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Proceedings Paper

Polarization-dependent responses of fluorescent indicators partitioned into myelinated axons
Author(s): Ileana Micu; Craig Brideau; Peter K. Stys
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Paper Abstract

Myelination, i.e. the wrapping of axons in multiple layers of lipid-rich membrane, is a unique phenomenon in the nervous systems of both vertebrates and invertebrates, that greatly increases the speed and efficiency of signal transmission. In turn, disruption of axo-myelinic integrity underlies disability in numerous clinical disorders. The dependence of myelin physiology on nanometric organization of its lamellae makes it difficult to accurately study this structure in the living state. We expected that fluorescent probes might become highly oriented when partitioned into the myelin sheath, and in turn, this anisotropy could be interrogated by controlling the polarization state of the exciting laser field used for 2-photon excited fluorescence (TPEF). Live ex vivo myelinated rodent axons were labeled with a series of lipohilic and hydrophilic fluorescenct probes, and TPEF images acquired while laser polarization was varied at the sample over a broad range of ellipticities and orientations of the major angle [see Brideau, Micu & Stys, abstract this meeting]. We found that most probes exhibited strong dependence on both the major angle of polarization, and perhaps more surprisingly, on ellipticity as well. Lipophilic vs. hydrophilic probes exhibited distinctly different behavior. We propose that polarization-dependent TPEF microscopy represents a powerful tool for probing the nanostructural architecture of both myelin and axonal cytoskeleton in a domain far below the resolution limit of visible light microscopy. By selecting probes with different sizes and physicochemical properties, distinct aspects of cellular nanoarchitecture can be accurately interrogated in real-time in living tissue.

Paper Details

Date Published: 9 February 2012
PDF: 8 pages
Proc. SPIE 8207, Photonic Therapeutics and Diagnostics VIII, 82076C (9 February 2012); doi: 10.1117/12.908976
Show Author Affiliations
Ileana Micu, Univ. of Calgary (Canada)
Craig Brideau, Univ. of Calgary (Canada)
Peter K. Stys, Univ. of Calgary (Canada)

Published in SPIE Proceedings Vol. 8207:
Photonic Therapeutics and Diagnostics VIII
Anita Mahadevan-Jansen; Andreas Mandelis; Kenton W. Gregory; Nikiforos Kollias; Hyun Wook Kang; Henry Hirschberg; Melissa J. Suter; Brian Jet-Fei Wong; Justus F. Ilgner; Stephen Lam; Bodo E. Knudsen; Steen Madsen; E. Duco Jansen; Bernard Choi; Guillermo J. Tearney; Laura Marcu; Haishan Zeng; Matthew Brenner; Krzysztof Izdebski, Editor(s)

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