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The Effect of Running Exercise on Intervertebral Disc Extracellular Matrix Production in a Rat Model

Brisby, Helena MD*; Wei, Ai Qun PhD†; Molloy, Tim PhD†; Chung, Sylvia A. MSc Hon†; Murrell, George A. MD†; Diwan, Ashish D. MD†

doi: 10.1097/BRS.0b013e3181e0f5bc
Basic Science

Study Design. Using a running rat model, the effects of physical exercise on cellular function and intervertebral disc (IVD) extracellular matrix were studied.

Objective. To investigate whether 3-weeks treadmill running exercise can stimulate matrix production and cellular proliferation of the IVD.

Summary of Background Data. Appropriate physical exercise plays an important role in the treatment of patients with low back pain-associated IVD disorder. However, it is unknown how regular exercise affects the disc at the cellular level.

Methods. Twelve Sprague-Dawley rats underwent a daily treadmill exercise regime for a total of 3 weeks. Twelve nonexercised rats served as controls. The spinal lumbar IVD were collected and paraffin embedded for histologic analysis. Cell counts were determined on hematoxylin-eosin- and Masson-Trichrome-stained paraffin sections. Protein expression of collagen-I, collagen-II, aggrecan, Sox-9, and Sox-6 was evaluated with immunohistochemical staining. mRNA expression of Sox-9 and collagen-2 were studied by in situ hybridization. Proteoglycans were visualized with Alcian blue. Apoptosis was detected by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling assay.

Results. The cell numbers in the anulus fibrosus (AF) increased by 25% (P < 0.05) after 3 weeks of exercise. Collagen-2 and Sox-9 mRNA were strongly expressed in the nucleus pulposus (NP) samples of the running group, but weakly expressed in the controls. An increase in collagen-II, aggrecan, and Sox-9 protein expression in NP and AF regions of the disc was detected in the exercised rats compared with controls. Quantification of Alcian blue staining demonstrated increased proteoglycan in both NP (8-fold) and AF (7-fold) in the exercised group compared with controls (P < 0.05). In addition, no significant differences were observed between the experimental groups in cellular apoptosis, collagen-I, or Sox-6 expression.

Conclusion. In this study, increased extracellular matrix production and cell proliferation with no induction of disc cell apoptosis was observed in the lumbar IVD after a 3-week running regimen in rats, suggesting that regular exercise may have an augmentative effect on cells and matrix production.

A regime of regular exercise for 3 weeks in rats increased cellularity and extracellular matrix production, with no induction of cellular apoptosis in lumbar intervertebral discs, suggesting that regular exercise may have an augmentative effect on matrix production.

From the *Department of Orthopaedics, Sahlgrenska University Hospital, Gothenburg University, Gothenburg, Sweden; and †Department of Orthopaedics Surgery, The University of New South Wales St. George Hospital Campus, New South Wales, Australia.

Acknowledgment date: March 25, 2009. Revision date: August 17, 2009. Acceptance date: September 2, 2009.

The manuscript submitted does not contain information about medical device(s)/drug(s).

Funds were received in support of this work. No benefits in any form have been or will be received from a commercial party related directly or indirectly to the subject of this manuscript.

Supported by Spine Service, St. George Hospital, South East Health, Sydney, Wennergrens' Foundation, The Marianne and Marcus Wallenberg Foundation, the Gothenburg Medical Society, and The Swedish Medical Society.

This study was conducted after approval from the University of New South Wales Animal Care and Ethics Committee (ACEC).

The first two authors contributed equally to the work and share the first authorship.

Address correspondence and reprint requests to Ashish Diwan, MD, Orthopaedic Research Institute, Level 2, 4-10 South Street, Kogarah, NSW 2217, Australia; E-mail: a.diwan@spineservice.org

© 2010 Lippincott Williams & Wilkins, Inc.