title: The effect of bone morphogenic protein-2-coated tri-calcium phosphate/hydroxyapatite on new bone formation in a rat model of femoral distraction osteogenesis.
abstract: OBJECTIVE
  Distraction osteogenesis (DO) is an increasingly popular technique used to stimulate new bone formation to treat orthopedic disorders resulting from bone defects and deficits. Because of various possible complications that can occur during the long consolidation period, the development of procedures to accelerate regenerated ossification is clearly desirable. The purpose of this study was to evaluate the effect of single insertions of bone morphogenic protein-2 (BMP-2), delivered by tri-calcium phosphate (TCP)/hydroxyapatite (HA), administered at osteotomy sites, on the rate of new bone formation during DO in a rat model.
  
  
  METHODS
  Thirty-six male Sprague-Dawley rats, aged 12 weeks and weighing a mean (± standard deviation) of 401 ± 14 g, were used in this study. The animals were randomized into three groups of 12 rats each. Group I served as a control, group II was treated with only TCP/HA, and group III was treated with recombinant human (rh) BMP-2-coated TCP/HA. Materials were inserted into the medullary canal at the femoral osteotomy site at the end of the lengthening period. After a 7-day latent phase, distraction was commenced on day 0 at a rate of 0.50 mm every 6 h for 5 days (2 mm daily), resulting in a total of 10 mm of lengthening by day 5. At two different time-points [at 4 weeks (day 33) and 8 weeks (day 61) after cessation of distraction], the progress of bone formation was determined with microcomputed tomography (micro-CT), histology and real-time polymerase chain reaction (PCR). The mean and standard deviation of the values obtained from the experiment were computed and statistical analyses performed using anova. Statistical significance was established at P < 0.05. Results. Radiographically, all group III rat femurs exhibited bridging callus formation 8 weeks after cessation of distraction, whereas group II rat femurs demonstrated non-bridging callus formation. None of the group I rat femurs showed callus in the central zone of the distraction gap. For micro-CT, bone formation and remodeling of the distraction regeneration with beta-TCP/HA coated with rhBMP-2 had greater values than the control sides at all time-points. Two-dimensional quantitative analysis of the distraction regeneration showed that the bone volume of group III had higher values than groups I and II at 4 weeks (P < 0.05). This difference was also evident at 8 weeks. With hematoxylin and eosin (H&E) staining, the control group (group I) did not show any bone tissue at the distraction site. In group II at 4 weeks, abundant fibrous tissue surrounding the particles was visible with some areas of woven bone. At 8 weeks, the woven bone covered the particles but not the whole circumference. In group III at 4 weeks, much of the woven bone surrounded the particle with some fibrocartilagenous materials. At 8 weeks, woven bone covering the whole circumference of the particles was visible.
  
  
  CONCLUSIONS
  Application of rhBMP-2, at the end of the rather rapid distraction period, as a single bolus significantly increased the osteogenic process, while beta-TCP/HA behaved effectively as a sustained delivery system for this osteoinductive protein.
authors: Department of Orthopaedic Surgery, Seoul Veterans Hospital, Seoul, Korea.
authors: Jae-Hyuk
authors: JH
authors: Yang
authors: Hak-Jun
authors: HJ
authors: Kim
authors: Sung-Eun
authors: SE
authors: Kim
authors: Young-Pil
authors: YP
authors: Yun
authors: Ji-Hoon
authors: JH
authors: Bae
authors: Seung-Ju
authors: SJ
authors: Kim
authors: Kyung-Hee
authors: KH
authors: Choi
authors: Hae-Ryong
authors: HR
authors: Song
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D055396:Bone Morphogenetic Protein 2 / Q000008:administration & dosage* / Q000494:pharmacology; D002146:Bony Callus / Q000378:metabolism / Q000473:pathology; D002130:Calcium Phosphates / Q000008:administration & dosage* / Q000494:pharmacology; D024042:Collagen Type I / Q000235:genetics / Q000378:metabolism; D016503:Drug Delivery Systems / Q000379:methods; D017886:Durapatite / Q000008:administration & dosage / Q000494:pharmacology; D004801:Eosine Yellowish-(YS) / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D005269:Femur / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery; D006416:Hematoxylin / Q000378:metabolism; D006801:Humans; D008297:Male; D008855:Microscopy, Electron, Scanning; D010012:Osteogenesis; D019857:Osteogenesis, Distraction / Q000379:methods*; D053495:Osteopontin / Q000235:genetics / Q000378:metabolism; D010027:Osteotomy; D051381:Rats; D017207:Rats, Sprague-Dawley; D011994:Recombinant Proteins / Q000008:administration & dosage / Q000494:pharmacology; D013194:Staining and Labeling; D013997:Time Factors; D016212:Transforming Growth Factor beta / Q000008:administration & dosage* / Q000494:pharmacology; D055114:X-Ray Microtomography
chemical_list: D055396:Bone Morphogenetic Protein 2; D002130:Calcium Phosphates; D024042:Collagen Type I; D011994:Recombinant Proteins; C506897:Spp1 protein, rat; D016212:Transforming Growth Factor beta; C485817:beta-tricalcium phosphate; C499469:recombinant human bone morphogenetic protein-2; D053495:Osteopontin; D017886:Durapatite; D004801:Eosine Yellowish-(YS); D006416:Hematoxylin