The collagen microstructural changes of rat menisci and tibiofemoral cartilages under the influence of mechanical loading: An in vitro wear test of whole joints

Abstract

Abstract. BACKGROUND: Knee osteoarthritis (OA) is suggested to be induced by multi-factors, and mechanical environment is regarded as a risky factor. OBJECTIVE: To investigate the effect of isolated mechanical factor on cartilage. METHODS: An active wear test system was designed to perform parameters-controlled in vitro wear tests on rat knee joints with specific load magnitude, flexion-extension angle, and movement frequency. Six hind limbs of 9-month-old male SpragueDawley rats, with an additional spring on the medial side, were worn by using the custom-designed apparatus. Researchers observed both the menisci and tibial cartilages of these hind limbs using multiphoton laser scanning microscopy to analyze the change of the collagen microstructure caused by wear. RESULTS: Collagen microstructure of both the medial and lateral meniscus became disordered under cyclic load. Some tissues on the surface of the medial tibial cartilage were removed and the middle layer of the medial compartment displayed cracks. On the contrary, the lateral tibial cartilage was intact. CONCLUSIONS: The results implied that cyclic load caused menisci microstructure disarrangement prior to tibial cartilage damage and the collagen structure of mid-layer tibial cartilage failed before that of the superficial layer under the kinematics adopted in the study.

Maturation of the Meniscal Collagen Structure Revealed by Polarization-Resolved and Directional Second Harmonic Generation Microscopy

“…SHG microscopy has revealed a variety of meniscal structural features including: the fiber bundle organization 24 , the arborization of the tie-fibers 5 and the interaction of primary cilia with the ECM 25 in healthy menisci. The effect of degradation on ECM density and cell accumulation 26 , of cyclic loading 27 and the meniscal integrity following repair 20 have also been imaged by SHG microscopy. Furthermore large images of the whole joint (cartilage and meniscus) were imaged by multiphoton fluorescence and SHG 28 , and even in-vivo and minimally processed joints using SHG microendoscopy 29 .…”