An ultrastructural study of the intimal hyperplasia in healing microarterial anastomoses

The purpose of the study was to investigate the ultrastructure of intimal h yperplastic cells. End-to-end microarterial anastomoses were studied in a r abbit free-tissue-transfer model. There were five experimental groups, with 1, 3, 7, 14, or 28 days follow-up. At sacrifice the anastomoses were teste d for patency and then examined by light and electron microscopy, At days 1 and 3 the repaired intima was covered with macrophages and extravasated er ythrocytes. At day 7 spindle-shaped fibroblasts with copious rough endoplas mic reticulum were seen. Some of these cells also contained pinocytotic ves icles, filaments with focal densities, and subplasmalemmal attachment sites , the features of smooth muscle cells. At day 14, more cells contained smoo th muscle features and these features were also more pronounced. These youn g myofibroblasts were plumper than adjacent fibroblasts. At day 28 mature m yofibroblasts with a full complement of organelles were present. The result s, therefore, supported the hypothesis that myofibroblasts are present in t he intimal hyperplasia of healing microarterial anastomoses. (C) 1998 Wiley -Liss, Inc.