Figure 3.

Extracellular matrix protein deposition was altered by dynamic mechanical strain. All images show 10-μm paraffin-embedded sections, immunostained for types III collagen, IV collagen, and fibronectin (all in green), with a red nuclear counterstain; arrow indicates direction of strain and bar = 150 μm. Top row shows representative co-culture images from unstrained controls, while the middle row shows representative co-culture images from 10% strain, 1 cph. The bottom row shows the image intensity analysis averaged for all fibroblast-only and co-culture samples. (A) Type III collagen in unstrained versus (B) strained samples, where deposition was highest just beneath the epithelium and decreased with depth into the tissue (arrow indicates strain direction). (C) Type III collagen upregulation was greater for all strain levels except the highest strain rate applied (30% at 60 cph) in both fibroblast only and co-culture systems when compared with their respective static controls. (D) Type IV collagen expression in unstrained versus (E) strained samples, where deposition was also highest near the epithelium and decreased with depth. (F) Significant increase in type IV collagen was seen only with 10% strain in co-cultures. (G) Fibronectin production in unstrained versus (H) strained samples, where production was noticeably decreased. (I) Fibronectin quantification showed a significant decrease with all levels of strain and in the presence of the epithelium. *P < 0.05 compared with respective static controls.