Evaluation of Cardiac Graft Function by Echocardiography in Mice

Abstract

Generally, graft function in the murine cardiac allograft transplant model is assessed daily by palpating the heart for evidence of contraction. To our knowledge, few reports have investigated the correlation of cardiac graft function using echocardiography and immunohistochemical studies. In this study, we investigated the efficacy of echocardiographic and histologic evaluation of alloimmune responses in the acute phase of murine cardiac allografts. Fully vascularized heterotopic hearts from CBA (allogeneic group) or C57BL/6 (syngeneic group) donors were transplanted into C57BL/6 recipients using microsurgical techniques. Fluctuations in heart rate, left ventricular ejection fraction (LVEF), left ventricular functional shortening (LVFS), right ventricular outflow tract maximal systolic velocity (RVOT Vmax), and RVOT velocity time integral (RVOT VTI) were evaluated on postoperative days (PODs) 1, 3, 5, 7, and 9 after transplantation using an ultrasonic device. Histologic studies were also performed. The syngeneic group did not show a complete cessation of heartbeat or deterioration of cardiac function. CBA recipients in the allogeneic group rejected cardiac allografts on POD 9 after grafting. LVEF and LVFS in the allogeneic group gradually decreased on POD 9. Consistent with the time-course echocardiographic evaluation, histologic studies showed gradual atrophy of the left ventricle. In contrast, RVOT Vmax and RVOT VTI in the allogeneic group were not significantly different during the observation period. Additionally, the thickness of the right ventricular wall did not change until POD 7. The present findings suggested that echocardiography may help to evaluate time-course murine cardiac graft function through left ventricular parameters such as LVEF and LVFS.