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A dural lymphatic vascular system that drains brain interstitial fluid and macromolecules.

Aspelund A, Antila S, Proulx ST, Karlsen TV, Karaman S, Detmar M, Wiig H, Alitalo K - J. Exp. Med. (2015)

Bottom Line: Surprisingly, brain ISF pressure and water content were unaffected.Overall, these findings indicate that the mechanism of CSF flow into the dcLNs is directly via an adjacent dural lymphatic network, which may be important for the clearance of macromolecules from the brain.Importantly, these results call for a reexamination of the role of the lymphatic system in CNS physiology and disease.

View Article: PubMed Central - HTML - PubMed

Affiliation: Wihuri Research Institute and Translational Cancer Biology Program, Biomedicum Helsinki, University of Helsinki, 00014 Helsinki, Finland Wihuri Research Institute and Translational Cancer Biology Program, Biomedicum Helsinki, University of Helsinki, 00014 Helsinki, Finland.

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Lack of dural lymphatic vasculature inhibits CSF uptake into the dcLNs. (A) Schematic illustration of the experimental setup. (B) Representative fluorescent images of the dcLN in TG and WT mice 30 min after PEG-IRDye injection into the cisterna magna. AF, green channel autofluorescence. Bar, 1,000 µm. (C) Quantification of the dcLN fluorescence. n = 6 (TG) and 5 (WT). Data are representative of two independent experiments. Error bars indicate SD. Statistical analysis: two-tailed Student’s t test. *, P < 0.05.
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fig5: Lack of dural lymphatic vasculature inhibits CSF uptake into the dcLNs. (A) Schematic illustration of the experimental setup. (B) Representative fluorescent images of the dcLN in TG and WT mice 30 min after PEG-IRDye injection into the cisterna magna. AF, green channel autofluorescence. Bar, 1,000 µm. (C) Quantification of the dcLN fluorescence. n = 6 (TG) and 5 (WT). Data are representative of two independent experiments. Error bars indicate SD. Statistical analysis: two-tailed Student’s t test. *, P < 0.05.

Mentions: Second, we hypothesized that the absence of dura mater lymphatic vessels may impair macromolecule clearance from the brain. To test this, we studied the cerebral clearance of Alexa Fluor 488–conjugated OVA (A488-OVA, ∼45 kD), a macromolecule which retains fluorescent signal during fixation. We recorded cerebral, dcLN, and dura mater lymphatic vessel fluorescence from tissues 2 h after injection into the brain parenchyma of TG and WT littermate mice. Mice were perfusion fixed after sacrifice to prevent outflow of the tracer. Interestingly, the TG mice displayed a significant reduction in the amount of OVA cleared at the 2-h time point after injection (Fig. 4, A and B). Furthermore, a nearly complete abrogation of OVA accumulation was observed in the dcLNs of the TG mice (Fig. 4, C and D). Tracer-filled lymphatic vessels could be observed around the pterygopalatine artery and middle meningeal artery of WT mice, but this was absent in the TG mice (Fig. 4, E and F). To assess other possible causes for the drainage defect, we analyzed glymphatic function and the dcLN capacity for drainage. To this extent, the TG mice did not display qualitative defects in glymphatic function, as indicated by detectable paravascular outflow of the tracer in the subendothelial and perivascular space (Fig. 4, G and H), or a significant reduction in the amount of draining lymphatic vessels in the dcLN (Fig. 4, I and J). We also studied PEG-IRDye transfer from the subarachnoid space into the dcLNs after cisterna magna injection, which was significantly inhibited in the TG mice (Fig. 5). Overall, these data imply that the dura mater lymphatic vessels contribute to the clearance of macromolecules from the brain.


A dural lymphatic vascular system that drains brain interstitial fluid and macromolecules.

Aspelund A, Antila S, Proulx ST, Karlsen TV, Karaman S, Detmar M, Wiig H, Alitalo K - J. Exp. Med. (2015)

Lack of dural lymphatic vasculature inhibits CSF uptake into the dcLNs. (A) Schematic illustration of the experimental setup. (B) Representative fluorescent images of the dcLN in TG and WT mice 30 min after PEG-IRDye injection into the cisterna magna. AF, green channel autofluorescence. Bar, 1,000 µm. (C) Quantification of the dcLN fluorescence. n = 6 (TG) and 5 (WT). Data are representative of two independent experiments. Error bars indicate SD. Statistical analysis: two-tailed Student’s t test. *, P < 0.05.
© Copyright Policy - openaccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4493418&req=5

fig5: Lack of dural lymphatic vasculature inhibits CSF uptake into the dcLNs. (A) Schematic illustration of the experimental setup. (B) Representative fluorescent images of the dcLN in TG and WT mice 30 min after PEG-IRDye injection into the cisterna magna. AF, green channel autofluorescence. Bar, 1,000 µm. (C) Quantification of the dcLN fluorescence. n = 6 (TG) and 5 (WT). Data are representative of two independent experiments. Error bars indicate SD. Statistical analysis: two-tailed Student’s t test. *, P < 0.05.
Mentions: Second, we hypothesized that the absence of dura mater lymphatic vessels may impair macromolecule clearance from the brain. To test this, we studied the cerebral clearance of Alexa Fluor 488–conjugated OVA (A488-OVA, ∼45 kD), a macromolecule which retains fluorescent signal during fixation. We recorded cerebral, dcLN, and dura mater lymphatic vessel fluorescence from tissues 2 h after injection into the brain parenchyma of TG and WT littermate mice. Mice were perfusion fixed after sacrifice to prevent outflow of the tracer. Interestingly, the TG mice displayed a significant reduction in the amount of OVA cleared at the 2-h time point after injection (Fig. 4, A and B). Furthermore, a nearly complete abrogation of OVA accumulation was observed in the dcLNs of the TG mice (Fig. 4, C and D). Tracer-filled lymphatic vessels could be observed around the pterygopalatine artery and middle meningeal artery of WT mice, but this was absent in the TG mice (Fig. 4, E and F). To assess other possible causes for the drainage defect, we analyzed glymphatic function and the dcLN capacity for drainage. To this extent, the TG mice did not display qualitative defects in glymphatic function, as indicated by detectable paravascular outflow of the tracer in the subendothelial and perivascular space (Fig. 4, G and H), or a significant reduction in the amount of draining lymphatic vessels in the dcLN (Fig. 4, I and J). We also studied PEG-IRDye transfer from the subarachnoid space into the dcLNs after cisterna magna injection, which was significantly inhibited in the TG mice (Fig. 5). Overall, these data imply that the dura mater lymphatic vessels contribute to the clearance of macromolecules from the brain.

Bottom Line: Surprisingly, brain ISF pressure and water content were unaffected.Overall, these findings indicate that the mechanism of CSF flow into the dcLNs is directly via an adjacent dural lymphatic network, which may be important for the clearance of macromolecules from the brain.Importantly, these results call for a reexamination of the role of the lymphatic system in CNS physiology and disease.

View Article: PubMed Central - HTML - PubMed

Affiliation: Wihuri Research Institute and Translational Cancer Biology Program, Biomedicum Helsinki, University of Helsinki, 00014 Helsinki, Finland Wihuri Research Institute and Translational Cancer Biology Program, Biomedicum Helsinki, University of Helsinki, 00014 Helsinki, Finland.

Show MeSH
Related in: MedlinePlus