Analysis of femoral hematopoietic reconstitution after endoscopy. At 24 hours after irradiation at 10 Gy, C57BL/6 recipient mice were transplanted with 1000 LSKCD34⁻ GFP⁺; and 1 day later, an endoscopy was performed in the right femur of the recipient mice. (A) Eight days and 1 month after this first endoscopy, mice were killed, bone marrow from right and left femurs was flushed, and the GFP⁺ cells were counted by FACS analysis (8 days after endoscopy) and phenotyped by FACS analysis (8 days and 1 month after endoscopy). Graphics show the number of GFP⁺ cells present in right and left femurs 8 days after the endoscopy of the right femur and the percentage of immature hematopoietic cells (LSK), lymphocytes (B220, CD3, and NK1.1), myelocytes (CD11b), and erythrocytes (Ter119) found in the bone marrow of the right and left femurs of mice 8 days and 1 month after endoscopy. The percentage of GFP⁺ cells found in the different hematopoietic populations of a femur from nonirradiated and nonendoscoped mice is also shown (n = 5 for each group of mice). Error bars represent SEM. (B) Eight days after the first endoscopy, endoscopies were performed in the right and the left femurs of the same mouse. Pictures representative of GFP⁺ hematopoietic cells present in the knee, diaphysis, and femoral head areas are shown. These pictures represent frames of 30 to 50 seconds acquired videos over the length of the femur. Scale bar represents 50 μm. No difference could be detected in the imaging of double-scanned right femurs and simple-scanned left femurs. These data are representative of 3 independent experiments. (C) Eight days after this endoscopy, single-scanned right femur and intact left femur from transplanted mice were removed, included in paraffin, and cut longitudinally into 4-μm-depth slices for histologic analysis with hematoxylin-eosin-safran coloration. → indicates the path of the needle in the femoral cavity (left panel). Compared with control femur (right panel), endoscoped femur (left panel) demonstrated a similar organization of bone trabeculae. In both femurs, identical cellularity of hematopoietic and stromal cells was observed (2 adjacent top middle panels). Finally, the beginning of restoration of the endochondreal ossification was evidenced in the right endoscoped femur (bottom left panel): fibrous scar resulting from the endoscopic procedure is replaced by chondroid matrix (*) inhabited by few chondrocytes (→).