Inferior mechanical properties of spastic muscle bundles due to hypertrophic but compromised extracellular matrix material

Richard L. Lieber*, Eva Runesson, Fredrik Einarsson, Jan Fridén

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

150 Scopus citations

Abstract

The passive mechanical properties of small muscle fiber bundles obtained from surgical patients with spasticity (n = 9) and patients without neuromuscular disorders (n = 21) were measured in order to determine the relative influence of intracellular and extracellular components. For both types of patient, tangent modulus was significantly greater in bundles compared to identical tests performed on isolated single cells (P < 0.05). However, the relative difference between bundles and single cells was much greater in normal tissue than spastic tissue. The tangent modulus of normal bundles (462.5 ± 99.6 MPa) was 16 times greater than normal single cells (28.2 ± 3.3 MPa), whereas the tangent modulus of spastic bundles (111.2 ± 35.5 MPa) was only twice that of spastic muscle cells (55.0 ± 6.6 MPa). This relatively small influence of the extracellular matrix (ECM) in spastic muscle was even more surprising because spastic muscle cells occupied a significantly smaller fraction of the total specimen area (38.5 ± 13.6%) compared to normal muscle (95.0 ± 8.8%). Based on these data, normal muscle ECM is calculated to have a modulus of 8.7 GPa, and the ECM from spastic muscle of only 0.20 GPa. These data indicate that spastic muscle, although composed of cells that are stiffer compared to normal muscle, contains an ECM of inferior mechanical strength. The present findings illustrate some of the profound changes that occur in skeletal muscle secondary to spasticity. The surgical implications of these results are discussed.

Original languageEnglish (US)
Pages (from-to)464-471
Number of pages8
JournalMuscle and Nerve
Volume28
Issue number4
DOIs
StatePublished - Oct 1 2003

Keywords

  • Biomechanics
  • Collagen
  • Elasticity
  • Extracellular matrix
  • Sarcomere length
  • Spasticity

ASJC Scopus subject areas

  • Physiology
  • Clinical Neurology
  • Cellular and Molecular Neuroscience
  • Physiology (medical)

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