Immunohistochemical analysis of implanted MSCs. a and b The specimens were fixed and embedded in paraffin. Sections of 5 µm cut through the center of the cell masses were stained with anti-Col I antibody. Images show the staining at 3 weeks (a) and 6 weeks (b). Magnification ×10, bar 200 µm. c Immunohistochemical staining of Col I of rat Achilles tendon was used as positive control. d Col I expression was quantified by mean intensity of the images analyzed using Image-Pro Plus 6.0 software. Achilles tendon was used as positive control (each bar represents mean ± SD, n = 5; *p < 0.05, ANOVA).