A Modified Neonatal Mouse Cardiac Apicoectomy Model: Reproducibility and High Survival Rates.

Neonatal mouse heart apical resection (AR) can induce cardiac tissue regeneration. However, conventional AR models lack precise parameters for cryoanesthesia duration, thoracotomy site, and ambient temperature. We varied cryoanesthesia time, ambient temperature, and thoracotomy location to quantify blood loss, and survival rate. After surgery, RT-qPCR, immunofluorescence, and Masson staining were used to track AR model. Iterative testing showed that 4 min 30 s of cryoanesthesia followed by a 10-min delay at 24-28°C maintained complete cardiac arrest, providing a stable operative window. A fifth-intercostal thoracotomy, performed by gently compressing the lactating pup's back and dilating the thorax with blunt forceps, minimized bleeding and markedly improved survival. The refined AR protocol reproducibly elicits structural injury, transient functional impairment, and subsequent regenerative repair in P1 neonatal mouse hearts.