Insulin Gene Therapy using Vascular Smooth Muscle Cells in Diabetic Rats

Oh, Tae Geun; Lee, Mi Ja; Kim, Young Ku; Kim, Seung Tak

Abstract

BACKGROUND: Type 1 diabetes mellitus is caused by a lack of insulin. The purpose of this study was to test whether blood glucose control in severe diabetic animals can be achieved by transplanting of rat vascular smooth muscle cells which are transduced with the insulin gene using a retroviral vector system.
METHODS
After cloning the recombinant retroviral plasmid including human mutated proinsulin cDNA which contains furin endopeptidase cleavage site, the resulting plasmid, LInABCSN, was transfected into the retroviral packaging cell line (PA317/LhInABCSN). The resulting retrovirus in the supernatant of PA317/ LhInABCSN infected the F344 rat vascular smooth muscle cell (SMC) and produced the SMC/LhInABCSN cells. After transplanting SMC/LInABCSN cells into the internal carotid artery of the rat, diabetes was induced by an intraperitoneal streptozotocin (STZ) injection (50 mg/kg) 2 week later. The blood glucose and insulin levels, percent weight change and the survival rates between the control group (SMC/LNFZ) and the treatment group (SMC/LInABCSN) were compared.
RESULTS
The insulin concentrations in the supernatant of the SMC/LhInABCSN mice were 160.2 IU/mL in 24 hours, 243.6 IU/mL in 48 hours and 350.2 IU/mL in 72 hours, but the proinsulin concentrations in 24, 48 and 72 hours were all lower than 1 pmol/L. After 1 day and 3 days of the STZ injection, there were no differences in glucose concentrations between treatment group (n=10) and control group (n=10). There were no statistical differences in the percent weight change between the control and treatment group but the treated rats showed bad a lower weight loss than control rats. After 3 days of the STZ injection, serum insulin concentration of treatment group showed slightly higher levels than the control group (2.7+/-.5 IU/mL vs. 1.6+/-.1 IU/mL, p=0.077). The survival showed a significant increase in treatment group (median survival: 29 days, 9-104 days) compared to the control group (median survival: 6 days, 3-49 days, p < 0.05).
CONCLUSION
Although this study did not show a normal glucose concentration in treated rats, it did show significantly higher survival compared to control rats. It is believed that gene therapy using rat vascular smooth muscle cells which transduced the insulin gene may be a new insulin delivery method.