MPs in the injured nerve have dual origin. (a) CCI is performed on Ccr2^−/− host in parabiosis with MacBlue × Cx3cr1^egfp/+ donor mice, and fluorescent cells are tracked 10 and 20 d after nerve injury. Representative TPLSM tiled and stitched image reconstitution (scale bar = 50 µm) and quantification of the relative proportion of EGFP⁺ and ECFP⁺ cells in injured sciatic nerve cryosections in host parabiont and nonparabiotic MacBlue × Cx3cr1^egfp/+ mice (data represent a pool from three or four parabioses and four nonparabioses per time point processed independently; ANOVA with Bonferroni’s multiple comparison test was performed). (b) TPLSM images show the defect in ECFP⁺ cell accumulation in MacBlue × Cx3cr1^egfp/+ Ccr2^−/− mouse compared with MacBlue × Cx3cr1^egfp/+. Scale bars = 30 µm. (c) Quantification (number/mm²) of ECFP⁺ (upper panel) and EGFP⁺ cells (lower panel) from nerve cryosection (n = 4–5 mice per time point processed independently; P values of two-way ANOVA with Bonferroni multiple comparison tests are indicated). ***, P < 0.001.