Hallam Dean, Wan Tengfei, Saretzki Gabriele
Institute for Cell and Molecular Bioscience, Newcastle University Institute for Ageing, Campus for Ageing and Vitality, Newcastle University Newcastle upon Tyne, UK.
Institute for Cell and Molecular Bioscience, Newcastle University Institute for Ageing, Campus for Ageing and Vitality, Newcastle University Newcastle upon Tyne, UK.
Exp Gerontol. 2015 Jul;67:72-9. doi: 10.1016/j.exger.2015.04.014. Epub 2015 Apr 30.
The cornea protects the anterior eye and accounts for two thirds of the eyes refractive capacity. The homeostasis of corneal epithelium is thought to be maintained by putative stem cells residing in the epithelial basal layer. As a tissue constantly exposed to environmental stress, the cornea is hypothesised to accumulate persistent DNA damage events with time in stem cell populations. Recently, telomere associated DNA damage foci (TAFs) have been suggested as a marker for persistent DNA damage which can be used to detect senescent cells during ageing. Dietary restriction (DR) is the only known non-genetic intervention that is able to increase both life and health span among various animal species. The aim of this study was to analyse changes in corneal properties with age and under 16 months of DR. We employed immunofluorescence staining for ɣH2A.X together with telomere fluorescence in situ hybridisation (immuno-FISH) on mouse corneas from young, old ad libitum (AL) fed as well as dietary restricted (DR) mice. Our data show that the central corneas of old mice had significantly more general and telomere-associated DNA damage compared to young mice while DR treatment was able to reduce the amount of DNA damage significantly. We also found that the thickness of the peripheral region of the cornea, where the putative stem cells may reside, decreased with age regardless of whether the animals underwent DR treatment or not. Number of bullae, which indicates corneal edema, accumulated in old corneas in the central area and DR treatment mitigated the formation of these bullae. Moreover, the protein levels of the stem cell marker TAp63 decreased with age only in the central but not the peripheral region of the cornea. This finding suggests that epithelial progenitors might be better maintained in the peripheral than the central cornea during ageing. Together with the finding that the peripheral corneal showed no increase in DNA damage during age, we speculate that in mice, like humans, the putative stem cells reside in the peripheral cornea.
角膜保护眼球前部，并构成眼睛三分之二的屈光能力。角膜上皮的稳态被认为是由位于上皮基底层的假定干细胞维持的。作为一个不断暴露于环境压力的组织，据推测，随着时间的推移，角膜干细胞群体中会积累持续性DNA损伤事件。最近，端粒相关DNA损伤灶（TAFs）被认为是持续性DNA损伤的标志物，可用于检测衰老过程中的衰老细胞。饮食限制（DR）是唯一已知的能够延长多种动物寿命和健康期的非遗传干预措施。本研究的目的是分析随着年龄增长以及在16个月的饮食限制条件下角膜特性的变化。我们对来自自由采食（AL）的年轻和老年小鼠以及饮食限制（DR）小鼠的角膜进行了γH2A.X免疫荧光染色以及端粒荧光原位杂交（免疫荧光原位杂交）。我们的数据表明，与年轻小鼠相比，老年小鼠的中央角膜存在明显更多的一般性和端粒相关DNA损伤，而DR处理能够显著减少DNA损伤的数量。我们还发现，假定干细胞可能所在的角膜周边区域的厚度随年龄增长而减小，无论动物是否接受DR处理。表明角膜水肿的大疱数量在老年角膜的中央区域积聚，DR处理减轻了这些大疱的形成。此外，干细胞标志物TAp63的蛋白质水平仅在角膜中央区域随年龄增长而降低，而在周边区域则没有。这一发现表明，在衰老过程中，角膜周边的上皮祖细胞可能比中央的上皮祖细胞得到更好的维持。结合周边角膜在衰老过程中DNA损伤没有增加这一发现，我们推测，与人类一样，小鼠的假定干细胞存在于周边角膜中。
