ORCID
https://orcid.org/0000-0002-7472-455X
Date of Award
8-24-2023
Degree Name
Doctor of Philosophy (PhD)
Degree Type
Dissertation
Abstract
Traumatic brain injury (TBI) is a significant public health concern. Elderly individuals are more likely to be hospitalized and die from a TBI than younger victims, and experience worse outcomes along a series of clinical and functional endpoints. Studies exploring the mechanisms responsible for these outcome disparities are limited. As aging has been demonstrated to enhance baseline neuroinflammatory profile and is associated with synaptopathic neurodegenerative conditions linked to TBI, this thesis study sought to better characterize the relationship between aging-related neuroinflammation, microstructural—including synaptic—endpoints, and functional outcome following TBI. To this end, mice were subjected to diffuse and focal experimental brain injury at adult (3 months) and aged (18 months) time points. Microglial numbers and activity and hippocampal synapse and neuron loss were quantified along with learning and memory and anxiety-like behaviors at approximately one month post-injury. TBI impaired learning and memory and decreased hippocampal synaptic density in both age groups, but an effect of age was not detected. Aging similarly had no detectable, specific effect on hippocampal neuron loss in the setting of TBI, though older animals appeared to suffer greater lesion size and disruption of hippocampus. TBI increased microglial density and proliferation, which was potentiated in aged animals. Microglial endosomal/lysosomal quantity and microglial phagocytosis of synaptic proteins were both increased by TBI, but there was no statistically-significant effect of age. These data support an enhanced cellular neuroinflammatory potential in aged animals following TBI, but minimal differences in specific structural or functional endpoints. This thesis furthermore describes two novel immunofluorescence-based protocols developed in service of better understanding the role of TBI on synaptic health. The first protocol, SEQUIN, utilizes super-resolution microscopy to achieve synaptic resolution, enabling high throughput compared to related techniques. SEQUIN was used to quantify the density of excitatory synapses in the molecular layer of the CA1 region. The second technique introduced an additional channel to standard immunofluorescence microscopy using a long Stokes-shifted fluorophore. This approach allowed for rigorous, quantitative, super-resolution imaging of four antigens in a single experiment. By utilizing this technique two synaptic proteins, microglia, and CD68 were all analyzed simultaneously, facilitating the study of synaptic phagocytosis.
Language
English (en)
Chair and Committee
Terrance Kummer
Recommended Citation
Oswalt Reitz, Sydney J., "Effect of Age at Injury on Neuroinflammatory Response, Microstructural Outcomes, and Function Following Traumatic Brain Injury" (2023). Arts & Sciences Electronic Theses and Dissertations. 3133.
https://openscholarship.wustl.edu/art_sci_etds/3133