Gene expression of COL1A1 and COL3A1.

<p>COL1A1 and CoL3A1 mRNA normalized to tissue weight, presented as fold changes in the exercise group (filled bars) relative to the mean of the control group (open bars) in Achilles tendon and soleus muscle. In tendon COL3A1 mRNA was significantly increased (p<0.05) in the Exercise group and COL1A1 mRNA showed a strong tendency to an increase (p = 0.09). In exercised soleus muscle both COL1A1 (p<0.01) and COL3A1 (p<0.001) were significantly increased. Values are geometric means ± SEM.</p

SUV of <i>cis</i>-FPro in musculoskeletal tissues 60 minutes and 240 minutes post-injection (resting levels).

<p>The figure illustrates the changes in <i>cis</i>-Fpro uptake in the musculoskeletal tissues at two time points following injection of the tracer. In trabecular and cortical bones <i>cis</i>-Fpro uptake increased significantly (p<0.001) when comparing the values from the early PET scan (60 minutes post injection) to the late (240 minutes post injection). This was contradicted by a continuous decrease in tendon and muscle (p<0.001). Values are the mean ± SEM of all rats in the Exercise (only pre-exercise values) and Control group at the two time points post injection.</p

PCR Primers.

<p>PCR Primers.</p

Summary of findings after de-tensioning of 3D tendon-constructs and TGF-β1 supplementation.

<p>The 3D tendon-construct under static tension without TGF-β1 is set as baseline, all other conditions are shown relative to the tensioned 3D tendon-construct (n = 5). A) Analysis of genes encoding for different matrix proteins: Collagen type I (COL1A1), collagen type III (COL3A1), collagen type XII (COL12A1) collagen type XIV (COL14A1) and fibronectin. B) Analysis of tendon phenotypic markers and tendon-related genes: tenomodulin (TNMD), scleraxis (SCX), Mohawk homeobox (MKX), fibromodulin (FBMD), decorin and GAPDH. Data presented on a logarithmic y scale as geometric means ± SEM with 3D tendon construct as baseline (n = 5). Significant 2-way ANOVA (tension*TGF-β1) main effects written above the graphs. For FBMD, * indicates significant effect of TGF-β1 for the individual groups in the post hoc analysis.</p

Release of Tensile Strain on Engineered Human Tendon Tissue Disturbs Cell Adhesions, Changes Matrix Architecture, and Induces an Inflammatory Phenotype

<div><p>Mechanical loading of tendon cells results in an upregulation of mechanotransduction signaling pathways, cell-matrix adhesion and collagen synthesis, but whether unloading removes these responses is unclear. We investigated the response to tension release, with regard to matrix proteins, pro-inflammatory mediators and tendon phenotypic specific molecules, in an <i>in vitro</i> model where tendon-like tissue was engineered from human tendon cells. Tissue sampling was performed 1, 2, 4 and 6 days after surgical de-tensioning of the tendon construct. When tensile stimulus was removed, integrin type collagen receptors showed a contrasting response with a clear drop in integrin subunit α₁₁ mRNA and protein expression, and an increase in α₂ integrin mRNA and protein levels. Further, specific markers for tendon cell differentiation declined and normal tendon architecture was disturbed, whereas pro-inflammatory molecules were upregulated. Stimulation with the cytokine TGF-β1 had distinct effects on some tendon-related genes in both tensioned and de-tensioned tissue. These findings indicate an important role of mechanical loading for cellular and matrix responses in tendon, including that loss of tension leads to a decrease in phenotypical markers for tendon, while expression of pro-inflammatory mediators is induced.</p></div

Summary of mRNA expression of tendon-related genes as a response to changes in the spatial/mechanical environment and TGF-β1 supplementation.

<p>Summary of <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0086078#pone-0086078-g002" target="_blank">figure 2</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0086078#pone-0086078-g003" target="_blank">3:</a> The effect of the intervention is compared to the gene expression of the respective target cultured for six days under static tension, the arrows (↑↓) indicate significant changes relative to the tensioned samples, or no statistical change (↔). Arrows in parenthesis indicate a tendency (p< 0.1). Tenomodulin (TNMD); Scleraxis (SCX); Mohawk homeobox (MKX); Collagen type I (COL1A1); collagen type III (COL3A1); collagen type XII (COL12A1); collagen type XIV (COL14A1); Fibronectin (FN); Decorin (DCN); Fibromodulin (FBMD); Transforming growth factor-β1 (TGFB1); Connective tissue growth factor (CCN2); Glyceraldehyde 3-phosphate dehydrogenase (GAPDH).</p

Comparison between 2D monolayer and 3D tendon-constructs under static tension.

<p>The 3D tendon-construct is set as baseline, and mRNA expression of tendon cells grown on 2D monolayer is shown relative to the 3D tendon construct. Significant changes are indicated by *. Data presented on a logarithmic y scale baseline as geometric means ± SEM with 3D tendon-construct as baseline (n = 5).</p

Overview over the effect of de-tensioning and TGF-β1 supplementation on mRNA expression of tendon matrix genes and growth factors.

<p>Left panel (A, D, G, J): Effect of de-tensioning, mid panel (B, E, H, K): Effect of TGF-β1 on tensioned 3D tendon-constructs, right panel (C, F, I, L): Effect of TGF-β1 on de-tensioned 3D tendon-constructs. The data are presented on a logarithmic y scale as geometric means ± SD (n = 3) where Tension Day 1 is baseline. Significant 2-way RM ANOVA (tension*time) or (TGF-β1*time) main effects written above the graphs. Open triangles: 3D tendon-construct under tension, without TGF-β1 supplementation; open circles: 3D tendon-construct de-tensioned, without TGF-β1 supplementation; filled triangles: 3D tendon-construct under tension, with TGF-β1 supplementation; filled circles: 3D tendon-construct de-tensioned, with TGF-β1 supplementation.</p

Overview over the effect of de-tensioning on protein expression of different integrin subunits.

<p>A) Effect of de-tensioning on integrin sub-unit α5, B) Effect of de-tensioning on integrin sub-unit α11, C) Effect of de-tensioning on integrin sub-unit β1. The data are presented on a logarithmic y scale as geometric means ± SD (n = 3) where Tension Day 1 is baseline. Significant 2-way RM ANOVA (tension*time) main effects written above the graphs. Open triangles: 3D tendon-construct under tension, without TGF-β1 supplementation; open circles: 3D tendon-construct de-tensioned, without TGF-β1 supplementation. Below the graphs, representative western blots are shown (+/- tension).</p

Overview over the effect of de-tensioning on protein expression of integrin subunit α₂.

<p>The figure shows the western blot of one 3D tendon-construct over four time points shown(+/- tension).</p