Characterisation of a Drosophila model of cardiovascular disease

Abstract

The heart, as a vital organ, must pump continuously to deliver oxygenated blood to the tissues of the body. The physical stress of pumping is supported by the extracellular matrix (ECM), a dynamic protein scaffold inside and around the heart. While a regulated ECM is required to maintain heart function, aberrant or excessive ECM remodelling, called fibrosis, is associated with disease states and is a hallmark of cardiovascular disease. One major trigger of cardiovascular disease is obesity, and fibrotic remodelling is known to occur in this context. In order to study the impact of increased body size on heart function and the molecular and biophysical characteristics of the ECM, a larval overgrowth model for obesity in the genetic model Drosophila melanogaster has been developed and characterised. This model produces giant larvae twice as heavy as their wildtype counterparts, and allows a unique opportunity to study changes in the cardiac ECM in a simple genetic model. Results demonstrate a remarkable ability of the ECM to accommodate this increase in size. The muscles of the heart are particularly robust, and there are no obvious observable defects to the matrix. Preliminary results suggest Collagen fibres are thicker and more disperse. When observing heart functionality, the cross-sectional area of the heart lumen is increased significantly in giant larvae, both at diastole and systole. However, giant larvae display defects in contraction of the heart tube, characterised by an inability to contract fully at systole. This results in a less than proportional increase in stroke volume, and an increase in heart rate. Heart function of giant larvae is clearly affected by the increase in body size. To quantify the impact to the biophysical structure of the ECM, an atomic force microscopy protocol is being developed.