Abstract
Recent human trials of treatments for Alzheimer's disease (AD) have been largely unsuccessful, raising the idea that treatment may need to be started earlier in the disease, well before cognitive symptoms appear. An early marker of AD pathology is therefore needed and it is debated as to whether amyloid-βAβ? plaque load may serve this purpose. We investigated this in the hAPP-J20 AD mouse model by studying disease pathology at 6, 12, 24 and 36 weeks. Using robust stereological methods, we found there is no neuron loss in the hippocampal CA3 region at any age. However loss of neurons from the hippocampal CA1 region begins as early as 12 weeks of age. The extent of neuron loss increases with age, correlating with the number of activated microglia. Gliosis was also present, but plateaued during aging. Increased hyperactivity and spatial memory deficits occurred at 16 and 24 weeks. Meanwhile, the appearance of plaques and oligomeric Aβ were essentially the last pathological changes, with significant changes only observed at 36 weeks of age. This is surprising given that the hAPP-J20 AD mouse model is engineered to over-expresses Aβ. Our data raises the possibility that plaque load may not be the best marker for early AD and suggests that activated microglia could be a valuable marker to track disease progression.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Age Factors
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Alzheimer Disease / diagnosis
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Alzheimer Disease / genetics
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Alzheimer Disease / metabolism
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Alzheimer Disease / pathology*
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Amyloid beta-Protein Precursor / genetics*
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Amyloid beta-Protein Precursor / metabolism
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Animals
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Biomarkers / metabolism
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CA1 Region, Hippocampal / metabolism
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CA1 Region, Hippocampal / pathology*
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CA3 Region, Hippocampal / cytology
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CA3 Region, Hippocampal / metabolism
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Cell Count
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Disease Models, Animal
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Early Diagnosis
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Gene Expression
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Gliosis / diagnosis
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Gliosis / genetics
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Gliosis / metabolism
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Gliosis / pathology*
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Humans
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Inflammation
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Male
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Memory Disorders / diagnosis
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Memory Disorders / genetics
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Memory Disorders / metabolism
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Memory Disorders / pathology*
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Mice
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Mice, Transgenic
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Microglia / metabolism
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Microglia / pathology*
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Neurons / metabolism
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Neurons / pathology
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Plaque, Amyloid / diagnosis
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Plaque, Amyloid / genetics
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Plaque, Amyloid / metabolism
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Plaque, Amyloid / pathology*
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Stereotaxic Techniques
Substances
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Amyloid beta-Protein Precursor
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Biomarkers
Grants and funding
Funding provided by Iain S. Gray Foundation, Stanley and John Roth, Patricia A. Quick foundation, David King, Doug Battersby, Tony and Vivian Howland-Rose, Walter and Edith Sheldon, Gleneagle Securities, Bill Gruy, Geoffrey Towner, Amadeus Energy Ltd., Nick and Melanie Kell, J. O. and J. R. Wicking Trust and the Mason Foundation, the New South Wales Government, through their office for Science and Medical Research, and SpinalCure Australia. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.