Objectives: Different thermotherapeutic modalities such as transurethral microwave therapy or transurethral needle ablation have been developed to provide effective alternatives to surgical management of benign prostate hyperplasia (BPH). The mechanisms of thermotherapy, however, are not completely understood. We developed a model to investigate the effects of heat application on stromal cell viability and contractility. Methods: Cells isolated from prostatectomy and cystoprostatectomy specimens were cultured in a selective medium. Temperatures ranging from 37 to 50 degrees C were applied for 1 h. Cell contraction was visualized by means of a cell culture microscope equipped with a time-lapse video system. For quantitative analysis, the percentage of contracting cells was evaluated; 10 mu M of phenylepherine were applied for adrenergic stimulation of the eel Is. Results: On immunohistochemistry and phase-contrast microscopy, these cells were identified as prostatic myofibroblasts. Incubation at 50 degrees C for 1 h in vitro induced immediate death of all cells, whereas at 45 degrees C a II cells survived. At 37 degrees C 55% of the cells were seen to contract after addition of phenylephrine. Immediately after incubation at 45 degrees C contraction rate decreased to 29%, but returned to 46% 1 day later. Conclusions: With this model, it is possible to study the mechanisms of thermotherapy in vitro. The results suggest that the effects of thermotherapy are due to the induction of cell death rather than to reduced stromal cell contractility. Furthermore, the data show that treatment is probably only successful if temperatures in excess of 50 degrees C are maintained. Copyright (C) 2000 S. Karger AG, Basel.