Histology images (PAS (A) and von Kossa (B) staining) under 10-fold magnification).

<p>The scale bars in the right column indicate 120 μm. The tendon specimens revealed an increased formation of extracellular matrix (*) after stimulation with BMP-7 at week 4 (bT+BMP and pOB+bT+BMP). Stimulation with BMP-7 led to intratendinous calcification (arrowhead). At 8 weeks, limited extracellular matrix formation was found in monoculture without BMP (bT-BMP), whereas coculture without BMP-7 (pOB+bt-BMP) showed increased rates of ECM formation and intratendinous calcification areas (arrowhead). Stimulation with BMP-7 further increased ECM formation and calcification compared to the specimens at week 4. At 12 weeks, coculture with BMP-7 application (pOB+bT+BMP) showed the highest amount of ECM (*), osteoid (#) and calcification (arrowhead), followed by monoculture with BMP-7 (bT+BMP) and coculture without BMP (pOB+bT-BMP). Calcification was detected in areas close to the extracellular matrix as shown in panel A in the pOB+bT-BMP group at 10 weeks. Monoculture without BMP (bt-BMP) showed limited ECM and intratendinous calcified tissue.