Effects of enzymatic treatments on the depth-dependent viscoelastic shear properties of articular cartilage

Abstract

Osteoarthritis (OA) is a disease that involves the erosion and structural weakening of articular cartilage. OA is characterized by the degradation of collagen and proteoglycans in the extracellular matrix (ECM), particularly at the articular surface by proteinases including matrix metalloproteinases (MMPs) and a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTSs).1 Degradation of collagen and proteoglycans is known to alter shear mechanical properties of cartilage, but study of this phenomenon has been focused on bulk tissue properties. The purpose of this study was to assess microscale cartilage damage induced by trypsin or collagenase using a technique to measure the local shear viscoelastic properties. Safranin-O histology revealed a decrease in proteoglycans near the articular surface after collagenase and trypsin digestions, with proteoglycan depletion increasing in time. Similarly, confocal reflectance micrographs showed increasing collagen degradation in collagenase treated samples, although the collagen network remained intact after trypsin treatment. Both treatments induced changes in shear modulus that were confined to a narrow range ($400mm) near tissue surface. In addition, collagenase altered the total energy dissipation distribution by up to a factor of 100, with longer digestion times corresponding to higher energy dissipation. The ability to detect local mechanical signatures in tissue composition and mechanics is an important tool for understanding the spatially non-uniform changes that occur in articular cartilage diseases such as OA. ß

Multi‐parametric MRI characterization of enzymatically degraded articular cartilage

“…However, as it still permits detection of significant differences with various MRI parameters, it provides a model of changes possibly comparable to relatively early changes in OA and is thus relevant despite the modest changes observed. This highlights the importance of spatial analysis of cartilage properties and the importance of spatial reference methods . Another factor potentially affecting the observed differences is that the samples in the different groups were adjacent tissue, and may slightly differ due to natural biological variation.…”

Trypsin Pre‐Treatment Combined With Growth Factor Functionalized Self‐Assembling Peptide Hydrogel Improves Cartilage Repair in Rabbit Model

“…Recently, our group demonstrated that enzymatic pre‐treatment of cartilage explants with trypsin for 2 min were able to promote proteoglycan depletion extending from the center of the cartilage annuli in about 200 μm thick, dramatically influencing cellular migration and promoting better cartilage horizontal integration in an in vitro model . Trypsin enzymatic pre‐treatment of the cartilage results in proteoglycan depletion in a time‐dependent manner, not affecting collagen network and results in increased cell volume and total proteoglycan deposition on partial‐thickness cartilage defects in rabbits . Furthermore, chondrocyte proliferation was shown to increase post‐intra‐articular injection of trypsin in rabbits …”

Osteoarthritis year in review 2015: mechanics

“…In a related sets of experiments, Griffin et al . 31 examined the effects of collagenase and trypsin treatments on microscale changes in the shear modulus of cartilage plugs. Confocal reflectance micrographs revealed increasing collagen degradation caused by collagenase, but not by trypsin, but both treatments caused GAG loss, decreases in the dynamic (viscoelastic) shear modulus, and increased energy dissipation confined to the upper 400 μm of SZ tissue, as assessed by confocal strain mapping.…”