Modulation of miR-29a and ADAM12 Reduces Post-Ischemic Skeletal Muscle Injury and Improves Perfusion Recovery and Skeletal Muscle Function in a Mouse Model of Type 2 Diabetes and Peripheral Artery Disease

Both Type 1 diabetes mellitus (DM1) and type 2 diabetes mellitus (DM2) are associated with an increased risk of limb amputation in peripheral arterial disease (PAD). How diabetes contributes to poor PAD outcomes is poorly understood but may occur through different mechanisms in DM1 and DM2. Previously, we identified a disintegrin and metalloproteinase gene 12 (ADAM12) as a key genetic modifier of post-ischemic perfusion recovery. In an experimental PAD, we showed that ADAM12 is regulated by miR-29a and this regulation is impaired in ischemic endothelial cells in DM1, contributing to poor perfusion recovery. Here we investigated whether miR-29a regulation of ADAM12 is altered in experimental PAD in the setting of DM2. We also explored whether modulation of miR-29a and ADAM12 expression can improve perfusion recovery and limb function in mice with DM2. Our result showed that in the ischemic limb of mice with DM2, miR-29a expression is poorly downregulated and ADAM12 upregulation is impaired. Inhibition of miR-29a and overexpression of ADAM12 improved perfusion recovery, reduced skeletal muscle injury, improved muscle function, and increased cleaved Tie 2 and AKT phosphorylation. Thus, inhibition of miR-29a and or augmentation of ADAM12 improves experimental PAD outcomes in DM2 likely through modulation of Tie 2 and AKT signalling.

In a Mouse Model of Type 2 Diabetes and Peripheral Artery Disease, Modulation of MirR29a and ADAM12 Reduced Post -Ischemic Skeletal Muscle Injury, Improved Perfusion Recovery and Skeletal Muscle Function

Diabetes Mellitus (DM) is a major risk factor for developing peripheral arterial disease (PAD) and individuals with DM have worse PAD outcomes but the molecular mechanisms involved are poorly understood. Previously, in a hind limb ischemia (HLI) model of PAD, we identified a disintegrin and metalloproteinase gene 12 (ADAM12) as a key genetic modifier of post-ischemic perfusion recovery. Moreover, we showed that expression of ADAM12 in mouse and human tissue is regulated by miR29a. In non-diabetic mice, miR29a expression is downregulated after HLI that allows increased expression of ADAM12. However, upon HLI in high fat diet feed (HFD) mice, a model of type 2 diabetes, miR29a expression remains elevated that prevents ADAM12 increase and results in poor reperfusion recovery, increased skeletal muscle injury and decreased muscle function. Hence, we hypothesized that inhibition of miR29a or augmenting ADAM12 would improve these functional outcomes.

Mice (male, 26–28 weeks old) were randomized into 3 treatment groups and their hind limbs were treated with saline (grp1), ADAM12 cDNA (grp 2) or mir29a-inhibitor (grp3), through targeted micro-bubble delivery. Mice were treated at -3 days and -1 pre-surgery, followed by post-surgery weekly boosting. HLI was achieved by unilateral ligation and excision of the femoral artery of the left hind limb. The right hind limb served as non-ischemic control. Gene expression analysis in the hind limbs 3 days post HLI showed decreased miR29a expression in normal chow fed B6, but elevated miR29a expression in HFD (B6 vs HFD; 0.5730±0.01 vs.1.02 ± 0.06, n=3–4, p= 0.001). Treatment with miR29a inhibitor decreased miR29a expression in HFD and increased ADAM12 expression compared to control untreated HFD mice (miR29a INH vs Control HFD: 0.70±0.06 vs 1.02±0.06, n= 4–5, p= 0.004) ADAM12 expression (miR29A INH vs Control: HFD 208.62±24.52 vs 11.75±4.94, n= 3–4 P<0.01). Although ADAM12 cDNA improved ADAM12 expression, miR29a inhibition increased ADAM12 expression to a greater extent (HFD vs ADAM12 vs miR29aINH; 11.75±4.94 vs 20.71±2.98 vs 208.62±24.52, n3-4, p=< 0.001). Accordingly, miR29a inhibition and ADAM12 augmentation decreased skeletal muscle injury assessed by the number of centralized nuclei/muscle fibre (Control vs ADAM12 vs miR29aINH: 0.252±0.043, vs 0.139±0.041 vs 0.040±0.012 n=4, p= 0.05), and improved skeletal muscle function assessed as maximum muscle contraction (Control vs ADAM12 vs miR29aINH: 0.17±0.06 vs 0.26±0.06, vs 0.54±0.08, n=6–7, p<0.01). It also improved perfusion recovery, (% ischemic to non-ischemic limb, control vs ADAM12 vs miR29aINH: 42.52±5.35, vs 58.45±4.87, vs 97.59±6.14, n= 5–10, p<0.01). Thus, our results show augmentation of ADAM12 and Inhibition of MiR29a improves outcomes in experimental PAD in diabetic mice but inhibiting miR29a is a more effective strategy.

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