Monocyte Recruitment for Vascular Tissue Regeneration

A strategy to recruit monocytes (MCs) from blood to regenerate vascular tissue from unseeded (cell-free) tissue engineered vascular grafts is presented. When immobilized on the surface of vascular grafts, the fusion protein, H2R5 can capture blood-derived MC under static or flow conditions in a shear stress dependent manner. The bound MC turns into macrophages (Mϕ) expressing both M1 and M2 phenotype specific genes. When H2R5 functionalized acellular-tissue engineered vessels (A-TEVs) are implanted into the mouse aorta, they remain patent and form a continuous endothelium expressing both endothelial cell (EC) and MC specific proteins. Underneath the EC layer, multiple cells layers are formed coexpressing both smooth muscle cell (SMC) and MC specific markers. Lineage tracing analysis using a novel CX3CR1-confetti mouse model demonstrates that fluorescently labeled MC populates the graft lumen by two and four weeks postimplantation, providing direct evidence in support of MC/Mϕ recruitment to the graft lumen. Given their abundance in the blood, circulating MCs may be a great source of cells that contribute directly to the endothelialization and vascular wall formation of acellular vascular grafts under the right chemical and biomechanical cues.

Cell-free vascular grafts that grow with the host

Cell-free small diameter vascular grafts, based on small intestinal submucosa (SIS) functionalized with heparin and vascular endothelial growth factor (VEGF) manufactured and implanted successfully into the arterial system of neonatal lambs, where they remained patent and grew in size with the host to a similar extent and with similar rate as native arteries. Acellular tissue engineered vessels (A-TEV) integrated seamlessly into the native vasculature and developed confluent, functional endothelium that afforded patency. The medial layer was infiltrated by smooth muscle cells, showed no signs of calcification and developed contractile function. The vascular wall underwent remarkable extracellular matrix remodeling exhibiting elastin fibers and even inner elastic lamina within six months. Taken together, our results suggest that VEGF-based A-TEVs may be suitable for treatment of congenital heart disorders to alleviate the need for repeated surgeries, which are currently standard practice.

Implantation of VEGF-functionalized cell-free vascular grafts: regenerative and immunological response

Recently, our group demonstrated that immobilized VEGF can capture flowing endothelial cells (ECs) from the blood in vitro and promote endothelialization and patency of acellular tissue-engineered vessels (A-TEVs) into the arterial system of an ovine animal model. Here, we demonstrate implantability of submillimeter diameter heparin and VEGF-decorated A-TEVs in a mouse model and discuss the cellular and immunologic response. At 1 mo postimplantation, the graft lumen was fully endothelialized, as shown by expression of EC markers such as CD144, eNOS, CD31, and VEGFR2. Interestingly, the same cells coexpressed leukocyte/macrophage (Mϕ) markers CD14, CD16, VEGFR1, CD38, and EGR2. Notably, there was a stark difference in the cellular makeup between grafts containing VEGF and those containing heparin alone. In VEGF-containing grafts, infiltrating monocytes (MCs) converted into anti-inflammatory M2-Mϕs, and the grafts developed well-demarcated luminal and medial layers resembling those of native arteries. In contrast, in grafts containing only heparin, MCs converted primarily into M1-Mϕs, and the endothelial and smooth muscle layers were not well defined. Our results indicate that VEGF may play an important role in regulating A-TEV patency and regeneration, possibly by regulating the inflammatory response to the implants.-Smith, R. J., Jr., Yi, T., Nasiri, B., Breuer, C. K., Andreadis, S. T. Implantation of VEGF-functionalized cell-free vascular grafts: regenerative and immunological response.

Vertebral artery orifice stenosis: a report of 43 cases from northwest iran treated with angioplasty and stenting

More than one quarter of all transient ischemic attacks (TIA's) and ischemic strokes involve tissue supplied by the vertebrobasilar (VB) circulation. Vertebral artery stenotic lesion, particularly at the origin of the vertebral artery, is not uncommon but it is a less studied area. Here we present our endovascular treatment experience in a group of patients with vertebral artery orifice stenosis. We enrolled a group of patients with vertebral artery orifice stenosis who presented with confirmed posterior circulation stroke. Vertebrobasilar insufficiency syndrome was confirmed by imaging studies and clinical findings. Vertebral artery stenosis diagnosed by CT or MR Angiography and confirmed by Conventional and digital subtraction angiography (DSA). Angiography was performed by using of femoral or radial artery approach. From October 2008 to January 2010, forty-three consecutive patients (69.8% men) underwent stent placement for symptomatic vertebral artery orifice stenosis. Mean degree of stenosis was 70.45 +/- 7.455 percent and mean age was 71.65 +/- 7.743 years . In the 22 patients (22/43, 51.16%) stenosis were in left side. In the thirty patients (30/43, 69.6%) there was evidence of atherosclerotic disease in the internal carotid artery and in the 23% contra lateral vertebral artery was involved. There were five different cases with left renal artery stenosis especially in the men with left vertebral artery stenosis. Initial technical success rate was 100%. No cerebrovascular complications or embolic events occurred. Six months control angiography follow-up revealed one patient with stent occlusion and moderate (40%) restenosis in the another patient. According to our finding angioplasty and stenting for vertebral artery orifice stenosis is safe and effective. Patients with vertebral artery orifice disease frequently have coexistent atherosclerotic stenosis in the other major extracranial arteries including carotid and renal arteries.

Instability of IS6110 patterns in multidrug-resistant strains of Mycobacterium tuberculosis

The stability of IS6110 restriction fragment length polymorphism (RFLP) pattern was determined in 31 isolates from patients with multidrug-resistant tuberculosis (MDR-TB). These patients were in actual chains of transmission and they referred to the National Institute of Tuberculosis and Lung Diseases, Tehran, Iran. Susceptibility testing against first- and second-line drugs were performed by the proportional method on Lowenstein-Jensen culture media. Thereafter, DNA fingerprinting by IS6110 with direct repeat (DR) region as a probe was performed by standard protocols. The rate of IS6110 changes was 16%, although, no variation was found in the DR region, in a time-span of 1-63 months. The strains with unstable IS6110 patterns were resistant to all drugs tested, and the majority of them (60%) were collected from HIV-positive patients. The results demonstrated that for a reliable interpretation of strain typing, it is better to use an additional marker along with IS6110 RFLP.