737 Orthosilicic Acid Enhances Collagen Formation Through OSX Transcription

Friday, March 23, 2012: 10:45 a.m. - 12:15 p.m.
Presentation Type: Oral Session
J. CHENG1, L.M. DOMINIA1, G. MARSHALL2, P. LOOMER1, and V. VARANASI3, 1Division of Periodontology, University of California - San Francisco, San Francisco, CA, 2Preventive and Restorative Dent Sci, University of California - San Francisco, San Francisco, CA, 3Baylor College of Dentistry, Texas A & M Health Science Center, Dallas, TX
Objective: Bioactive glasses release Si4+ (0.1mM), which enhances osteoblast formation of collagen fibers during osteogenesis.  Collagen fiber bundle shape and size is controlled by the expression of collagen type 5 (Col(V)α3), which is regulated by osterix (OSX) transcription. Thus, it is hypothesized that Si4+ enhances collagen expression through enhanced OSX transcription. 

Method: 0.1 mM Si4+ treatments were prepared by dissolving Na2SiO3 in basal medium (α-MEM, 10% fetal bovine serum, 1% penicillin–streptomycin, 50 mg L-1 ascorbic acid (control medium)). Osteoblasts (MC3T3-E1 subclone 4) were treated with (1) control medium, (2) control medium after OSX siRNA knockdown, (3) Si4+ treated control medium, and (4) Si4+ treated control medium after OSX siRNA knockdown.  Cells were cultured for 3 days, lysed for mRNA, converted to cDNA, and amplified for OSX and Col(V)α3 relative expression using qPCR.  Cells on cover slips were cultured for 6 days under treatments (1) and (3), fixed, stained (Picrosirius Red) and imaged for collagen fiber bundle formation using polarized light microscopy.

Result: Si4+ treatments induced a two-fold increase in OSX and Col(V)α3 expression after 3 days in culture relative to control treated cells. When OSX siRNA knockdown was applied to osteoblasts, Si4+ treatments did not enhance the expression of OSX or Col(V)α3. Imaging results revealed increased density of collagen fiber bundle formation in Si4+ treatments after 6 days as compared to control treatments.  

Conclusion: Si4+ treatments enhanced collagen ECM formation through the enhanced expression of OSX transcription and Col(V)α3 gene expression.

This abstract is based on research that was funded entirely or partially by an outside source: NIH/NIDCR 5P30DE020742-02

Keywords: Biomaterials, Collagen, Gene expression and Osteoblasts/osteoclasts