Therapeutic liver reconstitution with murine cells isolated long after death

Apoptosis in Postmortal Tissues of Goat Spinal Cords and Survival of Resident Neural Progenitors

Growing demand for therapeutic tissue repair recurrently focusses scientists' attention on critical assessment of postmortal collection of live cells, especially stem cells. Our study aimed to assess the survival of neuronal progenitors in postmortal spinal cord and their differentiation potential. Postmortal samples of spinal cords were obtained from human-sized animals (goats) at 6, 12, 24, 36, and 54 h after slaughter. Samples were studied by immunohistology, differentiation assay, Western blot and flow cytometry for the presence and location of GD2-positive neural progenitors and their susceptibility to cell death. TUNEL staining of the goat spinal cord samples over 6-54 h postmortem revealed no difference in the number of positive cells per cross-section. Many TUNEL-positive cells were located in the gray commissure around the central canal of the spinal cord; no increase in TUNEL-positive cells was recorded in either posterior or anterior horns of the gray matter where many GD2-positive neural progenitors can be found. The active caspase 3 amount as measured by Western blot at the same intervals was moderately increasing over time. Neuronal cells were enriched by magnetic separation with antibodies against CD24; among them, the GD2-positive neural progenitor subpopulation did not overlap with apoptotic cells having high pan-caspase activity. Apoptotic cell death events are relatively rare in postmortal spinal cords and are not increased in areas of the neural progenitor cell's location, within measured postmortal intervals, or among the CD24/GD2-positive cells. Data from our study suggest postmortal spinal cords as a valuable source for harvesting highly viable allogenic neural progenitor cells.

Pharmacologic inhibition of HNF4α prevents parenteral nutrition associated cholestasis in mice

Prolonged parenteral nutrition (PN) can lead to PN associated cholestasis (PNAC). Intestinally derived lipopolysaccharides and infused PN phytosterols lead to activation of NFκB, a key factor in PNAC. Our objective was to determine if inhibition of HNF4α could interfere with NFκB to alleviate murine PNAC. We showed that HNF4α antagonist BI6015 (20 mg/kg/day) in DSS-PN (oral DSS x4d followed by Total PN x14d) mice prevented the increased AST, ALT, bilirubin and bile acids and reversed mRNA suppression of hepatocyte Abcg5/8, Abcb11, FXR, SHP and MRP2 that were present during PNAC. Further, NFκB phosphorylation in hepatocytes and its binding to LRH-1 and BSEP promoters in liver, which are upregulated in DSS-PN mice, were inhibited by BI6015 treatment. BI6015 also prevented the upregulation in liver macrophages of Adgre1 (F4/80) and Itgam (CD11B) that occurs in DSS-PN mice, with concomitant induction of anti-inflammatory genes (Klf2, Klf4, Clec7a1, Retnla). In conclusion, HNF4α antagonism attenuates PNAC by suppressing NFκB activation and signaling while inducing hepatocyte FXR and LRH-1 and their downstream bile and sterol transporters. These data identify HNF4α antagonism as a potential therapeutic target for prevention and treatment of PNAC.

Pharmacologic activation of hepatic farnesoid X receptor prevents parenteral nutrition-associated cholestasis in mice

BACKGROUND AND AIMS

Parenteral nutrition (PN)-associated cholestasis (PNAC) complicates the care of patients with intestinal failure. In PNAC, phytosterol containing PN synergizes with intestinal injury and IL-1β derived from activated hepatic macrophages to suppress hepatocyte farnesoid X receptor (FXR) signaling and promote PNAC. We hypothesized that pharmacological activation of FXR would prevent PNAC in a mouse model.

APPROACH AND RESULTS

To induce PNAC, male C57BL/6 mice were subjected to intestinal injury (2% dextran sulfate sodium [DSS] for 4 days) followed by central venous catheterization and 14-day infusion of PN with or without the FXR agonist GW4064. Following sacrifice, hepatocellular injury, inflammation, and biliary and sterol transporter expression were determined. GW4064 (30 mg/kg/day) added to PN on days 4-14 prevented hepatic injury and cholestasis; reversed the suppressed mRNA expression of nuclear receptor subfamily 1, group H, member 4 (Nr1h4)/FXR, ATP-binding cassette subfamily B member 11 (Abcb11)/bile salt export pump, ATP-binding cassette subfamily C member 2 (Abcc2), ATP binding cassette subfamily B member 4(Abcb4), and ATP-binding cassette subfamily G members 5/8(Abcg5/8); and normalized serum bile acids. Chromatin immunoprecipitation of liver showed that GW4064 increased FXR binding to the Abcb11 promoter. Furthermore, GW4064 prevented DSS-PN-induced hepatic macrophage accumulation, hepatic expression of genes associated with macrophage recruitment and activation (ll-1b, C-C motif chemokine receptor 2, integrin subunit alpha M, lymphocyte antigen 6 complex locus C), and hepatic macrophage cytokine transcription in response to lipopolysaccharide in vitro. In primary mouse hepatocytes, GW4064 activated transcription of FXR canonical targets, irrespective of IL-1β exposure. Intestinal inflammation and ileal mRNAs (Nr1h4, Fgf15, and organic solute transporter alpha) were not different among groups, supporting a liver-specific effect of GW4064 in this model.

CONCLUSIONS

GW4064 prevents PNAC in mice through restoration of hepatic FXR signaling, resulting in increased expression of canalicular bile and of sterol and phospholipid transporters and suppression of macrophage recruitment and activation. These data support augmenting FXR activity as a therapeutic strategy to alleviate or prevent PNAC.

Cadaveric Stem Cells: Their Research Potential and Limitations

In the era of growing interest in stem cells, the availability of donors for transplantation has become a problem. The isolation of embryonic and fetal cells raises ethical controversies, and the number of adult donors is deficient. Stem cells isolated from deceased donors, known as cadaveric stem cells (CaSCs), may alleviate this problem. So far, it was possible to isolate from deceased donors mesenchymal stem cells (MSCs), adipose delivered stem cells (ADSCs), neural stem cells (NSCs), retinal progenitor cells (RPCs), induced pluripotent stem cells (iPSCs), and hematopoietic stem cells (HSCs). Recent studies have shown that it is possible to collect and use CaSCs from cadavers, even these with an extended postmortem interval (PMI) provided proper storage conditions (like cadaver heparinization or liquid nitrogen storage) are maintained. The presented review summarizes the latest research on CaSCs and their current therapeutic applications. It describes the developments in thanatotranscriptome and scaffolding for cadaver cells, summarizes their potential applications in regenerative medicine, and lists their limitations, such as donor’s unknown medical condition in criminal cases, limited differentiation potential, higher risk of carcinogenesis, or changing DNA quality. Finally, the review underlines the need to develop procedures determining the safe CaSCs harvesting and use.

NF-κB Regulation of LRH-1 and ABCG5/8 Potentiates Phytosterol Role in the Pathogenesis of Parenteral Nutrition-Associated Cholestasis

BACKGROUND AND AIMS

Chronically administered parenteral nutrition (PN) in patients with intestinal failure carries the risk for developing PN-associated cholestasis (PNAC). We have demonstrated that farnesoid X receptor (FXR) and liver X receptor (LXR), proinflammatory interleukin-1 beta (IL-1β), and infused phytosterols are important in murine PNAC pathogenesis. In this study we examined the role of nuclear receptor liver receptor homolog 1 (LRH-1) and phytosterols in PNAC.

APPROACH AND RESULTS

In a C57BL/6 PNAC mouse model (dextran sulfate sodium [DSS] pretreatment followed by 14 days of PN; DSS-PN), hepatic nuclear receptor subfamily 5, group A, member 2/LRH-1 mRNA, LRH-1 protein expression, and binding of LRH-1 at the Abcg5/8 and Cyp7a1 promoter was reduced. Interleukin-1 receptor-deficient mice (Il-1r^-/- /DSS-PN) were protected from PNAC and had significantly increased hepatic mRNA and protein expression of LRH-1. NF-κB activation and binding to the LRH-1 promoter were increased in DSS-PN PNAC mice and normalized in Il-1r^-/- /DSS-PN mice. Knockdown of NF-κB in IL-1β-exposed HepG2 cells increased expression of LRH-1 and ABCG5. Treatment of HepG2 cells and primary mouse hepatocytes with an LRH-1 inverse agonist, ML179, significantly reduced mRNA expression of FXR targets ATP binding cassette subfamily C member 2/multidrug resistance associated protein 2 (ABCC2/MRP2), nuclear receptor subfamily 0, groupB, member 2/small heterodimer partner (NR0B2/SHP), and ATP binding cassette subfamily B member 11/bile salt export pump (ABCB11/BSEP). Co-incubation with phytosterols further reduced expression of these genes. Similar results were obtained by suppressing the LRH-1 targets ABCG5/8 by treatment with small interfering RNA, IL-1β, or LXR antagonist GSK2033. Liquid chromatography-mass spectrometry and chromatin immunoprecipitation experiments in HepG2 cells showed that ATP binding cassette subfamily G member 5/8 (ABCG5/8) suppression by GSK2033 increased the accumulation of phytosterols and reduced binding of FXR to the SHP promoter. Finally, treatment with LRH-1 agonist, dilauroyl phosphatidylcholine (DLPC) protected DSS-PN mice from PNAC.

CONCLUSIONS

This study suggests that NF-κB regulation of LRH-1 and downstream genes may affect phytosterol-mediated antagonism of FXR signaling in the pathogenesis of PNAC. LRH-1 could be a potential therapeutic target for PNAC.

Bovine Satellite Cells Isolated after 2 and 5 Days of Tissue Storage Maintain the Proliferative and Myogenic Capacity Needed for Cultured Meat Production

Cultured meat is an emerging alternative food technology which aims to deliver a more ethical, sustainable, and healthy muscle-tissue-derived food item compared to conventional meat. As start-up companies are rapidly forming and accelerating this technology, many aspects of this multi-faceted science have still not been investigated in academia. In this study, we investigated if bovine satellite cells with the ability to proliferate and undergo myogenic differentiation could be isolated after extended tissue storage, for the purpose of increasing the practicality for cultured meat production. Proliferation of bovine satellite cells isolated on the day of arrival or after 2 and 5 days of tissue storage were analyzed by metabolic and DNA-based assays, while their myogenic characteristics were investigated using RT-qPCR and immunofluorescence. Extended tissue storage up to 5 days did not negatively affect proliferation nor the ability to undergo fusion and create myosin heavy chain-positive myotubes. The expression patterns of myogenic and muscle-specific genes were also not affected after tissue storage. In fact, the data indicated a positive trend in terms of myogenic potential after tissue storage, although it was non-significant. These results suggest that the timeframe of which viable myogenic satellite cells can be isolated and used for cultured meat production can be greatly extended by proper tissue storage.

Tissues from Post-Mortem Donors as Alternative Sources of Stem Cells for Regenerative Medicine

Stem cells provide for all of the tissues in our body during embryogenesis. In adult organisms, they can be found as rare populations of tissue-specific stem cells in quiescent states, although they can still regenerate damaged tissues. Astonishingly, these cells are retained in tissues even post-mortem. There have been several reports that have provided evidence that cells with stem-like capabilities can be isolated, expanded, and differentiated in vitro from various tissues several hours, or even several days, post-mortem. Moreover, some post-mortem-tissue-derived stem cells can successfully engraft and regenerate injured host tissues. Here, we review in-vitro and in-vivo studies that provide evidence of isolation and characterization of stem cells from different tissues post-mortem, with a focus on the musculoskeletal and neural systems. Finally, we discuss their potential for use in regenerative medicine, and what needs to be done in further research toward their better exploitation.

Adult Mouse Liver Contains Two Distinct Populations of Cholangiocytes

The biliary system plays an important role in several acquired and genetic disorders of the liver. We have previously shown that biliary duct epithelium contains cells giving rise to proliferative Lgr5⁺ organoids in vitro. However, it remained unknown whether all biliary cells or only a specific subset had this clonogenic activity. The cell surface protease ST14 was identified as a positive marker for the clonogenic subset of cholangiocytes and was used to separate clonogenic and non-clonogenic duct cells by fluorescence-activated cell sorting. Only ST14^hi duct cells had the ability to generate organoids that could be serially passaged. The gene expression profiles of clonogenic and non-clonogenic duct cells were similar, but several hundred genes were differentially expressed. RNA fluorescence in situ hybridization showed that clonogenic duct cells are interspersed among regular biliary epithelium at a ∼1:3 ratio. We conclude that adult murine cholangiocytes can be subdivided into two populations differing in their proliferative capacity.

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Adult cholangiocytes consist of two distinct subsets

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ST14 is heterogeneously expressed in adult biliary epithelium

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ST14^hi cells are the clonogenic duct subset interspersed in normal bile ducts

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Gene expression differs between ST14^hi and ST14^lo duct cells

Cadaveric cardiosphere-derived cells can maintain regenerative capacity and improve the heart function of cardiomyopathy

OBJECTIVE

Cardiosphere-derived cells (CDCs) improve cardiac function and attenuate remodeling in ischemic and non-ischemic cardiomyopathy, and are currently obtained through myocardial biopsy. However, there is not any study on whether functional CDCs may be obtained through cadaveric autopsy with similar benefits in non-ischemic cardiomyopathy.

METHODS

Cardiac tissues from human or mouse cadavers were harvested, plated at 4°C, and removed at varying time points to culture human CDCs (CLH-EDCs) and mouse CDCs (CM-CDCs). The differentiation and paracrine effects of CDCs were also assessed. Furthermore, intramyocardial injection of cadaveric CM-CDCs was performed in an induced dilated cardiomyopathy (DCM) model.

RESULTS

With the extension of post mortem hours, the number of CLH-EDCs and CM-CDCs harvested from autopsy specimens decreased. The expressions of von Willebrand factor (VWF) and smooth muscle actin (SMA) on CDCs were gradually reduced, however, cardiac troponin I (TNI) expression increased in the 24 h group compared to the 0 h group. CLH-EDCs were also found to have similar paracrine function in the 24 h group compared to 0 h group. 8 weeks after CM-CDCs transplantion to the injured heart, mean left ventricular ejection fraction increased in both 0 h (64.99 ± 3.4%) and 24 h (62.99 ± 2.8%) CM-CDCs-treated groups as compared to the PBS treated group (53.64 ± 5.6 cm), with a decrease in left ventricular internal diastolic diameter (0.29 ± 0.08 cm and 0.32 ± 0.04 cm in 0 h and 24 h groups, vs. 0.41 ± 0.05 cm in PBS group).

CONCLUSION

CDCs from cadaveric autopsy are highly proliferative and differentiative, and may be used as a source for allograft transplantation, in order to decrease myocardial fibrosis, attenuate left ventricular remodeling, and improve heart function in doxorubicin-induced non-ischemic cardiomyopathy.

Hepatic progenitor cells of biliary origin with liver repopulation capacity

Hepatocytes and cholangiocytes self-renew following liver injury. Following severe injury hepatocytes are increasingly senescent, but whether hepatic progenitor cells (HPCs) then contribute to liver regeneration is unclear. Here, we describe a mouse model where the E3 ubiquitin ligase Mdm2 is inducibly deleted in more than 98% of hepatocytes, causing apoptosis, necrosis and senescence with nearly all hepatocytes expressing p21. This results in florid HPC activation, which is necessary for survival, followed by complete, functional liver reconstitution. HPCs isolated from genetically normal mice, using cell surface markers, were highly expandable and phenotypically stable in vitro. These HPCs were transplanted into adult mouse livers where hepatocyte Mdm2 was repeatedly deleted, creating a non-competitive repopulation assay. Transplanted HPCs contributed significantly to restoration of liver parenchyma, regenerating hepatocytes and biliary epithelia, highlighting their in vivo lineage potency. HPCs are therefore a potential future alternative to hepatocyte or liver transplantation for liver disease.

Hepatic Stellate Cells Improve Engraftment of Human Primary Hepatocytes: A Preclinical Transplantation Study in an Animal Model

Human hepatocytes are used for liver cell therapy, but the small number of engrafting cells limits the benefit of cell transplantation. We tested whether cotransplantation of hepatocytes with hepatic stellate cells (HSCs) could improve hepatocyte engraftment in vivo. Human primary hepatocytes were transplanted into SCID mice either alone or in a mixture with HSCs (quiescent or after culture activation) or LX-2 cells (ratio 20:1). Four weeks after transplantation into mouse livers, human albumin-positive (huAlb(+)) hepatocytes were found scattered. When cotransplanted in a mixture with HSCs or LX-2 cells, huAlb(+) hepatocytes formed clusters and were more numerous occupying 2- to 5.9-fold more surface on the tissue section than in livers transplanted with hepatocytes alone. Increased huAlb mRNA expression in livers transplanted with the cell mixtures confirmed those results. The presence of HSCs increased the number of hepatocytes entrapped in the host liver at an early time point posttransplantation but not their proliferation in situ as assessed by cumulative incorporation of BrdU. Importantly, 4 weeks posttransplantation, we found no accumulation of αSMA(+)-activated HSCs or collagen deposition. To follow the fate of transplanted HSCs, HSCs derived from GFP(+) mice were injected into GFP(-) littermates: 17 h posttransplant, GFP(+) HSCs were found in the sinusoids, without proliferating or actively producing ECM; they were undetectable at later time points. Coculture with HSCs improved the number of adherent hepatocytes, with best attachment obtained when hepatocytes were seeded in contact with activated HSCs. In vivo, cotransplantation of hepatocytes with HSCs into a healthy liver recipient does not generate fibrosis, but significantly improves the engraftment of hepatocytes, probably by ameliorating cell homing.

Dormancy and quiescence of skeletal muscle stem cells

The skeletal muscle of vertebrates has a huge regenerative capacity. When destroyed after different types of injury, this organ can regenerate very quickly (less than 20 days following myotoxin injection in the mouse) ad integrum and repeatedly. The cell responsible for this regeneration is the so-called satellite cell, the muscle stem cell that lies on top of the muscle fibre, a giant, multinucleated cell that contains the contractile material. When injected in the muscle, satellite cells can efficiently differentiate into contractile muscle fibres. The satellite cell shows great therapeutic potential; and its regenerative capacity has triggered particular interest in the field of muscular degeneration. In this review we will focus on one particular property of the satellite cell: its quiescence and dormancy. Indeed adult satellite cells are quiescent; they lie between the basal lamina and the basement membrane of the muscle fibre, ready to proliferate, and fuse in order to regenerate myofibers upon injury. It has recently been shown that a subpopulation of satellite cells is able to enter dormancy in human and mice cadavers. Dormancy is defined by a low metabolic state, low mobility, and a long lag before division when plated in vitro, compared to quiescent cells. This definition is also based on current knowledge about long-term hematopoietic stem cells, a subpopulation of stem cells that are described as dormant based on the same criteria (rare division and low metabolism when compared to progeny which are dividing more often). In the first part of this review, we will provide a description of satellite cells which addresses their quiescent state. We will then focus on the uneven distribution of satellite cells in the muscle and describe evidence that suggests that their dormancy differs from one muscle to the next and that one should be cautious when making generalisations regarding this cellular state. In a second part, we will discuss the transition between active dividing cells in developing animals to quiescence. This mechanism could be used or amplified in the switch from quiescence to dormancy. In a third part, we will review the signals and dynamics that actively maintain the satellite cell quiescent. The in-depth understanding of these mechanisms is key to describing how dormancy relies on quiescent state of the cells. In a fourth part, we will deal with dormancy per se: how dormant satellite cells can be obtained, their characteristics, their metabolic profile, and their molecular signature as compared to quiescent cells. Here, we will highlight one of the most important recent findings: that quiescence is a prerequisite for the entry of the satellite cell into dormancy. Since dormancy is a newly discovered phenomenon, we will review the mechanisms responsible for quiescence and activation, as these two cellular states are better known and key to understanding satellite cell dormancy. This will allow us to describe dormancy and its prerequisites.

Recovery of fibroblast-like cells from refrigerated goat skin up to 41 d of animal death

Successful cloning of animals using somatic cell nuclear transfer requires undamaged nuclear DNA from desired donor cell types. In vitro culture of cells is one way of ensuring nuclear integrity. The goal of this study was to evaluate the limits of postmortem cell survival/culture in refrigerated goat ear skin tissues which could be used for long-term storage and cloning of animals in future. To achieve this, 60 explants from 6 different goats were cultured after 0, 3, 6, 9, 13, 16, 20, 23, 27, 30, 33, 37, and 41 d postmortem and observed under inverted microscope for outgrowth of fibroblast-like cells, after 10-12 d of culture. Explants from all time points including 19% from 41-dpm tissues exhibited outgrowth. However, the percentage of outgrowth positive explants, as well as culture confluence, reduced with increasing postmortem time interval. Cell cultures established from primary outgrowth of 41-dpm tissues when compared for their growth profile with similarly obtained 0-dpm cultures revealed similar growth curve and cell morphology. Cytogenetic analysis of 41-dpm tissue-derived cell populations revealed a normal female karyotype with 60 XX homologous chromosomes indicating genetic stability of the cell population. In conclusion, these results show that refrigerated skin tissue remains alive for more than a month and that the cells derived from such tissues are normal and can be cryopreserved for long-term storage and future cloning of animals with desired genetics.

Long live the stem cell: the use of stem cells isolated from post mortem tissues for translational strategies

The "stem cell" has become arguably one of the most important biological tools in the arsenal of translational research directed at regeneration and repair. It remains to be seen whether every tissue has its own stem cell niche, although relatively recently a large amount of research has focused on isolating and characterizing tissue-specific stem cell populations, as well as those that are able to be directed to transdifferentiate into a variety of different lineages. Traditionally, stem cells are isolated from the viable tissue of embryonic, fetal, or adult living hosts; from "fresh" donated tissues that have been surgically or otherwise removed (biopsies), or obtained directly from tissues within minutes to several hours post mortem (PM). These human progenitor/stem cell sources remain potentially highly controversial, since they are accompanied by various still-unresolved ethical, social, moral and legal challenges. Due to the limited number of "live" donors, the small amount of material obtained from biopsies and difficulties during purification processes, harvesting from cadaveric material presents itself as an alternative strategy that could provide a hitherto untapped source of stem cells. However, PM stem cells are not without their own unique set of limitations including difficulty of obtaining samples, limited supply of material, variations in delay between death and sample collection, possible lack of medication history and suboptimal retrospective assignment of diagnostic and demographic data. This article is part of a Directed Issue entitled: Regenerative Medicine: The challenge of translation.

Cellular extracts from post-mortem human cardiac tissue direct cardiomyogenic differentiation of human adipose tissue-derived stem cells

BACKGROUND AIMS

Human adipose tissue-derived stem cells (hASCs) can be easily (and inexpensively) expanded in culture, and their high plasticity allows their conversion to different cell types. We study the potential capacity of postmortem cardiac tissue to direct cardiac differentiation of hASCs in vitro.

METHODS

Cardiac tissue collected from autopsies was used to obtain cell extracts and conditioned medium, and both approaches were tested for cardiac induction.

RESULTS

Gene expression analyses proved that post-mortem human cardiac tissue maintains genetic integrity. hASCs exposed to the cell extracts or conditioned medium for 2 weeks achieved the appearance of myotube-like structures and were positive for cardiac markers such as sarcomeric α-actinin, cardiac troponin I and T and desmin as proved by immunofluorescence. In addition, differentiated cells showed increased expression of cardiomyocyte-related genes analyzed by reverse transcriptase polymerase chain reaction (GATA-4, myocyte-enhancer factor-2c, α-cardiac actin and cardiac troponin I).

CONCLUSIONS

For the first time, post-mortem human cardiac tissue was used to induce hASC differentiation into myocardial-like cells. The methodology described here would serve as a useful model to obtain cardiomyocyte-like cells in vitro.

Liver support strategies: cutting-edge technologies

The treatment of end-stage liver disease and acute liver failure remains a clinically relevant issue. Although orthotopic liver transplantation is a well-established procedure, whole-organ transplantation is invasive and increasingly limited by the unavailability of suitable donor organs. Artificial and bioartificial liver support systems have been developed to provide an alternative to whole organ transplantation, but despite three decades of scientific efforts, the results are still not convincing with respect to clinical outcome. In this Review, conceptual limitations of clinically available liver support therapy systems are discussed. Furthermore, alternative concepts, such as hepatocyte transplantation, and cutting-edge developments in the field of liver support strategies, including the repopulation of decellularized organs and the biofabrication of entirely new organs by printing techniques or induced organogenesis are analysed with respect to clinical relevance. Whereas hepatocyte transplantation shows promising clinical results, at least for the temporary treatment of inborn metabolic diseases, so far data regarding implantation of engineered hepatic tissue have only emerged from preclinical experiments. However, the evolving techniques presented here raise hope for bioengineered liver support therapies in the future.

Therapeutic hepatocyte transplant for inherited metabolic disorders: functional considerations, recent outcomes and future prospects

The applications, outcomes and future strategies of hepatocyte transplantation (HTx) as a corrective intervention for inherited metabolic disease (IMD) are described. An overview of HTx in IMDs, as well as preclinical evaluations in rodent and other mammalian models, is summarized. Current treatments for IMDs are highlighted, along with short- and long-term outcomes and the potential for HTx to supplement or supplant these treatments. Finally, the advantages and disadvantages of HTx are presented, highlighted by long-term challenges with interorgan engraftment and expansion of transplanted cells, in addition to the future prospects of stem cell transplants. At present, the utility of HTx is represented by the potential to bridge patients with life-threatening liver disease to organ transplantation, especially as an adjuvant intervention where severe organ shortages continue to pose challenges.

Intestinal stem cells remain viable after prolonged tissue storage

Intestinal stem cells (ISCs) are responsible for renewal of the epithelium both during normal homeostasis and following injury. As such, they have significant therapeutic potential. However, whether ISCs can survive tissue storage is unknown. We hypothesize that, although the majority of epithelial cells might die, ISCs would remain viable for at least 24 h at 4 °C. To explore this hypothesis, jejuna of C57Bl6/J or Lgr5-LacZ mice were removed and either processed immediately or placed in phosphate-buffered saline at 4 °C. Delayed isolation of epithelium was performed after 24, 30, or 48 h storage. At the light microscope level, despite extensive apoptosis of villus epithelial cells, small intestinal crypts remained morphologically intact for 30 h and ISCs were identifiable via Lgr5-LacZ positivity. Electron microscopy showed that ISCs retained high integrity for 24 h. When assessed by flow cytometry, ISCs were more resistant to degeneration than the rest of the epithelium, including neighboring Paneth cells, with higher viability across all time points. Cultured isolated crypts showed no loss of capacity to form complex enteroids after 24 h tissue storage, with efficiencies after 7 days of culture remaining above 80 %. By 30 h storage, efficiencies declined but budding capability was retained. We conclude that, with delay in isolation, ISCs remain viable and retain their proliferative capacity. In contrast, the remainder of the epithelium, including the Paneth cells, exhibits degeneration and programmed cell death. If these findings are recapitulated in human tissue, storage at 4 °C might offer a valuable temporal window for the harvesting of crypts or ISCs for therapeutic application.

Effect of postmortem time interval on in vitro culture potential of goat skin tissues stored at room temperature

Animal cloning using somatic cell nuclear transfer technology has renewed the interest in postmortem tissue storage, since these tissues can be used to reintroduce the lost genes back into the breeding pool in animal agriculture, preserve the genetic diversity, and revive the endangered species. However, for successful cloning of animals, integrity of nuclear DNA is essential. Cell viability and their potential to in vitro culture ensure nuclear integrity. The aim of this study was to determine the limits of postmortem time interval within which live cells can be recovered from goat skin tissues. To test the postmortem tissue storage limits, we cultured 2-3 mm(2) skin pieces (n = 70) from the ears of three breeds of goats (n = 7) after 0, 2, 4, and 6 days of postmortem storage at 24°C. After 10 days of culture, outgrowth of fibroblast-like cells (>50 cells) around the explants was scored. All the explants irrespective of breed displayed outgrowth of cells on the dish containing fresh tissues (i.e., day 0 of storage). However, the number of explants exhibiting outgrowth reduced with increasing time interval. Only 53.85 % explants displayed outgrowth after 2 days of tissue storage. The number of explants displaying outgrowth was much smaller after 4 (16.67 %) and 6 days (13.3 %) of storage. In general, the number of outgrowing cells per explant, on a given day, also decreased with increasing postmortem storage time interval. To test the differences between cell cultures, we established secondary cultures from one of the goats exhibiting outgrowth of cells after 6 days of tissue storage and compared them to similar cells from fresh tissues. Comparison of both the cell lines revealed similar cell morphology and growth curves and had doubling times of 23.04 and 22.56 h, respectively. These results suggest that live cells can be recovered from goat (and perhaps other animal) tissues stored at room temperature even after 6 days of their death with comparable growth profiles and, thus, can be used for tissue banking for preservation of superior genetics, genetic diversity, and cloning of animals.

Molecular perturbations restrict potential for liver repopulation of hepatocytes isolated from non-heart-beating donor rats

Organs from non-heart-beating donors are attractive for use in cell therapy. Understanding the nature of molecular perturbations following reperfusion/reoxygenation will be highly significant for non-heart-beating donor cells. We studied non-heart-beating donor rats for global gene expression with Affymetrix microarrays, hepatic tissue integrity, viability of isolated hepatocytes, and engraftment and proliferation of transplanted cells in dipeptidyl peptidase IV-deficient rats. In non-heart-beating donors, liver tissue was morphologically intact for >24 hours with differential expression of 1, 95, or 372 genes, 4, 16, or 34 hours after death, respectively, compared with heart-beating donors. These differentially expressed genes constituted prominent groupings in ontological pathways of oxidative phosphorylation, adherence junctions, glycolysis/gluconeogenesis, and other discrete pathways. We successfully isolated viable hepatocytes from non-heart-beating donors, especially up to 4 hours after death, although the hepatocyte yield and viability were inferior to those of hepatocytes from heart-beating donors (P < 0.05). Similarly, although hepatocytes from non-heart-beating donors engrafted and proliferated after transplantation in recipient animals, this was inferior to hepatocytes from heart-beating donors (P < 0.05). Gene expression profiling in hepatocytes isolated from non-heart-beating donors showed far greater perturbations compared with corresponding liver tissue, including representation of pathways in focal adhesion, actin cytoskeleton, extracellular matrix-receptor interactions, multiple ligand-receptor interactions, and signaling in insulin, calcium, wnt, Jak-Stat, or other cascades.

CONCLUSION

Liver tissue remained intact over prolonged periods after death in non-heart-beating donors, but extensive molecular perturbations following reperfusion/reoxygenation impaired the viability of isolated hepatocytes from these donors. Insights into molecular changes in hepatocytes from non-heart-beating donors offer opportunities for improving donor cell viability, which will advance the utility of non-heart-beating donor organs for cell therapy or other applications.

Management of Liver Failure: From Transplantation to Cell-Based Therapy

The severe shortage of deceased donor organs has driven a search for alternative methods of treating liver failure. In this context, cell-based regenerative medicine is emerging as a promising interdisciplinary field of tissue repair and restoration, able to contribute to improving health in a minimally invasive fashion. Several cell types have allowed long-term survival in experimental models of liver injury, but their therapeutic potential in humans should be regarded with deep caution, because few clinical trials are currently available and the number of patients enrolled so far is too small to assess benefits versus risks. This review summarizes the current literature on the physiological role of endogenous stem cells in liver regeneration and on the therapeutic benefits of exogenous stem cell administration with specific emphasis on the potential clinical uses of mesenchymal stem cells. Moreover, critical points that still need clarification, such as the exact identity of the stem-like cell population exerting the beneficial effects, as well as the limitations of stem cell-based therapies, are discussed.

In vitro culture of fibroblast-like cells from postmortem skin of Katahdin sheep stored at 4 °C for different time intervals

Live animals have been produced recently from animal tissues preserved for decades at frozen temperatures with or without cryoprotectants. However, the tissues in these studies were cryopreserved within few hours of animal death to obtain culturable live cells as nuclear donors. How long the tissues can be left unfrozen after animal death, without losing the viability and potential to in vitro culture with comparable morphology and proliferative rate as the fresh tissues, is not completely understood. To understand this phenomenon, ear skin samples from individual sheep (n=3) were procured from slaughter plant and stored at 4 °C. After various intervals (2, 8, 24, 32, 48, and 56 h after slaughter), 2-3 mm(2) pieces (n=10) of skin samples were cultured for 12 d on two dishes (60 mm) for each sheep. Outgrowth of fibroblast-like cells was observed as early as day 4 of culture and was visible on dishes of all time points including 56 h by day 10. The number of outgrowing cells decreased with increasing time interval between animal slaughter and culture initiation. Secondary cultures were successfully established for all the time points. All cultures proliferated well and were apparently normal. Passage 2 cultures of 2 h and 56 h interval for one of the three sheep were compared for their growth pattern and proliferation rates. The population doubling time of 2 h and 56 h intervals was 33.12 and 34.8 h, respectively, and both the lines exhibited similar cell morphology and an "S"-shaped growth curve. These results suggest that skin tissues of sheep and perhaps other animal species with superior traits are effectively preserved at cellular level at least for 56 h at normal refrigerating conditions, without need of complicated cryopreservatives/cryotanks that are usually not available at small farms.