title: Elevated Levels of Cartilage Oligomeric Matrix Protein during In Vitro Cartilage Matrix Generation Decrease Collagen Fibril Diameter.
abstract: Cartilage oligomeric matrix protein (COMP) is a protein present in the cartilage matrix and is expressed more abundantly in osteoarthritis cartilage than in healthy cartilage. The present study was designed to investigate the effect of transforming growth factor β (TGFβ) on COMP deposition and the influence of COMP on collagen biochemistry in a long-term 3-dimensional culture. Bovine chondrocytes in alginate beads were cultured with or without 25 ng/mL TGFβ2 for 21 or 35 days. COMP was overexpressed in bovine chondrocytes using lentiviral transfection. COMP gene expression, COMP protein production, collagen and proteoglycan deposition, and collagen fibril thickness were determined. Addition of TGFβ2 resulted in more COMP mRNA and protein than the control condition without growth factors. Lentiviral transduction with COMP resulted in elevated gene expression of COMP and increased COMP levels in the alginate bead and culture medium compared to untransfected cells. Overexpression of COMP did not affect the deposition of collagen, collagen cross-linking, proteoglycan deposition, or the mechanical properties. Stimulating COMP production by either TGFβ2 or lentivirus resulted in collagen fibrils with a smaller diameter. Taken together, COMP deposition can be modulated in cartilage matrix production by the addition of growth factors or by overexpression of COMP. Inducing COMP protein expression resulted in collagen fibrils with a smaller diameter. Because it has been demonstrated that the collagen fibril diameter is associated with mechanical functioning of the matrix, modulating COMP levels should be taken into account in cartilage regeneration strategies.
authors.affiliation: Business Unit BioSciences, TNO Quality of Life, Leiden, the Netherlands ; Department of Orthopaedics, University Medical Center Rotterdam, Erasmus Medical Center, Rotterdam, the Netherlands.
authors.forename: Y M
authors.initials: YM
authors.lastname: Bastiaansen-Jenniskens
authors.affiliation: Business Unit BioSciences, TNO Quality of Life, Leiden, the Netherlands.
authors.forename: A C W
authors.initials: AC
authors.lastname: de Bart
authors.affiliation: Department of Otorhinolaryngology, University Medical Center Rotterdam, Erasmus Medical Center, Rotterdam, the Netherlands.
authors.forename: W
authors.initials: W
authors.lastname: Koevoet
authors.affiliation: Department of Precision and Microsystems Engineering, Faculty of Mechanical, Maritime and Materials Engineering, Delft University of Technology, Delft, the Netherlands.
authors.forename: K M B
authors.initials: KM
authors.lastname: Jansen
authors.affiliation: Department of Orthopaedics, University Medical Center Rotterdam, Erasmus Medical Center, Rotterdam, the Netherlands.
authors.forename: J A N
authors.initials: JA
authors.lastname: Verhaar
authors.affiliation: Department of Orthopaedics, University Medical Center Rotterdam, Erasmus Medical Center, Rotterdam, the Netherlands ; Department of Otorhinolaryngology, University Medical Center Rotterdam, Erasmus Medical Center, Rotterdam, the Netherlands.
authors.forename: G J V M
authors.initials: GJ
authors.lastname: van Osch
authors.affiliation: Business Unit BioSciences, TNO Quality of Life, Leiden, the Netherlands.
authors.forename: J
authors.initials: J
authors.lastname: DeGroot
keywords: cartilage matrix; cartilage oligomeric matrix protein; chondrocyte; lentivirus; transforming growth factor β