**Abstract**

Pancreatic islets contain beta cells which produce insulin based on the blood glucose levels resulting in tight control of blood glucose levels. In type 1 diabetic patients, most of the beta cells are destroyed, therefore, pharmaceutical insulin injection is mandatory to avoid diabetes-related illness and death. Even with recent advanced insulin therapy, hypoglycemia is a critical limiting factor to control blood glucose levels. There is no doubt that hypoglycemia can be fatal. Allogeneic islet transplantation can prevent severe hypoglycemia and provide excellent blood glucose control. On the other hand, allograft donor shortage is the major issue. To overcome donor shortage, xenograft has been used and shown safety and efficacy. Recently stem-cell-derived beta cells are clinically applied. In this chapter, the history and current status of allogenic islet transplantation and future scope are described.

**Keywords:** islet transplantation, allograft, type 1 diabetes, hypoglycemia, xenogeneic islet transplantation

### **1. Introduction**

Type 1 diabetes is a devastating disease due to its acute and chronic complications. Acute complications include hyperglycemic ketoacidosis and hypoglycemic attack, and both complications can be life-threatening. Chronic complications include nephropathy which leads to the necessity of hemodialysis, retinopathy which leads to blindness, and neuropathy which causes necrosis of the legs and the necessity of amputation.

Intensive insulin therapy is the gold standard for type 1 diabetic patients, which significantly reduces the risk of chronic complications and mortality rates [1]. However, intensive insulin therapy was associated with weight gain and a threefold increased risk for hypoglycemia [1], and hypoglycemia is a limiting factor for intensive insulin therapy [2]. Indeed, 4–10% of type 1 diabetic patients died due to hypoglycemia [3].

Since the cause of type 1 diabetes is destruction of insulin-secreting beta cells, beta cell replacement therapies are curative treatments [4]. Beta cell replacement therapies include the pancreas and islet transplantation. Allogeneic islet transplantation can

prevent severe hypoglycemia and provide excellent glycemic control. On the other hand, donor shortage is a major issue. In this chapter, the current situation of allogenic islet transplantation and potential resolution of donor shortage is described.
