Neurofibrillary tangles and senile plaques in aged bears

Area of Science:

• Comparative pathology
• Neuroscience
• Gerontology

Background:

• Aging humans and Alzheimer's disease (AD) patients exhibit neuronal cytoskeletal abnormalities, including neurofibrillary tangles (NFT) and senile plaques (SP).
• While SP are found in various species, NFT with human-like characteristics have not been previously identified in non-human mammals.

Purpose of the Study:

• To investigate the presence of age-related cytoskeletal abnormalities in nonprimate mammals, specifically aged bears.
• To compare the pathological findings in bears with those observed in human aging and Alzheimer's disease.

Main Methods:

• Examination of brain tissue from five aged bears (20-30 years old).
• Immunocytochemical analysis using antibodies against phosphorylated neurofilaments (NF), tau, A68 (AD-associated protein), and paired helical filament (PHF) antigen.
• Histopathological assessment for the presence of NFT and SP.

Main Results:

• An aged Asiatic brown bear exhibited NFT composed of 10-16 nm filaments, immunoreactive to antibodies for phosphorylated NF, tau, A68, and PHF antigen.
• An aged polar bear presented numerous SP with neurites immunoreactive to phosphorylated NF antibodies, but without identified NFT.
• These findings demonstrate age-related cytoskeletal abnormalities in nonprimate species.

Conclusions:

• Nonprimate mammals, such as bears, can develop age-related cytoskeletal abnormalities analogous to those in humans.
• Comparative pathology studies in aged mammals offer a valuable model for understanding the pathogenesis of neurodegenerative changes.
• Further research into comparative mammalian pathology may illuminate mechanisms underlying age-associated neurological disorders.