A role for chemokines in the induction of chondrocyte phenotype modulation.
OBJECTIVE
To extend the study of the chemokine receptor repertoire on human chondrocytes to receptors with reported housekeeping functions (CXCR3, CXCR4, CXCR5, and CCR6) and to evaluate whether ligands of these receptors play a role in chondrocyte phenotype modulation and proliferation.


METHODS
Chemokine receptor expression was determined by flow cytometry. Subcultures of chondrocytes were collected and fixed at confluence or during the exponential phase of growth and analyzed for chemokine receptor modulation. The effects of chemokines on isolated cells as well as chondrocytes cultured within an intact extracellular matrix were investigated. Isolated human chondrocytes were stimulated with 100 nM chemokines (monokine induced by interferon-gamma, stromal cell-derived factor 1alpha [SDF-1alpha], B cell-attracting chemokine 1 [BCA-1], or macrophage inflammatory protein 3alpha), and conditioned media were assessed for matrix-degrading enzyme contents (matrix metalloproteinases [MMPs] 1, 3, and 13, and N-acetyl-beta-D-glucosaminidase [NAG]). Cell proliferation and phenotype modulation were evaluated by bromodeoxyuridine incorporation and cathepsin B production. Induction of cell proliferation was assessed in cartilage explants by immunodetection of the proliferation-associated antigen S100A4.


RESULTS
CXCR3, CXCR4, CXCR5, and CCR6 were detected on human chondrocytes. CXCR3 and CXCR4 expression was increased in exponentially growing chondrocyte subcultures. Ligands of all receptors enhanced the release of MMPs 1, 3, and 13. Release of NAG and cathepsin B was significantly higher in chemokine-stimulated cultures than in unstimulated cultures. SDF-1alpha and BCA-1 also induced DNA synthesis and chondrocyte proliferation, as was shown by the up-regulation of S100A4 in cartilage explants as well.


CONCLUSIONS
Our findings extend the repertoire of functional responses elicited by the activity of chemokines on chondrocytes and open new avenues in our understanding of the control of chondrocyte differentiation status by chemokines and their receptors.
Mazzetti
Ilaria
I
Istituti Ortopedici Rizzoli, Bologna, Italy.
Magagnoli
Giorgia
G
Paoletti
Samantha
S
Uguccioni
Mariagrazia
M
Olivotto
Eleonora
E
Vitellozzi
Roberta
R
Cattini
Luca
L
Facchini
Andrea
A
Borzì
Rosa Maria
RM
D000118:Acetylglucosaminidase / Q000378:metabolism; D000328:Adult; D000368:Aged; D002401:Cathepsin B / Q000378:metabolism; D002455:Cell Division; D002478:Cells, Cultured; D018925:Chemokines / Q000494:pharmacology; D019902:Chondrocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D017364:Collagenases / Q000378:metabolism; D005089:Exocytosis / Q000502:physiology; D006801:Humans; D016130:Immunophenotyping; D020781:Matrix Metalloproteinase 1 / Q000378:metabolism; D053509:Matrix Metalloproteinase 13; D019278:Matrix Metalloproteinase 3 / Q000378:metabolism; D008875:Middle Aged; D010003:Osteoarthritis / Q000276:immunology* / Q000378:metabolism*; D054399:Receptors, CCR6; D054367:Receptors, CXCR3; D019718:Receptors, CXCR4 / Q000378:metabolism; D054380:Receptors, CXCR5; D019707:Receptors, Chemokine / Q000378:metabolism*; D018121:Receptors, Cytokine / Q000378:metabolism; D000071999:S100 Calcium-Binding Protein A4; D009418:S100 Proteins / Q000378:metabolism
C106311:CCR6 protein, human; C515187:CXCR3 protein, human; C095085:CXCR5 protein, human; D018925:Chemokines; D054399:Receptors, CCR6; D054367:Receptors, CXCR3; D019718:Receptors, CXCR4; D054380:Receptors, CXCR5; D019707:Receptors, Chemokine; D018121:Receptors, Cytokine; D000071999:S100 Calcium-Binding Protein A4; D009418:S100 Proteins; C077591:S100A4 protein, human; D000118:Acetylglucosaminidase; D002401:Cathepsin B; D017364:Collagenases; C507079:MMP13 protein, human; D053509:Matrix Metalloproteinase 13; D019278:Matrix Metalloproteinase 3; D020781:Matrix Metalloproteinase 1