Gonzalez, C. C.; Schurman, C. A.; Wilson, K. A.; Schilling, B.; Ellerby, L. M.; Tang, S. Y.

Chronic low back pain, commonly associated with intervertebral disc (IVD) degeneration, is highly prevalent in patients with Alzheimer\'s disease (AD), and the severity of the pain is correlated with the severity of the dementia. While incidences of both afflictions increase dramatically in the elderly population, it is unknown whether AD exacerbates the health of the IVD. Utilizing one-year-old male and female 5xFAD mice that constitutively express human APP and PSEN1 transgenes with five AD-linked mutations, we measured the lumbar IVDs extracellular matrix composition, the three-dimensional structure, degenerative score via histopathology, and mechanical behavior. The collagen, glycosaminoglycans, and advanced glycation end-products content of the IVD were not appreciably different between the 5xFAD animals and their wild-type littermates. Likewise, the 5xFAD IVDs were not histopathologically degenerated. However, the IVD volume, measured by contrast-enhanced microCT, was larger in the 5xFAD animals. Furthermore, dynamic microcompression revealed that 5xFAD IVDs exhibited higher loss tangent, indicating altered tissue damping and fluid-flow dynamics within the disc. These results suggest that although the IVDs of mice with AD are not more degenerated, they may be more susceptible to damage accumulation due to the elevated absorption of energy. Elderly individuals with AD may thus be more susceptible to IVD injuries that lead to eventual degeneration and spinal pain. Future work will focus on defining the molecular mechanisms and the consequences of these mechanical and structural changes in the IVD and their consequences to low back pain in individuals with AD.