The relative contributions of cell-dependent cortical microcircuit aging to cognition and anxiety. The relative contributions of cell-dependent cortical microcircuit aging to cognition and anxiety

Background: Aging is accompanied by altered thinking (cognition) and feeling (mood) functions that depend to some extent on information processing by brain cortical cell microcircuits. We hypothesized that age-associated long-term functional and biological changes are mediated by gene transcriptomic changes within neuronal cell-types forming cortical microcircuits, namely excitatory pyramidal cells (PYC) and inhibitory GABAergic neurons expressing vasoactive intestinal peptide (Vip), somatostatin (Sst) and parvalbumin (Pvalb). Methods: To test this hypothesis, we assessed locomotor, anxiety-like and cognitive behavioral changes between young (2 months, n=9) and old (22 months, n=12) male C57BL/6 mice, and performed frontal cortex cell-type specific molecular profiling, using laser-capture microscopy and RNA sequencing. Results: Old-mice displayed increased anxiety and reduced working memory. The four cell-types displayed distinct age-related transcriptomes and biological pathway profiles, affecting metabolic and cell signaling pathways, and selective markers of neuronal vulnerability (Ryr3), resilience (Oxr1), and mitochondrial dynamics (Opa1), suggesting high age-related vulnerability of PYCs, and variable degree of adaptation in GABAergic neurons. Correlations between gene expression and behaviors suggest that changes in cognition and anxiety associated with age are partly mediated by normal age-related cell changes, and that additional age-independent decreases in synaptic and signaling pathways, notably in PYC and SST-neurons further contribute to behavioral changes. Conclusions: Our study demonstrates cell-dependent differential vulnerability and coordinated cell-specific cortical microcircuit molecular changes with age. Collectively, the results suggest intrinsic molecular links between aging, cognition and mood-related behaviors with SST-neurons contributing evenly to both behavioral conditions. Overall design: Male C57BL/6 mice, Young (2 months, n=9) and old (22 months, n=12), performed frontal cortex cell-type specific molecular profiling, using laser-capture microscopy and RNA sequencing using illumina HiSeq

研究背景：衰老会伴随认知（cognition）与情绪（mood）功能的改变，而这些功能在一定程度上依赖于大脑皮层细胞微环路的信息处理。本研究假设，衰老相关的长期功能与生物学变化，由构成皮层微环路的神经元细胞类型内的基因转录组变化所介导，这些细胞类型包括兴奋性锥体神经元（excitatory pyramidal cells, PYC），以及表达血管活性肠肽（vasoactive intestinal peptide, Vip）、生长抑素（somatostatin, Sst）和小白蛋白（parvalbumin, Pvalb）的抑制性GABA能神经元（GABAergic neurons）。
研究方法：为验证上述假设，本研究对年轻（2月龄，n=9）与老年（22月龄，n=12）雄性C57BL/6小鼠的运动、类焦虑及认知行为变化进行评估，并通过激光捕获显微切割（laser-capture microscopy）与RNA测序（RNA sequencing）技术对前额叶皮层开展细胞类型特异性分子谱分析。
研究结果：老年小鼠表现出焦虑水平升高与工作记忆减退。四种细胞类型均呈现出独特的衰老相关转录组与生物学通路特征，影响代谢及细胞信号通路，并涉及神经元易感性标记物Ryr3、抗逆性标记物Oxr1以及线粒体动力学标记物Opa1，提示兴奋性锥体神经元（PYC）具有较高的衰老相关易感性，而GABA能神经元则存在程度不一的适应性变化。基因表达与行为学指标的相关性分析表明，衰老相关的认知与焦虑变化部分由正常衰老介导的细胞变化所驱动；此外突触与信号通路的非衰老依赖性下调（尤其是在PYC与SST神经元中）进一步加剧了行为学改变。
研究结论：本研究证实了衰老过程中细胞依赖性的易感性差异，以及皮层微环路中细胞特异性的协同分子变化。综合来看，本研究结果揭示了衰老、认知与情绪相关行为之间的内在分子关联，其中SST神经元对这两类行为改变均具有均等的贡献。
实验整体设计：以雄性C57BL/6小鼠为研究对象，分为年轻组（2月龄，n=9）与老年组（22月龄，n=12），通过激光捕获显微切割与RNA测序（采用illumina HiSeq平台）对前额叶皮层开展细胞类型特异性分子谱分析。