The hiPSC Cardiomyocyte Characterisation and validation Assay (hiPSC-CM) technology allows for the high-throughput production of patient-specific cardiomyocytes and other cardiac cell types. The method also facilitates the extensive evaluation of drug effects with well-established tools such as multielectrode array (MEA), patch clamp, and calcium ion oscillation measurements. In addition, the hiPSC-CM model provides a predictive model of human response to drugs.
Compounds used in the assay
The HiPSC Cardiomyocyte Assay uses various compounds to test cardiomyocytes for metabolic flexibility. Using a range of different substrates, metabolic activators and inhibitors, and biochemical cues such as insulin, we can evaluate the cardiomyocyte’s ability to use these compounds to produce energy.
Human stem cell-derived cardiomyocytes are increasingly being used in drug discovery, toxicity assessment, and cell-based disease treatments. Cardiovascular toxicity is of particular concern in the context of drug discovery, and the CiPA assay can help make informed decisions regarding the safety of new drugs. In addition, the assay is a promising step in the development of novel drugs, and it will enable scientists to identify potential cardiotoxic pills earlier.
Expression profile of targets involved in generating the cardiomyocyte AP
The cardiac action potential (AP) is triggered by a stimulus that depolarizes the myocyte’s membrane. This cellular response results from opening a Na+ or Ca2+ channel on the membrane. The efficacy of this response depends on the magnitude of the stimulus, the efficiency of the stimulus current, and the cell’s excitability. In addition, cardiac myocytes are linked by gap junctions, which allow low resistance ion flow.
Expression profiling of cardiac proteins offers an innovative approach to identify novel pathomechanisms in human cardiac diseases. Currently, most animal models display significant differences from human disease. However, by restricting the disease phenotype, genomic approaches can identify new therapeutic targets and mechanisms. Recent studies have shown that APN is localized in human hearts and downregulated in DCMi patients. These findings suggest that localized APN may play a role in regulating cardiac inflammation and protect the heart.
Two-dimensional versus three-dimensional culture system
HiPSC-CM differentiation systems are costly, requiring high growth factors and long concentration optimization times. Despite this, researchers have made strides to simplify the differentiation process and produce more reproducible results. One such differentiation platform was developed using rice-derived recombinant human albumin, RPMI 1640, and L-ascorbic acid 2-phosphate.
Using a microfluidic device, the researchers generated a common culture medium for hiPSC cardiomyocytes and endothelial cells. In this system, cardiomyocytes grew in a 3D matrix at the central part of the microfluidic chip, while endothelial cells grew in two lateral channels. In both cultures, the medium flow mimicked the microvasculature. After seven days of cell culture, the two cell types showed identical phenotypes, viability, and cellular-to-cell junctions.
Mechanical stretch
The results show that mechanical stretch regulates the gene response in hiPSC cardiomyocytes. Moreover, mechanical load also influences connective tissue and vascular cells. The mechanism behind this is that it triggers the activation of MAPKs, which are key players in the conversion of mechanical signals into physiological responses. These proteins are present in fibroblasts, endothelial cells, and vascular smooth muscle cells. Moreover, it has also been demonstrated that mechanical stretch triggers the expression of a number of proto-oncogenes in cardiac myocytes.
The study further demonstrated that the gene expression response to mechanical stretch is dependent on phenotypic changes in cardiomyocytes. For example, when cardiomyocytes undergo biaxial stretching or cyclic stretching, there is a differential expression of genes in NRVMs and cardiac myocytes. However, the results suggest that these changes only occur after a 24-hour stretch.
Predicting changes in clinical QTc interval
A patient of French-Canadian descent with polymorphic premature ventricular contractions and frequent nonsustained ventricular tachycardia was evaluated for QTc interval. His ECG revealed an important ventricular ectopy at rest, but his QTc interval and Q-U interval were normal. A subsequent echocardiogram and a Holter monitor demonstrated ventricular tachycardia.
In their study, the authors characterized 27 iPSC-CM cell lines. All cell lines were obtained from healthy donors. The optimal number of cell lines will depend on the TQT study endpoint and hazard identification. In addition, the number of cell lines will vary depending on the concentration of the drugs and genetic susceptibility.
