The heparan sulfate proteoglycan (HSPG) glypican-3 mediates commitment of MC3T3-E1 cells toward osteogenesis.
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.
Haupt
Larisa M
LM
Stem Cells and Tissue Repair Group, Institute of Medical Biology, A*STAR (Agency for Science, Technology and Research), Biopolis 138648, Singapore.
Murali
Sadasivam
S
Mun
Foong Kin
FK
Teplyuk
Nadiya
N
Mei
Leong Fong
LF
Stein
Gary S
GS
van Wijnen
Andre J
AJ
Nurcombe
Victor
V
Cool
Simon M
SM
D016475:3T3 Cells; D000818:Animals; D058578:Biglycan; D055396:Bone Morphogenetic Protein 2 / Q000378:metabolism; D002454:Cell Differentiation / Q000235:genetics; D019070:Cell Lineage / Q000235:genetics; D049109:Cell Proliferation; D050659:Core Binding Factor Alpha 1 Subunit / Q000235:genetics / Q000378:metabolism; D058575:Decorin; D016326:Extracellular Matrix Proteins / Q000378:metabolism; D016222:Fibroblast Growth Factor 2 / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D053673:Glypicans / Q000235:genetics / Q000378:metabolism*; D019763:Heparin Lyase / Q000235:genetics / Q000378:metabolism; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D010006:Osteoblasts / Q000201:enzymology / Q000378:metabolism*; D010012:Osteogenesis / Q000235:genetics; D011499:Protein Processing, Post-Translational; D011509:Proteoglycans / Q000378:metabolism; D034622:RNA Interference; D012333:RNA, Messenger / Q000378:metabolism; D017468:Receptors, Fibroblast Growth Factor / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D015238:Sulfotransferases / Q000235:genetics / Q000378:metabolism; D013997:Time Factors; D014162:Transfection; D053675:Versicans / Q000378:metabolism
C546884:BGN protein, human; C546885:Bgn protein, mouse; D058578:Biglycan; D055396:Bone Morphogenetic Protein 2; D050659:Core Binding Factor Alpha 1 Subunit; C546878:DCN protein, human; C546879:Dcn protein, mouse; D058575:Decorin; D016326:Extracellular Matrix Proteins; D053673:Glypicans; D011509:Proteoglycans; D012333:RNA, Messenger; D017468:Receptors, Fibroblast Growth Factor; D011994:Recombinant Proteins; C493716:Runx2 protein, mouse; C508323:Vcan protein, mouse; D016222:Fibroblast Growth Factor 2; D053675:Versicans; D015238:Sulfotransferases; D019763:Heparin Lyase