Degenerating Tanycytes Disrupt Tau Removal, Shaping Alzheimer’s Progression

Tau‑clearing cells in the brain may offer new clues to slowing Alzheimer’s disease progression, according to a study titled “Tanycytic degeneration impairs tau clearance and contributes to Alzheimer’s disease pathology,” from Kyoto University and INSERM, published in Cell Press Blue. The work identifies a previously unrecognized mechanism by which the tau protein accumulates in the brain—a hallmark of Alzheimer’s pathology—and points to a specialized group of cells, called tanycytes, as key players in clearing tau from the cerebrospinal fluid (CSF) to the blood.

“Tanycytes, whose cell bodies line the walls and floor of the third ventricle and extend long, slim processes that terminate in ‘endfeet’ that contact these fenestrated capillaries,” act as a shuttle between the CSF and the blood, the authors wrote. The new study suggests they also act as a kind of molecular “exit ramp,” moving tau out of the CSF and into the bloodstream for disposal. When these cells become fragmented, that clearance system falters. Tau, which should be ferried away, instead lingers—much like traffic backing up when a major off‑ramp closes—allowing toxic protein species to accumulate.

“Our findings reveal a previously underappreciated, disease‑relevant role for tanycytes in neurodegeneration,” said corresponding author Vincent Prévot, PhD, of INSERM. “Focusing on tanycyte health could be a way to improve tau clearance and limit disease progression.”

Using rodent and cellular models, the researchers showed that tanycytes take up tau from the CSF and release it into pituitary portal capillaries, enabling its entry into the systemic circulation, according to the authors. When the team blocked vesicular transport in tanycytes, tau clearance from CSF to blood slowed dramatically, and tau pathology intensified. As the authors wrote, “Blocking tanycytic vesicular transport blunts CSF‑to‑blood tau efflux and potentiates tau pathology.”

“We were able to show in rodent and cellular models not only that tanycytes were indeed involved in clearing tau but also that tanycytes in the brains of human Alzheimer’s patients were fragmented and had changes in gene expression related to this shuttle function,” Prévot said in a press release.

The group then turned to human samples. In postmortem brain tissue from Alzheimer’s patients, tanycytes appeared structurally compromised, with fragmented processes and marked transcriptomic changes—particularly in genes linked to vesicular transport. These alterations captured by single-nucleus RNA sequencing, the authors noted, “[explain] this clearance deficit” and provide the first evidence that tanycytic dysfunction contributes directly to human disease. “Our findings provide the first evidence for structural and functional alterations in these little‑known but key brain cells in human disease,” Prévot said.

The study also examined tau levels in patient fluids. Individuals with Alzheimer’s showed decreased plasma‑to‑CSF ratios of total and p181 tau, consistent with impaired movement of tau out of the brain and into circulation. Together, the animal, cellular, and human data support the existence of a brain‑to‑blood “tanycytic shuttle” whose breakdown may accelerate tau accumulation.

The researchers emphasize that maintaining tanycyte function is unlikely to be the sole answer to Alzheimer’s, but it may represent a promising new angle. They also acknowledge key limitations, including the lack of robust animal models that fully recapitulate human disease and the need for larger, longitudinal patient cohorts.

Still, the work broadens the landscape of Alzheimer’s biology by highlighting a cell type rarely considered in neurodegeneration. By illuminating how tau normally exits the brain—and what happens when that system fails—the study opens the door to potential interventions aimed at preserving or restoring this clearance pathway.