The Biological Significance Of Tunneling Nanotubes Between Cells In Vitro.

Objective The signal transduction and cellular interaction are necessary in various multi cellular organisms. Recently, a novel cellular communication structure, named tunneling nanotubes(TNTs), has been found in vitro with a diameter of 50 to 200nm , which is similar to intercellular bridges (IBs) in vivo. Recently, researchers have focused their attention on the roles of cell communication between tumor cells in the treatment of cancer. This experiment was carried out to understand the formation and roles of TNTs between cultured tumor and normal cells.Methods The morphological features and the trend of formation of TNTs were observed under inverted phase contrast microscopy. The HepG2 cells or Chang Liver cells were stained with DiI or DiO respectively and movement of the vesicles via TNTs was analyzed by inverted fluorescence microscopy. In order to find out whether the TNTs could be formed between HepG2 cells and Chang Liver cells, the two cell lines were marked with different lipophilic stains, co-cultured and analyzed by confocal microscopy.Results The formation of TNTs has been found between HepG2 cells or Chang Liver cells, and the numbers of TNTs get increased with the progression of culturing. The transfer of DiI-labeled organelles along TNTs was found to be uni-directional and discontinuous. The formation of TNTs between HepG2 cells and Chang Liver cells has also been observed. The TNTs came from the latter and the marked vesicles from Chang Liver cells could be transferred into HepG2 cells via TNTs.Conclusions Tunneling nanotubes are one of the universal structures involved in the cell communication in vitro. The vesicles can be transferred uni-directionally via TNTs. The vesicles of Chang Liver cells can move into HepG2 cells via TNTs, which were formed from Chang Liver cells.