Review Evidence for cellular and solute passage between the brain and skull bone marrow across meninges: A systematic review, 2025, Therkelsen et al.

[SNT Gatchaman]

Evidence for cellular and solute passage between the brain and skull bone marrow across meninges: A systematic review
Helena Eide Therkelsen; Rune Enger; Per Kristian Eide; Geir Ringstad

A potential two-way passage of cells and substances between the brain and skull bone marrow may open for new insights into neurological disease. The arachnoid membrane was traditionally considered to restrict cells and larger molecules in CSF from entering the dura and bone marrow directly. However, new data on exchange between brain and skull bone marrow have recently emerged.

Here, we conducted a systematic literature to answer the question: What is the current evidence regarding the movement of cells and molecules between the brain and skull bone marrow, spanning CSF and meninges? We excluded studies related to head or skull trauma, cranial fractures or defects, cancer invasion, CSF leakage, spontaneous intracranial hypotension, spinal dura mater, and studies solely focusing on meningeal lymphatic vessels or the passage of substances from CSF to meningeal lymphatic vessels.

The review identified 16 studies that provide evidence of communication between the brain, meninges and skull bone marrow. Cells (such as B and T cells and neutrophils), bacteria, and substances (tracers, drug compounds) have been reported to pass between the brain and skull bone. However, most studies are performed in rodents, emphasizing the need for translation to humans.

Link | PDF (Journal of Cerebral Blood Flow & Metabolism)

 

[SNT Gatchaman]

Concluding —

From the present literature review, a picture emerges that the brain borders, including the meninges and skull bone marrow, play an essential role in both immune surveillance and waste clearance. Instead of being regarded as separate anatomical entities, the CNS-meninges-skull organ-system should rather be viewed as an anatomical and functional continuum.

Taken together, emerging evidence from the last decade has demonstrated existence of vascular bone channels extending from the skull bone marrow to the dura mater. These channels may host vessels that bridge the previously considered impermeable barriers, including meninges, between the brain, subarachnoid space and the skull bone marrow. Recent research has revealed the existence of cuffs or openings around bridging veins, facilitating the passage of even large mass substances from the subarachnoid space to the dura mater. Current evidence suggests that the transport route occurs along the vessel (abluminal), specifically at the basement membrane, where the molecular composition is crucial. This emphasizes the significant role of the abundant expression of laminin within the basement membrane and its interactions with a6 integrin. While several questions persist, the brain meninges now emerge as a specialized structure with distinct functions, particularly in waste clearance and central nervous system (CNS) immunosurveillance.

 

[Jonathan Edwards]

The things you are liable to read in the 'scientific literature'
Ain't necessarily so.