title: Morphological changes and expression of MMPs and TIMPs in rabbit degenerated lateral meniscus after PCL-transection.
abstract: BACKGROUND
  Whether the expression level of MMP-1, MMP-13 and TIMP-1 has association with the degeneration of lateral meniscus after posterior cruciate ligament (PCL) fracture is poorly understood. The aim of this study was to investigate the influence of PCL fracture on lateral meniscus, including morphological changes, histological changes and roles of matrix metalloproteinase-1 (MMP-1), matrix metalloproteinase-13 (MMP-13) and tissue inhibitor of metalloproteinase-1 (TIMP-1) expression level in the secondary injury.
  
  
  METHODS
  Sixty male rabbits were used as PCL transection models and randomized into the PCL-transection side, which underwent PCL transection surgery, and the control side, which underwent PCL exposure without transection. On 4, 8, 12, 16 and 24 weeks after PCL-transection, 12 rabbits were randomly killed for H&E staining to determine the histological changes of lateral meniscus. Immunohistochemical staining was undertaken to evaluate the expression level of MMP-1, MMP-13 and TIMP-1 in lateral meniscus. The results were statistically analyzed using SPSS 15.0.
  
  
  RESULTS
  The lateral meniscus of PCL-transection side presented abnormal morphology. Histological evaluation score of meniscal degeneration in PCL-transection group was higher than that in the control group with statistical difference (P < 0.05). The expression levels of MMP-1, MMP-13 and TIMP-1 were significantly elevated in meniscus of the PCL-transection group with statistical difference (P < 0.05). MMP-1 expression displayed an increasing trend firstly then kept stable after PCL transection; MMP-13 and TIMP-1 expression displayed high level firstly then decreased in advanced stage after PCL transection.
  
  
  CONCLUSIONS
  PCL transaction may induce a coordinated response of degeneration of lateral meniscus in a time-dependent manner. The high expression level of MMP-1, MMP-13 and TIMP-1 would contribute to the degeneration of lateral meniscus after PCL transection.
authors.affiliation: Department of Orthopedics, Xiangya Hospital, Central South University Changsha 410008, Hunan, China.
authors.forename: Pengfei
authors.initials: P
authors.lastname: Lei
authors.affiliation: Department of Orthopedics, The Sixth Affiliated Hospital of Xinjiang Medical University China.
authors.forename: Rongxin
authors.initials: R
authors.lastname: Sun
authors.affiliation: Department of Orthopedics, Xiangya Hospital, Central South University Changsha 410008, Hunan, China.
authors.forename: Kanghua
authors.initials: K
authors.lastname: Li
authors.affiliation: Department of Orthopedics, Xiangya Hospital, Central South University Changsha 410008, Hunan, China.
authors.forename: Yihe
authors.initials: Y
authors.lastname: Hu
authors.affiliation: Department of Orthopedics, Xiangya Hospital, Central South University Changsha 410008, Hunan, China.
authors.forename: Zhan
authors.initials: Z
authors.lastname: Liao
keywords: MMP-1; MMP-13; PCL-transection; TIMP-1; lateral meniscus