Evidence of interstitial Cajal-like cells in human gallbladder

Abstract

The aim of this study was to assess the presence of interstitial Cajal-like cells (ICLCs) in the human gallbladder and to determine their distinctive immunophenotypic characteristics on the basis of double immunohistochemical staining. Gallbladder specimens investigated in the study were derived from patients (8 males, mean age 51.9±10.7 y; 22 females, mean age 52.9±15.1 y) subjected to elective laparoscopic cholecystectomy for symptomatic gallstone disease. Tissue samples were fixed in 4% phosphate-buffered paraformaldehyde, processed and embedded in paraffin. Sections from gallbladders were routinely stained with hematoxylin and eosin. Tissue antigens were retrieved using heat-induced epitope retrieval (HIER) method. For simultaneous visualization of two antigens an indirect double immunofluorescence procedure was applied. Primary antibodies used in this study were rabbit anti-c-Kit (anti-CD117) and mouse anti-mast cell tryptase. ICLCs were defined as CD117-immunopositive and tryptase-immunonegative objects. They were predominantly fusiform in shape with sparse branches that were visible in some sections. ICLCs were observed throughout the gallbladder, including the fundus, body (corpus) and neck, although they were most numerous in the corpus. The ICLCs were detected almost exclusively within the muscularis propria and they were arranged parallel to smooth muscle cells. The following subpopulations of the ICLCs were observed: ICLC-IM (intramuscular ICLCs) localized between smooth muscle fibers forming one muscle bundle and ICLC-IB (interbundle ICLCs) localized within the connective tissue separating smooth muscle bundles. In the current study we confirmed the presence of ICLCs in the human gallbladder. Applied double immunohistochemistry was found to be a reliable method for identifying ICLCs and for differentiating them from mast cells.