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).
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).
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).