Islet Cell Mass and the Longevity of Islet Grafts in Diabetic Rats

Abstract

In an attempt to demonstrate that a limited β-cell mass is able to maintain normoglycemia in streptozocin-diabetic rats, two groups of inbred rats received transplants of 500 or 1000 neonatal islets (corresponding to 10 and 20% of total islet cell mass, respectively) into the spleen. A close correlation was found between the functional longevity of the islet graft, and the total β-cell mass transplanted into the diabetic animals. Although euglycemia was maintained for 4-12 mo, the islet transplants were insufficient to produce glucose tolerance tests equal to those observed in normal rats. Relapse of diabetes correlated with histological findings of distorted islet architecture containing vacuolated β-cells in the grafts. This condition was not reversed after a month of normoglycemia. Spontaneous recovery of β-cell function in native islets was documented in 50% of the diabetic rats with prolonged normoglycemia following islet transplantation. This report shows that transplantation of as few as 500 neonatal islets, the equivalent of 10% of total islet cell mass, is sufficient to maintain normoglycemia in diabetic rats, albeit temporarily. A close correlation was found between the transplanted islet cell mass and the functional longevity of the islet graft.