Changes in matrix protein biochemistry

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Changes in matrix protein biochemistry and theexpression of mRNA encoding matrix proteins and metalloproteinases in posterior tibialis tendinopathy
From  Anthony N Corps,1 Andrew H N Robinson,2 Rebecca L Harrall,1 Nicholas C Avery,3Valerie A Curry,1 Brian L Hazleman,1 Graham P Riley4
ABSTRACT
Objectives Adult-acquired fl at foot secondary to a
dysfunctional posterior tibialis tendon (PTT) is often
treated by surgical transfer of the fl exor digitorum longus
tendon (FDLT). In this study, the authors compared
normal PTT, stage II dysfunctional PTT and replacement
FDLT, aiming to defi ne changes in collagen modifi cation,
glycosaminoglycan (GAG) and the expression of matrix
and metalloproteinase mRNA.
Methods Normal PTTs were obtained from patients with
no history of tendon problems. Samples of dysfunctional
PTT and replacement FDLT tissue were obtained from
patients undergoing surgical reconstruction. Tissue
samples were analysed for total collagen and GAG,
pentosidine and collagen cross-links. Total RNA was
assayed for mRNA encoding matrix proteins and
metalloproteinases, using real-time reverse transcription
PCR. Differences between clinical groups were assessed
using non-parametric statistics.
Results Dysfunctional PTT contained higher levels of
GAG and lower levels of pentosidine than normal PTT
or FDLT. In contrast, collagen in FDLT contained fewer
ketoimine and more aldimine cross-links than either
normal or dysfunctional PTT. mRNA encoding types I and
III collagens, aggrecan, biglycan, matrix metalloproteinase
(MMP)-2, -13 and -23, and a disintegrin and
metalloproteinase (ADAM)-12L each showed increased
levels in dysfunctional PTT compared with either normal
PTT or (except MMP-13) FDLT. In contrast, MMP-3 and
ADAM with thrombospondin domain (ADAMTS)-5 mRNA
were lower in both dysfunctional PTT and FDLT than
in normal PTT, while ADAMTS-1 mRNA was lower in
dysfunctional PTT than in FDLT.
Conclusions Stage II dysfunctional PTT shows
biochemical and molecular changes consistent with a
chronic remodelling of the extracellular matrix, rather than
rupture, while the replacement FDLT resembles normal
PTT in many, but not all, parameters.