An experimental gene therapy that uses a sexually transmitted virus could someday give pain relief without the use of drugs to millions of patients who suffer from bladder pain syndrome.
In a study published in the journal Human Gene Therapy, researchers at the University of Pittsburgh used gene therapy in rats to stimulate the production of enkephalin, an opioid-like compound naturally produced by the body. The gene was injected into the bladder wall and transported to nerves that deliver pain signals via a herpes simplex virus. The herpes virus was first rendered incapable of replication.
Researchers say the treated rats had significantly lower measures of pain compared to untreated animals when exposed to stimuli intended to induce bladder irritation.
“This is a very innovative application of Herpes Simplex Virus gene therapy in the treatment of a common and painful clinical problem that otherwise requires chronic use of narcotics,” says James M. Wilson, MD, PhD, Editor-in-Chief, and Director of the Gene Therapy Program, Department of Pathology and Laboratory Medicine, University of Pennsylvania Perelman School of Medicine, Philadelphia.
A similar gene therapy delivery system using the herpes simplex virus has been used in clinical studies on cancer patients and provided substantial pain relief with no side effects.
Researchers say gene therapy is also promising for patients who suffer from bladder pain syndrome/interstitial cystitis (BPS/IC) because the disorder is difficult to treat with current therapies such as opioid painkillers.
“Opioid drugs have been used to control pain in these patients; however, side effects are common,” wrote lead author Hitoshi Yokoyama, MD, from the University of Pittsburgh School Of Medicine and Shinshu University School of Medicine (Matsumoto, Japan) .
“The targeted therapy using the HSV (herpes simplex virus) vector encoding hPPE, which can suppress not only bladder overactivity and pain behavior but also urine cytokine expression, could be an attractive therapeutic option without side effects, instead of current treatments including systemic opioid application.”
The most common symptoms of BPS/IC are bladder pain, a frequent need to urinate and painful sexual intercourse. The cause is unknown. Neuromodulation, transcutaneous electrical nerve stimulation (TENS) and acupuncture have been used with some success in relieving pain from BPS/IC.