O'Hara M D, Pollard M D, Xiong Q B, Leeper D B
Department of Radiation Oncology & Nuclear Medicine, Thomas Jefferson University Hospital, Philadelphia, Pennsylvania.
Exp Hematol. 1991 Oct;19(9):878-81.
The purpose of this investigation was to study the response of the hematopoietic stem cell, spleen colony-forming unit (CFU-S), to hyperthermia. We have shown that CFU-S can acquire a transient resistance to further heating (thermotolerance). Hyperthermia was applied in vitro to nucleated bone marrow cells in McCoy's 5A medium plus 15% fetal bovine serum. Day-10 CFU-S (CFU-S10) were detected as spleen colonies after inoculation into the tail vein of irradiated (450 cGy plus 4 h plus 400 cGy) Balb/c male mice. Thermotolerance development was detected with a "step-up" heating protocol consisting of heating for various times at 42 degrees C followed immediately with a thermal challenge of 26 min at 44 degrees C. The inverse of the slopes of the heat "dose-response" curves (D degree +/- SE) of the normotolerant CFU-S heated to 42 degrees, 42.5 degrees, 43 degrees, 43.5 degrees, and 44 degrees C were 108 +/- 13, 54 +/- 8, 25 +/- 1, 17 +/- 2, and 12 +/- 5 min, respectively. A plot of the slopes of the heat "dose-response" relationships versus the inverse of the absolute temperature (Arrhenius plot) showed an inflection at approximately 43 degrees C. Analysis of the regression coefficient above and below the inflection point (Arrhenius analysis) yielded inactivation enthalpies (+/- SE) of 598 +/- 130 kJ/mol (143 +/- 31 kcal/mol) and 1205 +/- 171 kJ/mol (288 +/- 41 kcal/mol), respectively. The difference in inactivation enthalpy indicates a change in mechanism in the thermal inactivation of CFU-S above and below 43 degrees C, possibly due to thermotolerance development during exposure to temperatures less than 43 degrees C. Prolonged incubation at 42 degrees C for up to 180 min with a step-up to 44 degrees C for 26 min showed that CFU-S survival increased rapidly from 0.25 (26 min at 44 degrees C) to 0.52 within 10 min. The thermotolerance ratio (TTR, ratio of the surviving fraction of the maximum thermotolerant cells to that of the normotolerant cells) was 2.1. Both the higher inactivation enthalpy for exposures less than 43 degrees C and the rapid increase in survival during the "step-up" heating experiments at 42 degrees C demonstrate that CFU-S can develop thermotolerance during prolonged hyperthermia. These results suggest that thermotolerance can influence the thermal response of pluripotent bone marrow stem cells heated during whole-body or local-regional clinical hyperthermia protocols.
本研究的目的是探讨造血干细胞——脾集落形成单位（CFU-S）对热疗的反应。我们已经证明，CFU-S能够获得对进一步加热的短暂抗性（热耐受）。将热疗应用于添加15%胎牛血清的 McCoy's 5A 培养基中的有核骨髓细胞。将第10天的 CFU-S（CFU-S10）接种到经辐照（450 cGy 加 4 小时加 400 cGy）的 Balb/c 雄性小鼠尾静脉后，检测其作为脾集落的情况。采用“逐步升温”加热方案检测热耐受的形成，该方案包括在 42℃加热不同时间，随后立即在 44℃进行 26 分钟的热刺激。将正常耐受的 CFU-S 加热至 42℃、42.5℃、43℃、43.5℃和 44℃时，热“剂量-反应”曲线（D°±SE）斜率的倒数分别为 108±13、54±8、25±1、17±2 和 12±5 分钟。热“剂量-反应”关系的斜率与绝对温度倒数的关系图（阿累尼乌斯图）显示，在约 43℃处有一个拐点。对拐点上下的回归系数进行分析（阿累尼乌斯分析），得到失活焓（±SE）分别为 598±130 kJ/mol（143±31 kcal/mol）和 1205±171 kJ/mol（288±41 kcal/mol）。失活焓的差异表明，在 43℃上下，CFU-S 热失活的机制发生了变化，这可能是由于在暴露于低于 43℃的温度期间热耐受的形成。在 42℃下长时间孵育长达 180 分钟，然后逐步升温至 44℃持续 26 分钟，结果显示 CFU-S 的存活率在 10 分钟内迅速从 0.25（44℃下 26 分钟）增加到 0.52。热耐受比（TTR，最大热耐受细胞存活分数与正常耐受细胞存活分数之比）为 2.1。低于 43℃暴露时较高的失活焓以及在 42℃的“逐步升温”加热实验中存活率的快速增加都表明，CFU-S 在长时间热疗过程中能够形成热耐受。这些结果表明，热耐受可能会影响在全身或局部区域临床热疗方案中加热的多能骨髓干细胞的热反应。
