Adipose tissue-derived stem cells promote the reversion of non-alcoholic fatty liver disease: An in vivo study

Current perspectives on mesenchymal stem cells as a potential therapeutic strategy for non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) has emerged as a significant health challenge, characterized by its widespread prevalence, intricate natural progression and multifaceted pathogenesis. Although NAFLD initially presents as benign fat accumulation, it may progress to steatosis, non-alcoholic steatohepatitis, cirrhosis, and hepatocellular carcinoma. Mesenchymal stem cells (MSCs) are recognized for their intrinsic self-renewal, superior biocompatibility, and minimal immunogenicity, positioning them as a therapeutic innovation for liver diseases. Therefore, this review aims to elucidate the potential roles of MSCs in alleviating the progression of NAFLD by alteration of underlying molecular pathways, including glycolipid metabolism, inflammation, oxidative stress, endoplasmic reticulum stress, and fibrosis. The insights are expected to provide further understanding of the potential of MSCs in NAFLD therapeutics, and support the development of MSC-based therapy in the treatment of NAFLD.

A multi-modality imaging strategy to determine the multiple in vivo fates of human umbilical cord mesenchymal stem cells at different periods of acute liver injury treatment

Human umbilical cord mesenchymal stem cells (HUCMSCs) are applied for disease therapy as a new type of drug in many countries. Their effects are not only presented by live cells, but also apoptotic bodies or cell fragments of dead cells. Therefore, it is meaningful to determine the multiple fates of HUCMSCs in vivo. Although various probes combining different imaging modalities have been developed to label and trace transplanted HUCMSCs in vivo, the status of the cells (live, dead, or apoptotic) was not distinguished, and a thorough understanding of the multiple fates of HUCMSCs after transplantation in vivo is lacking. Therefore, a magnetic resonance (MR)/near infrared fluorescent (NIRF)/bioluminescence (BI) multi-modality imaging strategy was developed. Iron oxide nanoparticles (IONPs) were assembled into 100 nm nanoparticles using epigallocatechin gallate as a chemical linker to increase the MR signal and reduce the exocytosis of IONPs for direct cell labeling and longitudinal MR imaging tracking. Fluorescent probes for apoptosis (DEVD-Cy-OH) were also loaded in the above assemblies to monitor the cell status. Meanwhile, the cell surface was labeled with the fluorescent dye Cy7 via bioorthogonal reactions to visualize the NIRF signal. Luciferase was lentivirally transfected into live cells to generate bioluminescence. Such labeling did not affect either the viability, proliferation, migration, differentiation characteristics of HUCMSCs or their therapeutic effects on acute liver injury mice in vivo. The in vivo fates of HUCMSCs were monitored via MR/NIRF/BI multi-modality imaging in acute liver injury mice. Although MR and Cy7 signals aggregated in injured liver for 7 days, the BI signals persisted for less than 24 hours. There was an increase in DEVD-Cy-OH signals in the injured liver, but they were almost at the basal level. That means that HUCMSCs survive in mice for a short time, and the dead form of HUCMSCs accumulated in a large quantity and sustained for a long time, which might contribute to their therapeutic effect.

RabGAP AS160/TBC1D4 deficiency increases long-chain fatty acid transport but has little additional effect on obesity and metabolic syndrome in ADMSCs-derived adipocytes of morbidly obese women

The Akt substrate of 160 kDa (AS160), also known as TBC1 domain family member 4 (TBC1D4), represents a crucial regulator of insulin-stimulated glucose uptake in skeletal muscle and adipose tissue. Recent evidence suggests that AS160/TBC1D4 may also control the cellular entry of long-chain fatty acids (LCFAs), resulting in changes to the lipid profile of muscles and fat cells in lean subjects. However, there are virtually no data on AS160/TBC1D4 expression and its modulatory role in lipid metabolism in the adipocytes from morbidly obese individuals of different metabolic status. In this study, we evaluated the effect of the three main factors, i.e., AS160 silencing, obesity, and metabolic syndrome on lipid uptake and profile in fully differentiated adipocytes derived from mesenchymal stem cells (ADMSCs) of lean and obese (with/without metabolic syndrome) postmenopausal women. Additionally, we tested possible interactions between the explanatory variables. In general, obesity translated into a greater content of fatty acid transporters (especially CD36/SR-B2 and SLC27A4/FATP4) and boosted accumulation of all the examined lipid fractions, i.e., triacylglycerols (TAGs), diacylglycerols (DAGs), and free fatty acids (FFAs). The aforementioned were further enhanced by metabolic syndrome. Moreover, AS160 deficiency also increased the abundance of SLC27A4/FATP4 and CD36/SR-B2, especially on the cell surface of the adipocytes derived from ADMSCs of subcutaneous deposit. This was further accompanied by increased LCFA (palmitic acid) uptake. Despite the aforementioned, AS160 silencing seemed unable to significantly affect the phenotype of the adipocytes stemming from obese patients with respect to their cellular lipid profile as we observed virtually no changes in TAG, DAG, and FFA contents when compared to cells with the reference level of proteins. Nevertheless, knockdown of AS160 stimulated fatty acid oxidation, which may indicate that adaptive mechanisms counteract excessive lipid accumulation. At the same time, adipocytes of visceral origin were rather insensitive to the applied intervention.

Dietary Methionine Restriction Promotes Fat Browning and Attenuates Hepatic Lipid Accumulation in High-Choline-Fed Mice Associated with the Improvement of Thyroid Function

This study aims to explore the influences of a methionine-restricted diet (MRD) on fat browning and hepatic lipid accumulation in mice fed with a high-choline diet (HCD) and their possible mechanisms. ICR mice were randomly divided into three groups and fed with a normal diet (0.86% methionine + 0.20% choline, ND), HCD (0.86% methionine + 1.20% choline), or MRD (0.17% methionine + 1.20% choline) for 90 consecutive days. We found that MRD reduced body weight and fat mass; increased heat production and ambulatory locomotor activity; reduced hepatic and plasma lipid levels, hepatic fatty infiltration area, and adipocyte volume in white and brown adipose tissue; promoted fat browning, especially upregulated gene and protein expression levels of uncoupling protein 1 (UCP1); and promoted fat catabolism and inhibited fat anabolism in the liver and adipose tissue. Moreover, MRD increased antioxidant defenses and reduced inflammatory cytokine levels in the thyroid, blood, and liver. Furthermore, MRD improved thyroid morphological structure, promoted the synthesis and secretion of thyroid hormones, and enhanced the actions of thyroid hormones on its receptor organs (liver and adipose tissue). These findings suggested that MRD promoted fat browning and attenuated hepatic lipid accumulation in HCD mice associated with the improvement of thyroid function.

Recent Advances in Adipose Tissue Dysfunction and Its Role in the Pathogenesis of Non-Alcoholic Fatty Liver Disease

Obesity is a serious ongoing health problem that significantly increases the incidence of nonalcoholic fatty liver disease (NAFLD). During obesity, adipose tissue dysfunction is obvious and characterized by increased fat deposition (adiposity) and chronic low-grade inflammation. The latter has been implicated to critically promote the development and progression of NAFLD, whose advanced form non-alcoholic steatohepatitis (NASH) is considered one of the most common causes of terminal liver diseases. This review summarizes the current knowledge on obesity-related adipose dysfunction and its roles in the pathogenesis of hepatic steatosis and inflammation, as well as liver fibrosis. A better understanding of the crosstalk between adipose tissue and liver under obesity is essential for the development of new and improved preventive and/or therapeutic approaches for managing NAFLD.

Enhancing therapeutic effects and in vivo tracking of adipose tissue-derived mesenchymal stem cells for liver injury using bioorthogonal click chemistry

Adipose tissue-derived mesenchymal stem cell (ADSC)-based therapy is attractive for liver diseases, but the long-term therapeutic outcome is still far from satisfaction due to the low hepatic engraftment efficiency of ADSC transplantation. Herein, we propose a strategy based on liver sinusoidal endothelial cell (LSEC)-targeting peptide modification and near infrared (NIR) fluorescent probe labeling for enhancing LSEC-barrier-migration ability and in vivo tracking of ADSCs in a liver injury mouse model. RLTRKRGLK (RK), a LSEC-targeted peptide, and indocyanine green (ICG), a FDA approved infrared fluorescent dye, were simultaneously modified on the ADSC surface via a bioorthogonal click reaction. The equipped ADSCs not only exhibited significant binding ability towards LSEC both in vitro and in vivo, but could also be monitored by NIR imaging in vivo. In particular, the RK-modified ADSCs showed remarkable higher hepatic accumulation as compared to unmodified ADSCs, resulting in better therapeutic outcomes. Therefore, this study provides a simple and convenient method for enhancing the homing of transplanted ADSCs to injured liver accompanying with in vivo cell tracking ability, which may shed light on accelerating the clinical translation of the ADSC-based therapy for liver diseases.

Transplantation of brown adipose tissue up-regulates miR-99a to ameliorate liver metabolic disorders in diabetic mice by targeting NOX4

Nonalcoholic fatty liver disease (NAFLD), main cause of liver damage, is inextricably linked to diabetes. However, there is no specific means to improve the pathology of fatty liver in diabetic patients. Brown adipose tissue (BAT) is an important endocrine organ that secretes adipokines and microRNAs (miRNAs) involved in systemic metabolic regulation. To investigate the effects of BAT transplantation on liver lipid metabolism in diabetic mice, we transplanted BAT from male donor mice into diabetic mice induced by streptozotocin (STZ) combined with high-fat diet (HFD). At 10 weeks after transplantation, BAT transplantation significantly decreased the blood glucose and lipid, downregulated FAS, CD36, Scd1, ACCα, NOX2, NOX4, TGF-β1, FN and COL-1, up-regulated Nrf2, reversed the pathological changes of liver and increased the circulating miR-99a in diabetic mice. To verify whether circulating miR-99a improves oxidative stress by targeting inhibition of NOX4, we used 0.4mM palmitic acid (PA) to treat the LO2 cells. The expression of NOX4 protein was significantly decreased after transfection with miR-99a mimic, and increased after transfection with miR-99a inhibitor. Luciferase reporter assay confirmed that miR-99a could target NOX4 mRNA. These findings clarify the role of miR-99a and NOX4 in liver beneficial effect of BAT transplantation in diabetic mice.

Antioxidant preconditioning improves therapeutic outcomes of adipose tissue-derived mesenchymal stem cells through enhancing intrahepatic engraftment efficiency in a mouse liver fibrosis model

BACKGROUND

Although it has been preclinically suggested that adipose tissue-derived mesenchymal stem cell (ADSC)-based therapy could effectively treat chronic liver diseases, the hepatic engraftment of ADSCs is still extremely low, which severely limits their long-term efficacy for chronic liver diseases. This study was designed to investigate the impact of antioxidant preconditioning on hepatic engraftment efficiency and therapeutic outcomes of ADSC transplantation in liver fibrotic mice.

METHODS

Liver fibrosis model was established by using intraperitoneal injection of carbon tetrachloride (CCl₄) in the male C57BL/6 mice. Subsequently, the ADSCs with or without antioxidant pretreatment (including melatonin and reduced glutathione (GSH)) were administrated into fibrotic mice via tail vein injection. Afterwards, the ADSC transplantation efficiency was analyzed by ex vivo imaging, and the liver functions were assessed by biochemical analysis and histopathological examination, respectively. Additionally, a typical hydrogen peroxide (H₂O₂)-induced cell injury model was applied to mimic the cell oxidative injury to further investigate the protective effects of antioxidant preconditioning on cell migration, proliferation, and apoptosis of ADSCs.

RESULTS

Our data showed that antioxidant preconditioning could enhance the therapeutic effects of ADSCs on liver function recovery by reducing the level of AST, ALT, and TBIL, as well as the content of hepatic hydroxyproline and fibrotic area in liver tissues. Particularly, we also found that antioxidant preconditioning could enhance hepatic engraftment efficiency of ADSCs in liver fibrosis model through inhibiting oxidative injury.

CONCLUSIONS

Antioxidant preconditioning could effectively improve therapeutic effects of ADSC transplantation for liver fibrosis through enhancing intrahepatic engraftment efficiency by reducing oxidative injuries. These findings might provide a practical strategy for enhancing ADSC transplantation and therapeutic efficiency.

Melatonin prevents senescence of canine adipose-derived mesenchymal stem cells through activating NRF2 and inhibiting ER stress

Transplantation of adipose-derived mesenchymal stem cells (ADMSCs) can aid in the treatment of numerous diseases in animals. However, natural aging during in vitro expansion of ADMSCs prior to their use in transplantation restricts their beneficial effects. Melatonin is reported to exert biorhythm regulation, anti-oxidation, and anti-senescence effects in various animal and cell models. Herein, by using a senescent canine ADMSCs (cADMSCs) cell model subjected to multiple passages in vitro, we investigated the effects of melatonin on ADMSCs senescence. We found that melatonin alleviates endoplasmic reticulum stress (ERS) and cell senescence. MT1/MT2 melatonin receptor inhibitor, luzindole, diminished the mRNA expression levels and rhythm expression amplitude of Bmal1 and Nrf2 genes. Nrf2 knockdown blocked the stimulatory effects of melatonin on endoplasmic reticulum-associated degradation (ERAD)-related gene expression and its inhibitory effects on ERS-related gene expression. At the same time, the inhibitory effects of melatonin on the NF-κB signaling pathway and senescence-associated secretory phenotype (SASP) were blocked by Nrf2 knockdown in cADMSCs. Melatonin pretreatment improved the survival of cADMSCs and enhanced the beneficial effects of cADMSCs transplantation in canine acute liver injury. These results indicate that melatonin activates Nrf2 through the MT1/MT2 receptor pathway, stimulates ERAD, inhibits NF-κB and ERS, alleviates cADMSCs senescence, and improves the efficacy of transplanted cADMSCs.

Antioxidants inhibit cell senescence and preserve stemness of adipose tissue-derived stem cells by reducing ROS generation during long-term in vitro expansion

BACKGROUND

Adipose tissue-derived mesenchymal stem cells (ADSCs) are promising candidates for regenerative medicine. However, long-term in vitro passaging leads to stemness loss and cell senescence of ADSCs, resulting in failure of ADSC-based therapy.

METHODS

In this study, ADSCs were treated with low dose of antioxidants (reduced glutathione and melatonin) with anti-aging and stem cell protection properties in the in vitro passaging, and the cell functions including stem cell senescence, cell migration, cell multidirectional differentiation potential, and ROS content were carefully analyzed.

RESULTS

We found that GSH and melatonin could maintain ADSC cell functions through reducing cell senescence and promoting cell migration, as well as by preserving stemness and multidirectional differentiation potential, through inhibiting ROS generation during long-term expansion of ADSCs.

CONCLUSIONS

Our results suggested that antioxidant treatment could efficiently prevent the dysfunction and preserve cell functions of ADSCs after long-term passaging, providing a practical strategy to facilitate ADSC-based therapy.

Liver Bioengineering: Promise, Pitfalls, and Hurdles to Overcome

PURPOSE OF REVIEW

In this review, we discuss the recent advancements in liver bioengineering and cell therapy and future advancements to improve the field towards clinical applications.

RECENT FINDINGS

3D printing, hydrogel-based tissue fabrication, and the use of native decellularized liver extracellular matrix as a scaffold are used to develop whole or partial liver substitutes. The current focus is on developing a functional liver graft through achieving a non-leaky endothelium and a fully constructed bile duct. Use of cell therapy as a treatment is less invasive and less costly compared to transplantation, however, lack of readily available cell sources with low or no immunogenicity and contradicting outcomes of clinical trials are yet to be overcome.

SUMMARY

Liver bioengineering is advancing rapidly through the development of in vitro and in vivo tissue and organ models. Although there are major challenges to overcome, through optimization of the current methods and successful integration of induced pluripotent stem cells, the development of readily available, patient-specific liver substitutes can be achieved.

Effect of hydrogen-rich saline on apoptosis induced by hepatic ischemia reperfusion upon laparoscopic hepatectomy in miniature pigs

Hepatic ischemia reperfusion injury (HIRI) occurs commonly in liver surgery and liver transplantation. Hydrogen, a safe and effective antioxidant, exerts a protective effect against liver injury. In this study, we investigated the role of hydrogen-rich saline (HRS) in apoptosis in a miniature pig model of laparoscopic HIRI upon hepatectomy. Bama miniature pigs were randomly assigned to sham, I/R and HRS groups. The pigs received 10 mL/kg HRS by portal venous injection 10 min before reperfusion and at 1 d, 2 d, and 3 d after surgery. The results showed that HRS treatment significantly decreased serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST) and total bilirubin (TBIL) activity and TUNEL-positive cells. Upon HRS treatment, the expression of P53 and Bax mRNA and protein by RT-qPCR and Western blot was markedly decreased, whereas the expression of bcl-2 mRNA and protein was significantly increased. Moreover, Caspase-3 and Caspase-9 activities were significantly decreased upon treatment with HRS. In conclusion, the results indicate that HRS could alleviate liver injury and improve liver function via inhibiting apoptosis after laparoscopic HIRI and hepatectomy injury in miniature pigs.

Adipose tissue-derived stem cells ameliorate hyperglycemia, insulin resistance and liver fibrosis in the type 2 diabetic rats

Background

Type 2 diabetes (T2D) is closely associated with liver fibrosis, but no effective treatments are currently available. This study was designed to investigate the therapeutic effects of ADSCs on insulin resistance, hyperglycemia, and liver fibrosis on T2D rats.

Methods

We first established a T2D rat model with liver fibrosis by using the combination of a high-fat diet (HFD), low-dose streptozotocin (STZ), and carbon tetrachloride (CCl₄). Subsequently, the model rats were administrated by tail vein injection of PBS or ADSCs, respectively. Thereafter, insulin resistance and liver function were assessed by biochemical analysis, ELISA, histopathological examination, and q-PCR assay, respectively. Moreover, the molecular mechanisms of ADSCs on the effect of the TGF-β1/SMAD3 signaling pathway were further analyzed.

Results

Our data showed that ADSC transplantation significantly alleviated insulin resistance and hyperglycemia in the liver-injured T2D rats. We also found that ADSC transplantation could attenuate liver injury by improving liver function and inhibiting pathological changes of liver fibrosis, as well as through downregulation of TGF-β1 and phosphorylated SMAD3 both in vitro and in vivo.

Conclusions

These findings suggested that ADSC transplantation can ameliorate insulin resistance, hyperglycemia, and liver fibrosis via suppressing TGF-β1/SMAD3 signaling, which may provide a potential treatment strategy for liver fibrosis of T2D.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-017-0743-7) contains supplementary material, which is available to authorized users.

Administration of multipotent mesenchymal stromal cells restores liver regeneration and improves liver function in obese mice with hepatic steatosis after partial hepatectomy

Background

The liver has the remarkable capacity to regenerate in order to compensate for lost or damaged hepatic tissue. However, pre-existing pathological abnormalities, such as hepatic steatosis (HS), inhibits the endogenous regenerative process, becoming an obstacle for liver surgery and living donor transplantation.

Recent evidence indicates that multipotent mesenchymal stromal cells (MSCs) administration can improve hepatic function and increase the potential for liver regeneration in patients with liver damage. Since HS is the most common form of chronic hepatic illness, in this study we evaluated the role of MSCs in liver regeneration in an animal model of severe HS with impaired liver regeneration.

Methods

C57BL/6 mice were fed with a regular diet (normal mice) or with a high-fat diet (obese mice) to induce HS. After 30 weeks of diet exposure, 70% hepatectomy (Hpx) was performed and normal and obese mice were divided into two groups that received 5 × 10⁵ MSCs or vehicle via the tail vein immediately after Hpx.

Results

We confirmed a significant inhibition of hepatic regeneration when liver steatosis was present, while the hepatic regenerative response was promoted by infusion of MSCs. Specifically, MSC administration improved the hepatocyte proliferative response, PCNA-labeling index, DNA synthesis, liver function, and also reduced the number of apoptotic hepatocytes.

These effects may be associated to the paracrine secretion of trophic factors by MSCs and the hepatic upregulation of key cytokines and growth factors relevant for cell proliferation, which ultimately improves the survival rate of the mice.

Conclusions

MSCs represent a promising therapeutic strategy to improve liver regeneration in patients with HS as well as for increasing the number of donor organs available for transplantation.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-016-0469-y) contains supplementary material, which is available to authorized users.