Platelet-derived growth factor receptor α-positive cells in the tunica muscularis of human colon

An obstacle to understanding motor pathologies of the gastrointestinal (GI) tract is that the physiology of some of the cellular components of the gut wall is not understood. Morphologists identified fibroblast-like cells in the tunica muscularis many years ago, but little is known about these interstitial cells because of inadequate techniques to identify these cells. Recent findings have shown that fibroblast-like cells express platelet-derived growth factor receptor a (PDGFRa) in mice and that antibodies for these receptors can be used to label the cells. We used immunohistochemical techniques to study the phenotype and intercellular relationships of fibroblast-like cells in the human colon. Fibroblast-like cells are labelled specifically with antibodies to PDGFRa and widely distributed through the tunica muscularis of human colon. These cells form discrete networks in the region of the myenteric plexus and within the circular and longitudinal muscle layers. Platelet-derived growth factor receptor a+ cells are distinct from c-Kit+ interstitial cells of Cajal and closely associated with varicose processes of neurons expressing substance P (excitatory motor neurons) or neuronal nitric oxide synthase (nNOS) (inhibitory motor neurons). Platelet-derived growth factor receptor a+ cells express small conductance Ca2+-activated K+ channels (SK3), which are likely to mediate purinergic neural regulation of colonic muscles. Our data suggest that PDGFRa+ cells may have an important role in transducing inputs from enteric motor neurons. This study identifies reagents and techniques that will allow investigation of this class of interstitial cells and help develop an understanding of the role of PDGFRa+ cells in the human GI tract in health and disease.