Limb ischemia is a group of diseases caused by stenosis or occlusion of lower extremity arteries, resulting in inadequate perfusion of distal limb tissues. Clinically, arteriosclerosis obliterans, collagen disease-associated vasculitis, and thromboangiitis obliterans are the most common [1]. According to the duration and severity of ischemia, limb ischemia can be divided into acute limb ischemia (ALI) and chronic limb ischemia. ALI is a sudden, recent decrease in limb perfusion (lasting less than 14 days) that endangers the viability of the lower limb [2]. In clinical treatment, amputation may be the only option for many patients. Unfortunately, very few amputees can return to normal life [3]. Therefore, it is urgent to find effective therapeutic measures for limb ischemia.

In recent years, therapeutic neovascularization is a promising option for overcoming ischemia by providing an improved vascular network. Angiogenesis is a process in which vascular endothelial cells form a new vascular network by germinating or embedding based on the original blood vessels, which can establish effective collateral circulation in the ischemic area, restore the blood supply in the lesion area, improve the damaged ischemic tissue, and provide a new idea and approach for the treatment of ischemic diseases of lower limbs [4]. Vascular endothelial growth factor (VEGF) is a growth factor promoting vascular endothelial cells, which can promote the increase of vascular permeability, migration, proliferation, and angiogenesis. The VEGF overexpression has been proven to improve lower limb ischemia in diabetic mice [5].

Aryl hydrocarbon receptor (AhR) is a widely expressed heterodimer transcription regulatory factor, which is mostly located in the cytoplasmic region when it is not bound to ligands (such as TCDD, ITE, etc.). After binding with ligands, AhR ligand complex translocates to the nucleus and forms a heterodimer with aryl hydrocarbon receptor nuclear translocator (ARNT, also known as HIF-1β), thus inducing downstream gene expression [6,7]. At present, only 2–3 studies have revealed that AhR is critical to angiogenesis through the mouse lower limb ischemia model [8,9]. But the specific mechanism of action has not been clarified. Thus, we select AhR as the research object to conduct an in-depth study on its role in lower limb ischemia.

The signal transducer and activator of transcription 1 (STAT1) is a signal transduction protein. More and more studies have found that STAT1 inhibits tumor angiogenesis by down-regulating the expression level of VEGF [[10], [11], [12]], but no studies have revealed its role in ischemic diseases of lower limbs. Since the antiangiogenic effect of STAT1 can serve as an effective target for the treatment of diseases, we will simultaneously explore the mechanism of STAT1 in ischemic diseases of lower limbs.

Therefore, in this study, we hypothesized that AhR inhibits endothelial angiogenesis by promoting STAT1 and thereby down-regulating VEGF expression in lower extremity ischemic diseases.