title: Polymethylmethacrylate particles impair osteoprogenitor viability and expression of osteogenic transcription factors Runx2, osterix, and Dlx5.
abstract: Polymethylmethacrylate (PMMA) particles have been shown to inhibit the differentiation of osteoprogenitor cells, but the mechanism of this inhibitory effect has not been investigated. We hypothesize that the inhibitory effects of PMMA particles involve impairment of osteoprogenitor viability and direct inhibition of transcription factors that regulate osteogenesis. We challenged MC3T3-E1 osteoprogenitors with PMMA particles and examined the effects of these materials on osteoprogenitor viability and expression of transcription factors Runx2, osterix, Dlx5, and Msx2. MC3T3-E1 cells treated with PMMA particles over a 72-h period showed a significant reduction in cell viability and proliferation as indicated by a dose- and time-dependent increase in supernatant levels of lactate dehydrogenase, an intracellular enzyme released from dead cells, a dose-dependent decrease in cell number and BrdU uptake, and the presence of large numbers of positively labeled Annexin V-stained cells. The absence of apoptotic cells on TUNEL assay indicated that cell death occurred by necrosis, not apoptosis. MC3T3-E1 cells challenged with PMMA particles during the first 6 days of differentiation in osteogenic medium showed a significant dose-dependent decrease in the RNA expression of Runx2, osterix, and Dlx5 on all days of measurement, while the RNA expression of Msx2, an antagonist of Dlx5-induced osteogenesis, remained relatively unaffected. These results indicate that PMMA particles impair osteoprogenitor viability and inhibit the expression of transcription factors that promote osteoprogenitor differentiation.
authors.affiliation: Department of Orthopaedic Surgery, Stanford University Medical Center, 300 Pasteur Drive, Edwards Building, R-116, Stanford, California 94305-5341, USA.
authors.forename: Richard
authors.initials: R
authors.lastname: Chiu
authors.forename: Kierann E
authors.initials: KE
authors.lastname: Smith
authors.forename: Gene K
authors.initials: GK
authors.lastname: Ma
authors.forename: Ting
authors.initials: T
authors.lastname: Ma
authors.forename: R Lane
authors.initials: RL
authors.lastname: Smith
authors.forename: Stuart B
authors.initials: SB
authors.lastname: Goodman
mesh_terms: D016475:3T3 Cells; D000818:Animals; D017304:Annexin A5 / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects; D001843:Bone Cements / Q000633:toxicity; D001862:Bone Resorption / Q000139:chemically induced / Q000503:physiopathology; D002454:Cell Differentiation / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D050659:Core Binding Factor Alpha 1 Subunit / Q000235:genetics*; D004305:Dose-Response Relationship, Drug; D015870:Gene Expression / Q000187:drug effects; D018398:Homeodomain Proteins / Q000235:genetics*; D051379:Mice; D010011:Osteocytes / Q000166:cytology*; D019904:Polymethyl Methacrylate / Q000633:toxicity*; D011475:Prosthesis Failure; D012333:RNA, Messenger / Q000378:metabolism; D000076182:Sp7 Transcription Factor; D013234:Stem Cells / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D014157:Transcription Factors / Q000235:genetics*
chemical_list: D017304:Annexin A5; D001843:Bone Cements; D050659:Core Binding Factor Alpha 1 Subunit; C501120:Dlx5 protein, mouse; D018398:Homeodomain Proteins; C084119:MSX2 protein; D012333:RNA, Messenger; C493716:Runx2 protein, mouse; D000076182:Sp7 Transcription Factor; C479466:Sp7 protein, mouse; D014157:Transcription Factors; D019904:Polymethyl Methacrylate