Human placenta: de visu demonstration of interstitial Cajal-like cells

Traditional interstitial cells of Cajal (ICC) are present in the digestive tube and are supposed to act as pacemakers and neuromodulators. However, interstitial Cajal-like cells (ICLCs) were found outside the gastrointestinal tract, in various organs (e.g. ureter, bladder, fallopian tube, uterus, pancreas, mammary gland, myocardium etc.) and looking for such ICLC is a priority in our laboratories. We report here unequivocal visual evidence that ICLCs are present in the mesenchymal tissue of the villi from human term placenta. The following methods were used: a. vital staining with methylene blue (cryosections); b. silver impregnation (paraffin sections); c. Epon-embedded sections (approximately 1 microm) of glutaraldehyde/osmium fixed tissue, stained with toluidine blue; d. primary cell cultures (or second-passage cells) to reveal the characteristic, very long, moniliform cell processes and mitochondrial localization at dilations (molecular fluorescence probe: Mito Tracker Green); e. immunofluorescence for c-kit/CD117 marker or other characteristic proteins; f. transmission electron microscopy to establish the identity of ICLC.