Novel regenerative therapy using cell-sheet covered with omentum flap delivers a huge number of cells in a porcine myocardial infarction model

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 α-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.

Skeletal myogenic differentiation of urine-derived stem cells and angiogenesis using microbeads loaded with growth factors

To provide site-specific delivery and targeted release of growth factors to implanted urine-derived stem cells (USCs), we prepared microbeads of alginate containing growth factors. The growth factors included VEGF, IGF-1, FGF-1, PDGF, HGF and NGF. Radiolabeled growth factors were loaded separately and used to access the in vitro release from the microbeads with a gamma counter over 4 weeks. In vitro endothelial differentiation of USCs by the released VEGF from the microbeads in a separate experiment confirmed that the released growth factors from the microbeads were bioactive. USCs and microbeads were mixed with the collagen gel type 1 (2 mg/ml) and used for in vivo studies through subcutaneous injection into nude mice. Four weeks after subcutaneous injection, we found that grafted cell survival was improved and more cells expressed myogenic and endothelial cell transcripts and markers compared to controls. More vessel formation and innervations were observed in USCs combined with six growth factors cocktail incorporated in microbeads compared to controls. In conclusion, a combination of growth factors released locally from the alginate microbeads induced USCs to differentiate into a myogenic lineage, enhanced revascularization and innervation, and stimulated resident cell growth in vivo. This approach could potentially be used for cell therapy in the treatment of stress urinary incontinence.

Myocardial cell sheet therapy and cardiac function

Heart failure (HF) is the leading cause of death in developed countries. Regenerative medicine has the potential to drastically improve treatment for advanced HF. Stem cell-based medicine has received attention as a promising candidate therapy over the past decade; however, it has not yet realized this potential in terms of reliability. The cell sheet is an innovative technology for constructing aligned graft cells, and several cell sources have been investigated for making a feasible cell sheet. The most representative thus far is skeletal myoblast, although such cells raise the issue of arrhythmogenicity. Regenerative cardiomyocytes (CMs) derived from pluripotent stem cells (PSCs), such as embryonic stem cells or induced PSCs, are the most promising, because a myocardial cell sheet (MCS) constructed with regenerative CMs can potentially enable contraction recovery and electromechanical coupling with host CMs. The functional outcomes of experimental MCS are reduction of ventricular wall stress and paracrine effects rather than contraction recovery. Several technical obstacles still hamper the clinical application of MCSs, with graft survival the most pivotal issue. Ischemia, apoptosis, inflammation, and immune response can all cause graft cell death, and a stable blood supply to the MCS is critical for successful engraftment. Ventricular tachycardia must also be considered in any myocardial cell therapy, and multiple layering of MCS (>3 layers) is necessary to reconstruct human myocardium. Innervation is also a potential issue. The future application of myocardial cell therapy with MCS for advanced HF depends on resolving these difficulties.

Cardiovascular surgery for realization of regenerative medicine

Regenerative medicine is emerging as a new approach to the treatment of severe cardiovascular diseases that are resistant to conventional therapies. Although the type of cell transplanted (e.g., pluripotent stem cells, bone marrow-derived stem cells, skeletal myoblasts, or cardiac stem cells) influences the outcome of stem cell transplantation, the method of transplantation is also important, as the efficiency of engraftment after simple needle injection is poor. Scaffold-free cell sheet transplantation technology is one of the most promising methods in this regard. Although the results of clinical trials of stem cell therapy have been marginal to date, further elucidation of the actual mechanisms of cardiac repair following cell therapy would enhance the potential for full-scale implementation of stem cell therapy. In addition to stem cell therapy, the field of cardiovascular regenerative medicine includes interspecific chimera technology, drug delivery systems using biodegradable materials, and gene therapy. Integration of these new modalities with conventional therapies will be important to realize the goal of cardiovascular regenerative medicine tailored to the condition of each individual patient. Cardiovascular surgery would be an excellent means of carrying out this strategy and could potentially resolve the health problems of the increasing number of advanced cardiovascular patients. Herein, we review the recent basic and clinical research associated with the realization of regenerative medicine in the field of cardiovascular surgery.

Myoblast sheet can prevent the impairment of cardiac diastolic function and late remodeling after left ventricular restoration in ischemic cardiomyopathy

BACKGROUND

Impairment of diastolic function and late remodeling are concerns after left ventricular restoration (LVR) for ischemic cardiomyopathy. This study aims to evaluate the effects of combined surgery of myoblast sheets (MS) implantation and LVR.

METHODS

Rat myocardial infarction model was established 2 weeks after left anterior descending artery ligation. They were divided into three groups: sham operation (n=15; group sham), LVR by plicating the infracted area (n=15; group LVR), and MS implantation with LVR (n=15; group LVR+MS).

RESULTS

Serial echocardiographic study revealed significant LV redilatation and decrease of ejection fraction 4 weeks after LVR in group LVR. MS implantation combined with LVR prevented those later deteriorations of LV function in group LVR+MS. Four weeks after the operation, a hemodynamic assessment using a pressure-volume loop showed significantly preserved diastolic function in group LVR+MS; end-diastolic pressure (LVR vs. LVR+MS: 9.0±6.6 mm Hg vs. 2.0±1.0 mm Hg, P<0.05), end-diastolic pressure-volume relationship (LVR vs. LVR+MS 42±23 vs. 13±6, P<0.05). Histological examination revealed cellular hypertrophy and LV fibrosis were significantly less and vascular density was significantly higher in group LVR+MS than in the other two groups. Reverse transcription polymerase chain reaction demonstrated significantly suppressed expression of transforming growth factor-beta, Smad2, and reversion-inducing cysteine-rich protein with Kazal motifs in group LVR+MS.

CONCLUSIONS

MS implantation decreased cardiac fibrosis by suppressing the profibrotic gene expression and attenuated the impairment of diastolic function and the late remodeling after LVR. It is suggesting that MS implantation may improve long-term outcome of LVR for ischemic heart disease.