Gene therapy broadly refers to the transference of DNA into cells to modify them for specific purposes. One hope is that human stem cells could be genetically engineered to be glucose-responsive insulin. secreting cells. If such cells could be grown, then they could be mass-produced so that anyone with diabetes could be freed of their disease with a cell transplant. And perhaps the cells could be engineered to avoid rejection by the immune system.
It is difficult to grow cells that make insulin because the property of glucose-responsive insulin secretion is very complex and delicately balanced. Scientists have had success in mice and are working to develop cells that can be used in humans.