Hybrid approach to deep vein arterialization as an adjunct for patients with severe medial calcinosis.

Patients with no-option chronic limb-threatening ischemia are not candidates for conventional revascularization options and will inevitably require major amputation. Deep venous arterialization (DVA) is a potential option for these patients. A complete endovascular system to perform DVA has recently received great acclaim and US Foor and Drug Administration approval. However, patients with severe tibial medial calcinosis such as those with diabetes or renal failure may not be candidates for this because most endovascular needles cannot penetrate severe calcium. Here we describe a novel hybrid approach to DVA that provided technical success in three patients with end-stage renal disease and severe medial calcinosis.

Local CXCR4 Upregulation in the Injured Arterial Wall Contributes to Intimal Hyperplasia.

CXCR4 is a stem/progenitor cell surface receptor specific for the cytokine stromal cell-derived factor-1 (SDF-1α). There is evidence that bone marrow-derived CXCR4-expressing cells contribute to intimal hyperplasia (IH) by homing to the arterial subintima which is enriched with SDF-1α. We have previously found that transforming growth factor-ß (TGFß) and its signaling protein Smad3 are both upregulated following arterial injury and that TGFß/Smad3 enhances the expression of CXCR4 in vascular smooth muscle cells (SMCs). It remains unknown, however, whether locally induced CXCR4 expression in SM22 expressing vascular SMCs plays a role in neointima formation. Here, we investigated whether elevated TGFß/Smad3 signaling leads to the induction of CXCR4 expression locally in the injured arterial wall, thereby contributing to IH. We found prominent CXCR4 upregulation (mRNA, 60-fold; protein, 4-fold) in TGFß-treated, Smad3-expressing SMCs. Chromatin immunoprecipitation assays revealed a specific association of the transcription factor Smad3 with the CXCR4 promoter. TGFß/Smad3 treatment also markedly enhanced SDF-1α-induced ERK1/2 phosphorylation as well as SMC migration in a CXCR4-dependent manner. Adenoviral expression of Smad3 in balloon-injured rat carotid arteries increased local CXCR4 levels and enhanced IH, whereas SMC-specific depletion of CXCR4 in the wire-injured mouse femoral arterial wall produced a 60% reduction in IH. Our results provide the first evidence that upregulation of TGFß/Smad3 in injured arteries induces local SMC CXCR4 expression and cell migration, and consequently IH. The Smad3/CXCR4 pathway may provide a potential target for therapeutic interventions to prevent restenosis. Stem Cells 2016;34:2744-2757.

Periadventitial drug delivery for the prevention of intimal hyperplasia following open surgery.

BACKGROUND: Intimal hyperplasia (IH) remains a major cause of poor patient outcomes after surgical revascularization to treat atherosclerosis. A multitude of drugs have been shown to prevent the development of IH. Moreover, endovascular drug delivery following angioplasty and stenting has been achieved with a marked diminution in the incidence of restenosis. Despite advances in endovascular drug delivery, there is currently no clinically available method of periadventitial drug delivery suitable for open vascular reconstructions. Herein we provide an overview of the recent literature regarding innovative polymer platforms for periadventitial drug delivery in preclinical models of IH as well as insights about barriers to clinical translation. METHODS: A comprehensive PubMed search confined to the past 15years was performed for studies of periadventitial drug delivery. Additional searches were performed for relevant clinical trials, patents, meeting abstracts, and awards of NIH funding. RESULTS: Most of the research involving direct periadventitial delivery without a drug carrier was published prior to 2000. Over the past 15years there have been a surge of reports utilizing periadventitial drug-releasing polymer platforms, most commonly bioresorbable hydrogels and wraps. These methods proved to be effective for the inhibition of IH in various animal models (e.g. balloon angioplasty, wire injury, and vein graft), but very few have advanced to clinical trials. There are a number of barriers that may account for this lack of translation. Promising new approaches including the use of nanoparticles will be described. CONCLUSIONS: No periadventitial drug delivery system has reached clinical application. For periadventitial delivery, polymer hydrogels, wraps, and nanoparticles exhibit overlapping and complementary properties. The ideal periadventitial delivery platform would allow for sustained drug release yet exert minimal mechanical and inflammatory stresses to the vessel wall. A clinically applicable strategy for periadventitial drug delivery would benefit thousands of patients undergoing open vascular reconstruction each year.

A crosstalk between TGF-ß/Smad3 and Wnt/ß-catenin pathways promotes vascular smooth muscle cell proliferation.

RATIONALE: Endovascular interventions performed for atherosclerotic lesions trigger excessive vascular smooth muscle cell (SMC) proliferation leading to intimal hyperplasia. Our previous studies show that following endovascular injury, elevated TGF-ß/Smad3 promotes SMC proliferation and intimal hyperplasia. Furthermore in cultured SMCs, elevated TGF-ß/Smad3 increases the expression of several Wnt genes. Here we investigate a crosstalk between TGF-ß/Smad3 and Wnt/ß-catenin signaling and its role in SMC proliferation. METHODS AND RESULTS: To mimic TGF-ß/Smad3 up-regulation in vivo, rat aortic SMCs were treated with Smad3-expressing adenovirus (AdSmad3) or AdGFP control followed by stimulation with TGF-ß1 (or solvent). AdSmad3/TGF-ß treatment up-regulated Wnt2b, Wnt4, Wnt5a, Wnt9a, and Wnt11 (confirmed by qRT-PCR and ELISA), and also increased ß-catenin protein as detected by Western blotting. Blocking Wnt signaling using a Frizzled receptor inhibitor (Niclosamide) abolished TGF-ß/Smad3-induced ß-catenin stabilization. Increasing ß-catenin through degradation inhibition (using SKL2001) or by adenoviral expression enhanced SMC proliferation. Furthermore, application of recombinant Wnt2b, Wnt4, Wnt5a, or Wnt9a, but not Wnt11, stabilized ß-catenin and stimulated SMC proliferation as well. In addition, increased ß-catenin was found in the neointima of injured rat carotid artery where TGF-ß and Smad3 are known to be up-regulated. CONCLUSIONS: These results suggest a novel mechanism whereby elevated TGF-ß/Smad3 stimulates the secretion of canonical Wnts which in turn enhances SMC proliferation through ß-catenin stabilization. This crosstalk between TGF-ß/Smad3 and Wnt/ß-catenin canonical pathways provides new insights into the pathophysiology of vascular SMCs linked to intimal hyperplasia.