iPSC-derived human mesenchymal stem cells improve myocardial strain of infarcted myocardium.

We investigated global and regional effects of myocardial transplantation of human induced pluripotent stem cell (iPSC)-derived mesenchymal stem cells (iMSCs) in infarcted myocardium. Acute myocardial infarction (MI) was induced by ligation of left coronary artery of severe combined immunodeficient mice before 2 × 10(5) iMSCs or cell-free saline were injected into peri-infarcted anterior free wall. Sham-operated animals received no injection. Global and regional myocardial function was assessed serially at 1-week and 8-week by segmental strain analysis by using two dimensional (2D) speckle tracking echocardiography. Early myocardial remodelling was observed at 1-week and persisted to 8-week with global contractility of ejection fraction and fractional area change in saline- (32.96 ± 14.23%; 21.50 ± 10.07%) and iMSC-injected (32.95 ± 10.31%; 21.00 ± 7.11%) groups significantly depressed as compared to sham control (51.17 ± 11.69%, P < 0.05; 34.86 ± 9.82%, P < 0.05). However, myocardial dilatation was observed in saline-injected animals (4.40 ± 0.62 mm, P < 0.05), but not iMSCs (4.29 ± 0.57 mm), when compared to sham control (3.74 ± 0.32 mm). Furthermore, strain analysis showed significant improved basal anterior wall strain (28.86 ± 8.16%, P < 0.05) in the iMSC group, but not saline-injected (15.81 ± 13.92%), when compared to sham control (22.18 ± 4.13%). This was corroborated by multi-segments deterioration of radial strain only in saline-injected (21.50 ± 5.31%, P < 0.05), but not iMSC (25.67 ± 12.53%), when compared to sham control (34.88 ± 5.77%). Improvements of the myocardial strain coincided with the presence of interconnecting telocytes in interstitial space of the infarcted anterior segment of the heart. Our results show that localized injection of iMSCs alleviates ventricular remodelling, sustains global and regional myocardial strain by paracrine-driven effect on neoangiogenesis and myocardial deformation/compliance via parenchymal and interstitial cell interactions in the infarcted myocardium.

Ontogenic development of cardiomyocytes derived from transgene-free human induced pluripotent stem cells and its homology with human heart.

AIM: Reprogramming of somatic cells utilizing viral free methods provide a remarkable method to generate human induced pluripotent stem cells (hiPSCs) for regenerative medicine. In this study, we evaluate developmental ontogeny of cardiomyocytes following induced differentiation of hiPSCs. MAIN METHODS: Fibroblasts were reprogrammed with episomal vectors to generate hiPSC and were subsequently differentiated to cardiomyocytes. Ontogenic development of cardiomyocytes was studied by real-time PCR. KEY FINDINGS: Human iPSCs derived from episomal based vectors maintain classical pluripotency markers, generate teratomas and spontaneously differentiate into three germ layers in vitro. Cardiomyogenic induction of these hiPSCs efficiently generated cardiomyocytes. Ontogenic gene expression studies demonstrated that differentiation of cardiomyocytes was initiated by increased expression of mesodermal markers, followed by early cardiac committed markers, structural and ion channel genes. Furthermore, our correlation analysis of gene expression studies with human heart demonstrated that pivotal structural genes like cardiac troponin, actinin, myosin light chain maintained a high correlation with ion channel genes indicating coordinated activation of cardiac transcriptional machinery. Finally, microelectrode recordings show that these cardiomyocytes could respond aptly to pharmacologically active drugs. Cardiomyocytes showed a chronotropic response to isoproterenol, reduced Na(+) influx with quinidine, prolongation of beating rate corrected field potential duration (cFPD) with E-4031 and reduced beating frequency and shortened cFPD with verapamil. SIGNIFICANCE: Our study shows that viral free hiPSCs efficiently differentiate into cardiomyocytes with cardiac-specific molecular, structural, and functional properties that recapitulate developmental ontogeny of cardiogenesis. These results, coupled with the potential to generate patient-specific hiPSC lines hold great promise for the development of in vitro platform for drug pharmacogenomics; disease modeling and regenerative medicine.

One-step derivation of cardiomyocytes and mesenchymal stem cells from human pluripotent stem cells.

Cardiomyocytes (CMs) and mesenchymal stem cells (MSCs) are important cell types for cardiac repair post myocardial infarction. Here we proved that both CMs and MSCs can be simultaneously generated from human induced pluripotent stem cells (hiPSCs) via a pro-mesoderm differentiation strategy. Two hiPSC lines, hiPSC (1) and hiPSC (2) were generated from human dermal fibroblasts using OCT-4, SOX-2, KLF-4, c-Myc via retroviral-based reprogramming. H9 human embryonic stem cells (hESCs) served as control. CMs and MSCs were co-generated from hiPSCs and hESCs via embryoid body-dependent cardiac differentiation protocol involving a serum-free and insulin-depleted medium containing a p38 MAPK inhibitor, SB 203580. Comparing to bone marrow and umbilical cord blood-derived MSCs, hiPSC-derived MSCs (iMSCs) expressed common MSC markers and were capable of adipogenesis, osteogenesis and chondrogenesis. Moreover, iMSCs continuously proliferated for more than 32 population doublings without cellular senescence and showed superior pro-angiogenic and wound healing properties. In summary, we generated a large number of homogenous MSCs in conjunction with CMs in a low-cost and efficient one step manner. Functionally competent CMs and MSCs co-generated from hiPSCs may be useful for autologous cardiac repair.

Cell delivery and tracking in post-myocardial infarction cardiac stem cell therapy: an introduction for clinical researchers.

Stem cell-based therapy for patients with post-infarct heart failure is a relatively new and revolutionary concept in cardiology. Despite the encouraging results from pre-clinical studies, outcomes from most clinical trials remain moderately positive while the clinical benefits are largely attributed to transplanted cell-associated paracrine effects in stimulating angiogenesis and protecting endogenous cardiomyocytes. This scenario indicates that there may be a considerably protracted iterative process of conceptual and procedural refinement before true clinical benefits can be fully materialized. At present, many pressing questions regarding cell therapy remain unanswered. In addition to the primary interest in determining the ideal type of stem cells with best cardiogenic potential in vitro and in vivo, there are growing concerns on the impact of the host cardiac milieu on the transplanted cells, including their survival, migration, engraftment, and trans-differentiation as well as contribution to left ventricular function. Effective cell delivery and tracking methods are central to the unraveling of these questions. To date, cell-delivery modalities are yet to be optimized and strategies for safe and effective assessment of cells transplanted in the recipients are to be established. In this review, we discuss cell delivery and tracking modalities that are adopted in the current pre-clinical and clinical studies. We further discussed emerging technologies that are poised to impact the success of cell therapy.