Toru Kuratani

Feasibility, Safety, and Therapeutic Efficacy of Human Induced Pluripotent Stem Cell-Derived Cardiomyocyte Sheets in a Porcine Ischemic Cardiomyopathy Model

Background— Human induced pluripotent stem cell-derived cardiomyocytes (hiPS-CMs) are a promising source of cells for regenerating myocardium. However, several issues, especially the large-scale preparation of hiPS-CMs and elimination of undifferentiated iPS cells, must be resolved before hiPS cells can be used clinically. The cell-sheet technique is one of the useful methods for transplanting large numbers of cells. We hypothesized that hiPS-CM-sheet transplantation would be feasible, safe, and therapeutically effective for the treatment of ischemic cardiomyopathy. Methods and Results— Human iPS cells were established by infecting human dermal fibroblasts with a retrovirus carrying Oct3/4, Sox2, Klf4, and c-Myc. Cardiomyogenic differentiation was induced by WNT signaling molecules, yielding hiPS-CMs that were almost 90% positive for &agr;-actinin, Nkx2.5, and cardiac troponin T. hiPS-CM sheets were created using thermoresponsive dishes and transplanted over the myocardial infarcts in a porcine model of ischemic cardiomyopathy induced by ameroid constriction of the left anterior descending coronary artery (n=6 for the iPS group receiving sheet transplantation and the sham-operated group; both groups received tacrolimus daily). Transplantation significantly improved cardiac performance and attenuated left ventricular remodeling. hiPS-CMs were detectable 8 weeks after transplantation, but very few survived long term. No teratoma formation was observed in animals that received hiPS-CM sheets. Conclusions— The culture system used yields a large number of highly pure hiPS-CMs, and hiPS-CM sheets could improve cardiac function after ischemic cardiomyopathy. This newly developed culture system and the hiPS-CM sheets may provide a basis for the clinical use of hiPS cells in cardiac regeneration therapy.

Long-term results of the open stent-grafting technique for extended aortic arch disease

OBJECTIVE This report elucidates the long-term safety and effectiveness of extended aortic arch replacement with an open stent-grafting technique from our 12 years of experience. METHODS From 1994 to 2004, 126 patients (mean age 67.8 years) with different pathologic conditions of the aortic arch with extension to the descending aorta (57 dissections [acute/chronic = 31/26] and 69 aneurysms) were operated on with an open stent-grafting technique. During deep hypothermic circulatory arrest with selective cerebral perfusion, the stent graft was delivered through the transected proximal aortic arch, and arch replacement with a 4-branched prosthesis was performed. RESULTS Operative mortality within 30 days was 3.2%. Perioperative morbidity included 7 (5.6%) strokes and 8 (6.3%) spinal injuries (paraplegia in 3, transient paraparesis in 5). Sixty-three percent of the patients were extubated within 24 hours. In long-term follow-up (mean 60.4 +/- 36.5 months, maximum 153 months), survival was 81.1%, 63.3%, and 53.7% at 1, 5, and 8 years. Five (3.9%) late endoleaks were observed but treated with successful additional endovascular repair. Freedom from endoleaks was 98.0%, 91.1%, and 91.1% for 1, 5, and 8 years, respectively. CONCLUSION Long-term observation showed safety and good durability of the open stent-grafting technique for aortic arch disease. This technique could be an attractive treatment option for aortic arch aneurysm with distal extension and aortic dissection requiring aortic arch replacement.

Tissue- and Plasma-Specific MicroRNA Signatures for Atherosclerotic Abdominal Aortic Aneurysm

Background Atherosclerotic abdominal aortic aneurysm (AAA) is a progressive, gradual aortic rupture that results in death in the absence of surgical intervention. Key factors that regulate initiation and progression of AAA are unknown, making targeted interventions difficult. MicroRNAs play a fundamental role in atherosclerosis, and atherosclerotic coronary artery disease is characterized by tissue- and plasma-specific microRNA signatures. However, little is known about microRNAs involved in AAA pathology. This study examined tissue and plasma microRNAs specifically associated with AAA. Methods and Results AAA and normal wall tissues were sampled from patients undergoing AAA repair (n=13; mean age, 68±6 years) and aortic valve replacement surgery (n=7; mean age, 66±4 years), respectively. MicroRNA expression was assessed by high-throughput microRNA arrays and validated by real-time polymerase chain reaction for individual microRNAs that showed significant expression differences in the initial screening. MicroRNAs related to fibrosis (miR-29b), inflammation (miR-124a, miR-146a, miR-155, and miR-223), and endothelium (miR-126, let-7 family members, and miR-21) were significantly upregulated in AAA tissue. Significant negative correlations were seen in expression levels of monocyte chemoattractant protein-1 and miR-124a, -146a, and -223; tumor necrosis factor-α and miR-126 and -223; and transforming growth factor-β and miR-146a. Expression of microRNAs, such as miR-29b, miR-124a, miR-155, and miR-223, that were upregulated in AAA tissue was significantly reduced in plasma of patients with AAA (n=23; mean age, 72±9 years) compared to healthy controls (n=12; mean age, 51±11 years) and patients with coronary artery disease (n=17; mean age, 71±9 years). Conclusions The expression of some microRNAs was specifically upregulated in AAA tissue, warranting further studies on the microRNA function in AAA pathogenesis and on the possibility of using a microRNA biomarker for AAA diagnosis.

Mechanisms of symptomatic spinal cord ischemia after TEVAR: insights from the European Registry of Endovascular Aortic Repair Complications (EuREC).

Purpose To test the hypothesis that simultaneous closure of at least 2 independent vascular territories supplying the spinal cord and/or prolonged hypotension may be associated with symptomatic spinal cord ischemia (SCI) after thoracic endovascular aortic repair (TEVAR). Methods A pattern matching algorithm was used to develop a risk model for symptomatic SCI using a prospective 63-patient single-center cohort to test the positive predictive value (PPV) of prolonged intraoperative hypotension and/or simultaneous closure of at least 2 of 4 the vascular territories supplying the spinal cord (left subclavian, intercostal, lumbar, and hypogastric arteries). This risk model was then applied to data extracted from the multicenter European Registry on Endovascular Aortic Repair Complications (EuREC). Between 2002 and 2010, the 19 centers participating in EuREC reported 38 (1.7%) cases of symptomatic spinal cord ischemia among the 2235 patients in the database. Results In the single-center cohort, direct correlations were seen between the occurrence of symptomatic SCI and both prolonged intraoperative hypotension (PPV 1.00, 95% CI 0.22 to 1.00, p=0.04) and simultaneous closure of at least 2 independent spinal cord vascular territories (PPV 0.67, 95% CI 0.24 to 0.91, p=0.005). Previous closure of a single vascular territory was not associated with an increased risk of symptomatic spinal cord ischemia (PPV 0.07, 95% CI 0.01 to 0.16, p=0.56). The combination of prolonged hypotension and simultaneous closure of at least 2 territories exhibited the strongest association (PPV 0.75, 95% CI 0.38 to 0.75, p<0.0001). Applying the model to the entire EuREC cohort found an almost perfect agreement between the predicted and observed risk factors (kappa 0.77, 95% CI 0.65 to 0.90). Conclusion Extensive coverage of intercostal arteries alone by a thoracic stent-graft is not associated with symptomatic SCI; however, simultaneous closure of at least 2 vascular territories supplying the spinal cord is highly relevant, especially in combination with prolonged intraoperative hypotension. As such, these results further emphasize the need to preserve the left subclavian artery during TEVAR.

In situ tissue regeneration using a novel tissue-engineered, small-caliber vascular graft without cell seeding

OBJECTIVE Various types of natural and synthetic scaffolds with arterial tissue cells or differentiated stem cells have recently attracted interest as potential small-caliber vascular grafts. It was thought that the synthetic graft with the potential to promote autologous tissue regeneration without any seeding would be more practical than a seeded graft. In this study, we investigated in situ tissue regeneration in small-diameter arteries using a novel tissue-engineered biodegradable vascular graft that did not require ex vivo cell seeding. METHODS Small-caliber vascular grafts (4 mm in diameter) were fabricated by compounding a collagen microsponge with a biodegradable woven polymer tube that was constructed in a plain weave pattern with a double layer of polyglycolic acid (core) and poly-L-lactic acid (sheath) fibers. We implanted these tissue-engineered vascular grafts bilaterally into the carotid arteries of mongrel dogs (body weight, 20-25 kg). No anticoagulation regimen was used after implantation. We sacrificed the dogs 2, 4, 6, and 12 months (n = 4 in each group) after implantation and evaluated the explants histologically and biochemically. RESULTS All of the tissue-engineered vascular grafts were patent with no signs of thrombosis or aneurysm at any time. Histologic and biochemical examinations showed excellent in situ tissue regeneration with an endothelial cell monolayer, smooth muscle cells, and a reconstructed vessel wall with elastin and collagen fibers. CONCLUSION Our study indicated that this novel tissue-engineered vascular graft promoted in situ tissue regeneration and did not require ex vivo cell seeding, thereby conferring better patency on small-caliber vascular prostheses.

A self-renewing, tissue-engineered vascular graft for arterial reconstruction

OBJECTIVE Various tissue-engineered vascular grafts have been studied to overcome the clinical disadvantages of conventional prostheses. Previous tissue-engineered vascular grafts have generally required preoperative cellular manipulation or use of bioreactors to improve performance, and their mechanical properties have been insufficient. We focused on the concept of in situ cellularization and developed a tissue-engineered vascular graft for arterial reconstruction that would facilitate renewal of autologous tissue without any pretreatment. METHODS The graft comprised an interior of knitted polyglycolic acid compounded with collagen to supply a scaffold for tissue growth and an exterior of woven poly-L-lactic acid for reinforcement. All components were biocompatible and biodegradable, with excellent cellular affinity. The grafts, measuring 10 mm in internal diameter and 30 mm in length, were implanted into porcine aortas, and their utility was evaluated to 12 months after grafting. RESULTS All explants were patent throughout the observation period, with no sign of thrombus formation or aneurysmal change. Presence in the neomedia of endothelialization with proper integrity and parallel accumulation of functioning smooth muscle cells, which responded to vasoreactive agents, was confirmed in an early phase after implantation. Sufficient collagen synthesis and lack of elastin were quantitatively demonstrated. Dynamic assessment and long-term results of the in vivo study indicated adequate durability of the implants. CONCLUSION The graft showed morphologic evidence of good in situ cellularization, satisfactory durability to withstand arterial pressure for 12 postoperative months, and the potential to acquire physiologic vasomotor responsiveness. These results suggest that our tissue-engineered vascular graft shows promise as an arterial conduit prosthesis.

Long-term results of hybrid endovascular repair for thoraco-abdominal aortic aneurysms

OBJECTIVE The treatment of thoraco-abdominal aortic aneurysms (TAAAs) is extremely laborious, due to the surgical complexity of this condition. In particular, postoperative spinal paraplegia poses a severe complication that significantly lowers patients quality of life. In 1997, we devised a hybrid procedure consisting of extended endovascular aortic repair (EVAR) and visceral reconstruction. In this article, we report the long-term results obtained from this procedure. METHODS We conducted 1106 endovascular aortic repairs between 1997 and 2008. Among these, we selected 86 cases of TAAA. The mean patient age was 71.6 years. Preoperative complications included 19 cases of stroke, 22 cases of coronary artery disease (CAD) and 16 cases of chronic obstructive pulmonary disease (COPD). Cerebrospinal fluid drainage was initiated during the operation. We performed bypasses from the aortic bifurcation to abdominal visceral arteries, and deployed stent grafts to exclude the entire TAAA. RESULTS Operative time averaged 386 min. We lost two patients and encountered only one case of graft occlusion. Two patients had acute renal failure, but neither required a tracheostomy. Furthermore, no patients exhibited paraplegia or delayed paraplegia. We observed endoleaks in nine cases, and shrunken aneurysms in 73 cases. Long-term results included survival rates of 94.8%, 85.8%, 80.2% and 66.6% at 2, 5, 8 and 10 years, respectively. Only two patients died from aortic events. Rates of freedom from aortic events were 90.7%, 80.6%, 70.8% and 70.8% at 2, 5, 8 and 10 years, respectively. CONCLUSIONS The hybrid TAAA-repair protocol yielded satisfactory results. Although thorough follow-up is required for visceral bypass, this procedure could become the standard for TAAAs.

Biventricular support using implantable continuous-flow ventricular assist devices

A 34-year-old woman with fulminant myocarditis underwent emergent implant with the Toyobo (Nipro, Osaka, Japan) paracorporeal biventricular assist device (BiVAD). The patient had been stable for 6 months, until she started to develop heart failure symptoms due to severe pulmonary insufficiency. Pulmonary valve closure and BiVAD conversion to implantable rotary pumps was performed. A DuraHeart centrifugal pump (Terumo Heart Inc., Ann Arbor, MI) was used for left ventricular assist, and a Jarvik 2000 axial-flow pump (Jarvik Heart Inc., New York, NY) was used for right ventricular assist. Although strict management was required to balance the flow rates of the two different types of devices, her postoperative course was uneventful and she was discharged home.

Cardiac fibrosis and cellular hypertrophy decrease the degree of reverse remodeling and improvement in cardiac function during left ventricular assist

BACKGROUND This study investigated if the degree of cardiac fibrosis and myocyte size at the time of left ventricular assist device (LVAD) implantation predicts the degree of improvement in cardiac function and sustained recovery after LVAD explantation. METHODS The study included 34 patients who underwent LVAD-off test. LV end-diastolic (LVEDD) and end-systolic diameter (LVESD), LV ejection fraction (LVEF), mean pulmonary artery pressure (mPAP), pulmonary capillary wedge pressure (PCWP), and cardiac index (CI) were measured before LVAD implantation and during LVAD-off test. Myocardial tissue was obtained from the apical core at LVAD implantation. RESULTS The degree of cardiac fibrosis had significant correlations with changes in LVEDD (r = -0.725, p < 0.0001), LVESD (r = -0.800, p < 0.0001), LVEF (r = -0.637, p < 0.0001), mPAP (r = -0.569, p = 0.0010), PCWP (r = -0.463, p = 0.0123), and CI (r = -0.544, p = 0.0015). Myocyte size also had significant correlations with changes in LVEDD (r = -0.386, p = 0.0235), LVESD (r = -0.414, p = 0.0141), and LVEF (r = -0.528, p = 0.0015). The LVAD was successfully removed in 9 patients. The degree of cardiac fibrosis and myocyte size in these patients was significantly smaller compared with the patients who did not undergo LVAD removal. CONCLUSIONS Cardiac fibrosis and myocyte size at the time of LVAD implantation were significant predictors of degree of improvement of cardiac function and the sustained recovery after the LVAD explantation.

Fifteen-year experience with Toyobo paracorporeal left ventricular assist system.

Our 15-year experience of the Toyobo paracorporeal left ventricular assist system (LVAS) at Osaka University Hospital was reviewed. In total, 61 patients underwent Toyobo LVAS implantation from January 1992 to August 2007. Their mean age was 38.1 ± 16.9 years. The etiologies of heart failure were idiopathic dilated cardiomyopathy in 35 patients, ischemic cardiomyopathy in 15, myocarditis in 5, secondary cardiomyopathy in 4, and others in 2. Preoperatively, intubation was required in 41 patients (67.3%), an intra-aortic balloon pump was required in 38 (62.3%), and extracorporeal membrane oxygenation was required in 30 (49.2%). Four patients underwent heart transplantation and 11 underwent LVAS removal. Of those 11 patients, 4 were subjected to emergent removal because of device complications and all of them died. Of the 7 patients that underwent scheduled LVAS removal, heart failure recurred in 2 patients and reimplantation was required. In terms of major device-related complications, cerebral hemorrhage occurred in 16 patients (26.2%), cerebral infarction in 19 (31.1%), mediastinitis in 10 (16.4%), and inflow/outflow cannula exit site infection in 19 patients (31.1%). The actuarial survival rate of the patients operated on in the last 5 years of this study was 66.3% at 6 months and 45.9% at 1 year. Although the survival rate of patients supported by the Toyobo LVAS has recently improved, the morbidity rate is significant. Considering the current severe shortage of heart donors in Japan, it is important to introduce more durable devices with fewer complications and to establish the strategies for using the LVAS as a bridge to recovery.