Background: Neonatal mouse cardiomyocytes undergo a metabolic switch from glycolysis to oxidative phosphorylation, which results in a significant increase in reactive oxygen species (ROS) production that induces DNA damage. These cellular changes contribute to cardiomyocyte cell cycle exit and loss of the capacity for cardiac regeneration. The mechanisms that regulate this metabolic switch and the increase in ROS production have been relatively unexplored. Current evidence suggests that elevated ROS production in ischemic tissues occurs due to accumulation of the mitochondrial metabolite succinate during ischemia via succinate dehydrogenase (SDH), and this succinate is rapidly oxidized at reperfusion. Interestingly, mutations in SDH in familial cancer syndromes have been demonstrated to promote a metabolic shift into glycolytic metabolism, suggesting a potential role for SDH in regulating cellular metabolism. Whether succinate and SDH regulate cardiomyocyte cell cycle activity and the cardiac metabolic state remains unclear. Methods: Here, we investigated the role of succinate and succinate dehydrogenase (SDH) inhibition in regulation of postnatal cardiomyocyte cell cycle activity and heart regeneration. Results: Our results demonstrate that injection of succinate in neonatal mice results in inhibition of cardiomyocyte proliferation and regeneration. Our evidence also shows that inhibition of SDH by malonate treatment after birth extends the window of cardiomyocyte proliferation and regeneration in juvenile mice. Remarkably, extending malonate treatment to the adult mouse heart following myocardial infarction injury results in a robust regenerative response within 4 weeks following injury via promoting adult cardiomyocyte proliferation and revascularization. Our metabolite analysis following SDH inhibition by malonate induces dynamic changes in adult cardiac metabolism. Conclusions: Inhibition of SDH by malonate promotes adult cardiomyocyte proliferation, revascularization, and heart regeneration via metabolic reprogramming. These findings support a potentially important new therapeutic approach for human heart failure.

No abstract

Cardiac nerves regulate neonatal mouse heart regeneration and are susceptible to pathological remodeling following adult injury. Understanding cardiac nerve remodeling can lead to new strategies to promote cardiac repair. Our current understanding of cardiac nerve architecture has been limited to two-dimensional analysis. Here, we use genetic models, whole-mount imaging, and three-dimensional modeling tools to define cardiac nerve architecture and neurovascular association during development, disease, and regeneration. Our results demonstrate that cardiac nerves sequentially associate with coronary veins and arteries during development. Remarkably, our results reveal that parasympathetic nerves densely innervate the ventricles. Furthermore, parasympathetic and sympathetic nerves develop synchronously and are intertwined throughout the ventricles. Importantly, the regenerating myocardium reestablishes physiological innervation, in stark contrast to the non-regenerating heart. Mechanistically, reinnervation during regeneration is dependent on collateral artery formation. Our results reveal how defining cardiac nerve remodeling during homeostasis, disease, and regeneration can identify new therapies for cardiac disease.

Worldwide, congenital anomalies of the kidney and urinary tract (CAKUT) are the leading cause of chronic renal disease in children and play a significant causative factor in pediatric end‐stage renal disease. Current research being conducted is reliant upon animal model systems to monitor embryonic kidney development; however, a system modeling the human kidney organogenesis is a necessity in order to elucidate the intertwined genetic and molecular networks related to CAKUT pathogenesis.One known genetic correlation to CAKUT is the mutation within the gene encoding for the RET receptor tyrosine kinase, which plays a crucial role in kidney development. Mutations within the gene encoding for RET affect cellular pathways correlated to congenital anomalies such as Hirschsprung's disease and renal agenesis, which are due to the maldevelopment of neural crest cells and kidney progenitor cells, respectively. These defects indicate that RET plays a unique role in cellular mechanisms related to the kidney and ureter maturation, allowing for RET to be utilized as a renal biomarker. Monitoring RET protein expression allows for the efficiency of differentiation protocols to generate cells of kidney and neural crest lineages to be validated. Furthermore, utilizing RET as a renal biomarker could elucidate signaling molecules needed for multipotent stem cell development into a complex urinary system.There is a necessity to characterize the proficiency of protocols for Human Induced Pluripotent Stem Cells (hiPSCs) differentiation into kidney organoid and Neural Crest Stem Cells (NCSCs), in order to advance the methods for obtaining functioning kidney lineages. A novel hiPSC RET reporter cell line was created via CRISPR‐Cas9 technology to determine the efficacy of current differentiation protocols. The hiPSC RET reporter cell line was an invaluable asset to the protocol characterization process due to the role of RET in collecting duct and enteric nervous system lineages. With the ability to detect RET utilizing the fluorescent marker, as well as via immunohistochemistry, the ability to produce ureteric bud progenitor cells and NCSCs was able to be reliably verified. The RNA and protein product was analyzed via qPCR and immunofluorescence microscopy, respectively, for the presence of several renal precursor and NCSC biomarkers.Analyzation of the RNA throughout differentiation provided strong evidence for the generation of kidney progenitor cells and NCSCs. Moreover, antibody staining of the kidney organoids and neural crest cells revealed the presence of protein biomarkers produced by ureteric bud and neuronal precursor cells, respectively. Kidney organoids and neural crest cells are a promising paradigm to monitor the pathogenesis of CAKUT. Currently, a model system of the human embryonic kidney development relies on discovery of additional biomarkers in order to verify cell identity. Ultimately, the potential of having hiPSCs as a renewable resource to produce NCSCs and organoids has clinical applications in drug screening, disease modeling, and stem cell therapies – all which may lead to a novel cure for CAKUT and neurocristopathies.Support or Funding InformationAmgen Scholars Program at Washington University in St. LouisThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

No abstract