UC San Diego

Congenital heart defects are the leading cause of right ventricular heart failure (RVHF) in pediatric patients. In particular, hypoplastic left heart syndrome is a condition in which infants are born with an underdeveloped left side of the heart and must undergo three corrective open-heart surgeries to make their right ventricle their main systemic pump. Due to the increased afterload on the RV due to systemic circulation, the RV undergoes a cascade of negative remodeling characterized myocardial apoptosis, maladaptive hypertrophy, vessel rarefaction, metabolic shifts from lipid oxidation to glucose metabolism, inflammation, fibrosis, ischemia from mismatched oxygen supply/demand, and oxidative stress that cannot be corrected by standard treatments that only alleviate the underlying symptoms. Regenerative therapies such as c-kit cardiac progenitor cells (CPCs) and decellularized myocardial matrix (MM) hydrogels are promising therapeutics that mitigate negative remodeling in the RV and promote repair and improve overall cardiac function. CPCs, however, are limited due to their low survival and engraftment rates while MM hydrogels have yet to be investigated in models of RVHF. Furthermore, MM hydrogels that have been investigated are derived from the porcine left ventricle (LV) and have only been investigated in models of left ventricular heart failure, neglecting the fact that the LV and RV are two distinct tissues that arise separately during cardiac development. Thus, leading to a need to evaluate RV derived MM hydrogels to treat RVHF. Here we fabricate and characterize a new RV MM hydrogel and compare it to its predecessor, evaluate the effect of both MM on CPC behavior in vitro, compare CPC alone therapy with MM and CPC combined therapy in vivo, and investigate the mechanisms action of LV MM and RV MM and their effects on negative RV remodeling and function in a small animal model of RVHF. We have developed a new RV MM hydrogel, that while it is physically and mechanically similar to LV MM, it is distinctly different based on proteomic makeup. We further showed that both MM enhance the survival of CPCs against common implant hazards such as needle forces and reactive oxygen species as well as enhance their angiogenic paracrine signaling in vitro. Qualitative assessment showed the benefit of delivering CPCs with either MM to improve CPC retention in vivo while echocardiography demonstrated improvements to cardiac function only when comparing the combinatorial therapies to themselves at the baseline indicating a limited repair timeframe. CPCs alone however showed no functional improvement in echo or MRI when compared to the other treatment groups. CPCs also demonstrated detrimental differentially expressed genes when compared to saline and the MM group suggesting the adult cells hold no therapeutic benefit. Finally, we show proof-of-concept of intramyocardial injections of MM in a rat pulmonary artery banded model of RVHF. Animals injected with either LV MM or RV MM demonstrated significant improvements in tricuspid annular plane systolic excursion, RV end-diastolic volume, RV end-systolic volume, and RV free wall thickness. Both MM also affected pathways related to neovascularization, cardiac contractility, and cardiac development at 1 week post injection. RV MM, however, induced overexpression of pro-inflammatory and pro-fibrotic gene expression, suggesting it may induce a prolonged inflammatory response. Despite this, both MM didn’t affect macrophage, capillary, or myofibroblast density at the 1-week timepoint but did induce significant arteriole growth when compared to saline. Both MM further mitigated negative remodeling pathways by reducing hypertrophy, fibrosis and myofibroblast density and by increasing arteriole density when compared to saline. This study shows proof-of-concept of MM hydrogel therapies, tissue specific or otherwise, to not only mitigate pediatric RVHF with implications of being translated into other cases of RVHF.