Figure 1.

Injured p14 IVDs heal regeneratively with highly cellular matrix deposition throughout the injury site and organized AF layers adjacent to the injury while injured p28 IVDs heal with fibrosis

(A–J) Representative (A) ScxGFP and (B) DAPI images of AF controls and injury sites of p14 and p28 mice 56 days after injury with (C) magnified images of injury sites with DAPI. Quantification of (D) % cells expressing ScxGFP and (E) total number of cells within injury sites. Picrosirius Red Alcian blue images of AF controls and injury sites of p14d56 and p28d56 mice under (F) brightfield and (G) polarized light with (H) magnified images of injury sites of p14d56 and p28d56. Quantification of (I) % repair tissue within the injury site and (J) collagen disorganization score. Scale bars = 100 μm. Dashed lines outline injury sites (yellow or green), fibrous caps (purple), and repair tissue (white). Arrows point toward cellular repair tissue (white), fibrous caps (purple), and adjacent AF structures near injury sites (yellow). Biological n = 5/age, error bars = SD. Student’s t test with p < 0.05 determined significance, depicted in graphs as a horizontal black line.