title: Enhancement of meniscal repair in the avascular zone using connective tissue growth factor in a rabbit model.
abstract: BACKGROUND
  Connective tissue growth factor (CTGF) is a secreted protein containing several domains that mediate interactions with growth factors, integrins and extracellular matrix components. CTGF plays an important role in extracellular matrix production by its ability to mediate collagen deposition during wound healing. CTGF also induces neovascularization in vitro, suggesting a role in angiogenesis in vivo. We herein evaluated whether CTGF was required for extracellular matrix synthesis of meniscal fibrochondrocytes and/or angiogenesis during the repair of meniscal tears.
  
  
  METHODS
  Meniscal fibrochondrocytes were isolated from the inner-1/2 of rabbit meniscus by trypsin collagenase treatment and further treated with 100 ng/ml CTGF in vitro. Characterization of fibrochondrocytes was identified by flow cytometry analyzing CD31, CD44, CD45 and CD105, and was further tested by type II collagen immunocytochemistry. Changes in gene expression of meniscal fibrochondrocytes were monitored by quantitative real-time polymerase chain reaction. Histological sections prepared from a 3-mm portion of a longitudinal tearing defect in the middle of the rabbit meniscus were subjected to fluorescence-immunohistochemistry analysis at 1, 4 and 10 weeks following surgical treatment with 1.5 µg of CTGF/fibrin-glue composites.
  
  
  RESULTS
  Quantitative RT-PCR assay showed that types I and II collagen and vascular endothelial growth factor mRNA expression in the 100 ng/ml CTGF group were remarkably enhanced as compared to levels in the no-dose group at 14 days ((2.38 ± 0.63) fold, (2.96 ± 0.87) fold, (2.14 ± 0.56) fold, respectively). Likewise, fluorescence-immunohistochemical analysis revealed that in the group implanted with CTGF-fibrin glue, types I and II collagen, as well as the capillaries, completely filled the defect by 10 weeks, postoperatively. In contrast, only soft tissue repair occurred when PBS-fibrin glue was implanted.
  
  
  CONCLUSIONS
  These findings suggest that CTGF can significantly promote extracellular matrix deposition (types I and II collagen) within the meniscal avascular zone; CTGF can greatly heighten the expression of vascular endothelial growth factor activity simultaneously in vivo, further enhancing the repair of meniscal tears in the avascular zone.
authors.affiliation: Department of Orthopedic Surgery, General Hospital of Chinese People's Liberation Army, Beijing 100853, China.
authors.forename: Wei
authors.initials: W
authors.lastname: He
authors.forename: Yu-Jie
authors.initials: YJ
authors.lastname: Liu
authors.forename: Zhi-Gang
authors.initials: ZG
authors.lastname: Wang
authors.forename: Zi-Kuan
authors.initials: ZK
authors.lastname: Guo
authors.forename: Ming-Xin
authors.initials: MX
authors.lastname: Wang
authors.forename: Ning
authors.initials: N
authors.lastname: Wang
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D019902:Chondrocytes / Q000166:cytology; D024042:Collagen Type I / Q000378:metabolism; D024043:Collagen Type II / Q000378:metabolism; D055513:Connective Tissue Growth Factor / Q000494:pharmacology*; D005434:Flow Cytometry; D007150:Immunohistochemistry; D008297:Male; D008592:Menisci, Tibial / Q000166:cytology*; D011817:Rabbits; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000070600:Tibial Meniscus Injuries; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism; D014945:Wound Healing / Q000187:drug effects*
chemical_list: D024042:Collagen Type I; D024043:Collagen Type II; D042461:Vascular Endothelial Growth Factor A; D055513:Connective Tissue Growth Factor