Figure 2.

Morphological changes of mesenchymal stem cells analyzed at 2, 6, and 24 h post-seeding. (A) Area, (B) circularity, and (C) aspect ratio measurements were taken. The results indicate that stem cells on the acid-etched endoskeleton surface spread the most over 24 h. The circularity of the three surfaces began dissimilar, but converged at 24 h. The aspect ratio of stem cells initially began close to 1, but over 24 h, the smooth surfaces, Ti and PEEK, increased significantly higher than the rough, acid-etched endoskeleton surface. Taken together, the aspect ratio and circularity indicate that stem cells on smooth surfaces move toward a spindle or fibroblastic morphology, whereas those on the rough, acid-etched endoskeleton surface moved toward a stellate or star-like morphology. Within a single time point, * indicates significance, p < 0.05 between acid-etched Ti and PEEK, ^† indicates significance between acid-etched Ti and Ti, and ^§ indicates significance between PEEK and Ti. Color-coded bars demonstrate significance between time points for a single surface.