Distribution of anionic sites in gut tissue: an electron-microscopical study

Intestinal glycosaminoglycans in neonatal necrotizing enterocolitis

Advanced necrotizing enterocolitis (NEC) is a common neonatal surgical emergency of unknown aetiology. Despite improvements in the prognosis, the aggressive form of the disease is still associated with significant rates of morbidity and mortality. Recent evidence indicates that the extracellular matrix (ECM) is important in gastrointestinal development and glycosaminoglycans, major constituents of the ECM, are attenuated in inflammatory bowel disease. The hypothesis of this study was that changes in the nature and distribution of intestinal glycosaminoglycans occur in NEC. The distribution and nature of glycosaminoglycans were determined in 31 sections of well preserved resection margins and severely diseased bowel from eight neonates affected by NEC. An established histological method of glycosaminoglycans analysis using cationic gold with silver enhancement was employed in this study. The identity of specific glycosaminoglycans was also elucidated using a combination of cationic gold staining and glycanase digestion. In well preserved tissue, staining was seen throughout the full thickness of the bowel. The epithelial basement membrane and basolateral surfaces, lamina propria and submucosa were particularly prominent. In moderate disease, patchy loss of anionic sites was frequently observed with glycosaminoglycans-deficient areas adjacent to intact sites. In severe NEC, there was extensive loss of glycosaminoglycans in most of the sections examined. Glycanase analysis revealed that the glycosaminoglycans in well preserved tissue were sensitive to chondroitinase ABC and only vascular sites were sensitive to heparinase III. The consequences of glycosaminoglycans loss in NEC as demonstrated in this study are not known but modulation of gastrointestinal glycosaminoglycans could be important in the pathogenesis of NEC and may underlie some of the clinical manifestations of this condition.