Abstract 12467: Engineered Somatic Cells for Cardiac Repair
The implantation of cardiogenic cells in the heart is currently being investigated as a potential treatment for ischemic heart disease. While large numbers of functional cardiomyocytes can be generated from pluripotent stem cells at this time, their implantation may result in sustained tumorigenic and arrhythmogenic risks. Alternatively, the use of engineered somatic cells may offer a safer and more efficient route to cell-based cardiac therapy. As a proof-of-concept, we genetically engineered a novel excitable cell source from human unexcitable cells (HEK293) through the stable expression of connexin-43 gap junctions, fast sodium (INa) and inward rectifier potassium (IK1) channels. A monoclonal engineered cell line with a resting potential of -74.2±0.8 mV, rapid action potential upstroke (150.3±7.2 V/s), short action potential duration (APD=18.6±1.0 ms), and high coupling strength (134.1±14.0 nS) was used to generate confluent cell networks that supported active impulse conduction (23.3±0.6 cm/s) at high pacing rates (up to 26.5±0.6 Hz). These cells effectively restored 2D conduction blocks (> 1 cm in diameter) and reconnected remote (> 2.5 cm apart) islands of neonatal rat ventricular myocytes (NRVM) in vitro as shown by optical mapping of membrane potential and intracellular calcium transients. Similarly, excitable 3D HEK293 tissue bridges repaired large conduction gaps within 3D engineered cardiac tissues. At a microscopic scale, the interface between engineered HEK293 cells and NRVMs in 2D strands exhibited a significant APD gradient (> 220 ms/mm) despite no gradient in conduction velocity. To reduce this large APD gradient, a T-type Ca2+ channel was stably expressed in the excitable HEK293 cells which significantly prolonged their APD to 259.5±31.2 ms. Interestingly, partial block of IK1 by application of BaCl2 in networks of these cells yielded spontaneous action potential activity (0.5–3 Hz rate) suggesting the potential to bioengineer autonomous pacemaking cells. In conclusion, we demonstrate the generation of novel engineered excitable cell sources with defined and tunable electrical properties. This in vitro platform represents an important step towards the rational design of future somatic cell therapies for cardiac repair.
- © 2010 by American Heart Association, Inc.