The specificity of 2.3ColGFP expression in transduced TRCs in vivo. (a). GFP expression in a representative area of a whole TRCs ossicle frozen-section from a 4-week 2.3ColGFP implant. The left panel is a bright field in which a dotted line in red outlines a bone formation area inside the ossicle and the area between the red line and yellow line is a fibrous tissue. The right panel is a fluorescence phase, in which a dotted white line outlines the corresponding bone formation area inside the ossicle; the area between the white line and yellow line is the corresponding fibrous tissue. Original magnification: ×40. (b). Three representative areas from panel b were examined at a higher magnification (×200). A, an area full of cells with strong GFP expression. B, a field containing a bony structure in the middle along with GFP+ cells on both sides. C, a display of two clusters of cells with extremely high expression of 2.3ColGFP. (c). H&E staining of the ossicle section at a magnification of ×200 (left) and ×400 (right). GFP, green fluorescent protein; hBMSCs, human bone marrow stromal cells.