Immunohistochemical study of NG2 chondroitin sulfate proteoglycan expression in the small and large intestines

The intestinal subepithelial myofibroblasts (ISEMFs) are located in the lamina propria under the epithelial cells. ISEMFs are thought to have an important role in protecting and maintaining the integrity of the epithelial cell layer and also in the process of wound healing. In this study, we report that the membrane-bound proteoglycan NG2 is abundantly distributed in the ISEMF layer of the mouse and human intestines. NG2 immunostaining in this layer is distributed with similar intensity from the crypt to villi. NG2 is also immunolocalized along the membranes of smooth muscle cells in the intestinal muscle layer. However, skeletal and cardiac muscles are not immunostained for NG2, demonstrating selective expression of the proteoglycan by smooth muscle cells. Using electron microscopy, NG2 immunoreactivity was strongly observed along the cell membranes of ISEMF, with weak diffusion into the neighboring matrix, indicative of the presence of some "shed" NG2. This first report of NG2 proteoglycan expression by ISEMF provides insights into the nature of the interaction of these cells with extracellular matrix and/or intestinal epithelial cells.