Effects of Articular Cartilage Constituents on Phosphotungstic Acid Enhanced Micro-Computed Tomography.

Sakari S Karhula,Heikki J Nieminen,Janne H Ylärinne,Mikko J Lammi,Simo Saarakkala,Kenneth P H Pritzker,Mikko A Finnilä,Lassi Rieppo,Sami Kauppinen,Lin Han

doi:10.1371/journal.pone.0171075

Abstract

Contrast-enhanced micro-computed tomography (CEμCT) with phosphotungstic acid (PTA) has shown potential for detecting collagen distribution of articular cartilage. However, the selectivity of the PTA staining to articular cartilage constituents remains to be elucidated. The aim of this study was to investigate the dependence of PTA for the collagen content in bovine articular cartilage. Adjacent bovine articular cartilage samples were treated with chondroitinase ABC and collagenase to degrade the proteoglycan and the collagen constituents in articular cartilage, respectively. Enzymatically degraded samples were compared to the untreated samples using CEμCT and reference methods, such as Fourier-transform infrared imaging. Decrease in the X-ray attenuation of PTA in articular cartilage and collagen content was observed in cartilage depth of 0–13% and deeper in tissue after collagen degradation. Increase in the X-ray attenuation of PTA was observed in the cartilage depth of 13–39% after proteoglycan degradation. The X-ray attenuation of PTA-labelled articular cartilage in CEμCT is associated mainly with collagen content but the proteoglycans have a minor effect on the X-ray attenuation of the PTA-labelled articular cartilage. In conclusion, the PTA labeling provides a feasible CEμCT method for 3D characterization of articular cartilage.

Highlights

Composition of articular cartilage (AC) is known to be strongly associated with its biomechanical properties [1]
We reported the potential of CEμCT method for analyzing the 3D collagen distribution in AC by using phosphotungstic acid (PTA) as the contrast agent [4]
The results of this study suggest that PTA distribution mainly coincides with the collagen content in the superficial AC and relies on the balance dictated by the electric attraction forces of collagen and repulsion forces of the PGs within AC

Summary

Introduction

Composition of articular cartilage (AC) is known to be strongly associated with its biomechanical properties [1]. Main constituents in AC are proteoglycans (PG), collagens and chondrocytes. Osteoarthritis (OA) progression leads to loss of PG content, degeneration of collagen. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

Objectives

Methods

Results

Conclusion