By taking spleen cells and transplanting them into the pancreas of diabetic mice. The spleen cells caused the mouse pancreas to regenerate including the insulin producing Islet cells. Human clinical trials are just starting and will take at least five years. Source: Iacocca interview on Fox's Your world with Cavuto.
Questions: What of people whose spleen has been removed? What of people whose diabetes is due to insulin receptor deficiencies in all cells? IOW it will not cure one type of diabetes and some few people will be unable to undergo the procedure without organ or at least cell donation if it works in humans. Still it is encouraging.