The molecular assembly of perineuronal nets by super-resolution microscopy in ageing brains.

神经元周网（Perineuronalnets，PNN）是一种特殊的细胞外基质结构，它包裹着中枢神经系统内的特定神经元群体。PNN成熟与关键期关闭相吻合，我们观察到可塑性显着下降。目前的研究表明PNN通过三种主要机制控制突触可塑性：a）创建物理屏障以引导轴突终止，B）携带轴突发芽的抑制分子，以及c）限制突触处的受体运动。因此，我们认为，PNN的操纵可能提供一个新的目标可塑性操纵神经退行性疾病，如阿尔茨海默氏病。PNN的酶促降解已经显示出在动物模型中恢复幼年水平的可塑性，然而我们仍然面临着这些治疗的靶向特异性、递送和稳定性的挑战。此外，我们必须进一步询问PNN分子组装的机制以及PNN分子与突触的原位关系，以了解我们如何操纵PNN用于治疗用途。通过使用超分辨率扩展显微镜，我们的目标是在15 nm分辨率下识别PNN分子和突触的空间关系。我们将克服传统光学显微镜的衍射极限，将培养的原代PNN神经元嵌入水凝胶中，水凝胶将进行各向同性膨胀，从而使我们能够在分子水平上可视化PNN结构。结合对PNNs的进一步生物物理和动力学分析，我们的目标是发现PNNs在神经元表面的分子组装机制。

Perineuronal nets (PNNs) are specialised extracellular matrix structures that encase specific neuron populations within the central nervous system. PNN maturation coincides with critical period closure, where we observe a significant decrease in plasticity. Current research implicates PNNs in the control of synaptic plasticity via three main mechanisms: a) creating a physical barrier to guide axon termination, b) harbouring inhibitory molecules of axon sprouting, and c) limiting receptor motility at the synapse. Hence, we believe that manipulation of PNNs may provide a novel target for plasticity manipulation in neurodegenerative diseases, like Alzheimer's Disease. Enzymatic degradation of PNNs has already been shown to retrieve juvenile levels of plasticity in animal models, however we still face challenges with target specificity, delivery, and stability of these treatments. Furthermore, we must further interrogate the mechanisms of PNN molecular assembly and the relationship of PNN molecules to the synapse in situ, in order to understand how we can manipulate PNNs for therapeutic use. Through the use of super-resolution expansion microscopy, we aim to identify the spatial relationship of PNN molecules and synapses at 15 nm resolution. We will overcome the diffraction limit of conventional optical microscopy by embedding cultured primary PNN neurons in a hydrogel, that will undergo isotropic expansion, thereby allowing us to visualise PNN structures at the molecular level. In combination with further biophysical and dynamic analysis of PNNs we aim to discover the mechanisms of molecular assembly of PNNs on the surface of neurons.