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

Abstract

Abstract:In a synovial joint, the articular cartilage is directly affected during the progression of Osteoarthritis (OA). The characterization of early stage modification in extra-cellular matrix of cartilage is essential for detection as well as understanding the progression of disease. The objective of this study is to demonstrate the potential and capability of nonlinear optical microscopy for the morphological investigation of early stage osteoarthritic cartilage. ICRS Grade-I cartilage sections were obtained from the femoral condyle of the human knee. The surface of articular cartilage was imaged by second harmonic generation and two-photon excited fluorescence microscopy. Novel morphological features like microsplits and wrinkles were observed, which would otherwise not be visible in other clinical imaging modalities (e.g., CT, MRI, ultrasound and arthroscope. The presence of superficial layer with distinct collagen fibrils parallel to the articular surface in 4 specimens out of 14 specimens, indicates that different phases of OA within ICRS Grade-I can be detected by SHG microscopy. All together, the observed novel morphologies in early stage osteoarthritic cartilage indicates that SHG microscopy might be a significant tool for the assessment of cartilage disorder.

Characterization of cellular and matrix alterations in the early pathogenesis of osteochondritis dissecans in pigs using second harmonic generation and two‐photon excitation fluorescence microscopy

“…The observations were done in the entire 100 µm‐section and in adjacent thick sections and were always confined to the necrotic areas. Furthermore, almost identical ripples and microsplits were observed using SHG in osteoarthritic cartilage and a similar fissure or microcrack was revealed by SHG in cartilage upon low‐energy impact . The findings were therefore assumed to be valid and not artifacts from sample preparation.…”

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

“…In another associated study, histopathological changes in surgicallyinduced osteoarthritic cartilage were characterized by SHM followed by image analyses, demonstrating that SHM could be an ideal imaging approach for detecting pathological changes in articular cartilage [11]. Our group has demonstrated the novel features (such as microsplits and wrinkle-like patterns) in early stage osteoarthritic human cartilage, which could not otherwise be visualized by standard clinical imaging modalities [12], can be visualized using SHM. The discrimination ability of type-I and type-II collagen by p-SHM further adds to the characterization of articular cartilage, which might be advantageous for the postoperative evaluation of regenerated cartilage in the synovial-joint [26,33].…”

“…The feasibility of SHM for the assessment of articular cartilage in animals [11,28,30,56], humans [12,33], and tissue-engineered [44,48,57,58] cartilage constructs have been demonstrated several times. SHM can provide a wealth of information at several levels, including, but not limited to, micron-level surface morphology, changes in collagen architecture, detection of collagen types in regenerated cartilage, label-free analysis, and 3D imaging capability (optical biopsy) within the limit of laser penetration depth.…”

“…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.…”

“…Notably, SHM images can provide relatively improved morphological features with much higher contrast than twophoton autofluorescence images of articular cartilage [12]. Thus, an image-processing algorithm for SHM images could provide improved results for the automatic categorization of damaged cartilage.…”