Collagen type X and aggrecan. (A-D) Collagen type X; (E-H) aggrecan; (A,E) ACL from young normal knee; (B,F) ACL from aging knee; (C,G) fibroblast-like cell aggregates in the degenerated ACL; (D,H) chondrocyte-like cell aggregates in the degenerated ACL. Type X collagen-positive area is observed around chondrocyte-like cell aggregates (black arrows), and aggrecan was observed around chondrocyte-like cell aggregates in the ACL midsubstance (white arrows). (Original magnification ×40).
Hasegawa et al. Arthritis Research & Therapy 2013 15:R29 doi:10.1186/ar4165