Repair of liver mediated by adult mouse liver neuro-glia antigen 2-positive progenitor cell transplantation in a mouse model of cirrhosis

Single-cell landscape of the intrahepatic ecosystem in alcohol-related liver disease

Alcohol-related liver disease (ALD) is a common chronic liver disease caused by long-term excessive alcohol consumption and responsible for more than half of all liver-related deaths worldwide. The molecular mechanisms associated with ALD were not fully understood. In this study, we performed single-cell RNA sequencing on liver tissues obtained from ALD patients and healthy liver donors. We identified an ALB+KRT7+ epithelial population that expressed both hepatocyte and biliary markers significantly expanded in ALD livers. The ALB+KRT7+ epithelial cells were demonstrated to have stem cell properties and malignant transformation potentials. Moreover, ALB+KRT7+ epithelium-derived ALD organoids promote the tumour growth by activating Wnt/β-catenin signalling of liver cancer cells. Most importantly, blocking the Wnt protein secretion or knockdown the Wnt receptor suppressed the tumour promoting effect of ALD organoids. Our study provides important insights that Wnt signalling can be targeted in patients with advanced alcohol-related cirrhosis to prevent malignant transformation. In addition, our results also uncovered the important alterations of nonparenchymal cells, especially macrophages and T/NK populations that responsible for active inflammation responses in alcohol-related hepatitis and immunosuppressive microenvironment in advanced cirrhosis livers, which likely facilitated the malignant progression of ALD. KEY POINTS: This study provides single-cell landscape of human liver samples across different ALD stages. The ALB+ KRT7+ epithelium were enriched in ALD patients, and the function of this epithelial population varied significantly across ALD stages. ALB+KRT7+ epithelium from advanced alcohol-related cirrhosis had malignant transformation potential and tumour promotion activity. The comprehensive changes of parenchymal and nonparenchymal cells in the ALD livers lay a hidden danger for the further malignant progression.

New advances of NG2-expressing cell subset in marrow mesenchymal stem cells as novel therapeutic tools for liver fibrosis/cirrhosis

BACKGROUND

Bone marrow-derived mesenchymal stem cell (BMMSC)-based therapy has become a major focus for treating liver fibrosis/cirrhosis. However, although these cell therapies promote the treatment of this disease, the heterogeneity of BMMSCs, which causes insufficient efficacy during clinical trials, has not been addressed. In this study, we describe a novel Percoll-Plate-Wait procedure (PPWP) for the isolation of an active cell subset from BMMSC cultures that was characterized by the expression of neuroglial antigen 2 (NG2/BMMSCs).

METHODS

By using the key method of PPWP and other classical biological techniques we compared NG2/BMMSCs with parental BMMSCs in biological and functional characteristics within a well-defined diethylnitrosamine (DEN)-induced liver fibrosis/cirrhosis injury male C57BL/6 mouse model also in a culture system. Of note, the pathological alterations in the model is quite similar to humans'.

RESULTS

The NG2/BMMSCs revealed more advantages compared to parentalBMMSCs. They exhibited greater proliferation potential than parental BMMSCs, as indicated by Ki-67 immunofluorescence (IF) staining. Moreover, higher expression of SSEA-3 (a marker specific for embryonic stem cells) was detected in NG2/BMMSCs than in parental BMMSCs, which suggested that the "stemness" of NG2/BMMSCs was greater than that of parental BMMSCs. In vivo studies revealed that an injection of NG2/BMMSCs into mice with ongoing DEN-induced liver fibrotic/cirrhotic injury enhanced repair and functional recovery to a greater extent than in mice treated with parental BMMSCs. These effects were associated with the ability of NG2/BMMSCs to differentiate into bile duct cells (BDCs). In particular, we discovered for the first time that NG2/BMMSCs exhibit unique characteristics that differ from those of parental BMMSCs in terms of producing liver sinusoidal endothelial cells (LSECs) to reconstruct injured blood vessels and sinusoidal structures in the diseased livers, which are important for initiating hepatocyte regeneration. This unique potential may also suggest that NG2/BMMSCs could be an novel off-liver progenitor of LSECs. Ex vivo studies revealed that the NG2/BMMSCs exhibited a similar trend to that of their in vivo in terms of functional differentiation responding to the DEN-diseased injured liver cues. Additionally, the obvious core role of NG2/BMMSCs in supporting the functions of BMMSCs in bile duct repair and BDC-mediated hepatocyte regeneration might also be a novel finding.

CONCLUSIONS

Overall, the PPWP-isolated NG2/BMMSCs could be a novel effective cell subset with increased purity to serve as a new therapeutic tool for enhancing treatment efficacy of BMMSCs and special seed cell source (BDCs, LSECs) also for bioliver engineering.

Hepatocyte growth factor-mediated apoptosis mechanisms of cytotoxic CD8+ T cells in normal and cirrhotic livers

Intrahepatic stem/progenitor cells and cytotoxic CD8⁺ T cells (CD8⁺ T cells) in the cirrhotic liver undergo apoptosis, which potentially facilitates progression to cancer. Here, we report that hepatocyte growth factor (HGF) signaling plays an important role in promoting normal and damaged liver CD8⁺ T cell Fas-mediated apoptosis through its only receptor, c-Met. In addition to binding with HGF, c-Met also binds to Fas to form a complex. Using a diethylnitrosamine (DEN)-induced liver fibrosis/cirrhosis mouse model, immunostaining, and terminal deoxynucleotidyl transferase (TdT) dUTP nick-end labeling (TUNEL) staining, we found that HGF secretion was significantly higher at 10 weeks post-DEN, the liver cirrhotic phase (LCP), than at 3 weeks post-DEN, the liver fibrotic phase (LFP). Correspondingly, differences in CD8⁺ T cell proliferation and apoptosis were noted between the two phases. Interestingly, staining and TUNEL assays revealed lower smooth muscle actin (α-SMA)⁺ cell apoptosis, a marker for hepatic stellate cells (HSCs), in the LFP group than in the LCP group, which suggested a beneficial correlation among HGF, CD8⁺ T cells and HSCs in improving the fibrotic load during damaged liver repair. In cultures, when met different concentrations of recombinant HGF (rHGF), phytohemagglutinin (PHA)-stimulated naive mouse splenic CD8⁺ T cells (pn-msCD8⁺ T cells) responded differently; as increases in rHGF increased were associated with decreases in the clonal numbers of pn-msCD8⁺ T cells, and when the rHGF dose was greater than 200 ng/mL, the clonal numbers significantly decreased. In the presence of 400 ng/mL rHGF, the death-inducing signaling complex (DISC) can be directly activated in both nsCD8⁺ T cells and healthy human peripheral blood CD8⁺ T cells (hp-CD8⁺ T cells), as indicated by recruitment of FADD and caspase-8 because DISC forms via the recruitment of FADD and caspase-8, among others. These findings suggest that Fas-mediated apoptosis, may also indicate a regulatory role of HGF signaling in hepatic homeostasis.

Macrophage Depletion Reactivates Fecal Virus Shedding following Resolution of Acute Hepatitis A in Ifnar1-/- Mice

Although hepatitis A virus (HAV) is associated only with acute hepatitis in humans, HAV RNA persists within the liver for months following resolution of liver inflammation and cessation of fecal virus shedding in chimpanzees and murine models of hepatitis A. Here, we confirm striking differences in the kinetics of HAV RNA clearance from liver versus serum and feces in infected Ifnar1-/- mice and investigate the nature of viral RNA persisting in the liver following normalization of serum alanine aminotransferase (ALT) levels. Fecal shedding of virus produced in hepatocytes declined >3,000-fold between its peak at day 14 and day 126, whereas intrahepatic HAV RNA declined only 32-fold by day 154. Viral RNA was identified within hepatocytes 3 to 4 months after inoculation and was associated with membranes, banding between 1.07 and 1.14 g/cm3 in isopycnic iodixanol gradients. Gradient fractions containing HAV RNA demonstrated no infectivity when inoculated into naive mice but contained neutralizing anti-HAV antibody. Depleting CD4+ or CD8+ T cells at this late point in infection had no effect on viral RNA abundance in the liver, whereas clodronate-liposome depletion of macrophages between days 110 and 120 postinoculation resulted in a striking recrudescence of fecal virus shedding and the reappearance of viral RNA in serum coupled with reductions in intra-hepatic Ifnγ, Tnfα, Ccl5, and other chemokine transcripts. Our data suggest that replication-competent HAV RNA persists for months within the liver in the presence of neutralizing antibody following resolution of acute hepatitis in Ifnar1-/- mice and that macrophages play a key role in viral control late in infection. IMPORTANCE HAV RNA persists in the liver of infected chimpanzees and interferon receptor-deficient Ifnar1-/- mice for many months after neutralizing antibodies appear, virus has been cleared from the blood, and fecal virus shedding has terminated. Here, we show this viral RNA is located within hepatocytes and that the depletion of macrophages months after the resolution of hepatic inflammation restores fecal virus shedding and circulating viral RNA. Our study identifies an important role for macrophages in virus control following resolution of acute hepatitis A in Ifnar1-/- mice and may have relevance to relapsing hepatitis A in humans.

Immunotherapeutic Targeting of NG2/CSPG4 in Solid Organ Cancers

Neuro-glia antigen 2/chondroitin sulfate proteoglycan 4 (NG2/CSPG4, also called MCSP, HMW-MAA, MSK16, MCSPG, MEL-CSPG, or gp240) is a large cell-surface antigen and an unusual cell membrane integral glycoprotein frequently expressed on undifferentiated precursor cells in multiple solid organ cancers, including cancers of the liver, pancreas, lungs, and kidneys. It is a valuable molecule involved in cancer cell adhesion, invasion, spreading, angiogenesis, complement inhibition, and signaling. Although the biological significance underlying NG2/CSPG4 proteoglycan involvement in cancer progression needs to be better defined, based on the current evidence, NG2/CSPG4⁺ cells, such as pericytes (PCs, NG2⁺/CD146⁺/PDGFR-β⁺) and cancer stem cells (CSCs), are closely associated with the liver malignancy, hepatocellular carcinoma (HCC), pancreatic malignancy, and pancreatic ductal adenocarcinoma (PDAC) as well as poor prognoses. Importantly, with a unique method, we successfully purified NG2/CSPG4-expressing cells from human HCC and PDAC vasculature tissue blocks (by core needle biopsy). The cells appeared to be spheres that stably expanded in cultures. As such, these cells have the potential to be used as sources of target antigens. Herein, we provide new information on the possibilities of frequently selecting NG2/CSPG4 as a solid organ cancer biomarker or exploiting expressing cells such as CSCs, or the PG/chondroitin sulfate chain of NG2/CSPG4 on the cell membrane as specific antigens for the development of antibody- and vaccine-based immunotherapeutic approaches to treat these cancers.

Neonatal lung-derived SSEA-1+ cells exhibited distinct stem/progenitor characteristics and organoid developmental potential

Stem/progenitor cells, because of their self-renewal and multiple cell type differentiation abilities, have good potential in regenerative medicine. We previously reported a lung epithelial cell population that expressed the stem cell marker SSEA-1 was abundant in neonatal but scarce in adult mice. In the current study, neonatal and adult mouse-derived pulmonary SSEA-1⁺ cells were isolated for further characterization. The results showed that neonatal-derived pulmonary SSEA-1⁺ cells highly expressed lung development-associated genes and had enhanced organoid generation ability compared with the adult cells. Neonatal pulmonary SSEA-1⁺ cells generated airway-like and alveolar-like organoids, suggesting multilineage cell differentiation ability. Organoid generation of neonatal but not adult pulmonary SSEA-1⁺ cells was enhanced by fibroblast growth factor 7 (FGF 7). Furthermore, neonatal pulmonary SSEA-1⁺ cells colonized and developed in decellularized and injured lungs. These results suggest the potential of lung-derived neonatal-stage SSEA-1⁺ cells with enhanced stem/progenitor activity and shed light on future lung engineering applications.

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Pulmonary SSEA-1⁺ cells are abundant in neonatal and scarce in adult stages

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The stem/progenitor activity of pulmonary SSEA-1⁺ cells is enhanced in neonatal stage

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Neonatal pulmonary SSEA-1⁺ cells developed into airway- and alveolar-like organoids

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FGF7 regulates alveolar epithelium development of neonatal pulmonary SSEA-1⁺ cells

Liver Regeneration and Cell Transplantation for End-Stage Liver Disease

Liver transplantation is the only curative option for end-stage liver disease; however, the limitations of liver transplantation require further research into other alternatives. Considering that liver regeneration is prevalent in liver injury settings, regenerative medicine is suggested as a promising therapeutic strategy for end-stage liver disease. Upon the source of regenerating hepatocytes, liver regeneration could be divided into two categories: hepatocyte-driven liver regeneration (typical regeneration) and liver progenitor cell-driven liver regeneration (alternative regeneration). Due to the massive loss of hepatocytes, the alternative regeneration plays a vital role in end-stage liver disease. Advances in knowledge of liver regeneration and tissue engineering have accelerated the progress of regenerative medicine strategies for end-stage liver disease. In this article, we generally reviewed the recent findings and current knowledge of liver regeneration, mainly regarding aspects of the histological basis of regeneration, histogenesis and mechanisms of hepatocytes' regeneration. In addition, this review provides an update on the regenerative medicine strategies for end-stage liver disease. We conclude that regenerative medicine is a promising therapeutic strategy for end-stage liver disease. However, further studies are still required.

Hepatocyte growth factor mediates a novel form of hepatic stem/progenitor cell-induced tolerance in a rat xenogeneic liver rejection model

We have previously identified novel neural/glial antigen 2-expressing hepatic stem/progenitor cells (NG2+ HSPs) that are beneficial for tissue repair by inhibiting the immune cell response. In this in vivo study, we investigated the use of hepatocyte growth factor (HGF)-secreting NG2+ HSPs as a tolerogen in the well-established Syrian golden hamster (SGH) to Lewis (LEW) xenogeneic rat acute liver rejection (ARJ) model. Liver and blood cells were collected for histology and functional analyses using immunofluorescence staining, western blot, ELISA, and TUNEL assays. All recipient rats were randomly divided into 5 groups (n = 14 rats/group) and treated with: (1) ARJ + PBS: (2) ARJ + NG2: tail vein injection of NG2+ HSPs; (3) ARJ + tacrolimus (FK506, oral administration); (4) ARJ + an anti-cMet functional blocking antibody (a-cMet-Ab, I.V) 24 h before the injection of NG2+ HSPs; (5) ARJ + cHGF (clinically used HGF). LEW to LEW syngeneic rats were considered "normal" (n = 14, namely Syn). Significantly prolonged mean survival times (MSTs) and improved graft functions were observed after NG2+ HSP transplantation. An anti-cMet Ab significantly blocked the effect of NG2+ HSPs, suggesting that the effects were likely associated with HGF secreted from NG2+ HSPs. Notably, when intravenously injected into the xenogeneic rat model, the injected cHGF not only prolonged the MST of recipient rats but also increased the number of TUNEL-expressing xenoreactive cytotoxic T lymphocytes (CD8+ T cells). Based on these results, HGF-secreting NG2+ HSPs may specifically target recipient CD8+ T cells by inducing their apoptosis.

Ductular Reaction in Liver Diseases: Pathological Mechanisms and Translational Significances

Ductular reaction (DR) is characterized by the proliferation of reactive bile ducts induced by liver injuries. DR is pathologically recognized as bile duct hyperplasia and is commonly observed in biliary disorders. It can also be identified in various liver disorders including nonalcoholic fatty liver disease. DR is associated with liver fibrosis and damage, and the extent of DR parallels to patient mortality. DR raises scientific interests because it is associated with transdifferentiation of liver cells and may play an important role in hepatic regeneration. The origin of active cells during DR can be cholangiocytes, hepatocytes, or hepatic progenitor cells, and associated signaling pathways could differ depending on the specific liver injury or animal models used in the study. Although further studies are needed to elucidate detailed mechanisms and the functional roles in liver diseases, DR can be a therapeutic target to inhibit liver fibrosis and to promote liver regeneration. This review summarizes previous studies of DR identified in patients and animal models as well as currently understood mechanisms of DR.

Decellularized Liver Scaffold for Liver Regeneration

After being initially hailed as the ultimate solution to end-stage organ failure, such as end-stage liver disease (ESLD), engineering of vascularized tissues has stalled because of the need for a well-structured circulatory system that can maintain the cells to be seeded inside the construct.In the field of regenerative medicine, decellularized scaffolds, derived mainly from various non-autologous whole organs, have become an emerging treatment technique to overcome this obstacle. As a result of significant progress made in recent years, organogenesis through whole-organ decellularization scaffolds may now become more feasible than ever before. In this chapter, we describe in detail the necessary steps for liver organogenesis using a decellularized acellular scaffold (DAS), seed cell isolation, and recellularization in a bioreactor-like culture system. This new technique to re-engineer organs may have major implications for the fields of drug discovery, organ transplantation, and ultimately regenerative medicine.

Functional liver tissue engineering by an adult mouse liver-derived neuro-glia antigen 2-expressing stem/progenitor population

Deaths due to end-stage liver diseases are increasingly registered annually in the world. Liver transplantation is the ultimate treatment for end-stage liver diseases to date, which has been hampered by a critical shortage of organs. The potential of decellularized liver scaffolds (DLS) derived from solid organs as a three-dimensional platform has been evolved as a promising approach in liver tissue engineering for translating functional liver organ replacements, but questions still exist regarding the optimal cell population for seeding in DLS and the preparation of the DLS themselves. The aim of our study was to utilize a sodium dodecyl sulfate decellularization procedure in combination with a low concentration of trypsin (0.005%)-ethylenediaminetetraacetic acid (0.002%) process to manufacture DLS from whole mouse livers and recellularized with hepatic stem/progenitors for use in liver tissue engineering and injured liver treatment. Results showed that the DLS generated with all the necessary microstructure and the extracellular components to support seeded hepatic stem/progenitor cell attachment, functional hepatic cell differentiation. Hepatic differentiation from stem/progenitor cells loaded by DLS was more efficient than that of the stem/progenitor cells in the two-dimensional cell culture model. In summary, the method of DLS loaded by hepatic stem/progenitor cells provided by this study was effective in maintaining DLS extracellular matrix to introduce seeded stem/progenitor cell differentiation, hepatic-like tissue formation and functional hepatic protein production in vitro that promoted functional recovery and survival in a mouse model of dimethylnitrosamine-induced liver cirrhosis after auxiliary heterotopic liver transplantation. Copyright © 2016 John Wiley & Sons, Ltd.

Comparison of the therapeutic effectiveness of human CD34+ and rat bone marrow mesenchymal stem cells on improvement of experimental liver fibrosis in Wistar rats

BACKGROUND AND OBJECTIVE

Human umbilical cord blood (UCB) cells and bone marrow mesenchymal stem cells (BM-MSCs) have numerous advantages as grafts for cell transplantation. We hypothesized differing impacts of human UCB cells and rat BM-MSCs on reversal of hepatic injury and revival of liver function in carbon tetrachloride (CCl₄)-induced liver fibrosis.

METHODS

Forty rats were divided into 4 groups; control group, CCl₄ group, CCl₄/CD34⁺ group and CCl₄/BM-MSCs group. Blood samples were driven from rats at 4, 8 and 12 weeks to measure serum concentration of albumin and alanine aminotransferase (ALT). Quantitative expression of collagen Iα, TGF-β, α-SMA, albumin, MMP-2, MMP-9 and TNF-α were assessed by polymerase chain reaction. Histopathological examination of the liver tissue was performed. GFP labeled cells were detected in groups injected with stem cells.

RESULTS

Regarding liver function, CD34⁺ were more efficient than BM-MSCs in elevating albumin (P<0.05) and reducing ALT (P<0.05) concentrations. Concerning gene expression, CD34⁺ were more effective than BM-MSCs in reducing gene expressions of collagen Iα (P<0.01), TGF-β1 (P<0.01) and α-SMA (P<0.01). Both CD34⁺ and BM-MSCs have the same efficacy in reducing TNF-α (P<0.001 and P<0.01, respectively). Furthermore, CD34⁺ were more valuable than BM-MSCs in increasing gene expression of albumin (P<0.05) and MMP-9 (P<0.01).

CONCLUSION

Taken together; human UCB CD34⁺ stem cells were more efficient in improvement of experimental liver injury than BM-MSCs. This study highlighted an important role of human UCB CD34⁺ stem cells in liver fibrosis therapy.