Changes in Extracellular Matrix Components of Bladder Detrusor in Relation to Bladder Hypertrophy and Compliance in Patients with Benign Prostatic Hyperplasia

Abstract

The bladder hypertrophy caused by infravesical obstruction due to benign prostatic hyperplasia (BPH) often results in bladder dysfunction. Here we attempted to study morphometrically the histological changes in bladder detrusor with reference to extracellular matrix and to find the correlation of those changes with bladder hypertrophy. Ultrasound estimated bladder weight (UEBW) and urodynamic parameters were evaluated in 34 BPH patients (71.4±7.9 years) before surgery. Bladder wall samples were obtained at surgery and stained using Masson trichrome method and immunohistochemistry for collagen types I and III and fibronectin, followed by morphometric color image analysis system. UEBW, ratios of connective tissue−to−smooth muscle (c/m), collagen type III-immunoreactive area−to−collagen type I-immunoreactive area (collagen III/I) and fibronectin−immunoreactive area−to−non−immunoreactive area (f/n) ranged from 21.0 to 126.1g (47.9±25.4g), 12.9 to 53.3% (27.6±9.2%), 31.9 to 69.7% (46.5±8.0%) and 40.2 to 125.9% (59.8±15.9%), respectively. UEBW correlated with c/m (r=0.744, p<0.0001), collagen III/I (r=0.698, p<0.0001) and f/n (r=0.733, p<0.0001). Among urodynamic parameters, bladder compliance was the only one that correlated with c/m (r=0, 673, p<0.0001), collagen III/I (r=0.475, p<0.05) and f/n (r=0.590, p<0.001). These results suggest that an abnormal increase of connective tissue accompanied with increased levels of collagen type III and fibronectin could contribute to advanced bladder hypertrophy with a loss of elasticity of the bladder wall in patients with infravesical obstruction.