Gene therapy using replication-defective herpes simplex virus vectors expressing nerve growth factor in a rat model of diabetic cystopathy

Diabetic cystopathy is one of the common complications of diabetes and current therapy is limited. In the present study, the effects of gene therapy, using replication-defective herpes simplex virus type 1 (HSV-1) vectors to deliver and express the nerve growth factor (NGF) gene (HSV-NGF) on tissue NGF levels and bladder function, were evaluated in streptozotocin (STZ)induced diabetic rats. Diabetic rats exhibited a significant decrease in NGF levels in the bladder and lumbosacral dorsal root ganglia (DRG) detected by enzyme-linked immunosorbent assay and displayed marked bladder dysfunction 12 weeks after STZ injection. In contrast, rats with bladder wall injection of the NGF expression vector 8 weeks after STZ treatment exhibited a significant increase of NGF levels in the bladder and L6 DRG 4 weeks after HSV-NGF injection. Along with the restoration of tissue NGF expression, in metabolic cage studies and cystometry, HSV-NGF-injected rats also showed significantly reduced bladder capacity and postvoid residual volume than diabetic rats injected with the control vector (HSV-lacZ), indicating that voiding function was improved after HSV vector-mediated NGF gene delivery. Thus, HSV vector-mediated NGF gene therapy may prove useful to restore decreased NGF expression in the bladder and bladder afferent pathways, thereby improving hypoactive bladder function in diabetes.