Saint Joseph’s Translational Research Institute

Microvascular obstruction (MVO) and "no-reflow phenomenon" (NRP) remain barriers to optimal tissue perfusion after percutaneous coronary intervention (PCI). The purpose of this study was to develop, characterise, and test an adenosine-eluting guidewire (Adenowire) for coronary vasodilation. Utilising polyurethane chemistry, we developed a non-toxic pentameric form of adenosine (PA) that can be coated onto guidewires (Adenowire) and that allows continuous elution of adenosine into the distal vascular bed during PCI. We characterised PA with Fourier transform infrared spectroscopy, NMR and MALDI time-of-flight mass spectrometry, established its stability by calorimetry, and confirmed its safety by extensive toxicological testing. Adenowires reliably released adenosine in vitro over 60 minutes. In pigs, insertion of an Adenowire into the left circumflex or left anterior descending coronary artery resulted in immediate and sustained (40 minutes) vasodilation. Electron microscopy demonstrated smooth thin coating of the terminal portion of guidewires and showed lack of fibrin or platelet adhesion to the Adenowire after in vivo use. Since guidewires are the first devices to cross a culprit lesion, Adenowires would prophylactically medicate vascular beds with adenosine at the target site without the need for additional manipulations by the interventionalist.

Background: Heart failure (HF) is the leading cause of mortality in United States. Animal models used to test novel HF therapeutics are inadequate as pathological features of human HF are not replicated. Available large-animal swine myocardial ischemia (MI) models mimic human HF; however, do not achieve ejection fractions (EF) less than 40%. Objective: We sought to develop a reproducible swine MI model with EF below 35%. Methods: Yucatan miniature pigs (n=18) were anesthetized, catheterized and collagen suspension (COL) of microfibrillar hemostat (INSTAT MCH, Ethicon) mixed in contrast and saline solution was injected into the left anterior descending coronary artery (LAD) under fluoroscopic guidance. COL injections started distally and filled side branches during catheter retraction. Complete transient LAD occlusion was confirmed at 2hrs by coronary angiography. Cardiac function was evaluated at 3mos using a 1.5T MRI System (Siemens Magnetom Avanto). LV volumes at end systole (LVESD) and diastole (LVEDD), EF, wall thickness (WT) in area at risk (AAR) and normal zones (NZ) were calculated. Uninjected Yucatan pigs (n=3) served as controls. Results: Twelve of 18 pigs survived COL infarction. At 3mos, EF was reduced in COL injected pigs compared to control (27.0±2.3 vs. 61.6±1.3%, respectively, P<0.001). LVESV and LVEDV were 4- and 2-fold higher and WT in AAR and NZ were reduced 6- and 2-fold, respectively in COL injected compared to controls. Conclusions: A reproducible large animal model of MI was produced by catheter based LAD collagen delivery resulting in EFs below 35% and progression to HF. By closely resembles human HF, it a highly useful for testing potential HF therapies.

Persufflation (PSF; gaseous oxygen perfusion) is an organ preservation technique with a potential for use in donor heart preservation. Improved heart preservation with PSF may improve outcomes by maintaining cardiac tissue quality in the setting of longer cold ischemia times and possibly increasing the number of donor hearts available for allotransplant. Published data suggests that PSF is able to extend the cold storage times for porcine hearts up to 14 hours without compromising viability and function, and has been shown to resuscitate porcine hearts following donation after cardiac death. This review summarizes key published work on heart PSF, including prospective implications and future directions for PSF in heart transplantation. We emphasize the potential impact of extending preservation times and expanding donor selection criteria in heart allotransplant. Additionally, the key issues that need to be addressed before PSF were to become a widely utilized preservation strategy prior to clinical heart transplantation are summarized and discussed.

The vast majority of arteriovenous grafts (AVG) have been constructed using expanded polytetrafluoroethylene (ePTFE). While ePTFE grafts have the advantage of being relatively inexpensive and easy to manufacture, distribute, ship, and store, their primary patency rates are disappointing when compared with the native AVF. Though use of arteriovenous fistulas (AVF) in the United States has increased substantially, approximately 25% of hemodialysis patients continue to use AVG as their vascular access. We present here a comprehensive review of biological grafts and their use in hemodialysis vascular access. In this review, we discuss the use of synthetics and then explore the evolution of biological grafts over the past 20 years, their clinical impact, and future challenges in widespread clinical use in hemodialysis patients. Provided are in depth descriptions of currently used nonbiological arteriovenous grafts and the recent approaches in increasing the patency of synthetic grafts. Recent technological advances using tissue-engineered AVGs have shown promise for patients receiving hemodialysis and their potential to provide an attractive, viable option for vascular access have been discussed.

This study was conducted as a controlled, prospective investigation to show the safety and efficacy of a polyvinyl alcohol (PVA) device in a sheep model. To evaluate the ability of a permanent PVA hydrogel barrier to reduce the risk of potential vessel damage during anterior vertebral revision surgery, to provide a nonadhesive barrier at the surgical site, and to create a surgical revision plane of dissection. The development of scar tissue and adhesions presents a significant postoperative problem in spine surgery, where adhesion involvement of overlying structures can cause pain, neurovascular complications, and present a difficult surgical environment during revisions. The devices were implanted onto the ventral surface of exposed lumbar intervertebral discs using an anterolateral approach. One disc separated from the study site was also exposed to serve as a control. Three sheep each were then evaluated with an explant procedure at 30 and 90 days. Extensive sampling was undertaken to evaluate gross anatomic, micropathologic, and biochemical environments and properties of the device. The structural properties and appearance of the device remained intact at both 30 and 90 days. The material remained flexible, hydrophilic, and soft, without visible resorption or decomposition. The material was well tolerated by the animal, with minimal histologic signs of inflammation or rejection. Tissue planes were easily able to be localized by the surgeon attempting to locate the prior surgical site at the time of resection. The PVA vessel shield effectively protected the structures overlying the sheep spine during revision, providing a clear dissection plane for resection at repeat surgery. The overlying structures separated from the previous surgical site with no adhesion, and allowed safe separation of adjacent tissues without the use of sharp dissection.

Abstract Reconstruction of the pulmonary valve and outflow tract is frequently needed to repair congenital defects. Current substitutes lead to graft failure and reoperation due to calcification, shrinkage, progressive insufficiency or transvalvular gradients, and relative growth of the patient compared to the valve. CorMatrix extracellular matrix (ECM), derived from decellularized, non-crosslinked small intestine submucosa (SIS) is used for general cardiac repairs and regenerates into normal cardiac tissue with growth potential. Previously, we showed that an ECM pulmonary valve leaflet remodeled into a neo-leaflet histologically similar to native valve architecture. In this study we used an ECM valved conduit for pulmonary valve replacement in an ovine model to demonstrate its potential to remodel into native tissue. A trileaflet valved conduit was produced from CorMatrix ECM sutured into a tube then intussuscepted to form a tube within a tube. At three equidistant points the inner tube was sutured to the outer tube forming three leaflets to guide unidirectional flow with physiologic opening and closing mechanics. Under cardiopulmonary bypass the ovine pulmonary valve and pulmonary artery section was removed and replaced with the ECM valved conduit. Valve function was evaluated by echocardiography post-operatively and at bi-monthly intervals until euthanasia at 3, 5, 8, and 12 months. Histological evaluation included H and E, Movat pentachrome, von Kossa, anti-CD31, and anti-eNOS. Our echocardiography results show that a pulmonary valve constructed from ECM opens and closes completely without regurgitation or stenosis for 12 months. Grossly, explanted valves appeared similar to native valves and were remodeling after 3 months with further progression to native morphology after 5, 8 and 12 months. Histological examination showed diffuse cellular infiltration by 3 months. At 5 months, collagen organization was increased and glycosaminoglycans were distributed throughout the middle of the leaflet. At 3 months, SEM and eNOS staining demonstrated a confluent and functional endothelial lining on the pulmonary artery and hinge regions of the valve. At 5 months, this lining extended to the center of the leaflet with confluent areas at the leaflet tip. At 8 and 12 months, a tri-layered structure similar to native valve architecture was demonstrated histologically by a Movat stain with a confluent endothelial lining demonstrated by eNOS and CD31 staining. The von Kossa stain showed an absence of calcific deposits at all time points except occasionally at the suture. These results demonstrate the potential of a CorMatrix ECM pulmonary valve to remodel into endothelialized tissue that is indistinguishable from the host’s native valve both grossly and histologically. Such a regenerated valve would be expected to improve patient outcomes since it remodels into native tissue with growth potential.

Background: Aging is associated with increased mortality following acute myocardial infarction (AMI). Early cell therapy clinical trials for AMI have shown a modest improvement in cardiac function. Previous evidence suggest that B cells may be protective in tissue injury. Our initial studies showed that intramyocardial delivery of bone marrow derived B cells improves cardiac function in young rats. Aim: In this study, we determined the effect of B cell therapy in aged animals subjected to AMI using a clinically relevant protocol. Methods: Human PB B cells were isolated from buffy coats using CD19+ selection. Young (8-10wks) and aged (10-12mos) athymic rats had baseline echocardiography then coronary artery ligation (d1). At d7, rats had repeat echocardiography and received 1×10 7 B cells or vehicle intravenously. At d9 and d21, rats underwent follow-up echocardiography. Explanted hearts were measured for infarct size and B cell localization was determined in infarcted aged rat hearts after d8 in a subset of animals by IHC. Results: Fractional ventricular diameter shortening (FS) decreased at d7 compared to baseline in young (27.9 ±0.9 vs. 55.6±0.6%, P <0.001) and aged (31.6±0.9 vs. 53.4±0.5%, P <0.001) rats. At d9, FS was higher in B cell compared to control treated aged rats (44.9±2.6 vs. 29.3±3.0%, P <0.001). FS was minimally changed in B cell compared to control treated young rats (37.3±3.3 vs. 31.2±3.5%, P =NS). At d21, FS was higher in aged rats receiving B cells compared to controls (38.6±2.2 vs. 30.0±2.6%, P <0.001) and trended higher in B cell treated young rats compared to control (34.1±1.8 vs. 28.0±2.6%, P =0.058). FS was higher in aged rats receiving B cells stored for 1.5hrs at room temperature compared to freshly prepared B cells (35.1±3.2% vs. 27.1±2.4%, P =0.035). Infarct size was smaller in B cell treated aged rats compared to controls (12.9±2.3 vs. 22.4±2.4% LV, P =0.010); no difference in infarct size was detected in young rats. B cells were detected in the infarct of aged rats at d8. Conclusion: These data support that intravenous delivery of peripheral blood B cells is efficacious in improving cardiac function and limiting infarct size in aged rats, an experimental model more relevant to clinical population.

Background: Paclitaxel-Coating balloon (PCB) has shown efficacy for treatment of coronary artery disease. Optical coherence tomography (OCT) is a promising endovascular imaging devise and has been reported to have a high correlation with histomorphometric measurement. However, the association of in-stent stenosis (ISR) by OCT and histopathology response is still not fully addressed. The current study was designed to compare the OCT and histopathological findings following PCB treatment in a porcine ISR model. Materials and Methods: Thirty-two coronary arteries (LAD: n=12, LCX: n=11, RCA: n=9) of 24 Yorkshire pigs were assigned to two (2) groups randomly. PCB (SeQuent, length 20mm, n=16) or non-coating balloon (NCB, length 20mm n=16) were inflated for 60 seconds with B:A 1.2:1 followed by BMS (length 12mm) implantation (S/A 1.5:1) within the target region. At 28 days, animals underwent OCT and histopathology evaluation. Results: There were no significant differences between groups among parameters measured by OCT. The thickness of neointimal hyperplasia on stent strut and the percent of ISR were 585 ± 277 μ m, 46.8 ± 19.0 % for PCB, and 661 ± 237 μ m, 52.4 ± 15.3 % for NCB (p=NS, respectively). However, inflammation (PEB: 3.40 ± 0.84, NCB: 2.27 ± 1.18, p=0.003) and fibrin deposition scores (PCB: 2.31 ± 0.93, NCB: 0.81 ± 0.86, p<0.001) were significantly higher in PCB compared to NCB. The OCT ISR% was positively correlated with inflammation score (PCB: r=0.62, and NCB: r=0.85; p<0.05 respectively). Interestingly, fibrin deposition score only in PCB was negatively correlated with the OCT ISR% (r=-0.68, p=0.005). OCT also showed an uncovered (33.3%) and insufficient non-uniformed neointima (13.3%) in PCB group (p=0.008 vs NCB). Conclusions: OCT can be used as a valuable imaging tool to evaluate vessel wall histopathological changes in vivo. The higher inflammation and fibrin deposition scores in PCB may indicate a delayed healing response in the current experimental setting.

Dacron® (polyethylene terephthalate) and Goretex® (expanded polytetrafluoroethylene) vascular grafts have been very successful in replacing obstructed blood vessels of large and medium diameters. However, as diameters decrease below 6 mm, these grafts are clearly outperformed by transposed autologous veins and, particularly, arteries. With approximately 8 million individuals with peripheral arterial disease, over 500,000 patients diagnosed with end-stage renal disease, and over 250,000 patients per year undergoing coronary bypass in the USA alone, there is a critical clinical need for a functional small-diameter conduit [Lloyd-Jones et al., Circulation 2010;121:e46–e215]. Over the last decade, we have witnessed a dramatic paradigm shift in cardiovascular tissue engineering that has driven the field away from biomaterial-focused approaches and towards more biology-driven strategies. In this article, we review the preclinical and clinical efforts in the quest for a tissue-engineered blood vessel that is free of permanent synthetic scaffolds but has the mechanical strength to become a successful arterial graft. Special emphasis is given to the tissue engineering by self-assembly (TESA) approach, which has been the only one to reach clinical trials for applications under arterial pressure.