Korean J Androl.  2012 Apr;30(1):23-30. 10.5534/kja.2012.30.1.23.

Transforming Growth Factor-beta Type I Receptor Inhibitor Induces Functional and Morphologic Recovery in a Rat Model of Erectile Dysfunction and Cavernous Fibrosis

• Ryu JK
• Oh SM
• Jin HR
• Song KM
• Kwon MH
• Kim DK
• Suh JK

• KMID: 2298805
• DOI: http://doi.org/10.5534/kja.2012.30.1.23

Abstract

PURPOSE
To examine the effectiveness of small-molecule inhibitor of transforming growth factor-beta (TGF-beta) type I receptor, an activin receptor-like kinase 5 (ALK5), on erectile dysfunction (ED) in a rat model of cavernous fibrosis, in which fibrosis was induced by intracavernous injection of adenovirus expressing TGF-beta1 (Ad-TGF-beta1).
MATERIALS AND METHODS
Four-month-old Sprague-Dawley rats were divided into four groups (n=10 per group): age-matched controls without treatment, age-matched controls receiving intracavernous injection of LacZ adenovirus, and cavernous fibrosis rats receiving an intracavernous injection of saline or ALK5 inhibitor (5 mg/kg). ALK5 inhibitor or saline was administered on day 5 after injection of Ad-TGF-beta1. On day 30, erectile function was assessed by electrical stimulation of the cavernous nerve and the penis was then harvested for histologic studies (n=6 per group) and for the measurement of the hydroxyproline level (n=4 per group).
RESULTS
Ad-TGF-beta1-induced cavernous fibrosis rats treated with saline showed a significant decrease in cavernous smooth muscle and endothelial content, and an increase in collagen deposition, which resulted in profound deterioration of all erectile function parameters, such as the ratios of maximal intracavernous pressure (ICP), total ICP, and slope to mean arterial pressure. ALK5 inhibitor significantly restored erectile function in a rat model of cavernous fibrosis by increasing cavernous smooth muscle and endothelial content, and by blocking cavernous fibrosis.
CONCLUSIONS
The results suggest that inhibition of the TGF-beta pathway is a promising therapeutic strategy for the treatment of ED related to cavernous fibrosis from various causes.

Keyword

Erectile dysfunction; Fibrosis; Transforming growth factor beta; TGF-beta type I receptor

MeSH Terms

Activin Receptors
Adenoviridae
Animals
Arterial Pressure
Caves
Collagen
Electric Stimulation
Erectile Dysfunction
Fibrosis
Hydroxyproline
Male
Muscle, Smooth
Penis
Protein-Serine-Threonine Kinases
Rats
Rats, Sprague-Dawley
Receptors, Transforming Growth Factor beta
Transforming Growth Factor beta
Transforming Growth Factor beta1
Activin Receptors
Collagen
Hydroxyproline
Protein-Serine-Threonine Kinases
Receptors, Transforming Growth Factor beta
Transforming Growth Factor beta
Transforming Growth Factor beta1

Figure

• 

  Fig. 1. Activin receptor-like kinase 5 (ALK5) inhibitor restores intracavernous pressure (ICP) elicited by electrical stimulation of the cavernous nerve in an adenovirus expressing TGF-β1 (Ad-TGF-β1)-induced cavernous fibrosis model. (A) Representative ICP responses for the untreated control, LacZ adenovirus (Ad-LacZ)-treated control, and cavernous fibrosis model receiving intracavernous injection of saline or ALK5 inhibitor. (B∼D) Ratios of the mean maximal ICP, total ICP (area under the curve), and slope to mean arterial pressure (MAP) were calculated for each group. Each bar depicts the mean±standard deviations from n=6 animals per group. ∗p＜0.01 compared with other groups. ALK5I, small-molecule inhibitor of activin-like receptor kinase 5.

• 

  Fig. 2. Activin receptor-like kinase 5 (ALK5) inhibitor promotes the regression of cavernous fibrosis and reduces collagen content in an adenovirus expressing TGF-β1 (Ad-TGF-β1)-induced cavernous fibrosis model. (A) Masson's trichrome staining of cavernous tissue from the untreated control, LacZ adenovirus (Ad-LacZ)-treated control, and cavernous fibrosis model receiving intracavernous injection of saline or ALK5 inhibitor. Magnification, 100×. (B) Cavernous hydroxyproline content in each group. Each bar depicts the mean±standard deviations from n=4 animals per group. ∗p＜0.05 compared with other groups. ALK5I, small-molecule inhibitor of activin-like receptor kinase 5.

• 

  Fig. 3. Activin receptor-like kinase 5 (ALK5) inhibitor restores cavernous smooth muscle content in an adenovirus expressing TGF-β1 (Ad-TGF-β1)-induced cavernous fibrosis model. (A) Anti-smooth muscle α-actin staining of cavernous tissue from the untreated control, LacZ adenovirus (Ad-LacZ)-treated control, and cavernous fibrosis model receiving intracavernous injection of saline or ALK5 inhibitor. Magnification, 100×. (B) Quantitative analysis of smooth muscle cell content in cavernous tissue was performed using an image analyzer. Each bar depicts the mean±standard deviations from n=6 animals per group. ∗p＜0.01 compared with other groups. ALK5I, small-molecule inhibitor of activin-like receptor kinase 5.

• 

  Fig. 4. Activin receptor-like kinase 5 (ALK5) inhibitor restores cavernous endothelial content in an adenovirus expressing TGF-β1 (Ad-TGF-β1)- induced cavernous fibrosis model. (A) Anti-factor VIII staining of cavernous tissue from the untreated control, LacZ adenovirus (Ad-LacZ)-treated control, and cavernous fibrosis model receiving intracavernous injection of saline or ALK5 inhibitor. Each figure was merged with factor VIII staining and phase image. Magnification, 200×. (B) Quantitative analysis of endothelial cell content in cavernous tissue was performed by using an image analyzer. Each bar depicts the mean±standard deviations from n=6 animals per group. ∗p＜0.01 compared with other groups. ALK5I, small-molecule inhibitor of activin-like receptor kinase 5.

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