Biphenotypic surface epithelial cells in the gastrointestinal tube with mixed epithelial-myofibroblastic differentiation: a paradigm.

Epithelial cells and myofibroblasts are well-characterized histomorphological elements of tissues. They are distinguished from one another on the basis of topography and of differences in cytokeratin (CK) and α-smooth muscle actin (SMA) expression. Certain epithelial cells exhibit CK / SMA co-expression. This study aimed to define the immunophenotypical characteristics of these biphenotypic cells with respect to cytodifferentiation (broad spectrum of CKs, SMA), cell-cell interaction (E-cadherin, adenomatous polyposis coli - APC, β-catenin), and cell survival (cyclooxygenase-2 - Cox-2). At the routine gastrointestinal pathology service of the Department of Pathology, University of Szeged, tissue samples were identified from instances of cervical inlet patch (n = 5), Barrett's esophagus (n=5), gastritis (n=5), fundic gland polyp (n=2), gastric neoplastic polyp (n=1), inflammatory bowel disease (n=5), and colonic neoplastic polyp (n=3). that contained epithelial cells expressing SMA. These biphenotypic cells were further immunophenotyped. Foregut-derived biphenotypic cells expressed CKs 7 and 20, while hindgut-derived biphenotypic cells expressed only CK 20. Subepithelial myofibroblasts adjacent to biphenotypic epithelium expressed Cox-2, SMA, and β-catenin, as did biphenotypic cells. Myofibroblasts, however, did not express CKs. In neoplastic polyps, APC expression weakened as cytologic atypism increased, while intermingled biphenotypic cells in neoplastic glands overexpressed APC, as did myofibroblasts beneath. CK subspecies expression in biphenotypic cells reflects embryonic development of the gastrointestinal tract. The immunophenotyping analysis addresses bidirectional (via transdifferentiation from epithelia into myofibroblasts or vice versa) formation of biphenotypic cells within damaged epithelium, a phenomenon that must be further analysed.