New composite tissue allograft transplantation model in mouse with intravital microscopic evaluation of microcirculation

A new mouse composite tissue allograft (CTA) transplantation model was developed. to study the microcirculatory changes during acute allograft rejection and ischemia/reperfusion (I/R) injury. The donor cremaster muscle allografts were prepared as a tube flap, harvested on the common iliac vessels, transplanted to the neck region of the recipient, and anastomosed to the recipient's ipsilateral carotid artery and external jugular vein using standard end-to-end microsurgical technique. In Group 1 (n=6), the hemodynamics of cremasteric muscle microcirculation was measured in C57BL/6N mice without transplantation for baseline data. In Group 2 (n=6), isograft transplantations were performed between C57BL/6N mice. In Group 3 (n=5), allograft transplantations were performed across a high histocompatibility barrier between C3H and C57BL/6N mice. Following transplantation, cremaster muscle tube flaps were prepared for standard microcirculatory measurements of functional capillary perfusion, diameters, and red blood cell (RBC) velocities of 1(st), 2(nd), and 3(rd) order arterioles and venules, and numbers of rolling, adhering, and transmigrating leukocytes and lymphocytes. Hemodynamic Parameters of microcirculation did not differ significantly between the three groups. However, the number of rolling, adhering, and transmigrating polymorphonuclear leukocytes and lymphocytes was significantly increased in the allograft group (p<0.001) as early as 2 hr following transplantation. Cremaster muscle transplantation in mice is a reliable and reproducible model with a 95 percent immediate success rate. The model offers the unique possibility of studying leukocyte-endothelial interaction during acute allograft rejection and I/R injury in mouse.