Effects of long‐term vardenafil treatment on the development of fibrotic plaques in a rat model of Peyronie's disease

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Abstract
To determine whether the phosphodiesterase-5 (PDE5) inhibitor, vardenafil, given orally and in different regimens, has a similar effect to that of the PDE5 inhibitor sildenafil, which prevented the development of a Peyronie's disease (PD)-like plaque formation induced by injecting transforming growth factor beta1 (TGF-beta1) into the tunica albuginea of the rat. Vardenafil was given to male rats (eight per group) either in the drinking water or as an oral instillation once daily, at approximately 1 and approximately 3 mg/kg/day for 45 days after one injection with TGF-beta1 into the tunica albuginea, as an 'early preventive' treatment for TGF-beta1-induced formation of a PD-like plaque. Other groups received the two doses of vardenafil only in the drinking water, starting with a well-formed plaque, for 42 days ('late, therapeutic' administration). Sections of penile tissue were stained histochemically or immunohistochemically, followed by quantitative image analysis for collagen/smooth muscle and collagen III/I ratios, myofibroblast content (alpha-smooth muscle actin), TGF-beta1 expression, and apoptotic index. Preventative treatment with vardenafil at the higher dose (both continuous and once-daily treatments) reduced the collagen/smooth muscle and collagen III/I ratios, and the numbers of myofibroblasts and TGF-beta1-positive cells, and selectively increased the apoptotic index in the PD-like plaque. The lower dose was less effective, When vardenafil was given continuously in the drinking water for 41 days after the PD-like plaque was formed, there was only a partial reduction of the plaque. Long-term oral treatment with vardenafil slows and reverses the early stages of an experimental PD-like plaque in the rat, and might ameliorate a more advanced plaque.