title: Minimal invasive annulotomy for induction of disc degeneration and implantation of poly (lactic-co-glycolic acid) (PLGA) plugs for annular repair in a rabbit model.
abstract: BACKGROUND
  The rabbit disc model is useful for the study of intervertebral disc (IVD) degeneration and experimental therapeutic interventions. The annulotomy-induced disc models present several drawbacks, particularly an excessive disruption of disc integrity and a rapidly disc degeneration; therefore, this study sought to establish a minimal invasive annulotomy for induction of disc degeneration model, combined to annulus repair using implantation of a PLGA (poly lactic-co-glycolic acid) plug.
  
  
  METHODS
  New Zealand white rabbits (n = 24) received annular injuries in three discs (L3/4, L4/5 and L5/6). The experimental discs were randomly assigned to four groups: (a) annular defect with a 1.8 mm diameter mini-trephine; (b) annular puncture by 16G needle; (c) annular defect with a PLGA plug implanted by press-fit fashion; (d) uninjured L2/3 disc served as control. Postsurgical x-ray, MRI examination, and real-time PCR analysis were performed at 1, 3 and 6 months. Gross morphology and histology were evaluated at postoperative 6 months.
  
  
  RESULTS
  Radiographic examinations showed a slow, progressive disc space narrowing and a significant degree of disc degeneration on MRI grade in the injured discs at 6 months in all rabbits. Histological examinations and aggrecan, Col1A1, Col2A1 and matrix metalloprotease (MMP)-3 mRNA expression confirmed the disc degeneration, supporting the imaging results. The PLGA implantation reduced the marked loss of T2-weighted signal intensity seen at MRI in the injured discs and slowly decreased the disc height index (DHI) over the follow-up period. HE/Safranin O staining showed that annular defect was replaced by regenerated connective tissue with significant loss of proteoglycan content.
  
  
  CONCLUSIONS
  The minimally invasive approach for the creation of annular defects by an appropriately sized mini-Trephine is a suitable option for the study of disc degeneration in a rabbit model. Implantation of a suitable PLGA plug induced a successful repair of the annulus fibrosus within the degenerated disc, and retarded the degenerative process in the annular injury model.
authors.affiliation: Clinical Laboratory, Department of Orthopedics, Tongde Hospital of Zhejiang Province, Hangzhou, China. xinlonghz@gmail.com.
authors.forename: Long
authors.initials: L
authors.lastname: Xin
authors.affiliation: Clinical Laboratory, Department of Orthopedics, Tongde Hospital of Zhejiang Province, Hangzhou, China. xinlonghz@aliyun.com.
authors.forename: Chun
authors.initials: C
authors.lastname: Zhang
authors.affiliation: Clinical Laboratory, Department of Orthopedics, Tongde Hospital of Zhejiang Province, Hangzhou, China. walker2004@sohu.com.
authors.forename: Fuhua
authors.initials: F
authors.lastname: Zhong
authors.affiliation: Department of Orthopaedic Surgery, Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, Hangzhou, China. racer2004@sina.com.
authors.forename: Shunwu
authors.initials: S
authors.lastname: Fan
authors.affiliation: Department of Polymer Science and Engineering, Zhejiang University, Hangzhou, China. wwgfz@tju.edu.cn.|Department of Polymer Materials Science and Engineering, Tianjin University, Tianjin, China. wwgfz@tju.edu.cn.
authors.forename: Wei
authors.initials: W
authors.lastname: Wang
authors.affiliation: Clinical Laboratory, Department of Spine Surgery, The Fourth Affiliated Hospital of Xinjiang Medical University, Urumqi, 830000, China. wangzb0202@163.com.
authors.forename: Zhenbin
authors.initials: Z
authors.lastname: Wang
mesh_terms: D053674:Aggrecans / Q000235:genetics; D000818:Animals; D001672:Biocompatible Materials / Q000494:pharmacology; D024042:Collagen Type I / Q000235:genetics; D024043:Collagen Type II / Q000235:genetics; D004195:Disease Models, Animal; D017586:Diskectomy / Q000009:adverse effects / Q000295:instrumentation / Q000379:methods; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D020007:Implants, Experimental; D007403:Intervertebral Disc / Q000187:drug effects* / Q000293:injuries / Q000378:metabolism; D055959:Intervertebral Disc Degeneration / Q000000981:diagnostic imaging / Q000188:drug therapy* / Q000209:etiology; D019344:Lactic Acid / Q000494:pharmacology*; D008279:Magnetic Resonance Imaging; D019278:Matrix Metalloproteinase 3 / Q000235:genetics; D019060:Minimally Invasive Surgical Procedures / Q000009:adverse effects / Q000295:instrumentation / Q000379:methods; D011100:Polyglycolic Acid / Q000494:pharmacology*; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011817:Rabbits; D011859:Radiography; D011897:Random Allocation; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D053674:Aggrecans; D001672:Biocompatible Materials; D024042:Collagen Type I; D024043:Collagen Type II; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011100:Polyglycolic Acid; D019344:Lactic Acid; D019278:Matrix Metalloproteinase 3