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The role of phospholipase D in osteoblast response to titanium surface microstructure.

ABSTRACT: 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.

SUBMITTER: Fang M

PROVIDER: S-EPMC4287411 | biostudies-literature | 2010 Jun

REPOSITORIES: biostudies-literature

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The role of phospholipase D in osteoblast response to titanium surface microstructure.

Fang Mimi M Olivares-Navarrete Rene R Wieland Marco M Cochran David L DL Boyan Barbara D BD Schwartz Zvi Z

Journal of biomedical materials research. Part A 20100601 3

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 o ...[more]

PMID: 19705469

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Project description:A critical stage during osseointegration of a titanium (Ti) implant is primary bone remodeling, which involves cross talk among osteoclast precursors, osteoclasts, mesenchymal stem cells (MSCs), and osteoblasts. This phase couples the processes of bone formation and resorption. During remodeling, osteoclasts produce factors capable of regulating MSC migration and osteogenesis. Furthermore, they degrade primary bone, creating a foundation with a specific chemistry, stiffness, and morphology for osteoblasts to synthesize and calcify their matrix. MSCs and osteoblasts receiving cues from the implant surface produce factors capable of regulating osteoclasts in order to promote net new bone formation. The purpose of this study was to determine the effects Ti implant surfaces have on bone remodeling. Human MSCs and normal human osteoblasts (NHOsts) were cultured separately on 15 mm grade 2 smooth PT, hydrophobic-microrough SLA, hydrophilic-microrough Ti (mSLA) (Institut Straumann AG, Basel, Switzerland), or tissue culture polystyrene (TCPS). After 7d, conditioned media from surface cultures were used to treat human osteoclasts for 2d. Activity was measured by fluorescence of released collagen followed by mRNA quantification. This study demonstrates that MSC and NHOst cultures are able to suppress osteoclast activity in a surface dependent manner and osteoclast mRNA levels are selectively regulated by surface treatments. The substrate-dependent regulatory effect was mitigated when MSCs were silenced for integrin subunits and when conditioned media were denatured. These results indicate that MSCs and NHOsts regulate at least two aspects of remodeling: reduced fusion of new osteoclasts and reduced activity of existing osteoclasts. STATEMENT OF SIGNIFICANCE:In this study, we developed a novel in vitro model to study how microstructured and hydrophilic titanium implants impact bone remodeling for dental and orthopaedic applications. Our approach intersects biomaterials and systems physiology, revealing for the first time that implant surface properties are capable of regulating the communication among the cells involved in remodeling of primary bone during osseointegration. We believe that the basic research presented in our manuscript will provide important knowledge in our understanding of factors that impact implant success. Furthermore, it provides a solid foundation for the development of materials that enable rapid osseointegration and earlier loading times for implants in bone that has been compromised by trauma or disease.

Dataset Information

The role of phospholipase D in osteoblast response to titanium surface microstructure.

Publications

The role of phospholipase D in osteoblast response to titanium surface microstructure.

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