What Went Wrong with VEGF-A in Peripheral Arterial Disease? A Systematic Review and Biological Insights on Future Therapeutics

PEGylation of Human Vascular Endothelial Growth Factor

Vascular endothelial growth factor A-165 (VEGF-A165) positively modulates neointimal hyperplasia, lumen stenosis, and neovascularization. One challenge for the use of VEGF-A165 for potential therapy is its short serum half-life. Therefore, we are designing VEGF-A165 bioconjugates carrying polyethylene glycol (PEG). The purity of the recombinantly expressed human VEGF-A165 exceeded 90%. The growth factor had a half-maximal effective concentration of 0.9 ng/mL (EC50) and induced tube formation of human umbilical vein endothelial cells. PEGylation was conducted by Schiff base reaction followed by reductive amination. After purification, two species were obtained, with one or two PEG attached per VEGF-A165 dimer. Both resulting bioconjugates had a purity exceeding 90%, wild-type bioactivity, and increased hydrodynamic radii as required for prolonging the half-life.

A review of the current state in neointimal hyperplasia development following endovascular intervention and minor emphasis on new horizons in immunotherapy

Endovascular strategies play a vital role in the treatment of peripheral arterial disease (PAD). However, luminal loss or restenosis after endovascular intervention remains a significant challenge. The main underlying mechanisms are negative vascular remodeling and elastic recoil in balloon angioplasty. During stenting, the main reason for this complex is neointimal proliferation. Endothelial cell injury due to endovascular intervention initiates a series of molecular events, such as overexpression of growth factors, cytokine secretion, and adhesion molecules. These induce platelet activation and inflammatory processes, which trigger the proliferation and migration of vascular smooth muscle cells into the intima, resulting in neointimal hyperplasia. During this process, PAD progression is mainly caused by chronic inflammation, in which macrophages play a central role. Of the current strategies, drug release interventions aim to suppress restenosis using antiproliferative drugs, such as sirolimus and paclitaxel, during drug release. These drugs inhibit vascular reendothelialization and reduce late in-stent restenosis. For this reason, immunotherapy can be considered an important alternative. Interventions that polarize macrophages to the M2 subtype are particularly important, as they shape the immune response in an anti-inflammatory direction and contribute to tissue repair. However, there are several challenges to overcome, such as localizing antiproliferative or polarizing agents only to areas of vascular injury. This review discusses, based on the early study observations, immunotherapeutic approaches to prevent restenosis after endovascular intervention for the treatment of PAD.

The Concentration of Pro- and Antiangiogenic Factors in Saliva and Gingival Crevicular Fluid Compared to Plasma in Patients with Peripheral Artery Disease and Type 2 Diabetes

Several studies have investigated various biomarkers in relation to peripheral artery disease (PAD) for disease stratification and early-onset detection. In PAD, angiogenesis is required for tissue restoration and tissue perfusion. Considering changes in angiogenesis in patients with PAD, angiogenic factors could be explored as one of the new prognostic molecules. In recent studies, saliva and gingival crevicular fluid (GCF) have gained recognition as new, easily obtained diagnostic materials. This study aimed to compare the levels of selected circulating angiogenic factors (VEGF-A, PDGF-BB, and ANG-1) in unstimulated whole saliva (WS) and GCF versus plasma at three points in time to find possible correlations between their concentrations among patients with PAD and diabetes type 2 in 32 patients with Rutherford stages 5 and 6. A significant positive correlation has been demonstrated between circulating PDGF-BB levels in GCF and plasma. In most cases, comorbidities do not have an impact on the change in general correlation for the whole group. Our results clearly showed that GCF could be a good source for PDGF assessment. However, future studies with a larger number of subjects are warranted to confirm this finding and identify the most accurate angiogenic biomarkers in saliva or GCF that could be applied in clinical practice.

Muscle progenitor cells are required for skeletal muscle regeneration and prevention of adipogenesis after limb ischemia

Skeletal muscle injury in peripheral artery disease (PAD) has been attributed to vascular insufficiency, however evidence has demonstrated that muscle cell responses play a role in determining outcomes in limb ischemia. Here, we demonstrate that genetic ablation of Pax7+ muscle progenitor cells (MPCs) in a model of hindlimb ischemia (HLI) inhibited muscle regeneration following ischemic injury, despite a lack of morphological or physiological changes in resting muscle. Compared to control mice (Pax7WT), the ischemic limb of Pax7-deficient mice (Pax7Δ) was unable to generate significant force 7 or 28 days after HLI. A significant increase in adipose was observed in the ischemic limb 28 days after HLI in Pax7Δ mice, which replaced functional muscle. Adipogenesis in Pax7Δ mice corresponded with a significant increase in PDGFRα+ fibro/adipogenic progenitors (FAPs). Inhibition of FAPs with batimastat decreased muscle adipose but increased fibrosis. In vitro, Pax7Δ MPCs failed to form myotubes but displayed increased adipogenesis. Skeletal muscle from patients with critical limb threatening ischemia displayed increased adipose in more ischemic regions of muscle, which corresponded with fewer satellite cells. Collectively, these data demonstrate that Pax7+ MPCs are required for muscle regeneration after ischemia and suggest that muscle regeneration may be an important therapeutic target in PAD.