Endocrine Abstracts

The need for new therapeutic options in diabetes has become increasingly apparent. Until recently transplantation of isolated islets has had limited success. The Edmonton Protocol has described how many of the problems can be overcome, but has highlighted the need to develop methods of expanding islets cells in culture to provide sufficient tissue to meet the potentially huge demand for this treatment. We have focused on three approaches: 1. deriving replicating human Beta cell lines from islet tissue from patients with Persistent Hyperinsulinaemic Hypoglycaemia of Infancy (PHHI), 2. engineering non Beta cell lines; and 3. muscle-directed gene therapy.

In collaboration with colleagues in London, Leicester and Sheffield a human Beta cell line, NES2Y, has been derived from PHHI tissue. NES2Y cells are poorly glucose responsive and have elevated rates of insulin release under basal conditions, a phenotype that fits well with the PHHI pathology. They do not possess functional K-ATP channels. To repair this defect NES2Y cells were stably transfected with cDNAs encoding SUR1, and Kir6.2. Designated NISK9, the engineered Beta cells exhibited glucose responsive secretion of insulin in the physiologically relevant glucose concentration range (3-11 mM). They were also able to modulate cytosolic calcium concentration in response to KCl and tolbutamide.

Non-beta cells have also been engineered to secrete insulin. These include the mouse corticotrophic AtT20 cell line, which efficiently processes the transfected proinsulin to insulin. However, although these cells restored near normal glycaemia when implanted into streptozotocin diabetic mice, the co-secretion of ACTH rendered the mice resistant to insulin.{BR}Efficient expression of human insulin can be achieved following intramuscular injection of naked plasmid DNA in rats. The secreted insulin was biologically active as evidenced by significantly lower plasma glucose levels following DNA injection.