Cardiotoxicity is one of the main reasons for drug withdrawals, accounting for 45% of all drugs taken off the market between 1994 and 2006. Establishing in vitro screens at the early phases of drug development is critical in preventing late stage failure.
Cyprotex offer both standard and novel approaches for assessing cardiotoxicity. Much of our research in the field of cardiotoxicity has focused on the area of iPSC-derived cardiomyocytes, whole cell microelectrode array and 3D triculture models. We also offer a CiPA single ion channel panel including Nav1.5, Kv4.3 (Ito), hERG (IKr), KvLQT1/minK (IKs), Cav1.2 and kir2.1 (IK1).
Cyprotex have specific expertise in the development of 3D cell-based models, and much of our research focuses in this area. One important consideration is that the myocardial tissue only comprises 30% cardiomyocytes with the remaining 70% being non-cardiomyocytes (predominantly endothelial and fibroblast cells). These non-cardiomyocytes are essential to myocardial structure and function and emerging evidence suggests that they play a role within drug-induced cardiovascular toxicity.
Cyprotex have developed cardiac 3D triculture microtissues formed from cardiomyocytes (iPSC-derived), cardiac fibroblasts and cardiac endothelial cells. These models spontaneously beat as shown in the videos below and are amenable to long term culture and so are ideal for repeated dose exposure studies.
The microtissues display uniform size and shape with a diameter of 200µm and whole mount immunofluorescense displays even distribution of key cell markers throughout the microtissues as shown below.
Cyprotex have invested in confocal high content screening for imaging the microtissues and enables a complete analysis of the entire microtissue through Z-stack analysis. These images are illustrated in the videos below.
Cyprotex have considerable expertise in microelectrode array being one of the first companies to launch a high throughput MEA service using iPSC-derived cardiomyocytes (eCiphr®Cardio). Cyprotex is also heavily involved in the CiPA initiative where as part of the MEA sub-team have a vital role in the evaluation and development of new testing methods.
For eCiphr®Cardio, a highly purified population of cardiomyocytes, which are differentiated from human induced pluripotent stem (iPS) cells, are used. These cells are a mixture of spontaneously electrically-active atrial, nodal and ventricular-like myocytes which beat in synchrony and exhibit expected electrophysiological and biochemical responses upon reference drug exposure.
Using this system, an ECG-like recording can be monitored following test compound exposure. Example traces are illustrated below:
The following parameters can be recorded
Conduction velocity can also be measured. This is defined as the speed at which the signal is translated from a first depolarization event observed in one cell to the depolarization event in an adjacent cell, which results in a wave of activation. In the example below, the effect of lidocaine on the conduction velocity is illustrated. The conduction velocity increases while the amplitude decreases with larger doses of lidocaine.
Unlike single ion channel patch clamp measurements, eCiphr®Cardio assesses changes in all major ion channels implicated in an action potential, and so is capable of detecting the effects on the hERG channel, calcium channels, sodium channels and beta adrenergic receptors. By assessing a longer time course, it is also possible to detect hERG trafficking effects using eCiphr®Cardio.
Cyprotex offer the full panel of single ion channel assays currently being assessed within the CiPA initiative. We can offer gigaseal recordings using automated patch clamp (Cytopatch4). The ion channels available include:
Contact Cyprotex to find out more about our ion channel panel.
Prolongation of the so-called QT interval, which reflects the time between heart’s ventricular depolarization and repolarisation is a common reason for cardiotoxicity. Virtually all drugs that prolong QT interval block the delayed rectifier K+ current (Ikr), which is responsible for repolarization. The prolongation of the QT interval has been associated with torsade de pointes (TdP), which may lead to ventricular arrhythmia and consequently sudden cardiac death.
However, TdP is not always associated with QT interval prolongation and not all Ikr blockers cause QT prolongation or TdP. It is thus critical to design assays that can examine the effects of drug candidates on the entire action potential and thereby uncover all potential mechanisms behind drug-induced cardiotoxicity.
Utilizing cell-based assays, Cyprotex are able to assess single ion channel effects by measuring hERG inhibition in an automated patch clamp system (Cytopatch4 or Ionworks™ Quattro), as well as whole cell electrophysiology using microelectrode array (eCiphr®Cardio).