Abundant <i>Agc1-CreERT2</i> labeled Tomato⁺ cells were present in the repair callus during fracture healing.

<p>A: The left tibia of 2.5-month-old <i>Agc1-CreERT2; ROSA-tdTomato</i> mouse and <i>ROSA-tdTomato</i> control mouse were subjected to semi-stabilized fracture surgery. At 7 days after surgery, these mice were treated with tamoxifen and were sacrificed 2 days post tamoxifen. The panels left to panel a: X-ray images of fractured tibiae of <i>ROSA-tdTomato</i> control mouse. day0: right after surgery; day9: 9 days after surgery. Red arrows indicate the fractures. Panel a: the fluorescence image of fractured tibiae of <i>ROSA-tdTomato</i> mouse. Panel a′: Saf-O staining indicates the presence of chondrocytes (red staining) in the repair callus of <i>ROSA-tdTomato</i> fractured tibiae. Panel b: fluorescence image of the fractured tibiae of <i>Agc1-CreERT2; ROSA-tdTomato</i> mouse, Tomato⁺ cells were present specifically in the growth plate (white arrow) and in the repair callus outlined by the dotted lines. The colored rectangles indicate the locations of Tomato⁺ cells in the callus. The panel right to panel b: magnified fluorescence image of the area marked by a red rectangle in b. White asterisks indicate non-specific fluorescence signals. The white arrow indicates the growth plates. Panel b′: Saf-O staining of the fractured tibiae. The red dotted lines outline the repair callus. The colored rectangles mark the areas of red staining. The matching areas in b and b′ are marked by the same colored rectangles. Red asterisks: fracture sites. The red arrow indicates the growth plate. B: The left tibia of 2-month-old <i>Agc1-CreERT2; ROSA-tdTomato</i> mouse and <i>ROSA-tdTomato</i> control mouse were subjected to semi-stabilized fracture surgery. At 6 days after surgery, these mice were treated with tamoxifen and were sacrificed 8 days post tamoxifen. Panel a: fluorescence image of fractured tibiae of <i>ROSA-tdTomato</i> mouse. Panel a′: Saf-O staining of repair callus in fractured tibiae in panel a. The panels left to panel a: X-ray images of fractured tibiae of <i>ROSA-tdTomato</i>. Panel b: fluorescence image of fractured tibiae of <i>Agc1-CreERT2; ROSA-tdTomato</i> mouse. Almost all cells in the callus outlined by the white dotted lines were Tomato⁺ cells. The panel right to panel b: magnified fluorescence image of the area marked by the white rectangle. The white arrow indicates the growth plates. Panel b′: Saf-O staining of the fractured tibiae. The red stippled line outlines the repair callus. The image right to b′: the Saf-O staining of area marked by a yellow rectangle in b′. The red arrow indicates the growth plate.