Higher expression of phosphodiesterase type 5 in the anterior fibromuscular stroma of the human prostate

To examine phosphodiesterase type 5 (PDE5) expression in the anterior fibromuscular stroma (AFMS) of the prostate. Although PDE5 expression was identified in the human prostate, differences in PDE5 expression in intra-prostatic regions are unknown. The AFMS in the prostate has peculiar innervations that could contribute to voiding function. Here, we examined regional differences in PDE5 expression in the prostate with special reference to the AFMS. A total 18 human prostate and bladder specimens were obtained. Tissue specimens were processed by hematoxylin–eosin (H&E) staining and immunohistochemistry for PDE5. Immunoreactivity with PDE5 was evaluated using computer-assisted image analysis in the following regions: the AFMS, bladder neck, stromal hyperplasia in the transition zone, glandular hyperplasia in the transition zone (TZ gland), and the peripheral zone (PZ). The correlation between PDE5 expression in the AFMS and clinical data was analysed. Image analysis revealed that the median ratio of the PDE5-immunoreactive area to smooth muscle area by H&E staining was 74.7% in the AFMS. There was significantly higher PDE5 expression in the AFMS than in the TZ gland (p = 0.034) and PZ (p = 0.002). PDE5 expression in the AFMS was not significantly correlated with age, prostate volume, transition zone volume, or transition zone index. However, older men had a tendency to have higher PDE5 expression in the AFMS. We found higher PDE5 expression in the AFMS compared with other prostatic regions, which suggested that the AFMS is a target region of PDE5 inhibitors in the prostate.