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Role of cardiac troponin T on heart function using an ex vivo isolated rat model

A 2018/2019 Summer Studentship research project

This study will provide the first evidence of the bioactivity of rat cardiac troponin T.

Student: Cassian Duthie
Supervisors: Dr Sarah Appleby, Associate Professor Chris Pemberton
Sponsor: TBC

Project brief

Introduction

The troponins are a family of regulatory proteins found in skeletal and heart muscle fibers, and are involved in muscular contraction. Furthermore, troponin (TnI and TnT) is the gold standard biomarker for diagnosis of acute myocardial infarction (MI). The historical basis for the diagnostic use of troponin is that it only appears in measurable amounts in blood in the event of myocardial cell death, i.e. heart attack. However, it has been known for some time that cardiac troponin T exists in cytosolic pools in cardiomyocytes and that this can be possibly released into the circulation under non-heart attack related conditions. Further, with the advent of new, highly sensitive cardiac troponin T assays, it has become clear that 40–60% of the healthy, well population carries measurable amounts of troponin T in their blood. Thus, a fundamental question that has not been addressed is: does circulating cardiac troponin T have biological actions upon the heart? However, as yet, there have been no studies that have administered rat cardiac troponin T directly into an ex vivo heart and measured changes in heart function. Thus, this project will investigate the effect of rat cardiac troponin T on heart function in both normal and damaged hearts using an ex vivo rat heart attack model; measuring changes in several parameters of cardiac function.

Aim

To investigate the role of cardiac rat troponin T on heart function using an ex vivo isolated rat heart model.

Method

Sprague-Dawley rats obtained from the Christchurch Animal Research Facility, University of Otago, Christchurch, will be used for the experiments. Using an ex vivo isolated rat heart model, a method already established in the Christchurch Heart Institute, recombinant cardiac troponin T will be administered directly into the rat heart. Hearts will be randomly assigned to either a control group, administered only perfusion buffer (Krebs-Henseleit solution) or to the troponin T treatment group. For the treatment group, recombinant cardiac troponin T will be diluted in the perfusion buffer and administered directly into the heart via a perfusion line using a syringe pump. Incrementing doses of troponin T (1 nM to 10 nM) will be used to determine the dosage required for subsequent experiments. In the next set of experiments, hearts will undergo myocardial infarction by 35 minutes of total coronary flow occlusion, followed by a 60 minute reperfusion (ischaemia / reperfusion). Troponin T will be perfused for 30 minutes either prior to ischaemia or starting at the time of reperfusion. Measures of cardiac function including contractility, left ventricular pressures and coronary flow will be made throughout the experiment.

Student researcher’s component of the study

The student will be responsible for all aspects of the isolated rat heart experiments.