Irisin Promotes Cardiac Homing of Intravenously Delivered MSCs and Protects against Ischemic Heart Injury.

Few intravenously administered mesenchymal stromal cells (MSCs) engraft to the injured myocardium, thereby limiting their therapeutic efficacy for the treatment of ischemic heart injury. Here, it is found that irisin pretreatment increases the cardiac homing of adipose tissue-derived MSCs (ADSCs) administered by single and multiple intravenous injections to mice with MI/R by more than fivefold, which subsequently increases their antiapoptotic, proangiogenic, and antifibrotic effects in rats and mice that underwent MI/R. RNA sequencing, Kyoto Encyclopedia of Genes and Genomes (KEGG) signaling pathway analysis, and loss-of-function studies identified CSF2RB as a cytokine receptor that facilitates the chemotaxis of irisin-treated ADSCs in the presence of CSF2, a chemokine that is significantly upregulated in the ischemic heart. Cardiac-specific CSF2 knockdown blocked the cardiac homing and cardioprotection abilities of intravenously injected irisin-treated ADSCs in mice subjected to MI/R. Moreover, irisin pretreatment reduced the apoptosis of hydrogen peroxide-induced ADSCs and increased the paracrine proangiogenic effect of ADSCs. ERK1/2-SOD2, and ERK1/2-ANGPTL4 are responsible for the antiapoptotic and paracrine angiogenic effects of irisin-treated ADSCs, respectively. Integrin αV/ß5 is identified as the irisin receptor in ADSCs. These results provide compelling evidence that irisin pretreatment can be an effective means to optimize intravenously delivered MSCs as therapy for ischemic heart injury.

Branched-Chain Amino Acids Exacerbate Obesity-Related Hepatic Glucose and Lipid Metabolic Disorders via Attenuating Akt2 Signaling.

Branched chain amino acids (BCAAs) are associated with the progression of obesity-related metabolic disorders, including type 2 diabetes and nonalcoholic fatty liver disease. However, whether BCAAs disrupt the homeostasis of hepatic glucose and lipid metabolism remains unknown. In this study, we observed that BCAAs supplementation significantly reduced high-fat (HF) diet-induced hepatic lipid accumulation while increasing the plasma lipid levels and promoting muscular and renal lipid accumulation. Further studies demonstrated that BCAAs supplementation significantly increased hepatic gluconeogenesis and suppressed hepatic lipogenesis in HF diet-induced obese (DIO) mice. These phenotypes resulted from severe attenuation of Akt2 signaling via mTORC1- and mTORC2-dependent pathways. BCAAs/branched-chain α-keto acids (BCKAs) chronically suppressed Akt2 activation through mTORC1 and mTORC2 signaling and promoted Akt2 ubiquitin-proteasome-dependent degradation through the mTORC2 pathway. Moreover, the E3 ligase Mul1 played an essential role in BCAAs/BCKAs-mTORC2-induced Akt2 ubiquitin-dependent degradation. We also demonstrated that BCAAs inhibited hepatic lipogenesis by blocking Akt2/SREBP1/INSIG2a signaling and increased hepatic glycogenesis by regulating Akt2/Foxo1 signaling. Collectively, these data demonstrate that in DIO mice, BCAAs supplementation resulted in serious hepatic metabolic disorder and severe liver insulin resistance: insulin failed to not only suppress gluconeogenesis but also activate lipogenesis. Intervening BCAA metabolism is a potential therapeutic target for severe insulin-resistant disease.

N-Cadherin Overexpression Mobilizes the Protective Effects of Mesenchymal Stromal Cells Against Ischemic Heart Injury Through a ß-Catenin-Dependent Manner.

RATIONALE: Mesenchymal stromal cell-based therapy is promising against ischemic heart failure. However, its efficacy is limited due to low cell retention and poor paracrine function. A transmembrane protein capable of enhancing cell-cell adhesion, N-cadherin garnered attention in the field of stem cell biology only recently. OBJECTIVE: The current study investigates whether and how N-cadherin may regulate mesenchymal stromal cells retention and cardioprotective capability against ischemic heart failure. METHODS AND RESULTS: Adult mice-derived adipose tissue-derived mesenchymal stromal cells (ADSC) were transfected with adenovirus harboring N-cadherin, T-cadherin, or control adenovirus. CM-DiI-labeled ADSC were intramyocardially injected into the infarct border zone at 3 sites immediately after myocardial infarction (MI) or myocardial ischemia/reperfusion. ADSC retention/survival, cardiomyocyte apoptosis/proliferation, capillary density, cardiac fibrosis, and cardiac function were determined. Discovery-driven/cause-effect analysis was used to determine the molecular mechanisms. Compared with ADSC transfected with adenovirus-control, N-cadherin overexpression (but not T-cadherin) markedly increased engrafted ADSC survival/retention up to 7 days post-MI. Histological analysis revealed that ADSC transfected with adenovirus-N-cadherin significantly preserved capillary density and increased cardiomyocyte proliferation and moderately reduced cardiomyocyte apoptosis 3 days post-MI. More importantly, ADSC transfected with adenovirus-N-cadherin (but not ADSC transfected with adenovirus-T-cadherin) significantly increased left ventricular ejection fraction and reduced fibrosis in both MI and myocardial ischemia/reperfusion mice. In vitro experiments demonstrated that N-cadherin overexpression promoted ADSC-cardiomyocyte adhesion and ADSC migration, enhancing their capability to increase angiogenesis and cardiomyocyte proliferation. MMP (matrix metallopeptidases)-10/13 and HGF (hepatocyte growth factor) upregulation is responsible for N-cadherin's effect upon ADSC migration and paracrine angiogenesis. N-cadherin overexpression promotes cardiomyocyte proliferation by HGF release. Mechanistically, N-cadherin overexpression significantly increased N-cadherin/ß-catenin complex formation and active ß-catenin levels in the nucleus. ß-catenin knockdown abolished N-cadherin overexpression-induced MMP-10, MMP-13, and HGF expression and blocked the cellular actions and cardioprotective effects of ADSC overexpressing N-cadherin. CONCLUSIONS: We demonstrate for the first time that N-cadherin overexpression enhances mesenchymal stromal cells-protective effects against ischemic heart failure via ß-catenin-mediated MMP-10/MMP-13/HGF expression and production, promoting ADSC/cardiomyocyte adhesion and ADSC retention.

Tailorable Hydrogel Improves Retention and Cardioprotection of Intramyocardial Transplanted Mesenchymal Stem Cells for the Treatment of Acute Myocardial Infarction in Mice.

Background Poor engraftment of intramyocardial stem cells limits their therapeutic efficiency against myocardial infarction (MI)-induced cardiac injury. Transglutaminase cross-linked Gelatin (Col-Tgel) is a tailorable collagen-based hydrogel that is becoming an excellent biomaterial scaffold for cellular delivery in vivo. Here, we tested the hypothesis that Col-Tgel increases retention of intramyocardially-injected stem cells, and thereby reduces post-MI cardiac injury. Methods and Results Adipose-derived mesenchymal stem cells (ADSCs) were co-cultured with Col-Tgel in a 3-dimensional system in vitro, and Col-Tgel encapsulated ADSCs were observed using scanning electron microscopy and confocal microscopy. Vitality, proliferation, and migration of co-cultured ADSCs were evaluated. In addition, mice were subjected to MI and were intramyocardially injected with ADSCs, Col-Tgel, or a combination thereof. ADSCs engraftment, survival, cardiac function, and fibrosis were assessed. In vitro MTT and Cell Counting Kit-8 assays demonstrated that ADSCs survive and proliferate up to 4 weeks in the Col-Tgel. In addition, MTT and transwell assays showed that ADSCs migrate outside the edge of the Col-Tgel sphere. Furthermore, when compared with ADSCs alone, Col-Tgel-encapsulated ADSCs significantly enhanced the long-term retention and cardioprotective effect of ADSCs against MI-induced cardiac injury. Conclusions In the current study, we successfully established a 3-dimensional co-culture system using ADSCs and Col-Tgel. The Col-Tgel creates a suitable microenvironment for long-term retention of ADSCs in an ischemic area, and thereby enhances their cardioprotective effects. Taken together, this study may provide an alternative biomaterial for stem cell-based therapy to treat ischemic heart diseases.

Pretreatment of Diabetic Adipose-derived Stem Cells with mitoTEMPO Reverses their Defective Proangiogenic Function in Diabetic Mice with Critical Limb Ischemia.

Adipose-derived stem cells (ADSCs) have the ability to migrate to injury sites and facilitate tissue repair by promoting angiogenesis. However, the therapeutic effect of ADSCs from patients with diabetes is impaired due to oxidative stress. Given that diabetes is a group of metabolic disorders and mitochondria are a major source of reactive oxygen species (ROS), it is possible that mitochondrial ROS plays an important role in the induction of diabetic ADSC (dADSC) dysfunction. ADSCs isolated from diabetic mice were treated with mitoTEMPO, a mitochondrial ROS scavenger, or TEMPO, a universal ROS scavenger, for three passages. The results showed that pretreatment with mitoTEMPO increased the proliferation, multidifferentiation potential, and the migration and proangiogenic capacities of dADSCs to levels similar to those of ADSCs from control mice, whereas pretreatment with TEMPO showed only minor effects. Mechanistically, mitoTEMPO pretreatment enhanced the mitochondrial antioxidant capacity of dADSCs, and knockdown of superoxide dismutase reduced the restored mitochondrial antioxidant capacity and attenuated the proangiogenic effects induced by mitoTEMPO pretreatment. In addition, mitoTEMPO pretreatment improved the survival of dADSCs in diabetic mice with critical limb ischemia, showing protective effects similar to those of control ADSCs. Pretreatment of dADSCs with mitoTEMPO decreased limb injury and improved angiogenesis in diabetic mice with critical limb ischemia. These findings suggested that short-term pretreatment of dADSCs with a mitochondrial ROS scavenger restored their normal functions, which may be an effective strategy for improving the therapeutic effects of ADSC-based therapies in patients with diabetes.