Improvement of mouse cardiac function by hESC-derived cardiomyocytes correlates with vascularity but not graft size.
ABSTRACT Transplantation of human embryonic stem cell-derived cardiomyocytes (hESC-CM) has been shown to improve the function of the rodent heart 1 month after myocardial infarction (MI). However, the mechanistic basis and optimal delivery strategies are unclear. We investigated the influence of the number of injected cells, resulting graft size, and possible paracrine mechanisms in this process. MI was induced in NOD-SCID mice (n=84) followed by injection of enriched hESC-CM at different dosages, hESC-non-CM derivatives, culture medium, or no injection. Cardiac function was monitored for 12 weeks with 9.4 T MRI (n=70). Grafts were identified by epifluorescence of a transgenic GFP marker and characterized by immunofluorescence. Vascularity and paracrine effects were investigated immunohistochemically. Transplantation of differentiated hESCs improved short, mid-, and long-term cardiac performance and survival, although only cardiomyocytes formed grafts. A mid-term (4 weeks) cardiomyocyte-specific enhancement was associated with elevated vascular density around the graft and attenuated compensatory remodeling. However, increasing the number of hESC-CM for injection did not enhance heart function further. Moreover, we observed that small graft size was associated with a better functional outcome. HESC-CM increased myocardial vascularization and enhanced heart function in mice after MI, but larger graft size was associated with reduced functional improvement. Future studies should focus on advanced delivery strategies and mechanisms of action rather than increasing graft size.
Stem Cell Research & Therapy 11/2011; 2(6):44. · 3.21 Impact Factor
Article: Efficient differentiation of human induced pluripotent stem cells generates cardiac cells that provide protection following myocardial infarction in the rat.[show abstract] [hide abstract]
ABSTRACT: Induced pluripotent stem (iPS) cells are being used increasingly to complement their embryonic counterparts to understand and develop the therapeutic potential of pluripotent cells. Our objectives were to identify an efficient cardiac differentiation protocol for human iPS cells as monolayers, and demonstrate that the resulting cardiac progenitors could provide a therapeutic benefit in a rodent model of myocardial infarction. Herein, we describe a 14-day protocol for efficient cardiac differentiation of human iPS cells as a monolayer, which routinely yielded a mixed population in which over 50% were cardiomyocytes, endothelium, or smooth muscle cells. When differentiating, cardiac progenitors from day 6 of this protocol were injected into the peri-infarct region of the rat heart; after coronary artery ligation and reperfusion, we were able to show that human iPS cell-derived cardiac progenitor cells engrafted, differentiated into cardiomyocytes and smooth muscle, and persisted for at least 10 weeks postinfarct. Hearts injected with iPS-derived cells showed a nonsignificant trend toward protection from decline in function after myocardial infarction, as assessed by magnetic resonance imaging at 10 weeks, such that the ejection fraction at 10 weeks in iPS treated hearts was 62%±4%, compared to that of control infarcted hearts at 45%±9% (P<0.2). In conclusion, we demonstrated efficient cardiac differentiation of human iPS cells that gave rise to progenitors that were retained within the infarcted rat heart, and reduced remodeling of the heart after ischemic damage.Stem cells and development 12/2011; 21(6):977-86. · 4.15 Impact Factor
Article: Murine and human pluripotent stem cell-derived cardiac bodies form contractile myocardial tissue in vitro.[show abstract] [hide abstract]
ABSTRACT: AimsWe explored the use of highly purified murine and human pluripotent stem cell (PSC)-derived cardiomyocytes (CMs) to generate functional bioartificial cardiac tissue (BCT) and investigated the role of fibroblasts, ascorbic acid (AA), and mechanical stimuli on tissue formation, maturation, and functionality.Methods and resultsMurine and human embryonic/induced PSC-derived CMs were genetically enriched to generate three-dimensional CM aggregates, termed cardiac bodies (CBs). Addressing the critical limitation of major CM loss after single-cell dissociation, non-dissociated CBs were used for BCT generation, which resulted in a structurally and functionally homogenous syncytium. Continuous in situ characterization of BCTs, for 21 days, revealed that three critical factors cooperatively improve BCT formation and function: both (i) addition of fibroblasts and (ii) ascorbic acid supplementation support extracellular matrix remodelling and CB fusion, and (iii) increasing static stretch supports sarcomere alignment and CM coupling. All factors together considerably enhanced the contractility of murine and human BCTs, leading to a so far unparalleled active tension of 4.4 mN/mm(2) in human BCTs using optimized conditions. Finally, advanced protocols were implemented for the generation of human PSC-derived cardiac tissue using a defined animal-free matrix composition.ConclusionBCT with contractile forces comparable with native myocardium can be generated from enriched, PSC-derived CMs, based on a novel concept of tissue formation from non-dissociated cardiac cell aggregates. In combination with the successful generation of tissue using a defined animal-free matrix, this represents a major step towards clinical applicability of stem cell-based heart tissue for myocardial repair.European Heart Journal 10/2012; · 10.48 Impact Factor