Hwa-Yean Shin

Role of Increased Penile Expression of Transforming Growth Factor-β1 and Activation of the Smad Signaling Pathway in Erectile Dysfunction in Streptozotocin-Induced Diabetic Rats

INTRODUCTION It has been suggested that transforming growth factor-beta1 (TGF-beta1) plays an important role in the pathogenesis of diabetes-induced erectile dysfunction. AIM To investigate the expression and activity of Smad transcriptional factors, the key molecules for the initiation of TGF-beta-mediated fibrosis, in the penis of streptozotocin (STZ)-induced diabetic rats. METHODS Fifty-two 8-week-old Sprague-Dawley rats were used and divided into control and diabetic groups. Diabetes was induced by an intravenous injection of STZ. MAIN OUTCOME MEASURES Eight weeks later, erectile function was measured by electrical stimulation of the cavernous nerve (N = 12 per group). The penis was harvested and stained with Masson trichrome or antibody to TGF-beta1, phospho-Smad2 (P-Smad2), smooth muscle alpha-actin, and factor VIII (N = 12 per group). Penis specimens from a separate group of animals were used for TGF-beta1 enzyme-linked immunosorbent assay (ELISA), P-Smad2/Smad2, phospho-Smad3 (P-Smad3)/Smad3, fibronectin, collagen I, and collagen IV western blot, or hydroxyproline determination. RESULTS Erectile function was significantly reduced in diabetic rats compared with that in controls. The expression of TGF-beta1, P-Smad2, and P-Smad3 protein evaluated by ELISA or western blot was higher in diabetic rats than in controls. Compared with that in control rats, P-Smad2 expression was higher mainly in smooth muscle cells and fibroblasts of diabetic rats, whereas no significant differences were noted in endothelial cells or in the dorsal nerve bundle. Cavernous smooth muscle and endothelial cell contents were lower in diabetic rats than in controls. Cavernous fibronectin, collagen IV, and hydroxyproline content was significantly higher in diabetic rats than in controls. CONCLUSION Upregulation of TGF-beta1 and activation of the Smad signaling pathway in the penis of diabetic rats might play important roles in diabetes-induced structural changes and deterioration of erectile function.

Downregulation of angiogenic factors and their downstream target molecules affects the deterioration of erectile function in a rat model of hypercholesterolemia.

OBJECTIVES To evaluate how the expression of angiogenic factors and their downstream target molecules, which are potentially involved in penile homeostasis, is related to erectile dysfunction in a rat model of hypercholesterolemia. METHODS Fifty-six 2-month-old male Sprague-Dawley rats were included in this study. The control animals (n = 28) were fed a normal diet, and the experimental animals (n = 28) were fed a diet containing 4% cholesterol and 1% cholic acid for 3 months. Erectile function was evaluated by cavernous nerve electrical stimulation, and cavernous tissue was harvested for histologic examination (n = 12, respectively). Cavernous tissue specimens from the remaining rats were used for reverse transcriptase-polymerase chain reaction (RT-PCR), Western blot, or cyclic guanosine monophosphate (cGMP) measurement. RESULTS The ratio of maximal intracavernous pressure to mean arterial pressure was significantly lower in the hypercholesterolemic rats than in the controls (P <0.01). Analysis by RT-PCR and Western blot showed significantly lower gene expression of vascular endothelial growth factor (VEGF), angiopoietin-1, and angiopoietin-2 and significantly lower protein expression of VEGF, angiopoietin-1, angiopoietin-2, the ratio of phospho-Akt to Akt, and phospho-endothelial nitric oxide synthase (eNOS) to eNOS in hypercholesterolemic rats than in controls. Cavernous tissue cGMP concentrations and endothelial area were also significantly lower in hypercholesterolemic rats than in controls (P <0.01). CONCLUSIONS Downregulation of the expression of the angiogenic factors and their downstream signal molecules, and decreased endothelial content in the corpus cavernosum of hypercholesterolemic rats might play important roles in the deterioration of erectile function.

IN-1130, a Novel Transforming Growth Factor-β Type I Receptor Kinase (Activin Receptor-like Kinase 5) Inhibitor, Promotes Regression of Fibrotic Plaque and Corrects Penile Curvature in a Rat Model of Peyronie's Disease

INTRODUCTION Transforming growth factor-beta1 (TGF-beta1) has been known to play a crucial role in the pathogenesis of Peyronies disease (PD). AIM The aim of this paper was to investigate the therapeutic effect of IN-1130, a novel small molecule inhibitor of activin receptor-like kinase (ALK)5, a type I receptor of TGF-beta, in an animal model of PD. METHODS PD was induced in rats through repeated injections of adenovirus expressing TGF-beta1 (days 0, 3, and 6; 1 x 10(10) particles/0.1 mL, respectively) into the tunica albuginea. The rats were divided into five groups (N = 10 per group): group 1, age-matched controls without treatment; group 2, age-matched controls receiving repeated injections of IN-1130 (days 30 and 37; 5 mg/kg in 0.1 mL saline, respectively); group 3, PD rats without treatment; group 4, PD rats receiving repeated injections of saline (days 30 and 37; 0.1 mL, respectively); group 5, PD rats receiving repeated injections of IN-1130 (days 30 and 37; 5 mg/kg in 0.1 mL saline, respectively) into the lesion. MAIN OUTCOME MEASURES Penile curvature was evaluated by use of an artificial erection test at day 45, and the penis was then harvested for histologic examination. Collagen in the plaque was quantitatively assessed by hydroxyproline determination. RESULTS IN-1130 induced significant regression of fibrotic plaque through reduced infiltration of inflammatory cells, reduced transnuclear expression of phospho-Smad2/phospho-Smad3, reduced hydroxyproline content, and reduced cartilage content and restoration of elastin fibers in the fibrotic plaque of PD rats, which was accompanied by the correction of penile curvature. CONCLUSION Antagonizing TGF-beta signaling through the use of ALK5 inhibitors may represent an exciting new therapeutic strategy for the future treatment of PD.

Water-soluble lipopolymer as a gene carrier to corpus cavernosum

Adenovirus or naked plasmid DNA (pDNA) has been used to deliver the therapeutic gene into corpus cavernosum. However, the potential risks of viral vector and inefficiency of naked pDNA have limited their clinical application. In this study, water-soluble lipopolymer (WSLP) was evaluated as a gene carrier to corpus cavernosum. The WSLP/pDNA complex was transfected to smooth muscle cells in vitro. WSLP had high transfection efficiency, which was comparable to poly(ethylenimine) (PEI). In addition, WSLP had much less cytotoxicity than PEI, suggesting that WSLP is a safer carrier than PEI. To evaluate the transfection efficiency to corpus cavernosum, the WSLP/pDNA complex was injected into the rat corpus cavernosum. As a result, the WSLP/pDNA complex showed higher transfection efficiency than naked pDNA. In addition, the gene expression was dependent upon the dose of the complex. The results suggest that WSLP may be useful for gene therapy of erectile dysfunction.

Designed angiopoietin-1 variant, COMP-angiopoietin-1, rescues erectile function through healthy cavernous angiogenesis in a hypercholesterolemic mouse

Despite the advent of oral phosphodiesterase-5 inhibitors, curative treatment for erectile dysfunction (ED) remains unavailable. Recently, the link between ED and cardiovascular disease was unveiled and the main etiology of ED was found to be vasculogenic. Therefore, neovascularization is a promising strategy for curing ED. Angiopoietin-1 (Ang1) is an angiogenic growth factor that promotes the generation of stable and functional vasculature. Here, we demonstrate that local delivery of the soluble, stable, and potent Ang1 variant, COMP-Ang1 gene or protein, into the penises of hypercholesterolemic mice increases cavernous angiogenesis, eNOS phosphorylation, and cGMP expression, resulting in full recovery of erectile function and cavernous blood flow up to 8 weeks after treatment. COMP-Ang1-induced promotion of cavernous angiogenesis and erectile function was abolished in Nos3-/- mice and in the presence of the NOS inhibitor, L-NAME. COMP-Ang1 also restored the integrity of endothelial cell-cell junction by down-regulating the expression of histone deacetylase 2 in the penis of hypercholesterolemic mice and in primary cultured mouse cavernous endothelial cells. These findings constitute a new paradigm toward curative treatment of both cavernous angiopathy and ED.