Anti-TGFβ-1 receptor inhibitor mediates the efficacy of the human umbilical cord mesenchymal stem cells against liver fibrosis through TGFβ-1/Smad pathway

Human umbilical cord mesenchymal stem cells improve uterine incision healing after cesarean delivery in rats by modulating the TGF-β/Smad signaling pathway

OBJECTIVE

Although human umbilical cord-derived mesenchymal stem cells (HU-MSCs) have attracted increasing attention because of their pivotal functions in the process of wound healing, the underlying molecular mechanisms have been poorly understood. It has been shown that the TGF-β/Smad signaling pathway plays an important role in the process of scar formation. The present study focused on exploring whether HU-MSCs improve uterine incision healing after cesarean delivery in rats via the TGF-β/Smad signaling pathway.

STUDY DESIGN

Pregnant rats were randomly assigned to three groups, including the NP group, incision-injected group (HU-MSCs1 group), and tail vein-injected group (HU-MSCs2 group), and 30 days after cesarean section, sampling was carried out to further explore the specific mechanisms from tissue and protein levels.

RESULTS

HU-MSCs secretion could inhibit the fibrosis of scar tissue. We observed that the TGF-β induced expression of TGF-β1, Smad2, and Smad3 was attenuated upon HU-MSCs treatment in scar tissue, while the decrease in TGF-β3 expression was enhanced by HU-MSCs. Furthermore, HU-MSCs treatment accelerated wound healing and attenuated collagen deposition in a damaged uterine rat model, leading to the promoting of uterine incision scarring. In addition, the expression of alpha-smooth muscle actin (a-SMA) was enhanced by HU-MSCs treatment.

CONCLUSION

HU-MSCs transplantation promotes rat cesarean section uterine incision scar healing by modulating the TGF-β/Smad signaling pathway.

Stem cell-based therapy for fibrotic diseases: mechanisms and pathways

Fibrosis is a pathological process, that could result in permanent scarring and impairment of the physiological function of the affected organ; this condition which is categorized under the term organ failure could affect various organs in different situations. The involvement of the major organs, such as the lungs, liver, kidney, heart, and skin, is associated with a high rate of morbidity and mortality across the world. Fibrotic disorders encompass a broad range of complications and could be traced to various illnesses and impairments; these could range from simple skin scars with beauty issues to severe rheumatologic or inflammatory disorders such as systemic sclerosis as well as idiopathic pulmonary fibrosis. Besides, the overactivation of immune responses during any inflammatory condition causing tissue damage could contribute to the pathogenic fibrotic events accompanying the healing response; for instance, the inflammation resulting from tissue engraftment could cause the formation of fibrotic scars in the grafted tissue, even in cases where the immune system deals with hard to clear infections, fibrotic scars could follow and cause severe adverse effects. A good example of such a complication is post-Covid19 lung fibrosis which could impair the life of the affected individuals with extensive lung involvement. However, effective therapies that halt or slow down the progression of fibrosis are missing in the current clinical settings. Considering the immunomodulatory and regenerative potential of distinct stem cell types, their application as an anti-fibrotic agent, capable of attenuating tissue fibrosis has been investigated by many researchers. Although the majority of the studies addressing the anti-fibrotic effects of stem cells indicated their potent capabilities, the underlying mechanisms, and pathways by which these cells could impact fibrotic processes remain poorly understood. Here, we first, review the properties of various stem cell types utilized so far as anti-fibrotic treatments and discuss the challenges and limitations associated with their applications in clinical settings; then, we will summarize the general and organ-specific mechanisms and pathways contributing to tissue fibrosis; finally, we will describe the mechanisms and pathways considered to be employed by distinct stem cell types for exerting anti-fibrotic events.

Mechanisms of Action of Mesenchymal Stem Cells in Metabolic-Associated Fatty Liver Disease

Metabolic-associated fatty liver disease (MAFLD) is currently the most common chronic liver disease worldwide. However, its pathophysiological mechanism is complicated, and currently, it has no FDA-approved pharmacological therapies. In recent years, mesenchymal stem cell (MSC) therapy has attracted increasing attention in the treatment of hepatic diseases. MSCs are multipotent stromal cells that originated from mesoderm mesenchyme, which have self-renewal and multipotent differentiation capability. Recent experiments and studies have found that MSCs have the latent capacity to be used for MAFLD treatment. MSCs have the potential to differentiate into hepatocytes, which could be induced into hepatocyte-like cells (HLCs) with liver-specific morphology and function under appropriate conditions to promote liver tissue regeneration. They can also reduce liver tissue injury and reverse the development of MAFLD by regulating immune response, antifibrotic activities, and lipid metabolism. Moreover, several advantages are attributed to MSC-derived exosomes (MSC-exosomes), such as targeted delivery, reliable reparability, and poor immunogenicity. After entering the target cells, MSC-exosomes help regulate cell function and signal transduction; thus, it is expected to become an emerging treatment for MAFLD. In this review, we comprehensively discussed the roles of MSCs in MAFLD, main signaling pathways of MSCs that affect MAFLD, and mechanisms of MSC-exosomes on MAFLD.

Mesenchymal stromal cells (MSCs) and their exosome in acute liver failure (ALF): a comprehensive review

Recently, mesenchymal stromal cells (MSCs) and their derivative exosome have become a promising approach in the context of liver diseases therapy, in particular, acute liver failure (ALF). In addition to their differentiation into hepatocytes in vivo, which is partially involved in liver regeneration, MSCs support liver regeneration as a result of their appreciated competencies, such as antiapoptotic, immunomodulatory, antifibrotic, and also antioxidant attributes. Further, MSCs-secreted molecules inspire hepatocyte proliferation in vivo, facilitating damaged tissue recovery in ALF. Given these properties, various MSCs-based approaches have evolved and resulted in encouraging outcomes in ALF animal models and also displayed safety and also modest efficacy in human studies, providing a new avenue for ALF therapy. Irrespective of MSCs-derived exosome, MSCs-based strategies in ALF include administration of native MSCs, genetically modified MSCs, pretreated MSCs, MSCs delivery using biomaterials, and also MSCs in combination with and other therapeutic molecules or modalities. Herein, we will deliver an overview regarding the therapeutic effects of the MSCs and their exosomes in ALF. As well, we will discuss recent progress in preclinical and clinical studies and current challenges in MSCs-based therapies in ALF, with a special focus on in vivo reports.

From hair to liver: emerging application of hair follicle mesenchymal stem cell transplantation reverses liver cirrhosis by blocking the TGF-β/Smad signaling pathway to inhibit pathological HSC activation

Liver cirrhosis (LC) involves multiple systems throughout the body, and patients with LC often die of multiple organ failure. However, few drugs are useful to treat LC. Hair follicle mesenchymal stem cells (HF-MSCs) are derived from the dermal papilla and the bulge area of hair follicles and are pluripotent stem cells in the mesoderm with broad prospects in regenerative medicine. As an emerging seed cell type widely used in skin wound healing and plastic surgery, HF-MSCs show considerable prospects in the treatment of LC due to their proliferation and multidirectional differentiation capabilities. We established an LC model in C57BL/6J mice by administering carbon tetrachloride (CCl₄) and injected HF-MSCs through the tail vein to explore the therapeutic effects and potential mechanisms of HF-MSCs on LC. Here, we found that HF-MSCs improved liver function and ameliorated the liver pathology of LC. Notably, PKH67-labeled HF-MSCs were detected in the injured liver and expressed the hepatocyte-specific markers cytokeratin 18 (CK18) and albumin (ALB). In addition, in contrast to that in the LC group, the α-SMA expression showed a decreasing trend in the treatment group in vitro and in vivo, indicating that the pathological activation of hepatic stellate cells (HSCs) was inhibited by HF-MSC treatment. Moreover, the levels of transforming growth factor β (TGF-β1) and p-Smad3, a signaling molecule downstream of TGF-β1, were increased in mice with LC, while HF-MSC treatment reversed these changes in vivo and in vitro. Based on these findings, HF-MSCs may reverse LC by blocking the TGF-β/Smad pathway and inhibiting the pathological activation of HSCs, which may provide evidence for the application of HF-MSCs to treat LC.

Immunomodulatory Effect of Lycium barbarum Polysaccharides against Liver Fibrosis Based on the Intelligent Medical Internet of Things

Lycium barbarum polysaccharide (LBP) is the main active component of Lycium barbarum and has many beneficial effects, including neuroprotection, antiaging, and antioxidation. This study mainly explores the immunomodulatory effect of Lycium barbarum polysaccharides against liver fibrosis based on the intelligent medical Internet of Things. This measure emphasizes that the current effective methods and methods for the treatment of liver cancer are mainly combined treatments of Western medicine and Chinese medicine. These treatments have a certain effect in preventing liver cancer, reducing recurrence, and reducing side effects. Among them, chemotherapy has unique advantages in improving the quality of life and prolonging survival. With the development of medical science and technology, the clinical efficacy and efficacy of traditional Chinese medicine in the treatment of liver cancer are constantly improving. The mechanism is also studied from many aspects. The treatment time of LBPs on fibrotic hepatocytes was set to 24 h. Take liver fiber cells in logarithmic growth phase and incubate them at 37°C for 24 h. The whole process uses a temperature sensor for intelligent temperature control. In the experiment, groups of LBPs with different concentrations and different molecular weight ranges were set up and each group had 6 multiple holes. The original medium was aspirated and replaced with a medium containing different concentrations of LBPs (12.5, 25, 50, 100, and 200 μg/mL) and cultured for 24 h. Based on the previous research, this study used in vitro cell experiments, microscopic observation, and MTT method to verify whether Lycium barbarum polysaccharides inhibit the proliferation of human liver cancer cells in vitro and whether they cooperate with the chemotherapy drug fluorouracil to play a tumor-killing effect. Animal experiments, using ELISA, HE staining, and other methods, explore the molecular and immunological mechanisms of LBP's antiliver cancer effect from the perspective of Th/Th2 differentiation balance and DC function, in order to provide experimental evidence for Chinese medicine polysaccharides in cancer immunotherapy and application. At different LBP concentrations (0 μmol/L, 5 μmol/L, 10 μmol/L, and 15 μmol/L), the inhibition rates were 0.80%, 20.06%, 35.44%, and 55.39%, respectively. This study provides a new method for large-scale expansion of hepatocytes in vitro, laying a stronger foundation for biological treatment of liver fibrosis.

Therapeutic effects of CXCL9-overexpressing human umbilical cord mesenchymal stem cells on liver fibrosis in rats

Umbilical cord mesenchymal stem cells (UC-MSCs) transplantation has become a promising treatment for liver fibrosis. However, UC-MSCs have limited anti-fibrosis ability, and their homing ability of UC-MSCs to the injured liver seems to be poor. In our study, we aimed to determine if the CXCL9-overexpressing UC-MSCs could have synergistic anti-fibrosis effects and whether it can promote the homing ability of UC-MSCs. Overexpression of CXCL9 in UC-MSCs (CXCL9-UC-MSCs) was attained by transfecting the lenti-CXCL9-mCherry to naive UC-MSCs. The therapeutic effect of transducted CXCL9-UC-MSCs on both repairing of hepatic fibrosis and target homing were evaluated by comparing with the control of UC-MSCs transfected with empty lenti-mCherry vector. The results revealed that the liver function of CXCL9-UC-MSCs treated group was significantly improved when compared with that of control UC-MSCs (P < 0.05), and the histopathology indicated an obvious decrease of the collagen fiber content and significant disappearing of pseudo-lobules with basically normal morphology of hepatic lobules. Furthermore, liver frozen sections confirmed that CXCL9-UC-MSCs have significantly stronger chemotaxis and stable persistence in the injured liver tissues. In summary, overexpression of CXCL9 could improve the efficacy of UC-MSCs therapy for liver fibrosis repairing on account of an enhanced ability of UC-MSCs in homing to and staying in the injured sites of liver fibrosis in rat models.

A novel minimally invasive OFM technique with orthotopic transplantation of hUC-MSCs and in vivo monitoring of liver metabolic microenvironment in liver fibrosis treatment

Background

Mesenchymal stromal cells (MSCs) transplantation showed promising therapeutic results in liver fibrosis. However, efficient cell delivery method is urgently needed and the therapeutic mechanism remains unclear. This study focused on developing a minimally invasive open-flow microperfusion (OFM) technique, which combined orthotopic transplantation of human umbilical cord-derived (hUC)-MSCs to liver and in vivo monitoring of liver microenvironment in mice with CCl₄-induced liver fibrosis.

Methods

The therapeutic potential of OFM route was evaluated by comparing OFM with intravenous (IV) injection route in terms of hUC-MSCs engraftment at the fibrosis liver, liver histopathological features, liver function and fibrotic markers expression after hUC-MSCs administration. OFM was also applied to sample liver interstitial fluid in vivo, and subsequent metabolomic analysis was performed to investigate metabolic changes in liver microenvironment.

Results

Compared with IV route, OFM route caused more hUC-MSCs accumulation in the liver and was more effective in improving the remodeling of liver structure and reducing collagen deposition in fibrotic liver. OFM transplantation of hUC-MSCs reduced blood ALT, AST, ALP and TBIL levels and increased ALB levels, to a greater extent than IV route. And OFM route appeared to have a more pronounced effect on ameliorating the CCl₄-induced up-regulation of the fibrotic markers, such as α-SMA, collagen I and TGF-β. In vivo monitoring of liver microenvironment demonstrated the metabolic perturbations induced by pathological condition and treatment intervention. Two metabolites and eight metabolic pathways, which were most likely to be associated with the liver fibrosis progression, were regulated by hUC-MSCs administration.

Conclusion

The results demonstrated that the novel OFM technique would be useful for hUC-MSCs transplantation in liver fibrosis treatment and for monitoring of the liver metabolic microenvironment to explore the underlying therapeutic mechanisms.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02599-w.

Current understanding of mesenchymal stem cells in liver diseases

Liver diseases caused by various factors have become a significant threat to public health worldwide. Liver transplantation has been considered as the only effective treatment for end-stage liver diseases; however, it is limited by the shortage of donor organs, postoperative complications, long-term immunosuppression, and high cost of treatment. Thus, it is not available for all patients. Recently, mesenchymal stem cells (MSCs) transplantation has been extensively explored for repairing hepatic injury in various liver diseases. MSCs are multipotent adult progenitor cells originated from the embryonic mesoderm, and can be found in mesenchymal tissues including the bone marrow, umbilical cord blood, adipose tissue, liver, lung, and others. Although the precise mechanisms of MSC transplantation remain mysterious, MSCs have been demonstrated to be able to prevent the progression of liver injury and improve liver function. MSCs can self-renew by dividing, migrating to injury sites and differentiating into multiple cell types including hepatocytes. Additionally, MSCs have immune-modulatory properties and release paracrine soluble factors. Indeed, the safety and effectiveness of MSC therapy for liver diseases have been demonstrated in animals. However, pre-clinical and clinical trials are largely required to confirm its safety and efficacy before large scale clinical application. In this review, we will explore the molecular mechanisms underlying therapeutic effects of MSCs on liver diseases. We also summarize clinical advances in MSC-based therapies.

Human umbilical cord-derived mesenchymal stem cells improve the function of liver in rats with acute-on-chronic liver failure via downregulating Notch and Stat1/Stat3 signaling

BACKGROUND

Effective treatments for acute-on-chronic liver failure (ACLF) are lacking. Human umbilical cord-derived mesenchymal stem cells (hUC-MSCs) have been applied in tissue regeneration and repair, acting through paracrine effects, cell fusion, and actual transdifferentiation. The present study was designed to investigate the therapeutic potential of hUC-MSCs in acute-on-chronic liver injury (ACLI) and ACLF rat models.

METHODS

Wistar rats aged 6 weeks were intraperitoneally administered porcine serum (PS) at a dose of 0.5 mL twice per week for 11 weeks to generate an immune liver fibrosis model. After 11 weeks, rats with immune liver fibrosis were injected intravenously with lipopolysaccharide (LPS) to induce an ACLI model or combined LPS and D-galactosamine (D-GalN) to induce an ACLF model. The rats with ACLI or ACLF were injected intravenously with 2×106 hUC-MSCs, 4×106 hUC-MSCs, or 0.9% sodium chloride as a control. The rats were sacrificed at 1, 2, 4, and 6 weeks (ACLI rats) or 4, 12, and 24 h (ACLF rats). The blood and liver tissues were collected for biochemical and histological investigation.

RESULTS

The application of hUC-MSCs in rats with ACLI and ACLF led to a significant decrease in the serum levels of ALT, AST, TBil, DBil, ALP, ammonia, and PT, with ALB gradually returned to normal levels. Inflammatory cell infiltration and collagen fiber deposition in liver tissues were significantly attenuated in ACLI rats that received hUC-MSCs. Inflammatory cell infiltration and apoptosis in liver tissues of ACLF rats that received hUC-MSCs were significantly attenuated. Compared with those in the rats that received 0.9% sodium chloride, a significant reduction in proinflammatory cytokine levels and elevated serum levels of hepatocyte growth factor (HGF) were found in ACLF rats that received hUC-MSCs. Furthermore, Notch, IFN-γ/Stat1, and IL-6/Stat3 signaling were inhibited in ACLI/ACLF rats that received hUC-MSCs.

CONCLUSIONS

hUC-MSC transplantation can improve liver function, the degree of fibrosis, and liver damage and promote liver repair in rats with ACLI or ACLF, mediated most likely by inhibiting Notch signaling and reversing the imbalance of the Stat1/Stat3 pathway.

The Application of Mesenchymal Stem Cells in the Treatment of Liver Diseases: Mechanism, Efficacy, and Safety Issues

Mesenchymal stem cell (MSC) transplantation is a novel treatment for liver diseases due to the roles of MSCs in regeneration, fibrosis inhibition and immune regulation. However, the mechanisms are still not completely understood. Despite the significant efficacy of MSC therapy in animal models and preliminary clinical trials, issues remain. The efficacy and safety of MSC-based therapy in the treatment of liver diseases remains a challenging issue that requires more investigation. This article reviews recent studies on the mechanisms of MSCs in liver diseases and the associated challenges and suggests potential future applications.

Exosomes from Placenta-Derived Mesenchymal Stem Cells Are Involved in Liver Regeneration in Hepatic Failure Induced by Bile Duct Ligation

Although the liver has a regenerative capacity, hepatic failure is a severe and irreversible chronic disease. Placenta-derived mesenchymal stem cells (PD-MSCs) have distinctive features, such as recycling of the placenta waste after birth, ease of accessibility, abundant cell numbers, and strong immunosuppressive properties. Previously, we reported that PD-MSCs can regenerate the liver in hepatic failure through antifibrotic and autophagic mechanisms. Many reports have investigated whether exosomes, which are formed by the budding of vesicular bodies and are emitted into the blood, from stem cells have therapeutic potential in various diseases. C-reactive protein (CRP) is produced in hepatocytes and secreted via vessels. Therefore, the objectives of this study were to compare the expression of CRP in exosomes of a hepatic failure rat model (bile duct ligation, BDL) and to evaluate the therapeutic effect by their correlation between CRP and angiogenesis depending on PD-MSC transplantation. The exosomes were analyzed in a BDL rat model with transplantation of PD-MSCs through LC-MS analysis and precipitation solution. The exosomes, CRP, and factors related to these molecules were evaluated and quantified in exosomes as well as investigated by real-time PCR, Western blot, and immunofluorescence (IF) in vivo and in vitro. CRP was present in exosomes from serum of a rat model and increased by PD-MSC transplantation. In the exosomes, CRP upregulated the factors related to the Wnt signaling pathway and angiogenesis in the BDL rat liver-transplanted PD-MSCs. Also, CRP regulated the Wnt pathway and vascularization in rat hepatocytes by interacting with endothelial cells. Therefore, our findings indicate that CRP in exosomes excreted by PD-MSCs functions in angiogenesis via the Wnt signaling pathway.

Quantification of the CM-Dil-labeled human umbilical cord mesenchymal stem cells migrated to the dual injured uterus in SD rat

Background

Human umbilical cord mesenchymal stem cell (hUC-MSC) therapy is considered as a promising approach in the treatment of intrauterine adhesions (IUAs). Considerable researches have already detected hUC-MSCs by diverse methods. This paper aims at exploring the quantitative distribution of CM-Dil-labeled hUC-MSCs in different regions of the uterus tissue of the dual injury-induced IUAs in rats and the underlying mechanism of restoration of fertility after implantation of hUC-MSCs in the IUA model.

Methods

In this study, we investigated the quantification of the CM-Dil-labeled hUC-MSCs migrated to the dual injured uterus in Sprague Dawley rats. Additionally, we investigated the differentiation of CM-Dil-labeled hUC-MSCs. The differentiation potential of epithelial cells, vascular endothelial cells, and estrogen receptor (ER) cells were assessed by an immunofluorescence method using CK7, CD31, and ERα. The therapeutic impact of hUC-MSCs in the IUA model was assessed by hematoxylin and eosin, Masson, immunohistochemistry staining, and reproductive function test. Finally, the expression of TGF-β1/Smad3 pathway in uterine tissues was determined by qRT-PCR and Western blotting.

Results

The CM-Dil-labeled cells in the stroma region were significantly higher than those in the superficial myometrium (SM) (71.67 ± 7.98 vs. 60.92 ± 3.96, p = 0.005), in the seroma (71.67 ± 7.98 vs. 23.67 ± 8.08, p = 0.000) and in the epithelium (71.67 ± 7.98 vs. 4.17 ± 1.19, p = 0.000). From the 2nd week of treatment, hUC-MSCs began to differentiate into epithelial cells, vascular endothelial cells, and ER cells. The therapeutic group treated with hUC-MSCs exhibited a significant decrease in fibrosis (TGF-β1/Smad3) as well as a significant increase in vascularization (CD31) compared with the untreated rats.

Conclusion

Our findings suggested that the distribution of the migrated hUC-MSCs in different regions of the uterine tissue was unequal. Most cells were in the stroma and less were in the epithelium of endometrium and gland. Injected hUC-MSCs had a capacity to differentiate into epithelial cells, vascular endothelial cells, and ER cells; increase blood supply; inhibit fibration; and then restore the fertility of the IUA model.

Effects of Extracellular Vesicles Derived from Mesenchymal Stem/Stromal Cells on Liver Diseases

Therapeutic effects of Mesenchymal Stem/Stromal Cells (MSCs) transplantation have been observed in various disease models. However, it is thought that MSCs-mediated effects largely depend on the paracrine manner of secreting cytokines, growth factors, and Extracellular Vesicles (EVs). Similarly, MSCs-derived EVs also showed therapeutic benefits in various liver diseases through alleviating fibrosis, improving regeneration of hepatocytes, and regulating immune activity. This review provides an overview of the MSCs, their EVs, and their therapeutic potential in treating various liver diseases including liver fibrosis, acute and chronic liver injury, and Hepatocellular Carcinoma (HCC). More specifically, the mechanisms by which MSC-EVs induce therapeutic benefits in liver diseases will be covered. In addition, comparisons between MSCs and their EVs were also evaluated as regenerative medicine against liver diseases. While the mechanisms of action and clinical efficacy must continue to be evaluated and verified, MSCs-derived EVs currently show tremendous potential and promise as a regenerative medicine treatment for liver disease in the future.

MSCs helped reduce scarring in the cornea after fungal infection when combined with anti-fungal treatment

Background

Fungal Keratitis (FK) is an infective keratopathy with extremely high blindness rate. The damaging effect of this disease is not only the destruction of corneal tissue during fungal infection, but also the cornea scar formed during the healing period after infection control, which can also seriously affect a patient’s vision. The purpose of the study was to observe the effect of umbilical cord mesenchymal stem cells (uMSCs) on corneal scar formation in FK.

Methods

The FK mouse model was made according to a previously reported method. Natamycin eye drops were used for antifungal treatment 24 h after modeling. There are four groups involved in the study, including control group, FK group, vehicle^inj FK group and uMSCs^inj FK group. Mice in uMSCs^inj FK group received repeated subconjunctival injections of uMSCs for 3 times at the 1d, 4d and 7d after FK modeling. At 14d, 21d and 28d after trauma, clinical observation, histological examination, second harmonic generation and molecular assays were performed.

Results

The uMSCs topical administration reduced corneal scar formation area and corneal opacity, accompanying with decreased corneal thickness and inflammatory cell infiltration, following down-regulated fibrotic-related factors α-SMA, TGFβ1, CTGF, and COLI and finally inhibited phosphorylation of TGFβ1/Smad2 signaling pathway during FK corneal fibrosis.

Conclusion

The results confirmed that uMSCs can improve corneal opacity during the scar formation stage of FK, and exert anti-inflammatory and anti-fibrotic effects.

Human umbilical cord mesenchymal stem cells ameliorate liver fibrosis in vitro and in vivo: From biological characteristics to therapeutic mechanisms

Liver fibrosis is a wound-healing response to chronic injuries, characterized by the excessive accumulation of extracellular matrix or scar tissue within the liver; in addition, its formation is associated with multiple cytokines as well as several cell types and a variety of signaling pathways. When liver fibrosis is not well controlled, it can progress to liver cirrhosis, but it is reversible in principle. Thus far, no efficient therapy is available for treatment of liver fibrosis. Although liver transplantation is the preferred strategy, there are many challenges remaining in this approach, such as shortage of donor organs, immunological rejection, and surgical complications. Hence, there is a great need for an alternative therapeutic strategy. Currently, mesenchymal stem cell (MSC) therapy is considered a promising therapeutic strategy for the treatment of liver fibrosis; advantageously, the characteristics of MSCs are continuous self-renewal, proliferation, multipotent differentiation, and immunomodulatory activities. The human umbilical cord-derived (hUC)-MSCs possess not only the common attributes of MSCs but also more stable biological characteristics, relatively easy accessibility, abundant source, and no ethical issues (e.g., bone marrow being the adult source), making hUC-MSCs a good choice for treatment of liver fibrosis. In this review, we summarize the biological characteristics of hUC-MSCs and their paracrine effects, exerted by secretion of various cytokines, which ultimately promote liver repair through several signaling pathways. Additionally, we discuss the capacity of hUC-MSCs to differentiate into hepatocyte-like cells for compensating the function of existing hepatocytes, which may aid in amelioration of liver fibrosis. Finally, we discuss the current status of the research field and its future prospects.

Mesenchymal stem cells prolong the survival of orthotopic liver transplants by regulating the expression of TGF-β1

BACKGROUND/AIMS

Recent studies have shown that transforming growth factor-β1 (TGF-β1) is prominently associated with acute rejection. This study aimed to explore the role of mesenchymal stem cells (MSCs) in the maintenance of the long-term survival of orthotopic liver transplants (OLTs) via the regulation of TGF-β1 in an experimental rat model.

MATERIALS AND METHODS

We used Lewis rats as donors and ACI rats as recipients. Hematoxylin and eosin staining was performed to evaluate histomorphological changes, and Western blot was performed to measure protein expression.

RESULTS

The expression of TGF-β1 in the liver allografts and spleen and protein levels of forkhead box P3 (FoxP3), interleukin-10 (IL-10), and cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) were measured using Western blot. The suppressive capacity of CD4+CD25+ regulatory T cells was evaluated using the MTT assay. Cell-mediated immunotoxicity was evaluated using the mixed lymphocyte reaction of CD4+ T cells and cytotoxic T lymphocyte (CTL) assay of CD8+ T cells. The results showed that MSCs prolonged the survival of the OLT mice by regulating the expression of TGF-β1 at different time points. The administration of MSCs promoted a prolonged survival in the ACI recipients (105±6.6 d) compared with the MSC-untreated recipients (16.2±4.0 d). On the postoperative day (POD) 7, the MSC-treated recipients showed a significantly higher expression of TGF-β1, FoxP3, IL-10, and CTLA-4 than the MSC-untreated recipients. However, on POD 100, the MSC-treated recipients showed a lower expression of TGF-β1 and FOxP3 than that on POD 7. Moreover, on POD 7, CD4+CD25+ regulatory T cells extracted from the MSC-treated recipients showed a higher expression of FoxP3, IL-10, CTLA-4, and suppressive capacity. On POD 7, CD4+ T cells from the MSC-treated recipients showed more significantly diminished proliferative functions than the MSC-untreated recipients; further, a reduced allospecific CTL activity of CD8+ T cells was observed in the MSC-treated recipients.

CONCLUSION

MSCs may represent a promising cell therapeutic approach for inducing immunosuppression or transplant tolerance.

Strategies to improve the efficiency of mesenchymal stem cell transplantation for reversal of liver fibrosis

End‐stage liver fibrosis frequently progresses to portal vein thrombosis, formation of oesophageal varices, hepatic encephalopathy, ascites, hepatocellular carcinoma and liver failure. Mesenchymal stem cells (MSCs), when transplanted in vivo, migrate into fibrogenic livers and then differentiate into hepatocyte‐like cells or fuse with hepatocytes to protect liver function. Moreover, they can produce various growth factors and cytokines with anti‐inflammatory effects to reverse the fibrotic state of the liver. In addition, only a small number of MSCs migrate to the injured tissue after cell transplantation; consequently, multiple studies have investigated effective strategies to improve the survival rate and activity of MSCs for the treatment of liver fibrosis. In this review, we intend to arrange and analyse the current evidence related to MSC transplantation in liver fibrosis, to summarize the detailed mechanisms of MSC transplantation for the reversal of liver fibrosis and to discuss new strategies for this treatment. Finally, and most importantly, we will identify the current problems with MSC‐based therapies to repair liver fibrosis that must be addressed in order to develop safer and more effective routes for MSC transplantation. In this way, it will soon be possible to significantly improve the therapeutic effects of MSC transplantation for liver regeneration, as well as enhance the quality of life and prolong the survival time of patients with liver fibrosis.

More than a syllable in fib-ROS-is: The role of ROS on the fibrotic extracellular matrix and on cellular contacts

Fibrosis is characterized by excess deposition of extracellular matrix (ECM). However, the ECM changes during fibrosis not only quantitatively but also qualitatively. Thus, the composition is altered as the expression of various ECM proteins changes. Moreover, also posttranslational modifications, secretion, deposition and crosslinkage as well as the proteolytic degradation of ECM components run differently during fibrosis. As several of these processes involve redox reactions and some of them are even redox-regulated, reactive oxygen species (ROS) influence fibrotic diseases. Redox regulation of the ECM has not been studied intensively, although evidences exist that the alteration of the ECM, including the redox-relevant processes of its formation and degradation, may be of key importance not only as a cause but also as a consequence of fibrotic diseases. Myofibroblasts, which have differentiated from fibroblasts during fibrosis, produce most of the ECM components and in return obtain important environmental cues of the ECM, including their redox-dependent fibrotic alterations. Thus, myofibroblast differentiation and fibrotic changes of the ECM are interdependent processes and linked with each other via cell-matrix contacts, which are mediated by integrins and other cell adhesion molecules. These cell-matrix contacts are also regulated by redox processes and by ROS. However, most of the redox-catalyzing enzymes are localized within cells. Little is known about redox-regulating enzymes, especially the ones that control the formation and cleavage of redox-sensitive disulfide bridges within the extracellular space. They are also important players in the redox-regulative crosstalk between ECM and cells during fibrosis.