3D Imaging Reveals Complex Microvascular Remodeling in the Right Ventricle in Pulmonary Hypertension.

BACKGROUND: Pathogenic concepts of right ventricular (RV) failure in pulmonary arterial hypertension focus on a critical loss of microvasculature. However, the methods underpinning prior studies did not take into account the 3-dimensional (3D) aspects of cardiac tissue, making accurate quantification difficult. We applied deep-tissue imaging to the pressure-overloaded RV to uncover the 3D properties of the microvascular network and determine whether deficient microvascular adaptation contributes to RV failure. METHODS: Heart sections measuring 250-µm-thick were obtained from mice after pulmonary artery banding (PAB) or debanding PAB surgery and properties of the RV microvascular network were assessed using 3D imaging and quantification. Human heart tissues harvested at the time of transplantation from pulmonary arterial hypertension cases were compared with tissues from control cases with normal RV function. RESULTS: Longitudinal 3D assessment of PAB mouse hearts uncovered complex microvascular remodeling characterized by tortuous, shorter, thicker, highly branched vessels, and overall preserved microvascular density. This remodeling process was reversible in debanding PAB mice in which the RV function recovers over time. The remodeled microvasculature tightly wrapped around the hypertrophied cardiomyocytes to maintain a stable contact surface to cardiomyocytes as an adaptation to RV pressure overload, even in end-stage RV failure. However, microvasculature-cardiomyocyte contact was impaired in areas with interstitial fibrosis where cardiomyocytes displayed signs of hypoxia. Similar to PAB animals, microvascular density in the RV was preserved in patients with end-stage pulmonary arterial hypertension, and microvascular architectural changes appeared to vary by etiology, with patients with pulmonary veno-occlusive disease displaying a lack of microvascular complexity with uniformly short segments. CONCLUSIONS: 3D deep tissue imaging of the failing RV in PAB mice, pulmonary hypertension rats, and patients with pulmonary arterial hypertension reveals complex microvascular changes to preserve the microvascular density and maintain a stable microvascular-cardiomyocyte contact. Our studies provide a novel framework to understand microvascular adaptation in the pressure-overloaded RV that focuses on cell-cell interaction and goes beyond the concept of capillary rarefaction.

Four decades of progress in heart-lung transplantation: Two hundred seventy-one cases at a single institution.

OBJECTIVE: The objective of this study is to evaluate survival for combined heart-lung transplant (HLTx) recipients across 4 decades at a single institution. We aim to summarize our contemporary practice based on more than 271 HLTx procedures over 40 years. METHODS: Data were collected from a departmental database and the United Network for Organ Sharing. Recipients younger than age 18 years, those undergoing redo HLTx, or triple-organ system transplantation were excluded, leaving 271 patients for analysis. The pioneering era was defined by date of transplant between 1981 and 2000 (n = 155), and the modern era between 2001 and 2022 (n = 116). Survival analysis was performed using cardinality matching of populations based on donor and recipient age, donor and recipient sex, ischemic time, and sex matching. RESULTS: Between 1981 and 2022, 271 HLTx were performed at a single institution. Recipients in the modern era were older (age 42 vs 34 y; P < .001) and had shorter waitlist times (78 vs 234 days; P < .001). Allografts from female donors were more common in the modern era (59% vs 39%; P = .002). In the matched survival analysis, 30-day survival (97% vs 84%; P = .005), 1-year survival (89% vs 77%; P = .041), and 10-year survival (53% vs 26%; P = .012) significantly improved in the modern era relative to the pioneering era, respectively. CONCLUSIONS: Long-term survival in HLTx is achievable with institutional experience and may continue to improve in the coming decades. Advances in mechanical circulatory support, improved maintenance immunosuppression, and early recognition and management of acute complications such as primary graft dysfunction and acute rejection have dramatically improved the prognosis for recipients of HLTx in our contemporary institutional experience.

Biomechanical engineering analysis of neochordae length's impact on chordal forces in mitral repair.

OBJECTIVES: Artificial neochordae implantation is commonly used for mitral valve (MV) repair. However, neochordae length estimation can be difficult to perform. The objective was to assess the impact of neochordae length changes on MV haemodynamics and neochordal forces. METHODS: Porcine MVs (n = 6) were implanted in an ex vivo left heart simulator. MV prolapse (MVP) was generated by excising at least 2 native primary chordae supporting the P2 segments from each papillary muscle. Two neochordae anchored on each papillary muscle were placed with 1 tied to the native chord length (exact length) and the other tied with variable lengths from 2× to 0.5× of the native length (variable length). Haemodynamics, neochordal forces and echocardiography data were collected. RESULTS: Neochord implantation repair successfully eliminated mitral regurgitation with repaired regurgitant fractions of approximately 4% regardless of neochord length (P < 0.01). Leaflet coaptation height also significantly improved to a minimum height of 1.3 cm compared with that of MVP (0.9 ± 0.4 cm, P < 0.05). Peak and average forces on exact length neochordae increased as variable length neochordae lengths increased. Peak and average forces on the variable length neochordae increased with shortened lengths. Overall, chordal forces appeared to vary more drastically in variable length neochordae compared with exact length neochordae. CONCLUSIONS: MV regurgitation was eliminated with neochordal repair, regardless of the neochord length. However, chordal forces varied significantly with different neochord lengths, with a preferentially greater impact on the variable length neochord. Further validation studies may be performed before translating to clinical practices.

Biomechanics and clinical outcomes of various conduit configurations in valve sparing aortic root replacement.

Background: Several conduit configurations, such as straight graft (SG), Valsalva graft (VG), anticommissural plication (ACP), and the Stanford modification (SMOD) technique, have been described for the valve-sparing aortic root replacement (VSARR) procedure. Prior ex vivo studies have evaluated the impact of conduit configurations on root biomechanics, but the mock coronary artery circuits used could not replicate the physical properties of native coronary arteries. Moreover, the individual leaflet's biomechanics, including the fluttering phenomenon, were unclear. Methods: Porcine aortic roots with coronary arteries were explanted (n=5) and underwent VSARR using SG, VG, ACP, and SMOD for evaluation in an ex vivo left heart flow loop simulator. Additionally, 762 patients who underwent VSARR from 1993 through 2022 at our center were retrospectively reviewed. Analysis of variance was performed to evaluate differences between different conduit configurations, with post hoc Tukey's correction for pairwise testing. Results: SG demonstrated lower rapid leaflet opening velocity compared with VG (P=0.001) and SMOD (P=0.045) in the left coronary cusp (LCC), lower rapid leaflet closing velocity compared with VG (P=0.04) in the right coronary cusp (RCC), and lower relative opening force compared with ACP (P=0.04) in the RCC. The flutter frequency was lower in baseline compared with VG (P=0.02) and in VG compared with ACP (P=0.03) in the LCC. Left coronary artery mean flow was higher in SG compared with SMOD (P=0.02) and ACP (P=0.05). Clinically, operations using SG compared with sinus-containing graft was associated with shorter aortic cross-clamp and cardiopulmonary bypass time (P<0.001, <0.001). Conclusions: SG demonstrated hemodynamics and biomechanics most closely recapitulating those from the native root with significantly shorter intraoperative times compared with repair using sinus-containing graft. Future in vivo validation studies as well as correlation with comprehensive, comparative clinical study outcomes may provide additional invaluable insights regarding strategies to further enhance repair durability.

Does the residual aorta dilate after replacement of the bicuspid aortic valve and ascending aorta?

Background: Although a bicuspid aortic valve (BAV) is known to be associated with progressive ascending aortic dilatation, the fate of the residual aorta after aortic valve and ascending aorta surgery is unknown. We reviewed surgical outcomes and explored serial changes in the size of the sinus of Valsalva (SOV) and distal ascending aorta (DAAo) in 89 patients with a BAV undergoing aortic valve replacement (AVR) and graft replacement (GR) of the ascending aorta. Methods: We retrospectively examined patients who underwent AVR and GR of the ascending aorta for BAV-and related disease and thoracic aortic dilatation at our institution between January 2009 and December 2018. Patients who underwent AVR alone or required intervention for the aortic root and aortic arch and patients with connective tissue diseases were excluded. Aortic diameters were examined using computed tomography (CT). Late CT more than 1 year after surgery was performed in 69 patients (78%) with a mean follow-up of 4.9±2.8 years. Results: The surgical indication for aortic valve etiology was stenosis in 61 patients (69%), regurgitation in 10 (11%), and mixed in 18 (20%). Preoperative maximum short diameters of the ascending aorta, SOV, and DAAo were 47.3±4.7, 36.0±5.2, and 37.2±3.6 mm, respectively. The diameter of the SOV increased non-significantly by 0.08±0.45 mm per year [95% confidence interval (CI): -0.12 to 0.11, P=0.150], while that of the DAAo increased significantly by 0.11±0.40 mm per year (95% CI: 0.02-0.21, P=0.005). One patient required reoperation 6 years postoperatively due to a pseudo-aneurysm at the proximal anastomotic site. No patient required reoperation due to progressive dilatation of the residual aorta. According to the Kaplan-Meier analysis, the long-term survival rates were 98.9%, 98.9%, and 92.7% at 1, 5, and 10 years postoperatively, respectively. Conclusions: Rapid dilatation of the residual aorta rarely occurred in patients with a BAV who underwent AVR and GR of the ascending aorta in the mid-term follow-up. For selected patients with a surgical indication for ascending aortic dilatation, simple AVR and GR of the ascending aorta may be sufficient surgical options.

Angiogenic stem cell delivery platform to augment post-infarction neovasculature and reverse ventricular remodeling.

Many cell-based therapies are challenged by the poor localization of introduced cells and the use of biomaterial scaffolds with questionable biocompatibility or bio-functionality. Endothelial progenitor cells (EPCs), a popular cell type used in cell-based therapies due to their robust angiogenic potential, are limited in their therapeutic capacity to develop into mature vasculature. Here, we demonstrate a joint delivery of human-derived endothelial progenitor cells (EPC) and smooth muscle cells (SMC) as a scaffold-free, bi-level cell sheet platform to improve ventricular remodeling and function in an athymic rat model of myocardial infarction. The transplanted bi-level cell sheet on the ischemic heart provides a biomimetic microenvironment and improved cell-cell communication, enhancing cell engraftment and angiogenesis, thereby improving ventricular remodeling. Notably, the increased density of vessel-like structures and upregulation of biological adhesion and vasculature developmental genes, such as Cxcl12 and Notch3, particularly in the ischemic border zone myocardium, were observed following cell sheet transplantation. We provide compelling evidence that this SMC-EPC bi-level cell sheet construct can be a promising therapy to repair ischemic cardiomyopathy.

A novel patch-sparing technique for reconstruction of the aortomitral curtain.

Our goal was to describe a novel technique for reconstructing the aortomitral curtain using autologous tissue. This technique was performed on a patient who required replacement of both the aortic and mitral valves and the aortic root due to recurrent prosthetic valve infection and aortic root abscess. The aortomitral curtain was reconstructed without using any artificial patches. Instead, surrounding autologous tissues were used, including the residual healthy left atrial and aortic basal tissues. This patch-sparing technique may occasionally be feasible to perform and may serve as a secure anchor for subsequent aortic root replacement.

Surgical Strategy for Chronic Type B Dissecting Aortic Aneurysm to Prevent Aorta-Related Events.

BACKGROUND: This study was aimed to evaluate the outcomes of performing open repair or thoracic endovascular aortic repair for chronic type B dissecting aortic aneurysm. METHODS: From July 2004 to February 2019, 52 patients underwent surgery as open repair (n = 32) or endovascular repair (n = 20) for chronic type B dissecting aortic aneurysm. Replacement of the aorta was limited to the aneurysmal portion with or without reconstructing the visceral arteries or the segmental arteries. Stent grafts were deployed in the true lumen above the celiac artery to cover the primary entry for even DeBakey IIIb dissection. RESULTS: Operative mortality and morbidity rates, including spinal cord ischemia incidence, did not differ between the groups. Operative mortality and morbidity rates, including spinal cord ischemia incidence, did not differ between the groups. In the endovascular repair group, 3 patients died due to rupture of residual false lumen in the early, and late postoperative follow-up. The 5-year rate of freedom from all-cause death, aorta-related death, and aorta-related event were 84% ± 6%, 94% ± 3% and 84% ± 6%. The endovascular repair was independently associated with all-cause death (hazard ratio [HR], 5.7; confidence interval [CI], 1.02-31.6; P = 0.04) and aorta-related event (HR, 30.9; CI 4.9-195.0; P < 0.001). In the open group, postoperative residual aortic diameter was an independent predictor of aorta-related events, and the threshold was 41 mm. CONCLUSIONS: Open repair remains a better option than simple endovascular repair alone in DeBakey IIIb dissection, but the distal un-resected aortic portion over 41 mm was associated with late aortic events.

Repair of pacemaker lead-induced right ventricular perforation via a left mini-thoracotomy.

Cardiac perforation is a rare but serious and life-threatening complication of permanent pacemaker implantation, with an incidence of 0.1-6%. Surgery is usually performed through a median sternotomy; however, sternotomy-related morbidity remains a concern. Herein, we report a case of surgical repair performed via a left mini-thoracotomy for a right ventricular perforation caused by implantation of a permanent pacemaker lead in a 56-year-old woman. Through the left fifth intercostal space, the pacemaker lead was observed to have penetrated the left ventricular myocardium, reaching the pericardium. The lead had passed through the right ventricle and the inferior ventricular septum and protruded from the left ventricular myocardium. After pacemaker lead removal, a dark blow-out type hemorrhage occurred; hence, repair was performed using a pair of pledgeted Mattress sutures. In conclusion, left mini-thoracotomy provides an adequate surgical field and has less impact on hemodynamics when operating at the cardiac apex. .

Emergency sandwich patch repair via right ventricular incision for postinfarction ventricular septal defects: a case series.

BACKGROUND: The surgical treatment for postinfarction ventricular septal defect (VSD) remains challenging, especially in emergency cases. Several authors have reported the efficacy of a sandwich patch VSD repair via a right ventricular (RV) incision. However, this procedure remains uncommon, and its efficacy is still unknown, especially when performed under an emergency. CASE SUMMARY: We were able to perform sandwich patch VSD repair via an RV incision on seven consecutive patients with VSD following an ST-segment elevation myocardial infarction (STEMI) from March 2017 to December 2019. Bovine pericardial patches were used for sandwich patches. Two patients developed inferior STEMI, and the other patients developed anterior STEMI. Six patients received intra-aortic balloon pump prior to surgery, and the other received extracorporeal membrane oxygenation with Impella. The interval between the diagnosis of VSD and surgery was within 1 day in all patients except one (5 days). All seven patients underwent VSD repair in the emergency status. Four patients underwent concomitant coronary artery bypass grafting. The hospital mortality rate was 14.3% (1/7). Early postoperative transthoracic echocardiography revealed that only one patient developed more than trace residual shunt. The postoperative right atrial pressure was not significantly elevated at ≤12 mmHg in all patients. No patient developed early postoperative prolonged low cardiac output syndrome. DISCUSSION: In patients with postinfarction VSD, a sandwich patch VSD repair via an RV incision is a promising procedure with a low incidence of residual shunt development and hospital mortality, even in emergency cases.

Reverse remodelling after aortic valve replacement for chronic aortic regurgitation.

OBJECTIVES: This study aimed to assess the long-term outcomes and investigate the factors related to left ventricular (LV) reverse remodelling after aortic valve replacement (AVR) in patients with chronic aortic regurgitation (AR). METHODS: A total of 246 patients who underwent AVR for chronic AR at our institution were included in this retrospective study. Primary end-points included all-cause mortality, cardiac mortality and major adverse cerebral and cardiovascular events. Secondary end-points included cardiac function on echocardiography 1 year after surgery. We explored the predictive factors for reverse remodelling 1 year after surgery. RESULTS: The 10-year survival rate was 86.0%, with no cardiac deaths in 93.8% and no major adverse cerebral and cardiovascular events in 79.9% of patients. Postoperative LV function and symptoms were significantly improved 1 year after surgery, but 34 patients (13.8%) did not recover normal function and structure. A significant negative correlation was found between the incidence of cardiac death and major adverse cerebral and cardiovascular events and reverse remodelling. Multivariate logistic regression identified preoperative LV ejection fraction (P = 0.001, odds ratio = 1.057) and LV end-systolic dimension index (P = 0.038, odds ratio = 0.912) as significant predictive factors of reverse remodelling 1 year after surgery. CONCLUSIONS: Preoperative LV ejection fraction and LV end-systolic dimension index were predictive factors for reverse remodelling after surgery, which was associated with late outcomes. Earlier surgery may thus help to restore normal LV function and achieve better late outcomes after AVR for AR.

Off-Pump Resection of an Epicardial Cyst by Using a Minimally Invasive Approach.

A 25-year-old man presented with palpitations and subsequently received a diagnosis of a large epicardial cyst (6.8 × 3.8 cm) originating from the left ventricle. The cyst compressed the left atrium and ventricle and led to left ventricular diastolic dysfunction. Contrast-enhanced chest computed tomography revealed that the circumflex artery passed over or through the cyst. We successfully resected the cyst without using cardiopulmonary bypass through a left mini-thoracotomy with thoracoscopic assistance. The diastolic dysfunction improved after the procedure. Most epicardial cysts may be treated in this fashion if the cyst is located in the left side of the heart.

Graft Traction Resolved Left Ventricular Outflow Tract Obstruction.

We admitted a 76-year-old woman for treatment of an ascending aortic aneurysm with left ventricular outflow tract (LVOT) obstruction and systolic anterior motion (SAM) of the mitral valve. Echocardiography showed an elevated velocity of the LVOT flow with a sigmoid septum. Mild mitral regurgitation was also detected due to SAM. We performed a graft replacement of the ascending aorta, after which the LVOT obstruction and SAM were resolved. We report a case in which the traction of a graft likely released the compression on the aortic root and ventricular septum.

Inactive large cerebral hemorrhage is not exacerbated by the adjustment of anticoagulation post open-heart surgery.

Optimal timing of open-heart surgery for the treatment of patients with cerebral hemorrhage remains controversial because systemic heparinization may lead to catastrophic bleeding. Several recent reports have shown that patients who undergo open-heart surgery .within a few weeks of cerebral hemorrhage have a much lower risk of exacerbated bleeding than previously considered. Herein, we report a case of left atrial myxoma and large hemorrhagic embolic stroke, which was successfully operated on with no exacerbation of cerebral hemorrhage. Careful assessment of time-course changes in cerebral hemorrhage by neurological imaging and adjustment of anticoagulation can help prevent the exacerbation of postoperative cerebral hemorrhage and neurological deterioration. .

Benefits of robotically-assisted surgery for complex mitral valve repair.

OBJECTIVES: To determine whether robotic mitral valve repair can be applied to more complex lesions compared with minimally invasive direct mitral valve repair through a right thoracotomy. METHODS: We enrolled 335 patients over a 9-year period; 95% of the robotic surgeries were performed after experience performing direct mitral valve repair. RESULTS: The mean age in the robotic versus thoracotomy repair groups was 61 ± 14 vs 55 ± 11 years, respectively (P < 0.001); 97% vs 100% of the patients, respectively, had degenerative aetiologies. Repair complexity was simple in 106 (63%) vs 140 (84%), complex in 34 (20%) vs 20 (12%) and most complex in 29 (17%) vs 6 (4%) patients undergoing robotic versus thoracotomy repair, respectively. The average complexity score with robotic repair was significantly higher versus thoracotomy repair (P < 0.001). The robotic group underwent more chordal replacement using polytetrafluoroethylene and less resections. All patients underwent ring annuloplasty. Cross-clamp time did not differ between the groups, and no strokes or deaths occurred. More patients undergoing robotic repair underwent concomitant procedures versus the thoracotomy group (30% vs 14%, respectively; P < 0.001). The overall repair rate was 100%, with no early mortality or strokes in either group. Postoperative mean residual mitral regurgitation was 0.3 in both groups, and the mean pressure gradient through the mitral valve was 2.4 vs 2.7 mmHg (robotic versus thoracotomy repair, respectively; P = 0.031). CONCLUSIONS: Robotic surgery can be applied to repair more complex mitral lesions, with excellent early outcomes.

Successful surgical resection and reconstruction for a huge primary cardiac lymphoma filling the right heart.

Primary cardiac lymphoma (PCL) is rare, with a frequency of 1.0%-1.6% among cardiac malignant tumors. Chemotherapy is often selected as a first-line treatment for PCL. However, when the tumor causes heart failure or life-threatening hemodynamic collapse, antecedent urgent surgery is required. We herein report a successful case of complete tumor resection and reconstruction of the right atrium and right ventricle using a bovine pericardial patch combined with tricuspid valve replacement in a patient with a huge PCL filling the right heart that manifested as tricuspid valve stenosis and subsequent heart failure.

Long-term outcomes after reoperation for mitral paravalvular leaks: a single-centre experience.

OBJECTIVES: We aimed to analyse the pathology of paravalvular leak (PVL), and determine the long-term outcomes of redo mitral valve replacement and risk factors of all-cause mortality. METHODS: Seventy-nine patients (mean age 70 ± 9 years; 54 female, 68%) who underwent redo mitral valve replacement for mitral PVL between January 2000 and May 2019 were retrospectively reviewed. Indications for PVL intervention were haemolytic anaemia (57/79, 72%), New York Heart Association class III/IV congestive heart failure (56/79, 71%) and prosthetic valve endocarditis with PVL (2/79, 3%). RESULTS: PVL most commonly occurred at lateral sectors (42/79, 55%). Early mortality occurred in 2 patients (3%) due to low cardiac output syndrome. Two patients (3%) had residual PVL at discharge. Sixteen patients (23%) developed late PVL (mean follow-up, 3.4 ± 2.9 years), among whom 11 (69%) developed PVL at same area as that preoperatively. Additionally, 9 patients (56%) developed PVL at lateral sectors in late follow-up. At 1, 5 and 10 years, the survival rate was 93%, 72% and 45%; rate of freedom from cardiac death was 96%, 92% and 78%; and rate of freedom from PVL recurrence was 94%, 82% and 54%, respectively. Chronic kidney disease was the only risk factor in the multivariate analysis for mortality [P = 0.013; hazard ratio 4.0 (1.4-11.0)]. CONCLUSIONS: Surgery for mitral PVL confers reasonable early and long-term outcomes. Greater attention to the anterolateral annulus may help prevent PVL.

Robotic mitral valve repair for rheumatic mitral stenosis and regurgitation: a case report.

BACKGROUND: Rheumatic mitral valve (MV) disease is the major cause of congestive cardiac failure in children and young adults, particularly in developing countries. Mitral valve repair with minimum prosthetic material is the gold standard treatment for this condition. However, MV repair for rheumatic MV disease is known to be technically demanding. CASE SUMMARY: A 27-year-old woman without a history of cardiac disease presented with dyspnoea on exertion. Echocardiography revealed rheumatic severe mitral stenosis and regurgitation, with thickening of the bileaflets, doming of the anterior leaflet, shortening of the posterior leaflet, fusions of the lateral and particularly the medial commissure, and enlargement of the mitral annulus. We successfully performed robot-assisted MV repair with bicommissural release, patch augmentation of the two leaflets, and implantation of an originally sized partial band. DISCUSSION: Robotic MV repair can contribute to precise valve inspection and operative procedures. This approach seems feasible for complex rheumatic MV disease particularly in young patients.

Early results of robotically assisted mitral valve repair in a single institution: report of the first 100 cases.

OBJECTIVE: Robotically assisted mitral valve repair was approved for use in Japan in April 2018. The study objective was to assess the safety and clinical outcomes of robotic mitral valve surgery in the first 100 cases performed in our center. METHODS: We reviewed the first 100 patients who underwent robotic primary mitral valve repair, including concomitant procedures, from April 2018 to August 2019. The cause of mitral valve disease was degenerative (n = 94), endocarditis (n = 2), functional (n = 2), and other (n = 2). RESULTS: There was no in-hospital or 30-day mortality. Mitral valve repair was completed in all patients. Only one patient required conversion to full sternotomy due to left ventricular apex bleeding. In echocardiography performed before hospital discharge, the mitral regurgitation was graded as none or trivial in 94 patients (94%) and mild in 4 (4%). Only two patients required surgical re-intervention due to postoperative hemolysis with moderate mitral regurgitation. For patients who underwent the mitral valve procedure alone, the median times of the total operation, cardiopulmonary bypass, aortic clamping, and console usage were 185, 112, 71, and 60 min, respectively. The learning curve showed that the operation time decreased slightly during the first ten cases and then plateaued at a mean of approximately 180 min. CONCLUSIONS: Robotically assisted mitral valve repair was feasible, safe, and therapeutically effective in the first 100 cases, with a minimal learning curve. The robotically assisted approach provides a high-quality surgical view and tremorless suture/cut handling, which will contribute to further development of minimally invasive mitral valve surgery.

Tumorigenicity assay essential for facilitating safety studies of hiPSC-derived cardiomyocytes for clinical application.

Transplantation of cardiomyocytes (CMs) derived from human induced pluripotent stem cells (hiPSC-CMs) is a promising treatment for heart failure, but residual undifferentiated hiPSCs and malignant transformed cells may lead to tumor formation. Here we describe a highly sensitive tumorigenicity assay for the detection of these cells in hiPSC-CMs. The soft agar colony formation assay and cell growth analysis were unable to detect malignantly transformed cells in hiPSC-CMs. There were no karyotypic abnormalities during hiPSCs subculture and differentiation. The hiPSC markers TRA1-60 and LIN28 showed the highest sensitivity for detecting undifferentiated hiPSCs among primary cardiomyocytes. Transplantation of hiPSC-CMs with a LIN28-positive fraction > 0.33% resulted in tumor formation in nude rats, whereas no tumors were formed when the fraction was < 0.1%. These findings suggested that combination of these in vitro and in vivo tumorigenecity assays can verify the safety of hiPSC-CMs for cell transplantation therapy.