New application of optical agent to image angiogenesis in hindlimb ischemia

Hyperintensity of integrin-targeted fluorescence agent IntegriSense750 accurately predicts flap necrosis compared to Indocyanine green

BACKGROUND

Flap necrosis is a feared complication of reconstructive surgery. Current methods of prediction using Indocyanine green (ICG) lack specificity. IntegriSense750 is a fluorescence agent that binds sites of vascular remodeling. We hypothesized that IntegriSense750 better predicts flap compromise compared to ICG.

METHODS

Fifteen mice underwent lateral thoracic artery axial flap harvest. Mice received an injection of ICG (n = 7) or IntegriSense750 (n = 8) daily from postoperative days (POD) 0-3 and were imaged daily. Mean signal-to-background ratios quantified the change in fluorescence as necrosis progressed.

RESULTS

Mean signal-to-background ratio was significantly higher for IntegriSense750 compared to ICG on POD0 (1.47 ± 0.17 vs. 0.86 ± 0.21, p = 0.01) and daily through POD3 (2.12 ± 0.70 vs. 0.96 ± 0.29, p < 0.001).

CONCLUSIONS

IntegriSense750 demonstrates increased signal-to-background ratio at areas of flap distress compared to ICG which may increase identification of flap necrosis and improve patient outcomes.

Extracellular vesicles from mesenchymal stem cells activates VEGF receptors and accelerates recovery of hindlimb ischemia

Extracellular vesicles (EVs) derived from mesenchymal stem cells (MSCs) are potential therapies for various diseases, but their angiogenic mechanisms of therapeutic efficacy remain unclear. Here, we describe how MSC-EVs, activates VEGF receptors and downstream angiogenesis pathways. Mouse MSC-EVs were isolated from cell culture medium and characterized using transmission electron microscopy, nanoparticle analysis, and western blotting. In vitro migration, proliferation, and tube formation assays using endothelial cells were used to assess the angiogenic potential of MSC-EVs, and revealed higher levels of cellular migration, proliferation, and tube formation after treatment. qRT-PCR and western blotting (WB) revealed higher protein and mRNA expression of the angiogenic genes VEGFR1 and VEGFR2 in mouse SVEC-4 endothelial cells after MSC-EVs treatment. Additionally, other vital pro-angiogenic pathways (SRC, AKT, and ERK) were activated by in vitro MSC-EV treatment. WB and qRT-PCR revealed enriched presence of VEGF protein and miR-210-3p in MSC-EV. The hindlimb ischemia mouse model was established and MSC-EVs with or without Matrigel (EV-MSC+Gel) were injected into the ischemic area and blood reperfusion was monitored using molecular imaging techniques. The in vivo administration of MSC-EVs increased both blood reperfusion and the formation of new blood vessels in the ischemic limb, with the addition of matrigel enhancing this effect further by releasing EVs slowly. MSC-EVs enhance angiogenesis in ischemic limbs, most likely via the overexpression of VEGFR1 and VEGFR2 in endothelial cells. These findings reveal a novel mechanism of activating receptors by MSC-EVs influence the angiogenesis.