The research team, led by Rui Zeng, Jiaxu Zhao, Haibao Peng and senior author Yudan Chi at Fudan University in Shanghai, began with an observation from the clinic. Reviewing magnetic resonance imaging and computed tomography scans of patients with breast and lung cancer, they noticed that dural metastases produce a distinctive pattern of cranial erosion, with thinning of the skull bone directly above the tumor lesions. This signature was absent in patients with brain metastases, leptomeningeal metastases or meningiomas, suggesting that something unique was happening at the interface between the skull and the dura when tumor cells settled there. The erosion was not incidental damage; it was a clue that bone-resorbing cells were active participants in the disease process.

To interrogate that clue, the researchers built a mouse model of dural metastasis in which fluorescently labeled tumor cells home specifically to the dura mater. Using bioluminescence imaging and histological analysis, they confirmed that the model faithfully recapitulates the human pattern of dural colonization and skull erosion. They then turned their attention to the meningeal lymphatic vessels, the network of thin-walled channels discovered to line the dura and drain fluid and immune cells from the central nervous system to the deep cervical lymph nodes. Since their characterization in 2015, these vessels have been recognized as a critical highway for anti-tumor immunity, allowing T cells primed in the meninges to mount responses against brain tumors. In the dural metastasis model, that highway was in ruins.

Through intravital two-photon microscopy, which allows researchers to watch living tissue in real time through a surgically prepared window, the team documented dramatic impairments in lymphatic drainage as tumors progressed. The vessels adjacent to tumor lesions became dilated, developed blebs, and suffered local structural injuries. Functional tracer studies, in which fluorescent dextran and protein tracers were injected into the cerebrospinal fluid and tracked to the deep cervical lymph nodes, confirmed that drainage capacity collapsed in tumor-bearing animals. Notably, the researchers found that the tumors did not simply sprout new lymphatic vessels or prune existing ones wholesale; instead, the architecture of the vessels was disrupted in a way that suggested mechanical or biochemical sabotage rather than simple lymphangiogenesis.

The identity of the saboteurs emerged from single-cell RNA sequencing of the dural tumor microenvironment. The analysis revealed a strongly immunosuppressive landscape, with T cells showing clear molecular signatures of exhaustion, including elevated expression of inhibitory receptors such as PD1 and TIM3 and diminished cytotoxic function. Among the immune and stromal populations, cancer-associated osteoclasts stood out. Using a genetic reporter system that labels cathepsin K-expressing cells, the team traced two distinct osteoclast populations: large osteoclasts that localized specifically at the skull-tumor interface, where they carved resorption cavities into the bone, and smaller osteoclasts that permeated the intratumoral regions. Dynamic imaging showed these two subsets were interrelated, with the interface population appearing to seed the intratumoral one.

The causal link between osteoclasts and lymphatic destruction was tested pharmacologically. When the researchers depleted osteoclasts with zoledronic acid, a bisphosphonate drug already approved for the treatment of bone metastases and osteoporosis, the meningeal lymphatic vessels recovered their structure and their drainage function. Tracer flow to the deep cervical lymph nodes was restored, vessel dilation and injury diminished, and, critically, the exhausted T cell population in the dura rebounded. Tumor growth slowed, and survival improved in the treated animals. The effect depended on intact lymphatic drainage: when the researchers surgically ligated the drainage pathways in zoledronic acid-treated mice, the anti-tumor benefit was largely abolished, demonstrating that the drug was working not by directly killing tumor cells but by reopening the immune corridor that the tumors had shut down.

The mechanistic culprit turned out to be angiopoietin-2, a signaling molecule secreted by the osteoclasts themselves. Angiopoietin-2 is known to destabilize blood vessels, but its role in lymphatic biology is context-dependent, determined in part by the endothelial phosphatase VEPTP. In the dural metastasis model, osteoclast-derived angiopoietin-2 was sufficient to disrupt lymphatic vessel integrity even in the absence of tumors: administering the protein to healthy mice or to zoledronic acid-treated tumor-bearing mice reproduced the drainage defects. Conversely, knocking down Angpt2 expression specifically in cathepsin K-expressing cells using an adeno-associated viral vector restored lymphatic structure and drainage, reduced T cell exhaustion, slowed tumor growth and extended survival. The team also ruled out a parallel candidate, PDGF-BB, which showed no effect on lymphatic drainage or tumor progression, sharpening the case for angiopoietin-2 as the key mediator.

The implications extend beyond dural metastasis. Meningeal lymphatic vessels have been implicated in glioblastoma immunity, in the efficacy of radiotherapy, and in the response to checkpoint blockade immunotherapy, and recent work has shown that osteoclasts can undermine immunotherapy in bone metastases through other secreted factors. The new study connects these threads, positioning the skull-dura interface as a battleground where bone-resorbing cells, acting under tumor influence, disable the very drainage routes that anti-tumor T cells need. It also fits within a broader rethinking of skull bone marrow as an active immunological compartment, connected to the brain surface through specialized channels and responsive to pathological signals from the central nervous system and its coverings.

Translational prospects are tantalizing but cautious. Zoledronic acid is already in widespread clinical use, and patients with bone metastases routinely receive it, yet dural metastasis remains a clinical challenge, suggesting that timing, dosing and delivery will matter enormously. The selective angiopoietin-2 knockdown strategy used in mice is far from bedside readiness, though anti-angiopoietin-2 agents have been explored in oncology trials for other purposes. What the study provides, above all, is a conceptual framework: dural metastasis is not merely tumor growth in an inconvenient location, but a coordinated hijacking of the meningeal lymphatic system by tumor-corrupted osteoclasts, a process that can in principle be reversed. If that reversal can be achieved safely in patients, the brain’s own drainage highways might once again carry the immune cells needed to fight back.

Subject of Research: The role of osteoclast-derived angiopoietin-2 in disrupting meningeal lymphatic drainage during dural metastasis

Article Title: Osteoclasts intercept meningeal lymphatic paths for dural metastasis

Article References: Zeng, R., Zhao, J., Peng, H., Ma, J., Hua, S., Zeng, Y., Li, X., Huang, Y., Li, C., Yang, J., Chen, H., Feng, X., Zhang, Q., Chen, L., & Chi, Y. (2026). Osteoclasts intercept meningeal lymphatic paths for dural metastasis. Nature. https://doi.org/10.1038/s41586-026-11082-6

Image Credits: AI Generated

DOI: 10.1038/s41586-026-11082-6

Keywords: dural metastasis, osteoclasts, meningeal lymphatic vessels, angiopoietin-2, zoledronic acid, T cell exhaustion, tumor microenvironment, single-cell RNA sequencing, breast cancer, lung cancer, skull erosion, cancer immunotherapy

For most of neuroscience history, the brain was considered an immune-privileged organ with no lymphatic drainage at all. That assumption posed a puzzle: the brain consumes 20 to 25 percent of the body’s total energy, generating mountains of metabolic byproducts, yet seemed to lack the lymphatic vessels every other organ relies on for waste removal. The answer began to emerge in 2012, when researcher Jeffrey Iliff and colleagues used fluorescent tracers in mice to show that cerebrospinal fluid flows deep into brain tissue along channels surrounding blood vessels, exchanges with the fluid bathing neurons, and exits through venous pathways. Because this process depends on aquaporin-4, a water channel protein concentrated on the ends of star-shaped astrocyte processes, the pathway was named the glymphatic system — a glial-dependent cousin of the lymphatic system.

The mechanics are elegant. Cerebrospinal fluid, produced by the choroid plexus in the brain’s ventricles, pulses along perivascular spaces driven by arterial pulsations from the heartbeat. At the same time, rhythmic breathing creates pressure changes that mechanically dilate these channels, acting as a second major pump. Aquaporin-4 channels on astrocyte endfeet, which sheath up to 98 percent of cerebral blood vessels, then shuttle the fluid into brain tissue, where it mixes with interstitial fluid and collects metabolic debris including amyloid-beta, tau, alpha-synuclein, and inflammatory cytokines. The waste-laden fluid drains back out along venous pathways, eventually reaching deep cervical lymph nodes in the neck and the peripheral lymphatic system.

In 2015, a second discovery completed the picture. Jonathan Kipnis’s laboratory identified functional lymphatic vessels lining the dural sinuses of the brain’s outer membrane — vessels that had been hiding in plain sight for centuries. These meningeal lymphatic vessels express classic lymphatic endothelial markers, transport cerebrospinal fluid and immune cells to deep cervical lymph nodes, and serve as a bridge between the brain’s immune surveillance and the body’s peripheral immune system. In 2019, researchers confirmed that vessels at the skull base are the primary route for clearing large molecules from cerebrospinal fluid, and by 2022, three-dimensional MRI had visualized these structures in living humans for the first time, revealing age-related thickening of the vessels and shrinkage of the lymph nodes they feed.

The connection to Alzheimer’s disease is now supported by converging evidence from animal models and human imaging. Mice engineered to lack aquaporin-4 show roughly a 70 percent reduction in interstitial solute clearance and accelerated amyloid accumulation. In human patients, diffusion tensor imaging along perivascular spaces — a technique that quantifies water movement in these channels — reveals reduced glymphatic function not only in established Alzheimer’s dementia but in prodromal and even preclinical stages, with the decline detectable before cerebrospinal fluid amyloid markers cross pathological thresholds. Postmortem studies show that loss of aquaporin-4’s polarized localization on astrocyte endfeet correlates specifically with Alzheimer’s status, amyloid burden, and advanced disease stages, independent of age.

Sleep emerges as perhaps the most potent modulator of this system. During deep non-REM sleep, the space between brain cells expands by roughly 60 percent, dramatically lowering resistance to fluid flow and boosting waste clearance. Interstitial amyloid-beta levels rise during wakefulness and fall during sleep, while sleep deprivation elevates tau levels by more than 50 percent in humans and accelerates pathological tau spread in animal models. Neuroimaging studies have captured coherent oscillations between neural slow waves, blood flow, and cerebrospinal fluid pulses during sleep — a physiological symphony that appears to choreograph the nightly brainwash. Obstructive sleep apnea, by disrupting the respiratory pressure gradients that help drive glymphatic flow, is associated with impaired clearance and accelerated dementia progression.

Neuroinflammation adds a vicious dimension to the story. When glymphatic clearance falters, pro-inflammatory cytokines accumulate in the brain, triggering overactivation of microglia, the brain’s resident immune cells. Activated microglia then release inflammatory mediators that further disrupt fluid transport, creating a self-amplifying loop. Meanwhile, perivascular macrophages that normally clear inflammatory debris from the drainage channels become overwhelmed, and astrocyte dysfunction compounds the problem. Periodontal infection by Porphyromonas gingivalis — increasingly recognized as an Alzheimer’s risk factor — may initiate this cascade by disturbing microglial circadian rhythms and sabotaging sleep-dependent clearance.

Translating these findings into therapies is now an intense research focus. On the pharmacological front, omega-3 polyunsaturated fatty acids accelerate amyloid clearance through aquaporin-4-dependent mechanisms, while the botanical extract L-3-n-butylphthalide enhances vascular pulsation to boost perivascular drainage. Noninvasive neuromodulation has produced striking preclinical results: 40-hertz gamma sensory stimulation promotes glymphatic amyloid clearance through vasoactive intestinal peptide neurons, repetitive transcranial magnetic stimulation restores aquaporin-4 polarization in Alzheimer’s mice, and 40-hertz transcranial vibration synchronizes human brain activity with cerebrospinal fluid flow. Focused ultrasound combined with microbubbles enhances soluble amyloid removal to cerebrospinal fluid and cervical lymph nodes, potentially synergizing with anti-amyloid antibodies.

The most provocative — and controversial — intervention is surgical. Deep cervical lymphatic-venous anastomosis, pioneered by Chinese microsurgeons, creates a bypass connecting neck lymphatic vessels directly to veins, theoretically relieving pressure in the cerebral waste drainage system. Performed through two small neck incisions, the procedure has reportedly improved cognition in preliminary cases, including an 84-year-old patient whose symptoms improved postoperatively. However, the review’s authors stress that evidence remains limited to isolated case reports without large controlled trials. Critical questions persist: which Alzheimer’s subgroups benefit, whether the surgery addresses underlying amyloid pathology or merely symptoms, and how to distinguish Alzheimer’s from idiopathic normal pressure hydrocephalus, a condition with overlapping pathology that complicates diagnosis.

The standard anti-amyloid drugs tell their own cautionary tale. Lecanemab and donanemab can reduce brain amyloid but carry risks of brain swelling and bleeding, particularly in APOE ε4 carriers, and their cognitive benefits remain modest. Anti-tau antibodies have fared worse, failing across multiple phase 2 trials. Against this backdrop, glymphatic-targeted strategies offer a fundamentally different logic: rather than attacking proteins directly, they aim to restore the brain’s intrinsic capacity to clear them. The review’s authors argue that this multi-target approach — addressing microcirculation, sleep dysfunction, and waste clearance simultaneously — matches the holistic intervention philosophy that neurodegenerative disease may ultimately demand. But they caution that the field remains in its early translational stage, with the molecular details of glymphatic dysfunction incompletely mapped and most candidate agents lacking specificity. Rigorous large-cohort clinical trials, standardized imaging assessment, and careful patient stratification will determine whether the brain’s drainage system can deliver on its extraordinary promise.

Subject of Research: The role of the glymphatic system and meningeal lymphatic vessels in Alzheimer's disease pathogenesis and therapy

Article Title: Novel Therapeutic Insights Into Alzheimer's Disease: Glymphatic System and Meningeal Lymphatic Vessels

Article References: Song, B., Wang, W., Liu, S., Jin, X., Qi, Y., Li, M., Yue, D., Liu, Y., Li, X., Yin, L., & Feng, L. (2026). Novel Therapeutic Insights Into Alzheimer's Disease: Glymphatic System and Meningeal Lymphatic Vessels. Aging Cell, 25(9), Article e70699. https://doi.org/10.1111/acel.70699

Image Credits: AI Generated

DOI: 10.1111/acel.70699

Keywords: Alzheimer's disease, glymphatic system, meningeal lymphatic vessels, aquaporin-4, amyloid-beta, tau protein, sleep, neuroinflammation, cerebrospinal fluid, deep cervical lymphaticovenous anastomosis, brain waste clearance, neurodegeneration