In the search of potential human islet stem cells: is tetranectin showing us the way?

Pancreatic islet cell transplantation is a promising approach to restore the required mass of functional beta cells in diabetic patients as a means to achieve long-term normoglycemia. This therapy is, however, not yet widely used, in part because of the shortage of human islet cells. Gaining detailed knowledge of the physiological basis governing the processes of differentiation of pancreatic stem or progenitor cells and the mechanisms and molecules necessary for a successful engraftment of the transplanted cells into the liver is instrumental for the ambitious goal of engineering new pancreatic islets to cure type I diabetes. We describe the in vivo and in vitro localisation of tetranectin (TN) in human and murine islet cells. Similar to human islets, murine islets stain positive for tetranectin. The amount and localization of TN is influenced by different culture conditions. The ability of TN to bind plasminogen indicates that it may have a role in regulating pericellular proteolysis and proteolytic activation of latent forms of metalloproteinases and growth factors. Tetranectin may thereby play an important role in the survival of islets in the liver after islet transplantation. TN-positive cells can be isolated and maintained in culture after human islet isolation, thereby providing the possibility to further clarify its role and function in vivo as well as in the course of islet transplantation.