title: Mesenchymal stem cells expressing baculovirus-engineered BMP-2 and VEGF enhance posterolateral spine fusion in a rabbit model.
abstract: BACKGROUND
  Mesenchymal stem cell (MSC)-based cell therapy and gene transfer have converged and show great potential for accelerating bone healing. Gene therapy can provide more sustained expression of osteogenic factors such as bone morphogenetic protein-2 (BMP-2). We previously demonstrated that low-dose BMP-2 enhanced spinal posterolateral fusion by MSCs in a rabbit model. Herein, we genetically modified rabbit MSCs with a recombinant baculovirus encoding BMP-2 (Bac-CB) and vascular endothelial growth factor (Bac-VEGF) seeded into porous scaffolds to enhance spinal fusion.
  
  
  OBJECTIVE
  This study evaluates the success rate of the MSC-based cell therapy and gene transfer approach for single-level posterolateral spine fusion. We hypothesize that combining three-dimensional tricalcium phosphate (TCP) scaffolds and genetically modified allogeneic MSCs with baculovirus-mediated growth factor expression would increase the success rate of spinal fusion.
  
  
  METHODS
  The study design was based on an animal model (approved by the Institutional Animal Care and Use Committee) using 18 adult male New Zealand rabbits.
  
  
  METHODS
  This study included 18 male New Zealand rabbits, weighing 3.5 to 4 kg. Allogeneic bone marrow-derived MSCs were isolated and genetically modified with Bac-CB and Bac-CV seeded onto TCP scaffolds (MSC/Bac/TCP). The animals were divided into three groups according to the material implanted into the bilateral L4-L5 intertransverse space: TCP scaffold (n=6), MSC/TCP (n=6), and MSC/Bac/TCP (n=6). After 12 weeks, the rabbits were euthanized for radiographic examination, manual palpation, and histologic study.
  
  
  RESULTS
  Bilateral fusion areas in each animal were evaluated independently. The radiographic fusion rates at 12 sites were 0 of 12 in the TCP scaffold group, 4 of 12 in the MSC/TCP group, and 10 of 12 in the MSC/Bac/TCP group. By manual palpation, there were zero solid fusions in the TCP scaffold group, two solid fusions in the MSC/TCP group, and five solid fusions in the MSC/Bac/TCP group. Fusion rates were significantly greater in the MSC/Bac/TCP group.
  
  
  CONCLUSIONS
  The results indicate the potential of using baculovirus as a vector for gene/cell therapy approaches to improve bone healing and support the feasibility of using allogeneic MSCs for inducing bone formation and intertransverse process fusion.
authors.affiliation: Department of Orthopaedic Surgery, Keelung Chang Gung Memorial Hospital, Chang Gung University, 7F, No. 222, Maijin Rd, Keelung 20401, Taiwan. Electronic address: fts111@adm.cgmh.org.tw.
authors.forename: Tsai-Sheng
authors.initials: TS
authors.lastname: Fu
authors.affiliation: Department of Orthopaedic Surgery, Linkou Chang Gung Memorial Hospital, Chang Gung University, No. 5, Fusing St., Gueishan, Taoyuan 333, Taiwan.
authors.forename: Yu-Han
authors.initials: YH
authors.lastname: Chang
authors.affiliation: Department of Orthopaedic Surgery, Keelung Chang Gung Memorial Hospital, Chang Gung University, 7F, No. 222, Maijin Rd, Keelung 20401, Taiwan.
authors.forename: Chak-Bor
authors.initials: CB
authors.lastname: Wong
authors.affiliation: Department of Orthopaedic Surgery, Keelung Chang Gung Memorial Hospital, Chang Gung University, 7F, No. 222, Maijin Rd, Keelung 20401, Taiwan.
authors.forename: I-Chun
authors.initials: IC
authors.lastname: Wang
authors.affiliation: Department of Orthopaedic Surgery, Linkou Chang Gung Memorial Hospital, Chang Gung University, No. 5, Fusing St., Gueishan, Taoyuan 333, Taiwan.
authors.forename: Tsung-Ting
authors.initials: TT
authors.lastname: Tsai
authors.affiliation: Department of Orthopaedic Surgery, Linkou Chang Gung Memorial Hospital, Chang Gung University, No. 5, Fusing St., Gueishan, Taoyuan 333, Taiwan.
authors.forename: Po-Liang
authors.initials: PL
authors.lastname: Lai
authors.affiliation: Department of Orthopaedic Surgery, Linkou Chang Gung Memorial Hospital, Chang Gung University, No. 5, Fusing St., Gueishan, Taoyuan 333, Taiwan.
authors.forename: Lih-Huei
authors.initials: LH
authors.lastname: Chen
authors.affiliation: Department of Orthopaedic Surgery, Linkou Chang Gung Memorial Hospital, Chang Gung University, No. 5, Fusing St., Gueishan, Taoyuan 333, Taiwan.
authors.forename: Wen-Jer
authors.initials: WJ
authors.lastname: Chen
mesh_terms: D000818:Animals; D016367:Baculoviridae / Q000235:genetics; D055396:Bone Morphogenetic Protein 2 / Q000235:genetics / Q000378:metabolism*; D015316:Genetic Therapy / Q000379:methods*; D008297:Male; D045164:Mesenchymal Stem Cell Transplantation; D059630:Mesenchymal Stem Cells / Q000378:metabolism; D010012:Osteogenesis; D011817:Rabbits; D013123:Spinal Fusion / Q000379:methods*; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics / Q000378:metabolism*
chemical_list: C525718:BMP2 protein, human; D055396:Bone Morphogenetic Protein 2; D042461:Vascular Endothelial Growth Factor A
keywords: Baculovirus; Bone regeneration; Gene therapy; Mesenchymal stem cells; Posterolateral fusion; Tricalcium phosphate