Composition, structure and tensile biomechanical properties of equine articular cartilage during growth and maturation

J Oinas,R K Korhonen,H J Helminen,L Rieppo,S Saarakkala,J T Iivarinen,A P Ronkainen,P A J Brama,M A J Finnilä,P R Van Weeren

doi:10.1038/s41598-018-29655-5

Abstract

Articular cartilage undergoes structural and biochemical changes during maturation, but the knowledge on how these changes relate to articular cartilage function at different stages of maturation is lacking. Equine articular cartilage samples of four different maturation levels (newborn, 5-month-old, 11-month-old and adult) were collected (N = 25). Biomechanical tensile testing, Fourier transform infrared microspectroscopy (FTIR-MS) and polarized light microscopy were used to study the tensile, biochemical and structural properties of articular cartilage, respectively. The tensile modulus was highest and the breaking energy lowest in the newborn group. The collagen and the proteoglycan contents increased with age. The collagen orientation developed with age into an arcade-like orientation. The collagen content, proteoglycan content, and collagen orientation were important predictors of the tensile modulus (p < 0.05 in multivariable regression) and correlated significantly also with the breaking energy (p < 0.05 in multivariable regression). Partial least squares regression analysis of FTIR-MS data provided accurate predictions for the tensile modulus (r = 0.79) and the breaking energy (r = 0.65). To conclude, the composition and structure of equine articular cartilage undergoes changes with depth that alter functional properties during maturation, with the typical properties of mature tissue reached at the age of 5–11 months.

Highlights

Articular cartilage (AC) is a specialized connective tissue covering the ends of articulating bones within the joints
Fourier transform infrared microspectroscopy (FTIR-MS) and polarized light microscopy (PLM) were used to study the relationship between the composition, structure and tensile biomechanical properties of equine AC at multiple depths and different stages of growth and maturation
Significant structural and compositional changes in AC occurred during maturation, and these changes were related to the tensile biomechanical properties

Summary

Introduction

Articular cartilage (AC) is a specialized connective tissue covering the ends of articulating bones within the joints. The tensile biomechanical properties of AC are provided by the specific structure of the collagen fibril network and the biochemical composition of the tissue[9,10,11]. The variations in AC tensile biomechanical properties can be attributed to the orientation of the collagen fibrils and differences in the amount and spatial distribution of macromolecules, such as collagen and PGs12. The relationship between the tissue composition, collagen fibril network arrangement, and tensile properties can be very complex in different phases of tissue maturation. The second aim of the study was to determine the relationships between the AC composition, arrangement of the collagen network, and tensile biomechanical properties. We hypothesized that during maturation, arrangement of the collagen network and the collagen content of the AC affect profoundly its tensile biomechanical properties

Objectives

Methods

Results

Conclusion