The activated complement pathway in the fibrous process of benign prostatic hyperplasia

Background: To elucidate the changes in activated complement pathway in the fibrous process of benign prostatic hyperplasia (BPH), we analyzed the correlation between complement component expression and histological types of fibrosis using human BPH tissue. Methods: Fifty-six histological BPH patients who underwent prostate needle biopsy at our institution (mean age 68.6 +/- 6.5 years), divided into two histological groups, fibromuscular and fibrous, were compared. Inflammatory cell infiltration in BPH tissue was evaluated by immunohistochemical staining using CD45, with complement expression analysis performed using C3, factor B, and C5b-9 antibody, and the occupancy ratio of the stained region was calculated. Further, correlation between the histological types of fibrous components in BPH tissue and lower urinary tract symptoms questionnaires was analyzed. Results: Twenty-seven (48.2%) and 29 (51.8%) cases were classified in the fibromuscular and fibrous groups, respectively. The proportion of CD45-positive cells in BPH tissue was significantly higher in the fibromuscular group. In complement component analysis, factor B did not significantly differ between groups, while C3 (fibromuscular group; 10.7 +/- 8.2%, fibrous group; 16.4 +/- 12.7%) and C5b-9 (fibromuscular group; 15.9 +/- 6.2%, fibrous group; 17.6 +/- 9.2%) were significantly higher in the fibrous group (p = 0.04, p = 0.04, respectively). International Prostate Symptom Score Q5 subscore, indicating slow stream, was significantly higher in the fibrous group (p = 0.04). Conclusions: In fibrous BPH with abundant fibrosis, the late complement pathway in addition to alternative pathway was activated compared to fibromuscular BPH. These results suggested that the alternative and late complement pathways were involved in the histological fibrous process of BPH.