Glimpses into the molecular pathogenesis of Peyronie's disease

Peyronie's disease (PD) is a fibroproliferative disease of the penis. Since little is known about the molecular pathogenesis of PD, we compared the biochemical make-up of PD plaques with normal tunica albuginea to clarify pathological processes in the scarred tissue. Protein and mRNA levels were measured in plaques and in unaffected pieces of the tunica albuginea. We investigated the presence of myofibroblasts, the deposition of collagens, and some key elements of Wnt and YAP1 signaling at protein level. The expression of 45 genes, all related to collagen homeostasis and extracellular matrix proteins, was quantified. In plaques, more myofibroblasts were present, and we observed an activation of Wnt signaling and YAP1 signaling. Increased levels of the collagens types I and III confirm the fibrotic nature of plaques. The mRNA ratio of collagen types III, IV, and VI to type I was increased. The expression of lysyl hydroxylase 3 was higher, whereas a decreased expression level was seen for fibronectin and cathepsin K. The biochemical composition of plaques was different from unaffected tunica albuginea: the relative and absolute abundance of various extracellular matrix proteins were changed, as well as the quality of collagen and the level of the collagen-degrading enzyme cathepsin K.