To Evaluate Bone Morphogenetic Protein-2 Effects In Range Of Motion Of Functional Spinal Unit Of Rabbit's Lumbar Spine

Objectives: To prove anterolateral extraperitoneal anular stab is not only a simple and practicable but also a successful way to constructn a slowly progressive, reproducible rabbit model of intervertebral disc degeneration.Methods: In the experiment, we anticipated 24 New Zealand rabbits would be used. Actually, 26 rabbits were used in the experiment because 2 rabbits had to quit because of unforeseen situation. Three rabbits were killed promptly to provide intact disc specimens and collected radioloty and histology data for comparison with the preoperative state of discs. After general anesthesia, the L2-L3, L3-L4, and L4-L5 lumbar intervertebral discs of remaining 21 skeletally mature female New Zealand White rabbits were stabbed by 16-gauge hypodermic needle to a depth of 5 mm in the left anterolateral annulus fibrosus. All experimental rabbits were performed serial magnetic resonance imaging scan in the stabbed discs and intact L1-L2 and L5-L6 control discs at 3, 6, 12, and 24 weeks post surgery. Three rabbits were chosen randomly each time supplemental radiograph and histologic analyses (Remain 9 rabbits were used in the secondary stage experiment) . At the same time, whole results were compared with preoperative observation results.Results: Radiograph findings included early osteophyte formation in adjacent intervertebral by 6 weeks post stab and extensive, bridging osteophytes by 24 weeks. The stabbed discs exhibited a progressive decrease in "magnetic resonance imaging index" (the product of nucleus pulposus area and signal intensity from T2-weighted midsagittal plane images) starting at 3 weeks post stab and continuing through 24 weeks (mean MRI index was 82% of preoperative MRI index by week 3, decreasing to 31% by week 24.) , with no evidence of spontaneous recovery or reversal of magnetic resonance imaging changes. Histologic analysis revealed progressive loss of notochordal cells from the nucleus pulposus, filling of the nucleus pulposus space with fibrocartilage, and derangement of anulus fibrosus.Conclusion: Stabbing the anterolateral anulus fibrosus of adult rabbit lumbar discs with a 16-gauge hypodermic needle to a limited (5-mm) depth results in a number of slowly progressive and reproducible magnetic resonance imaging, radiograph, and histologic changes over 24 weeks that show a similarity to changes seen in human intervertebral disc degeneration. This model would appear suitable for studying pathogenesis and pathophysiology of intervertebral disc degeneration and testing safety and efficacy of novel treatments of intervertebral disc degeneration.Part II. To Evaluate Bone Morphogenetic Protein -2 Effects in Range of Motion of Functional Spinal Unit Of Rabbit's Lumbar SpineObjectives: To determine the efficacy of Bone Morphogenetic Protein-2 injection in degenerated intervertebral rabbit disc in preventing or delaying the progression of disc degeneration, it also can change the biomechanics of intervertebral disc and provide the experiments evidences for initiate a new therapy in intervertebral disc degeneration disease.Methods: Optional choosing 9 experiment rabbit were injected BMP-2 in stabbed intervertebral disc with Contralateral track in 3 weeks postoperation. At the time point of 6, 12 and 24 weeks postoperation, treatment intervertebral discs were analyzed the changes in MRI, histology and gene expression. At the same time, the ROM testing of FSU of L3-4 were completed and compared the difference in intact, stabbed and BMP-2 therapy three groups.Results: The treatment interverbral discs were found some degenerative changes by MRI, histology and gene expression at 6, 12, 24 weeks postoperation but had low level degeneration. The ROM testing of FSU of L3-4 in BMP-2 therapy group had some differences with intact group but had no changes with stabbed group at 6 weeks. At 12 and 24 weeks time points, treatment group still had variance with intact group in ROM testing but the results showed they were developing to normal and had obvious statistically significant differences with stabbed group.Conclusion: BMP-2 Partially injected in rabbit intervertebral disc not only shows delaying disc degeneration evidences by imagelogy, histology and gene expression but also finds the gene therapy discs are developing to normal by ROM testing of FUS of L3-4 during 9 to 21 weeks after BMP-2 injection(during 12 to 24weeks postoperation). We can hypothesis that the way of BMP-2 injected directly in intervertebral disc may be an effective new treatment to degeneration disc disease in the future.