The mechanism of action of phosphodiesterase type 5 inhibitors in preventing myofibroblast transformation in in vitro models of peyronie's disease

Abstract Objectives Peyronie’s disease (PD) is a fibrotic disorder of the penis, where a fibrous plaque forms in the tunica albuginea (TA), leading to pain, penile deformity, and erectile dysfunction. There is currently no effective medical treatment available. The transformation of fibroblasts into myofibroblasts is a key event in the pathophysiology of PD and previous work has shown that phosphodiesterase type 5 inhibitors (PDE5i) can prevent this transformation in vitro and prevent PD development in vivo. This study aims to identify the molecular mechanism of the anti-myofibroblast action of PDE5i. Methods Primary fibroblasts were isolated from the TA of patients undergoing corrective surgery for PD. Myofibroblast transformation was determined utilizing an In-cell ELISA assay by quantifying the expression of α-smooth muscle actin in response to 10 ng/mL TGF-β1. Concentration response curves (CRCs) were generated to confirm the anti-fibrotic action of PDE5i, and in the presence and absence of pharmacological inhibitors to identify molecular components involved in the mechanism of action of PDE5i. Three biological and three technical replicates were generated, and statistical significance determined using unpaired Students’ t-test. Results TGF-β1 receptor inhibitor SB-505124 and PDE5i vardenafil abrogated TGF-β1-induced myofibroblast transformation with an IC50 of 0.29 ± 0.07 μM and 10.15 ± 3.53 μM, respectively. At 1 μM, protein kinase G inhibitor KT5823 did not prevent the antifibrotic action of vardenafil. The cAMP analog 8-Br-cAMP and PDE3i cilostamide abrogated TGF-β1-induced myofibroblast transformation with an IC50 of 6.88 ± 14.29 μM, and 14.05 ± 1.63 μM, respectively. In the presence of 1 μM KT5720, a protein kinase A inhibitor, the antifibrotic effect of vardenafil was significantly reduced. Conclusions These results suggest that PDE5i prevent TGF-β1-induced transformation of myofibroblasts not through PKG, but through the PDE3/cAMP/PKA pathway. Although such an interaction has been shown in other fibroblasts, this is the first demonstration in PD fibroblasts. Conflicts of Interest No known conflicts of interest.