In vivo micro-CT has already been used to monitor microstructural changes of bone in mice of different ages and in models of age-related diseases such as osteoporosis. However, as aging is accompanied by frailty and subsequent increased sensitivity to external stimuli such as handling and anesthesia, the extent to which longitudinal imaging can be applied in aging studies remains unclear. Consequently, the potential of monitoring individual mice during the entire aging process — from healthy to frail status — has not yet been exploited. In this study, we assessed the effects of long-term in vivo micro-CT imaging - consisting of 11 imaging sessions over 20 weeks - on hallmarks of aging both on a local (i.e., static and dynamic bone morphometry) and systemic (i.e., frailty index (FI) and body weight) level at various stages of the aging process. Furthermore, using a premature aging model (PolgA^{(D257A/D257A)}), we assessed whether these effects differ between genotypes. The 6th caudal vertebrae of 4 groups of mice (PolgA^{(D257A/D257A)} and PolgA^(+/+)) were monitored by in vivo micro-CT every 2 weeks. One group was subjected to 11 scans between weeks 20 and 40 of age, whereas the other groups were subjected to 5 scans between weeks 26-34, 32-40 and 40-46, respectively. The long-term monitoring approach showed small but significant changes in the static bone morphometric parameters compared to the other groups. However, no interaction effect between groups and genotype was found, suggesting that PolgA mutation does not render bone more or less susceptible to long-term micro-CT imaging. The differences between groups observed in the static morphometric parameters were less pronounced in the dynamic morphometric parameters. Moreover, the body weight and FI were not affected by more frequent imaging sessions. Finally, we observed that longitudinal designs including baseline measurements at young adult age are more powerful at detecting effects of in vivo micro-CT imaging on hallmarks of aging than cross-sectional comparisons between multiple groups of aged mice subjected to fewer imaging sessions.

中文翻译：

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长期体内显微CT成像对衰老小鼠骨质减少和虚弱的标志的影响

体内micro-CT已被用于监测不同年龄小鼠以及与年龄相关的疾病（例如骨质疏松症）模型中骨骼的微结构变化。然而，由于衰老伴随着身体虚弱以及随之而来的对外界刺激（如处理和麻醉）敏感性的增加，纵向成像在衰老研究中的应用程度尚不清楚。因此，尚未开发出在从健康到脆弱的整个衰老过程中监视单个小鼠的潜力。在这项研究中，我们评估了长期体内影响微型CT成像-包括20个星期的11次成像-在各个阶段的局部（即静态和动态骨形态测量）和全身性（即脆弱指数（FI）和体重）水平均具有衰老特征老化过程。此外，使用过早的衰老模型（PolgA ^{（D257A / D257A）}），我们评估了这些影响在基因型之间是否不同。通过体内监测4组小鼠（PolgA ^{（D257A / D257A）}和PolgA ^{（+ / +）}）的第六尾椎骨每2周进行一次微型CT。一组在年龄的20至40周之间进行了11次扫描，而另一组分别在26-34、32-40和40-46周之间进行了5次扫描。与其他组相比，长期监测方法显示出静态骨形态参数的微小但显着变化。然而，没有发现组与基因型之间的相互作用效应，这表明PolgA突变不会使骨骼或多或少地受到长期微CT成像的影响。在静态形态计量学参数中观察到的组之间的差异在动态形态计量学参数中不太明显。此外，体重和FI不受更频繁的影像学检查的影响。最后，