Therapeutic effect of hepatocyte growth factor-overexpressing bone marrow-derived mesenchymal stem cells on CCl4-induced hepatocirrhosis.Cell Death Dis. 2018;9:1186. [PMID: 30538216 DOI: 10.1038/s41419-018-1239-9]

Current Perspectives and Progress in Preoperative Portal Vein Embolization with Stem Cell Augmentation (PVESA)

Portal vein embolization with stem cell augmentation (PVESA) is an emerging approach for enhancing the growth of the liver segment that will remain after surgery (i.e., future liver remnant, FLR) in patients with liver cancer. Conventional portal vein embolization (PVE) aims to induce preoperative FLR growth, but it has a risk of failure in patients with underlying liver dysfunction and comorbid illnesses. PVESA combines PVE with stem cell therapy to potentially improve FLR size and function more effectively and efficiently. Various types of stem cells can help improve liver growth by secreting paracrine signals for hepatocyte growth or by transforming into hepatocytes. Mesenchymal stem cells (MSCs), unrestricted somatic stem cells, and small hepatocyte-like progenitor cells have been used to augment liver growth in preclinical animal models, while clinical studies have demonstrated the benefit of CD133 + bone marrow-derived MSCs and hematopoietic stem cells. These investigations have shown that PVESA is generally safe and enhances liver growth after PVE. However, optimizing the selection, collection, and application of stem cells remains crucial to maximize benefits and minimize risks. Additionally, advanced stem cell technologies, such as priming, genetic modification, and extracellular vesicle-based therapy, that could further enhance efficacy outcomes should be evaluated. Despite its potential, PVESA requires more investigations, particularly mechanistic studies that involve orthotopic animal models of liver cancer with concomitant liver injury as well as larger human trials.

Mesenchymal Stem Cells Accelerate Recovery of Acetic Acid-Induced Chronic Gastric Ulcer by Regulating Ekt/Akt/TRIM29 Axis

Chronic gastric ulcer (CGU), a prevalent digestive disease, has a high incidence and is seriously harmful to human health. Mesenchymal stem cells (MSCs) have been proven to have beneficial therapeutic effects in many human diseases. Here, a CGU model induced by acetic acid in mice was used to evaluate the repair effects and potential mechanism of human umbilical cord-derived MSCs (hUC-MSCs) and hUC-MSCs derived conditioned medium (hUC-MSC-CM). We found that hUC-MSCs and hUC-MSC-CM treatment significantly repaired morphological characteristics of CGU, improved proliferation and decreased apoptosis of gastric cells, and promoted the generation of new blood vessels in granulation tissues. In addition, we could detect the homing of MSCs in gastric tissue, and MSCs may differentiate into Lgr5-positive cells. As well as this, in vitro experiments showed that hUC-MSC-CM could promote cell proliferation, stimulate cell cycle progression, and reduce the incidence of apoptosis. The transcriptome of cells and the iTRAQ proteome of gastric tissues suggest that MSCs may play a therapeutic role by increasing the expression of TRIM29. Additionally, it was found that knocking down TRIM29 significantly decreased the ameliorative effects of hUC-MSC-CM on cell apoptosis. As a result of further molecular experiments, it was found that TRIM29 is capable of phosphorylating Erk/Akt in specific cell type. As a whole, it appears that hUC-MSCs can be an effective therapeutic approach for promoting gastric ulcer healing and may exert therapeutic effects in the form of paracrine and differentiation into gastric cells.

Repairing Effect of Mesenchymal Stem Cells on Lead Acetate-Induced Testicular Injury in Mice

Lead acetate can cause testicular damage in males. In this study, we assessed the repairing effects of human umbilical cord mesenchymal stem cells (MSCs) on testicular injury caused by lead acetate in mice. MSCs were injected into mice with testicular injury by intraperitoneal injection, and the organ coefficient of reproductive organs, sperm motility, hormone level and antioxidant index of mice were tested. Compared with the normal group, the coefficient of reproductive organs and sperm motility were reduced in the model group, and histopathology showed obvious testicular injury, proving successful modeling. Compared with the model group, the reproductive organ coefficient and sperm motility were improved in the experimental group, and histopathology showed that the testicular injury could be significantly improved. Sex hormone secretion tends to be normal, and the antioxidant index increased. Sequencing results showed that there were 485 upregulated genes and 172 downregulated genes between the model group and the control group, and 210 upregulated genes and 482 downregulated genes between the experimental group and the model group. Differentially expressed genes are mainly concentrated in AMP-activated protein kinase (AMPK) signaling pathway, apoptosis signaling pathway, and arginine biosynthesis signaling pathway. Overall, MSCs can significantly improve the degree of damages to mice testis caused by lead acetate and have a certain repairing effect.

Multiple Dimensions of using Mesenchymal Stem Cells for Treating Liver Diseases: From Bench to Beside

Liver diseases impose a huge burden worldwide. Although hepatocyte transplantation has long been considered as a potential strategy for treating liver diseases, its clinical implementation has created some obvious limitations. As an alternative strategy, cell therapy, particularly mesenchymal stem cell (MSC) transplantation, is widely used in treating different liver diseases, including acute liver disease, acute-on-chronic liver failure, hepatitis B/C virus, autoimmune hepatitis, nonalcoholic fatty liver disease, nonalcoholic steatohepatitis, alcoholic liver disease, liver fibrosis, liver cirrhosis, and hepatocellular carcinoma. Here, we summarize the status of MSC transplantation in treating liver diseases, focusing on the therapeutic mechanisms, including differentiation into hepatocyte-like cells, immunomodulating function with a variety of immune cells, paracrine effects via the secretion of various cytokines and extracellular vesicles, and facilitation of homing and engraftment. Some improved perspectives and current challenges are also addressed. In summary, MSCs have great potential in the treatment of liver diseases based on their multi-faceted characteristics, and more accurate mechanisms and novel therapeutic strategies stemming from MSCs will facilitate clinical practice.

Exosomes Derived from BMMSCs Mitigate the Hepatic Fibrosis via Anti-Pyroptosis Pathway in a Cirrhosis Model

Researchers increasingly report the therapeutic effect of exosomes derived from rat bone marrow mesenchymal stem cells (Exos-rBMMSC) on liver disease, while the optimal dose of Exos-rBMMSC in liver cirrhotic treatment has not been reported. In this study, we aimed to explore the efficacy and dose of Exos-rBMMSC in a hepatic cirrhosis rat model. The therapeutic effects of a low dose, medium dose and high dose of Exos-rBMMSC were assessed by liver function tests and histopathology. After four-weeks of Exos-rBMMSC therapy, pyroptosis-related expression levels in the medium dose and the high dose Exos-rBMMSC groups were significantly decreased compared to those in the liver cirrhosis group (p < 0.05). The hepatic function assay and histopathology results showed significant improvement in the medium dose and the high dose Exos-rBMMSCs groups. The localization of PKH67-labeled Exos-rBMMSC was verified microscopically, and these particles were coexpressed with the PCNA, NLRP3, GSDMD and Caspase-1. Our results demonstrated that Exos-rBMMSC accelerated hepatocyte proliferation and relieved liver fibrosis by restraining hepatocyte pyroptosis. More importantly, we confirmed that the high dose of Exos-rBMMSC may be the optimal dose for liver cirrhosis, which is conducive to the application of Exos-rBMMSC as a promising cell-free strategy.

Dialysis based-culture medium conditioning improved the generation of human induced pluripotent stem cell derived-liver organoid in a high cell density

Human pluripotent stem cell-derived liver organoids (HLOs) have recently become a promising alternative for liver regenerative therapy. To realize this application, a large amount of human-induced pluripotent stem cells (hiPSCs) derived-liver cells are required for partial liver replacement during transplantation. This method requires stepwise induction using costly growth factors to direct the hiPSCs into the hepatic lineage. Therefore, we developed a simple dialysis-based medium conditioning that fully utilized growth factors accumulation to improve hepatic differentiation of hiPSCs at a high cell density. The results demonstrated that the dialysis culture system could accumulate the four essential growth factors required in each differentiation stage: activin A, bone morphogenetic protein 4 (BMP4), hepatocyte growth factor (HGF), and oncostatin M (OSM). As a result, this low lactate culture environment allowed high-density bipotential hepatic differentiation of up to 4.5 × 10⁷ cells/mL of human liver organoids (HLOs), consisting of hiPSC derived-hepatocyte like cells (HLCs) and cholangiocyte like-cells (CLCs). The differentiated HLOs presented a better or comparable hepatic marker and hepatobiliary physiology to the one that differentiated in suspension culture with routine daily medium replacement at a lower cell density. This simple miniaturized dialysis culture system demonstrated the feasibility of cost-effective high-density hepatic differentiation with minimum growth factor usage.

A transcriptional regulatory network of HNF4α and HNF1α involved in human diseases and drug metabolism

HNF4α and HNF1α are core transcription factors involved in the development and progression of a variety of human diseases and drug metabolism. They play critical roles in maintaining the normal growth and function of multiple organs, mainly the liver, and in the metabolism of endogenous and exogenous substances. The twelve isoforms of HNF4α may exhibit different physiological functions, and HNF4α and HNF1α show varying or even opposing effects in different types of diseases, particularly cancer. Additionally, the regulation of CYP450, phase II drug-metabolizing enzymes, and drug transporters is affected by several factors. This article aims to review the role of HNF4α and HNF1α in human diseases and drug metabolism, including their structures and physiological functions, affected diseases, regulated drug metabolism genes, influencing factors, and related mechanisms. We also propose a transcriptional regulatory network of HNF4α and HNF1α that regulates the expression of target genes related to disease and drug metabolism.

Liver regeneration as treatment target for severe alcoholic hepatitis

Severe alcoholic hepatitis (AH) is a distinct entity in the spectrum of alcohol-related liver disease, with limited treatment options and high mortality. Supportive medical care with corticosteroids in selected patients is the only currently available treatment option, often with poor outcomes. Based on the insights into the pathogenetic mechanisms of AH, which are mostly obtained from animal studies, several new treatment options are being explored. Studies have implicated impaired and deranged liver regeneration processes as one of the culprit mechanisms and a potential therapeutic target. Acknowledging evidence for the beneficial effects of granulocyte colony-stimulating factor (G-CSF) on liver regeneration and immunomodulation in animal models, several human studies investigated its role in the treatment of advanced alcohol-related liver disease and AH. Contrary to the previously published studies suggesting benefits of G-CSF in the outcomes of patients with severe AH, these effects were not confirmed by a recently published multicenter randomized trial, suggesting that other options should rather be pursued. Stem cell transplantation represents another option for improving liver regeneration, but evidence for its efficacy in patients with severe AH and advanced alcohol-related liver disease is still very scarce and unconvincing, with established lack of efficacy in patients with compensated cirrhosis. In this review, we summarize the current knowledge on the pathogenesis and experimental therapies targeting liver regeneration. The lack of high-quality studies and evidence is a major obstacle in further treatment development. New insights into the pathogenesis of not only liver injury, but also liver regeneration processes are mandatory for the development of new treatment options. A reliable experimental model of the pathogenesis of AH and processes involved in liver recovery is still missing, and data obtained from animal studies are essential for future research.

Recent advances in the therapeutic efficacy of hepatocyte growth factor gene-modified mesenchymal stem cells in multiple disease settings

Mesenchymal stem cell (MSC) therapy is considered a new treatment for a wide range of diseases and injuries, but challenges remain, such as poor survival, homing and engraftment rates, thus limiting the therapeutic efficacy of the transplanted MSCs. Many strategies have been developed to enhance the therapeutic efficacy of MSCs, such as preconditioning, co-transplantation with graft materials and gene modification. Hepatocyte growth factor (HGF) is secreted by MSCs, which plays an important role in MSC therapy. It has been reported that the modification of the HGF gene is beneficial to the therapeutic efficacy of MSCs, including diseases of the heart, lung, liver, urinary system, bone and skin, lower limb ischaemia and immune-related diseases. This review focused on studies involving HGF/MSCs both in vitro and in vivo. The characteristics of HGF/MSCs were summarized, and the mechanisms of their improved therapeutic efficacy were analysed. Furthermore, some insights are provided for HGF/MSCs' clinical application based on our understanding of the HGF gene and MSC therapy.

Preconditioning with Trehalose Protects the Bone Marrow-Derived Mesenchymal Stem Cells Under Oxidative Stress and Enhances the Stem Cell-Based Therapy for Cerebral Ischemic Stroke

Bone marrow-derived mesenchymal stem cell (BMSC) transplantation has emerged as a potential treatment for ischemic stroke. Preconditioning with pharmacological agents before cell transplantation has been shown to increase the efficiency of cell therapy. In this study, trehalose (Tre), an autophagy inducer, was used as a pharmacological agent to treat BMSCs, and the neuroprotective effect of BMSCs preconditioned with Tre on cerebral ischemia was assessed. BMSCs were treated in vitro with different concentrations of Tre. Immunofluorescence staining of LC3B was performed to detect autophagy, and Western blotting for LC3, Beclin1, p-AMPK, and p-mTOR was performed. Flow cytometry and Western blotting analysis were performed to measure cell apoptosis in the presence of hydrogen peroxide (H₂O₂). Enzyme-linked immunosorbent assay was used to test the secretion levels of neurotrophic factors. An in vivo ischemia/reperfusion model was generated by middle cerebral artery occlusion in male Sprague Dawley rats, and Tre-preconditioned BMSCs were administered intralesionally 24 hours after ischemic injury. Histopathological examination and neurological function studies were conducted. In vitro, Tre promotes autophagy of BMSCs through the activation of the AMPK signal pathway. Tre protected BMSCs from H₂O₂-induced cell viability reduction and apoptosis. Moreover, Tre pretreatment increased the secretion of brain-derived neurotrophic factor, vascular endothelial growth factor, and hepatocyte growth factor. In vivo, preconditioning with Tre could further enhance the survival of BMSCs, reduce infarct size, alleviate cell apoptosis, abate vessel decrease, and ultimately improve functional recovery. Our study indicates that Tre can enhance the survival of BMSCs under oxidative stress and enhance BMSC-based treatment of ischemia/reperfusion injury.

Therapeutic Effects and Repair Mechanism of HGF Gene-Transfected Mesenchymal Stem Cells on Injured Endometrium

There are many studies on the advantages of using mesenchymal stem cells (MSCs) that secrete various paracrine factors for repairing endometrial injury. However, the stability and effectiveness of MSCs require improvement to become a viable therapy. Hepatocyte growth factor (HGF), one of the cytokines secreted by MSCs, promotes vascular repair and mesenchymal to epithelial transformation (MET). Therefore, HGF likely promotes the repair process of the endometrium. We prepared MSCs transfected with the HGF gene to explore its repair effects and mechanism using a damaged endometrium mouse model. HGF gene-transfected MSCs were prepared by electroporation. The transfected MSCs retained their cellular characteristics and significantly increased the expression of HGF ( $P<0.01$ ). HGF gene-transfected MSCs helped damaged endometrium to recover its morphological characteristics, improved proliferation and decreased apoptosis of endometrial cells, increased the expression of endometrial vascular growth-related factors, and activated phosphorylated c-Met and AKT in the mouse endometrial damage model ( $P<0.05$ ). Compared with normal MSCs, HGF gene-transfected MSCs produced a more significant effect on damaged endometrial epithelium repair by activating the HGF/c-Met and downstream signaling pathways. Our results indicate that HGF gene-transfected MSCs provide an effective and promising tool for injured endometrium therapy.

Targeting Programmed Cell Death to Improve Stem Cell Therapy: Implications for Treating Diabetes and Diabetes-Related Diseases

Stem cell therapies have shown promising therapeutic effects in restoring damaged tissue and promoting functional repair in a wide range of human diseases. Generations of insulin-producing cells and pancreatic progenitors from stem cells are potential therapeutic methods for treating diabetes and diabetes-related diseases. However, accumulated evidence has demonstrated that multiple types of programmed cell death (PCD) existed in stem cells post-transplantation and compromise their therapeutic efficiency, including apoptosis, autophagy, necroptosis, pyroptosis, and ferroptosis. Understanding the molecular mechanisms in PCD during stem cell transplantation and targeting cell death signaling pathways are vital to successful stem cell therapies. In this review, we highlight the research advances in PCD mechanisms that guide the development of multiple strategies to prevent the loss of stem cells and discuss promising implications for improving stem cell therapy in diabetes and diabetes-related diseases.

Effect of Hepatocyte Growth Factor-Transfected Human Umbilical Cord Mesenchymal Stem Cells on Hepatic Stellate Cells by Regulating Transforming Growth Factor-β1/Smads Signaling Pathway

Studies have shown that human umbilical cord mesenchymal stem cells (hUCMSCs) could ameliorate liver fibrosis (LF) through inhibiting the activation of hepatic stellate cells (HSCs). However, the specific mechanisms have not been studied clearly. The purpose of this study was to explore the possible mechanism of hepatocyte growth factor (HGF)-transfected hUCMSCs in inhibiting the proliferation and activation of HSCs-T6. The upper and lower double-cell coculture system was established among HGF-hUCMSCs, LV5-NC-hUCMSCs, hUCMSCs, and HSCs-T6 in experimental groups; HSCs-T6 were cultured alone as control group. After coculturing for 1, 2, and 3 days, results showed that HGF-transfected hUCMSCs could decrease cell viability of HSCs-T6 and promote apoptosis; inhibit their activation and reduce the expression of Collagen I, Collagen III, TGF-β1, Smad2 and Smad3, which may be related to inhibiting the activation of TGF-β1/Smads signaling pathway. These findings suggested that HGF-transfected hUCMSCs may be used as an alternative and novel therapeutic approach for the treatment of LF.

Retinal Lineage Therapeutic Specific Effect of Human Orbital and Abdominal Adipose-Derived Mesenchymal Stem Cells

Retinal degenerative diseases are one of the main causes of complete blindness in aged population. In this study, we compared the therapeutic potential for retinal degeneration of human mesenchymal stem cells derived from abdominal subcutaneous fat (ABASCs) or from orbital fat (OASCs) due to their accessibility and mutual embryonic origin with retinal tissue, respectively. OASCs were found to protect RPE cells from cell death and were demonstrated to increase early RPE precursor markers, while ABASCs showed a raise in retinal precursor marker expression. Subretinal transplantation of OASCs in a mouse model of retinal degeneration led to restoration of the RPE layer while transplantation of ABASCs resulted in a significant restoration of the photoreceptor layer. Taken together, we demonstrated a lineage-specific therapeutic effect for either OASCs or ABASCs in retinal regeneration.

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.

Dental Pulp Mesenchymal Stem Cells Attenuate Limb Ischemia via Promoting Capillary Proliferation and Collateral Development in a Preclinical Model

Critical limb ischemia (CLI), an end-stage manifestation of peripheral artery disease (PAD), still lacks effective therapeutic strategies. Recently, dental pulp-derived mesenchymal stem cells (DP-MSCs) have been attracting more and more attentions in therapeutic applications due to their high proliferation ability, powerful osteogenic differentiation potential, and effective anti-inflammatory effects. In this study, we compared the therapeutic effects of MSCs derived from different sources in a femoral artery-ligated preclinical ischemic model. We found that treatments with MSCs, including bone marrow- (BM-), adipose- (AD-), dental pulp- (DP-), and umbilical cord- (UC-) derived MSCs, improved limb functions, reduced inflammatory responses, increased angiogenesis, and promoted regeneration of muscle fiber. Among them, DP-MSCs and BM-MSCs produced much more impressive effects in restoring limb functions and promoting angiogenesis. The flow velocity restored to nearly 20% of the normal level at 3 weeks after treatments with DP-MSCs and BM-MSCs, and obvious capillary proliferation and collateral development could be observed. Although neovascularization was induced in the ischemic limb after ligation, MSCs, especially DP-MSCs, significantly enhanced the angiogenesis. In vitro experiments showed that serum deprivation improved the expression of angiogenic factors, growth factors, and chemokines in DP-MSCs and UC-MSCs, but not in BM-MSCs and AD-MSCs. However, DP-MSCs produced stronger therapeutic responses than UC-MSCs, which might be due to the higher expression of hepatocyte growth factor (HGF) and hypoxia-inducible factor-1 α (HIF-1α). We speculated that DP-MSCs might stimulate angiogenesis and promote tissue repair via expressing and secreting angiogenic factors, growth factors, and chemokines, especially HGF and HIF-1α. In conclusion, DP-MSCs might be a promising approach for treating CLI.

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.

Comparing the Therapeutic Potential of Stem Cells and their Secretory Products in Regenerative Medicine

Cell therapy involves the transplantation of human cells to replace or repair the damaged tissues and modulate the mechanisms underlying disease initiation and progression in the body. Nowadays, many different types of cell-based therapy are developed and used to treat a variety of diseases. In the past decade, cell-free therapy has emerged as a novel approach in regenerative medicine after the discovery that the transplanted cells exerted their therapeutic effect mainly through the secretion of paracrine factors. More and more evidence showed that stem cell-derived secretome, i.e., growth factors, cytokines, and extracellular vesicles, can repair the injured tissues as effectively as the cells. This finding has spurred a new idea to employ secretome in regenerative medicine. Despite that, will cell-free therapy slowly replace cell therapy in the future? Or are these two modes of treatment still needed to address different diseases and conditions? This review provides an indepth discussion about the values of stem cells and secretome in regenerative medicine. In addition, the safety, efficacy, advantages, and disadvantages of using these two modes of treatment in regenerative medicine are also critically reviewed.

Current and Emerging Approaches for Hepatic Fibrosis Treatment

Liver fibrosis resulting from chronic liver injury is a key factor to develop liver cirrhosis and risk of hepatocellular carcinoma (HCC) which are major health burden worldwide. Therefore, it is necessary for antifibrotic therapies to prevent chronic liver disease progression and HCC development. There has been tremendous progress in understanding the mechanisms of liver fibrosis in the last decade, which has created new opportunities for the treatment of this condition. In this review, we aim to make an overview on information of different potential therapies (drug treatment, cell therapy, and liver transplantation) for the liver fibrosis and hope to provide the therapeutic options available for the treatment of liver fibrosis and discuss novel approaches.

Protection of liver sinusoids by intravenous administration of human Muse cells in a rat extra-small partial liver transplantation model

Small-for-size syndrome (SFSS) has a poor prognosis due to excessive shear stress and sinusoidal microcirculatory disturbances in the acute phase after living-donor liver transplantation (LDLT). Multilineage-differentiating stress enduring (Muse) cells are reparative stem cells found in various tissues and currently under clinical trials. These cells selectively home to damaged sites via the sphingosine-1-phosphate (S1P)-S1P receptor 2 system and repair damaged tissue by pleiotropic effects, including tissue protection and damaged/apoptotic cell replacement by differentiating into tissue-constituent cells. The effects of intravenously administered human bone marrow-Muse cells and -mesenchymal stem cells (MSCs) (4 × 105 ) on liver sinusoidal endothelial cells (LSECs) were examined in a rat SFSS model without immunosuppression. Compared with MSCs, Muse cells intensively homed to the grafted liver, distributed to the sinusoids and vessels, and delivered improved blood chemistry and Ki-67(+) proliferative hepatocytes and -LSECs within 3 days. Tissue clearing and three-dimensional imaging by multiphoton laser confocal microscopy revealed maintenance of the sinusoid continuity, organization, and surface area, as well as decreased sinusoid interruption in the Muse group. Small-interfering RNA-induced knockdown of hepatocyte growth factor and vascular endothelial growth factor-A impaired the protective effect of Muse cells on LSECs. Intravenous injection of Muse cells might be a feasible approach for LDLT with less recipient burden.

Murine endometrial-derived mesenchymal stem cells suppress experimental autoimmune encephalomyelitis depending on indoleamine-2,3-dioxygenase expression

Cellular therapy with mesenchymal stem cells (MSCs) is a huge challenge for scientists, as little translational relevance has been achieved. However, many studies using MSCs have proved their suppressive and regenerative capacity. Thus, there is still a need for a better understanding of MSCs biology and the establishment of newer protocols, or to test unexplored tissue sources. Here, we demonstrate that murine endometrial-derived MSCs (meMSCs) suppress Experimental Autoimmune Encephalomyelitis (EAE). MSC-treated animals had milder disease, with a significant reduction in Th1 and Th17 lymphocytes in the lymph nodes and in the central nervous system (CNS). This was associated with increased Il27 and Cyp1a1 expression, and presence of IL-10-secreting T CD4+ cells. At EAE peak, animals had reduced CNS infiltrating cells, histopathology and demyelination. qPCR analysis evidenced the down-regulation of several pro-inflammatory genes and up-regulation of indoleamine-2,3-dioxygenase (IDO). Consistently, co-culturing of WT and IDO-/- meMSCs with T CD4+ cells evidenced the necessity of IDO on the suppression of encephalitogenic lymphocytes, and IDO-/- meMSCs were not able to suppress EAE. In addition, WT meMSCs stimulated with IL-17A and IFN-γ increased IDO expression and secretion of kynurenines in vitro, indicating a negative feedback loop. Pathogenic cytokines were increased when CD4+ T cells from AhR-/- mice were co-cultured with WT meMSC. In summary, our research evidences the suppressive activity of the unexplored meMSCs population, and shows the mechanism depends on IDO-kynurenines-Aryl hydrocarbon receptor (AhR) axis. To our knowledge this is the first report evidencing that the therapeutic potential of meMSCs relying on IDO expression.

Murine liver repair via transient activation of regenerative pathways in hepatocytes using lipid nanoparticle-complexed nucleoside-modified mRNA

Induction of intrinsic liver regeneration is an unmet need that can be achieved by temporally activating key hepatocyte regenerative pathways. Here, we establish an efficient, safe, non-integrative method to transiently express hepatocyte-growth-factor (HGF) and epidermal-growth-factor (EGF) in hepatocytes via nucleoside-modified, lipid-nanoparticle-encapsulated mRNA (mRNA-LNP) delivery in mice. We confirm specific hepatotropism of mRNA-LNP via intravenous injection of firefly luciferase encoding mRNA-LNP, with protein expression lasting about 3 days. In the liver, virtually all hepatocytes are transfected along with a subpopulation of endothelial and Kupffer cells. In homeostasis, HGF mRNA-LNP efficiently induce hepatocyte proliferation. In a chronic liver injury mouse model recapitulating non-alcoholic fatty liver disease, injections of both HGF and EGF mRNA-LNP sharply reverse steatosis and accelerate restoration of liver function. Likewise, HGF and EGF mRNA-LNP accelerate liver regeneration after acetaminophen-induced acute liver injury with rapid return to baseline ALT levels. This study introduces mRNA-LNP as a potentially translatable safe therapeutic intervention to harness liver regeneration via controlled expression of endogenous mitogens in vivo.

Applications of Mesenchymal Stem Cells in Liver Fibrosis: Novel Strategies, Mechanisms, and Clinical Practice

Liver fibrosis is a common result of most chronic liver diseases, and advanced fibrosis often leads to cirrhosis. Currently, there is no effective treatment for liver cirrhosis except liver transplantation. Therefore, it is important to carry out antifibrosis treatment to reverse liver damage in the early stage of liver fibrosis. Mesenchymal stem cells (MSCs) are the most widely used stem cells in the field of regenerative medicine. The preclinical and clinical research results of MSCs in the treatment of liver fibrosis and cirrhosis show that MSC administration is a promising treatment for liver fibrosis and cirrhosis. MSCs reverse liver fibrosis and increase liver function mainly through differentiation into hepatocytes, immune regulation, secretion of cytokines and other nutritional factors, reduction of hepatocyte apoptosis, and promotion of hepatocyte regeneration. Recently, many studies provided a variety of new methods and strategies to improve the effect of MSCs in the treatment of liver fibrosis. In this review, we summarized the current effective methods and strategies and their potential mechanisms of MSCs in the treatment of liver fibrosis, as well as the current research progress in clinical practice. We expect to achieve complete reversal of liver injury with MSC-based therapy in the future.

Tanshinone IIA exerts therapeutic effects by acting on endogenous stem cells in rats with liver cirrhosis

BACKGROUND AND OBJECTIVE

Liver cirrhosis (LC), the major pathway for the progression and development of chronic liver disease, is an advanced stage of liver disease. It is the third most common chronic noncommunicable disease after cardiovascular diseases and malignant tumors. Tanshinone IIA (Tan), an extract of Salvia miltiorrhiza (S. miltiorrhiza), has been proven to promote the proliferation and differentiation of stem cells. Moreover, its protective effect in liver injury has received widespread attention. The present study investigated whether Tan plays a therapeutic role in LC by promoting endogenous stem cell proliferation and differentiation.

MATERIALS AND METHODS

LC models were established by intraperitoneal injection of an olive oil solution containing 50 % carbon tetrachloride (CCL₄) combined with 10 % alcohol in the drinking water. After successful model establishment, the animals were randomly divided into four groups and injected with physiological saline or low-, medium-, or high-dose (10, 20, or 40 mg/kg) Tan for seven consecutive days. The protective effect of Tan on LC was observed by western blotting, serological examination and histopathological staining. Furthermore, immunofluorescence double-labeling of 5-bromo-2-deoxyuridine (BrdU) and the liver cell markers albumin and CK-18 or the liver stem cell markers EPCAM and OV-6 was used to evaluate the proliferation and differentiation of endogenous liver stem cells.

RESULTS

We confirmed successful establishment of the LC model by observing transaminase levels and hematoxylin-eosin (HE) and Masson staining of liver sections in CCL₄-treated and healthy rats. After Tan treatment, HE and Masson staining of paraffin sections of liver tissue showed that Tan treatment significantly improved histological injury to the liver. Serological tests showed that albumin-bilirubin (ALBI) scores and models for end-stage liver disease (MELD) were lower. Immunofluorescence and immunohistochemical staining showed that the newly proliferated cells were colocalized with ALB, OV-6, EPCAM, and CK-18, indicating that new expression of these markers occurred after Tan injection. All results were most significant in the medium-dose treatment group.

CONCLUSION

Tan can alleviate liver injury induced by CCL₄ combined with alcohol in rats and plays a therapeutic role in LC by promoting the proliferation and differentiation of endogenous liver stem cells.

Genetic Engineering as a Strategy to Improve the Therapeutic Efficacy of Mesenchymal Stem/Stromal Cells in Regenerative Medicine

Mesenchymal stem/stromal cells (MSCs) have been widely studied in the field of regenerative medicine for applications in the treatment of several disease settings. The therapeutic potential of MSCs has been evaluated in studies in vitro and in vivo, especially based on their anti-inflammatory and pro-regenerative action, through the secretion of soluble mediators. In many cases, however, insufficient engraftment and limited beneficial effects of MSCs indicate the need of approaches to enhance their survival, migration and therapeutic potential. Genetic engineering emerges as a means to induce the expression of different proteins and soluble factors with a wide range of applications, such as growth factors, cytokines, chemokines, transcription factors, enzymes and microRNAs. Distinct strategies have been applied to induce genetic modifications with the goal to enhance the potential of MCSs. This review aims to contribute to the update of the different genetically engineered tools employed for MSCs modification, as well as the factors investigated in different fields in which genetically engineered MSCs have been tested.

In vivo priming of human mesenchymal stem cells with hepatocyte growth factor-engineered mesenchymal stem cells promotes therapeutic potential for cardiac repair

The clinical use of human bone marrow-derived mesenchymal stem cells (BM-MSCs) has been hampered by their poor performance after transplantation into failing hearts. Here, to improve the therapeutic potential of BM-MSCs, we developed a strategy termed in vivo priming in which BM-MSCs are primed in vivo in myocardial infarction (MI)-induced hearts through genetically engineered hepatocyte growth factor-expressing MSCs (HGF-eMSCs) that are encapsulated within an epicardially implanted 3D cardiac patch. Primed BM-MSCs through HGF-eMSCs exhibited improved vasculogenic potential and cell viability, which ultimately enhanced vascular regeneration and restored cardiac function to the MI hearts. Histological analyses further demonstrated that the primed BM-MSCs survived longer within a cardiac patch and conferred cardioprotection evidenced by substantially higher numbers of viable cardiomyocytes in the MI hearts. These results provide compelling evidence that this in vivo priming strategy can be an effective means to enhance the cardiac repair of MI hearts.

Pre-treatments enhance the therapeutic effects of mesenchymal stem cells in liver diseases

Liver diseases caused by viral infection, alcohol abuse and metabolic disorders can progress to end‐stage liver failure, liver cirrhosis and liver cancer, which are a growing cause of death worldwide. Although liver transplantation and hepatocyte transplantation are useful strategies to promote liver regeneration, they are limited by scarce sources of organs and hepatocytes. Mesenchymal stem cells (MSCs) restore liver injury after hepatogenic differentiation and exert immunomodulatory, anti‐inflammatory, antifibrotic, antioxidative stress and antiapoptotic effects on liver cells in vivo. After isolation and culture in vitro, MSCs are faced with nutrient and oxygen deprivation, and external growth factors maintain MSC capacities for further applications. In addition, MSCs are placed in a harsh microenvironment, and anoikis and inflammation after transplantation in vivo significantly decrease their regenerative capacity. Pre‐treatment with chemical agents, hypoxia, an inflammatory microenvironment and gene modification can protect MSCs against injury, and pre‐treated MSCs show improved hepatogenic differentiation, homing capacity, survival and paracrine effects in vitro and in vivo in regard to attenuating liver injury. In this review, we mainly focus on pre‐treatments and the underlying mechanisms for improving the therapeutic effects of MSCs in various liver diseases. Thus, we provide evidence for the development of MSC‐based cell therapy to prevent acute or chronic liver injury. Mesenchymal stem cells have potential as a therapeutic to prolong the survival of patients with end‐stage liver diseases in the near future.

Mechanisms Underlying Cell Therapy in Liver Fibrosis: An Overview

Fibrosis is a common feature in most pathogenetic processes in the liver, and usually results from a chronic insult that depletes the regenerative capacity of hepatocytes and activates multiple inflammatory pathways, recruiting resident and circulating immune cells, endothelial cells, non-parenchymal hepatic stellate cells, and fibroblasts, which become activated and lead to excessive extracellular matrix accumulation. The ongoing development of liver fibrosis results in a clinically silent and progressive loss of hepatocyte function, demanding the constant need for liver transplantation in clinical practice, and motivating the search for other treatments as the chances of obtaining compatible viable livers become scarcer. Although initially cell therapy has emerged as a plausible alternative to organ transplantation, many factors still challenge the establishment of this technique as a main or even additional therapeutic tool. Herein, the authors discuss the most recent advances and point out the corners and some controversies over several protocols and models that have shown promising results as potential candidates for cell therapy for liver fibrosis, presenting the respective mechanisms proposed for liver regeneration in each case.

A New Insight of Kartogenin Induced the Mesenchymal Stem Cells (MSCs) Selectively Differentiate into Chondrocytes by Activating the Bone Morphogenetic Protein 7 (BMP-7)/Smad5 Pathway

Background

Rotator cuff injury is the most common cause of shoulder disability, and although the repair technique has improved, the rate of rotator cuff reduction after repair is still high. The fibrocartilage region, which appears to be histologically inserted, cannot be regenerated. In recent years, studies have reported that mesenchymal stem cells (MSCs) have enhanced cartilage regeneration in the tendon and bone interface after rotator cuff repair, which has become a hot topic of research.

Material/Methods

Two mesenchymal stem cell types, SMSC (synovial-derived mesenchymal stem cells) and BMSC (bone marrow-derived mesenchymal stem cells) were intervened using kartogenin (KGN). The cytotoxicity was evaluated and the proliferation of the 2 cells was observed. Four commonly used cartilage phenotype genes were detected by quantitative real-time polymerase chain reaction, and the cartilage differentiation of MSCs induced by KGN was explored. The bidirectional regulation of the expression of BMP-7 and the downstream gene Smad5 was observed by constructing a lentiviral overexpression vector containing the target gene BMP-7. To explore whether BMP-7/Smad5 pathway activation promotes differentiation of SMSCs into chondrocytes.

Results

KGN can induce the selective differentiation of endogenous MSCs into chondrocytes by activating the BMP-7/Smad5 pathway, which promotes the regeneration of interfacial cartilage, and improves the quality of tendon healing of the tendon after rotator cuff repair.

Conclusions

This study found a new biological intervention method to promote the effect of tendon on bone healing after rotator cuff repair.

Conditioned Medium from Human Mesenchymal Stromal Cells: Towards the Clinical Translation

Mesenchymal stem/stromal cells (MSC) remain a promising tool for regenerative medicine as the efficacy of MSC-based cell therapy has been demonstrated for a broad spectrum of indications. Their therapeutic potency is mainly associated with their ability to secrete multiple factors critical for tissue regeneration. Due to comparable effects along with superior safety MSC conditioned medium (MSC-CM) containing a complex of MSC-secreted products is considered a reasonable alternative to cell therapy. However, the lack of standards regulating bioprocessing, use of proper auxiliary materials, and quality control complicates the development of MSC secretome-based therapeutics. In this study, we suggested several approaches addressing these issues. We manufactured 36 MSC-CM samples based on different xeno-free serum-free chemically defined media (DMEM-LG or MSC NutriStem^® XF) using original protocols and considered total concentrations of regeneration-associated paracrine factors secreted by human adipose-derived MSC at each time-point of conditioning. Using regression analysis, we retrospectively predicted associations between concentrations of several components of MSC-CM and its biological activity to stimulate human dermal fibroblast and endothelial cell migration in vitro as routine examples of potency assays for cell-based products. We also demonstrated that the cell culture medium might affect MSC-CM biological activity to varying degrees depending on the potency assay type. Furthermore, we showed that regression analysis might help to overcome donor variability. The suggested approaches might be successfully applied for other cell types if their secretome was shown to be promising for application in regenerative medicine.