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BioMed Research International
Volume 2015, Article ID 859084, 9 pages
http://dx.doi.org/10.1155/2015/859084
Research Article

Endogenous Two-Photon Excited Fluorescence Provides Label-Free Visualization of the Inflammatory Response in the Rodent Spinal Cord

1Neurosurgery, Carl Gustav Carus University Hospital, TU Dresden, Fetscherstraße 74, 01307 Dresden, Germany
2Clinical Sensoring and Monitoring, Anesthesiology and Intensive Care Medicine, Carl Gustav Carus University Hospital, TU Dresden, Fetscherstraße 74, 01307 Dresden, Germany
3Centre for Translational Bone, Joint and Soft Tissue Research, Carl Gustav Carus University Hospital, TU Dresden, Fetscherstraße 74, 01307 Dresden, Germany
4Department of Clinical Pathobiochemistry, Carl Gustav Carus University Hospital, TU Dresden, Fetscherstraße 74, 01307 Dresden, Germany
5Center for Regenerative Therapies Dresden (CRTD), TU Dresden, Fetscherstrasse 105, 01307 Dresden, Germany

Received 20 March 2015; Revised 19 July 2015; Accepted 27 July 2015

Academic Editor: Marija Mostarica-Stojković

Copyright © 2015 Ortrud Uckermann et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Activation of CNS resident microglia and invasion of external macrophages plays a central role in spinal cord injuries and diseases. Multiphoton microscopy based on intrinsic tissue properties offers the possibility of label-free imaging and has the potential to be applied in vivo. In this work, we analyzed cellular structures displaying endogenous two-photon excited fluorescence (TPEF) in the pathologic spinal cord. It was compared qualitatively and quantitatively to Iba1 and CD68 immunohistochemical staining in two models: rat spinal cord injury and mouse encephalomyelitis. The extent of tissue damage was retrieved by coherent anti-Stokes Raman scattering (CARS) and second harmonic generation imaging. The pattern of CD68-positive cells representing postinjury activated microglia/macrophages was colocalized to the TPEF signal. Iba1-positive microglia were found in areas lacking any TPEF signal. In peripheral areas of inflammation, we found similar numbers of CD68-positive microglia/macrophages and TPEF-positive structures while the number of Iba1-positive cells was significantly higher. Therefore, we conclude that multiphoton imaging of unstained spinal cord tissue enables retrieving the extent of microglia activation by acquisition of endogenous TPEF. Future application of this technique in vivo will enable monitoring inflammatory responses of the nervous system allowing new insights into degenerative and regenerative processes.