Background: Long-term maintenance of the phenotype of beta cells in vitro is difficult. The objective of this study was to examine an in vitro method for preserving the capacity of adult human beta cells to express insulin. We evaluated the use of long-term cultured islet cells for the treatment of diabetic SCID mice.
Methods: Human islets were isolated from cadaveric donors. The islets were cultured as monolayers and clusters in repeating cycles for 4 months. Thereafter, the cells were tested in vitro for their capacity to express insulin and to secrete insulin in response to glucose challenge. Finally, the cluster-cultured cells were transplanted under the kidney capsule and into the kidney tissue in streptozotocin (STZ)-induced diabetic SCID mice.
Results: Approximately 3.6% of cultured islet cells in cluster phase expressed insulin at 4 months and this was confirmed using immuno-gold-labeling electron microscopy. The cultured islet cells secreted insulin in response to glucose challenge in a dose-dependent manner. After transplantation, the islet cells redifferentiated and generated >20% insulin positive cells. The 4-month cultured cells rendered the blood glucose level near normal in mild diabetic mice (7.25 mM+/-1.595 vs. 15.225 mM+/-2.55, P<0.0025).
Conclusion: It is possible to preserve the capacity of adult human islets to express insulin over a 4-month period in vitro, and this capacity was enhanced significantly by transplantation into SCID mice. The described system will be useful in studies of beta cell proliferation and differentiation.