Abstracts
2002 Digestive Disease Week

# 105607 Abstract ID: 105607 The Role of Angiogenesis in the Development of the Tissue-Engineered Intestine
James Gardner-Thorpe, Tracy Grikscheit, Alexander Perez, Hiromichi Ito, Anthony Ramsanahie, Stanley W Ashley, Joseph P Vacanti, Edward E Whang, Boston, MA

Introduction: Using tissue-engineering principles, we have developed a prototype neointestine. The purpose of this study was to characterize the development of the microvasculature of the engineered neointestine because (1) strategies to improve its blood supply may lead to accelerated neointestinal growth and (2) an adequate capillary network is essential for intestinal absorptive function. Methods: Intestinal organoid units were harvested from the small bowel of neonatal rats. Neointestinal cysts were generated by implanting organoid-polymer constructs into syngeneic adult recipients. 23 of these cysts were harvested at times ranging from one to eight weeks after implantation. The architecture of cysts and native bowel obtained from rats aged two to six weeks was assessed after H&E staining. Capillary density was assayed using immunohistochemical staining for CD34 and expressed as number of capillaries per total nuclei in the field. VEGF levels were measured by ELISA and normalized to total protein. Results: Over the eight week period the cysts increased in volume (0.5cm3 at week one vs. 12.6cm3 at week eight) and mass (1.3g vs 12.5g). The mucosal and submucosal layers increased in thickness and crypts became more abundant. The capillary density in the wall remained constant (mean? SEM: 82.7?9.1) throughout the duration of cyst development. The VEGF level was significantly higher in the young rat bowel than in the engineered cyst (147.6?23.9pg/mg vs 42.3?3.3pg/mg, p<0.001). The engineered cyst wall expressed a constant level of VEGF similar to that found in the wall of adult intestine at each of the time points. Conclusion: As the engineered intestine develops, it gains architectural features of normal small intestine. During this period, it is able to maintain a constant capillary density. VEGF may be useful in strategies to accelerate development of the tissue-engineered neointestine.