Mouse parabiosis model.

To investigate the effect of circulating cells to form the regenerate, after MF we parabiosed GFP⁺ homozygous mice with C57BL/6. Both mice were positioned side by side in the supine position with the non-GFP mouse on the right and the GFP⁺ mouse on the left. Under general anesthesia (isoflurane), we made a longitudinal (midaxial line) incision from knee to elbow on the right side of the C57BL/6 and the left side of the GFP⁺ mouse. Deep 4-0 prolene sutures were placed uniformly through the muscle bellies of both mice along the quadriceps, obliques, latissimus dorsi and triceps. The skin was closed with 6-0 prolene. For confirmation of adequate chimerism, we used FACS to analyze the circulation of the non-GFP mouse, showing GFP⁺ cells at 4 weeks by a blood draw from a tail-vein assay of the C57BL/6 mice at 4 weeks. After confirming crosscirculation at 4 weeks, MF surgery was performed on the left knee of the non-GFP parabiont, using a technique described above in the Mouse MF model in the C57BL/6 mouse.