Effects of transplanted bone-marrow-derived mesenchymal stem cells in animal models of acute hepatitis

Leveraging stem cells to combat hepatitis: a comprehensive review of recent studies

Hepatitis is a significant global public health concern, with viral infections being the most common cause of liver inflammation. Antiviral medications are the primary treatments used to suppress the virus and prevent liver damage. However, the high cost of these drugs and the lack of awareness and stigma surrounding the disease create challenges in managing hepatitis. Stem cell therapy has arisen as a promising therapeutic strategy for hepatitis by virtue of its regenerative and immunomodulatory characteristics. Stem cells have the exceptional capacity to develop into numerous cell types and facilitate tissue regeneration, rendering them a highly promising therapeutic avenue for hepatitis. In animal models, stem cell therapy has demonstrated worthy results by reducing liver inflammation and improving liver function. Furthermore, clinical trials have been undertaken to assess the safety and effectiveness of stem cell therapy in individuals with hepatitis. This review aims to explore the involvement of stem cells in treating hepatitis and highlight the findings from studies conducted on both animals and humans. The objective of this review is to primarily concentrate on the ongoing and future clinical trials that assess the application of stem cell therapy in the context of hepatitis, including the transplantation of autologous bone marrow-derived stem cells, human induced pluripotent stem cells, and other mesenchymal stem cells. In addition, this review will explore the potential merits and constraints linked to stem cell therapy for hepatitis, as well as its prospective implications in the management of this disease.

Mesenchymal Stem Cell Therapy in Acute Liver Failure

Acute liver failure (ALF) is a severe liver disease syndrome with rapid deterioration and high mortality. Liver transplantation is the most effective treatment, but the lack of donor livers and the high cost of transplantation limit its broad application. In recent years, there has been no breakthrough in the treatment of ALF, and the application of stem cells in the treatment of ALF is a crucial research field. Mesenchymal stem cells (MSCs) are widely used in disease treatment research due to their abundant sources, low immunogenicity, and no ethical restrictions. Although MSCs are effective for treating ALF, the application of MSCs to ALF needs to be further studied and optimized. In this review, we discuss the potential mechanisms of MSCs therapy for ALF, summarize some methods to enhance the efficacy of MSCs, and explore optimal approaches for MSC transplantation.

Establishing an hTERT-driven immortalized umbilical cord-derived mesenchymal stem cell line and its therapeutic application in mice with liver failure

Acute liver failure (ALF) is characterized by rapid liver cell destruction. It is a multi-etiological and fulminant complication with a clinical mortality of over 80%. Therapy using mesenchymal stem cells (MSCs) or MSCs-derived exosomes can alleviate acute liver injury, which has been demonstrated in animal experiments and clinical application. However, similar to other stem cells, different cell sources, poor stability, cell senescence and other factors limit the clinical application of MSCs. To achieve mass production and quality control on stem cells and their exosomes, transfecting umbilical cord mesenchymal stem cell (UCMSC) with lentivirus overexpressing human telomerase reverse transcriptase (hTERT) gene, the hTERT-UCMSC was constructed as an immortalized MSC cell line. Compared with the primary UCMSC (P3) and immortalized cell line hTERT-UCMSC at early passage (P10), the hTERT-UCMSC retained the key morphological and physiological characteristics of UCMSC at the 35th passage (P35), and showed no signs of carcinogenicity and toxic effect in mice. There was no difference in either exosome production or characteristics of exosomes among cultures from P3 primary cells, P10 and P35 immortalized hTERT-UCMSCs. Inoculation of either hTERT-UCMSC (P35) or its exosomes improved the survival rate and liver function of ALF mice induced by thioacetamide (TAA). Our findings suggest that this immortalized cell line can maintain its characteristics in long-term culture. Inoculation of hTERT-UCMSC and its exosomes could potentially be used in clinics for the treatment of liver failure in the future.

Ameliorative effect of bone marrow-derived mesenchymal stem cells on burn-induced hepatic and metabolic derangements in rats

AIMS

The current study aims to investigate the therapeutic potential of bone marrow-derived mesenchymal stem cells (MSCs) as a solo therapy in ameliorating both skin lesions and liver injury induced by cutaneous severe burn injury (SBI) in rats.

MAIN METHODS

In anesthetized male adult Wistar albino rats, 30 % total burn surface area and established hepatic injury was achieved via direct contact of each experimental animal's dorsum with heated metal rod (100 °C) for 10 s. On the next day following burn, human MSCs or mouse MSCs was administered locally around the burn site and intraperitonially (0.5 × 10⁶ cells/rat for each route) and outcomes were investigated at 4 and 14 days following burn induction.

KEY FINDINGS

Both types of MSCs significantly improved skin and liver histology, decreased liver enzymes, and ameliorated oxidative stress in hepatocytes of SBI-rats. Further, SBI-induced rises in hepatic apoptotic marker (caspase-3, Bax) and serum inflammatory markers (TNF-α, IL-1β, and IL-6) were reduced following either human or mouse MSC administration. In addition, MSCs augmented insulin receptor substrate-1, phosphorylated protein kinase-B (phospho-Akt), while alleviating serum glucose levels in SBI-rats. These previous effects persisted even at the 14-day time point.

SIGNIFICANCE

Following single administration, bone marrow-derived MSCs is capable of counteracting SBI-induced skin lesions as well as related hepatic complications, specifically via mitigating postburn hyperglycemia and hyperinflammation.

Amelioration of aflatoxin acute hepatitis rat model by bone marrow mesenchymal stem cells and their hepatogenic differentiation

Background and Aim:

Bone marrow-derived mesenchymal stem cells (BM-MSCs) transplantation and their hepatogenic differentiated cells (HDCs) can be applied for liver injury repair by tissue grafting. Regenerative potentiality in liver cirrhosis models was widely investigated; however, immunomodulation and anti-inflammation in acute hepatitis remain unexplored. This study aimed to explore the immunomodulatory and evaluate twice intravenous (IV) or intrahepatic (IH) administration of either BM-MSCs or middle-stage HDCs on aflatoxin (AF) acute hepatitis rat model.

Materials and Methods:

BM-MSCs viability, phenotypes, and proliferation were evaluated. Hepatogenic differentiation, albumin, and mmmmmmmm-fetoprotein gene expression were assessed. AF acute hepatitis was induced in rats using AFB1 supplementation. The transplantation of BM-MSCs or their HDCs was done either by IV or IH route. Hepatic ultrasound was performed after 3-weeks of therapy. Cytokines profile (tumor necrosis factor-α [TNF-α], interleukin [IL]-4, and IL-10) was assessed. Hepatic bio-indices, serum, and hepatic antioxidant activity were evaluated, besides examining liver histological sections.

Results:

Acute AFB1 showed a significant increase in TNF-α (p<0.01), liver enzyme activities (p<0.05), as well as decrease in IL-4, IL-10, and antioxidant enzyme activities (p<0.05). Cytokines profile was ameliorated in groups treated with IV and IH BM-MCs, showed a negative correlation between IL-4 and TNF-α (p<0.05), and a positive correlation between IL-10 upregulation and TNF-α (p<0.01). In IV HDCs treated group, positive correlations between IL-4 and IL-10 downregulation and TNF-α were observed. However, in IH HDCs group, a significant positive correlation between IL-4 and IL-10 upregulation and TNF-α, were recorded (p<0.05). In addition, IV BM-MSCs and IH HDCs treatments significantly increased antioxidant enzymes activity (p<0.05). IV and IH BM-MSCs significantly ameliorated liver transaminase levels, whereas IH HDCs significantly ameliorated alanine aminotransferase activity and nitric oxide concentration (p<0.05).

Conclusion:

The administration routes of BM-MSCs did not demonstrate any significant difference; however, the IH route of HDCs showed significant amelioration from the IV route. On the other hand, it showed noticeable anti-inflammatory and immunomodulatory improvements in aflatoxicosis rats. Therefore, it can be concluded that acute hepatitis can be treated by a noninvasive IV route without the expense of hepatogenic differentiation. Further research using clinical trials that address several problems regarding engraftment and potentiation are needed to determine the optimal manipulation strategy as well as to achieve better long term effects.

UMSCs Attenuate LPS/D-GalN-induced Acute Liver Failure in Mice by Down-regulating the MyD88/NF-κB Pathway

BACKGROUND AND AIMS

Acute liver failure (ALF) is an inflammatory process of acute liver cell injury. Mesenchymal stem cells (MSCs) are undifferentiated, primitive cells with anti-inflammatory, anti-apoptotic, and multi-directional differentiation abilities. This study aimed to explore the therapeutic mechanism of umbilical cord (U)MSCs in ALF.

METHODS

D-galactosamine (D-GalN) combined with lipopolysaccharide (LPS) was used to establish an ALF model. After model establishment, UMSCs were injected via the tail vein. After UMSC transplantation, the number of mouse deaths was monitored every 12 h. A fully automatic biochemical analyzer was used to detect changes in biochemical analysis. Pathological changes was observed by stained with hematoxylin and eosin.The expression of My D88 was detected by immunohistochemical analysis, quantitative reverse transcription, and western blotting. The expression of NF-κB was detected by quantitative reverse transcription, western blotting.The expression of Bcl-2,Bax were detected by quantitative reverse transcription, western blotting.The expression of TNF-α, IL-1β, IL-6 were detected by enzyme-linked immunosorbent assay.

RESULTS

The 48-h survival rate of the UMSC-treated group was significantly higher than that of the LPS/D-GalN-exposed group. After 24 h of LPS/D-GalN exposure, UMSCs reduced serum alanine aminotransferase and aspartate aminotransferase levels and improved the liver structure. Western blot and real-time fluorescence quantitative nucleic acid amplification analyses showed that UMSCs decreased MyD88 expression, thereby inhibiting LPS/GalN-induced phosphorylation and degradation of inhibitor of nuclear factor (NF)-κB (IκB). Additionally, NF-κB p65 underwent nuclear translocation, inhibiting the production of the inflammatory factors interleukin (IL)-1β, IL-6 and tumor necrosis factor (TNF)-α and played a protective role in ALF by down-regulating the pro-apoptotic gene Bax and up-regulating the anti-apoptotic gene Bcl-2. In summary, these findings indicate that UMSCs play a protective role in LPS/GalN-induced acute liver injury via inhibition of the MyD88 pathway and subsequent inhibition of NF-κB-mediated cytokine production.

CONCLUSIONS

Through the above mechanisms, UMSCs can effectively reduce LPS/D-GalN-induced ALF, reduce mouse mortality, and restore damaged liver function and damaged liver tissue.

Human Wharton's jelly-derived mesenchymal stem cells alleviate concanavalin A-induced fulminant hepatitis by repressing NF-κB signaling and glycolysis

Background

Fulminant hepatitis is a severe life-threatening clinical condition with rapid progressive loss of liver function. It is characterized by massive activation and infiltration of immune cells into the liver and disturbance of inflammatory cytokine production. Mesenchymal stem cells (MSCs) showed potent immunomodulatory properties. Transplantation of MSCs is suggested as a promising therapeutic approach for a host of inflammatory conditions.

Methods

In the current study, a well-established concanavalin A (Con A)-induced fulminant hepatitis mouse model was used to investigate the effects of transplanting human umbilical cord Wharton's jelly-derived MSCs (hWJ-MSCs) on fulminant hepatitis.

Results

We showed that hWJ-MSCs effectively alleviate fulminant hepatitis in mouse models, primarily through inhibiting T cell immunity. RNA sequencing of liver tissues and human T cells co-cultured with hWJ-MSCs showed that NF-κB signaling and glycolysis are two main pathways mediating the protective role of hWJ-MSCs on both Con A-induced hepatitis in vivo and T cell activation in vitro.

Conclusion

In summary, our data confirmed the potent therapeutic role of MSCs-derived from Wharton's jelly of human umbilical cord on Con A-induced fulminant hepatitis, and uncovered new mechanisms that glycolysis metabolic shift mediates suppression of T cell immunity by hWJ-MSCs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02560-x.

Liver regeneration and inflammation: from fundamental science to clinical applications

Liver regeneration is a complex process involving the crosstalk of multiple cell types, including hepatocytes, hepatic stellate cells, endothelial cells and inflammatory cells. The healthy liver is mitotically quiescent, but following toxic damage or resection the cells can rapidly enter the cell cycle to restore liver mass and function. During this process of regeneration, epithelial and non-parenchymal cells respond in a tightly coordinated fashion. Recent studies have described the interaction between inflammatory cells and a number of other cell types in the liver. In particular, macrophages can support biliary regeneration, contribute to fibrosis remodelling by repressing hepatic stellate cell activation and improve liver regeneration by scavenging dead or dying cells in situ. In this Review, we describe the mechanisms of tissue repair following damage, highlighting the close relationship between inflammation and liver regeneration, and discuss how recent findings can help design novel therapeutic approaches.

Bone marrow mesenchymal stem cell co-adjuvant therapy with albendazole for managing Toxocara vitulorum-rat model

Background and Aim:

Toxocara vitulorum is a bovine intestinal nematode. Immune pictures following infection are conflicting and stopping anthelmintic albendazole treatment recording reversed liver abnormalities. The purpose of this work was to evaluate the therapeutic potential of bone marrow mesenchymal stem cells (BMMSCs) therapy, subsequent to albendazole administration in rats infected with T. vitulorum.

Materials and Methods:

The ultrasonographic and histopathological examinations as well as serum liver enzymes activity and the kinetics of recovery were investigated. The correlation of cell-mediated and humoral immune pictures was assessed by assaying immunoglobulins, splenocytes viability, phagocytic index, and Th1/Th2 cytokines.

Results:

The cultured BMMSCs counting were 4.21×10⁴ cells/cm² with 96.03% viability. Flow-cytometric analysis indicated positive CD90 (82%), CD105 (79%) and negative CD34 (0.37%), CD45 (0.42%), attesting to the suitability of the isolated BMMSCs for use in therapy. Transplantation of BMMSCs after albendazole administration significantly reduced the release of liver enzymes (p<0.05) indicating liver cellularity improvement. The ultrasonographic, macroscopic, and histopathological findings confirmed the biochemical results. Significant elevation in the levels of tumor necrosis factor (TNF)-α and interferon (INF)-γ with a decline in interleukin (IL)-4 was observed in the untreated model (p<0.05). However, albendazole treatment followed by BMMSCs therapy significantly lowered the release of TNF-α and INF-γ, associated with significant production of IL-4 and IL-10 (p<0.05).

Conclusion:

The final results indicated that the liver functions, histopathological findings, and immune parameters were aggravated after experimental T. vitulorum infection. Albendazole treatment followed by BMMSCs therapy was found to assist in regeneration of injured hepatic tissue. Besides, it appeared to modulate host defensive immune responses against T. vitulorum antigens. This work could define more clearly the events that manipulate the host immune, histopathological, and biochemical responses to minimize obstacles in using stem cell therapy in animal toxocariosis.

Stem cells from human exfoliated deciduous teeth ameliorate concanavalin A-induced autoimmune hepatitis by protecting hepatocytes from apoptosis

BACKGROUND

Autoimmune hepatitis is a serious autoimmune liver disease that threatens human health worldwide, which emphasizes the urgent need to identify novel treatments. Stem cells from human exfoliated deciduous teeth (SHED), which are easy to obtain in a non-invasive manner, show pronounced proliferative and immunomodulatory capacities.

AIM

To investigate the protective effects of SHED on concanavalin A (ConA)-induced hepatitis in mice, and to elucidate the associated regulatory mechanisms.

METHODS

We used a ConA-induced acute hepatitis mouse model and an in vitro co-culture system to study the protective effects of SHED on ConA-induced autoimmune hepatitis, as well as the associated underlying mechanisms.

RESULTS

SHED infusion could prevent aberrant histopathological liver architecture caused by ConA-induced infiltration of CD3⁺, CD4⁺, tumor necrosis-alpha⁺, and interferon-gamma⁺ inflammatory cells. Alanine aminotransferase and aspartate aminotransferase were significantly elevated in hepatitis mice. SHED infusion could therefore block ConA-induced alanine aminotransferase and aspartate aminotransferase elevations. Mechanistically, ConA upregulated tumor necrosis-alpha and interferon-gamma expression, which was activated by the nuclear factor-kappa B pathway to induce hepatocyte apoptosis, resulting in acute liver injury. SHED administration protected hepatocytes from ConA-induced apoptosis.

CONCLUSION

SHED alleviates ConA-induced acute liver injury via inhibition of hepatocyte apoptosis mediated by the nuclear factor-kappa B pathway. Our findings could provide a potential treatment strategy for hepatitis.

Therapeutic effect of bone marrow mesenchymal stem cells in a rat model of carbon tetrachloride induced liver fibrosis

Background

Liver fibrosis is a major medical problem with high mortality and morbidity rates where the formation of regenerative nodules and cirrhosis leads to loss of liver function and may result in the development of hepatocellular carcinoma. bone marrow mesenchymal stem cells (BM-MSCs) have drawn attention as a novel approach for treatment of liver fibrosis. This study aimed to evaluate the therapeutic effect of BM-MSCs on the liver structure in carbon tetrachloride (CCl₄) induced liver fibrosis in male rats relative to resveratrol and Silybum marianum as standard drugs derived from herbal plants.

Methods

Fifty adult male albino rats (Sprague Dawley strain; 180–220 g mean body weight) were purchased from the Laboratory Animal Unit in the Nile Center of Experimental Research, Mansoura, Egypt. Liver function were determined, isolation and preparation of BM- MSCs and detection of cell-surface markers by flow cytometry.

Results

Animals exposed to CCl₄ developed liver injury characterized by significant increase of liver enzymes, malondialdehyde (MDA), tumor necrosis factor alpha (TNFα), and CYP450, inhibition of antioxidant enzymes, and decreased albumin. Treatment with stem cells enhanced liver state more effectively than resveratrol and S. marianum. It significantly decreased AST, ALT, ALP, MDA, TNF-α, and CYP450 and increased albumin, SOD, GSH, GST, and CAT. Histopathological study and atomic force microscope results confirmed the therapeutic effects of MSCs.

Conclusions

BM-MSCs could restore liver structure and function in CCL₄ induced liver fibrosis rat model, ameliorating the toxicity of CCl₄ and improving liver function tests.

Clinical application of stem cell in patients with end-stage liver disease: progress and challenges

End-stage liver disease (ESLD) is life-threatening disease worldwide, and patients with ESLD should be referred to liver transplantation (LT). However, the use of LT is limited by the lacking liver source, high cost and organ rejection. Thus, other alternative options have been explored. Stem cell therapy may be a potential alternative for ESLD treatment. With the potential of self-renewal and differentiation, both hepatic and extrahepatic stem cells have attracted a lot of attention. Among them, multipotent stem cells are most widely studies owing to their characteristics. Multipotent stem cells mainly consist of two subpopulations: hematopoietic stem cells (HSCs) and mesenchymal stem cells (MSCs). Accumulating evidences have proved that either bone marrow (BM)-derived HSCs mobilized by granulocyte colony-stimulating factor or MSCs transplantation can improve the biochemical indicators of patients with ESLD. However, there are some challenges to be resolved before stem cells widely used in clinic, including the best stem cell source, the optimal route for stem cells transplantation, and the dose and frequency of stem cell injected. The purpose of this review is to discuss the potential of stem cell in liver diseases, particularly, the clinical progress and challenges of multipotent stem cells in the field of ESLD.

The clinical application of mesenchymal stem cells in liver disease: the current situation and potential future

Liver disease is a major health issue which present poor clinical treatment performance. Cirrhosis and liver failure are common clinical manifestations of liver diseases. Liver transplantation is recognized as the ultimate and most efficient therapy to the end stage of liver disease. But it was limited by the shortage of honor organs and high cost. Nowadays, stem cell therapy gained more and more attention due to its attractive efficacy in treating liver disease especially in cirrhosis during the clinical trials. Mesenchymal stem cell (MSC) can be differentiated into hepatocytes, promote liver regeneration, inhibit liver fibrosis and induce liver apoptosis, particularly via paracrine mechanisms. This review will highlight recent clinical applications of MSC, providing the available evidence and discussing some unsolved questions in treating liver disease.

Exosomes derived from human umbilical cord mesenchymal stem cells ameliorate IL-6-induced acute liver injury through miR-455-3p

Background

Using a toxin-induced nonhuman primate model of acute liver failure (ALF), we previously reported that peripheral infusion of human umbilical cord mesenchymal stem cells (hUC-MSCs) strongly suppresses the activation of circulating monocytes and interleukin-6 (IL-6) production, thereby disrupting the development of a cytokine storm and improving the prognosis of monkeys. MSCs are considered to play a therapeutic role under different stresses by adaptively producing specific factors, prompting us to investigate the factors that hUC-MSCs produce in response to high serum levels of IL-6, which plays a critical role in initiating and accelerating ALF.

Methods

We stimulated hUC-MSCs with IL-6, and the hUC-MSC-derived exosomes were deeply sequenced. The miRNAs in the exosomes that have potential to suppress IL-6-associated signaling pathway were screened, and the role of one of the most possible miRNAs was tested in the mouse model of inflammatory liver injury.

Result

We determined that miR-455-3p, which is secreted through exosomes and potentially targets PI3K signaling, was highly produced by hUC-MSCs with IL-6 stimulation. The miR-455-3p-enriched exosomes could inhibit the activation and cytokine production of macrophages challenged with lipopolysaccharide (LPS) both in vivo and in vitro. In a chemical liver injury mouse model, enforced expression of miR-455-3p could attenuate macrophage infiltration and local liver damage and reduce the serum levels of inflammatory factors, thereby improving liver histology and systemic disorder.

Conclusions

miR-455-3p-enriched exosomes derived from hUC-MSCs are a promising therapy for acute inflammatory liver injury.

Mesenchymal stromal cells promote liver regeneration through regulation of immune cells

The liver is sensitive to pathogen-induced acute or chronic liver injury, and liver transplantation (LT) is the only effective strategy for end-stage liver diseases. However, the clinical application is limited by a shortage of liver organs, immunological rejection and high cost. Mesenchymal stromal cell (MSC)-based therapy has gradually become a hot topic for promoting liver regeneration and repairing liver injury in various liver diseases, since MSCs are reported to migrate toward injured tissues, undergo hepatogenic differentiation, inhibit inflammatory factor release and enhance the proliferation of liver cells in vivo. MSCs exert immunoregulatory effects through cell-cell contact and the secretion of anti-inflammatory factors to inhibit liver inflammation and promote liver regeneration. In addition, MSCs are reported to effectively inhibit the activation of cells of the innate immune system, including macrophages, natural killer (NK) cells, dendritic cells (DCs), monocytes and other immune cells, and inhibit the activation of cells of the adaptive immune system, including T lymphocytes, B lymphocytes and subsets of T cells or B cells. In the current review, we mainly focus on the potential effects and mechanisms of MSCs in inhibiting the activation of immune cells to attenuate liver injury in models or patients with acute liver failure (ALF), nonalcoholic fatty liver disease (NAFLD), and liver fibrosis and in patients or models after LT. We highlight that MSC transplantation may replace general therapies for eliminating acute or chronic liver injury in the near future.

Exploring the Most Promising Stem Cell Therapy in Liver Failure: A Systematic Review

Background

Alternative approaches to transplantation for liver failure are needed. One of the alternative approaches is stem cell therapy. However, stem cell therapy in liver failure is not standardized yet, as every centre have their own methods. This systematic review is aimed at compiling and analyzing the various studies that use stem cells to treat liver failure, to get an insight into potential protocols in terms of safety and efficacy by comparing them to controls.

Methods

This systematic review was done according to PRISMA guidelines and submitted for registration in PROSPERO (registration number CRD42018106119). All published studies in PubMed/MEDLINE and Cochrane Library, using key words: “human” and “stem cell” AND “liver failure” on 16^th June 2018, without time restriction. In addition, relevant articles that are found during full-text search were added. Inclusion criteria included all original articles on stem cell use in humans with liver failure. Data collected included study type, treatment and control number, severity of disease, concomitant therapy, type and source of cells, passage of cells, dose, administration route, repeats, and interval between repeats, outcomes, and adverse events compared to controls. Data were analyzed descriptively to determine the possible causes of adverse reactions, and which protocols gave a satisfactory outcome, in terms of safety and efficacy.

Results

There were 25 original articles, i.e., eight case studies and 17 studies with controls.

Conclusion

Among the various adult stem cells that were used in human studies, MSCs from the bone marrow or umbilical cord performed better compared to other types of adult stem cells, though no study showed a complete and sustainable performance in the outcome measures. Intravenous (IV) route was equal to invasive route. Fresh or cryopreserved, and autologous or allogeneic MSCs were equally beneficial; and giving too many cells via intraportal or the hepatic artery might be counterproductive.

Immune modulation by mesenchymal stem cells

Mesenchymal stem cells (MSCs) can be derived from various adult tissues with multipotent and self‐renewal abilities. The characteristics of presenting no major ethical concerns, having low immunogenicity and possessing immune modulation functions make MSCs promising candidates for stem cell therapies. MSCs could promote inflammation when the immune system is underactivated and restrain inflammation when the immune system is overactivated to avoid self‐overattack. These cells express many immune suppressors to switch them from a pro‐inflammatory phenotype to an anti‐inflammatory phenotype, resulting in immune effector cell suppression and immune suppressor cell activation. We would discuss the mechanisms governing the immune modulation function of these cells in this review, especially the immune‐suppressive effects of MSCs.

Mesenchymal Stem Cells for Liver Regeneration in Liver Failure: From Experimental Models to Clinical Trials

The liver centralizes the systemic metabolism and thus controls and modulates the functions of the central and peripheral nervous systems, the immune system, and the endocrine system. In addition, the liver intervenes between the splanchnic and systemic venous circulation, determining an abdominal portal circulatory system. The liver displays a powerful regenerative potential that rebuilds the parenchyma after an injury. This regenerative mission is mainly carried out by resident liver cells. However, in many cases this regenerative capacity is insufficient and organ failure occurs. In normal livers, if the size of the liver is at least 30% of the original volume, hepatectomy can be performed safely. In cirrhotic livers, the threshold is 50% based on current practice and available data. Typically, portal vein embolization of the part of the liver that is going to be resected is employed to allow liver regeneration in two-stage liver resection after portal vein occlusion (PVO). However, hepatic resection often cannot be performed due to advanced disease progression or because it is not indicated in patients with cirrhosis. In such cases, liver transplantation is the only treatment possibility, and the need for transplantation is the common outcome of progressive liver disease. It is the only effective treatment and has high survival rates of 83% after the first year. However, donated organs are becoming less available, and mortality and the waiting lists have increased, leading to the initiation of living donor liver transplantations. This type of transplant has overall complications of 38%. In order to improve the treatment of hepatic injury, much research has been devoted to stem cells, in particular mesenchymal stem cells (MSCs), to promote liver regeneration. In this review, we will focus on the advances made using MSCs in animal models, human patients, ongoing clinical trials, and new strategies using 3D organoids.

Therapeutic Potential of Plasma Proteins Derived from Umbilical Cord Blood for Acute Liver Failure

There are very limited clinically viable treatment options for acute liver failure, a life-threatening condition that rapidly progresses to loss of liver function. In this study, we aim to evaluate the therapeutic potential of UCBP for acute liver failure induced in a rat model by D-galactosamine (GalN). F344 rats were randomly divided into two groups (control and UCBP-treated) after GalN injection. The therapeutic effects of UCBP were evaluated based on survival rate, H&E staining, TUNEL, PCNA staining, and in vivo BrdU labeling. Hepatocyte proliferation and the therapeutic mechanisms of UCBP were examined with BrdU and Western blot assay in vitro. The survival rate in the UCBP-treated group was found to be increased compared to the control group (85 vs 55%, P = 0.029). UCBP treatment significantly decreased apoptosis and increased cell proliferation. These effects may be secondary to specific bioactive molecules in UCBP. In vitro experiments revealed that adiponectin is one of the key biologically active components of UCBP in facilitating this result and promoting hepatocyte proliferation. Furthermore, this effect is mediated by p38/ERK mitogen-activated protein kinase (MAPK) signaling pathways. Therefore, this uncomplicated and clinically accessible approach may serve as effective bridge therapy for acute liver failure.

Progress in mesenchymal stem cell-based therapy for acute liver failure

Acute liver failure is a life-threatening clinical syndrome characterized by rapid development of hepatocellular necrosis leading to high mortality and resource costs. Numerous treatment strategies for acute liver failure simply prevent complications and decelerate disease progression. The only curative treatment for acute liver failure is liver transplantation, but there are many restrictions on the application of liver transplantation. In recent years, a growing number of studies have shown that stem cells can effectively treat acute liver failure. Several types of stem cells have been used to study liver diseases; mesenchymal stem cells are most commonly used because they are easy to obtain and present no ethical problems. The aims of this article are to review the current knowledge regarding therapeutic mechanisms of mesenchymal stem cells in acute liver failure, to discuss recent advancements in preclinical and clinical studies in the treatment of mesenchymal stem cells, and to summarize the methodological improvement of mesenchymal stem cell transplantation in treating liver failure.

Undifferentiated Adipose Tissue Stem Cell Transplantation Promotes Hepatic Regeneration, Ameliorates Histopathologic Damage of the Liver, and Upregulates the Expression of Liver Regeneration- and Liver-Specific Genes in a Rat Model of Partial Hepatectomy

Objective

Adipose tissue stem cells (ADSCs) present a promising therapeutic method to alleviate liver failure (LF). The purpose of this prospective study was to evaluate the efficacy of undifferentiated ADSC transplantation on liver regeneration and on the expression of liver regeneration- and liver-specific genes, following 60% partial hepatectomy (PHx).

Methods

Sixty female rats were subjected to PHx and were transplanted with 10⁶ or 2 × 10⁶ ADSCs, either into the portal vein (PV) or into the hepatic parenchyma. Animals of the control group were not transplanted and served as controls. Animals were sacrificed on the 4th, the 7th, or the 15th postoperative day (POD).

Results

The transplanted ADSCs were successfully engrafted into the liver parenchyma and ameliorated the histopathologic damage on the 7th and 15th POD. All transplanted animals demonstrated a significantly higher liver regeneration rate on the 4th and 7th POD, compared with the control group. The expression of hepatocyte growth factor, α-fetoprotein, tyrosine aminotransferase, hepatocyte nuclear factor 4a, and cytochrome P450 1A2 was significantly upregulated, compared with the control group.

Conclusions

Although undifferentiated, ADSC transplantation significantly enhanced the liver regeneration process. These findings may be proven clinically valuable, especially in cases of acute LF.

Current Perspectives Regarding Stem Cell-Based Therapy for Liver Cirrhosis

Liver cirrhosis is a major cause of mortality and a common end of various progressive liver diseases. Since the effective treatment is currently limited to liver transplantation, stem cell-based therapy as an alternative has attracted interest due to promising results from preclinical and clinical studies. However, there is still much to be understood regarding the precise mechanisms of action. A number of stem cells from different origins have been employed for hepatic regeneration with different degrees of success. The present review presents a synopsis of stem cell research for the treatment of patients with liver cirrhosis according to the stem cell type. Clinical trials to date are summarized briefly. Finally, issues to be resolved and future perspectives are discussed with regard to clinical applications.

Umbilical Cord-Derived Mesenchymal Stem Cell Transplantation in Hepatitis B Virus Related Acute-on-Chronic Liver Failure Treated with Plasma Exchange and Entecavir: a 24-Month Prospective Study

BACKGROUND & AIM

Search for an effective therapy for patients with hepatitis B virus related acute-on-chronic liver failure (HBV-ACLF) remains an important issue. This study investigated the efficacy of umbilical cord-derived mesenchymal stem cell (UC-MSC) transplantation in patients with HBV-ACLF.

METHODS

45 consecutive entecavir-treated HBV-ACLF patients were prospectively studied. Among these patients, 11 received both plasma exchange (PE) and a single transplantation of UC-MSCs (group A), while 34 received only PE (group B). The primary endpoint was survival at 24 months.

RESULTS

Compared with group B, levels of albumin, alanine aminotransferase, aspartate aminotransferase, total bilirubin, direct bilirubin, prothrombin time (PT), international normalized ratio (INR) and model for end-stage liver disease score in group A improved significantly at 4 weeks after transplantation (p < 0.05). Levels of albumin, PT and INR in group A were also markedly improved at 24 months (p < 0.05). Group A had significantly higher cumulative survival rate at 24 months (54.5 % v.s. 26.5 %, p = 0.015 by log rank test). Between the two groups, levels of creatinine, White blood cell, hemoglobin and platelet were similar. HBeAg loss and hepatocellular carcinoma incidence were similar at 24 months. Group assignment (relative risk: 2.926, 95%confidence interval: 1.043-8.203, p = 0.041) was an independent predictor for survival at 24 months. Success rate of UC-MSC transplantation was 100 % in group A. No severe adverse event was observed in any patient.

CONCLUSION

UC-MSC transplantation is safe and effective for HBV-ACLF patients treated with PE and entecavir. It further improves the hepatic function and survival.

Mesenchymal Stem Cell-Dependent Modulation of Liver Diseases

Acute liver failure and cirrhosis display sequential and overlapping severe pathogenic processes that include inflammation, hepatocyte necrosis, and fibrosis, carrying a high mortality rate. Mesenchymal stem cells (MSCs) are a heterogeneous subset of stromal stem cells with immunonodulatory characteristics. MSCs are considered to act through multiple mechanisms to coordinate a dynamic, integrated response to liver inflammation and fibrosis, which prevents the progressive distortion of hepatic architecture. Accordingly, MSCs as well as their products have been investigated as a novel therapeutic approach for the treatment of inflammatory and fibrotic liver diseases.

In this review, we highlight the current findings on the MSC-based modulation of liver inflammation and fibrosis, and the possible use of MSCs in the therapy of immune-mediated liver pathology. We briefly describe the cellular and molecular mechanisms involved in MSC-dependent modulation of cytokine production, phenotype and function of liver infiltrated inflammatory cells and compare effects of engrafted MSCs versus MSC-generated conditioned medium (MSC-CM) in the therapy of acute liver injury. In order to elucidate therapeutic potential of MSCs and their products in modulation of chronic liver inflammation and fibrosis, we present the current findings regarding pathogenic role of immune cells in liver fibrosis and describe mechanisms involved in MSC-dependent modulation of chronic liver inflammation with the brief overview of on-going and already published clinical trials that used MSCs for the treatment of immune mediated chronic liver diseases. The accumulating evidence shows that MSCs had a significant beneficial effect in the treatment of immune-mediated liver diseases.

Adipose-derived mesenchymal stem cells slow disease progression of acute-on-chronic liver failure

A serious complication of chronic hepatic insufficiency is acute-on-chronic liver failure, a recognized syndrome characterized by acute decompensation of cirrhosis and organ/system failure. We investigated the use of adipose-derived mesenchymal stem cells (AD-MSCs) in an experimental model of acute-on-chronic liver failure, developed by microsurgical extrahepatic cholestasis in rats. Rats undergoing microsurgical extrahepatic cholestasis were treated by intraparenchymal liver injection of human or rat AD-MSCs, undifferentiated or previously differentiated in vitro toward the hepatocyte lineage. The groups treated with rat AD-MSCs showed less ascites, lower hepato- and splenomegaly, less testicular atrophy, and an improvement in serum biochemical hepatic parameters. There was also an improvement in histological liver changes, in which the area of fibrosis and bile duct proliferation were significantly decreased in the group treated with predifferentiated rat AD-MSCs. In conclusion, an isograft of hepatocyte-predifferentiated AD-MSCs injected intraparenchymally 2 weeks after microsurgery in extrahepatic cholestatic rats prevents secondary complications of acute-on-chronic hepatic failure. These data support the potential use of autologous AD-MSCs in the treatment of human cholestasis, and specifically of newborn biliary atresia, which could be beneficial for patients awaiting transplant.

Stem Cell Therapies for Treatment of Liver Disease

Cell therapy is an emerging form of treatment for several liver diseases, but is limited by the availability of donor livers. Stem cells hold promise as an alternative to the use of primary hepatocytes. We performed an exhaustive review of the literature, with a focus on the latest studies involving the use of stem cells for the treatment of liver disease. Stem cells can be harvested from a number of sources, or can be generated from somatic cells to create induced pluripotent stem cells (iPSCs). Different cell lines have been used experimentally to support liver function and treat inherited metabolic disorders, acute liver failure, cirrhosis, liver cancer, and small-for-size liver transplantations. Cell-based therapeutics may involve gene therapy, cell transplantation, bioartificial liver devices, or bioengineered organs. Research in this field is still very active. Stem cell therapy may, in the future, be used as a bridge to either liver transplantation or endogenous liver regeneration, but efficient differentiation and production protocols must be developed and safety must be demonstrated before it can be applied to clinical practice.

Allo-transplantation of mesenchymal stem cells attenuates hepatic injury through IL1Ra dependent macrophage switch in a mouse model of liver disease

BACKGROUND & AIMS

Autologous transplantation of mesenchymal stem cells (MSCs) reduces concanavalin A (Con A)-induced hepatic injury in mice. However, the mechanism is unclear and the therapeutic effect of allo-transplantation remains unknown. Our aim was to investigate the effects and mechanisms related to allo-transplantation of MSCs when used to treat Con A hepatic injury.

METHODS

After Con A-induced liver injury was created in C57BL/6J mice, MSCs derived from BALB/c mice or a vehicle control was administered.

RESULTS

Allo-transplantation of MSCs derived from BALB/c mice attenuated hepatic apoptosis in C57BL/6J mice that had undergone Con A-induced liver injury. MSCs increased the level of serum interleukin (IL)-10 and the phosphorylation of hepatic STAT3, but decreased the level of hepatic IFN-γ and phospho-STAT1. Notably, the administered MSCs were trapped mostly in the lungs and promoted the macrophage M2 switch, which contributed to the increased IL10 levels in the lungs and serum. Loss of the therapeutic effect was observed after knock-down of the expression of interleukin 1 receptor antagonist (IL1Ra) in the MSCs. In vitro investigation supported the hypothesis that MSCs are able to switch Con A-stimulated macrophages to the M2 phenotype, which results in an increase in IL10 production.

CONCLUSIONS

Allo-transplantation of MSCs reduces Con A liver injury by increasing IL10 production through an IL1Ra dependent macrophage switch.

Stem cell-based regenerative opportunities for the liver: State of the art and beyond

The existing mismatch between the great demand for liver transplants and the number of available donor organs highlights the urgent need for alternative therapeutic strategies in patients with acute or chronic liver failure. The rapidly growing knowledge on stem cell biology and the intrinsic repair processes of the liver has opened new avenues for using stem cells as a cell therapy platform in regenerative medicine for hepatic diseases. An impressive number of cell types have been investigated as sources of liver regeneration: adult and fetal liver hepatocytes, intrahepatic stem cell populations, annex stem cells, adult bone marrow-derived hematopoietic stem cells, endothelial progenitor cells, mesenchymal stromal cells, embryonic stem cells, and induced pluripotent stem cells. All these highly different cell types, used either as cell suspensions or, in combination with biomaterials as implantable liver tissue constructs, have generated great promise for liver regeneration. However, fundamental questions still need to be addressed and critical hurdles to be overcome before liver cell therapy emerges. In this review, we summarize the state-of-the-art in the field of stem cell-based therapies for the liver along with existing challenges and future perspectives towards a successful liver cell therapy that will ultimately deliver its demanding goals.

Mesenchymal stromal cell therapy in liver disease: opportunities and lessons to be learnt?

End-stage liver disease is responsible for 30,000 deaths per year in the United States alone, and it is continuing to increase every year. With liver transplantation the only curative treatment currently available, new therapies are in great demand. Mesenchymal stem cells (MSC) offer an opportunity to both treat liver inflammatory damage, as well as reverse some of the changes that occur following chronic liver injury. With the ability to regulate both the innate and adaptive immune system, as well as both inhibit and promote apoptosis of effector inflammatory cells, there are numerous therapeutic opportunities for MSC in acute and chronic liver disease. This article critically appraises the potential therapeutic roles of MSC in liver disease, as well as the barriers to their adoption into clinical practice.

Therapeutic effects of transplantation of bone marrow mesenchymal stem cells on ConA-induced acute liver injury in mice

AIM: To assess the therapeutic action of bone marrow mesenchymal stem cells (BMMSCs) on concanavalin A (ConA)-induced acute liver injury in mice.

METHODS: BMMSCs were isolated from bone tissues of C57BL/6 mice, cultured, identified, and labeled with CM-Dil in vitro. C57BL/6 mice were injected with different doses of ConA to find the optimal concentration to generate a mouse model of ConA-induced hepatitis. C57BL/6 mice were randomly divided into groups I-IV and a control group. Groups I-IV were injected with CM-Dil labeled BMMSCs at 1 × 10⁵, 5 × 10⁵, 1 × 10⁶, and 1 × 10⁷, respectively. The control group was injected with PBS. Serum levels of liver enzymes [alanine transaminase (ALT) and aspartate transaminase (AST)], cytokines [tumor necrosis factor-α (TNF-α), interferon-γ (IFN-γ), and interleukin-4 (IL-4)], histopathology, and localization of BMMSCs were investigated at 24 h after injection.

RESULTS: We collected cells in line with the characteristics of BMMSCs, and the rate of CM-Dil labeling was over 90%. With increasing doses of ConA, the severity of liver injury increased, and 15 mg/kg was the optimal dose for inducing acute liver injury in C57BL/6 mice. Serum levels of ALT, AST, TNF-α, IFN-γ, IL-4 and Knodell score were significantly reduced in groups II and III as compared with the control group (P < 0.05). Injected CM-Dil labeled BMMSCs were located in the liver of ConA-injected mice, but were not detected in the heart, lung or spleen.

CONCLUSION: The therapeutic efficacy of BMMSCs for ConA-induced hepatitis is defined. It is possible that BMMSCs migrate to the inflammatory sites and reduce the production of TNF-α, IFN-γ and IL-4 to alleviate liver injury induced by ConA.

MR tracking of SPIO-labeled mesenchymal stem cells in rats with liver fibrosis could not monitor the cells accurately

Our previous study showed that in vivo magnetic resonance (MR) imaging is effective in tracking superparamagnetic iron oxide (SPIO)-labeled bone marrow mesenchymal stem cells (BMSCs) in rats with liver fibrosis. SPIO-labeling-induced signal reduction on MR images was completely reversed within 15 days after transplantation. It is still unclear whether the signal changes in MR imaging could reflect the number of transplanted cells in the liver. In the present study, BMSCs of male rats were doubly labeled with enhanced green fluorescent protein (EGFP) and SPIO and injected intravascularly into female rats with liver fibrosis. At different time points after injection, MR imaging was performed. The distribution of SPIO particles and EGFP-positive cells was determined by Prussian blue staining and EGFP immunohistochemistry, respectively. The distribution of transplanted BMSCs in various organs was assessed by detection of the SRY gene using real-time quantitative PCR. At 15 days post transplantation, the numbers of transplanted cells were significantly decreased in the lung, kidney, spleen and muscle, but not liver and heart, in comparison with those at 7 days after transplantation. EGFP staining-positive cells were observed in the liver intralobular parenchyma, while Prussian blue staining was negative at 42 days after transplantation. Taken together, SPIO particles and EGFP-labeled BMSCs show a different tissue distribution pattern in rats with liver fibrosis after a long-term period of monitoring. SPIO-based MR imaging may not be suitable for long-term tracking of transplanted BMSCs in vivo.

Bone marrow-derived mesenchymal stem cells attenuate acute liver injury and regulate the expression of fibrinogen-like-protein 1 and signal transducer and activator of transcription 3

In recent years, bone marrow-derived mesenchymal stem cells (BMSCs) have been demonstrated to exert extensive therapeutic effects on acute liver injury; however, the underlying mechanisms of these effects have remained to be elucidated. The present study focused on the potential anti-apoptotic and pro-regenerative effects of BMSCs in D-galactosamine (D-Gal) and lipopolysaccharide (LPS)-induced acute liver injury in rats. An experimental rat acute liver injury model was established by intraperitoneal injection of D-Gal (400 mg/kg) and LPS (80 μg/kg). BMSCs and an identical volume of saline were administered via the caudal vein 2 h after the D-Gal and LPS challenge. Subsequently, the serum samples were collected to detect the levels of alanine aminotransferase and aspartate aminotransferase. Hematoxylin and eosin staining, terminal deoxynucleotidyl transferase-mediated nick-end labeling assay and immunohistochemical staining were performed to determine apoptosis, regeneration and histological changes of liver sections. Western blotting and reverse transcription-quantitative polymerase chain reaction were performed to detect the protein and mRNA expression levels of fibrinogen-like-protein 1 (FGL1), phosphorylated signal transducer and activator of transcription 3 (p-STAT3), STAT3 and B-cell lymphoma 2 (Bcl-2) and Bcl-2 associated X protein (Bax) in liver tissue samples. The results indicated that intravenous transplantation of BMSCs significantly decreased the levels of alanine aminotransferase and aspartate aminotransferase, and reduced hepatocellular necrosis and inflammatory cell infiltration. Additionally, a terminal deoxynucleotidyl transferase-mediated nick-end labeling assay and immunohistochemical staining revealed that BMSC treatment reduced hepatocyte apoptosis and enhanced liver regeneration. Furthermore, Bcl-2 expression was increased, whilst the protein expression of Bax was reduced. The expression of FGL1 and p-STAT3 were elevated concurrently with the improvement of liver function. These results demonstrated that BMSCs may provide a promising potential agent for the prevention of acute liver injury via inhibition of hepatocyte apoptosis and acceleration of liver regeneration. The mechanism may be, a least in part, a consequence of the upregulation of FGL1 expression and the induction of STAT3 phosphorylation.

Tonsil-derived mesenchymal stem cells alleviate concanavalin A-induced acute liver injury

Acute liver failure, the fatal deterioration of liver function, is the most common indication for emergency liver transplantation, and drug-induced liver injury and viral hepatitis are frequent in young adults. Stem cell therapy has come into the limelight as a potential therapeutic approach for various diseases, including liver failure and cirrhosis. In this study, we investigated therapeutic effects of tonsil-derived mesenchymal stem cells (T-MSCs) in concanavalin A (ConA)- and acetaminophen-induced acute liver injury. ConA-induced hepatitis resembles viral and immune-mediated hepatic injury, and acetaminophen overdose is the most frequent cause of acute liver failure in the United States and Europe. Intravenous administration of T-MSCs significantly reduced ConA-induced hepatic toxicity, but not acetaminophen-induced liver injury, affirming the immunoregulatory capacity of T-MSCs. T-MSCs were successfully recruited to damaged liver and suppressed inflammatory cytokine secretion. T-MSCs expressed high levels of galectin-1 and -3, and galectin-1 knockdown which partially diminished interleukin-2 and tumor necrosis factor α secretion from cultured T-cells. Galectin-1 knockdown in T-MSCs also reversed the protective effect of T-MSCs on ConA-induced hepatitis. These results suggest that galectin-1 plays an important role in immunoregulation of T-MSCs, which contributes to their protective effect in immune-mediated hepatitis. Further, suppression of T-cell activation by frozen and thawed T-MSCs implies great potential of T-MSC banking for clinical utilization in immune-mediated disease.