Figure 2: Fluorescence intensity and stress in tail tendon fascicles at incremental strains.

(a) Average stress–strain curves for each of the strain groups tested (n=3 each curve). Fascicle mechanical behaviour encompassed the range of linear behaviour to tissue failure. For clarity, the standard error bars are only shown for the last 1% strain of each curve. (b) Representative whole-sample fluorescence scans of 5, 10.5 and 15% strain samples, and the corresponding brightfield image for the 15% strain sample, clearly showing an increase in CF-CHP staining with increased strain. In these images, fascicles have been folded on microscope slides showing the stretched section on the left half of the image and the clamped ends on the right half of the image. Arrows indicate the approximate location of clamping. Scale bars, 2 mm. (c) Mean pixel intensity (n=5, 0% strain; n=3, 1–15% strain, mean±s.e.m.) quantified from fluorescence images of loaded fascicles (left axis) and the average percentage of collagen digested by trypsin (right axis) from fascicles in each group (0, 5, 7.5, 9, 10.5, 15% strain, n=5, mean±s.e.m.). The orange dotted lines in a and c indicate the approximate transition strain from the linear region of the stress–strain curve to the onset of damage as identified by the deviation of the stress–strain curve from linearity, which correlates with onset of CF-CHP intensity.