不同年龄段人群皮肤组织中两种mtDNA缺失研究

Detection of large deletions in mitochondrial DNA during skin aging

目的定量观察不同年龄段健康人群皮肤组织中线粒体DNA（mtDNA）大片段4977bp和3895bp缺失的发生情况，探讨与自然老化及日光照射之间的关联性。方法收集不同年龄段71例皮肤组织，曝光部位（颈项部、手背部或额面部）31例，非曝光部位（臀部、大腿部或腰腹部）40例，分别提取其基因组DNA，以普通PCR对mtDNA中的4977bp缺失和3895bp缺失突变进行扩增，并以荧光实时定量PCR法对mtDNA中的4977bp缺失和3895bp缺失突变进行定量检测和分析。结果普通PCR检测显示4977bp缺失和3895bp缺失的发生率均随年龄增大而增加，40岁以后人群中mtDNA的4977bp缺失和3895bp缺失发生率分别高达47．5％（19／40）和30．0％（12／40），显著高于40岁以前人群（Х^2分别为4．673，6．118，P〈0．05）。4977bp缺失和3895bp缺失在曝光部位的总发生率为48．4％（15／31）和32．3％（9／31），较非曝光部位升高，但两者相比差异并无统计学意义。定量PCR检测结果表明4977bp缺失和3895hp缺失的相对拷贝数无论在曝光还是非曝光部位，均与年龄增长呈正相关（丘分别为0．907，0．845，P〈0．05）；但4977bp缺失在曝光与非曝光部位的突变数相比差异无统计学意义（P=0．264），而3895bp缺失在曝光与非曝光部位相比差异却有统计学意义（P=0．014）。结论mtDNA中4977bp缺失主要与自然老化相关，可作为观察皮肤自然老化进程的指标之一。3895bp的缺失与紫外线照射具有更为密切的联系。

Objective To quantitatively observe the actual levels of 4977 bp and 3895 bp mitochondrial DNA （mtDNA） deletion in healthy human skin of different age, and to explore their relationship with intrinsic aging and photoaging. Methods Seventy-one samples of skin tissue were obtained from healthy volunteers, including 40 samples from UV-protected areas （buttock, thigh, waist or abdomen） and 31 from UV-exposed areas （neck, back of hands, forehead or face）. Nuclear and mitoehondrial DNA was extracted from these samples. Conventional PCR was performed to detect the incidence of 4977 bp and 3895 bp mtDNA deletion. Then, SYBR Green real-time PCR was applied to quantitatively analyze the target mutations in positive samples. Results Conventional PCR showed that the incidence of both 4977 bp deletion and 3895 bp deletion increased with age. For example, the incidence of 4977 bp deletion and 3895 bp deletion accounted for 47.5% （19/40） and 30% （12/40）, respectively in samples from volunteers older than 40 years, significantly higher than that in those from volunteers younger than 40 years （Х^2 = 4.673, 6.118, respectively, both P 〈 0.05）. The total incidence of 4977 hp deletion and 3895 hp deletion in UV-exposed areas was 48.4% （15/31 ） and 32.3% （9/31 ）, respectively, which did not differ from those in UV-protected areas. The results from real-time PCR revealed a positive correlation of the copy number of 4977 bp deletion and 3895 bp deletion with age （rs = 0.907, 0.845, respectively, both P 〈 0.05）. When the UV-exposed area was compared with the UV-protected area, no significant difference was found in the copy number of 4977 bp deletion （P = 0.264）, whereas a higher level of 3895 bp deletion was noticed in UV-exposed area （P = 0.014）. Conclusions The 4977 bp mtDNA deletion is primarily associated with chronological aging, and might serve as a biomarker for the process of chronological aging of skin. Deletion of 3895 bp mtDNA seems to be more susceptible to ultraviolet radiation.