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Proceedings of the British Pharmacological Society at http://www.pA2online.org/abstracts/Vol7Issue4abst148P.pdf
Human cerebrospinal fluid contains exosomes that represent a novel reservoir for
therapeutic biomarker discovery
J.M. Street1, R.T.A. Chalmers2, T.S. Walsh2, D.J. Webb1, J.W. Dear1. 1University of Edinburgh,
Edinburgh, United Kingdom, 2Royal Infirmary of Edinburgh, Edinburgh, United Kingdom.
One of the pathological hallmarks of neurodegenerative diseases, such as spongiform
encephalopathies (TSEs) and Alzheimer's dementia (AD), is the accumulation of abnormal
proteins within brain tissue (prions in TSEs and b-amyloid in AD). Studies in cell culture have
demonstrated these proteins are released from cells within lipid vesicles termed exosomes [1].
In vitro, the exosomal protein content changes with drug therapy, which suggests that
exosomes could represent a reservoir for therapeutic biomarker discovery. Our aim was to
determine if exosomes are present in human cerebrospinal fluid (CSF). CSF was collected from
patients undergoing thoraco-abdominal aortic aneurysm repair (with full ethical approval). This
group was chosen as they have a CSF drain inserted peri-operatively as part of routine clinical
management. The CSF was ultracentrifuged (as per established protocols for urinary exosome
isolation [2]) and the presence of exosomes was tested by western blotting for specific markers,
sucrose gradient centrifugation, immunoelectron microscopy and the proteome was explored by
tandem mass spectrometry. The exosomal markers TSG101 and Flotillin-1 were found to be
enriched in the ultracentrifugation pellet over the unfractionated CSF. Using sucrose gradient
-3
centrifugation, the density of the 'microvesicles' was established as 1.14 - 1.20 g.cm ,
consistent with the density previously reported for exosomes (see figure). Staining for Flotillin-1
during electron microscopy revealed the presence of Flotillin-1 on structures consistent in size
and shape with previous reports for exosomes. Alpha-2-macroglobulin, which is involved in the
clearance of A-beta, and filamin-A, which is linked to periventricular heterotopia, were identified
in the exosomes by tandem mass spectrometry. Based on this evidence, we conclude that
human CSF contains exosomes. The existence of exosomes provides a source for new
diagnostic and therapeutic biomarkers and proteomic discovery studies are ongoing.
1. Faure J et al. Molecular and cellular neurosciences 2006; 31: 642-8.
2. Pisitkun T et al. Proceedings of the National Academy of Sciences 2004; 101: 13368-73.