Successful autotransplantation of microvessel fragments into the rat heart.

We examined whether microvessel fragments (Mvf), autologously transplanted with myofibroblasts (Mf) into the heart, could survive and form connections to the host's coronary microcirculation. Neither achievement has been reported before in the heart. Mvf and Mf were prepared from Sprague-Dawley rat epididymal fat pads. A mixture of Mvf (labeled with the fluorescent probe DiI-acetylated low-density lipoprotein, DiI-Ac-LDL) and Mf was injected into the superficial myocardium under general anesthesia. Rats (n = 5 in each group) were killed on postoperative days 7, 14, 21, 42 and 49, and India ink was perfused through the coronary arteries. Frozen sections of the injected area were examined under fluorescence and light microscopes. Some DiI-Ac-LDL-labeled Mvf survived in each group, and India ink was present in the lumina of microvessels coincident with DiI-Ac-LDL-labeled autotransplanted Mvf. Hematoxylin and eosin staining revealed mild inflammatory reactions followed by some fibrosis at the injection sites. These findings indicate that autotransplanted Mvf can survive for at least 49 days, and that patent microvascular anastomoses can form between them and the host's coronary microvessels. Possibly, autotransplantation of Mvf could lead to the development of a new collateral microcirculation, a phenomenon especially important in the ischemic heart.