Effects of cell adhesion motif, fiber stiffness, and cyclic strain on tenocyte gene expression in a tendon mimetic fiber composite hydrogel

Highlights: • A fiber composite material exhibits multimodal shear and tension micromechanics. • Gene expression of tenocytes is insensitive to fiber stiffness or YRGDS vs DGEA. • Tendon marker and collagen genes are insensitive to fiber environment under strain. • MMP3 and IL6 genes are sensitive to fiber stiffness and peptide under cyclic strain. • Healthy tenocytes rapidly respond to their environment by a catabolic response. We recently developed a fiber composite consisting of tenocytes seeded onto discontinuous fibers embedded within a hydrogel, designed to mimic physiological tendon micromechanics of tension and shear. This study examined if cell adhesion peptide (DGEA or YRGDS), fiber modulus (50 or 1300 kPa) and/or cyclic strain (5% strain, 1 Hz) influenced bovine tenocyte gene expression. Ten genes were analyzed and none were sensitive to peptide or fiber modulus in the absence of cyclic tensile strain. Genes associated with tendon (SCX and TNMD), collagens (COL1A1, COL3A1, COL11A1), and matrix remodelling (MMP1, MMP2, and TIMP3) were insensitive to cyclic strain. Contrarily, cyclic strain up-regulated IL6 by 30-fold and MMP3 by 10-fold in soft YRGDS fibers. IL6 expression in soft YRGDS fibers was 5.7 and 3.3-fold greater than in soft DGEA fibers and stiff RGD fibers, respectively, under cyclic strain. Our findings suggest that changes in the surrounding matrix can influence catabolic genes in tenocytes when cultured in a complex strain environment mimicking that of tendon, while having minimal effects on tendon and homeostatic genes.