Interest of second harmonic generation imaging for diagnosis in thick and opaque tissue

Issue title: Selected papers of the 5th International Symposium on Mechanobiology of Cartilage and Chondrocyte, Athens, May 2007

Article type: Research Article

Authors: Werkmeister, E.^; | de Isla, N. | Marchal, L. | Stoltz, J.F.^; | Dumas, D.

Affiliations: CNRS – Groupe d'Ingénierie Cellulaire et Tissulaire, Faculté de Médecine, Nancy-Université – UHP, UMR 7563, 54 505 Vandoeuvre-lès-Nancy, France | Unité de Thérapie Cellulaire et Tissulaire – Brabois, CHU Nancy, 54 500 Vandoeuvre-lès-Nancy, France

Note: [] Address for correspondence: E. Werkmeister, Groupe d'Ingénierie Cellulaire et Tissulaire, Faculté de Médecine, Nancy-Université, UHP, 9, Avenue de la Forêt de Haye, 54505 Vandoeuvre-lès-Nancy, France. Tel.: +33 3 83 68 34 58; Fax: + 33 3 83 68 34 59; E-mail: [email protected].

Abstract: In articular hyaline cartilage, chondrocytes are surrounded by an extracellular matrix which is mainly composed by collagen and proteoglycanes. Pathological specimens show a partial or complete degradation of this matrix. Therefore, it could be interesting to know how mechanical or biochemical constraints applied to cartilage specimens induce modifications of the cartilage network. Multiphoton technology combined to Second Harmonic Generation (SHG) enables to image cartilage specimens in a non-invasive mode with high resolution at deep penetration. By placing a band pass filter in front of the transmitted light detector, SHG signal with frequency doubled can be isolated for a new contrast imaging. SHG (second harmonic generation) is a diffusion process generated from organized structures and does not need any fluorescent staining. Due to their non-centrosymetric structure, collagen fibrilles present a high second-order non-linear susceptibility and thus give rise to a strong SHG signal when exposed to high enough electric fields produced by a focal point of a femtosecond pulsed laser (multiphoton microscopy). As the extracellular matrix of cartilage is in part constituted by collagen fibers, it can be imaged with this contrast tool. The intensity of SHG signals strongly depends on the organization of collagen fibers. Thus a modification of the extracellular matrix in terms of 3D-organization of collagen induced by mechanical stress can be shown with this contrast tool.

Keywords: Multiphoton microscopy, second harmonic generation, collagen, extracellular matrix

DOI: 10.3233/BIR-2008-0483

Journal: Biorheology, vol. 45, no. 3-4, pp. 375-383, 2008