Gene therapy and erectile dysfunction: the current status

Effects of Icariside II on corpus cavernosum and major pelvic ganglion neuropathy in streptozotocin-induced diabetic rats

Diabetic erectile dysfunction is associated with penile dorsal nerve bundle neuropathy in the corpus cavernosum and the mechanism is not well understood. We investigated the neuropathy changes in the corpus cavernosum of rats with streptozotocin-induced diabetes and the effects of Icariside II (ICA II) on improving neuropathy. Thirty-six 8-week-old Sprague-Dawley rats were randomly distributed into normal control group, diabetic group and ICA-II treated group. Diabetes was induced by a one-time intraperitoneal injection of streptozotocin (60 mg/kg). Three days later, the diabetic rats were randomly divided into 2 groups including a saline treated placebo group and an ICA II-treated group (5 mg/kg/day, by intragastric administration daily). Twelve weeks later, erectile function was measured by cavernous nerve electrostimulation with real time intracorporal pressure assessment. The penis was harvested for the histological examination (immunofluorescence and immunohistochemical staining) and transmission electron microscopy detecting. Diabetic animals exhibited a decreased density of dorsal nerve bundle in penis. The neurofilament of the dorsal nerve bundle was fragmented in the diabetic rats. There was a decreased expression of nNOS and NGF in the diabetic group. The ICA II group had higher density of dorsal nerve bundle, higher expression of NGF and nNOS in the penis. The pathological change of major pelvic nerve ganglion (including the microstructure by transmission electron microscope and the neurite outgrowth length of major pelvic nerve ganglion tissue cultured in vitro) was greatly attenuated in the ICA II-treated group (p < 0.01). ICA II treatment attenuates the diabetes-related impairment of corpus cavernosum and major pelvic ganglion neuropathy in rats with Streptozotocin-Induced Diabetes.

Gene therapy as future treatment of erectile dysfunction

IMPORTANCE OF THE FIELD

Erectile dysfunction (ED) is a major men's health problem. Although the high success rate of treating ED by phosphodiesterase 5 (PDE5) inhibitors has been reported, there are a significant number of ED patients who do not respond to currently available treatment modalities.

AREAS COVERED IN THIS REVIEW

To elucidate the current status of gene therapy applications for ED, gene therapy approaches for ED treatment are reviewed.

WHAT THE READER WILL GAIN

Gene therapy strategies that can enhance nitric oxide (NO) production or NO-mediated signaling pathways, growth factor-mediated nerve regeneration or K(+) channel activity in the smooth muscle could be promising approaches for the treatment of ED. Although the majority of gene therapy studies are still in the preclinical phase, the first clinical trial using non-viral gene transfer of Ca(2+)-activated, large-conductance K(+) channels into the corpus cavernosum of ED patients showed positive results.

TAKE HOME MESSAGE

Gene therapy represents an exciting future treatment option for ED, especially for people with severe ED unresponsive to current first-line therapies such as PDE5 inhibitors although the long-term safety of both viral and non-viral gene therapies should be established.

Gene therapy for male erectile dysfunction

The potential clinical advantages of a gene transfer therapy-based approach to treatment of genitourinary smooth muscle-based disorders are several: potential single therapy for restoration of normal bladder or erectile function; eliminating the need for daily medication; use in combination with other therapies to reduce dose requirements and side effects; and development of mechanism-based, patient-specific treatment approaches. With the safe administration of hMax-K to men with erectile dysfunction in the first human phase 1 trial and the initiation of the phase 1 trial of hMaxi-K for patients who have detrusor overactivity, we have entered an exciting new era in the development of safe enduring therapies for genitourinary disorders.