title: Mechanical loading influences the effects of bisphosphonates on human periodontal ligament fibroblasts.
abstract: OBJECTIVE
  There is increasing evidence that bisphosphonates affect orthodontic tooth movement. The object of the study was to investigate the changes produced by tensile strain on human periodontal ligament fibroblasts (HPdLFs) treated with clodronate or zoledronate.
  
  
  METHODS
  HPdLF were cultured with 5 and 50 μM clodronate or zoledronate for 48 h and applied to tensile strain (TS) (5 and 10 %) for 12 h in vitro. Viability was verified by MTT assay and apoptosis rate via caspase 3/7 assay. Gene expression of receptor activator of nuclear factor kappa-B ligand (RANKL) and osteoprotegerin (OPG) was investigated using real-time PCR. OPG was also analyzed by ELISA and RANKL by immunocytochemical staining.
  
  
  RESULTS
  Zoledronate (50 μM) reduced the viability of HPdLF (76 vs 100 %) and combined with 5 % TS to 53 %. TS of 10 % and clodronate reduced viability to 79 % with increased caspase 3/7 activity. Clodronate (5 μM) led to a slight increase of OPG gene expression, zoledronate (5 μM) to a slight decrease. Combined with 5 % TS, both increased OPG gene expression (2-3-fold) and OPG synthesis. Zoledronate increased gene expression of RANKL (4-fold). Combined with 5 % of TS, this increase was abolished. TS of 10 % in combination amplified increase of RANKL ending up with a 9-fold gene expression by clodronate and high RANKL protein synthesis.
  
  
  CONCLUSIONS
  This study shows for the first time that mechanical loading alters the effects of bisphosphonates on viability, apoptosis rate, and OPG/RANKL system of HPdLF dependent on the applied strength. Low forces and bisphosphonates increase factors for bone apposition, whereas high forces combined with bisphosphonates stimulate osteoclastogenesis.
  
  
  CONCLUSIONS
  Mechanical loading of periodontal ligament with high strengths should be avoided during bisphosphonate therapy.
authors: Department of Orthodontics, Medical Center, Johannes Gutenberg of University Mainz, Augustusplatz 2, 55131, Mainz, Germany, collin.jacobs@unimedizin-mainz.de.
authors: Collin
authors: C
authors: Jacobs
authors: Christian
authors: C
authors: Walter
authors: Thomas
authors: T
authors: Ziebart
authors: Isabelle
authors: I
authors: Dirks
authors: Sabrina
authors: S
authors: Schramm
authors: Sarah
authors: S
authors: Grimm
authors: Elena
authors: E
authors: Krieger
authors: Heinrich
authors: H
authors: Wehrbein
mesh_terms: D017209:Apoptosis; D050071:Bone Density Conservation Agents / Q000494:pharmacology*; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D004002:Clodronic Acid / Q000494:pharmacology*; D004164:Diphosphonates / Q000494:pharmacology*; D004797:Enzyme-Linked Immunosorbent Assay; D005347:Fibroblasts / Q000187:drug effects*; D015870:Gene Expression; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology*; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D053244:Osteoprotegerin / Q000235:genetics / Q000378:metabolism; D010513:Periodontal Ligament / Q000166:cytology* / Q000187:drug effects; D053245:RANK Ligand / Q000235:genetics / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D013314:Stress, Mechanical; D014087:Tooth Movement Techniques; D000077211:Zoledronic Acid
chemical_list: D050071:Bone Density Conservation Agents; D004164:Diphosphonates; D007093:Imidazoles; D053244:Osteoprotegerin; D053245:RANK Ligand; D004002:Clodronic Acid; D000077211:Zoledronic Acid