Abstract
Congenital heart disease is rarely cured by surgery and can lead to life-threatening, intractable right ventricular heart failure (HF). In particular, children with hypoplastic left heart syndrome have a 10 year transplant-free survival rate of 50-75% despite palliative surgical repair. Currently, no effective stem-cell based treatments are available for pediatric HF. Recent stem-cell based clinical trials have been limited by poor differentiation rates and low cell retention. Additionally, we have shown that human cardiac progenitor cells (hCPCs) have reduced regenerative potential as they age, starting as early as 1 year old. We propose the aggregation of CPCs into scaffold-free spheres to improve the differentiation of child CPCs into mature cardiac phenotypes by enhancing intercellular Notch signaling. Notch signaling activity has been implicated in the regulation of CPC fate decisions and prior research in our lab has shown that intramyocardial delivery of Notch-ligand containing hydrogels improves cardiac function. Child CPC spheres were produced at a size of 1500 cells per sphere using a microwell array and cultured in suspension. Using immunohistochemistry, we showed that aggregation of CPCs increased Notch1 expression compared to parallel monolayer cultures. This effect is not limited to CPCs and was recapitulated in spheres of Chinese hamster ovarian cells transfected with Notch1-YFP. Additionally, Notch signaling pathway gene array data showed increased expression of the Notch-cleaving metalloprotease ADAM10 (3.6-fold) and Notch ligand DLL1 (25.0-fold) in CPC spheres by 3 days in culture compared to monolayer cultures. By 14 days in culture, we showed that aggregation of CPCs robustly increases the expression of the GATA4, a cardiac transcription factor associated with angiogenesis, and VEGFR1, an early marker of endothelial lineage commitment. Based on our results, we hypothesize that aggregation of CPCs into spheroids increases endothelial differentiation via a Notch-dependent mechanism. Transplantation of CPC spheres may improve cardiac function in vivo compared to transplantation of single CPCs. The results from our project will facilitate the development of autologous stem-cell based therapies for pediatric HF.
Published Version
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