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Arthritis Rheum. 2010 Aug;62(8):2370-81. doi: 10.1002/art.27512.

Matrix metalloproteinase 13 loss associated with impaired extracellular matrix remodeling disrupts chondrocyte differentiation by concerted effects on multiple regulatory factors.

Author information

1
Istituti Ortopedici Rizzoli, Bologna, Italy. rosamaria.borzi@ior.it

Abstract

OBJECTIVE:

To link matrix metalloproteinase 13 (MMP-13) activity and extracellular matrix (ECM) remodeling to alterations in regulatory factors leading to a disruption in chondrocyte homeostasis.

METHODS:

MMP-13 expression was ablated in primary human chondrocytes by stable retrotransduction of short hairpin RNA. The effects of MMP-13 knockdown on key regulators of chondrocyte differentiation (SOX9, runt-related transcription factor 2 [RUNX-2], and beta-catenin) and angiogenesis (vascular endothelial growth factor [VEGF]) were scored at the protein level (by immunohistochemical or Western blot analysis) and RNA level (by real-time polymerase chain reaction) in high-density monolayer and micromass cultures under mineralizing conditions. Effects on cellular viability in conjunction with chondrocyte progression toward a hypertrophic-like state were assessed in micromass cultures. Alterations in SOX9 subcellular distribution were assessed using confocal microscopy in micromass cultures and also in osteoarthritic cartilage.

RESULTS:

Differentiation of control chondrocyte micromasses progressed up to a terminal phase, with calcium deposition in conjunction with reduced cell viability and scant ECM. MMP-13 knockdown impaired ECM remodeling and suppressed differentiation in conjunction with reduced levels of RUNX-2, beta-catenin, and VEGF. MMP-13 levels in vitro and ECM remodeling in vitro and in vivo were linked to changes in SOX9 subcellular localization. SOX9 was largely excluded from the nuclei of chondrocytes with MMP-13-remodeled or -degraded ECM, and exhibited an intranuclear staining pattern in chondrocytes with impaired MMP-13 activity in vitro or with more intact ECM in vivo.

CONCLUSION:

MMP-13 loss leads to a breakdown in primary human articular chondrocyte differentiation by altering the expression of multiple regulatory factors.

PMID:
20506238
PMCID:
PMC2921033
DOI:
10.1002/art.27512
[Indexed for MEDLINE]
Free PMC Article
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