Neural cell adhesion molecule (NCAM) expression in nerves and muscle of developing human large bowel

Most studies of neural cell adhesion molecule (NCAM) in human musculature are devoted to either developing or adult skeletal and cardiac muscle. The aim of this study was to determine the pattern of NCAM expression in the intestinal musculature of the developing human large bowel. In specimens of large bowel from foetuses (gestational age 8-20 weeks), we examined the immunohistochemical localisation of NCAM in parallel to those of alpha-smooth muscle actin and desmin. Within the developing neural complex, NCAM was expressed at all stages investigated. In intestinal muscle at 8 weeks, immunoreactivity for all antisera was restricted to the muscularis propria. The differentiating muscularis mucosae was demonstrated first at 15 weeks by immunostaining for alpha-smooth muscle actin, and this expression was followed by that of NCAM and desmin at 17 and 19 weeks, respectively. At 20 weeks, NCAM immunoreactivity in the external muscle was intense at the inner border of the circular muscle, with its concentration decreasing towards the outer margin of the muscular wall, whereas alpha-smooth muscle actin and desmin were uniformly distributed in all muscle layers. NCAM is expressed by nerves and muscle of developing human large intestine. Its appearance follows a predetermined pattern, which implies its relevance to the differentiation of intestinal muscle layers.