Spatial proteomics in the hippocampi of resistant and resilient individuals as compared to Alzheimer’s disease (AD) and primary age‐related tauopathy (PART).

Background An intriguing group of individuals, termed “resilient,” demonstrate neuropathologic changes consistent with Alzheimer disease (AD), yet display no cognitive impairment. In addition, there are older individuals who resist the development of AD neuropathologic change despite their age, termed “resistant.” Herein, we analyzed protein expression in the hippocampi around normal and neurofibrillary tangle (NFT)‐bearing neurons in these resistant and resilient individuals as compared to those with AD and primary age‐related tauopathy (PART) with cognitive decline. Method Utilizing Nanostring’s GeoMx™ Digital Spatial Profiling (DSP) technology, we compared individuals with AD neuropathologic change and dementia to individuals with AD neuropathologic change and no dementia (resilient), as well as PART with dementia and resistant (PART without dementia) cases. The DSP panel allows for spatial analysis of the level of expression of 73 different proteins in multiple regions of interest (ROIs) on formalin‐fixed paraffin‐embedded sections. We analyzed hippocampal sections, with our ROIs being NFT‐bearing neurons, non‐NFT‐bearing neurons, and their surrounding microenvironments (non‐neuronal cells and neuropil), including a comparison of entorhinal cortex, CA1 and CA2 subregions (Figures 1 and 2). Result Analyses comparing NFT‐bearing neurons to non‐NFT‐bearing neurons, revealed 22 proteins with differential expression, including various p‐tau epitopes, Neprilysin, ADAM10, IDE and GPNMB (Figure 3). Comparing resilient and AD NFTs, we identified 17 proteins with differential expression, including Park 5, HSC70 and VPS35 (Figure 4). The microenvironment of the resistant compared to others highlighted several proteins with differential expression including GFAP, NRGN and NEFL (Figure 5). A comparison of NFT‐bearing neurons in non‐demented cases displayed regional protein expression differences between entorhinal and CA1 including alpha‐synuclein and CSF1R. Distinct regional protein expression differences in NFT‐bearing neurons in demented cases were also identified including EMP1 and ATG12 (Figure 6). Conclusion In conclusion, using a novel spatial proteomic technique, we have demonstrated that resistant and resilient individuals display lower levels of inflammation and upregulation of protective pathways, that in turn lead to maintenance of neuronal integrity. In addition, although the resistant and resilient harbor PART and AD pathology (respectively), we have identified protein expression differences that may further our understanding of the mechanisms by which the resistant and resilient evade cognitive decline.