Cardiomyopathies are life threatening heart muscle disorders that often run in families. The disease takes many forms, all of which place patients at risk for pathological heart remodeling, sudden cardiac death, and heart failure. While no cure exists, physicians can reduce the impact of the disease if it is caught in its early stages. Early detection schemes currently rely on genetic testing, to see if an individual carries one of the ~1400 known cardiomyopathy mutations. If a new cardiomyopathy patient happens to carry a known mutation, their family members can be meaningfully screened. Those carrying the mutation will receive preventative care, while non-carriers can be safely excused from clinical follow-ups and relieved of undue anxiety. Unfortunately, only 40-60% of cardiomyopathy patients test positive for a verified mutation. The rest, comprising roughly half of all patient families, cannot benefit from genetic testing for early diagnosis unless further steps are taken. The options for such families are limited. Co-segregation analysis can be performed in families of sufficient size and may identify a novel gene mutation, but this result is not guaranteed. If th family is small or otherwise unsuited for co-segregation study, all first-degree relatives must be periodically tested for signs of emerging disease - even though there is a 50% chance that they do not carry the mutation. Hence, in cases where genetic testing results are indeterminate, a more robust, single-repetition method for early detection of cardiomyopathy inheritance is badly needed. Induced pluripotent stem cells (iPSC), derived from a person's own somatic cells by expression of pluripotent stem cell factors, may provide a solution. We envision an approach in which iPSC-derived cardiomyocytes (iPSC-CMs) are generated from a patient and formed into engineered heart tissue (EHT) for in vitro study. We hypothesize that abnormal behavior measured in EHTs will reflect direct effects of any mutations present. As such, these phenotypes could act as surrogate markers of inheritance. By testing EHTs of each family member, the pattern of inheritance could be established regardless of the subjects' ages, and without requiring a large family, as in co-segregation analysis. With this specific goal in mind, w have developed a novel strategy to generate EHTs that are ideal for biomechanical phenotyping. We produce these ribbon-like specimens by seeding cardiac cells into thin, laser-cut sections of decellularized porcine myocardium. Initial tests with neonatal rat ventricular myocytes have yielded spontaneously beating EHTs that produce measurable contraction forces and can survive months in culture. The goal of this project is to assess the true potential of this exciting new technology by generating EHTs with iPSC-CMs from control and diseased subjects. We can then test the ability of our system to reproducibly detect the phenotypic consequences of even clinically mild mutations. The successful completion of our aims will be an important step toward an alternative to genetic testing for the early identification of individuals who are at risk of developing cardiomyopathy.
Roughly 600,000 individuals in the United States suffer from intrinsic cardiac muscle disorders known as cardiomyopathies, and because the disease can be caused by gene mutations there are numerous family members of these individuals who also at high risk of being affected. Early identification of cardiomyopathy inheritance allows physicians to intervene in the progression of disease, but at present genetic testing is the only reliable approach to early identification and in roughly half of all cases it fails to give a conclusive reslt. The goal of this project is to use induced pluripotent stem cells to grow engineered heart tissue from patients and their first degree relatives in an attempt to uncover biomechanical phenotypes that can be used as surrogates for genetic markers when these are unavailable.
