Trott K R, Shirazi A, Heasman F
Department of Radiation Biology, St. Bartholomew's Hospital, London, UK.
Radiother Oncol. 1999 Mar;50(3):261-6. doi: 10.1016/s0167-8140(98)00136-4.
The timing of acceleration of repopulation in the epidermis during daily irradiation is related to the development of skin erythema and epidermal hypoplasia. Therefore, the relationship between impairment of the epidermal barrier function, the dermal inflammatory response and epidermal hypoplasia with the acceleration of repopulation was investigated. MATERIALS AND PURPOSE: Skin fields of approximately 1 cm2 on the thighs of TUC mice were given five daily fractions of 3 Gy in each week followed by top-up doses at the end of the first, the second, or the third week to determine residual epidermal tolerance and to calculate repopulation rates in weeks 1, 2, or 3. Systemic modulation of repopulation was attempted by daily indomethacine during fractionated irradiation whereas tape stripping or UV-B exposure before the start of fractionated irradiation attempted local modulation. In parallel experiments, the water permeability coefficient of the epidermis was determined ex vivo by studying transepidermal transport of tritiated water.
Without modulation, no repopulation was found in the first week of daily fractionation but repopulation compensated 30% of the dose given in week two and 70% of the dose given in week three. Only tape stripping before the start of fractionated irradiation accelerated repopulation in week one. UV-B had no effect on repopulation although it stimulated proliferation as much as tape stripping. Indomethacin did not suppress acceleration of repopulation. A significant increase in transepidermal water loss was found but only after repopulation had already accelerated.
Acceleration of repopulation in mouse epidermis during daily-fractionated irradiation is not related to the simultaneous development of an inflammatory response. Also, the loss of the epidermal barrier function is not involved in the development of the acceleration response, which rather seems to be triggered directly by the decreased cellularity of the epidermis.
每日照射期间表皮再增殖加速的时间与皮肤红斑及表皮发育不全的发生有关。因此，研究了表皮屏障功能受损、真皮炎症反应和表皮发育不全与再增殖加速之间的关系。
对TUC小鼠大腿上约1 cm²的皮肤区域每周给予5次，每次3 Gy的剂量，然后在第一、第二或第三周结束时给予补充剂量，以确定残余表皮耐受性并计算第1、2或3周的再增殖率。在分次照射期间每日给予吲哚美辛以尝试对再增殖进行全身调节，而在分次照射开始前进行胶带剥离或紫外线B照射以尝试局部调节。在平行实验中，通过研究氚标记水的经表皮转运来离体测定表皮的水渗透系数。
在未进行调节的情况下，每日分次照射的第一周未发现再增殖，但再增殖在第二周补偿了所给剂量的30%，在第三周补偿了70%。仅在分次照射开始前进行胶带剥离可加速第一周的再增殖。紫外线B对再增殖没有影响，尽管它与胶带剥离一样能刺激增殖。吲哚美辛并未抑制再增殖的加速。发现经表皮水分流失显著增加，但仅在再增殖已经加速之后。
每日分次照射期间小鼠表皮再增殖的加速与炎症反应的同时发生无关。此外，表皮屏障功能的丧失不参与加速反应的发生，加速反应似乎是由表皮细胞数量减少直接触发的。
