The heparan sulfate proteoglycan (HSPG) glypican-3 mediates commitment of MC3T3-E1 cells toward osteogenesis
Haupt, Larisa M. ; Murali, Sadasivam ; Mun, Foong Kin ; Teplyuk, Nadiya M. ; Mei, Leong Fong ; Stein, Gary S. ; Van Wijnen, Andre J. ; Nurcombe, Victor ; Cool, Simon M.
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Keywords
Animals
Bone Morphogenetic Protein 2
*Cell Differentiation
*Cell Lineage
Cell Proliferation
Core Binding Factor Alpha 1 Subunit
Extracellular Matrix Proteins
Fibroblast Growth Factor 2
Gene Expression Regulation, Enzymologic
Glypicans
Heparin Lyase
Humans
Mice
Mice, Knockout
Osteoblasts
*Osteogenesis
*Protein Processing, Post-Translational
Proteoglycans
RNA Interference
RNA, Messenger
Receptors, Fibroblast Growth Factor
Recombinant Proteins
Sulfotransferases
Time Factors
Transfection
Versicans
Cell Biology
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Abstract
Heparan sulfate (HS) sugar chains attached to core proteoglycans (PGs) termed HSPGs mediate an extensive range of cell-extracellular matrix (ECM) and growth factor interactions based upon their sulfation patterns. When compared with non-osteogenic (maintenance media) culture conditions, under established osteogenic culture conditions, MC3T3-E1 cells characteristically increase their osteogenic gene expression profile and switch their dominant fibroblast growth factor receptor (FGFR) from FGFR1 (0.5-fold decrease) to FGFR3 (1.5-fold increase). The change in FGFR expression profile of the osteogenic-committed cultures was reflected by their inability to sustain an FGF-2 stimulus, but respond to BMP-2 at day 14 of culture. The osteogenic cultures decreased their chondroitin and dermatan sulfate PGs (biglycan, decorin, and versican), but increased levels of the HS core protein gene expression, in particular glypican-3. Commitment and progress through osteogenesis is accompanied by changes in FGFR expression, decreased GAG initiation but increased N- and O-sulfation and reduced remodeling of the ECM (decreased heparanase expression) resulting in the production of homogenous (21 kDa) HS chain. With the HSPG glypican-3 expression strongly upregulated in these processes, siRNA was used to knockdown this gene to examine the effect on osteogenic commitment. Reduced glypican-3 abrogated the expression of Runx2, and thus differentiation. The reintroduction of this HSPG into Runx2-null cells allowed osteogenesis to proceed. These results demonstrate the dependence of osteogenesis on specific HS chains, in particular those associated with glypican-3.
Source
J Cell Physiol. 2009 Sep;220(3):780-91. Link to article on publisher's site