Preconditioning of adipose-derived stem cells by phosphodiesterase-5 inhibition enhances therapeutic efficacy against diabetes-induced erectile dysfunction.

BACKGROUND: Adipose-derived stem cells have been considered as a promising therapy for erectile dysfunction. However, the therapeutic efficacy of adipose-derived stem cell-based therapy requires improvement. OBJECTIVE: To determine whether the inhibition of phosphodiesterase type 5 in adipose-derived stem cells would improve stem cell therapy for rats with diabetes-induced erectile dysfunction. MATERIALS AND METHODS: A phosphodiesterase type 5 siRNA was incorporated into lentiviral vectors and transduced into adipose-derived stem cells. The mRNA and protein levels of phosphodiesterase type 5 were evaluated. Three days after transduction, the adipose-derived stem cell supernatant was collected to determinate the levels of insulin-like growth factor 1 and vascular endothelial growth factor. Streptozotocin-induced diabetic rat models were established and used for comparative analysis of 1- and 2-week treatment regimens with intracavernosal injection of adipose-derived stem cells or Lv-siPDE5-modified adipose-derived stem cells. RESULTS: Lv-siPDE5-ADSCs secreted more insulin-like growth factor 1 and vascular endothelial growth factor in supernatants than unmodified adipose-derived stem cells. Preconditioned Adipose-derived stem cells-treated diabetic rats showed consistently superior erectile function when compared with non-preconditioned adipose-derived stem cells after 2 weeks of treatment. Lv-siPDE5-ADSCs provided additional benefits in recovery of cavernous structures with rapid effects (1 week) when compared to plain adipose-derived stem cells. These features were associated with the significantly increased levels of insulin-like growth factor 1 and vascular endothelial growth factor in Lv-siPDE5-ADSC-treated diabetic rats. CONCLUSIONS: Adipose-derived stem cell therapy could serve as an alternate approach for diabetes-induced erectile dysfunction, albeit with a long onset period. In vitro preconditioning of adipose-derived stem cells could accelerate the functional and structural recovery in vivo, indicating that preconditioning by inhibition of phosphodiesterase type 5 may improve adipose-derived stem cells therapy following diabetes-induced erectile dysfunction.

S-allyl cysteine restores erectile function through inhibition of reactive oxygen species generation in diabetic rats.

Excessive production of reactive oxygen species (ROS) by an overactive nicotinamide adenine dinucleotide phosphate (NADPH) oxidase system in penile tissue is an important mechanism of erectile dysfunction (ED). S-allyl cysteine (SAC), a bioactive component derived from garlic, was recently reported to exert versatile antioxidant properties. We hypothesized that SAC would be able to resolve diabetes-related ED by reducing ROS generation, and designed this study to investigate this possibility as well as to determine the related underlying mechanisms. A streptozotocin-induced diabetes rat model was established and used for comparative analysis of 4-week treatment regimens with insulin or SAC. The ratio of maximal intracavernous pressure (ICP) to mean arterial blood pressure (MAP) was measured to determine erectile function. Differential levels of ROS, NADPH oxidase subunits, nitric oxide (NO)/cyclic guanosine monophosphate (cGMP) signalling pathway, and apoptosis were evaluated in cavernous tissues. Max ICP/MAP was found to be markedly decreased in untreated diabetic rats; SAC, but not insulin, treatment restored the ratio to baseline (in non-diabetic untreated controls). The corpus cavernosum of untreated diabetic rats showed increased p47(phox) and p67(phox) expression, ROS production and penile apoptotic index, and decreased phospho-endothelial nitric oxide synthase (phospho-eNOS, Ser1177) expression, cGMP concentration, B-cell lymphoma 2 (Bcl-2)/Bcl-2-associated X protein (Bax) ratio and smooth muscle cell number. SAC treatment normalized all the diabetes-induced effects, whereas insulin treatment partially normalized the alterations, but produced no effects on P47(phox) expression, penile ROS level, apoptotic index, Bcl-2/Bax ratio and smooth muscle cell number. Collectively, these data indicate that SAC treatment can restore erectile function in diabetic rats by preventing ROS formation through modulation of NADPH oxidase subunit expression. Furthermore, the poor efficacy of conventional insulin treatment for diabetic ED may be associated with an elevated level of ROS in penile tissue.