Among the key opportunities offered by a non-destructive imaging method is the ability to "watch" natural or experimentally-induced changes in tissue composition on a sample-by-sample basis to better understand the processes of matrix damage and repair. For example:

GAG concentration increased steadily in young bovine cartilage pre-treated with trypsin to remove tissue GAG. The recovery rate was relatively uniform throughout the tissue over the 5-8 week recovery period, and eventually the chondrocytes were largely able to recapitulate the [GAG] of the native tissue (including the natural depth variation) (Figure 1).

iatimeinclutureFigure 1:

When young bovine tissue was treated with interleukin-1 (IL-1) to impose a heterogeneous distribution of matrix damage, the pattern of recovery was somewhat different than that seen following trypsin-induced damage. During the first two weeks the rate of GAG recovery was the same throughout the tissue. By the third week, the tissue that had initially been most affected by IL-1 showed no further recovery, while the regions least affected by IL-1 were continuing to recover at the same rate seen initially (Figure 2). One hypothesis for this finding is that IL-1-induced damage to the collagen matrix in some way prevents complete GAG recovery. These results have important implications for our understanding of cartilage repair - and provide information that would have been tremendously difficult to get without non-destructive imaging. (Figure 2).

iaweeksFigure 2:

For further details on these studies, please refer to:

  • Allen RG, Burstein D, Gray ML. Monitoring Glycosaminoglycan Replenishment in Cartilage Explants with Gadolinium Enhanced MRI. J Orthop Res, 1999; 17: 430-436.
  • Williams, A. Regeneration of Cartilage Glycosaminoglycan After Degradation by Interleukin-1, January 2001 (MIT, Electrical Engineering and Computer Science).