ITGAM and intervertebral disk degenerative disorder: Given the fibrocytes being a lineage of monocytes expressing CD11b, we studied their temporospatial distribution in puncture injury-induced disc degeneration in CD11b-DTR mice, in which the expression of EGFP-diphtheria toxin (DT) receptor fusion protein is controlled by the ITGAM promoter, thereby directing transgene expression and expressing membrane-localized green fluorescence protein (GFP) in monocytes/macrophages.23,28 Normal mouse NP, which contains predominantly notochordal cells,4 was negative for GFP expression (Fig. S10).