Thermotolerance of human myometrium: implications for minimally invasive uterine therapies

Endometrial ablation has gained significant clinical acceptance over the last decade as a minimally invasive treatment for abnormal uterine bleeding. To improve upon current thermal injury modeling, it is important to better characterize the myometrium's thermotolerance. The extent of myometrial thermal injury was determined across a spectrum of thermal histories/doses (time-temperature combinations). Fresh extirpated human myometrium was obtained from 13 subjects who underwent a previous scheduled benign hysterectomy. Within two hours of hysterectomy, the unfixed myometrium was treated in a stabilized saline bath with temperatures ranging from 45-70 °C and time intervals from 30- 150 seconds. The time-temperature combinations were selected to simulate treatment times under 2.5 minutes. A total of six such thermal matrices, each comprised of 45 time-temperature combinations, were prepared for evaluation. The treated myometrium was cryosectioned for nitro blue tetrazolium (NBT) staining to assess for thermal respiratory enzyme inactivation. Image analysis was subsequently used to quantitatively assess the stained myometrium's capacity to metabolize the tetrazolium at each time-temperature combination. This colorimetric data was then used as marker of cellular viability and determine survival parameters with implications for developing minimally invasive uterine therapies.