Table 1

Biomarkers of bone, cartilage and synovial turnover, and the BIPED classification

Tissue

Molecule

Markers of synthesis

Markers of degradation

BIPED classification

Bone

Type I collagen

PYD^a

B

NTX-I^a,b

D

CTX-I^a,b

P

Noncollagenous proteins

Osteocalcin^b

P

Cartilage

Type II collagen

PIIANP^b

P

Total PIINP

D

PIICP^b,c

D, P

CTX-II^a,c

D, B, P, E

HELIX-IIa

P

Coll 2-1^a,b

P

Coll 2-1 NO₂^a,b

P

C2C^a,b

P, E

1,2C^a,b

P, E

Aggrecan

Epitope 846 (cartilage content^c)

E

Nonaggrecan and noncollagenous proteins

COMP^b,c

D, B, P

Pentosidine^a,b

P

Proteases and their inhibitors

MMPs^b

B, P, E

TIMPs^b

B, P

Synovium

Type III collagen

GIc-GaI-PYD^a

E

Noncolagenous proteins

YKL-40^b,c

B, E

Hayluronic acid^b

B, P

^aUrine. ^bSerum. ^c Synovial fluid. BIPED, B (burden of disease), I (investigative), P (prognostic), E (efficacy of intervention), D (diagnostic); C1,2C, assay that detects COL2-3/4C (short) epitope; C2C, assay that detects COL2-3/4C (long) epitope; Coll 2-1, 9-amino-acid peptide of type II collagen; Coll 2-1 NO₂, nitrated form of Coll 2-1; COMP, cartilage oligomeric protein; CTX-I, carboxyl-terminal cross-linked telopeptide of type I collagen; CTX-II, C-terminal cross-linked telopeptide of type II collagen; Glc-Gal-PYD, glucosyl-galactosyl-pyridinoline; HELIX-II, helical type II collagen; MMP, matrix metalloproteinase; NTX-I, N-terminal cross-linked telopeptide of type I collagen; PIIANP, N-propeptide IIA of collagen type II; PIICP, C-propeptide of collagen type II; PIINP, N-propeptide II of collagen type II; PYD, pyridinoline; TIMP, tissue inhibitor of matrix metalloproteinase; YKL-40, cartilage glycoprotein 39. Reproduced with permission from Rouseeau and Delmas [80].

Abramson and Attur Arthritis Research & Therapy 2009 11:227   doi:10.1186/ar2655