**Early vs. Later Decompression of Cervical Spinal Cord Injuries with Spinal Cord Compression
J.B. Sledge, III, MD; D.G. Anderson, MD; M.G. Fehlings, MD, PhD, FRCS(C); A.R. Vaccaro, MD
North American spine surgeons, under the guidance of Dr. Fehlings, will be participating in the Surgical Treatment of Acute Spinal Cord Injury Study (STASCIS). This is a randomized, controlled multicenter trial designed to evaluate the effect of early (</= 12 hours) versus later (>/= 24 hours) decompression surgery on neurologic recovery following cervical spine trauma. Four hundred fifty patients with cervical spinal cord injury will be batch randomized according to age, sex, American Spinal Injury Association (ASIA) score and center to either early or late decompression. Patients will be evaluated by ASIA score and FIM score at up to one year to compare the two groups.
SOX9-Mediated Gene Therapy in a Degenerative Disc Model
F.M. Phillips, MD; R.C. Haydon, MD, PhD
The objective of this proposal was to determine the efficacy of exogenous SOX9 for the treatment and/or prevention of degenerative disc disease in an animal model. Three specific aims were proposed. The first aim was to determine whether the AdSOX9 vector could efficiently transduce rabbit lumbar intervertebral discs in vivo. The second aim was to determine whether exogenous SOX9 expression could promote the healing of degenerative lumbar discs in an animal model of disc degeneration. The third aim was to determine whether exogenous SOX9 expression could prevent and/or delay the intervertebral disc degenerative process in vivo.
We have recently completed the proposed studies. Specifically, we first demonstrated that recombinant adenoviral vectors expressing SOX9 (ie, AdSOX9) or GFP (ie, AdGFP) effectively transduced disc cells when they were injected into the lumbar intervertebral discs of New Zealand white rabbits. When the intervertebral disc materials of the injected animals were analyzed, expression of exogenous SOX9 and induced production of type II collagen were readily detected in AdSOX9-injected disc tissues using immunohistochemistry.
We next used a stab incision procedure to establish the lumbar intervertebral disc degeneration model of New Zealand white rabbits. To determine the potential therapeutic effect of SOX9, we first introduced stab incision for four weeks, followed by injection of the AdSOX9 or the AdGFP control into the degenerative discs. To determine the possible preventive effect of SOX9 on disc degeneration, we injected the AdSOX9 or AdGFP virus at the same time when the lumbar discs were stabbed. Animals were sacrificed at six and eight weeks after injection and were evaluated using X-ray radiography and MRI. The injected discs were evaluated histologically for preservation of normal disc architecture and the levels of Type II collagen in the nucleus pulposus were immunohistochemically determined.
Findings or Conclusions to Date. We found that AdSOX9 injection effectively transduces intervertebral discs and increases the production of Type II collagen. Using the stab incision-induced disc degeneration model, we have demonstrated that AdSOX9 injection restored the chondroid appearance of normal nucleus pulposus whereas the AdGFP-injected discs showed degenerative changes consistent with annulotomy-induced degeneration. Both plain X-rays and MRIs showed lesser grades of disc degeneration in the SOX9-treated discs. Thus, our findings support the hypothesis of our application, suggesting that SOX9 can be used as a potential therapeutic agent to treat disc degeneration.
BMP-Transduced Mesenchymal Stem Cells for Spine Fusion
T.C. He, MD, PhD; R.C. Haydon, MD, PhD; F.M. Phillips, MD
The objective of this pilot study is to determine and compare the efficacy of posterior spine fusion with different sources of mesenchymal stem cells that are transduced with BMP2, BMP6 and BMP9. Robust bone regeneration has important implications for the clinical management of many musculoskeletal disorders, including bone grafting, fracture healing and spinal fusion. Two specific aims were proposed in the original application. The first aim was to determine the transduction efficiency of adenoviral vectors expressing BMP-2, BMP-6 and BMP-9 in rabbit mesenchymal stem cells. The second aim was to determine the efficacy of posterior spine fusion mediated by the AdBMP-transduced mesenchymal stem cells derived from bone marrow and peripheral blood cells.
Since receiving the NASS funding, we have completed the first aim. Specifically, recombinant adenoviruses (AdBMPs) expressing BMP-2, BMP-6 and BMP-9 were used to infect rabbit mesenchymal stem cells derived from either bone marrow cells (BMCs) or peripheral buffycoat cells (PBCs). By monitoring the expression of green fluorescence protein (GFP), we found that both marrow cells and buffy coat cells were effectively transduced by the AdBMP-2, -6 and -9 vectors and the gene expression lasted at least ten days under cell culture conditions.
We next carried out a pilot animal study, in which autologous BMCs and PBCs were first transduced ex vivo with AdBMP-2, -6 and -9, and the AdGFP control, and the transduced cells were soaked in Type I collagen sponges and placed over the decorticated costal processes of rabbit lumbar L4-5 vertebrae to complete the arthrodesis. The level and duration of transgene expression were determined by detecting the GFP expression postmortem at two, four and eight weeks after implantation. The fusion sites were examined radiographically and histologically.
Since the submission of our status report in August 2003, we have conducted more animal studies to determine the reproducibility and efficacy of BMP-2, -6 and -9 mediated spinal fusion, with emphasis on using BMCs as cell carriers. Through X-ray radiographic, CT scan and histological examination, we demonstrated that all three BMPs can effectively induce spinal fusion using transduced bone marrow cells, at as early as four weeks after implantation. These findings confirm and expand our pilot studies described in the previous status report.
Findings or Conclusions to Date. Our results demonstrate that: 1) AdBMPs effectively transduced both BMCs and PBCs; 2) all three BMPs were able to induce solid spinal fusion at as early as four weeks after implantation; and 3) BMCs were better recipient (than PBCs) of gene transfer and promoted more effective spinal fusion.
*Abstracts/permission forms not received at the time of publication
**Current and ongoing research