Structure–function relationship is altered with aging and degeneration in the human meniscus

Abstract-Text (inkl. Referenzen und Bildunterschriften)

Introduction: The elastic and viscoelastic properties of degenerated menisci may change before alterations are detectable in the adjacent articular cartilage1.

Aim: The aim of this study was to identify changes in the structure-function relationship of lateral and medial menisci during aging/degeneration.

Materials & Methods: Twelve mildly (age: 47±11) and 12 severely (age: 82±9) degenerated human medial and lateral menisci were investigated (Fig. 1A). Confined stress-relaxation tests were performed to assess permeability (k) and equilibrium modulus (Eeq), and tensile tests to determine Young"s modulus (E) and failure load (Fmax). DNA, glycosaminoglycan (GAG) and collagen were quantified. Collagen type I (COL1), COL2 and aggrecan (ACAN) were analyzed by immunohistochemistry in different meniscus regions (Fig. 1A,B). Statistics: Kruskal-Wallis test (significance, p<0.05).

Results: Eeq increased with degeneration (p<0.05, Fig. 2A), without affecting k (p>0.76, Fig. 2B). The tensile properties were not altered with degeneration (p>0.16). While GAG increased, collagen decreased with degeneration, both in lateral (p<0.05) and medial (p=0.06) menisci. A progressive destruction of the collagen structure was observed without significantly affecting COL1 or COL2 (p>0.20, Fig. 1C,D). ACAN increased with degeneration, particularly in lateral menisci (p<0.05, Fig. 1E) and in the white-white zone (zone 1, p<0.05, Fig. 1F).

Discussion: This work indicates that structural changes may be detectable at protein level before biomechanical alterations can be observed. The increase in Eeq may be explained by a disturbed relationship in the biphasic meniscus structure possibly resulting from an increase in GAG. This data can be used to validate in silico determination of meniscus material parameters, with special focus on the early detection of osteoarthritis. References: 1. Seitz et al., 2021. Acknowledgements: DFG (AS3135/2-1), ON Foundation (21-340).