Deleterious Effects of Remote Ischaemic Per-conditioning During Lower Limb Ischaemia-Reperfusion in Mice

Mitochondrial transplantation reduces lower limb ischemia-reperfusion injury by increasing skeletal muscle energy and adipocyte browning

Recent studies have shown that mitochondrial transplantation can repair lower limb IRI, but the underlying mechanism of the repair effect remains unclear. In this study, we found that in addition to being taken up by skeletal muscle cells, human umbilical cord mesenchymal stem cells (hMSCs)-derived mitochondria were also taken up by adipocytes, which was accompanied by an increase in optic atrophy 1 (OPA1) and uncoupling protein 1. Transplantation of hMSCs-derived mitochondria could not only supplement the original damaged mitochondrial function of skeletal muscle, but also promote adipocyte browning by increasing the expression of OPA1. In this process, mitochondrial transplantation can reduce cell apoptosis and repair muscle tissue, which promotes the recovery of motor function in vivo. To the best of our knowledge, there is no study on the therapeutic mechanism of mitochondrial transplantation from this perspective, which could provide a theoretical basis.

Effect of miR-206 on lower limb ischemia-reperfusion injury in rat and its mechanism

Lower limb ischemia-reperfusion is a common pathological process during clinical surgery. Because lower limb ischemia-reperfusion usually aggravates ischemia-induced skeletal muscle tissue injury after lower limb ischemia-reperfusion, it also causes remote organ heart, intestine, liver, lung and other injuries, and there is no effective clinical treatment for lower limb ischemia-reperfusion injury, so it is urgent to study its injury mechanism. In this study, the rat model of lower limb ischemia-reperfusion was established by clamping the femoral artery with microarterial clips, and the wall destruction such as intimal injury, cell edema, collagen degeneration, neutrophil infiltration, and elastic fiberboard injury of the femoral artery wall was detected. The expression of inflammatory factors was detected by immunohistochemistry. miR-206 preconditioning was used to observe the expression of inflammatory factors, redox status and apoptosis in the vascular wall of rats after acute limb ischemia-reperfusion. Our findings suggest that vascular endothelial cell edema increases, wall thickening, neutrophil infiltration, and elastic fiber layer damage during IRI. Inflammatory factor expression was increased in femoral artery tissue, and miR-206 expression levels were significantly down-regulated. Further studies have found that miR-206 attenuates lower limb IRI by regulating the effects of phase inflammatory factors. In this study, we investigated the effect of miR-206 on inflammatory factors and its possible role in the development of lower limb IRI, providing new research ideas for the regulatory mechanism of lower limb IRI, and providing a certain theoretical basis for the treatment of lower limb ischemia-reperfusion injury after surgery or endovascular intervention.

Engineering of cyanine-based nanoplatform with tunable response toward reactive species for ratiometric NIR-II fluorescent imaging in mice

High-quality second near-infrared (NIR-II) nanoprobes are of great significance for real-time bioimaging and medical diagnosis. Cyanine is an important class of fluorophores to construct activatable probes; however, there are still significant challenges hindering their biological applications, including weak fluorescence in aqueous solution, instability, and insufficient specificity. Herein, an integrated engineering strategy is conducted to develop the cyanine-based activatable NIR-II nanoplatforms with bright, stable emission and high specificity. Specifically, poly(styrene-co-maleic anhydride) (PSMA) is employed to encapsulate NIR-II fluorescent molecules (IR1048) to render the stable and bright NIR-II nanoparticles (PSMA@IR1048 NPs). By charge-modulated strategy, a series of cyanine-fluorophores are loaded on the surface of PSMA@IR1048 NPs and exhibit tunable response toward reactive species. Combing those two strategies, NIR-II ratiometric fluorescent nanoprobes (RNPs, including RNP1, RNP2, and RNP3) are constructed; among them, RNP2 displays hypochlorous acid (HClO) responsive performance and generates a higher NIR-II fluorescent ratio (FL2/FL1) signal. Such nanoprobe can reliably report the pathological HClO level in models of diabetic liver injury and lower limb ischemia-reperfusion (I/R) injury mice. Our study paves an engineering strategy to construct cyanine-based stable, bright, and specific NIR-II probes for bioimaging.