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Background: Although regenerative cell therapy is expected to be an alternative treatment for peripheral artery disease (PAD), many regenerative cell therapies have failed to show sufficient efficacy in clinical trials. Most preclinical studies have used acute ischemia models, despite PAD being a chronic disease. In addition, aging and atherosclerosis decrease the quality of a patient's stem cells. Therefore, using a non-acute ischemic preclinical model and stem cells with high regenerative potency are important for the development of effective regenerative therapy. In this study, we assessed the tissue regenerative potential of umbilical cord-derived mesenchymal stromal cells (UCMSCs), which could potentially be an ideal cell source, in a rat model of established ischemia., Methods and results: The regenerative capacity of UCMSCs was analyzed in terms of angiogenesis and muscle regeneration. In vitro analysis showed that UCMSCs secrete high amounts of cytokines associated with angiogenesis and muscle regeneration. In vivo experiments in a rat non-acute ischemia model showed significant improvement in blood perfusion after intravenous injection of UCMSCs compared with injection of culture medium or saline. Histological analysis revealed UCMSCs injection enhanced angiogenesis, with an increased number of von Willebrand factor-positive microcapillaries, and improved muscle regeneration., Conclusions: These results suggest that intravenous administration of UCMSCs may be useful for treating patients with PAD.

Although mesenchymal stem cell transplantation has been successful in the treatment of ischemic cardiomyopathy, the underlying mechanisms remain unclear. Herein, we investigated whether mitochondrial transfer could explain the success of cell therapy in ischemic cardiomyopathy. Mitochondrial transfer in co-cultures of human adipose-derived mesenchymal stem cells and rat cardiomyocytes maintained under hypoxic conditions was examined. Functional recovery was monitored in a rat model of myocardial infarction following human adipose-derived mesenchymal stem cell transplantation. We observed mitochondrial transfer in vitro , which required the formation of cell-to-cell contacts and synergistically enhanced energy metabolism. Rat cardiomyocytes exhibited mitochondrial transfer 3 days following human adipose-derived mesenchymal stem cell transplantation to the ischemic heart surface post-myocardial infarction. We detected donor mitochondrial DNA in the recipient myocardium concomitant with a significant improvement in cardiac function. Mitochondrial transfer is vital for successful cell transplantation therapies and improves treatment outcomes in ischemic cardiomyopathy.

For ischemic cardiomyopathy (ICM) with limited therapeutic options, the induction of arteriogenesis has the potential to improve cardiac function through major restoration of blood flow. We hypothesized that transplantation of a Notch signaling-modified mesenchymal stem cell (SB623 cell) patch would induce angiogenesis and arteriogenesis in ischemic lesions, leading to improvement of left ventricular (LV) function in a rat ICM model. Two weeks after the induction of ischemia, SB623 cell patch transplantation into ICM rats (SB group, n = 10) or a sham operation (no-treatment group, n = 10) was performed. The LV ejection fraction was significantly improved at 6 weeks after SB623 cell patch transplantation ( P < 0.001). Histological findings revealed that the number of von Willebrand factor (vWF)-positive capillary vessels ( P < 0.01) and alpha smooth muscle actin (αSMA)- and vWF-positive arterioles with a diameter greater than 20 µm ( P = 0.002) was significantly increased in the SB group, suggesting the induction of angiogenesis and arteriogenesis. Moreover, rat cardiomyocytes treated with SB623 cell patch transplantation showed upregulation of ephrin-B2 ( P = 0.03) and EphB4 ( P = 0.01) gene expression, indicating arteriogenesis induction. In conclusion, SB623 cell patch transplantation improved LV function by inducing angiogenesis and arteriogenesis in a rat ICM model.

Diabetic foot ulceration is a common chronic diabetic complication. Human umbilical cord-derived mesenchymal stem cells (hUC-MSCs) have been widely used in regenerative medicine owing to their multipotency and easy availability. We developed poly(lactic-co-glycolic acid) (PLGA)-based scaffold to create hUC-MSC tissue sheets. In vitro immunostaining showed that hUC-MSC tissue sheets formed thick and solid tissue sheets with an abundance of extracellular matrix (ECM). Diabetic wounds in mice treated with or without either the hUC-MSC tissue sheet, hUC-MSC injection, or fiber only revealed that hUC-MSC tissue sheet transplantation promoted diabetic wound healing with improved re-epithelialization, collagen deposition, blood vessel formation and maturation, and alleviated inflammation compared to that observed in other groups. Taken collectively, our findings suggest that hUC-MSCs cultured on PLGA scaffolds improve diabetic wound healing, collagen deposition, and angiogenesis, and provide a novel and effective method for cell transplantation, and a promising alternative for diabetic skin wound treatment.

Intravenous infusion of stem cells is a minimally invasive cellular delivery method, though a few have been reported in a critical limb-threatening ischemia (CLTI) animal model or patients. In the present study, we hypothesized that intravenous infusion of bone-marrow derived mesenchymal stem cells (MSCs) improves tissue perfusion in a rat hindlimb ischemia model. Hindlimb ischemia was generated in Sprague-Dawley rats by femoral artery removal, then seven days after ischemic induction intravenous infusion of 1 × 10 6 MSCs (cell group) or vehicle (control group) was performed. As compared with the control, tissue perfusion was significantly increased in the cell group. Histological findings showed that capillary density was significantly increased in the cell group, with infused green fluorescent protein (GFP)-MSCs distributed in the ischemic limb. Furthermore, gene expression of vascular endothelial growth factor (VEGF) was significantly increased in ischemic hindlimb muscle tissues of rats treated with MSC infusion. In conclusion, intravenous infusion of bone-marrow derived MSCs improved tissue perfusion in ischemic hindlimbs through angiogenesis, suggesting that intravenous infusion of MSCs was a promising cell delivery method for treatment of CLTI., (© 2022. The Author(s).)

Notch signaling-modified human mesenchymal stem cell, SB623 cell, is a promising cell therapy product for ischemic stroke. With the aim to expand indications for their use for critical limb-threatening ischemia (CLTI), we hypothesized that SB623 cells improved tissue perfusion by inducing angiogenesis or arteriogenesis in a hindlimb ischemia model rat. In Sprague-Dawley rats, hindlimb ischemia was generated by femoral artery removal, then seven days after ischemic induction 1 × 10 5 SB623 cells or PBS was injected into the ischemic adductor muscle. As compared with the PBS group, tissue perfusion was significantly increased in the SB623 group. While capillary density did not vary between the groups, αSMA- and vWF-positive arterioles with a diameter  > 15 μm were significantly increased in the SB623 group. Whole transcriptome analysis of endothelial cells co-cultured with SB623 cells showed upregulation of the Notch signaling pathway as well as several other pathways potentially leading to arteriogenesis. Furthermore, rat muscle treated with SB623 cells showed a trend for higher ephrin-B2 and significantly higher EphB4 expression, which are known as arteriogenic markers. In the hindlimb ischemia model, SB623 cells improved tissue perfusion by inducing arteriogenesis, suggesting a promising cell source for treatment of CLTI.

Objectives: High-mobility group box 1 protein (HMGB1) fragment enhances bone marrow-derived mesenchymal stem cell (BM-MSC) recruitment to damaged tissue to promote tissue regeneration. This study aimed to evaluate whether systemic injection of HMGB1 fragment could promote tissue repair in a rat model of myocardial infarction (MI)., Methods: HMGB1 (n = 14) or phosphate buffered saline (n = 12, control) was administered to MI rats for 4 days. Cardiac performance and left ventricular remodeling were evaluated using ultrasonography and immunostaining. BM-MSC recruitment to damaged tissue in green fluorescent protein-bone marrow transplantation (GFP-BMT) models was evaluated using immunostaining., Results: At four weeks post-treatment, the left ventricular ejection fraction was significantly improved in the HMGB1 group compared to that in the control. Interstitial fibrosis and cardiomyocyte hypertrophy were also significantly attenuated in the HMGB1 group compared to the control. In the peri-infarction area, VEGF-A mRNA expression was significantly higher and TGFβ expression was significantly attenuated in the HMGB1 group than in the control. In GFP-BMT rats, GFP+/PDGFRα+ cells were significantly mobilized to the peri-infarction area in the HMGB1 group compared to that in the control, leading to the formation of new vasculature. In addition, intravital imaging revealed that more GFP+/PDGFRα+ cells were recruited to the peri-infarction area in the HMGB1 group than in the control 12 h after treatment., Conclusions: Systemic administration of HMGB1 induced angiogenesis and reduced fibrosis by recruiting PDGFRα+ mesenchymal cells from the bone marrow, suggesting that HMGB1 administration might be a new therapeutic approach for heart failure after MI., Competing Interests: The authors have no competing interests to declare.

Background: The extracellular matrix, in particular basement membrane components such as laminins (LMs), is essential for stem cell differentiation and self-renewal. LM511 and LM221 are the main extracellular matrix components of the epicardium, where stem cells were abundant. Here, we examined whether LMs affected the regeneration process by modulating stem cell activities., Methods: In vitro, adhesive, and proliferative activities of mesenchymal stem cells (MSCs) were evaluated on LM511 and LM221. To examine the effects of LMs in vivo, we established an acute myocardial infarction model by ligation of the proximal part of the left anterior descending artery at the height of the left atrial appendage and then placed atelocollagen sheets with or without LM511 and LM221 over the anterolateral surface of the left ventricular wall. Four or 8 weeks later, cardiac function, histology, and cytokine expressions were analyzed., Results: MSCs showed greater proliferation and adhesive properties on LM511 than on LM221. In vivo, at 4 weeks, isolectin B4-positive cells were significantly higher in the LM511-transplanted group than in the control group. Moreover, some isolectin B4-positive cells expressed both platelet-derived growth factor receptor α and CD90, suggesting that LM511 enhanced MSC recruitment and attachment at the implanted site. After 8 weeks, these cells were more abundant than at 4 weeks. Transplantation with LM511-conjugated sheets increased the expression of cardioprotective and angiogenic factors., Conclusions: Transplantation with LM511-conjugated sheets enhanced MSC localization to the implantation site and modulated stem cells activities, leading to angiogenesis in acute myocardial infarction rat models.

For ischemic cardiomyopathy (ICM) with limited therapeutic options, the induction of arteriogenesis has the potential to improve cardiac function through major restoration of blood flow. We hypothesized that transplantation of a Notch signaling-modified mesenchymal stem cell (SB623 cell) patch would induce angiogenesis and arteriogenesis in ischemic lesions, leading to improvement of left ventricular (LV) function in a rat ICM model. Two weeks after the induction of ischemia, SB623 cell patch transplantation into ICM rats (SB group, n = 10) or a sham operation (no-treatment group, n = 10) was performed. The LV ejection fraction was significantly improved at 6 weeks after SB623 cell patch transplantation (P < 0.001). Histological findings revealed that the number of von Willebrand factor (vWF)-positive capillary vessels (P < 0.01) and alpha smooth muscle actin (aSMA)- and vWF-positive arterioles with a diameter greater than 20 µm (P = 0.002) was significantly increased in the SB group, suggesting the induction of angiogenesis and arteriogenesis. Moreover, rat cardiomyocytes treated with SB623 cell patch transplantation showed upregulation of ephrin-B2 (P = 0.03) and EphB4 (P = 0.01) gene expression, indicating arteriogenesis induction. In conclusion, SB623 cell patch transplantation improved LV function by inducing angiogenesis and arteriogenesis in a rat ICM model. [ABSTRACT FROM AUTHOR]

Background: Although endogenous cardiac repair by recruitment of stem cells including bone marrow-derived mesenchymal stem cells (MSCs) or tissue residential stem cells, may be one of therapeutical options for healing the damaged heart, it has not been established how to mobilize stem cells or how to optimize stem cell bed for stem cells by modulation of extracellular matrix. In this study, we hypothesized that combined strategy of prostacyclin agonist (ONO1301), which induce the recruitment of stem cells by enhanced production of scatter factor, with stem cell niche LM221 may enhance regeneration processes by endogenous cardiac repair. Methods and Results: We implanted LM221 immersed collagen sheet with administration of ONO1301 (Combination group, n=8), only LM221 immersed collagen sheet (LM group, n=10), only ONO1301 administration (ONO group, n=10), and the control (n=11). Four weeks later, histological analysis revealed that endothelial cell marker positive cells were significantly higher in the combination group compared with ONO1301 alone group and control group (combination: 380±38 cells/mm2, LM221 alone: 364±36 cells/mm2, ONO1301 alone: 278±12 cells/mm2, control: 195±29 cells/mm2; vs. control; p<0.05), associated with the increase of the production of angiogenesis-related cytokines. Especially, the expression of HGF was significantly higher in the combination group compared with the control group (combination: 3.3±0.8-fold, LM221 alone: 1.8±0.1-fold, ONO1301 alone: 2.3±0.1-fold to the control; p<0.05). In addition, the gene expression of c-kit (stem cell marker) was higher in the combination groups than the ONO1301 alone group (combination: 1.74-fold to the ONO1301 alone; p<0.05). Moreover, infarct size was remarkably reduced in the combination groups than in the ONO1301 alone group and control group (combination: 13.3±2.0%, LM221 alone: 16.4±0.4%, ONO1301 alone: 23.7±4.5%, control: 29.2±3.2cells/mm2; p<0.05). Conclusion: The combination of LM221 and ONO1301 enhance endogenous repair by recruitment of residential stem cells or endothelial cells in rat infarction model, proposing new therapeutical strategy for tissue repair in heart failure. [ABSTRACT FROM AUTHOR]

Introduction: Although systemic administration of high-mobility group box 1 (HMGB1) reportedly mobilize bone marrow mesenchymal stem cells (BM-MSCs) to damaged tissue and promote tissue regeneration, the actual in vivo mechanisms remain unknown. An in vivo imaging system with two-photon microscopy may elucidate the nature of the physiological phenomenon in the living myocardium under beating condition. Hypothesis: We hypothesized that our in vivo imaging system can assess BM-MSC mobilization to injured myocardium by real-time systemic HMGB1 administration. Methods: Two weeks after LAD ligation, HMGB1 (3 mg/kg) or PBS (control; 3 ml/kg) was administered intravenously to 10 green fluorescent protein bone marrow transplantation (GFP-BMT) model rats. BM cell recruitment to the infarction area was analyzed at 6 and 12 h after each injection by in vivo imaging with two-photon microscopy (Figure 1A). Results: In real-time in vivo imaging analysis, more BM-derived GFP cells were mobilized to the infarction area in the HMGB1 group than in the control (Figure 1B). The recruitment of GFP+-BM cells was more enhanced visually at 12 h than at 6 h after HMGB1 injection (Figure 1C). After intravenous Texas-red injection, GFP+-BM cells flowed through the stained vessels at the peri-infarction area, with adherence of some GFP+-BM cells on the vessels or migration to the extracellular matrix 12 h after HMGB1 injection (Figure 1B/1C). These findings were not observed in the normal myocardium. Subsequent histological analysis revealed significant GFP+/PDGFRα+ cell accumulation to the infarction area in the HMGB1 group as compared with the control (HMGB1 vs control, 131±35 vs 20±15; p<0.01), which led to the formation of a new vasculature (Figure 2). Conclusions: The in vivo imaging system could detect BM-MSC mobilization to the peri-infarction area caused by systemic administration of HMGB1. This system may be a useful novel modality for drug screening for various heart diseases. [ABSTRACT FROM AUTHOR]