Injection of AAV2-BMP2 and AAV2-TIMP1 into the nucleus pulposus slows the course of intervertebral disc degeneration in an in vivo rabbit model

Abstract

BACKGROUND CONTEXT Intervertebral disc degeneration (IDD) is a common cause of back pain. Patients who fail conservative management may face the morbidity of surgery. Alternative treatment modalities could have a significant impact on disease progression and patients’ quality of life. PURPOSE To determine if the injection of a virus vector carrying a therapeutic gene directly into the nucleus pulposus improves the course of IDD. STUDY DESIGN Prospective randomized controlled animal study. METHODS Thirty-four skeletally mature New Zealand white rabbits were used. In the treatment group, L2–L3, L3–L4, and L4–L5 discs were punctured in accordance with a previously validated rabbit annulotomy model for IDD and then subsequently treated with adeno-associated virus serotype 2 (AAV2) vector carrying genes for either bone morphogenetic protein 2 (BMP2) or tissue inhibitor of metalloproteinase 1 (TIMP1). A nonoperative control group, nonpunctured sham surgical group, and punctured control group were also evaluated. Serial magnetic resonance imaging (MRI) studies at 0, 6, and 12 weeks were obtained, and a validated MRI analysis program was used to quantify degeneration. The rabbits were sacrificed at 12 weeks, and L4–L5 discs were analyzed histologically. Viscoelastic properties of the L3–L4 discs were analyzed using uniaxial load normalized displacement testing. Creep curves were mathematically modeled according to a previously validated two-phase exponential model. Serum samples obtained at 0, 6, and 12 weeks were assayed for biochemical evidence of degeneration. RESULTS The punctured group demonstrated MRI and histologic evidence of degeneration as expected. The treatment groups demonstrated less MRI and histologic evidence of degeneration than the punctured group. The serum biochemical marker C-telopeptide of collagen type II increased rapidly in the punctured group, but the treated groups returned to control values by 12 weeks. The treatment groups demonstrated several viscoelastic properties that were distinct from control and punctured values. CONCLUSIONS Treatment of punctured rabbit intervertebral discs with AAV2-BMP2 or AAV2-TIMP1 helps delay degenerative changes, as seen on MRI, histologic sampling, serum biochemical analysis, and biomechanical testing. Although data from animal models should be extrapolated to the human condition with caution, this study supports the potential use of gene therapy for the treatment of IDD.

Efficacy of intradiscal hepatocyte growth factor injection for the treatment of intervertebral disc degeneration

“…In a rabbit annular stab-injury model, there was a relative decrease in BMP-2 mRNA levels, followed by a consequent increase close to the preoperative levels (20). In a prospective, randomized controlled animal study, injection of the BMP-2 gene delayed degenerative changes in a rabbit disc puncture model (23). Our results demonstrated that the number of BMP-2-positive cells in the AF increased following treatment with HGF, whereas a strong positive staining of BMP-2 was only observed in cells at the disrupted border in the AF of stab-injury only and gel alone-treated segments, suggesting that HGF promotes BMP-2-induced repair in degenerative discs.…”

Molecular Basis of Intervertebral Disc Degeneration and Herniations: What Are the Important Translational Questions?

“…BMP-2 and BMP-7 (osteogenic protein 1) act to increase proteoglycan production, specifically aggrecan and collagen types I and II in AF and NP cells [11,37,47]. Local injection of degenerative discs with BMP-2 and BMP-7 has been reported to maintain disc height and increase production of proteoglycans in both rat and rabbit models [3,31,34,41,58]. Despite successful demonstration of increased proteoglycan and collagen content, BMPs also cause ossification of the annulus and aberrant bone formation [29,35].…”

“…In vivo transfection of intervertebral disc cells with an adenoviral vector containing the TGF-b1 gene resulted in increased TGF-b1 expression and proteoglycan synthesis [65]. Also, successful delivery of an adeno-associated virus encoded with genes for the proanabolic molecule BMP-2 and anticatabolic molecule tissue inhibitor of matrix metalloproteinases 1 showed decreased MRI, histologic, serum biochemical, and biomechanical evidence of disc degeneration over a 12-week period [41].…”

MMPs and ADAMTSs in intervertebral disc degeneration

“…Gene delivery of TIMP-1 has been shown to enhance proteoglycan synthesis in human degenerate IVD cells [117]. In a in vivo rabbit model of IDD, injection of adenoassociated virus serotype 2 (AAV2) vector carrying TIMP-1 gene into NP tissue remarkably enhances Col II content in the discs, followed up less MRI and histologic evidence of degeneration [118]. These data further confirm that an increased ECM production contributes to the delay of IDD progression.…”