Figure 2.

Prx1-expressing cells become embedded osteocytes in response to mechanical loading. (a) Prx1CreER-GFP(+) cells (brown) were detected in the periosteum surrounding the nonloaded (A) and loaded bone (B). Arrows denote examples of these cells for clarity. Osteocytes, muscle cells, bone marrow cells, and other cells in the periosteum were negative for GFP staining. (b) Beta-galactosidase staining was used to detect cells in which recombination had occurred (brown). Osteocytes near the periosteal surface demonstrated recombination in the loaded bone ((B), red boxes), but these cells were absent from nonloaded limbs (A). Brown coloration observed in the periosteum, muscle, and lacunae without corresponding nuclei (blue) was also seen in negative controls and thus deemed nonspecific staining. Nuclei were stained with hematoxylin, and micrographs were collected at 20x magnification.