Characterization of the spatial and temporal response to tau in chronic traumatic encephalopathy - Repetitive head injuries (RHI) from contact sports such as American football, hockey, and soccer, or military service and intimate partner violence can occur upwards of 1000s of times each year for decades in some cases. The cumulative damage from these hits have been shown to have profound consequences ranging behavior and cognitive clinical impairments to overt dementia demonstrating that millions of individuals might be at risk for long term neurodegeneration after RHI exposure. RHI, specifically the non-concussive injuries, are strongly linked to the neurodegenerative disease chronic traumatic encephalopathy (CTE). CTE is a tauopathy where hyperphosphorylated tau (ptau) pathology begins in the frontal cortex at the depths of the cortical sulcus with foci of neuronal ptau aggregates found around blood vessels (CTE lesion). However, as the disease progresses, ptau deposition is enhanced and spreads from the frontal cortex to the medial temporal lobe, and ultimately the whole brain is involved at end stage. Until recently, it was entirely unknown what mechanisms might be involved linking RHI induced damage to early CTE pathogenesis. However, our initial work has identified neuroinflammation as a likely driver of disease. To better understand how RHI and ptau affects the brain during CTE, we will use our unique resource, the Boston University CTE brain bank, the largest CTE brain bank in the world, to select subjects to profile using cutting edge approaches. We will use frozen tissue from frontal cortex, hippocampus, and calcarine cortex in each subject that capture early, middle, and late involvement of ptau progression from individuals diagnosed with RHI exposure and no CTE, low stage CTE, high stage CTE, and appropriate controls. First, we will perform single nuclei RNA sequencing (snRNAseq) to compare cell population changes among our groups and across disease progression. In addition, we will use proximal frozen tissue sections to perform ptau and Aβ ELISAs to measure pathologic protein accumulation in direct contact with the cells assayed by snRNAseq. We will then perform spatial transcriptomics to investigate how local cell populations are directly related to pathology using the same snRNAseq tissue. The sections will be stained for ptau and Aβ pathology prior to sequencing and spatial transcriptomics data will be registered to and correlated with CTE lesions and Aβ plaques. Finally, we will utilize a cutting-edge tissue culture paradigm to examine mechanistic connections. We will culture 3D human derived forebrain cortical spheroids (CS) that contain all the major brain cell types. CS will be treated with isolated ptau aggregates from CTE, and we will examine, tau seeding, phagocytosis, reactive phenotypes, and genomic profiles to determine the individual neurodegenerative effects. Overall, these findings will be critical in advancing our understanding of how ptau pathology influences the distinct neuroimmune phenotypes present in the brain and drives disease. Better characterization of human disease will lead to better disease models which are critically needed to aid in the discovery of disease modifying therapies or novel in-life biomarkers. We expect the findings will shed light not only into CTE, but other tauopathies as well.
