Regenerative Medicine Strategies for Hypoplastic Left Heart Syndrome

Hypoplastic left heart syndrome (HLHS), the most severe and common form of single ventricle congenital heart lesions, is characterized by hypoplasia of the mitral valve, left ventricle (LV), and all LV outflow structures. While advances in surgical technique and medical management have allowed survival into adulthood, HLHS patients have severe morbidities, decreased quality of life, and a shortened lifespan. The single right ventricle (RV) is especially prone to early failure because of its vulnerability to chronic pressure overload, a mode of failure distinct from ischemic cardiomyopathy encountered in acquired heart disease. As these patients enter early adulthood, an emerging epidemic of RV failure has become evident. Regenerative medicine strategies may help preserve or boost RV function in children and adults with HLHS by promoting angiogenesis and mitigating oxidative stress. Rescuing a RV in decompensated failure may also require the creation of new, functional myocardium. Although considerable hurdles remain before their clinical translation, stem cell therapy and cardiac tissue engineering possess revolutionary potential in the treatment of pediatric and adult patients with HLHS who currently have very limited long-term treatment options.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/140239/1/ten.teb.2016.0136.pd

Evaluation of Explanted CorMatrix Intracardiac Patches in Children With Congenital Heart Disease

Animal data demonstrate that intracardiac patches of decellularized porcine small intestine submucosa (CorMatrix; CorMatrix Cardiovascular, Inc, Atlanta, GA) become repopulated with native cells, suggesting the possibility of a substrate for regenerative tissue in humans. We report the only prospective series to date of explanted CorMatrix patches placed in infants with congenital heart disease

Tissue- specific angiogenic and invasive properties of human neonatal thymus and bone MSCs: Role of SLIT3- ROBO1

Although mesenchymal stem/stromal cells (MSCs) are being explored in numerous clinical trials as proangiogenic and proregenerative agents, the influence of tissue origin on the therapeutic qualities of these cells is poorly understood. Complicating the functional comparison of different types of MSCs are the confounding effects of donor age, genetic background, and health status of the donor. Leveraging a clinical setting where MSCs can be simultaneously isolated from discarded but healthy bone and thymus tissues from the same neonatal patients, thereby controlling for these confounding factors, we performed an in vitro and in vivo paired comparison of these cells. We found that both neonatal thymus (nt)MSCs and neonatal bone (nb)MSCs expressed different pericytic surface marker profiles. Further, ntMSCs were more potent in promoting angiogenesis in vitro and in vivo and they were also more motile and efficient at invading ECM in vitro. These functional differences were in part mediated by an increased ntMSC expression of SLIT3, a factor known to activate endothelial cells. Further, we discovered that SLIT3 stimulated MSC motility and fibrin gel invasion via ROBO1 in an autocrine fashion. Consistent with our findings in human MSCs, we found that SLIT3 and ROBO1 were expressed in the perivascular cells of the neonatal murine thymus gland and that global SLIT3 or ROBO1 deficiency resulted in decreased neonatal murine thymus gland vascular density. In conclusion, ntMSCs possess increased proangiogenic and invasive behaviors, which are in part mediated by the paracrine and autocrine effects of SLIT3.Comparison of mesenchymal stem/stromal cells (MSCs) from the human neonatal thymus and bone revealed that the axon guidance molecule SLIT3 is important for MSC proangiogenic effects. Not only is SLIT3 an endothelial cell stimulatory factor, but it also promotes MSC migration and invasion in an autocrine fashion via the ROBO1 receptor. Deficiency of either SLIT3 or ROBO1 can decrease the vascularization of the neonatal thymus.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/156475/2/sct312723_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/156475/1/sct312723.pd

Considerations of valvular heart disease in children with ventricular assist devices

Ventricular assist devices have become a valuable tool in the treatment of heart failure in children. The use of ventricular assist devices has decreased mortality in children with end-stage heart failure awaiting transplant. It is not uncommon for children with end-stage heart failure associated with cardiomyopathy or congenital heart disease to have significant systemic semilunar and atrioventricular valve regurgitation, which can impact the efficiency and efficacy of hemodynamic support provided by a ventricular assist device. Therefore, implanting clinicians should carefully assess for valve abnormalities that may need repair and impact device selection and cannulation strategy to effectively support this diverse population. The purpose of this review is to provide an overview of this important and relevant topic and to discuss strategies for managing these patients

Characterization and Angiogenic Potential of Human Neonatal and Infant Thymus Mesenchymal Stromal Cells

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/135262/1/sct3201544339.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/135262/2/Supplemental_Information.pd

Mesenchymal Stem/Stromal Cells from Discarded Neonatal Sternal Tissue: In Vitro Characterization and Angiogenic Properties

Autologous and nonautologous bone marrow mesenchymal stem/stromal cells (MSCs) are being evaluated as proangiogenic agents for ischemic and vascular disease in adults but not in children. A significant number of newborns and infants with critical congenital heart disease who undergo cardiac surgery already have or are at risk of developing conditions related to inadequate tissue perfusion. During neonatal cardiac surgery, a small amount of sternal tissue is usually discarded. Here we demonstrate that MSCs can be isolated from human neonatal sternal tissue using a nonenzymatic explant culture method. Neonatal sternal bone MSCs (sbMSCs) were clonogenic, had a surface marker expression profile that was characteristic of bone marrow MSCs, were multipotent, and expressed pluripotency-related genes at low levels. Neonatal sbMSCs also demonstrated in vitro proangiogenic properties. Sternal bone MSCs cooperated with human umbilical vein endothelial cells (HUVECs) to form 3D networks and tubes in vitro. Conditioned media from sbMSCs cultured in hypoxia also promoted HUVEC survival and migration. Given the neonatal source, ease of isolation, and proangiogenic properties, sbMSCs may have relevance to therapeutic applications

Human Neonatal Thymus Mesenchymal Stem Cells Promote Neovascularization and Cardiac Regeneration

Newborns with critical congenital heart disease are at significant risk of developing heart failure later in life. Because treatment options for end-stage heart disease in children are limited, regenerative therapies for these patients would be of significant benefit. During neonatal cardiac surgery, a portion of the thymus is removed and discarded. This discarded thymus tissue is a good source of MSCs that we have previously shown to be proangiogenic and to promote cardiac function in an in vitro model of heart tissue. The purpose of this study was to further evaluate the cardiac regenerative and protective properties of neonatal thymus (nt) MSCs. We found that ntMSCs expressed and secreted the proangiogenic and cardiac regenerative morphogen sonic hedgehog (Shh) in vitro more than patient-matched bone-derived MSCs. We also found that organoid culture of ntMSCs stimulated Shh expression. We then determined that ntMSCs were cytoprotective of neonatal rat cardiomyocytes exposed to H2O2. Finally, in a rat left coronary ligation model, we found that scaffoldless cell sheet made of ntMSCs applied to the LV epicardium immediately after left coronary ligation improved LV function, increased vascular density, decreased scar size, and decreased cardiomyocyte death four weeks after infarction. We conclude that ntMSCs have cardiac regenerative properties and warrant further consideration as a cell therapy for congenital heart disease patients with heart failure

Effects of Scaffold Material Used in Cardiovascular Surgery on Mesenchymal Stem Cells and Cardiac Progenitor Cells

BackgroundPolytetrafluoroethylene (PTFE) and porcine small intestinal submucosa (pSIS) are patch materials used in congenital heart surgery. Porcine SIS is an extracellular-matrix scaffold that may interact with stem or progenitor cells. To evaluate this, we determined the in vitro effects of pSIS and PTFE on human bone marrow mesenchymal stromal cells (MSCs) and cardiac progenitor cells (CPCs) in 3 areas; cell proliferation, angiogenic growth-factor production, and differentiation.MethodsHuman MSCs and CPCs were seeded onto pSIS and PTFE patches. Cell-seeded patches were cultured and then assessed for cell viability and proliferation and supernatant vascular endothelial growth factor A (VEGFA) levels. Cell proliferation was quantified by MTT assay (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide). Quantitative real-time polymerase chain reaction was performed on cell-seeded scaffolds to determine relative changes in gene expression related to angiogenesis and cardiogenesis.ResultsThe MSCs and CPCs were able to attach and proliferate on pSIS and PTFE. The proliferation rate of each cell type was similar on pSIS. Total RNA isolation was only possible from the cell-seeded pSIS patches. The MSC VEGFA production was increased by pSIS. Porcine SIS promoted an angiogenic gene profile in MSCs and an early cardiogenic profile in CPCs.ConclusionsBoth PTFE and pSIS allow for varying degrees of cell proliferation. Porcine SIS elicits different phenotypical responses in MSCs as compared with CPCs, which indicates that pSIS may be a bioactive scaffold that modulates stem cell activation and proliferation. These findings highlight the differences in scaffold material strategies and suggest potential advantages of bioactive approaches