Dubicanac Marko, Strueve Julia, Mestre-Frances Nadine, Verdier Jean-Michel, Zimmermann Elke, Joly Marine
Institute of Zoology, Tierärztliche Hochschule Hannover, Hanover, Lower Saxony, Germany.
Clinic for Small Animals, Tierärztliche Hochschule Hannover, Hanover, Lower Saxony, Germany.
PeerJ. 2017 May 4;5:e3258. doi: 10.7717/peerj.3258. eCollection 2017.
Opacities of the lens are typical age-related phenomena which have a high influence on photoreception and consequently circadian rhythm. In mouse lemurs, a small bodied non-human primate, a high incidence (more than 50% when >seven years) of cataracts has been previously described during aging. Previous studies showed that photoperiodically induced accelerated annual rhythms alter some of mouse lemurs' life history traits. Whether a modification of photoperiod also affects the onset of age dependent lens opacities has not been investigated so far. The aim of this study was therefore to characterise the type of opacity and the mouse lemurs' age at its onset in two colonies with different photoperiodic regimen.
Two of the largest mouse lemur colonies in Europe were investigated: Colony 1 having a natural annual photoperiodic regime and Colony 2 with an induced accelerated annual cycle. A slit-lamp was used to determine opacities in the lens. Furthermore, a subset of all animals which showed no opacities in the lens nucleus in the first examination but developed first changes in the following examination were further examined to estimate the age at onset of opacities. In total, 387 animals were examined and 57 represented the subset for age at onset estimation.
The first and most commonly observable opacity in the lens was nuclear sclerosis. Mouse lemurs from Colony 1 showed a delayed onset of nuclear sclerosis compared to mouse lemurs from Colony 2 (4.35 ± 1.50 years 2.75 ± 0.99 years). For colony 1, the chronological age was equivalent to the number of seasonal cycles experienced by the mouse lemurs. For colony 2, in which seasonal cycles were accelerated by a factor of 1.5, mouse lemurs had experienced 4.13 ± 1.50 seasonal cycles in 2.75 ± 0.99 chronological years.
Our study showed clear differences in age at the onset of nuclear sclerosis formation between lemurs kept under different photoperiodic regimes. Instead of measuring the chronological age, the number of seasonal cycles ( = four) experienced by a mouse lemur can be used to estimate the risk of beginning nuclear sclerosis formation. Ophthalmological examinations should be taken into account when animals older than 5-6 seasonal cycles are used for experiments in which unrestricted visual ability has to be ensured. This study is the first to assess and demonstrate the influence of annual photoperiod regime on the incidence of lens opacities in a non-human primate.
晶状体混浊是典型的与年龄相关的现象，对光感受器有很大影响，进而影响昼夜节律。在小鼠狐猴（一种小型非人类灵长类动物）中，先前已描述其在衰老过程中白内障发病率很高（7岁以上时超过50%）。先前的研究表明，光周期诱导的加速年度节律会改变小鼠狐猴的一些生活史特征。到目前为止，尚未研究光周期的改变是否也会影响年龄依赖性晶状体混浊的发生。因此，本研究的目的是在两个具有不同光周期方案的群体中，表征混浊的类型以及小鼠狐猴出现混浊时的年龄。
对欧洲最大的两个小鼠狐猴群体进行了研究：群体1具有自然年度光周期模式，群体2具有诱导的加速年度周期。使用裂隙灯来确定晶状体混浊情况。此外，对所有在首次检查时晶状体核未出现混浊但在后续检查中出现首次变化的动物子集进行进一步检查，以估计混浊开始出现时的年龄。总共检查了387只动物，其中57只作为估计混浊开始年龄的子集。
晶状体中最早且最常见的混浊是核硬化。与群体2的小鼠狐猴相比，群体1的小鼠狐猴核硬化出现延迟（4.35±1.50岁对2.75±0.99岁）。对于群体1，实际年龄等同于小鼠狐猴经历的季节周期数。对于群体2，其中季节周期加速了1.5倍，小鼠狐猴在2.75±0.99实际年龄中经历了4.13±1.50个季节周期。
我们的研究表明，处于不同光周期模式下的狐猴在核硬化形成开始时的年龄存在明显差异。可以使用小鼠狐猴经历的季节周期数（=4个）来估计开始形成核硬化的风险，而不是测量实际年龄。当使用超过5 - 6个季节周期的动物进行必须确保无限制视觉能力的实验时，应考虑进行眼科检查。本研究首次评估并证明了年度光周期模式对非人类灵长类动物晶状体混浊发生率的影响。
