Transurethral balloon laser thermotherapy induces long-lasting apoptosis of prostatic smooth muscle cells in human prostatic hyperplasia

Transurethral balloon laser thermotherapy (TUBAL-T) has been developed recently as a noninvasive treatment for benign prostatic hyperplasia (BPH), but the cellular events occurrmg after TUBAL-T were not yet fully understood. We examined prostate tissues by electron microscopy and the DNA nick end-labeling method at 2 and 4 weeks after a single TUBAL-T treatment in an attempt to elucidate the mechanism by which TUBAL-T progressively improves obstructive complications of patients with BPH. Condensation of chromatin at the nuclear margin was observed in prostatic smooth muscle cells (PSMCs) located in the area adjacent to periurethral coagulative necrosis. PSMCs with condensed chromatin were often accompanied by cytoplasmic vacuoles in perinuclear areas. Application of the nick end-labeling method at the light microscopic level revealed that most PSMC nuclei were positive for terminal TdT-mediated dUTP-dioxygenic nick end-labeling (TUNEL) staining. These results strongly suggested that long-standing apoptosis is induced in PSMCs by TUBAL-T. as well as massive coagulative necrosis of prostatic tissues. The role of apoptosis in PSMCs in the clinical improvement of outlet obstruction after TUBAL-T is discussed.