Post-ischemic vascular repair is impaired by diabetes mellitus (DM). The neurotrophin receptor p75 (p75NTR) has a prominent role in DM-induced defective post-ischemic neovascularization. Here we have studied the effect of p75NTR gene knockout on ischemic wounds healing in limbs of diabetic mice and elucidated the role of soluble (s) form of the ST2 in DM and limb ischemia (LI). sST2 acts as a decoy receptor and is regarded as a novel biomarker for heart failure and myocardial infarction.Methods
DM was induced by streptozotocin in p75NTR-/- and p75NTR + / + mice. LI and full excisional skin wound on the ipsilateral calf were induced in all mice. After 3 days, wound morphological and histological analyses and gene profiling were performed. To study soluble sST2 regulation by p75NTR in endothelial cells (ECs), HUVECs were silenced for p75NTR and then treated with TNF-α. To determine the possible clinical relevance of sST2, sST2 was measured (ELISA) in the plasma of diabetic patients with leg ischemic ulcers and critical LI (CLI) requiring surgical revascularization or limb amputation and in healthy controls and correlated with clinical data.Results
non-diabetic p75NTR-/- and p75NTR + / + mice exhibited similar wound closure rate and capillary density. DM reduced wound closure and capillary density in p75NTR + / + mice (p < 0.05 and p < 0.01, vs non-diabetic p75NTR + / + mice). Diabetic p75NTR-/- mice showed accelerate wound closure and increased angiogenesis in comparison with diabetic p75NTR + / + mice (p < 0.05 for both comparisons). DM increased sST2 expression in wounded skin of p75NTR + / + mice (p < 0.05 vs. non-diabetic p75NTR + / + mice), but not of p75NTR-/- mice (p=N.S, vs. non-diabetic p75NTR-/- mice). TNF-α increased p75NTR and sST2 expression in cultured HUVECs. Silencing of p75NTR inhibited sST2 expression in TNF-α-stimulated HUVECs. Finally, plasma sST2 was increased in diabetic patients with CLI undergoing surgical revascularization (271.8 ± 138.7 pg/ml vs. 142.8 ± 41.2 pg/ml in healthy controls, p < 0.05; n=53 and n=10, respectively) and within this patient population, sST2 was directly associated with mortality within one year of follow-up, but not with extent of coronary artery disease (p=0.001 and p=NS after multivariate linear regression analysis). sST2 plasma level were further increased in diabetic patients with lower limb amputation for CLI (552.5 ± 118.7 pg/ml, P < 0.05 vs both controls and patients undergoing revascularization).Conclusions
we have identified a link between p75NTR and sST2. sST2 is a possible biomarker and therapeutic target in diabetic patients with peripheral ischemia.