Myogenic differentiation in atrium-derived adult cardiac pluripotent cells and the transcriptional regulation of GATA4 and myogenin on ANP promoter

Stem Cell Studies in Cardiovascular Biology and Medicine: A Possible Key Role of Macrophages

Simple Summary

Stem cells are used in cardiovascular biology and biomedicine and this field of research is expanding. Two types of stem cells have been used in research: induced pluripotent and somatic stem cells. Induced pluripotent stem cells (iPSCs) are similar to embryonic stem cells (ESCs) in that they can differentiate into somatic cells. Bone marrow stem/stromal cells (BMSCs), adipose-derived stem cells (ASCs), and cardiac stem cells (CSCs) are somatic stem cells that have been used for cardiac regeneration. Recent studies have indicated that exosomes and vesicles from BMSCs and ASCs can be used in regenerative medicine and diagnostics. Chemokines and exosomes can contribute to the communication between inflammatory cells and stem cells to differentiate stem cells into the cell types required for tissue regeneration or repair. In this review, we address these issues based on our research and previous publications.

Abstract

Stem cells are used in cardiovascular biology and biomedicine, and research in this field is expanding. Two types of stem cells have been used in research: induced pluripotent and somatic stem cells. Stem cell research in cardiovascular medicine has developed rapidly following the discovery of different types of stem cells. Induced pluripotent stem cells (iPSCs) possess potent differentiation ability, unlike somatic stem cells, and have been postulated for a long time. However, differentiating into adult-type mature and functional cardiac myocytes (CMs) remains difficult. Bone marrow stem/stromal cells (BMSCs), adipose-derived stem cells (ASCs), and cardiac stem cells (CSCs) are somatic stem cells used for cardiac regeneration. Among somatic stem cells, bone marrow stem/stromal cells (BMSCs) were the first to be discovered and are relatively well-characterized. BMSCs were once thought to have differentiation ability in infarcted areas of the heart, but it has been identified that paracrine cytokines and micro-RNAs derived from BMSCs contributed to that effect. Moreover, vesicles and exosomes from these cells have similar effects and are effective in cardiac repair. The molecular signature of exosomes can also be used for diagnostics because exosomes have the characteristics of their origin cells. Cardiac stem cells (CSCs) differentiate into cardiomyocytes, smooth muscle cells, and endothelial cells, and supply cardiomyocytes during myocardial infarction by differentiating into newly formed cardiomyocytes. Stem cell niches and inflammatory cells play important roles in stem cell regulation and the recovery of damaged tissues. In particular, chemokines can contribute to the communication between inflammatory cells and stem cells. In this review, we present the current status of this exciting and promising research field.

The regulation of troponins I, C and ANP by GATA4 and Nkx2-5 in heart of hibernating thirteen-lined ground squirrels, Ictidomys tridecemlineatus

Hibernation is an adaptive strategy used by various mammals to survive the winter under situations of low ambient temperatures and limited or no food availability. The heart of hibernating thirteen-lined ground squirrels (Ictidomys tridecemlineatus) has the remarkable ability to descend to low, near 0°C temperatures without falling into cardiac arrest. We hypothesized that the transcription factors GATA4 and Nkx2-5 may play a role in cardioprotection by facilitating the expression of key downstream targets such as troponin I, troponin C, and ANP (atrial natriuretic peptide). This study measured relative changes in transcript levels, protein levels, protein post-translational modifications, and transcription factor binding over six stages: euthermic control (EC), entrance into torpor (EN), early torpor (ET), late torpor (LT), early arousal (EA), and interbout arousal (IA). We found differential regulation of GATA4 whereby transcript/protein expression, post-translational modification (phosphorylation of serine 261), and DNA binding were enhanced during the transitory phases (entrance and arousal) of hibernation. Activation of GATA4 was paired with increases in cardiac troponin I, troponin C and ANP protein levels during entrance, while increases in p-GATA4 DNA binding during early arousal was paired with decreases in troponin I and no changes in troponin C and ANP protein levels. Unlike its binding partner, the relative mRNA/protein expression and DNA binding of Nkx2-5 did not change during hibernation. This suggests that either Nkx2-5 does not play a substantial role or other regulatory mechanisms not presently studied (e.g. posttranslational modifications) are important during hibernation. The data suggest a significant role for GATA4-mediated gene transcription in the differential regulation of genes which aid cardiac-specific challenges associated with torpor-arousal.

Concise review: skeletal muscle stem cells and cardiac lineage: potential for heart repair

Valuable and ample resources have been spent over the last two decades in pursuit of interventional strategies to treat the unmet demand of heart failure patients to restore myocardial structure and function. At present, it is clear that full restoration of myocardial structure and function is outside our reach from both clinical and basic research studies, but it may be achievable with a combination of ongoing research, creativity, and perseverance. Since the 1990s, skeletal myoblasts have been extensively investigated for cardiac cell therapy of congestive heart failure. Whereas the Myoblast Autologous Grafting in Ischemic Cardiomyopathy (MAGIC) trial revealed that transplanted skeletal myoblasts did not integrate into the host myocardium and also did not transdifferentiate into cardiomyocytes despite some beneficial effects on recipient myocardial function, recent studies suggest that skeletal muscle-derived stem cells have the ability to adopt a cardiomyocyte phenotype in vitro and in vivo. This brief review endeavors to summarize the importance of skeletal muscle stem cells and how they can play a key role to surpass current results in the future and enhance the efficacious implementation of regenerative cell therapy for heart failure.

Cancer research by means of tissue engineering--is there a rationale?

Tissue engineering (TE) has evoked new hopes for the cure of organ failure and tissue loss by creating functional substitutes in the laboratory. Besides various innovations in the context of Regenerative Medicine (RM), TE also provided new technology platforms to study mechanisms of angiogenesis and tumour cell growth as well as potentially tumour cell spreading in cancer research. Recent advances in stem cell technology--including embryonic and adult stem cells and induced pluripotent stem cells--clearly show the need to better understand all relevant mechanisms to control cell growth when such techniques will be administered to patients. Such TE-Cancer research models allow us to investigate the interactions that occur when replicating physiological and pathological conditions during the initial phases of replication, morphogenesis, differentiation and growth under variable given conditions. Tissue microenvironment has been extensively studied in many areas of TE and it plays a crucial role in cell signalling and regulation of normal and malignant cell functions. This article is intended to give an overview on some of the most recent developments and possible applications of TE and RM methods with regard to the improvement of cancer research with TE platforms. The synthesis of TE with innovative methods of molecular biology and stem-cell technology may help investigate and potentially modulate principal phenomena of tumour growth and spreading, as well as tumour-related angiogenesis. In the future, these models have the potential to investigate the optimal materials, culture conditions and material structure to propagate tumour growth.

3D-culture system for heart regeneration and cardiac medicine

3D cultures have gained attention in the field of regenerative medicine for their usefulness as in vitro model of solid tissues. Bottom-up technology to generate artificial tissues or organs is prospective and an attractive approach that will expand as the field of regenerative medicine becomes more translational. We have characterized c-kit positive cardiac stem cells after long-term cultures and established a 3D-nanoculture system using collagen scaffolds. By combining informatics-based studies, including proteomic analyses and microarrays, we sought to generate methods that modeled cardiac regeneration which can ultimately be used to build artificial hearts. Here, we describe the use of biodegradable beads or 3D cultures to study cardiac regeneration. We summarize recent work that demonstrates that, by using a combination of molecular analyses with 3D cultures, it is possible to evaluate concise mechanisms of solid tissue stem cell biology.

Cell shape and cardiosphere differentiation: a revelation by proteomic profiling

Stem cells (embryonic stem cells, somatic stem cells such as neural stem cells, and cardiac stem cells) and cancer cells are known to aggregate and form spheroid structures. This behavior is common in undifferentiated cells and may be necessary for adapting to certain conditions such as low-oxygen levels or to maintain undifferentiated status in microenvironments including stem cell niches. In order to decipher the meaning of this spheroid structure, we established a cardiosphere clone (CSC-21E) derived from the rat heart which can switch its morphology between spheroid and nonspheroid. Two forms, floating cardiospheres and dish-attached flat cells, could be switched reversibly by changing the cell culture condition. We performed differential proteome analysis studies and obtained protein profiles distinct between spherical forms and flat cells. From protein profiling analysis, we found upregulation of glycolytic enzymes in spheroids with some stress proteins switched in expression levels between these two forms. Evidence has been accumulating that certain chaperone/stress proteins are upregulated in concert with cellular changes including proliferation and differentiation. We would like to discuss the possible mechanism of how these aggregates affect cell differentiation and/or other cellular functions.

Cardiomyocyte regeneration

The heart was initially believed to be a terminally differentiated organ; once the cardiomyocytes died, no recovery could be made to replace the dead cells. However, around a decade ago, the concept of cardiac stem cells (CSCs) in adult hearts was proposed. CSCs differentiate into cardiomyocytes, keeping the heart functioning. Studies have proved the existence of stem cells in the heart. These somatic stem cells have been studied for use in cardiac regeneration. Moreover, recently, induced pluripotent stem cells (iPSCs) were invented, and methodologies have now been developed to induce stable cardiomyocyte differentiation and purification of mature cardiomyocytes. A reprogramming method has also been applied to direct reprogramming using cardiac fibroblasts into cardiomyocytes. Here, we address cardiomyocyte differentiation of CSCs and iPSCs. Furthermore, we describe the potential of CSCs in regenerative biology and regenerative medicine.