No description available.

No description available.

No description available.

No description available.

No description available.

Implantation of engineered cardiac tissue may restore lost cardiac function to damaged myocardium. We propose that functional cardiac tissue can be fabricated using a modular, vascularized tissue engineering approach developed in our laboratory. In this study, rat aortic endothelial cells (RAEC) were coated onto sub-millimetre size modules embedded with cardiomyocyte-enriched neonatal rat heart cells (CM) and assembled into a contractile, macroporous sheet-like construct. Cell morphologies, contractility and responsiveness to electrical stimulus were examined to evaluate the function of the resulting modular construct. CM embedded modules contracted spontaneously at day 7 post-fabrication and remained viable in vitro at day 14. Modules cultured in 10% bovine serum were more contractile and responsive to external stimulus compared to 10% FBS medium cultured modules. VE-cadherin staining showed a confluent layer of RAEC on CM embedded co-culture modules at day 7. Co-culture modules were also contractilie, but when compared to CM only modules their electrical responsiveness was slightly diminished. Modules assembled into macroporous sheets retained their characteristics at day 10 post-assembly. Micrographs from histological sections revealed the existence of muscle bundles near the perimeter of modules and at inter-module junctions. The fate of modular cardiac tissues in vivo was examined using two implantation strategies based on a syngeneic animal model. Co-culture modules (CM and EC) were either injected into the peri-infarct zone of the heart, or fabricated into a patch form and implanted over a right ventricular free wall defect. In both models, donor EC were involved in the formation of blood vessels-like structures, which appeared to have connected with the host vasculature. Co-culture implants had a higher overall vessel density compared to CM-only implants, but only in the absence of MatrigelTM. Moreover, donor CM organized into striated muscle-like structures, at least when MatrigelTM was removed from the matrix. Together these results suggest that modular cardiac tissue can survive and develop into native-like structures when implanted in vivo and the potential of the modular approach as a platform for building 3-D vascularised cardiac tissue should be explored in greater depth.

Implantation of engineered cardiac tissue may restore lost cardiac function to damaged myocardium. We propose that functional cardiac tissue can be fabricated using a modular, vascularized tissue engineering approach developed in our laboratory. In this study, rat aortic endothelial cells (RAEC) were coated onto sub-millimetre size modules embedded with cardiomyocyte-enriched neonatal rat heart cells (CM) and assembled into a contractile, macroporous sheet-like construct. Cell morphologies, contractility and responsiveness to electrical stimulus were examined to evaluate the function of the resulting modular construct. CM embedded modules contracted spontaneously at day 7 post-fabrication and remained viable in vitro at day 14. Modules cultured in 10% bovine serum were more contractile and responsive to external stimulus compared to 10% FBS medium cultured modules. VE-cadherin staining showed a confluent layer of RAEC on CM embedded co-culture modules at day 7. Co-culture modules were also contractilie, but when compared to CM only modules their electrical responsiveness was slightly diminished. Modules assembled into macroporous sheets retained their characteristics at day 10 post-assembly. Micrographs from histological sections revealed the existence of muscle bundles near the perimeter of modules and at inter-module junctions. The fate of modular cardiac tissues in vivo was examined using two implantation strategies based on a syngeneic animal model. Co-culture modules (CM and EC) were either injected into the peri-infarct zone of the heart, or fabricated into a patch form and implanted over a right ventricular free wall defect. In both models, donor EC were involved in the formation of blood vessels-like structures, which appeared to have connected with the host vasculature. Co-culture implants had a higher overall vessel density compared to CM-only implants, but only in the absence of MatrigelTM. Moreover, donor CM organized into striated muscle-like structures, at least when MatrigelTM was removed from the matrix. Together these results suggest that modular cardiac tissue can survive and develop into native-like structures when implanted in vivo and the potential of the modular approach as a platform for building 3-D vascularised cardiac tissue should be explored in greater depth.

No description available.

Mitochondrial dysfunction is a common feature in a wide range of disorders and diseases from obesity, diabetes, cancer to cardiovascular diseases. The overall goal of my doctoral research has been to investigate mitochondrial metabolic dysfunction in skeletal and cardiac muscles in the context of chronic disease development. Perinatal nutrition is well known to affect risk for insulin resistance, obesity, and cardiovascular disease during adulthood. The underlying mechanisms however, are poorly understood. Previous research from our lab showed that the in utero maternal undernutrition mouse model is one in which skeletal and cardiac muscle physiology and metabolism is impaired. Here we used this model to study the impact of in utero undernutrition on offspring skeletal primary muscle cells and to determine if there is a cell autonomous phenotype. Metabolic analyses using extracellular flux technologies revealed a shift from oxidative to glycolytic metabolism in primary myotubes. Gene expression profiling identified significant changes in mRNA expression, including an upregulation of cell stress and OXPHOS genes and a downregulation of cell division genes. However, there were no changes in levels of marker proteins for mitochondrial oxidative phosphorylation (OXPHOS). Findings are consistent with the conclusion that susceptibility to metabolic disease in adulthood can be caused at least in part by muscle defects that are programmed in utero and mediated by impaired mitochondrial function. In my second project, the effects of the absence of glutaredoxin-2 (Grx2) on redox homeostasis and on mitochondrial dynamics and energetics in cardiac muscle from mice were investigated. Previous work in our lab established that Grx2-deficient mice exhibit fibrotic cardiac hypertrophy, and hypertension, and that complex I of OXPHOS is defective in isolated mitochondria. Here we studied the role of Grx2 in the control of mitochondrial structure and function in intact cells and tissue, as well as the role of GRX2 in human heart disease. We demonstrated that the absence of Grx2 impacts mitochondrial fusion, ultrastructure and energetics in mouse primary cardiomyocytes and cardiac tissue and that provision of the glutathione precursor, N-acetylcysteine (NAC) did not restore glutathione redox or prevent impairments. Furthermore we used data from the human Genotype-Tissue Expression consortium to show that low GRX2 expression is associated with increased fibrosis, hypertrophy, and infarct in the left ventricle. Altogether, our results indicate that GRX2 plays a major role in cardiac mitochondrial structure and function, and protects against left ventricle pathologies in humans. In my third project, we collaborated with cardiac surgeon, Dr. Calum Redpath, of the Ottawa Heart Institute to study atrial mitochondrial metabolism in atrial fibrillation patients with and without type 2 diabetes (T2DM). T2DM is a major risk factor for atrial fibrillation, but the causes are poorly understood. Atrial appendages from coronary artery bypass graft surgery were collected and analyzed. We showed an impaired complex I respiration in diabetic patients with atrial fibrillation compared to diabetic patients without atrial fibrillation. In addition, and for the first time in atrial fibrillation patients, mitochondrial supercomplexes were studied; results showed no differences in the assembly of the “traditional” complexes but a decrease in the formation of “high oligomeric” complexes. A strong trend for increased protein oxidation was also observed. There were no changes in markers for OXPHOS protein levels. Overall findings reveal novel aspects of mitochondrial dysfunction in atrial fibrillation and diabetes in humans. Overall, our results reveal that in utero undernutrition affects the programming of skeletal muscle primary cells, thereby increasing susceptibility to metabolic diseases. In addition, we show that GRX2 impacts cardiac mitochondrial dynamics and energetics in both mice and humans. Finally, we show impaired mitochondrial function and supercomplex assembly in humans with atrial fibrillation and T2DM. Ultimately, understanding the mechanisms causing mitochondrial dysfunction in muscle tissues during chronic disease development will increase our capacity to identify effective prevention and treatment strategies.

No description available.