Insights on the impact of mitochondrial organisation on bioenergetics in high-resolution computational models of cardiac cell architecture

• Published in: PLoS computational biology Vol. 14; no. 12; p. e1006640
• Main Authors: Ghosh, Shouryadipta, Tran, Kenneth, Delbridge, Lea M D, Hickey, Anthony J R, Hanssen, Eric, Crampin, Edmund J, Rajagopal, Vijay
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 01.12.2018; Public Library of Science (PLoS)
• Subjects: Adenosine diphosphate; Adenosine Diphosphate - metabolism; Adenosine triphosphate; Adenosine Triphosphate - metabolism; Animals; ATP; Bioenergetics; Bioengineering; Biological Transport, Active; Biology; Biology and Life Sciences; Biomedical engineering; Cardiology; Cardiomyocytes; Cell culture; Computation; Computational Biology; Computer applications; Computer Simulation; Contraction; Creatine; Creatine - metabolism; Creatine kinase; Creatine Kinase - metabolism; Cross sections; Diabetes; Diabetic Cardiomyopathies - metabolism; Diabetic Cardiomyopathies - pathology; Diffusion; Electron microscopy; Energy; Energy Metabolism; Engineering schools; Enzyme kinetics; Finite element method; Force distribution; Heart; Homogeneity; Hypoxia; Kinases; Laboratories; Male; Mathematical models; Medicine and Health Sciences; Metabolism; Microscopy, Electron, Transmission; Mitochondria; Mitochondria, Heart - metabolism; Mitochondria, Heart - ultrastructure; Models, Cardiovascular; Myocytes, Cardiac - metabolism; Myocytes, Cardiac - ultrastructure; Oxygen Consumption; Phosphates; Phosphocreatine; Phosphocreatine - metabolism; Physical Sciences; Physiology; Questions; Rats; Rats, Sprague-Dawley; Scanning electron microscopy; Software; Stress concentration; Studies; Supervision; Australia; Melbourne Victoria Australia
• ISSN: 1553-7358; 1553-734X; 1553-7358
• DOI: 10.1371/journal.pcbi.1006640

Recent electron microscopy data have revealed that cardiac mitochondria are not arranged in crystalline columns but are organised with several mitochondria aggregated into columns of varying sizes spanning the cell cross-section. This raises the question-how does the mitochondrial arrangement affect the metabolite distributions within cardiomyocytes and what is its impact on force dynamics? Here, we address this question by employing finite element modeling of cardiac bioenergetics on computational meshes derived from electron microscope images. Our results indicate that heterogeneous mitochondrial distributions can lead to significant spatial variation across the cell in concentrations of inorganic phosphate, creatine (Cr) and creatine phosphate (PCr). However, our model predicts that sufficient activity of the creatine kinase (CK) system, coupled with rapid diffusion of Cr and PCr, maintains near uniform ATP and ADP ratios across the cell cross sections. This homogenous distribution of ATP and ADP should also evenly distribute force production and twitch duration with contraction. These results suggest that the PCr shuttle and associated enzymatic reactions act to maintain uniform force dynamics in the cell despite the heterogeneous mitochondrial organization. However, our model also predicts that under hypoxia activity of mitochondrial CK enzymes and diffusion of high-energy phosphate compounds may be insufficient to sustain uniform ATP/ADP distribution and hence force generation.