'Shovel-Ready' applications of stem cell advances for pediatric heart disease

Recent advances and challenges on application of tissue engineering for treatment of congenital heart disease

Congenital heart disease (CHD) affects a considerable number of children and adults worldwide. This implicates not only developmental disorders, high mortality, and reduced quality of life but also, high costs for the healthcare systems. CHD refers to a variety of heart and vascular malformations which could be very challenging to reconstruct the malformed region surgically, especially when the patient is an infant or a child. Advanced technology and research have offered a better mechanistic insight on the impact of CHD in the heart and vascular system of infants, children, and adults and identified potential therapeutic solutions. Many artificial materials and devices have been used for cardiovascular surgery. Surgeons and the medical industry created and evolved the ball valves to the carbon-based leaflet valves and introduced bioprosthesis as an alternative. However, with research further progressing, contracting tissue has been developed in laboratories and tissue engineering (TE) could represent a revolutionary answer for CHD surgery. Development of engineered tissue for cardiac and aortic reconstruction for developing bodies of infants and children can be very challenging. Nevertheless, using acellular scaffolds, allograft, xenografts, and autografts is already very common. Seeding of cells on surface and within scaffold is a key challenging factor for use of the above. The use of different types of stem cells has been investigated and proven to be suitable for tissue engineering. They are the most promising source of cells for heart reconstruction in a developing body, even for adults. Some stem cell types are more effective than others, with some disadvantages which may be eliminated in the future.

Regulation of Osteogenic Differentiation of Placental-Derived Mesenchymal Stem Cells by Insulin-Like Growth Factors and Low Oxygen Tension

Placental mesenchymal stem cells (PMSCs) are multipotent cells that can differentiate in vitro to multiple lineages, including bone. Insulin-like growth factors (IGFs, IGF-1 and IGF-2) participate in maintaining growth, survival, and differentiation of many stem cells, including osteoprogenitors. Low oxygen tension (PO₂) can maintain stem cell multipotency and impede osteogenic differentiation. In this study, we investigated whether PMSC osteogenic differentiation is influenced by low PO₂ and by IGFs. Our results indicated that low PO₂ decreased osteogenic markers RUNX2 and OPN; however, re-exposure to higher oxygen tension (room air) restored differentiation. IGFs, especially IGF-1, triggered an earlier expression of RUNX2 and enhanced OPN and mineralization. RUNX2 was phosphorylated in room air and augmented by IGFs. IGF-1 receptor (IGF-1R) was increased in low PO₂ and reduced by IGFs, while insulin receptor (IR) was increased in differentiating PMSCs and enhanced by IGF-1. Low PO₂ and IGFs maintained higher IR-A which was switched to IR-B in room air. PI3K/AKT was required for osteogenic differentiation, while MEK/ERK was required to repress an RUNX2 and OPN increase in low PO₂. Therefore, IGFs, specifically IGF-1, trigger the earlier onset of osteogenic differentiation in room air, whereas, reversibly, low PO₂ impedes complete differentiation by maintaining higher multipotency and lower differentiation markers.

Management of children with congenital heart defect: state of the art and future prospects

The treatment of children with congenital heart defects has evolved in the last 60 years from conservative care to a highly specialized management where advances in imaging, surgical, interventional and support techniques meet together to ensure satisfactory development and good quality of life to the child and to the upcoming grown up. Management of congenital heart defects best begins before birth with the aim, whenever possible, to maintain or establish biventricular physiology or, if this is excluded, to optimize the conditions for univentricular physiology. Current research in the field of genetics, device bioengineering and miniaturization, stem cell therapy, and fusion imaging technology is expected to help to improve further patient outcome. In this review, current management strategies and future prospects are discussed.

Human Cardiomyocytes Prior to Birth by Integration-Free Reprogramming of Amniotic Fluid Cells

: The establishment of an abundant source of autologous cardiac progenitor cells would represent a major advance toward eventual clinical translation of regenerative medicine strategies in children with prenatally diagnosed congenital heart disease. In support of this concept, we sought to examine whether functional, transgene-free human cardiomyocytes (CMs) with potential for patient-specific and autologous applications could be reliably generated following routine amniocentesis. Under institutional review board approval, amniotic fluid specimens (8-10 ml) at 20 weeks gestation were expanded and reprogrammed toward pluripotency using nonintegrating Sendai virus (SeV) expressing OCT4, SOX2, cMYC, and KLF4. Following exposure of these induced pluripotent stem cells to cardiogenic differentiation conditions, spontaneously beating amniotic fluid-derived cardiomyocytes (AF-CMs) were successfully generated with high efficiency. After 6 weeks, quantitative gene expression revealed a mixed population of differentiated atrial, ventricular, and nodal AF-CMs, as demonstrated by upregulation of multiple cardiac markers, including MYH6, MYL7, TNNT2, TTN, and HCN4, which were comparable to levels expressed by neonatal dermal fibroblast-derived CM controls. AF-CMs had a normal karyotype and demonstrated loss of NANOG, OCT4, and the SeV transgene. Functional characterization of SIRPA⁺ AF-CMs showed a higher spontaneous beat frequency in comparison with dermal fibroblast controls but revealed normal calcium transients and appropriate chronotropic responses after β-adrenergic agonist stimulation. Taken together, these data suggest that somatic cells present within human amniotic fluid can be used to generate a highly scalable source of functional, transgene-free, autologous CMs before a child is born. This approach may be ideally suited for patients with prenatally diagnosed cardiac anomalies.

SIGNIFICANCE

This study presents transgene-free human amniotic fluid-derived cardiomyocytes (AF-CMs) for potential therapy in tissue engineering and regenerative medicine applications. Using 8-10 ml of amniotic fluid harvested at 20 weeks gestation from normal pregnancies, a mixed population of atrial, ventricular, and nodal AF-CMs were reliably generated after Sendai virus reprogramming toward pluripotency. Functional characterization of purified populations of beating AF-CMs revealed normal calcium transients and appropriate chronotropic responses after β-adrenergic agonist stimulation in comparison with dermal fibroblast controls. Because AF-CMs can be generated in fewer than 16 weeks, this approach may be ideally suited for eventual clinical translation at birth in children with prenatally diagnosed cardiac anomalies.

Cellular and molecular characterization of human cardiac stem cells reveals key features essential for their function and safety

Cell therapy of heart diseases is emerging as one of the most promising known treatments in recent years. Transplantation of cardiac stem cells (CSCs) may be one of the best strategies to cure adult or pediatric heart diseases. As these patient-derived stem cells need to be isolated from small heart biopsies, it is important to select the best isolation method and CSC subpopulation with the best cardiogenic functionality. We employed three different protocols including c-KIT(+) cell sorting, clonogenic expansion, and explants culture to isolate c-KIT(+) cells, clonogenic expansion-derived cells (CEDCs), and cardiosphere-derived cells (CDCs), respectively. Evaluation of isolated CSC characteristics in vitro and after rat myocardial infarction (MI) model transplantation revealed that although c-KIT(+) and CDCs had higher MI regenerative potential, CEDCs had more commitment into cardiomyocytes and needed lower passages that were essential to reach a definite cell count. Furthermore, genome-wide expression analysis showed that subsequent passages caused changes in characteristics of cells, downregulation of cell cycle-related genes, and upregulation of differentiation and carcinogenic genes, which might lead to senescence, commitment, and possible tumorigenicity of the cells. Because of different properties of CSC subpopulations, we suggest that appropriate CSCs subpopulation should be chosen based on their experimental or clinical use.

Right ventricular failure and pathobiology in patients with congenital heart disease - implications for long-term follow-up

Right ventricular dysfunction represents a common problem in patients with congenital heart defects, such as Tetralogy of Fallot or pulmonary arterial hypertension. Patients with congenital heart defects may present with a pressure or volume overloaded right ventricle (RV) in a bi-ventricular heart or in a single ventricular circulation in which the RV serves as systemic ventricle. Both subsets of patients are at risk of developing right ventricular failure. Obtaining functional and morphological imaging data of the right heart is technically more difficult than imaging of the left ventricle. In contrast to findings on mechanisms of left ventricular dysfunction, very little is known about the pathophysiologic alterations of the right heart. The two main causes of right ventricular dysfunction are pressure and/or volume overload of the RV. Until now, there are no appropriate models available analyzing the effects of pressure and/or volume overload on the RV. This review intends to summarize clinical aspects mainly focusing on the current research in this field. In future, there will be increasing attention to individual care of patients with right heart diseases. Hence, further investigations are essential for understanding the right ventricular pathobiology.