Nicolas Borenstein

Intra Renal Arterial Injection of Autologous Mesenchymal Stem Cells in an Ovine Model in the Postischemic Kidney

Background and Aims: Acute renal failure (ARF) remains a major healthcare problem. Although modern medical therapy has improved its outcome, the syndrome still has high mortality and morbidity rates [Xue et al.: J Am Soc Nephrol 2006;17:1135–1142]. Recently, stem cell (SC) therapies have been proposed as an alternative for the treatment of ARF on the basis of the damaged cells’ replacement or enhanced recovery or regeneration. The aims of this study were to investigate the engraftment of autologous mesenchymal stem cells (MSC) injected into the renal artery in an ovine model of ischemia reperfusion injury (IRI) and to assess the consequence of the delay between injury and cell transplantation on the engraftment. Material and Methods: MSC were transplanted in animals submitted to IRI or in healthy animals not submitted to IRI. Sheep with IRI were grafted at two different time points after injury. Unilateral renal IRI was performed by percutaneous transluminal placement of a balloon catheter in the renal artery. MSC were isolated from bone marrow, cultured, labeled and injected into the renal artery. Results: All ewes showed renal engraftment by MSC, both in tubules and glomeruli. MSC expressed tubular epithelial cell markers and podocyte phenotype. There was a significant increase of engraftment of tubules by MSC when cells were injected early after injury indicating that the delay for cell transplantation after ischemic insult should be short. Conclusions: This is the first report of intra-arterial autologous transplantation of MSC in the kidney, resulting in a successful engraftment into tubular and glomerular structures. The results strongly suggest that the optimal time window for stem cell therapy is during the early phase of the ischemic injury.

Noncultured, Autologous, Skeletal Muscle Cells Can Successfully Engraft Into Ovine Myocardium

Background There is compelling evidence showing that cellular cardiomyoplasty can improve cardiac function. Considering the potential benefit of using noncultured muscle cells (little time, lower cost, reduced risk of contamination), we investigated the feasibility of grafting cells obtained directly after enzymatic dissociation of skeletal muscle biopsies into ovine myocardium. We hypothesized that those noncultured muscle cells would engraft massively. Methods and Results Autologous, intramyocardial skeletal muscle cell implantation was performed in 8 sheep. A skeletal muscle biopsy sample (≈10 g) was explanted from each animal. The sheep were left to recover for ≈3 hours and reanesthetized when the cells were ready for implantation. A left fifth intercostal thoracotomy was performed, and 10 epicardial injections of the muscle preparation (between 10 and 20 million cells) were carried out. All sheep were euthanized 3 weeks after myocardial implantation. Immunohistochemistry was performed with monoclonal antibodies to a fast skeletal isoform of myosin heavy chain. Skeletal myosin heavy‐chain expression was detected in all slides at 3 weeks after implantation in 8 of 8 animals, confirming engraftment of skeletal muscle cells. Massive areas of engraftment (from 2 to 9 mm in diameter) or discrete loci were noted within the myocardial wall. Conclusions Our results indicate that noncultured skeletal muscle cells can successfully and massively engraft in ovine myocardium. Thus, avoiding the cell culture expansion phase is feasible and could become a promising option for cellular cardiomyoplasty. (Circulation. 2003;107:3088‐3092.)

An ovine model of chronic heart failure: echocardiographic and tissue Doppler imaging characterization.

Abstract  Background and aim of the study: Heart failure in the western world is a major health‐care issue. In order to validate novel surgical or pharmacological treatments, reproducible animal models of left ventricular dysfunction are necessary. In the current study, we report our data and experience with a model of toxin‐induced heart failure in the sheep. Methods: Sequential intracoronary injections of doxorubicin (0.75 mg/kg) were carried out every 2 weeks until standard echocardiographic and tissue Doppler imaging detection of myocardial systolic dysfunction. The animals were assessed 1 month later and harvested. Indices of cardiac function from baseline to last day of protocol were recorded and their differences were evaluated by a Wilcoxon rank test for paired data. Results: Ten sheep received 2.5 ± 0.7 intracoronary injections of a cumulative dose of 88.8 ± 25 mg/m2 doxorubicin. All available parameters demonstrated signs of severe cardiac dysfunction with statistical significance. All hearts demonstrated severe histological lesions, some of which were consistent with doxorubicin‐induced toxicity. Conclusions: The present study shows that this ovine model is reproducible and stable. It can therefore be relevant to the study of chronic heart failure. It will be incorporated in our future studies concerning novel treatments (such as cell therapy) of nonischemic dilated cardiomyopathy.

Expandable Right Ventricular-to-Pulmonary Artery Conduit: An Animal Study

This study was performed to assess a new vascular stent graft as an expandable valved conduit for right ventricular outflow tract (RVOT) reconstruction in sheep. Conduits were constructed by sewing an 18-mm valved conduit inside a stent. Crimped to 16 mm, they were implanted either under or without extracorporeal circulation in seven (group A) and in five (group B) sheep, respectively. Six weeks and 3 mo after their insertion, conduits were dilated intraluminally. A valved stent was implanted percutaneously into conduits before they were killed. Two animals from group A recovered normally, whereas five animals had a complicated postoperative course. In group B, one died acutely due to kinking of the conduit. Balloon dilatations were performed in all surviving animals. First dilatations had a slight impact on valvular function in all animals but one, whereas second dilatations led to significant PR in all. Transcatheter valve implantation was performed successfully. When animals were killed, no bleeding was found around the surgically implanted device. In conclusion, we designed a biologic valved conduit for RVOT reconstruction that can be dilated sequentially to follow animal growth. This new device can have tremendous applications in children with congenital heart diseases involving the RVOT.

Unambiguous Identification of Implanted Cells After Cellular Cardiomyoplasty: A Critical Issue

To the Editor: In their article describing cell implantation in the myocardium of rats, Davani et al1 stress the attention on integration of the transplanted syngenic mesenchymal progenitor cells within myocardial architecture and on their differentiation into smooth muscle and endothelial cells. Their conclusions are based on experimental work using 4′,6-diamidino-2-phenylindole (DAPI) as a cell marker. They raise the legitimate concern of false-negative cells resulting from the dilution of the marker on cell proliferation. We think, however, that the occurrence of false-positive is also a concern with this type of cell labeling. Our group has conducted research on an autologous muscle cell grafting procedure in canine urethra as well as in ovine myocardium. To validate the best tools for non-genetic cell labeling, we performed in vitro and in vivo assessment of chemical fluorescent markers, one of which was DAPI (Sigma). Cells were marked with 50 μg/mL of DAPI during 30 minutes and then washed off 3 times to remove unbound DAPI. Those cells were suspended in Dulbecco’s Modified Eagle Medium and destroyed through 3 rounds of temperature variations (from −160°C to 80°C). One hundred percent cellular mortality was obtained. The dead cells (30 million cells) were then poured onto one Petri dish containing adherent muscle cells (1 million cells …

A new self-expandable transcatheter aortic valve for transapical implantation: feasibility in acute and chronic animal experiments.

Abstract Objectives. Transcatheter aortic valve implantation (TAVI) is currently expanding worldwide, however all available prostheses share some fundamental design drawbacks. We investigated the feasibility, safety and hemodynamic performance of the innovative transapical Acurate TA™ self-expandable device, which has the unique advantage of offering anatomically correct self-alignment within the aortic root. Design. Transapical TAVI was performed in six acute swine and six chronic sheep procedures, with follow-up of 7, 14, 21, 28, 60 and 90 days. TAVI was performed under TEE and angiographic guidance without rapid pacing. Results. A partial sternotomy approach was used to access the LV-apex. All valve implantations were performed as planned and all animals survived the implantation procedure. After deployment, no migration, embolization or coronary obstruction was observed during the observation period. Intraoperative TEE examination identified no signs of intravalvular leakage or valve dysfunction. Transvalvular mean pressure gradients were 5.4 ± 2.2 mmHg decreasing during follow-up (1.6 ± 0.8 mmHg, 1.8 ± 0.8 mmHg, 1.3 ± 0.2, 1.8 ± 0.7 mmHg, 1.6 ± 0.8 mmHg), with a slight increase atday 90 (4.0 ± 2.4 mmHg, P < 0.05). Macroscopic examination at necropsy showed correct anatomical positioning of the valve stent without any signs of structural valve deterioration. Conclusions. These first results of the innovative self-expandable transapical ACURATE TA™ device explore the feasibility and safety of anatomically correct off-pump implantation with optimal hemodynamic results.

Echoguided closed commissurotomy for mitral valve stenosis in a dog

Surgical treatment of mitral stenosis (MS) usually consists of open mitral commissurotomy (MC) or percutaneous balloon MC, which require a cardiopulmonary bypass or transseptal approach, respectively. We describe here the first surgical management of congenital MS in a dog using a less invasive procedure, a surgical closed MC under direct echo guidance. A 5-year-old female Cairn terrier was referred for ascites, weakness, and marked exercise intolerance for 2 months, which was refractory to medical treatment. Diagnosis of severe MS associated with atrial fibrillation (AF) was confirmed by echo-Doppler examination and electrocardiography. Poor response to medical treatment suggested a corrective procedure on the valve was indicated. However, due to the cost and high mortality rate associated with cardiopulmonary bypass, a hybrid MC was recommended. A standard left intercostal thoracotomy was performed and three balloon valvuloplasty catheters of differing diameters were sequentially inserted through the left atrium under direct echo guidance. Transesophageal echocardiography revealed a 62% reduction in the pressure half-time compared to the pre-procedure. Thirteen months after surgery the dog is still doing well with resolution of ascites and a marked improvement of most echo-Doppler variables.

Toward the development of a fully elastic mitral ring: Preliminary, acute, in vivo evaluation of physiomechanical behavior

OBJECTIVES The optimal repair of functional mitral regurgitation is still debated. No device is able to simultaneously abolish mitral regurgitation and replicate natural mitral annular dynamics. We have tested a fully elastic mitral ring in an acute animal study with the purpose of evaluating (1) ring design and implantation technique, (2) elastic performance, and (3) acute effects on the native mitral annulus. METHODS Ten healthy sheep underwent surgical implantation of mitral devices, the elastic component of which is represented by a helicoid metallic spring. Preimplantation and postimplantation echocardiographic parameter measurements to evaluate annular dynamics and ventricular function comprise mitral annular motion, systolic tissue Doppler imaging peak wave, transmitral pressure gradient, peak transmitral flow velocity, and ejection fraction. Postimplantation angiographic analysis allowed measurement of the mitral annular area and perimeter variations by means of segmentation of the radiopaque mitral device contour. RESULTS No significant difference in terms of ejection fraction (P = .13) and systolic tissue Doppler imaging peak wave (P = .87) was found before and after implantation. Mitral annular motion (1.16 cm) was preserved. The percentage of systolic annular reduction derived from angiographic analysis was 14.1% (range, 7.7%-19.7%) in terms of area and 7.2% (range, 4.9%-10.0%) in terms of perimeter. CONCLUSIONS A mitral elastic ring, implantable by using a standard technique, acutely preserves mitral annular dynamics, allowing area and perimeter changes. Further chronic study is needed to verify the biocompatibility and durability of the device.

Successful Treatment of a Congenital Pulmonic Valvular Stenosis in a Snow Leopard (Uncia uncia) by Percutaneous Balloon Valvuloplasty

Abstract A 3-yr-old intact female snow leopard (Uncia uncia) was evaluated for progressive apathy, lethargy, and decreased appetite. Cardiac auscultation revealed a left basal grade IV/VI systolic ejection murmur, and an echocardiogram confirmed a severe pulmonic valvular stenosis (pressure gradient of 98 mm Hg). The lesion was managed by balloon valvuloplasty, resulting in a marked pressure gradient reduction (30 mm Hg). The cat recovered well, and clinical signs resolved. This is the first description of a pulmonary valve stenosis and management with balloon valvuloplasty in a wild felid.

Surgical Treatment of Cor Triatriatum Sinister in a Cat Under Cardiopulmonary Bypass.

OBJECTIVE To report the surgical repair of cor triatriatum sinister (CTS) incorporating heart-beating cardiopulmonary bypass (CPB) in a cat. STUDY DESIGN Clinical case report. ANIMAL Fourteen-month-old, 5.9-kg male castrated Maine Coon cat. MATERIALS AND METHODS The cat had a 3 month history of inappetance, weight loss, and recurrent pulmonary edema. CTS with severe systolic pulmonary arterial (SPA) hypertension (124 mm Hg) was diagnosed by 2D echocardiography, color flow and continuous wave Doppler modes, and left atrial and pulmonary angiography. Surgery was performed through a left intercostal thoracotomy. CPB was initiated and the heart was kept beating. The left atrial appendage was opened and the intra-atrial membrane was excised. RESULTS After 48 hours, the cat was doing well. Reduced SPA pressure (52 mm Hg) with decreased right heart enlargement was observed on ultrasound examination and the cat was discharged 6 days after surgery with oral antibiotics for 10 days, aspirin, and furosemide. Four months after surgery, the cat presented with increased activity and weight gain and was completely asymptomatic. Transthoracic echocardiography showed a marked improvement of all echo-Doppler variables with disappearance of SPA hypertension (24 mm Hg). Four years after surgery, the cat was still doing well with no recurrence of clinical signs despite the lack of medical treatment. CONCLUSION CTS in the cat may be successfully treated by surgery facilitated by use of CPB leading to early and long-term substantial improvement in clinical status and cardiac function. CTS can safely be repaired under CPB in cats.