BMP-2 induces the expression of chondrocyte-specific genes in bovine synovium-derived progenitor cells cultured in three-dimensional alginate hydrogel.
OBJECTIVE
According to recent reports, the synovial membrane may contain mesenchymal stem cells with the potential to differentiate into chondrocytes under appropriate conditions. In order to assess the usefulness of synovium-derived progenitor cells for the purposes of cartilage tissue engineering, we explored their requirements for the expression of chondrocyte-specific genes after expansion in vitro.


METHODS
Mesenchymal progenitor cells were isolated from the synovial membranes of bovine shoulder joints and expanded in two-dimensions on plastic surfaces. They were then seeded either as micromass cultures or as single cells within alginate gels, which were cultured in serum-free medium. Under these three-dimensional conditions, chondrogenesis is known to be supported and maintained. Cell cultures were exposed either to bone morphogenetic protein-2 (BMP-2) or to isoforms of transforming growth factor-beta (TGF-beta). The levels of mRNA for Sox9, collagen types I and II and aggrecan were determined by RT-PCR.


RESULTS
When transferred to alginate gel cultures, the fibroblast-like synovial cells assumed a rounded form. BMP-2, but not isoforms of TGF-beta, stimulated, in a dose-dependent manner, the production of messenger RNAs (mRNAs) for Sox9, type II collagen and aggrecan. Under optimal conditions, the expression levels of cartilage-specific genes were comparable to those within cultured articular cartilage chondrocytes. However, in contrast to cultured articular cartilage chondrocytes, synovial cells exposed to BMP-2 continued to express the mRNA for alpha1(I) collagen.


CONCLUSIONS
This study demonstrates that bovine synovium-derived mesenchymal progenitor cells can be induced to express chondrocyte-specific genes. However, the differentiation process is not complete under the chosen conditions. The stimulation conditions required for full transformation must now be delineated.
Park
Y
Y
ITI Research Institute for Dental and Skeletal Biology, University of Bern, Murtenstrasse 35, P.O. Box 54, 3010 Bern, Switzerland.
Sugimoto
M
M
Watrin
A
A
Chiquet
M
M
Hunziker
E B
EB
D000464:Alginates; D000818:Animals; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins / Q000494:pharmacology*; D002358:Cartilage, Articular / Q000166:cytology / Q000502:physiology*; D002417:Cattle; D018929:Cell Culture Techniques; D002454:Cell Differentiation / Q000187:drug effects; D015870:Gene Expression / Q000187:drug effects*; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D059630:Mesenchymal Stem Cells / Q000166:cytology / Q000187:drug effects*; D016133:Polymerase Chain Reaction; D013583:Synovial Membrane / Q000502:physiology; D016212:Transforming Growth Factor beta / Q000494:pharmacology*
D000464:Alginates; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins; D016212:Transforming Growth Factor beta; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate