Köichi Toda

BACKGROUND: Transplantation of cardiomyocytes that are derived from human induced pluripotent stem cell-derived cardiomyocytes (hiPS-CMs) shows promise in generating new functional myocardium in situ, whereas the survival and functionality of the transplanted cells are critical in considering this therapeutic impact. Cell-sheet method has been used to transplant many functional cells; however, potential ischemia might limit cell survival. The omentum, which is known to have rich vasculature, is expected to be a source of blood supply. We hypothesized that transplantation of hiPS-CM cell sheets combined with an omentum flap may deliver a large number of functional hiPS-CMs with enhanced blood supply. METHODS AND RESULTS: Retrovirally established human iPS cells were treated with Wnt signaling molecules to induce cardiomyogenic differentiation, followed by superparamagnetic iron oxide labeling. Cell sheets were created from the magnetically labeled hiPS-CMs using temperature-responsive dishes and transplanted to porcine hearts with or without the omentum flap (n=8 each). Two months after transplantation, the survival of superparamagnetic iron oxide-labeled hiPS-CMs, assessed by MRI, was significantly greater in mini-pigs with the omentum than in those without it; histologically, vascular density in the transplanted area was significantly greater in mini-pigs with the omentum than in those without it. The transplanted tissues contained abundant cardiac troponin T-positive cells surrounded by vascular-rich structures. CONCLUSIONS: The omentum flap enhanced the survival of hiPS-CMs after transplantation via increased angiogenesis, suggesting that this strategy is useful in clinical settings. The combination of hiPS-CMs and the omentum flap may be a promising technique for the development of tissue-engineered vascular-rich new myocardium in vivo.

In this study, we proposed that the functionality or phenotype of differentiated cardiomyocytes derived from human induced pluripotent stem cells (iPSC-CMs) might be modified by co-culture with mesenchymal stem cells (MSCs), resulting in an improved therapeutic potential for failing myocardial tissues. Structural, motility, electrophysiological, and metabolic analyses revealed that iPSC-CMs co-cultured with MSCs displayed aligned myofibrils with A-, H-, and I-bands that could contract and relax quickly, indicating the promotion of differentiation and the establishment of the iPSC-CM structural framework, and showed clear gap junctions and an electric pacing of >2 Hz, indicating enhanced cell-cell interactions. In addition, soluble factors excreted by MSCs, including several cytokines and exosomes, enhanced cardiomyocyte-specific marker production, produced more energy under normal and stressed conditions, and reduced reactive oxygen species production by iPSC-CMs under stressed condition. Notably, gene ontology and pathway analysis revealed that microRNAs and proteins in the exosomes impacted the functionality and maturation of iPSC-CMs. Furthermore, cell sheets consisting of a mixture of iPSC-CMs and MSCs showed longer survival and enhanced therapeutic effects compared with those consisting of iPSC-CMs alone. This may lead to a new type of iPSC-based cardiomyogenesis therapy for patients with heart failure.

Background When transplanted into failing heart, autologous somatic tissue–derived cells yield functional recovery via paracrine effects that enhance native regeneration. However, the therapeutic effects are modest. We developed a method in which scaffold‐free cell sheets are attached to the epicardial surface to maximize paracrine effects. This Phase I clinical trial tested whether transplanting autologous cell–sheets derived from skeletal muscle is feasible, safe, and effective for treating severe congestive heart failure. Methods and Results Fifteen ischemic cardiomyopathy patients and 12 patients with dilated cardiomyopathy, who were in New York Heart Association functional class II or III and had been treated with the maximum medical and/or interventional therapies available, were enrolled. Scaffold‐free cell sheets of 3 to 9×10 8 cells derived from autologous muscle were transplanted over the LV free wall via left thoracotomy, without additional interventional treatments. There were no procedure‐related major complications during follow‐up. The majority of the ischemic cardiomyopathy patients showed marked symptomatic improvement in New York Heart Association classification (pre: 2.9±0.5 versus 6 months: 2.1±0.4, P <0.01; 1 year: 1.9±0.3, P <0.01) and the Six‐Minute Walk Test with significant reduction of serum brain natriuretic peptide level (pre: 308±72 pg/mL versus 6 months: 191±56 versus 1 year: 182±46, P <0.05), pulmonary artery pressure, pulmonary capillary wedge pressure, pulmonary vein resistance, and left ventricular wall stress after transplantation instead of limited efficacy in dilated cardiomyopathy patients. Conclusions Cell‐sheet transplantation as a sole therapy was feasible for treating cardiomyopathy. Promising results in the safety and functional recovery warrant further clinical follow‐up and larger studies to confirm this treatment's efficacy for severe congestive heart failure. Clinical Trial Registration URL : http://www.umin.ac.jp/english/ . Unique identifier: UMIN 000003273.