Quantitative SHG imaging in osteoarthritis model mice, implying a diagnostic application

Abstract

Osteoarthritis (OA) restricts the daily activities of patients and significantly decreases their quality of life. The development of noninvasive quantitative methods for properly diagnosing and evaluating the process of degeneration of articular cartilage due to OA is essential. Second harmonic generation (SHG) imaging enables the observation of collagen fibrils in live tissues or organs without staining. In the present study, we employed SHG imaging of the articular cartilage in OA model mice ex vivo. Consequently, three-dimensional SHG imaging with successive image processing and statistical analyses allowed us to successfully characterize histopathological changes in the articular cartilage consistently confirmed on histological analyses. The quantitative SHG imaging technique presented in this study constitutes a diagnostic application of this technology in the setting of OA.

Nonlinear optical microscopy of early stage (ICRS Grade-I) osteoarthritic human cartilage

“…Brown et al, has investigated collagen meshwork architecture by a two-dimensional spring-mass network model in bovine high grade osteoarthritic cartilage [13]. Kiyomatsu et al, presented a quantitative approach to characterize induced OA in a mice model [14]. Additionally, a few other reports use NLOM to study degenerative cartilage, but the analysis is rudimentary [15][16][17].…”

Collagen Organization Within the Cartilage of Trpv4−/− Mice Studied with Two‐Photon Microscopy and Polarized Second Harmonic Generation

“…In order to determine whether cartilage is malformed when TRPV4 is absent during development, our study was conducted using a label‐free imaging technique based on the measurement of the SHG signal under two‐photon excitation. The structure of the osteoarthritic cartilage has been investigated before using SHG, but data were obtained on cartilage samples subjected to mechanical load, either after surgical induction of OA in mice or from patients undergoing knee surgery for OA . Our present contribution aims to correlate the structural modifications of the cartilage matrix with molecular mechanisms affecting the chondrocytes (i.e., reduction of Ca 2+ transients due to the absence of the TRPV4 channels) at a time point post‐cartilage development but before the tissue has been subjected to ongoing mechanical loads, that is, in pups at P4–5.…”

“…We propose that significant differences with the WT mice could not be observed in the orientation of collagen fibers because at this stage of development, the mechanical load on the articular cartilage is minimal and compensatory mechanisms take place. Indeed, substantial modifications of the structure of the osteoarthritic cartilage have been observed 8 weeks after the surgical induction of OA in mice or in human samples where the advanced stage of OA progression required surgical replacement of the joint .…”

Assessment of Articular Cartilage by Second Harmonic Microscopy: Challenges and Opportunities

“…However, due to lack of early feature visibility (e.g., structural alterations in collagen fiber and changes in its integrity, fibrillation, chondrocyte cloning and death, micro-cracks and wrinkle-like pattern on articular surface etc. ), the problems such as identification of accurate size of cartilage-lesions and estimation for severity of lesions remain persistent even when cartilage evaluation is performed using an arthroscope [9][10][11][12][13]. In addition, inter-observer variations raise a question mark regarding its reliability, which indicates the need for specialized clinical professionals.…”