The acute inflammatory response occurs immediately after AR and ZA microinjection in neonatal mouse hearts. (A) Immunostaining for Ly-6G (1A8) at 1 day post-resection (dpr) in the neonatal mouse heart. The high-magnification views of the boxed areas are presented on the right. AR, apical resection; scale bars, 100 μm. (B) qRT-PCR assays of the expression of inflammatory markers (il6, il1b and ccl3) in sham and AR hearts at 1, 4 and 7 dpr. Gene expression in AR hearts is presented as the fold change compared to sham hearts. n = 3 per group. (C, D) Apical intramyocardial microinjection of ZA into the neonatal 1-day-old mouse heart. ZA was conjugated with Alexa Fluor® 488 to track its distribution in the cardiac apex. The high-magnification views of the boxed areas are presented on the right. dpm, days post-microinjection. Scale bars, 100 μm. (E) Immunostaining for Ly-6G (1A8) in the PBS and ZA micro-injected apical myocardium at 1 dpm in neonatal mice. The high-magnification views of the boxed areas are presented on the right. Arrows indicate Ly-6G (1A8)+ leukocytes. Scale bars, 100 μm. (F) qRT-PCR assays of the expression of inflammatory markers (il6, il1b and ccl3) at 1, 4 and 7 dpm. Gene expression in the ZA micro-injected hearts is presented as the fold change compared with PBS micro-injected hearts. n = 3 per group; values are presented as the mean ± SEM; *P < 0.05.