Improving the clinical evidence of bone graft substitute technology in lumbar spine surgery.

Bone graft substitutes have been used routinely for spine fusion for decades, yet clinical evidence establishing comparative data remains sparse. With recent scrutiny paid to the outcomes, complications, and costs associated with osteobiologics, a need to improve available data guiding efficacious use exists. We review the currently available clinical literature, studying the outcomes of various biologics in posterolateral lumbar spine fusion, and establish the need for a multicenter, independent osteobiologics registry.

Do the adjacent level intervertebral discs degenerate after a lumbar spinal fusion? An experimental study using a rabbit model.

STUDY DESIGN: A rabbit model of disc degeneration adjacent to a lumbar spinal fusion. OBJECTIVE: To use a rabbit model to determine the long-term changes in the intervertebral discs at the levels above (cephalad) and below (caudad) 2 fused lumbar levels. SUMMARY OF BACKGROUND DATA: Lumbar spinal fusion is generally carried out to eliminate motion at a specific lumbar level. However, it is commonly thought that by eliminating motion at a level, one increases the motion at the adjacent levels cephalad and caudad the fused levels. There have been studies that have reported on degeneration occurring at the cephalad and caudad levels adjacent to the fused levels. METHODS: A total of 9 New Zealand white, female rabbits: 4 rabbits in the control group and 5 rabbits in the experimental group. The 5 rabbits in the experimental group underwent a posterolateral 2-level lumbar spinal fusion from L3 to L5. The changes in the lumbar discs were assessed using radiographs, magnetic resonance (MR) images, and histology at 6 months and 12 months. RESULTS: The results at 6 months are less clear than those at 12 months. The results at 12 months for the experimental group are (1) the intervertebral disc height decreased at the caudad adjacent level and to a lesser extent at the cephalad adjacent level; (2) the MRI scores for the discs at the caudad and cephalad adjacent levels showed severe loss of signal intensity as compared to the discs at the same levels in the control group. This loss was more pronounced at the caudad level where the loss of signal intensity was similar to that seen at the fused levels; (3) the histologic analysis showed severe degenerative changes with a lack of live cells in the nucleus pulposus and in the endplate at the caudad adjacent level. At the cephalad level, live cells were apparent (albeit few) in the nucleus pulposus, and there was a more normal looking endplate with live cells. CONCLUSION: The intervertebral discs at both the cephalad and the caudad levels adjacent to the 2 fused lumbar levels in this rabbit-model experiment carried out over 12 months after surgery showed degenerative changes asassessed using disc-height measurements, MR images, and histology, and the effect was more severe at the caudad adjacent level.

The AdLMP-1 transfection in two different cells; AF cells, chondrocytes as potential cell therapy candidates for disc degeneration.

BACKGROUND: LMP-1 is known to increase proteoglycan production through the upregulating the BMPs and it is also known that BMP-2 acts on anulus fibrosus cells and chondrocytes to increase proteoglycan production. METHOD: We carried out an experiment, the effect of AdLMP-1 transfection on AF cells and chondrocytes in the production of sulfated-glycosaminoglycans, mRNA expression (aggrecan, type I, II collagen, LMP-1, BMP-2, and BMP-7), and immunofluorescence staining. AF cells and chondrocytes were grown in monolayer and treated for 6 days with AdLMP1-green fluorescence protein (GFP) (10, 20, and 30 multiplicity of infection [MOI]). After 6 days, the sGAG content in the media was quantified using 1,9-dimethylmethylene blue staining. The mRNA expression was measured with real-time PCR after 20 MOI infection of AdLMP1-GFP. The each cells treated with 20 MOI infection of AdGFP was used as a control group for the mRNA expression. The each cell group was immunofluorescence stained with each antibodies in the chamber slide at 3 x 10(4) cells/chamber. FINDINGS: 1) The sGAG production was maximum in 20 MOI AdLMP1-GFP infection on the AdLMP-1 treatment for both of AF cells and chondrocytes. 2) The mRNA expression of aggrecan, type I collagen, type II collagen, LMP-1, BMP-2, and BMP-7 is increased in both AF cells and chondrocytes in 20 MOI AdLMP1-GFP infection. 3) On the immunofluorescence staining results, the positive immunofluorescence stained cell numbers are increased after 20 MOI AdLMP1-GFP infection concordant with upregulation of mRNA expression. CONCLUSIONS: The AdLMP-1 treatments in AF cells and chondrocytes may be useful for cell transplantation therapy in disc degeneration.

Spine fusion by gene therapy.

Over 250 000 patients each year undergo a spine fusion procedure in the US. This constitutes 50% of all bone graft procedures. Despite best efforts, a large percentage of spine fusions (up to 35%) fail to form a solid bony arthrodesis. This is a significant clinical problem and has led to research in bone formation biology to augment spine fusion rates. Both recombinant and purified osteoinductive cytokines have been studied in pilot and pivotal studies in humans. At this point, recombinant human bone morphogenetic protein-2 has received FDA approved for lumbar interbody application with titanium cages. Despite these successes, limitations of directly applying osteoinductive proteins related to cost and carriers remain to be overcome. Gene therapy for spine fusion and other bone healing applications are being pursued as an alternative strategy. This article will review the state of the art of local gene therapy for bone formation and to highlight specific issues, which must be addressed when pursuing such a program. A critical step in using gene therapy for bone formation is choosing an appropriate osteoinductive gene. In choosing the gene, one must consider the differences in efficacy of the gene as well as the gene availability due to proprietary constraints. The choice of delivery vector is important. Factors such as the potency of the gene and the specific application intended play a role in this decision. Next, the effective dose, transduction time, and gene transfer method must be established. The choice of carrier material to form the scaffold for the new bone formation is another critical step that must be optimized for successful bone formation. Finally, a strategy for in vitro and in vivo testing must be developed to maximize the chances of success in human trials.

Osteochondral lesions of the capitellum in pediatric patients: role of magnetic resonance imaging.

The role of magnetic resonance imaging (MRI) in the evaluation of patients with osteochondral lesions of the capitellum is undefined. To define its role, the cases of nine consecutive children with 11 capitellar osteochondral lesions who underwent MRI were reviewed. Magnetic resonance imaging accurately delineated the size of the osteochondral lesions and identified capitellar loose bodies not seen on plain radiographs in two elbows. In patients without capitellar loose bodies, two distinct MRI patterns existed that were similar to those seen in femoral head osteonecrosis. Magnetic resonance imaging aided in the treatment of children with osteochondral lesions of the capitellum. Further studies are necessary to define the significance of the two MRI patterns.

Fibrogenesis imperfecta ossium: imaging correlation in three new patients.

OBJECTIVE: Fibrogenesis imperfecta ossium is an extremely rare disorder that can easily be misdiagnosed. We retrospectively reviewed the clinical and imaging data of three confirmed cases of fibrogenesis imperfecta. DESIGN AND PATIENTS: The patients consisted of two men and one woman, ranging in age from 40 to 53 years. Radiography was performed in all the patients. One patient had a 3-year follow-up of the thoracolumbar spine with conventional radiography and thoracolumbar magnetic resonance (MR) imaging. Open biopsy was performed in all cases, confirming the diagnosis of fibrogenesis imperfecta ossium. RESULTS: All our cases demonstrated "fishnet" trabecular pattern by conventional radiographs, and a pelvis radiograph of one patient showed an equivocal sclerosis pattern. Multiple fractures were noted in two patients. A pseudoexostosis was present in the ilium in one patient. Thoracolumbar MR imaging demonstrated diffuse low signal intensity within the medullary space on both T1-weighed and T2-weighted images, except for a region of increased signal intensity in the L1 and L2 vertebral bodies on T2-weighed images due to edema from acute collapse. CONCLUSIONS: Although uncommon, fibrogenesis imperfecta ossium should be considered in a previously healthy patient with a combination of progressive bone pain, unexplained fractures, a radiologic pattern of fishnet osteopenia and MR imaging of low signal intensity bone marrow on both T1-weighted and T2-weighted images.

The orientation of a T cell receptor to its MHC class II:peptide ligands.

The TCR found on CD4 T cells recognizes peptides bound to self MHC class II molecules as well as non-self MHC class II molecules. We have used the receptor on a cloned T cell line called D10.G4.1 (D10) to perform a structure-function analysis of this interaction. The D10 T cell clone recognizes not only a peptide from conalbumin (CA-wt) bound to syngeneic I-Ak against which it was raised, but also the allogeneic MHC molecules I-A(b,v,p,q,d). In the present study, we show that residue 30 in complementarity-determining region 1 (CDR1) of the TCR alpha-chain interacts with the I-A alpha-chain at hvr2 (residues 52, 53, and 55). We also show that residue 51 in CDR2 of the TCR alpha-chain interacts with the peptide at peptide residue 2. Finally, we show that residue 29 in CDR1 of the TCR beta-chain affects recognition of the glutamic acid at residue 66 in the I-A beta-chain. These data suggest an orientation of TCR relative to its peptide:MHC class II ligands. We argue that this orientation will be shared by all CD4 TCRs, and that it is only subtly different from the common orientation proposed for receptors binding to MHC class I.

The specificity and orientation of a TCR to its peptide-MHC class II ligands.

A T cell-mediated immune response is mainly determined by the 3-5 aa residues that protrude upwards from a peptide bound to an MHC molecule. Alterations of these peptide residues can diminish, eliminate or radically alter the signal that the T cell receives through its T cell receptor (TCR). We have used peptide immunizations of normal mice and mice carrying alpha or beta chain TCR transgenes to identify three distinct peptide contact points. One, near the carboxyl terminus of the peptide, involves the beta chain CDR3 region; the second was centrally located and interacted with both the alpha and beta chain CDR3 loops; the third was near the amino terminus of the peptide, and affected V alpha gene usage, but not the structure of CDR3 of either TCR chain. Based on these results, we propose an orientation for the TCR of this cloned line and argue for its generality.

Both high and low avidity antibodies to the T cell receptor can have agonist or antagonist activity.

Anti-TCR antibodies can activate or block the activation of T cells. In the present experiments, we have shown that different monoclonal antibodies to the same TCR can have either agonist or antagonist activity, and we have examined the relationship between these functional effects and the avidity of the antibody for the TCR. We show here that it is not the avidity of an anti-TCR antibody that determines whether it acts as an agonist or an antagonist. Moreover, we show that monovalent Fab fragments of agonist antibodies produce detectable changes in T cell behavior. These data suggest that T cell activation may involve not just aggregation of the TCR but also some induced change in individual ligated receptors, and that agonists may produce this change while antagonists do not. We argue that similar effects may apply to peptide-MHC ligands as well.