Abstract
Introduction
The hierarchical structure of tendon results in a complex mechanical strain environment, with tenocytes experiencing both tension and shear during loading. The mechanotransduction mechanisms involved in sensing these environments is currently unclear. To better understand the effects of shear and tension on cell behaviour, a fibre composite system able to recapitulate the physiological shear-tension ratio found in tendons, was used. Cell attachment within the composite was achieved by using either a collagen type I mimetic peptide, DGEA, or a fibronectin associated peptide, YRGDS, and the gene expression response analysed after loading.
Materials and Methods
Fibre composites with 4 different shear-tension (S-T) ratios were made using both PEG-DGEA and PEG-YRGDS fibres. 4 composites were made for each S-T ratio, of which 2 were loaded and 2 used as non-strained controls. Bovine digital extensor tendon tenocytes were seeded within composites, with 3 biological repeats from different donors. Loaded samples were exposed to 5% cyclic strain (1Hz) for 24 hours maintained in an incubator. The gene expression of 14 matrix related genes were analysed after loading via RT-qPCR.
Results
Tenocytes seeded on PEG-DGEA fibres were more mechano-sensitive than those seeded on PEG-YRGDS fibres; tenocytes in PEG-DGEA composites exhibited upregulation of COL-3, MMP-3 and IL-6, and downregulation of SCX with shear, while tenocytes in PEG-YRGDS composites downregulated TIMP-3 with shear.
Discussion
The main integrin involved in DGEA binding is α2β1 while the integrins associated with YRGDS attachment include α5β1, αVβ3 and αIIbβ3. Consequently, the findings of this study emphasise the importance of integrins in the role of mechanotransduction, and suggest integrins involved in collagen type I binding induce functionally different responses in tenocytes to those not involved in collagen type I binding when sensing mechanical stimuli comprised of shear and tension. This information is critical in future studies investigating tenocyte behaviour and tissue engineering approaches, as physiological integrin binding may be key in maintaining normal tenocyte pathways.
