Biology subjects

Hacker, T. A.

Publications and source records attributed to Hacker, T. A..

3 recordsLinked to original sources

bioRxiv2024

Human iPSC-derived Committed Cardiac Progenitors Generate Cardiac Tissue Grafts in a Swine Ischemic Cardiomyopathy Model without Triggering Ventricular Arrhythmias

BackgroundIntramyocardial injection of human pluripotent stem cell-derived cardiomyocytes following a myocardial infarction (MI) improves cardiac function in large animal models, but associated ventricular arrhythmias are major safety concern. We hypothesized that transendocardial injection of human induced pluripotent stem cell (hiPSC)-derived committed cardiac progenitor cells (CCPs), combined with cardiac fibroblast-derived extracellular matrix (cECM) to enhance cell retention, will generate cardiac tissue grafts improving contractility without triggering ventricular arrhythmias. MethodshiPSCs were differentiated using bioreactors and small molecules to produce committed cardiac progenitor cells (CCPs). MI was created using a coronary artery balloon occlusion and reperfusion model in Yucatan mini pigs. Four weeks later, epicardial needle injections of CCPs+cECM were performed in a small initial feasibility cohort (n=6), and then transendocardial injections of CCPs+cECM (n=14), CCPs alone (n=14), cECM alone (n=4) or vehicle control (n=13) into the peri-infarct region in a randomized cohort. Arrhythmias were evaluated using implanted event recorders. Magnetic resonance imaging (MRI) and invasive pressure-volume assessment were used to evaluate left ventricular anatomic and functional performance. Detailed histology was performed to detect and characterize human grafts. ResultsA scalable biomanufacturing protocol was developed generating CCPs which can efficiently differentiate into cardiomyocytes or endothelial cells in vitro. Intramyocardial delivery of CCPs to post-MI porcine hearts resulted in engraftment and differentiation of CCPs to form ventricular cardiomyocyte rich grafts. There was no significant difference in cardiac MRI-based measured cardiac volumes or function between control, CCP and CCP+cECM groups; however, pressure-volume analysis showed an improvement in dobutamine-stimulated functional reserve in CCP and CCP+cECM groups. Delivery of CCPs did not result in tumors or ventricular arrhythmias. ConclusionsTransendocardial delivery of CCPs with or without cECM into post-MI porcine hearts resulted in comparable human cardiomyocyte grafts which did not improve resting LV function but did improve stress-induced contractile reserve without triggering ventricular arrhythmias.

pathology↗

bioRxiv2023

Restricting dietary protein or dietary isoleucine improves metabolic health in aged mice

In defiance of the paradigm that calories from all sources are equivalent, we and others have shown that dietary protein is a dominant regulator of healthy aging. The restriction of protein or the branched-chain amino acid isoleucine promotes healthspan and extends lifespan when initiated in young or adult mice. However, many interventions are less efficacious or even deleterious when initiated in aged animals. Here, we investigate the physiological, metabolic, and molecular consequences of consuming a diet with a 67% reduction of all amino acids (Low AA), or of isoleucine alone (Low Ile), in male and female C57BL/6J.Nia mice starting at 20 months of age. We find that both diet regimens effectively reduce adiposity and improve glucose tolerance, which were benefits that were not mediated by reduced calorie intake. Both diets improve specific aspects of frailty, slow multiple molecular indicators of aging rate, and rejuvenate the aging heart and liver at the molecular level. These results demonstrate that Low AA and Low Ile diets can drive youthful physiological and molecular signatures, and support the possibility that these dietary interventions could help to promote healthy aging in older adults.

physiology↗

bioRxiv2022

Disruption of the nuclear localization signal in RBM20 is causative in dilated cardiomyopathy

Human patients carrying genetic mutations in RNA binding motif 20 (RBM20) develop a clinically aggressive dilated cardiomyopathy (DCM). RBM20 is a splicing factor with two canonical domains, an RNA recognition motif (RRM) and an arginine-serine rich (RS) domain. RRM loss-of-function disrupts the splicing of RBM20 target transcripts and leads to systolic dysfunction without overt DCM, while mutations in the RS domain precipitate DCM. We show that mice lacking the RS domain (Rbm20{Delta}RS) manifest DCM with mis-splicing of RBM20 target transcripts. We found that RBM20 is mis-localized in Rbm20{Delta}RS mice but not in mice lacking the RRM, which are also deficient in RBM20 splicing. We determine that the RS domain, not other domains including the RRM, is critical for RBM20 nuclear import and define the core nuclear localization signal (NLS) within this domain. Mutation analysis of phosphorylation sites within the RS domain indicate that phosphorylation is dispensable for RBM20 nuclear import. Collectively, our findings establish disruption of the NLS in RBM20 as a causative mechanism in DCM through nucleocytoplasmic transport.

cell biology↗