The in vivo performance of small-caliber nanofibrous polyurethane vascular grafts.

BACKGROUND: In a previous in vitro study, we confirmed that small-caliber nanofibrous polyurethane (PU) vascular grafts have favorable mechanical properties and biocompatibility. In the present study, we examined the in vivo biocompatibility and stability of these grafts. METHODS: Forty-eight adult male beagle dogs were randomly divided into two groups receiving, respectively, polyurethane (PU) or polytetrafluoroethylene (PTFE) grafts (n = 24 animals / group). Each group was studied at 4, 8, 12, and 24 weeks after graft implantation. Blood flow was analyzed by color Doppler ultrasound and computed tomography angiography. Patency rates were judged by animal survival rates. Coverage with endothelial and smooth muscle cells was characterized by hematoxylin-eosin and immunohistological staining, and scanning electron microscopy (SEM). RESULTS: Patency rates were significantly higher in the PU group (p = 0.02 vs. PTFE group). During the first 8 weeks, endothelial cells gradually formed a continuous layer on the internal surface of PU grafts, whereas coverage of PTFE graft by endothelial cells was inhomogeneous. After 12 weeks, neointimal thickness remained constant in the PU group, while PTFE group showed neointimal hyperplasia. At 24 weeks, some anastomotic sites of PTFE grafts became stenotic (p = 0.013 vs. PU group). Immunohistological staining revealed a continuous coverage by endothelial cells and an orderly arrangement of smooth muscle cells on PU grafts. Further, SEM showed smooth internal surfaces in PU grafts without thrombus or obvious neointimal hyperplasia. CONCLUSIONS: Small-caliber nanofibrous PU vascular grafts facilitate the endothelialization process, prevent excessive neointimal hyperplasia, and improve patency rates.

[Fabrication of tissue engineered vein containing valve scaffolds].

OBJECTIVE: To fabricate porous biodegradable tissue engineered vein containing valve scaffolds. METHODS: Based on the self-made cast, the tissue engineered vein containing valve scaffolds was fabricated by injection molding plus thermally induced phase separation. Poly (lactic-co-glycolic acid) (PLGA, LA/GA mole ratio 75:25) was used as matrices. Morphological structures and biocompatibility of scaffolds were tested. Cell seeding on scaffold was performed and the mechanic characteristics of cellular constructs evaluated. RESULTS: The scaffold had an inner diameter of 9 mm with a wall thickness of 0.9 mm and the thickness of valves was (0.32 ± 0.04) mm. Scanning electron microscopic (SEM) micrographs showed regular ladder-like porous structures and the average pore size and porosity of scaffolds were 10 - 20 µm and 90%. The PLGA scaffolds were biocompatible. The cellular constructs were tested in vitro, and the valve leaflets were functionally capable of opening and closing when stimulated. CONCLUSION: Based on the self-made cast, the tissue engineered vein containing valve scaffolds can be fabricated by injection molding plus thermally induced phase separation. Further researches are warranted.

Comparison between paclitaxel-coated balloon and standard uncoated balloon in the treatment of femoropopliteal long lesions in diabetics.

Atherosclerotic diseases may include femoropopliteal artery stenosis or occlusion. Percutaneous transluminal angioplasty (PTA) is an effective and minimally invasive treatment strategy for atherosclerotic femoropopliteal artery stenosis/occlusion disease. Balloon angioplasty is a widely used technique in the management of occlusive disease in almost all arterial segments.We enrolled 111 diabetics with long femoropopliteal lesions, among which 54 received PTA with paclitaxel-coated balloon (the Paclitaxel group), and 57 with standard balloon catheters (the Control group).The primary outcome was set as angiographic late lumen loss (LLL) within 6 months; the secondary angiographic outcome was binary restenosis. Clinical outcomes included Rutherford clarification, ankle-brachial index (ABI) and rate of clinically driven target lesion revascularization (TLR). Two groups had similar basal clinical features, angiographic and procedural characteristics. Compared to controls, the Paclitaxel group had a significantly lower 6-month LLL rate, 12-month binary restenosis rate, 12-month TLR, lower Rutherford grades at 3 and 6 months, and higher ABI at 3 months. For all factors which might influence outcomes, fasting blood glucose was negatively correlated with ABI; the blood urea nitrogen (BUN) was positively related with the Rutherford clarification grades. In addition, the coronary heart disease (CHD) and smoking histories were positively correlated with residual stenosis after treatment.Collectively, the paclitaxel-coated balloon angioplasty can yield more favorable angiographic and clinical outcomes than standard uncoated balloon angioplasty, even in the more challenging lesions (the long and occlusive femoropopliteal lesions) in diabetics, when it had a similar safety profile to the traditional balloon. Blood glucose, BUN, CHD, and smoking imply poor curative effects.

[pCKM-mPTH recombinant plasmid therapy for hypoparathyroidism by polycationic liposome-mediated transfection].

OBJECTIVE: To investigate the optimal ratio of polycationic liposome mediated pCKM-mPTH recombinant gene transfer to skeleton cells in the gene therapy of hypoparathyroidism (HPT). METHODS: The protective roles of polycationic liposome to DNA were observed by the DNaseIsensitive test. Liposome-plasmid complex (lipoplexes) with various liposome to plasmid ratio and the naked plasmid were transferred both in vivo and in vitro. The supernatants and serums were collected for measuring parathyroid hormone (PTH) with radioimmunoassay. RESULTS: When the ratio of lipoplexes reached 2:1, there were obviously protective roles to DNA. While it was 3:1, mPTH transgene expressing reached peak which the PTH amount was (16.4 +/- 4.8) pg/10,000 cells/24 h. Furthermore, the amount serum PTH of the HPT model SD rats reached the highest (35.9 pg/ml +/- 2.2 pg/ml) till the concentration of pCKM-mPTH is 20 microg/100 microl with 3:1 ratio of lipoplexes. CONCLUSION: Polycationic liposomes are more effective than naked plasmids for pCKM-mPTH recombinant gene transfer to skeleton cells. The results also indicated that the effect of pCKM-mPTH transferring into muscles might be depended on the optimal ratio and dosage of lipoplexes.

[Assessment of the mechanical properties and biocompatibility of a new electrospun polyurethane vascular prosthesis].

OBJECTIVE: To develop a small-caliber vascular grafts and study its morphologies, mechanical properties and biocompatibility. METHODS: The effects of electrospinning conditions on the microstructure and porosity of the resulting scaffolds were investigated for preparation of a small-caliber (4 mm) polyurethane vascular grafts with optimum microstructures and mechanical properties. The mechanical properties and biocompatibility of the prepared grafts were evaluated. RESULTS: The polyurethane vascular grafts showed a three-dimensional reticular structure consisting of nanofibers, with an average porosity of (51.48∓4.47)% and tensile strength of 5.85 ∓ 0.62 MPa. The grafts provided a better long-term support than e-PTFE graft for endothelial cell growth and endothelialization. CONCLUSION: The polyurethane vascular prosthesis possessed favorable microstructures, excellent mechanical properties and good biocompatibility for potential clinical application.

Intensive statin therapy: a favorable adjunct to the improvement of small-diameter vascular grafts.

To assess the effect of intensive statins therapy on the outcome of small-diameter vascular prosthesis, we investigated whether atorvastatin treatment (30 mg/d) could accelerate the re-endothelialization process and improve the patency rate in a canine infrarenal abdominal aorta-expanded polytetrafluoroethylene (ePTFE) bypass model. Furthermore, we also evaluated the effect of atorvastatin on the migratory and adherent capacity of circulating endothelial progenitor cells (EPCs) in vitro. Improved patency was confirmed by Doppler sonography and arteriography. Histological and scanning electron microscopy illustrated enhanced re-endothelialization process. Treatment with atorvastatin enhanced the circulating pool of EPCs with fortified migratory and adherent capacity. Reverse transcriptase-polymerase chain reaction (RT-PCR) analysis showed that atorvastatin treatment increased endothelial nitric oxide synthase (eNOS) and kinase insert domain receptor (KDR) messenger RNA (mRNA) expression in cultured EPCs and neointima. In conclusion, intensive statin therapy could be considered a favorable option to improve small-diameter vascular graft patency.

Detection of multiple cytokines by protein arrays from cell lysate and tissue lysate.

Previously we demonstrated that multiple cytokines could be simultaneously detected using an antibody-based protein array system with high sensitivity and specificity from conditioned medium and serum. Here, we created a higher density array system to simultaneously detect 35 cytokines from cell lysates and tissue lysates. This assay combines the advantages of the specificity of enzyme-linked immunosorbent assays (ELISA), sensitivity of enhanced chemiluminescence (ECL), and high-throughput of microspot. In this system, capture antibodies dissolved in methanol were spotted onto polyvinylidene difluoride (PVDF) membranes. The membranes were then incubated with tissue lysates or cell lysates. After removing unbound proteins by extensive washing, the membranes were exposed to horseradish peroxidase (HRP)-conjugated antibody(ies). The signals were visualized with an ECL system. High specificity, sensitivity, and accuracy of this approach were demonstrated. This approach can be used in any general laboratory setting without any sophisticated equipment. It should be feasible to extend this concept to develop a high-throughput protein array system. Combining nitrocellulose membrane-based and PVDF membrane-based approaches, the human cytokine array system can be applied to detect multiple cytokine expression from cell lysate, tissue lysate, serum, plasma, and conditioned medium. Future applications of this new approach include direct protein expression profiling, immunological disease diagnostics, and discovery of new biomarkers.