Abstract
BackgroundThe 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.MethodsNew 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.ResultsRadiographic 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.ConclusionsThe 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.
Highlights
The rabbit disc model is useful for the study of intervertebral disc (IVD) degeneration and experimental therapeutic interventions
In the Poly lactic-co-glycolic acid (PLGA) implantation group, brown repair tissue filled in the defect and was well integrated into the surrounding annulus, while no obvious scar tissue was visible in the sagittal plane
In an attempt to minimize the damage to the annular integrity and to accomplish a minimally invasive annulotomy, we and successfully designed a mini-trephine that created a defect by removing the annulus fibrosus (AF) in the annular injury model
Summary
The rabbit disc model is useful for the study of intervertebral disc (IVD) degeneration and experimental therapeutic interventions. Full-thickness AF injury using stab or puncture technique is popular and reproducible models in small animals [6,7,8,9]. These procedures, carry the risk of serious side effects such as undesirable osteophyte and overly rapid disc degeneration processes that less closely reflect the chronic course of clinical setting [10,11,12]. A goal of this study was to perform a minimally invasive annulotomy with limited annulus trauma For this purpose, an appropriately sized mini-trephine was designed for the partial removal of the AF and consequent induction of IVD degeneration
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