Abstract 643: Engineering of Functional Cardiac Pacemaker Sheets by Patterning of Cell Arrangement Using Magnetic Nanoparticles
[Background] Sophisticated architecture of the sinoatrial (SA) node is crucial for its robust pacemaking activity under a variety of pathophysiological conditions. Biological pacemaker created by cell-transplantation may therefore require specific cell patterning to improve its feasibility.
[Methods] Natural killer cell-1 antibody-conjugated magnetolipsome (NK-AML), which contains magnetite nanoparticles (diameter ~10 nm), was prepared to label rat cardiac specialized conduction system. Cardiomyocytes (CM) isolated from the GFP expressing rat embryo (14.5 d.p.c.) were incubated with NK-AML and dispersed on a culture dish with 64 multielectrodes. A small magnet was placed under the dish to arrange labeled CM (MAG group, n=5). CM cultured without magnet were referred as control (CONT group, n=5). After 3 days, extracellular potentials were recorded to examine pacing and conduction properties. Cultured CM of MAG group were transplanted on a sheet of cultured CM from neonatal rats. Three days later, both donor (embryo) and recipient (neonate) CM were loaded with Rhod2 and [Ca2+]i transients were recorded using a high-speed CCD camera to estimate electrical interaction between donor and recipient CM.
[Results] In MAG, the NK-AML-labeled CM were aggregated over a magnet, whereas in CONT, the NK-AML-labeled CM were randomly distributed among the unlabeled CM. Extracellular potentials recording revealed that regular spontaneous excitation originating from the aggregation of NK-AML-labeled CM propagated regularly over surrounding unlabeled CM. CONT, in contrast, showed considerable wondering of pacemaker sites in association with irregular propagations including spiral-type reentry. In addition, spontaneous beating rates in MAG were significantly faster than CONT (36±3 vs 22±2 bpm, p<0.05, n=5). The addition of isoproterenol (1 μM) increases the spontaneous beating rate in both MAG and CONT. [Ca2+]i transients of transplanted embryonic CM and recipient neonatal CM were well synchronized in MAG.
[Conclusion] The patterning of cell arrangements using magnetic nanoparticles could be a novel technique to engineer well-organized cardiac sheets for creation of dependable biological pacemaker.