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The role of phospholipase D in osteoblast response to titanium surface microstructure
Author(s) -
Fang Mimi,
OlivaresNavarrete Rene,
Wieland Marco,
Cochran David L.,
Boyan Barbara D.,
Schwartz Zvi
Publication year - 2009
Publication title -
journal of biomedical materials research part a
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.849
H-Index - 150
eISSN - 1552-4965
pISSN - 1549-3296
DOI - 10.1002/jbm.a.32596
Subject(s) - phospholipase d , materials science , pld2 , osteoblast , osteocalcin , osteopontin , alkaline phosphatase , phosphatidic acid , signal transduction , biochemistry , chemistry , biology , in vitro , endocrinology , phospholipid , membrane , enzyme
Biomaterial surface properties such as microtopography and energy can change cellular responses at the cell‐implant interface. Phospholipase D (PLD) is required for the differentiation of osteoblast‐like MG63 cells on machined and grit‐blasted titanium surfaces. Here, we determined if PLD is also required on microstructured/high‐energy substrates and the mechanism involved. shRNAs for human PLD1 and PLD2 were used to silence MG63 cells. Wild‐type and PLD1 or PLD1/2 silenced cells were cultured on smooth‐pretreatment surfaces (PT); grit‐blasted, acid‐etched surfaces (SLA); and SLA surfaces modified to have higher surface energy (modSLA). PLD was inhibited with ethanol or activated with 24,25‐dihydroxyvitamin‐D 3 [24R,25(OH) 2 D 3 ]. As surface roughness/energy increased, PLD mRNA and activity increased, cell number decreased, osteocalcin and osteoprotegerin increased, and protein kinase C (PKC) and alkaline phosphatase specific activities increased. Ethanol inhibited PLD and reduced surface effects on these parameters. There was no effect on these parameters after knockdown of PLD1, but PLD1/2 double knockdown had effects comparableto PLD inhibition. 24R,25(OH) 2 D 3 increased PLD activity and the production of osteocalcin and osteoprotegerin, but decreased cell number on the rough/high‐energy surfaces. These results confirm that surface roughness/energy‐induced PLD activity is required for osteoblast differentiation and that PLD2 is the main isoform involved in this pathway. PLD is activated by 24R,25(OH) 2 D 3 in a surface‐dependent manner and inhibition of PLD reduces the effects of surface microstructure/energy on PKC, suggesting that PLD mediates the stimulatory effect of microstructured/high‐energy surfaces via PKC‐dependent signaling. © 2009 Wiley Periodicals, Inc. J Biomed Mater Res, 2010