Regeneration of sinus node〜 reconstitution of biological pacemaker using bio-nanotechnololgy

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We constructed cardiac pacemaker sheets using a novel technique with patterning of cell alignment. Natural killer cell-1 antibody-conjugated magnetic nanoparticles (AM) 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(14.5d.p.c.) were incubated with AM 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. In MAO the AM-labeled CM were aggregated over a magnet, whereas in CONT, the AM-labeled CM were randomly distributed among the unlabeled CM. Extracellular potentials recording revealed that regular spontaneous excitation originating from the aggregation of AM-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(16±3 vs 11±2 bpm, p<0.05, n=5). The addition of isoproterenol(1μM) increases the spontaneous beating rate in both MAG and CONT. [Ca^2+] ; transients of transplanted embryonic CM and recipient neonatal CM were well synchronized in MAG 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.