Experimental model for neoangiogenesis in adhesion formation

This study presents an animal model for the observation of adhesion formation, from a vascular viewpoint. In 60 Wistar rats, a 4 cm midline incision was made and a 0.5 cm square piece of silastic 0.2 mm thick was fixed on the right side of the peritoneum with two separate angular stitches of nylon 9/0. The rats were randomized in six groups of 10 animals and were operated on again on days 2, 4, 6, 8, 10 and 12 respectively. Biopsies for scanning electron microscopy were obtained by resecting a 2 x 2 cm square of parietal peritoneum around and covering the silastic patch. Foreign body reaction induced by the silastic patch and ischaemia caused by stitching are the stimuli for adhesion formation. The results showed a gradual progression in the type and tenacity of adhesion formation. The maximal degree of peritoneal reactive angiogenesis was noted between days 8 and 12, together with a decrease and a redistribution in the extent of adhesions. In the early stages, vascularization is part of the organization of adhesions while their extent is limited. Two parallel mechanisms take part in trauma healing: while omento-parietal adhesions are vascularized, new peritoneal tissue with its vascular network develops and covers the silastic surface and the traumatized area. This theory is supported by the presence of fibroblasts differentiating into mesothelial cells on day 8. Theoretically, a valid treatment in preventing adhesion formation should increase the peritoneal neoangiogenesis and the repair of peritoneal lesions, but at the same time prevent the vascularization of adhesions. The present model offers the possibility of testing the effect of any treatment or device for preventing post-operative adhesions in a relatively short time.