Open Access Highly Accessed Research article

Aging is associated with increased activities of matrix metalloproteinase-2 and -9 in tenocytes

Tung-Yang Yu12, Jong-Hwei S Pang2, Katie Pei-Hsuan Wu1, Max J-L Chen1, Chien-Hung Chen1 and Wen-Chung Tsai13*

Author Affiliations

1 Departement of Physical Medicine and Rehabilitation, Chang Gung Memorial Hospital, Linkou, Taiwan

2 Graduate Institute of Clinical Medical Sciences, Chang Gung University, Kwei-Shan Tao-Yuan, Taiwan

3 College of Medicine, Change Gung University, Kwei-Shan Tao-Yuan, Taiwan

For all author emails, please log on.

BMC Musculoskeletal Disorders 2013, 14:2  doi:10.1186/1471-2474-14-2

Published: 2 January 2013



Most tendon pathology is associated with degeneration, which is thought to involve cyclic loading and cumulative age-related changes in tissue architecture. However, the association between aging and degeneration of the extracellular matrix (ECM) in tendons has not been investigated extensively.


We examined tenocytes from Achilles tendons taken from rats of three different ages (2, 12, and 24 months). Tenocyte viability was assessed using the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay. Quantitative real-time polymerase chain reaction (PCR) was used to determine the levels of mRNAs that encode type-I collagen, matrix metalloproteinase (MMP)-2 and −9, tissue inhibitor of metalloproteinase (TIMP)-1 and −2 and transforming growth factor (TGF)-β1. Gelatin zymography was used to evaluate the enzymatic activities of MMP-2 and −9. Furthermore, the concentration of TGF-β1 in conditioned medium was evaluated using enzyme-linked immunosorbent assay (ELISA).


The results of the MTT assay showed that the number of viable tenocytes decreased with age. No differences were observed in the levels of mRNAs that encode type-I collagen and TGF-β1 among the three age groups, and the TGF-β1 concentration did not change with age. However, mRNAs that encode MMP-2 and −9 were significantly more abundant in tenocytes from the aging group, and gelatin zymography revealed that the enzymatic activities of MMP-2 and −9 also increased significantly with age. Furthermore, as compared with young group, mRNAs that encode TIMP-1 and −2 were significantly decreased in tenocytes from the aging group.


Activities of MMP-2 and MMP-9 in tenocytes increase with age. This might provide a mechanistic explanation of how aging contributes to tendinopathy or tendon rupture with age.

Aging; Collagen; Matrix metalloproteinase; Tenocytes; Transforming growth factor-beta 1