A Comparative Study of the Efficacy of Intralesional Verapamil Versus Normal Saline Injection in a Novel Peyronie Disease Animal Model: Assessment of Immunohistopathological Changes and Erectile Function Outcome

Purpose: While intralesional injections improve penile curvature and decrease plaque volume, the exact mechanism of action on Peyronie disease is unknown. We evaluated penile curvature, immunohistology and erectile function outcomes after intralesional injections of verapamil and normal saline in a previously described Peyronie disease animal model. Materials and Methods: Peyronie plaque was induced in 12 adult male rats using an established Peyronie disease animal model. At 4 weeks the rats were divided into group 1-5 with 0.1 mg/0.1 ml intralesional verapamil injected every second day for 2 weeks, group 2-5 with 0.1 ml intralesional normal saline injection and group 3-2 that served as controls. At weeks 6 and 8 penile pressure was measured and serial immunohistochemical staining of penile tissue sections was done. Results: Intralesional injection of verapamil and normal saline resulted in macroscopic and microscopic changes to penile curvature and Peyronie plaque size. Decreased collagen and elastin fibers were measured with a significant reduction in smooth muscle alpha-actin (p < 0.05). Changes were greater in group 1 than group 2 (p < 0.05). Intralesional verapamil injection was associated with greater recovery of electrostimulated penile pressure, a surrogate of erectile function, than in the saline and control groups. Conclusions: To our knowledge this novel study offers for the first time histological evidence of cellular changes and improvement in penile pressure studies in rats with Peyronie plaque after intralesional verapamil injection therapy in a Peyronie disease animal model.