Human iPSCs in inherited cardiomyopathies

Recent advances in genetic technology unraveled novel disease genes for inherited cardiomyopathies. However, the cellular and molecular mechanisms leading to the disease remain poorly understood. Patient-specific model systems such as human induced pluripotent stem cells (hiPSCs) and the development of in vitro generated individual cardiomyocytes (CMs) provide new insights in the pathogenesis and may help to individualize therapeutic approaches. The effects of specific mutations within the remaining patient-specific genetic background plays an important role to understand modifying factors influencing penetrance and expressivity of disease features which are often different even between family members.

Therefore, isogenic controls generated by CRISPR-Cas9 technology are used for direct comparison of iPSC derived CMs. Other concerns such as the acceleration of maturation and the formation of sarcomeres in vitro are addressed by mechanical and electrical stimulation protocols. Our goals are focused on the characterization of pathological changes displaying clinical features of hiPSC derived CM from different cardiomyopathy patients compared to their isogenic controls.

Question: What are human induced pluripotent stem cells (hiPSCs)?
Answer: Human iPSCs are embryonic stem-like cells that have been reprogrammed from somatic cells (e.g. dermal fibroblasts) using a transfection vector and a well-defined set of embryonically expressed pluripotency factors (four `Yamanaka Factors`: OCT-4, SOX-2, Klf4, c-Myc). Similar to human embryonic stem cells (ESC), hiPSCs self-renew and can differentiate into cells of all three germ layers (endoderm, mesoderm, and ectoderm).

Question: What are inherited cardiomyopathies (CMPs)?
Answer: Inherited CMPs are diseases that affect the heart muscle leading to heart failure and sudden death. Different types of CMPs include hypertrophic CMP (HCM), dilated CMP (DCM) and arrhythmogenic (right ventricular) CMP (ACM) and even more rare subtypes. 

Question: What is CRISPR/Cas9 technology?
Answer: CRISPR (clustered regularly interspaced short palindromic repeats)/Cas (CRISPR-associated) system has been developed as an efficient and versatile technology for genome editing in eukaryotic cells and whole organisms. This technology can be engineered to induce Cas9-mediated double-stranded breaks (DSBs) in a sequence-specific manner. The resulting DSB will either generate nonspecific mutations knocking out a gene through the error-prone NHEJ (nonhomologous end joining) pathway, or produce specific modifications dictated by an exogenous repair template through the HDR (homology-directed repair) pathway.