A Meta-Analysis of Randomized Controlled Trials on Therapeutic Efficacy and Safety of Autologous Cell Therapy for Atherosclerosis Obliterans

Sirtuin 6 Deacetylates Apoptosis-Associated Speck-Like Protein (ASC) to Inhibit Endothelial Cell Pyroptosis in Atherosclerosis

Endothelial cell dysfunction is the main pathology of atherosclerosis (AS). Sirtuin 6 (SIRT6), a deacetylase, is involved in AS progression. This study aimed to investigate the impacts of SIRT6 on the pyroptosis of endothelial cells and its underlying mechanisms. ApoE-/- mice were fed a high-fat diet (HFD) to establish the AS mouse model, atherosclerotic lesions were evaluated using oil red O staining, and blood lipids and inflammatory factors were measured using corresponding kits. Human umbilical vein endothelial cells (HUVECs) were treated with oxidized low-density lipoprotein (ox-LDL) to establish the cell model, and pyroptosis was evaluated by flow cytometry, ELISA, and western blot. Immunoprecipitation (IP), co-IP, western blot, and immunofluorescence were used to detect the molecular mechanisms. The results showed that SIRT6 expression was downregulated in the blood of HFD-induced mice and ox-LDL-induced HUVECs. Overexpression of SIRT6 reduced atherosclerotic lesions, blood lipids, and inflammation in vivo and suppressed pyroptosis of HUVECs in vitro. Moreover, SIRT6 interacted with ASC to inhibit the acetylation of ASC, thus, reducing the interaction between ASC and NLRP3. Moreover, SIRT6 inhibits endothelial cell pyroptosis in the aortic roots of mice by deacetylating ASC. In conclusion, SIRT6 deacetylated ASC to inhibit its interaction with NLRP3 and then suppressed pyroptosis of endothelial cells, thus, decelerating the progression of AS. The findings provide new insights into the function of SIRT6 in AS.

Modalities to Deliver Cell Therapy for Treatment of Chronic Limb Threatening Ischemia

Significance: Chronic limb threatening ischemia (CLTI) is a severe form of peripheral arterial disease (PAD) that is associated with high rates of morbidity and mortality, and especially limb loss. In patients with no options for revascularization, stem cell therapy is a promising treatment option. Recent Advances: Cell therapy directly delivered to the affected ischemic limb has been shown to be a safe, effective, and feasible therapeutic alternative for patients with severe PAD. Multiple methods for cell delivery, including local, regional, and combination approaches, have been examined in both pre-clinical studies and clinical trials. This review focuses on delivery modalities used in clinical trials that deliver cell therapy to patients with severe PAD. Critical Issues: Patients with CLTI are at high risk for complications of the disease, such as amputations, leading to a poor quality of life. Many of these patients do not have viable options for revascularization using traditional interventional or surgical methods. Clinical trials have shown therapeutic benefit for cell therapy in these patients, but methods of cell treatment are not standardized, including the method of cell delivery to the ischemic limb. Future Directions: The ideal delivery approach for stem cell therapy in PAD patients remains unclear. Further studies are needed to determine the best modality of cell delivery to maximize clinical benefits.

Translational Relevance of Advanced Age and Atherosclerosis in Preclinical Trials of Biotherapies for Peripheral Artery Disease

Approximately 6% of adults worldwide suffer from peripheral artery disease (PAD), primarily caused by atherosclerosis of lower limb arteries. Despite optimal medical care and revascularization, many PAD patients remain symptomatic and progress to critical limb ischemia (CLI) and risk major amputation. Delivery of pro-angiogenic factors as proteins or DNA, stem, or progenitor cells confers vascular regeneration and functional recovery in animal models of CLI, but the effects are not well replicated in patients and no pro-angiogenic biopharmacological procedures are approved in the US, EU, or China. The reasons are unclear, but animal models that do not represent clinical PAD/CLI are implicated. Consequently, it is unclear whether the obstacles to clinical success lie in the toxic biochemical milieu of human CLI, or in procedures that were optimized on inappropriate models. The question is significant because the former case requires abandonment of current strategies, while the latter encourages continued optimization. These issues are discussed in the context of relevant preclinical and clinical data, and it is concluded that preclinical mouse models that include age and atherosclerosis as the only comorbidities that are consistently present and active in clinical trial patients are necessary to predict clinical success. Of the reviewed materials, no biopharmacological procedure that failed in clinical trials had been tested in animal models that included advanced age and atherosclerosis relevant to PAD/CLI.

Preventive Therapies in Peripheral Arterial Disease

Atherosclerosis, while initially deemed a bland proliferative process, is now recognized as a multifactorial-lipoprotein-mediated inflammation-driven pathway. With the rising incidence of atherosclerotic disease of the lower extremity arteries, the healthcare burden and clinical morbidity and mortality due to peripheral artery disease (PAD) are currently escalating. With a healthcare cost burden of over 21 billion USD and 200 million patients afflicted worldwide, accurate knowledge regarding the pathophysiology, presentation, and diagnosis of the disease is crucial. The role of lipoproteins and their remnants in atherosclerotic vessel occlusion and plaque formation and progression has been long established. This review paper discusses the epidemiology, pathophysiology, and presentation of PAD. PAD has been repeatedly noted to portend to poor cardiovascular and limb outcomes. We discuss major therapeutic avenues for the prevention of major cardiovascular adverse events and major limb adverse events in patients with PAD.