Objective—To assess different components of the
extracellular matrix with regard to their thermal properties,
composition, and turnover in ruptured cranial
cruciate ligaments (CCLs) of dogs, compared with
components of intact CCLs from a breed predisposed
to CCL failure.
Sample Population—Ruptured CCLs obtained from
8 dogs of breeds predisposed to ruptured CCLs and
intact CCLs from 12 cadaveric Labrador Retrievers.
Procedure—Ruptured and intact CCLs were analyzed
for water content; collagen content and collagen
cross-links were evaluated via hydroxyproline and
amino-acid analyses, respectively. Glycosaminoglycan
(GAG) content was analyzed via dimethylmethylene
blue and uronic acid assays. Matrix metalloproteinases
(MMPs)-2 and -9 and the tissue inhibitors of metalloproteinases
(TIMPs)-1 and -2 were detected via
gelatin SDS-PAGE zymography and reverse gelatin
zymography. Thermal analysis of ligaments was performed
by use of differential scanning calorimetry.
Results—Ruptured CCLs had significantly higher lamounts
of immature cross-links, total and sulfated GAGs,
and water content, compared with that of the intact ligaments.
Compared with intact CCLs, concentration of
pro–MMP-2 was significantly higher in ruptured CCLs;
the maximum temperature of collagen denaturation
was significantly lower in the ruptured CCLs.
Conclusions and Clinical Relevance—The extracellular
matrix of ruptured CCLs had an increased matrix
turnover indicated by increased collagen and GAG synthesis,
compared with that of intact CCLs. Although
the extracellular matrix changes may have occurred
before ligament rupture, it is possible that these
observed changes may be part of a reparative process
after rupture. (Am J Vet Res 2004;65:1136–1141)