Abstract：
Depilatory laser targeting melanin has been widely applied for the treatment of hypertrichosis. Both selective photothermolysis and thermal diffusion have been proposed for its effect, but the exact mechanism of permanent hair reduction remains unclear. In this study, we explore the role of thermal diffusion in depilatory laser-induced permanent hair loss and determine whether nonpigmented cells are injured by thermal diffusion.
C57BL/6 mice in anagen and telogen were treated with alexandrite laser (wavelength 755 nm, pulse duration 3 milliseconds, fluence 12 J/cm2 , spot size 12 mm), respectively. Histological analysis, terminal deoxynucleotidyl transferase dUTP nick-end labeling assay, and transmission electron microscopic imaging were employed to evaluate the injury to hair follicle (HF) cells. The proliferation status of HF cells was examined by 5-bromo-2\'-deoxyuridine pulse labeling. The number of HF stem cells was quantified by fluorescence-activated cell sorting. The size of the regenerated hair was determined by measuring its length and width.
We found that irradiating C57BL/6 mice in anagen with alexandrite laser led to hair miniaturization in the next anagen. In addition to thermal disruption of melanin-containing cells in the precortex region, we also detected necrosis of the adjacent nonpigmented dermal papilla cells due to thermal diffusion. Dermal papilla cells decreased by 24% after laser injury, while the number of bulge stem cells remained unchanged. When the laser was delivered to telogen HFs where no melanin was present adjacent to the dermal papilla, thermal necrosis and cell reduction were not detected in the dermal papilla and no hair miniaturization was observed.
Our results suggest that depilatory laser miniaturizes hair by inducing thermal necrosis of dermal papilla cells due to secondary thermal diffusion from melanin-containing precortex cells in the anagen hair bulbs.
C57BL/6 mice in anagen and telogen were treated with alexandrite laser (wavelength 755 nm, pulse duration 3 milliseconds, fluence 12 J/cm2 , spot size 12 mm), respectively. Histological analysis, terminal deoxynucleotidyl transferase dUTP nick-end labeling assay, and transmission electron microscopic imaging were employed to evaluate the injury to hair follicle (HF) cells. The proliferation status of HF cells was examined by 5-bromo-2\'-deoxyuridine pulse labeling. The number of HF stem cells was quantified by fluorescence-activated cell sorting. The size of the regenerated hair was determined by measuring its length and width.
We found that irradiating C57BL/6 mice in anagen with alexandrite laser led to hair miniaturization in the next anagen. In addition to thermal disruption of melanin-containing cells in the precortex region, we also detected necrosis of the adjacent nonpigmented dermal papilla cells due to thermal diffusion. Dermal papilla cells decreased by 24% after laser injury, while the number of bulge stem cells remained unchanged. When the laser was delivered to telogen HFs where no melanin was present adjacent to the dermal papilla, thermal necrosis and cell reduction were not detected in the dermal papilla and no hair miniaturization was observed.
Our results suggest that depilatory laser miniaturizes hair by inducing thermal necrosis of dermal papilla cells due to secondary thermal diffusion from melanin-containing precortex cells in the anagen hair bulbs.
摘要：
针对黑色素的脱毛激光已广泛应用于多毛症的治疗。选择性光热解和热扩散都被提出了它的效果，但永久性减发的确切机制尚不清楚。在这项研究中,我们探讨了热扩散在脱毛激光诱导的永久性脱发中的作用，并确定热扩散是否会损害非色素细胞。
C57BL/6小鼠在生长期和调生期用翠绿宝石激光（波长755nm，脉冲持续时间3毫秒，注量12J/cm2,光斑尺寸12毫米)，分别。组织学分析,末端脱氧核苷酸转移酶dUTP缺口末端标记测定，和透射电子显微镜成像用于评估毛囊（HF）细胞的损伤。通过5-溴-2'-脱氧尿苷脉冲标记检查HF细胞的增殖状态。通过荧光激活细胞分选对HF干细胞的数量进行定量。通过测量其长度和宽度来确定再生毛发的大小。
我们发现，在生长期中，用翠绿宝石激光照射C57BL/6小鼠会导致下一个生长期中的毛发小型化。除了前皮质区域含黑色素细胞的热破坏，我们还检测到邻近的无色素毛乳头细胞由于热扩散而坏死。激光损伤后毛乳头细胞减少24%，而凸起干细胞的数量保持不变。当激光被传递到皮肤乳头附近没有黑色素的静止期HFs时，在毛乳头中未检测到热坏死和细胞减少，也未观察到头发小型化。
我们的结果表明，脱毛激光通过诱导真皮乳头细胞的热坏死来使头发小型化，这是由于在生长期毛球中含有黑色素的前皮质细胞的二次热扩散所致。
C57BL/6小鼠在生长期和调生期用翠绿宝石激光（波长755nm，脉冲持续时间3毫秒，注量12J/cm2,光斑尺寸12毫米)，分别。组织学分析,末端脱氧核苷酸转移酶dUTP缺口末端标记测定，和透射电子显微镜成像用于评估毛囊（HF）细胞的损伤。通过5-溴-2'-脱氧尿苷脉冲标记检查HF细胞的增殖状态。通过荧光激活细胞分选对HF干细胞的数量进行定量。通过测量其长度和宽度来确定再生毛发的大小。
我们发现，在生长期中，用翠绿宝石激光照射C57BL/6小鼠会导致下一个生长期中的毛发小型化。除了前皮质区域含黑色素细胞的热破坏，我们还检测到邻近的无色素毛乳头细胞由于热扩散而坏死。激光损伤后毛乳头细胞减少24%，而凸起干细胞的数量保持不变。当激光被传递到皮肤乳头附近没有黑色素的静止期HFs时，在毛乳头中未检测到热坏死和细胞减少，也未观察到头发小型化。
我们的结果表明，脱毛激光通过诱导真皮乳头细胞的热坏死来使头发小型化，这是由于在生长期毛球中含有黑色素的前皮质细胞的二次热扩散所致。
