserved for 1 or 6 mo, similar to non-cryopreserved cells. In addition, these hepatocyte-like cells expressed hepatocyte-related mRNAs and demonstrated albumin production and glycogen storage. The present results suggest that hepatic stem/progenitor cells in NPC fractions may be efficiently cryopreserved, as demonstrated by the appearance of hepatocyte-like cells that show various hepatic functions even after cryopreservation. This study may lead to future BA cell therapy using the patient's own cells.

Considerations from the IQ Induction Working Group in Response to Drug-Drug Interaction Guidance from Regulatory Agencies: Focus on Downregulation, CYP2C Induction, and CYP2B6 Positive Control

The European Medicines Agency (EMA), the Pharmaceutical and Medical Devices Agency (PMDA), and the Food and Drug Administration (FDA) have issued guidelines for the conduct of drug-drug interaction studies. To examine the applicability of these regulatory recommendations specifically for induction, a group of scientists, under the auspices of the Drug Metabolism Leadership Group of the Innovation and Quality (IQ) Consortium, formed the Induction Working Group (IWG). A team of 19 scientists, from 16 of the 39 pharmaceutical companies that are members of the IQ Consortium and two Contract Research Organizations reviewed the recommendations, focusing initially on the current EMA guidelines. Questions were collated from IQ member companies as to which aspects of the guidelines require further evaluation. The EMA was then approached to provide insights into their recommendations on the following: 1) evaluation of downregulation, 2) in vitro assessment of CYP2C induction, 3) the use of CITCO as the positive control for CYP2B6 induction by CAR, 4) data interpretation (a 2-fold increase in mRNA as evidence of induction), and 5) the duration of incubation of hepatocytes with test article. The IWG conducted an anonymous survey among IQ member companies to query current practices, focusing specifically on the aforementioned key points. Responses were received from 19 companies. All data and information were blinded before being shared with the IWG. The results of the survey are presented, together with consensus recommendations on downregulation, CYP2C induction, and CYP2B6 positive control. Results and recommendations related to data interpretation and induction time course will be reported in subsequent articles.

Cell sources for in vitro human liver cell culture models

In vitro liver cell culture models are gaining increasing importance in pharmacological and toxicological research. The source of cells used is critical for the relevance and the predictive value of such models. Primary human hepatocytes (PHH) are currently considered to be the gold standard for hepatic in vitro culture models, since they directly reflect the specific metabolism and functionality of the human liver; however, the scarcity and difficult logistics of PHH have driven researchers to explore alternative cell sources, including liver cell lines and pluripotent stem cells. Liver cell lines generated from hepatomas or by genetic manipulation are widely used due to their good availability, but they are generally altered in certain metabolic functions. For the past few years, adult and pluripotent stem cells have been attracting increasing attention, due their ability to proliferate and to differentiate into hepatocyte-like cells in vitro However, controlling the differentiation of these cells is still a challenge. This review gives an overview of the major human cell sources under investigation for in vitro liver cell culture models, including primary human liver cells, liver cell lines, and stem cells. The promises and challenges of different cell types are discussed with a focus on the complex 2D and 3D culture approaches under investigation for improving liver cell functionality in vitro Finally, the specific application options of individual cell sources in pharmacological research or disease modeling are described.

Serum- and xeno-free cryopreservation of human umbilical cord tissue as mesenchymal stromal cell source

BACKGROUND AIMS

Human umbilical cord (UC) has become a notable source for mesenchymal stromal cells (MSCs) that can migrate to areas of inflammation and damaged tissue and can suppress excess immune reactions and to repair, respectively. Although UC is a solid tissue, there are several advantages, including repeatable uses from the same donor sample when needed and the possibility of future explorations for cells with unknown potential, if we could cryopreserve the UC as a living tissue material. However, because the cryoprotectants in the previous reports included animal- or allogeneic human-derived serum or no serum, the frozen-thawed UC-MSCs were inferior to fresh UC-MSCs in cell proliferation. The objective of this study was to find a suitable cryopreservation method of UC for clinical use.

METHODS

The UC was cut in cross-section and incised longitudinally, immersed in the cryoprotectant and frozen slowly. Later, it was thawed and minced rapidly, and the fragments of UC were cultured by improved explant method.

RESULTS

The highest yield of cells was obtained from frozen-thawed UC with serum- and xeno-free cryoprotectant, STEM-CELLBANKER, when compared with others. The cells derived from frozen-thawed UC stored in STEM-CELLBANKER expressed the phenotypes of MSCs, retained the immunosuppressive properties in allogeneic mixed lymphocyte reactions and the differentiation potentials (into adipocyte and chondrocytes) comparable to those derived from fresh UC.

CONCLUSIONS

UC can be cryopreserved in serum- and xeno-free cryoprotectant as a living tissue while keeping its growth and functions equivalent to fresh UC. Our method is simple and feasible for clinical use.

Biological impact of xeno-free chemically defined cryopreservation medium on amniotic epithelial cells

Background

Amnion-derived stem cells have been proposed for cell replacement therapy and tissue regeneration. An easily accessible cell source, the placenta, allows us to potentially establish a bio-bank of cells for immunotype matched clinical applications. Several xeno-free (XF) cryopreservation media are currently available for pluripotent stem cells, however, these media have not yet been evaluated for the cryopreservation of amnion-derived stem cells.

Methods

Human amniotic epithelial cells were collected using standard protocols, and stored at −160 °C in one of five commercially available media. Cells frozen in standard media containing fetal bovine serum served as controls. Cells were then thawed, and evaluated for viability, mitochondrial membrane stability, and senescence status. Quantitative real time PCR was utilized to assess for expression of stem cell genes, and flow cytometry was used to identify the stem cell surface markers.

Results

Cell recovery and repopulation assays indicated no significant difference between XF media versus standard cryopreservation medium. In addition, no impact was observed on the senescence status, the cytostructural or mitochondrial morphology between the tested cryopreservation media. Differences were observed on the expression of stem cell marker genes (OCT4, SOX2, and NANOG) and a cell surface marker (TRA1-60) following cryopreservation in different chemically defined XF media, however, these were not statistically significant.

Conclusions

Xeno-free cryopreservation of human amnion-derived stem cells is feasible and can be standardized to establish a bio-bank with human amnion-derived stem cells for future clinical application. Optimization of this media may allow for improved preservation of stem cell-like characteristics.

Acceleration of diabetic wound healing by a cryopreserved living dermal substitute created by micronized amnion seeded with fibroblasts

Bioengineered dermal substitutes have been used for the treatment of diabetic ulcers in clinics and achieved satisfactory results. However, constructing traditional tissue engineered dermal substitutes with two-step method is high-cost, time-consuming and greatly decreases fibroblast proliferative activity because of repeated trypsinization. Inthisstudy, we created a 3D micronized amniotic membrane (mAM) and used it as a natural microcarrier for ex vivo culture and amplification of human dermal fibroblasts (HDF) combined with the rotary cell culture system (RCCS). This one-step mAM-RCCS method couldamplify HDF quickly and construct a dermal substitute HDF-mAM simultaneously. To facilitate the clinical application of mAM-RCCS, anoptimized storage method was used.Post-thawing HDF-mAM retained high cell viability, intact cell morphology and active peptide secretion. When transplanted to the wounds of db/db mice, cryopreserved HDF-mAM promoted vascularization and diabetic wound healing significantly. These results demonstrate the potential application of cryopreserved HDF-mAM as a living dermal substitutefor treating diabetic ulcers and other chronic wounds in clinics.

Biotransformation in vitro: An essential consideration in the quantitative in vitro-to-in vivo extrapolation (QIVIVE) of toxicity data

Early consideration of the multiplicity of factors that govern the biological fate of foreign compounds in living systems is a necessary prerequisite for the quantitative in vitro-in vivo extrapolation (QIVIVE) of toxicity data. Substantial technological advances in in vitro methodologies have facilitated the study of in vitro metabolism and the further use of such data for in vivo prediction. However, extrapolation to in vivo with a comfortable degree of confidence, requires continuous progress in the field to address challenges such as e.g., in vitro evaluation of chemical-chemical interactions, accounting for individual variability but also analytical challenges for ensuring sensitive measurement technologies. This paper discusses the current status of in vitro metabolism studies for QIVIVE extrapolation, serving today's hazard and risk assessment needs. A short overview of the methodologies for in vitro metabolism studies is given. Furthermore, recommendations for priority research and other activities are provided to ensure further widespread uptake of in vitro metabolism methods in 21st century toxicology. The need for more streamlined and explicitly described integrated approaches to reflect the physiology and the related dynamic and kinetic processes of the human body is highlighted i.e., using in vitro data in combination with in silico approaches.

Technological progress and challenges towards cGMP manufacturing of human pluripotent stem cells based therapeutic products for allogeneic and autologous cell therapies

Recent technological advances in the generation, characterization, and bioprocessing of human pluripotent stem cells (hPSCs) have created new hope for their use as a source for production of cell-based therapeutic products. To date, a few clinical trials that have used therapeutic cells derived from hESCs have been approved by the Food and Drug Administration (FDA), but numerous new hPSC-based cell therapy products are under various stages of development in cell therapy-specialized companies and their future market is estimated to be very promising. However, the multitude of critical challenges regarding different aspects of hPSC-based therapeutic product manufacturing and their therapies have made progress for the introduction of new products and clinical applications very slow. These challenges include scientific, technological, clinical, policy, and financial aspects. The technological aspects of manufacturing hPSC-based therapeutic products for allogeneic and autologous cell therapies according to good manufacturing practice (cGMP) quality requirements is one of the most important challenging and emerging topics in the development of new hPSCs for clinical use. In this review, we describe main critical challenges and highlight a series of technological advances in all aspects of hPSC-based therapeutic product manufacturing including clinical grade cell line development, large-scale banking, upstream processing, downstream processing, and quality assessment of final cell therapeutic products that have brought hPSCs closer to clinical application and commercial cGMP manufacturing.

Human Liver Progenitor Cells for Liver Repair

Because of their high proliferative capacity, resistance to cryopreservation, and ability to differentiate into hepatocyte-like cells, stem and progenitor cells have recently emerged as attractive cell sources for liver cell therapy, a technique used as an alternative to orthotopic liver transplantation in the treatment of various hepatic ailments ranging from metabolic disorders to end-stage liver disease. Although stem and progenitor cells have been isolated from various tissues, obtaining them from the liver could be an advantage for the treatment of hepatic disorders. However, the techniques available to isolate these stem/progenitor cells are numerous and give rise to cell populations with different morphological and functional characteristics. In addition, there is currently no established consensus on the tests that need to be performed to ensure the quality and safety of these cells when used clinically. The purpose of this review is to describe the different types of liver stem/progenitor cells currently reported in the literature, discuss their suitability and limitations in terms of clinical applications, and examine how the culture and transplantation techniques can potentially be improved to achieve a better clinical outcome.