Project description:Current in vitro models fail in predicting the degradation rate and mode of magnesium (Mg) stents in vivo. To overcome this, the microenvironment of the stent is simulated here in an ex vivo bioreactor with porcine aorta and circulating medium, and compared with standard static in vitro immersion and with in vivo rat aorta models. In ex vivo and in vivo conditions, pure Mg wires were exposed to the aortic lumen and inserted into the aortic wall to mimic early- and long-term implantation, respectively. Results showed that: 1) Degradation rates of Mg were similar for all the fluid diffusion conditions (in vitro static, aortic wall ex vivo and in vivo); however, Mg degradation under flow condition (i.e. in the lumen) in vivo was slower than ex vivo; 2) The corrosion mode in the samples can be mainly described as localized (in vitro), mixed localized and uniform (ex vivo), and uniform (in vivo); 3) Abundant degradation products (MgO/Mg(OH)2 and Ca/P) with gas bubbles accumulated around the localized degradation regions ex vivo, but a uniform and thin degradation product layer was found in vivo. It is concluded that the ex vivo vascular bioreactor provides an improved test setting for magnesium degradation between static immersion and animal experiments and highlights its promising role in bridging degradation behavior and biological response for vascular stent research.Statement of significanceMagnesium and its alloys are candidates for a new generation of biodegradable stent materials. However, the in vitro degradation of magnesium stents does not match the clinical degradation rates, corrupting the validity of conventional degradation tests. Here we report an ex vivo vascular bioreactor, which allows simulation of the microenvironment with and without blood vessel integration to study the biodegradation of magnesium implants in comparison with standard in vitro test conditions and with in vivo implantations. The bioreactor did simulate the corrosion of an intramural implant very well, but showed too high degradation for non-covered implants. It is concluded that this system is in between static incubation and animal experiments concerning the predictivity of the degradation.

Project description:Endovascular stenting presents a promising approach to treat peripheral artery stenosis. However, a significant proportion of patients require secondary interventions due to complications such as in-stent restenosis and late stent thrombosis. Clinical failure of stents is not only attributed to patient factors but also on endothelial cell (EC) injury response, stent deployment techniques, and stent design. Three-dimensional in vitro bioreactor systems provide a valuable testbed for endovascular device assessment in a controlled environment replicating hemodynamic flow conditions found in vivo. To date, very few studies have verified the design of bioreactors based on applied flow conditions and their impact on wall shear stress, which plays a key role in the development of vascular pathologies. In this study, we develop a computationally informed bioreactor capable of capturing responses of human umbilical vein endothelial cells seeded on silicone tubes subjected to hemodynamic flow conditions and deployment of a self-expanding nitinol stents. Verification of bioreactor design through computational fluid dynamics analysis confirmed the application of pulsatile flow with minimum oscillations. EC responses based on morphology, nitric oxide (NO) release, metabolic activity, and cell count on day 1 and day 4 verified the presence of hemodynamic flow conditions. For the first time, it is also demonstrated that the designed bioreactor is capable of capturing EC responses to stent deployment beyond a 24-hour period with this testbed. A temporal investigation of EC responses to stent implantation from day 1 to day 4 showed significantly lower metabolic activity, EC proliferation, no significant changes to NO levels and EC's aligning locally to edges of stent struts, and random orientation in between the struts. These EC responses were indicative of stent-induced disturbances to local hemodynamics and sustained EC injury response contributing to neointimal growth and development of in-stent restenosis. This study presents a novel computationally informed 3D in vitro testbed to evaluate stent performance in presence of hemodynamic flow conditions found in native peripheral arteries and could help to bridge the gap between the current capabilities of 2D in vitro cell culture models and expensive pre-clinical in vivo models.

Project description:AimsIn-stent chronic total occlusion (IS-CTO) represents a unique challenge for percutaneous coronary intervention. Whether the optimal treatment for IS-CTO is angioplasty with paclitaxel-coated balloons (PCBs) or repeat stenting with drug-eluting stents (DESs) is unclear. We aimed to evaluate the long-term clinical outcome of PCB angioplasty and DES repeat stenting for DES IS-CTO.MethodsWe retrospectively included patients with DES IS-CTO who underwent successful PCB angioplasty or DES repeat stenting from January 2016 to December 2019. The primary endpoints were major adverse cardiac events (MACEs), including cardiac death, myocardial infarction, and target lesion revascularization (TLR). Cox proportional hazards model was performed to compare the risk of MACEs between PCB angioplasty and DES repeat stenting, and to further explore the prognostic factors of patients with DES IS-CTO.ResultsA total of 214 patients with DES IS-CTO were enrolled: 78 patients (36.4%) treated with PCB and 136 patients (63.6%) treated with DES respectively. The median follow-up was 1160 days, and MACEs were observed in 28.2% of patients with PCB angioplasty versus 26.5% of patients with DES repeat stenting (P = 0.784), mainly driven by TLR (21.8% vs. 19.9%, P = 0.735). There was no significant difference in the risk of MACEs between the PCB group and the DES group (hazard ratio [HR] 1.25, 95% confidence interval [CI] 0.64-2.46, P = 0.512). Multivariate Cox analysis revealed that chronic kidney disease and ≥ 3 stent layers in the lesion were independent predictors of MACEs, while switching to another antiproliferative drug was an independent protective factor (all P < 0.05).ConclusionsPCB angioplasty was an effective alternative treatment strategy for DES IS-CTO, which had similar long-term outcomes to DES repeat stenting in contemporary practice, but both were accompanied by a high rate of long-term MACEs. Improving the poor prognosis of patients with DES IS-CTO remains a challenge.

Project description:ObjectivesThe objective is to assess the performance of the Eluvia polymer coated drug eluting stent (DES) compared to a bare metal stent (BMS) platform in patients with femoropopliteal arterial disease.MethodsThis is a retrospective, single-center analysis. Patients treated with the Eluvia DES (group Eluvia) or the EverFlex BMS (group BMS) for femoropopliteal disease between January 2013 and December 2019 were included. Primary measure outcome of this analysis was the overall mortality. The PTX specific mortality, the primary patency, the amputation free survival (AFS), and the target lesion revascularization (TLR) rates were additionally evaluated.ResultsA total of 124 patients were treated by BMS deployment, while the Eluvia platform was preferred in 75 subjects. In both groups the majority presented with lifestyle limiting claudication (BMS: 84% vs Eluvia: 73%, p = 0.73). Chronic total occlusions were more frequent in patients treated by BMS (BMS: 71% vs Eluvia: 84%, p = 0.027), whereas the calcification burden (BMS: 81% vs Eluvia: 76%, p = 0.43) and the median lesion length (in mm, IQR) (BMS: 160 (100 to 240) vs Eluvia: 140 (80 to 229), p = 0.17) were comparable. At 24 months, the overall survival (BMS: 93% vs Eluvia: 89%, hazard ratio (HR): 1.20, 95% confidence interval (CI): 0.55 to 2.64, p = 0.64) and the PTX specific survival (BMS: 95% vs Eluvia: 95%, HR: 1.28, 95% CI: 0.41 to 4.02, p = 0.67) did not differ significantly between the two platforms. No significant difference was observed regarding the 24 months primary patency rate (BMS: 66% vs Eluvia: 78%, HR: 0.65, 95% CI: 0.37 to 1.15, p = 0.18), the freedom from TLR (BMS: 83% vs Eluvia: 89%, HR: 0.81, 95% CI: 0.39 to 1.68, p = 0.572), and the AFS (BMS: 93 vs Eluvia: 89%, HR: 1.20, 95% CI: 0.55 to 2.64). The Cox regression analysis revealed a higher mortality risk among patients with chronic limb-threatening ischemia (CLTI) (HR: 3.14, 95% CI: 1.61 to 6.14, p = 0.008), chronic obstructive pulmonary disease (COPD) (HR: 4.65, 95% CI: 2.14 to 10.09, p = 0.001), in octagenerians (HR: 4.40, 95% CI: 1.92 to 10.44, p = 0.005), and in patients not on statins at baseline (HR: 2.44, 95% CI: 1.19 to 4.99, p=0.014).ConclusionsIn this cohort, the use of the Eluvia DES did not increase the risk for mortality compared to BMS deployment. CLTI, COPD, advanced age, and the lack of statin therapy at baseline were associated with a higher risk for death.

Project description:ObjectivesWe sought to develop an ex vivo trachea model capable of producing mild, moderate, and severe tracheobronchomalacia for optimizing airway stent design. We also aimed to determine the amount of cartilage resection required for achieving different tracheobronchomalacia grades that can be used in animal models.MethodsWe developed an ex vivo trachea test system that enabled video-based measurement of internal cross-sectional area as intratracheal pressure was cyclically varied for peak negative pressures of 20 to 80 cm H2O. Fresh ovine tracheas were induced with tracheobronchomalacia by single mid-anterior incision (n = 4), mid-anterior circumferential cartilage resection of 25% (n = 4), and 50% per cartilage ring (n = 4) along an approximately 3-cm length. Intact tracheas (n = 4) were used as control. All experimental tracheas were mounted and experimentally evaluated. In addition, helical stents of 2 different pitches (6 mm and 12 mm) and wire diameters (0.52 mm and 0.6 mm) were tested in tracheas with 25% (n = 3) and 50% (n = 3) circumferentially resected cartilage rings. The percentage collapse in tracheal cross-sectional area was calculated from the recorded video contours for each experiment.ResultsEx vivo tracheas compromised by single incision and 25% and 50% circumferential cartilage resection produce tracheal collapse corresponding to clinical grades of mild, moderate, and severe tracheobronchomalacia, respectively. A single anterior cartilage incision produces saber-sheath type tracheobronchomalacia, whereas 25% and 50% circumferential cartilage resection produce circumferential tracheobronchomalacia. Stent testing enabled the selection of stent design parameters such that airway collapse associated with moderate and severe tracheobronchomalacia could be reduced to conform to, but not exceed, that of intact tracheas (12-mm pitch, 0.6-mm wire diameter).ConclusionsThe ex vivo trachea model is a robust platform that enables systematic study and treatment of different grades and morphologies of airway collapse and tracheobronchomalacia. It is a novel tool for optimization of stent design before advancing to in vivo animal models.

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Design and use of an ex vivo peripheral simulating bioreactor system for pharmacokinetic analysis of a drug coated stent

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