title: Up-Regulation of TGF-β Promotes Tendon-to-Bone Healing after Anterior Cruciate Ligament Reconstruction using Bone Marrow-Derived Mesenchymal Stem Cells through the TGF-β/MAPK Signaling Pathway in a New Zealand White Rabbit Model.
abstract: OBJECTIVE
  This study aimed to explore the role of TGF-β in tendon-to-bone healing after anterior cruciate ligament (ACL) reconstruction using bone marrow-derived mesenchymal stem cells (BMSCs) through the TGF-β/MAPK signaling pathway in a New Zealand white rabbit model.
  
  
  METHODS
  A total of 72 healthy male New Zealand white rabbits were selected for these experiments. Flow cytometry and immunofluorescence were used to detect the expression of BMSC surface markers, and qRT-PCR was performed to detect TGF-β mRNA expression. The ACL reconstruction model was established with autografts. The rabbits were randomly divided into the following groups: inhibition of TGF-β (inhibition), over-expression of TGF-β (over-expression), empty vector and untreated (n = 18 per group). Hematoxylineosin (HE) staining, toluidine blue staining and Masson trichrome staining were conducted to observe any chondrocyte-like cell growth, and biomechanical tests were used to calculate the maximum load and rigidity. Three-dimensional CT imaging and Western blotting were applied to detect changes in bone tunnel size and bone density and the expression levels of TGF-β/MAPK signaling pathway-related proteins, respectively.
  
  
  RESULTS
  CD90 and CD44 were positively expressed, while CD11b was not detected. Compared with the empty vector and untreated groups, TGF-β mRNA expression was significantly decreased in the inhibition group but increased in the over-expression group; the latter group had a larger number of fibroblasts, a tighter tendon-bone interface, an increased number of chondrocyte-like cells and fibrochondrocytes, and more collagen fibers than the inhibition, empty vector and untreated groups. Compared with the empty vector and untreated groups, the maximum load and rigidity; the CT values of bone tunnel and bone tunnel margin; and the protein expression levels of TGF-β, p-ERK1/2, p-p38, p-JNK, c-jun and c-myc were significantly down-regulated in the inhibition group but up-regulated in the over-expression group.
  
  
  CONCLUSIONS
  Our study indicated that up-regulating TGF-β expression in BMSCs from New Zealand white rabbits could promote tendon-to-bone healing after ACL reconstruction by regulating the TGF-β/MAPK signaling pathway.
authors.forename: Rui
authors.initials: R
authors.lastname: Wang
authors.forename: Bin
authors.initials: B
authors.lastname: Xu
authors.forename: Hong-Gang
authors.initials: HG
authors.lastname: Xu
mesh_terms: D000818:Animals; D059549:Anterior Cruciate Ligament Reconstruction; D001854:Bone Marrow Cells / Q000166:cytology; D002478:Cells, Cultured; D004195:Disease Models, Animal; D018960:Hyaluronan Receptors / Q000378:metabolism; D007592:Joint Diseases / Q000628:therapy*; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000378:metabolism / Q000502:physiology*; D008297:Male; D045164:Mesenchymal Stem Cell Transplantation; D059630:Mesenchymal Stem Cells / Q000166:cytology / Q000378:metabolism; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D011817:Rabbits; D015398:Signal Transduction; D013710:Tendons / Q000378:metabolism*; D018800:Thy-1 Antigens / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000235:genetics / Q000378:metabolism*; D014182:Transplantation, Autologous; D015854:Up-Regulation; D014945:Wound Healing / Q000502:physiology*
chemical_list: D018960:Hyaluronan Receptors; D018800:Thy-1 Antigens; D016212:Transforming Growth Factor beta; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3
keywords: Anterior cruciate ligament reconstruction; Bone marrow-derived mesenchymal stem cell ; TGF-β; TGF-β/MAPK signaling pathway; Tendon-to-bone healing