Generation of induced pluripotent stem cell line (VRISGi004-A) from a healthy female donor by reprogramming erythroid progenitor cells

We generated a human induced pluripotent stem cell (hiPSC) line from erythroid progenitor cells (EPCs) of a 20-year-old female healthy donor using Sendai virus vector encoding Yamanaka factors OCT3/4, SOX2, c-MYC, and KLF4. The established hiPSCs showed a standard morphology and expression of typical undifferentiated stem cell markers, a normal karyotype (46, XX), and demonstrated potential for differentiation in vitro. Furthermore, they were successfully differentiated into cardiomyocytes that expressed cardiomyocyte-specific markers. The iPSC line and iPSC-derived cardiomyocytes will provide new avenues for future drug testing/development and personalized cell therapy for cardiovascular diseases (CVDs).

Hutchinson-Gilford progeria patient-derived cardiomyocyte model of carrying LMNA gene variant c.1824 C > T

Cardiovascular diseases, atherosclerosis, and strokes are the most common causes of death in patients with Hutchinson-Gilford progeria syndrome (HGPS). The LMNA variant c.1824C > T accounts for ~ 90% of HGPS cases. The detailed molecular mechanisms of Lamin A in the heart remain elusive due to the lack of appropriate in vitro models. We hypothesize that HGPS patient's induced pluripotent stem cell (iPSC)-derived cardiomyocytes (iCMCs) will provide a model platform to study the cardio-pathologic mechanisms associated with HGPS. To elucidate the effects of progerin in cardiomyocytes, we first obtained skin fibroblasts (SFs) from a de-identified HGPS patient (hPGP1, proband) and both parents from the Progeria Research Foundation. Through Sanger sequencing and restriction fragment length polymorphism, with the enzyme EciI, targeting Lamin A, we characterized hPGP1-SFs as heterozygous mutants for the LMNA variant c.1824 C > T. Additionally, we performed LMNA exon 11 bisulfite sequencing to analyze the methylation status of the progeria cells. Furthermore, we reprogrammed the three SFs into iPSCs and differentiated them into iCMCs, which gained a beating on day 7. Through particle image velocimetry analysis, we found that hPGP1-iCMCs had an irregular contractile function and decreased cardiac-specific gene and protein expressions by qRT-PCR and Western blot. Our progeria-patient-derived iCMCs were found to be functionally and structurally defective when compared to normal iCMCs. This in vitro model will help in elucidating the role of Lamin A in cardiac diseases and the cardio-pathologic mechanisms associated with progeria. It provides a new platform for researchers to study novel treatment approaches for progeria-associated cardiac diseases.

Direct Reprogramming of Adult Human Cardiac Fibroblasts into Induced Cardiomyocytes Using miRcombo

Direct reprogramming of fibroblasts into induced cardiomyocytes (iCMs) through microRNAs (miRNAs) is a new emerging strategy for myocardial regeneration after ischemic heart disease. Previous studies have reported that murine fibroblasts can be directly reprogrammed into iCMs by transient transfection with four miRNAs (miRs-1, 133, 208 and 499 - termed "miRcombo"). While advancement in the knowledge of direct cell reprogramming molecular mechanism is in progress, it is important to investigate if this strategy may be translated to humans. Recently, we demonstrated that miRcombo transfection is able to induce direct reprogramming of adult human cardiac fibroblasts (AHCFs) into iCMs. Although additional studies are needed to achieve iCM maturation, our early findings pave the way toward new therapeutic strategies for cardiac regeneration in humans. This chapter describes methods for inducing direct reprogramming of AHCFs into iCMs through miRcombo transient transfection, showing experiments to perform for assessing iCM generation.

Noonan syndrome patient-specific induced cardiomyocyte model carrying SOS1 gene variant c.1654A>G

Noonan syndrome (NS) is a dominant autosomal genetic disorder, associated with mutations in several genes that exhibit multisystem abnormal development including cardiac defects. NS associated with the Son of Sevenless homolog 1 (SOS1) gene mutation attributes to the development of cardiomyopathy and congenital heart defects. Since the treatment option for NS is very limited, an in vitro disease model with SOS1 gene mutation would be beneficial for exploring therapeutic possibilities for NS. We reprogrammed cardiac fibroblasts obtained from a NS patient and normal control skin fibroblasts (C-SF) into induced pluripotent stem cells (iPSCs). We identified NS-iPSCs carry a heterozygous single nucleotide variation in the SOS1 gene at the c.1654A > G. Furthermore, the control and NS-iPSCs were differentiated into induced cardiomyocytes (iCMCs), and the electron microscopic analysis showed that the sarcomeres of the NS-iCMCs were highly disorganized. FACS analysis showed that 47.5% of the NS-iCMCs co-expressed GATA4 and cardiac troponin T proteins, and the mRNA expression levels of many cardiac related genes, studied by qRT-PCR array, were significantly reduced when compared to the control C-iCMCs. We report for the first time that NS-iPSCs carry a single nucleotide variation in the SOS1 gene at the c.1654A>G were showing significantly reduced cardiac genes and proteins expression as well as structurally and functionally compromised when compared to C-iCMCs. These iPSCs and iCMCs can be used as a modeling platform to unravel the pathologic mechanisms and also the development of novel drug for the cardiomyopathy in patients with NS.

Boosters and barriers for direct cardiac reprogramming

Heart disease is currently the most significant cause of morbidity and mortality worldwide, which accounts for approximately 33% of all deaths. Recently, a promising and alchemy-like strategy has been developed called direct cardiac reprogramming, which directly converts somatic cells such as fibroblasts to cardiac lineage cells such as cardiomyocytes (CMs), termed induced CMs or iCMs. The first in vitro cardiac reprogramming study, mediated by cardiac transcription factors (TFs)-Gata4, Tbx5 and Mef2C-, was not enough efficient to produce an adequate number of fully reprogrammed, functional iCMs. As a result, numerous combinations of cardiac TFs exist for direct cardiac reprogramming of mouse and human fibroblasts. However, the efficiency of direct cardiac reprogramming remains low. Recently, a number of cellular and molecular mechanisms have been identified to increase the efficiency of direct cardiac reprogramming and the quality of iCMs. For example, microgrooved substrate, cardiogenic growth factors [VEGF, FGF, BMP4 and Activin A], and an appropriate stoichiometry of TFs boost the direct cardiac reprogramming. On the other hand, serum, TGFβ signaling, activators of epithelial to mesenchymal transition, and some epigenetic factors (Bmi1 and Ezh2) are barriers for direct cardiac reprogramming. Manipulating these mechanisms by the application of boosters and removing barriers can increase the efficiency of direct cardiac reprogramming and possibly make iCMs reliable for cell-based therapy or other potential applications. In this review, we summarize the latest trends in cardiac TF- or miRNA-based direct cardiac reprogramming and comprehensively discuses all molecular and cellular boosters and barriers affecting direct cardiac reprogramming.

Heart regeneration for clinical application update 2016: from induced pluripotent stem cells to direct cardiac reprogramming

Cardiovascular disease remains a major cause of death for which current therapeutic regimens are limited. Following myocardial injury, endogenous cardiac fibroblasts, which account for more than half of the cells in the heart, proliferate and synthesize extracellular matrix, leading to fibrosis and heart failure. As terminally differentiated cardiomyocytes have little regenerative capacity following injury, the development of cardiac regenerative therapy is highly desired. Embryonic stem and induced pluripotent stem (iPS) cells are promising tools for regenerative medicine. However, these stem cells demonstrate variable cardiac differentiation efficiency and tumorigenicity, which must be resolved prior to clinical regenerative applications. Until the last decade, an established theory was that cardiomyocytes could only be produced from fibroblasts through iPS cell generation. In 2010, we first reported cardiac differentiation from fibroblasts by direct reprogramming, and we demonstrated that various cardiac reprogramming pathways exist.

This review summarizes the latest trends in stem cell and regenerative research regarding iPS cells, a partial reprogramming strategy, and direct cardiac reprogramming. We also examine the many recent advances in direct cardiac reprogramming and explore the suitable utilization of these methods for regenerative medicine in the cardiovascular field.