Aldehyde Dehydrogenase 2-mediated Stem Cell Niche Modification And Its Corresponding Strategy Of Metabolism Pre-adapation

Part 1 Host ALDH2 influences the retention and therapeutic efficacy of transplanted MSCObjective:To determine whether host ALDH2 influences transplanted MSC survival and therapy under ischemiaApproach and Results:Mice limb ischemia was performed by femoral artery ligation. A total of 106 MSCs were injected into the ischemic thigh muscles. One,2, and 4 weeks after transplantation, MSC retention, blood perfusion recovery, limb necrosis, and fibrosis were analyzed. Compared with wild-type tissue, ALDH2 deficiency tissue significantly limited MSC retention and its perfusion recovery and limb salvage effects after ischemia. Importantly, local overexpression of ALDH2 optimized tissue microenvironment and significantly magnified all these MSC-induced improvement.Conclusions:Host ALDH2 influences the retention and therapeutic efficacy of transplanted MSCPart 1 Host ALDH2 influences the retention and therapeutic efficacy of transplanted MSCObjective:To determine whether host ALDH2 influences transplanted MSC survival and therapy under ischemiaApproach and Results:Mice limb ischemia was performed by femoral artery ligation. A total of 106 MSCs were injected into the ischemic thigh muscles. One,2, and 4 weeks after transplantation, MSC retention, blood perfusion recovery, limb necrosis, and fibrosis were analyzed. Compared with wild-type tissue, ALDH2 deficiency tissue significantly limited MSC retention and its perfusion recovery and limb salvage effects after ischemia. Importantly, local overexpression of ALDH2 optimized tissue microenvironment and significantly magnified all these MSC-induced improvement.Conclusions:Host ALDH2 influences the retention and therapeutic efficacy of transplanted MSCPart 2 host ALDH2 mediates microenvironment homeostasis postischemiaObjective:To determine how host ALDH2 influences transplanted MSC survival and therapy under ischemiaApproach and Results:For microenvironment study, CD31-based capillary density, ATP-based metabolism substrate supply, anti-oxidatant activity and toxic substance accumulation were analyzed. And result indicated that host ALDH2 regulated transplanted MSC survival and therapy as a microenvironment homeostasis mediator, ALDH2 deficiency significantly inhibited local capillary density, energy supply, and oxidative stress regulating after ischemia. Overexpression of ALDH2 optimized these entire microenvironment factors.In addition, the toxic substance 4-hydroxynonenal (4-HNE) induced MSCs death via c-jun N-terminal kinase (JNK)-dependented and P53-mediated pathway.Conclusions:Our study establishes ALDH2 as a key mediator of host stem cell niche for optimal MSC therapy and suggests that ALDH2 deficiency present in the general population is a limiting host factor to be considered for MSC therapyPart 3 Hypoxia-induced glycogenesis promotes MSC survival and therapeuticefficiency in subsequent ischemiaObjective:To determine whether inducible metabolic adaptation enhances mesenchymal stem cells (MSC) survival and therapy under ischemia.Approach and Results:MSC were subjected to glycogen synthase 1-specific small interfering RNA or vehicle treatment, and then sublethal hypoxic preconditioning (HP) was applied to induce glycogenesis. The treated cells were subjected to ischemic challenge. The results exhibited that HP of MSC induced glycogen storage and stimulated glycogen catabolism and cellular ATP production, thereby preserving cell viability in long-term ischemia. In vivo study using the mouse limb ischemia model transplanted with HP or control MSC into the ischemic thigh muscles revealed a significant increased retention of MSC with glycogen storage associated with improved limb salvage, perfusion recovery and angiogenesis in the ischemic muscles. In contrast, glycogen synthesis inhibition significantly abolished these improvementsConclusions:hypoxia-induced glycogenesis improves MSC survival and therapy in ischemic tissuesPart 3 Hypoxia-induced glycogenesis promotes MSC survival and therapeuticefficiency in subsequent ischemiaObjective:To determine whether inducible metabolic adaptation enhances mesenchymal stem cells (MSC) survival and therapy under ischemia.Approach and Results:MSC were subjected to glycogen synthase 1-specific small interfering RNA or vehicle treatment, and then sublethal hypoxic preconditioning (HP) was applied to induce glycogenesis. The treated cells were subjected to ischemic challenge. The results exhibited that HP of MSC induced glycogen storage and stimulated glycogen catabolism and cellular ATP production, thereby preserving cell viability in long-term ischemia. In vivo study using the mouse limb ischemia model transplanted with HP or control MSC into the ischemic thigh muscles revealed a significant increased retention of MSC with glycogen storage associated with improved limb salvage, perfusion recovery and angiogenesis in the ischemic muscles. In contrast, glycogen synthesis inhibition significantly abolished these improvementsConclusions:hypoxia-induced glycogenesis improves MSC survival and therapy in ischemic tissuesPart 4 Hypoxia regulates glycogen metabolism via PI3K/Akt-dependented HIF-1 and GSK-3β Signaling CascadeObjective:To determine how hypoxia regulates the metabolic adaptation in MSCsApproach and Results:For pathway study, Akt-specific inhibitor LY294002, HIF-1 siRNA, GSK-3β overexpression adenovirus vector were used. Molecular analysis indicated that PI3K/Akt, hypoxia-inducible factor-1, and glycogen synthase kinase-3β regulated expression of glycogenesis genes, including glucose transporter 1, hexokinase, phosphoglucomutase 1, glycogen synthase 1, and glycogen phosphorylase, thereby regulating glycogen metabolism of stem cell during HP. PI3K/AKT inhibition suppressed activation of HIF-1 and GSK-3β, which may further regulate glycogen metabolism of MSC indirectly. HIF-1α silencing markedly inhibited glycogen accumulation. We further studied the genes which participate in glycogenesis, including glucose transporter 1, hexokinase, phosphoglucomutase 1, and GS1. Evidence from immunofluorescence indicated that these glycogenesis-related genes were upregulated in HP-MSC in a HIF-1-dependent manner, the effects of which are abolished by HIF-la siRNA silencing. These findings were confirmed by Western blot and qPCR. Furthermore, HP treatment induced glycogen synthesis at least in part through inhibition of GSK-3p, HP decreased GSK-3P activity and thus stimulated glycogenesis. Upregulation of GSK-3P activity via adenovirus overexpression of GSK-3β significantly inhibited HP-induced glycogenesis.Conclusions:Hypoxia turns on glycogen storage and regulates its metabolism via PI3K/AKT and its downstream HIF-1 and GSK-3P signal cascades. Glycogen storage is involved in the MSC metabolic adaptation as energy storage to promote MSC survival and therapeutic efficacy for ischemia. Our findings support a novel metabolic adaptation strategy to improve MSC therapy.