The therapeutic efficacy of intravenous hiPSC-MSCs infusion without intramuscular cellular transplantation

First, we determined whether hiPSC-MSCs could migrate into the ischemic limb after a single intravenous cellular infusion. Our results showed that most of the hiPSC-MSCs engrafted into the liver 12h after infusion (Supplementary Fig.1). The engrafted hiPSC-MSCs gradually migrated into the ischemic limb at day 3 and disappeared at day 14 (Supplementary Fig.1). A few cells engrafted in the ischemic limb, the engraftment rate was extremely low, evidenced by the DiR signal that was 9.8106 at day 7 after a single intravenous administration of 5105 hiPSC-MSCs versus 1.4109 7 days after a single intramuscular injection.

To compare intravenous cellular administration and intramuscular cellular delivery, three groups of mice that received intravenous hiPSC-MSC infusion once, every week or every 3 days without intramuscular administration of hiPSC-MSCs respectively and one group that received intramuscular hiPSC-MSC delivery only were employed (Fig.1a). Intravenous administration of hiPSC-MSCs once, every week or every 3 days without intramuscular administration of hiPSC-MSCs in the Saline-MSC/once, Saline-MSC/week and Saline-MSC/3 days groups significantly improved blood perfusion from day 7 onwards compared with the ischemia group (Fig.1b, all p<0.05). Repeated intravenous administration of hiPSC-MSCs in the Saline-MSC/week and Saline-MSC/3 days groups further increased blood perfusion at day 35 compared with the Saline-MSC/once group (Fig.1b, all p<0.05), although there was no difference between the first two groups (Fig.1b, p>0.05). Nevertheless intramuscular administration of hiPSC-MSCs in the MSC-Saline group achieved a better beneficial effect than intravenous administration of hiPSC-MSCs in the Saline-MSC/once, Saline-MSC/week and Saline-MSC/3 days groups from day 21 onwards (Fig.1b, all p<0.05).

To evaluate blood perfusion in the groups that received intravenous hiPSC-MSCs infusion without intramuscular hiPSC-MSCs transplantation, Laser Doppler imaging analysis was performed immediately and every week following femoral artery ligation (a). A single or repeated intravenous administration of hiPSC-MSCs in the Saline-MSC/once, Saline-MSC/week or Saline-MSC/3 days groups significantly increased blood perfusion from day 7 onwards compared with the ischemia group. Moreover, repeated intravenous hiPSC-MSCs infusion further improved blood perfusion at day 35. Nonetheless intramuscular hiPSC-MSC transplantation in the MSC-Saline group showed a superior beneficial effect over repeated intravenous hiPSC-MSC infusion in the Saline-MSC/week and Saline-MSC/3 days groups (b).

Taken together, our results demonstrated that systemic intravenous administration of hiPSC-MSCs without intramuscular administration of hiPSC-MSCs improved blood perfusion. Repeated intravenous administration of hiPSC-MSCs every week or every 3 days without intramuscular administration of hiPSC-MSCs further increased blood perfusion compared with a single intravenous injection, although there was no significant difference between intravenous administration repeated every week versus every 3 days. Nonetheless intramuscular administration of hiPSC-MSCs achieved a better beneficial effect than intravenous administration of hiPSC-MSCs once, every week or every 3 days.

Five groups of ICR mice were employed in the main experiment (Fig.2): (1) ischemia group receiving intravenous administration of saline immediately after induction of ischemia and intramuscular administration of culture medium at day 7; (2) MSC-Saline group receiving intravenous administration of saline immediately after induction of ischemia and intramuscular administration of 3106 hiPSC-MSCs at day 7; (3) MSC-MSC/once group receiving intravenous administration of 5105 hiPSC-MSCs immediately after induction of ischemia and intramuscular administration of 3106 hiPSC-MSCs at day 7; (4) MSC-MSC/week group receiving repeated intravenous administration of 5105 hiPSC-MSCs immediately and every week following induction of ischemia for 4 weeks and intramuscular administration of 3106 hiPSC-MSCs at day 7; (5) MSC-MSC/3 days group receiving repeated intravenous administration of 5105 hiPSC-MSCs immediately and every 3 days following induction of ischemia for 4 weeks and intramuscular administration of 3106 hiPSC-MSCs at day 7.

There are five groups of ICR mice in main experiment: ischemia group, MSC-Saline group, MSC-MSC/once group, MSC-MSC/week group, MSC-MSC/3 days group.

Serial laser doppler imaging and analysis was performed to evaluate the blood perfusion and monitor the blood flow recovery in the ischemic hind limb (Fig.3a). After induction of ischemia, blood perfusion of the ligated limb significantly decreased to an extremely low level relative to the non-ligated limb in the ischemia group (2.980.56), MSC-Saline group (2.960.30), MSC-MSC/once group (2.950.48), MSC-MSC/week group (3.010.29) and MSC-MSC/3 days group (2.970.30). There was no significant difference between the five groups (Fig.3b, all p>0.05). These results confirmed that acute hind-limb ischemia was induced in all groups. Intramuscular administration of hiPSC-MSCs with intravenous administration of saline or with intravenous administration of hiPSC-MSCs once or every week or every 3 days in the MSC-Saline, MSC-MSC/once, MSC-MSC/week and MSC-MSC/3 days groups resulted in a significant and progressive improvement in the blood perfusion of the ligated limb from day 14 onwards compared with the ischemia group (Fig.3b, all p<0.05). Intravenous administration of hiPSC-MSCs significantly increased blood perfusion in the MSC-MSC/once, MSC-MSC/week and MSC-MSC/3 days groups from day 7 onwards compared with the ischemia and MSC-Saline groups (Fig.3b, all p<0.05). Repeated intravenous administration of hiPSC-MSCs in the MSC-MSC/week and MSC-MSC/3 days groups further increased blood perfusion from day 28 onwards compared with the MSC-MSC/once group (Fig.3b, all p<0.05). Nevertheless there was no significant difference between mice that received repeated intravenous administration of hiPSC-MSCs in the MSC-MSC/week versus MSC-MSC/3 days groups throughout the study period. On day 35, blood perfusion of the ligated hind limb in the ischemia, MSC-Saline, MSC-MSC/once, MSC-MSC/week and MSC-MSC/3 days groups were 30.570.81, 40.560.84, 44.990.75, 50.410.68 and 51.120.86 respectively.

Laser Doppler imaging analysis was performed immediately and every week following femoral artery ligation to evaluate blood perfusion in the ischemic hind limbs (a). After intramuscular transplantation of hiPSC-MSCs, blood perfusion was significantly improved in the MSC-Saline, MSC-MSC/once, MSC-MSC/week and MSC-MSC/3 days groups compared with the ischemia group from day 14 onwards (all p<0.05). A single and repeated intravenous hiPSC-MSC infusion further improved blood perfusion in the MSC-MSC/once, MSC-MSC/week and MSC-MSC/3 days groups compared with MSC-Saline group (all p<0.05). Moreover, the blood perfusion was significantly higher in the MSC-MSC/week and MSC-MSC/3 days groups compared with the MSC-MSC/once group (all p<0.05). There was no significant difference between the MSC-MSC/week and MSC-MSC/3 days groups (p>0.05) (b).

Taken together, our results showed that systemic intravenous administration of hiPSC-MSCs combined with intramuscular transplantation of hiPSC-MSCs improved blood perfusion in a mouse model of hind-limb ischemia relative to intramuscular hiPSC-MSC transplantation without systemic hiPSC-MSC delivery. In addition, repeated intravenous administration of hiPSC-MSCs every week or every 3 days further improved the therapeutic effects of hiPSC-MSC-based therapy compared with a single intravenous injection. No significant difference was observed between repeated intravenous administration of hiPSC-MSCs every week and every 3 days.

To evaluate neovascularization in the ischemic limb, immunohistochemical staining with anti-mouse alpha-smooth muscle antigen (-SMA) and anti-mouse von Willebrand factor (vWF) antibodies were performed to assess arteriogenesis and angiogenesis following cellular transplantation respectively (Fig.4a). On day 14, intramuscular transplantation of hiPSC-MSCs in the MSC-Saline group did not increase arteriogenesis and capillary formation (Fig.4b,c, p>0.05). Nevertheless, systemic intravenous administration of hiPSC-MSCs in the MSC-MSC/once, MSC-MSC/week and MSC-MSC/3 days groups significantly improved arteriogenesis and capillary formation compared with the ischemia group (Fig.4b,c, all p<0.05). On day 35, compared with the ischemia group, intramuscular transplantation of hiPSC-MSCs in the MSC-Saline, MSC-MSC/once, MSC-MSC/week and MSC-MSC/3 days groups significantly increased neovascularization (Fig.4b,c, all p<0.05). Moreover, systemic intravenous administration of hiPSC-MSCs in the MSC-MSC/once, MSC-MSC/week and MSC-MSC/3 days groups further improved neovascularization compared with the MSC-Saline group on day 35 (Fig.4b,c, p<0.05). In addition, repeated intravenous administration of hiPSC-MSCs in the MSC-MSC/week and MSC-MSC/3 days groups further promoted neovascularization compared with the MSC-MSC/once group (Fig.4b,c, all p<0.05). There was no difference in neovascularization between the MSC-MSC/week and MSC-MSC/3 days groups (Fig.4b,c, all p>0.05).

Immunohistochemical staining with anti-mouse vWF (green) and anti-mouse -SMA (red) antibodies was performed to assess angiogenesis and arteriogenesis in ischemic tissues. Massons trichrome staining was performed to evaluate the degree of fibrosis (a). On day 14, neovascularization was markedly increased in the MSC-MSC/once, MSC-MSC/week and MSC-MSC/3 days groups, not in the MSC-Saline group, relative to the ischemia group. On day 35, after intramuscular transplantation of hiPSC-MSCs, neovascularization was significantly improved in the MSC-Saline, MSC-MSC/once, MSC-MSC/week and MSC-MSC/3 days groups compared with the ischemia group (all p<0.05). Intravenous administration of hiPSC-MSCs in the MSC-MSC/once, MSC-MSC/week and MSC-MSC/3 days groups enhanced the therapeutic effects of intramuscularly transplanted hiPSC-MSCs on neovascularization compared with the MSC-Saline group (all p<0.05). Moreover, neovascularization was further enhanced by repeated intravenous hiPSC-MSC infusion in the MSC-MSC/week and MSC-MSC/3 days groups compared with the MSC-MSC/once group (b, c). On day 14, fibrosis was remarkably decreased in the MSC-MSC/once, MSC-MSC/week and MSC-MSC/3 days groups, not in the MSC-Saline group, relative to the ischemia group. On day 35, after intramuscular transplantation of hiPSC-MSCs, fibrosis was significantly reduced in the MSC-Saline, MSC-MSC/once, MSC-MSC/week and MSC-MSC/3 days groups compared with the ischemia group (all p<0.05). Intravenous administration of hiPSC-MSCs in the MSC-MSC/once, MSC-MSC/week and MSC-MSC/3 days groups enhanced the therapeutic effects of intramuscularly transplanted hiPSC-MSCs on reduction of fibrosis compared with the MSC-Saline group (all p<0.05). Moreover, the anti-fibrotic effect was further enhanced by repeated intravenous hiPSC-MSC infusion in the MSC-MSC/week and MSC-MSC/3 days groups compared with the MSC-MSC/once group (d).

To assess the degree of fibrosis in the ischemic limb, Massons Trichrome staining were performed to determine the percentage of fibrotic tissue in the ischemic limb (Fig.4a). On day 14, intramuscular transplantation of hiPSC-MSCs in the MSC-Saline group did not decrease fibrosis (Fig.4d, p>0.05). Nevertheless, systemic intravenous administration of hiPSC-MSCs in the MSC-MSC/once, MSC-MSC/week and MSC-MSC/3 days groups significantly reduced fibrosis compared with the ischemia group (Fig.4d, all p<0.05). Compared with the ischemia group, intramuscular transplantation of hiPSC-MSCs in the MSC-Saline, MSC-MSC/once, MSC-MSC/week and MSC-MSC/3 days groups significantly ameliorated fibrosis on day 35 (Fig.4d, all p<0.05). Moreover, systemic intravenous administration of hiPSC-MSCs in the MSC-MSC/once, MSC-MSC/week and MSC-MSC/3 days groups significantly reduced fibrosis compared with the MSC-Saline group (Fig.4d, all p<0.05). In addition, repeated intravenous administration of hiPSC-MSCs in the MSC-MSC/week and MSC-MSC/3 days groups further decreased fibrosis compared with the MSC-MSC/once group (Fig.4d, all p<0.05). There were no differences in fibrosis between the MSC-MSC/week and MSC-MSC/3 days groups (Fig.4d, all p>0.05).

Taken together, our results showed that systemic intravenous administration of hiPSC-MSCs combined with intramuscular transplantation of hiPSC-MSCs promoted neovascularization and reduced fibrosis in a mouse model of hind-limb ischemia. Repeated intravenous administration of hiPSC-MSCs every week or every 3 days further increased the neovascularization and decreased the fibrosis following cellular transplantation compared with a single intravenous injection. No significant difference was observed between repeated intravenous administration of hiPSC-MSCs every week and every 3 days.

Fluorescent imaging of ischemic hind limbs was performed immediately and every week after induction of ischemia to access the cellular engraftment and survival of intramuscularly transplanted hiPSC-MSCs (Fig.5a). To avoid any confusion on the fluorescent signal, intravenous administered hiPSC-MSCs were not labeled with DiR. There was no significant difference in fluorescent signal intensity over the ischemic hind limb after intramuscular cellular transplantation (Fig.5b, all p>0.05). Systemic intravenous administration of hiPSC-MSCs significantly increased cellular engraftment and survival in the MSC-MSC/once, MSC-MSC/week and MSC-MSC/3 days groups from day 14 onwards relative to the MSC-Saline group (Fig.5b, all p<0.05). Moreover, repeated intravenous administration of hiPSC-MSCs in the MSC-MSC/week and MSC-MSC/3 days groups further improved cellular engraftment and survival from day 21 onwards compared with the MSC-MSC/once group (Fig.5b, all p<0.05). There was no significant difference between mice that received repeated intravenous administration of hiPSC-MSCs in the MSC/week and MSC-MSC/3 days groups throughout the study period. On day 35, the estimated survival rates in MSC-Saline, MSC-MSC/once, MSC-MSC/week and MSC-MSC/3 days groups decreased to 2.590.31%, 8.330.54%, 13.560.49% and 14.230.42%, respectively (Supplementary Fig.2 and Supplementary Data1).

A series of fluorescent images of ischemic hind limbs was performed immediately and every week following intramuscular transplantation of hiPSC-MSCs to detect the fate of intramuscularly transplanted hiPSC-MSCs (a). A single or repeated intravenous hiPSC-MSCs infusion in the MSC-MSC/once, MSC-MSC/week and MSC-MSC/3 days groups significantly prolonged the survival of intramuscular transplanted hiPSC-MSCs from day 14 onwards compared with the MSC-Saline group (all p<0.05). Moreover, repeated intravenous hiPSC-MSCs infusion in the MSC-MSC/week and MSC-MSC/3 days groups further improved the survival of intramuscularly transplanted hiPSC-MSCs from day 21 onwards compared with the MSC-MSC/once group (all p<0.05), whereas no significant difference was observed between MSC-MSC/week and MSC-MSC/3 days groups (p>0.05) (b).

Cellular engraftment and survival of intramuscularly transplanted hiPSC-MSCs were further confirmed by immunohistochemical double staining with anti-human GAPDH and anti-human mitochondria antibodies (Fig.6a). Systemic intravenous administration of hiPSC-MSCs significantly increased human GAPDH and human mitochondria positive cells over the ischemic hind limb in the MSC-MSC/once, MSC-MSC/week and MSC-MSC/3 days groups from day 14 onwards relative to the MSC-Saline group (Fig.6b, all p<0.05). Moreover, on day 35, repeated intravenous administration of hiPSC-MSCs in the MSC-MSC/week and MSC-MSC/3 days groups further increased the human GAPDH and human mitochondria positive cells compared with the MSC-MSC/once group (Fig.6b, all p<0.05). No difference between the MSC-MSC/week and MSC-MSC/3 days groups was noted (Fig.6b, all p>0.05).

The engraftment of intramuscularly transplanted hiPSC-MSCs was further confirmed by double immunohistochemical staining with anti-human GAPDH (green) and anti-human mitochondria antibodies (red) at day 14 and 35 (a). A single or repeated intravenous hiPSC-MSC infusion in the MSC-MSC/once, MSC-MSC/week and MSC-MSC/3 days groups significantly improved the engraftment of intramuscularly transplanted hiPSC-MSCs from day 14 onwards (all p<0.05). Repeated intravenous hiPSC-MSC infusion in the MSC-MSC/week and MSC-MSC/3 days groups further improved the engraftment of intramuscular transplanted hiPSC-MSCs at day 35 compared with the MSC-MSC/once group (all p<0.05), whereas no significant difference was observed between the MSC-MSC/week and MSC-MSC/3 days groups (p>0.05) (b).

Taken together, our results demonstrated that systemic intravenous administration of hiPSC-MSCs enhanced engraftment and survival of intramuscularly transplanted hiPSC-MSCs. In addition, repeated intravenous administration every week or every 3 days further increased the cellular engraftment and survival compared with a single intravenous injection. No significant difference was observed between repeated intravenous administration of hiPSC-MSCs every week versus every 3 days.

Immunohistochemical staining with anti-mouse CD68 antibody was performed to calculate the number of macrophages after cellular transplantation and evaluate the infiltration of macrophages (Fig.7a). M2 macrophages were further characterized by immunohistochemical staining with anti-mouse Arginase-1 antibody (Fig.7a). Although there was no significant difference between any of the five groups at day 7 and 14 after induction of ischemia (Fig.7b, all p>0.05), intramuscular administration of hiPSC-MSCs in the MSC-Saline, MSC-MSC/once, MSC-MSC/week and MSC-MSC/3 days groups significantly increased M2 macrophage polarization in the ligated limb from day 14 onwards relative to the ischemia group (Fig.7c, all p<0.05). Moreover, intravenous administration of hiPSC-MSCs remarkedly promoted M2 macrophage polarization in the MSC-MSC/once, MSC-MSC/week and MSC-MSC/3 days groups from day 7 onwards compared with the ischemia and MSC-Saline groups (Fig.7c, all p<0.05). On day 35, intramuscular administration of hiPSC-MSCs in MSC-Saline group had significantly decreased the infiltration of macrophages although the M2 macrophage percentage was similar to that in the ischemia group (Fig.7b,c, all p<0.05). Systemic intravenous administration of hiPSC-MSCs in the MSC-MSC/once, MSC-MSC/week and MSC-MSC/3 days groups significantly decreased macrophage infiltration and increased M2 macrophage polarization relative to the MSC-Saline group (Fig.7b,c, all p<0.05). Repeated intravenous administration of hiPSC-MSCs in the MSC-MSC/week and MSC-MSC/3 days groups further reduced the infiltration of macrophages and increased the polarization of M2 macrophages compared with the MSC-MSC/once group (Fig.7b,c, all p<0.05). There was no noticeable difference in either the infiltration of macrophages or polarization of M2 macrophages between the MSC-MSC/week and MSC-MSC/3 days groups (Fig.7b,c, all p>0.05).

Muscular infiltration of macrophages was determined by immunohistochemical staining with anti-mouse CD68 antibody (green) at day 7, 14, and 35. Number of M2 macrophages was detected by immunohistochemical staining with anti-mouse Arginase-1 antibodies (red) (a). At day 35, after intramuscular transplantation of hiPSC-MSCs, total macrophages were significantly decreased in the MSC-Saline, MSC-MSC/once, MSC-MSC/week and MSC-MSC/3 days groups compared with the ischemia group (all p<0.05). A single or repeated intravenous hiPSC-MSCs infusion in the MSC-MSC/once, MSC-MSC/week and MSC-MSC/3 days groups significantly decreased the muscular infiltration of macrophages compared with the MSC-Saline group (all p<0.05). In addition, repeated intravenous hiPSC-MSCs infusion in the MSC-MSC/week and MSC-MSC/3 days groups further decreased the muscular infiltration of macrophages compared with the MSC-MSC/once group (all p<0.05). Nevertheless no significant difference was observed between groups at day 7 and 14 (all p>0.05) (b). Intramuscular transplantation of hiPSC-MSCs without intravenous hiPSC-MSC infusion significantly increased the polarization of M2 macrophages at day 14 compared with the ischemia group (p<0.05). A single or repeated intravenous hiPSC-MSC infusion in the MSC-MSC/once, MSC-MSC/week and MSC-MSC/3 days groups significantly improved the polarization of M2 macrophages from day 7 onwards (all p<0.05). Repeated hiPSC-MSCs infusion further promoted the polarization of M2 macrophages compared with a single intravenous hiPSC-MSCs infusion in the MSC-MSC/once group at day 35 (all p<0.05) (c).

Taken together, our results demonstrated that systemic intravenous administration of hiPSC-MSCs decreased the infiltration of macrophages and increased the polarization of M2 macrophages. Repeated intravenous administration of hiPSC-MSCs every week or every 3 days further decreased the infiltration of macrophages and increased the polarization of M2 macrophages compared with a single intravenous injection, whereas no significant difference was observed between repeated intravenous administration of hiPSC-MSCs every week and every 3 days.

The limb tissue level of a specific subset-related cytokines was measured using a commercial mouse inflammatory factor array. For anti-inflammatory cytokines, on day 14, there was no significant difference on interleukin (IL)10 and vascular endothelial growth factor (VEGF) among the ischemia, MSC-Saline and MSC-MSC/once groups (Supplementary Fig.3a,b, all p>0.05). Nonetheless, repeated systemic intravenous hiPSC-MSC infusion in the MSC-MSC/week and MSC-MSC/3 days groups significantly increased IL-10 and VEGF compared with the ischemia group (Supplementary Fig.3a,b, all p<0.05). Moreover, an increase of IL-10 was observed in the MSC-MSC/week and MSC-MSC/3 days groups relative to the MSC-Saline group (Supplementary Fig.3a,b, all p<0.05). On day 35, intramuscular transplantation of hiPSC-MSCs in the MSC-Saline group did not significantly improved IL-10 relative to ischemia group. Nevertheless, systemic intravenous hiPSC-MSC infusion in the MSC-MSC/once, MSC-MSC/week and MSC-MSC/3 days groups significantly improved IL-10 compared with the ischemia group (Supplementary Fig.3a, all p<0.05). Moreover, repeated systemic intravenous hiPSC-MSC infusion in the MSC-MSC/week and MSC-MSC/3 days groups further increased IL-10 compared with the MSC-MSC/once group (Supplementary Fig.3a, all p<0.05). No significant difference on VEGF was observed among all five groups on day 35 (Supplementary Fig.3b, all p<0.05).

For inflammatory cytokines, on day 14, intramuscular transplantation of hiPSC-MSCs in the MSC-Saline, MSC-MSC/once, MSC-MSC/week and MSC-MSC/3 days groups significantly decreased IL-1A and IL-17A compared with the ischemia group (Supplementary Fig.3c,d, all p<0.05). Nonetheless, there was no significant difference among the MSC-Saline, MSC-MSC/once, MSC-MSC/week and MSC-MSC/3 days groups (Supplementary Fig.3c,d, all p>0.05). There was no significant difference on IL-2 and macrophage colony-stimulating factor (MCSF) among the ischemia, MSC-Saline and MSC-MSC/once groups (Supplementary Fig.3e,f, all p>0.05). Nonetheless, repeated systemic intravenous hiPSC-MSC infusion in the MSC-MSC/week and MSC-MSC/3 days groups significantly decreased IL-2 and MCSF compared with the ischemia group (Supplementary Fig.3e,f, all p<0.05). On day 35, intramuscular transplantation of hiPSC-MSCs in the MSC-Saline, MSC-MSC/once, MSC-MSC/week and MSC-MSC/3 days groups significantly reduced IL-17A relative to ischemia group (Supplementary Fig.3d, all p<0.05). Moreover, repeated systemic intravenous hiPSC-MSC infusion in the MSC-MSC/week and MSC-MSC/3 days groups further decreased IL-17A compared with the MSC-Saline and MSC-MSC/once groups respectively (Supplementary Fig.3d, all p<0.05). No significant difference on IL-1A, IL-2 and MCSF was observed among all five groups on day 35 (Supplementary Fig.3c,e,f, all p>0.05).

Taken together, our results demonstrated that systemic intravenous administration of hiPSC-MSCs could improve anti-inflammatory cytokines and decreased inflammatory cytokines. Repeated intravenous administration of hiPSC-MSCs every week or every 3 days further improved anti-inflammatory cytokines and decreased inflammatory cytokines compared with a single intravenous injection. No significant difference was observed between repeated intravenous administration of hiPSC-MSCs every week and every 3 days.

Flow cytometry analysis of fresh splenocytes was performed to assess splenic Tregs and natural killer (NK) cells populations and so determine the in vivo immunomodulatory effect of systemic administration of hiPSC-MSCs (Fig.8a). Splenic NK cells were defined as both a CD49b-FITC and NK1.1-APC positive cell population. Our result showed that splenic NK cells progressively decreased following intramuscular hiPSC-MSC transplantation or intravenous hiPSC-MSC infusion in the MSC-Saline, MSC-MSC/once, MSC-MSC/week and MSC-MSC/3 days groups, whereas no significant difference was noted between different time points in the ischemia group (Supplementary Fig.4a). Compared with the ischemia group, intramuscular administration of hiPSC-MSCs in the MSC-Saline, MSC-MSC/once, MSC-MSC/week and MSC-MSC/3 days groups significantly decreased splenic NK cells from day 14 onwards (Fig.8b, all p<0.05). Systemic intravenous hiPSC-MSC infusion in the MSC-MSC/once, MSC-MSC/week and MSC-MSC/3 days groups significantly reduced splenic NK cells from day 7 onwards relative to the ischemia and MSC-Saline groups (Fig.8b, all p<0.05). Repeated systemic intravenous hiPSC-MSC infusion in the MSC-MSC/week and MSC-MSC/3 days groups further reduced splenic NK cells from day 14 onwards compared with the MSC-MSC/once group (Fig.8b, all p<0.05). Nonetheless no significant difference was observed between the MSC-MSC/week and MSC-MSC/3 days groups (Fig.8b, all p>0.05).

Splenic Tregs and NK cells were determined by flow cytometry analysis at day 7, 14 and 35 (a). After intramuscular transplantation of hiPSC-MSCs, splenic NK cells were significantly decreased in the MSC-Saline, MSC-MSC/once, MSC-MSC/week and MSC-MSC/3 days groups from day 14 onwards compared with the ischemia group (all p<0.05). A single or repeated intravenous hiPSC-MSC infusion in the MSC-MSC/once, MSC-MSC/week and MSC-MSC/3 days groups significantly decreased splenic NK cells from day 7 onwards compared with the ischemia and MSC-Saline groups (all p<0.05). Repeated intravenous hiPSC-MSC infusion in the MSC-MSC/week and MSC-MSC/3 days groups further decreased splenic NK cells from day 14 onwards compared with the MSC-MSC/once group (all p<0.05) (b). After intramuscular transplantation of hiPSC-MSCs, splenic Tregs were significantly increased in the MSC-Saline, MSC-MSC/once, MSC-MSC/week and MSC-MSC/3 days groups at day 35 compared with the ischemia group (all p<0.05). A single or repeated intravenous hiPSC-MSC infusion in the MSC-MSC/once, MSC-MSC/week and MSC-MSC/3 days groups significantly increased splenic Tregs compared with the ischemia and MSC-Saline groups (all p<0.05). Moreover, repeated intravenous hiPSC-MSC infusion in the MSC-MSC/week and MSC-MSC/3 days groups further increased splenic Tregs from day 14 onwards compared with the MSC-MSC/once group (all p<0.05) (c).

Splenic Tregs were determined as Foxp3 positive cells in a proportion of pre-gated CD4 positive cells. Our result showed that splenic Tregs reached a peak on day 7 in the MSC-MSC/once group, whereas these immunomodulatory cells continued to increase in the MSC-MSC/week and MSC-MSC/3 days groups. No significant difference was observed between different time points in the ischemia and MSC-Saline groups (Supplementary Fig.4b). Compared with the ischemia group, intramuscular administration of hiPSC-MSCs in the MSC-Saline, MSC-MSC/once, MSC-MSC/week and MSC-MSC/3 days groups significantly increased splenic Tregs on day 35 (Fig.8c, all p<0.05). Intravenous hiPSC-MSC infusion in the MSC-MSC/once, MSC-MSC/week and MSC-MSC/3 days groups significantly improved splenic Tregs from day 7 onwards compared with the ischemia and MSC-Saline groups (Fig.8c, all p<0.05). Repeated systemic intravenous hiPSC-MSCs infusion in the MSC-MSC/week and MSC-MSC/3 days groups further increased splenic Tregs from day 14 onwards compared with the MSC-MSC/once group (Fig.8c, all p<0.05), but there was no significant difference between the MSC-MSC/week and MSC-MSC/3 days groups (Fig.8c, all p>0.05).

Taken together, our results demonstrated that systemic intravenous administration of hiPSC-MSCs could modulate systemic immune cell activation by decreasing splenic NK cells as well as increasing splenic Tregs. Repeated intravenous administration of hiPSC-MSCs every week or every 3 days further decreased splenic NKs and increased splenic Tregs compared with a single intravenous injection. No significant difference was observed between repeated intravenous administration of hiPSC-MSCs every week and every 3 days.

To compare the survival and engraftment of intramuscularly transplanted hiPSC-MSCs with intervenous infusion of hiPSC-MSCs and subcutaneous administration of cyclosporine A, fluorescent imaging of ischemic hind limb was performed immediately and every week in the MSC-Saline-Cyc, MSC-MSC/once-Cyc and MSC-MSC/week-Cyc groups (Supplementary Fig.5a). There was no significant difference in cellular engraftment between the MSC-MSC/once and MSC-Saline-Cyc groups through this study (Supplementary Fig.5b, p>0.05). Although repeated intravenous infusion of hiPSC-MSCs without subcutaneous administration of cyclosporine A remarkedly increased cell engraftment in the MSC-MSC/week group relative to the MSC-MSC/once group (Supplementary Fig.5b, p<0.05), no significant difference was observed after subcutaneous administration of cyclosporine A between the MSC-MSC/week-Cyc and MSC-MSC/once-Cyc groups (Supplementary Fig.5b, p>0.05). Nonetheless, subcutaneous administration of cyclosporine A did not improve the cell engraftment in the MSC-MSC/once-Cyc and MSC-MSC/week-Cyc groups relative to the MSC-MSC/once and MSC-MSC/week groups respectively (Supplementary Fig.5b, p>0.05).

To compare the therapeutic efficacy of intramuscularly transplanted hiPSC-MSCs with intervenous infusion of hiPSC-MSCs and subcutaneous administration of cyclosporine A, serial laser doppler imaging and analysis was performed to evaluate the blood perfusion and monitor the blood flow recovery in the ischemic hind limb (Supplementary Fig.6a). When comparison between the MSC-MSC/once and MSC-Saline-Cyc groups was performed, intravenous infusion of hiPSC-MSCs significantly improved blood perfusion in the MSC-MSC/once group relative to MSC-Saline-Cyc group during the first 2 weeks (Supplementary Fig.6b, p<0.05). Following intramuscular hiPSC-MSC transplantation at day 7, blood perfusion progressly increased in the MSC-MSC/once and MSC-Saline-Cyc groups. Nevertheless, no significant difference was observed between the MSC-MSC/once and MSC-Saline-Cyc groups from day 21 onwards (Supplementary Fig.6b, p>0.05). Repeated intravenous infusion of hiPSC-MSCs with or without subcutaneous administration of cyclosporine A significantly improved blood perfusion at day 35 in the MSC-MSC/week and MSC-MSC/week-Cyc groups compared with the MSC-MSC/once and MSC-MSC/once-Cyc groups respectively (Supplementary Fig.6b, p<0.05). Nonetheless, subcutaneous administration of cyclosporine A did not improve the blood perfusion in the MSC-MSC/once-Cyc and MSC-MSC/week-Cyc groups relative to the MSC-MSC/once and MSC-MSC/week groups respectively (Supplementary Fig.6b, p>0.05).

Cumulatively, our results demonstrated that no significant difference was observed in cell engraftment between a single or repeated intravenous hiPSC-MSC infusion and subcutaneous administration of cyclosporine A. Although there was no significant difference in blood perfusion between the cyclosporine A and single hiPSC-MSC infusion, a significantly improved blood perfusion was observed in the repeated hiPSC-MSC infusion groups relative to the cyclosporine A group. Furthermore, subcutaneous administration of cyclosporine A did not further increased cell engraftment or therapeutic efficacy in either single or repeated hiPSC-MSC infusion groups.

Continued here:
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