Biomedical subjects

S Tim Yoon

Publications and source records attributed to S Tim Yoon.

At least 19 recordsLinked to original sources

PubMed2006

Increased swelling complications associated with off-label usage of rhBMP-2 in the anterior cervical spine.

STUDY DESIGN/SETTING: Independent, retrospective clinical record review with a concurrent control. OBJECTIVE: To identify whether rhBMP-2 is associated with an increased incidence of clinically relevant postoperative prevertebral swelling problems in patients undergoing anterior cervical fusions. SUMMARY OF BACKGROUND DATA: Bone Morphogenetic Protein-2 (rhBMP-2) is FDA approved as a bone graft substitute in anterior lumbar interbody fusions. rhBMP-2 has also been used "off-label" in anterior cervical fusions. We suspected that rhBMP-2 might increase the incidence of adverse swelling events. METHODS: A total of 234 consecutive patients (ages 12-82 years) undergoing anterior cervical fusion with and without rhBMP-2 over a 2-year period at one institution comprised the study population. The incidence of clinically relevant prevertebral swelling was calculated. The populations were compared and statistical significance was determined. RESULTS: A total of 234 patients met the study criteria, 69 of whom underwent anterior cervical spine fusions using rhBMP-2; 27.5% of those patients in the rhBMP-2 group had a clinically significant swelling event versus only 3.6% of patients in the non-rhBMP-2 group. This difference was statistically significant (P < 0.0001) and remained so after controlling for other significant predictors of swelling. CONCLUSIONS: Off-label use of rhBMP-2 in the anterior cervical spine is associated with an increased rate of clinically relevant swelling events.

Adolescent↗

PubMed2006

The expression of anabolic cytokines in intervertebral discs in age-related degeneration.

STUDY DESIGN: Quantitative analysis of endogenous messenger ribonucleic acid (mRNA) expression of anabolic cytokines in the anulus fibrosus and nucleus pulposus tissue from the intervertebral discs of young and old rabbits was performed. OBJECTIVES: To measure the expression of anabolic cytokines bone morphogenetic protein-2 (BMP-2), BMP-7, transforming growth factor-beta (TGF-beta), and insulin-like growth factor-I (IGF-I) in the anulus fibrosus and nucleus pulposus tissue from young and old rabbits to determine if there are differences with age. SUMMARY OF BACKGROUND DATA: Disc degeneration increases with age and is associated with compromised disc chondrocytic function. Molecules such as BMP-2, BMP-7, TGF-beta, and IGF-I are known to up-regulate disc cell synthesis of key chondrocytic matrix molecules in vitro, and have been proposed as therapeutic agents to prevent disc degeneration. Previous studies have shown that exogenous anabolic cytokines can up-regulate disc-cell function both in vitro and in vivo, however, the endogenous expression of anabolic cytokines in the disc is still unknown. METHODS: New Zealand white rabbits aged 3 years (old) and 6 months (young) were used. Quantitative real-time polymerase chain reaction was performed to measure the mRNA levels of BMP-2, BMP-7, TGF-beta1, and IGF-I from anulus fibrosus and nucleus pulposus tissue from young and old rabbits. The discs form the young rabbits represent nondegenerated discs, and the discs from the old rabbits represent discs at the onset of degeneration. RESULTS: In the nucleus pulposus, the mRNA levels, given as a ratio of old to young, were 3.6 for BMP-2 (P = 0.004), 61 for BMP-7 (P = 0.02), 4.0 for TGF-beta1 (P = 0.3), and 0.6 for IGF-I (P = 0.2). In the anulus fibrosus, the mRNA levels, given as a ratio of old to young, were 1.6 for BMP-2 (P = 0.07), 4.6 for BMP-7 (P = 0.004), 2.9 for TGF- beta1 (P = 0.01), and 2.0 for IGF-I (P = 0.1). CONCLUSION: The disc tissue from the old rabbits as compared to the young rabbits showed, in general, significantly higher mRNA levels of endogenous BMP-2, BMP-7, and TGF-beta in both the anulus fibrosus and nucleus pulposus. The similar patterns of up-regulation in gene expression with age shown by these 3 anabolic cytokines suggest a common pathway in terms of regulation and transcription in the early stage of disc degeneration. The knowledge of the age-related pattern in endogenous gene expression of these anabolic cytokines could provide important information for clinical interventional therapy.

Aging↗

PubMed2006

Molecular therapy of the intervertebral disc.

Disc degeneration is the loss of the normal nucleus pulposus disc matrix to a more fibrotic and less cartilaginous structure. This change in disc micro-anatomy can be associated with pain and deformity, however, prevention and treatment options of disc degeneration are currently limited. Much research is going on to understand intervertebral discs at a molecular/ cellular level in hopes of creating clinically applicable options for treating disc degeneration. This review article will give insight into the current and developing status of treating intervertebral disc degeneration from a molecular standpoint.

Collagen↗

PubMed2006

Advances in osteobiologics in spine surgery.

In spine surgery, fixation devices that revolutionized spinal fusion are becoming mature technologies, and new tools derived from biologics are becoming more important in clinical practice. Thus, surgeons need to become more sophisticated in evaluating and using these new biologics, which are rapidly entering the market. The majority of these biologics are aimed at enhancing spinal fusion and can be called osteobiologics. Osteobiologic products vary from recombinant proteins to specially prepared allograft or autograft materials. Their financial costs are considerable, and the level of proof for the efficacy and safety of these products varies widely. In this article, I delineate useful principles that can be used to evaluate current and future generations of osteobiologic products, and I discuss the most pertinent examples of specific osteobiologics.

Biocompatible Materials↗

PubMed2005

Disc degeneration in the rabbit: a biochemical and radiological comparison between four disc injury models.

STUDY DESIGN: A biochemical and radiologic comparison of 4 disc injury models to produce disc degeneration in the rabbit was carried out in 2 experiments. OBJECTIVES: To develop a reliable animal model of intervertebral disc degeneration. SUMMARY OF BACKGROUND DATA: In order to study various interventions for retarding or preventing disc degeneration, a reliable animal model of disc degeneration is needed. METHODS: First experiment: 7 New Zealand white rabbits (1 year old, 3.5-4.5 kg body weight) were used to test 4 different disc injury models; intradiscal injection of Camptothecin (an apoptotic agent) using a 23-gauge needle at L2-L3, nucleus aspiration using a 21-gauge needle at L3-L4, 3 anulus punctures using a 21-gauge needle at L4-L5, and 1 anulus puncture using a 18-gauge needle at L5-L6. The L1-L2 level was used as a control. Rabbits were killed 12 weeks later. Lumbar spinal magnetic resonance images were assessed using 4 grades of disc degeneration. The water content of the nucleus was measured. Dimethylmethylene blue (DMMB) assay was used to measure the sulfated-glycosaminoglycan content. Second experiment: the 21-gauge 3-puncture and the 18-gauge 1-puncture models, thought most effective in producing disc degeneration in the first experiment, were again used in a second study. Six rabbits were killed 8 weeks later, the water and sulfated-glycosaminoglycan contents being measured as in the first experiment. RESULTS: In the first experiment, the water content in the aspiration and puncture models was significantly decreased. Only the sulfated-glycosaminoglycan content in the aspiration model showed a significant decrease as compared to the control. Disc heights and magnetic resonance grades documented significant degeneration occurring in the aspiration and puncture models. In the second experiment, the water content showed a significant decrease in the 21-gauge 3-puncture model, whereas neither of the results for the sulfated-glycosaminoglycancontent showed a significant difference as compared to the control data. CONCLUSION: In the first experiment, the 21-gauge 3-puncture and the 18-gauge 1-puncture models produced the most consistent disc degeneration in the rabbit lumbar spine. When these 2 models were again studied in the second experiment, the 21-gauge 3-puncture technique was superior in producing disc degeneration over a shorter period of time.

Animals↗

PubMed2005

Kyphoplasty for salvage of a failed vertebroplasty in osteoporotic vertebral compression fractures: case report and surgical technique.

Osteoporotic vertebral compression fractures are a significant source of morbidity. Recently described techniques of vertebroplasty and kyphoplasty have provided consistent successful outcomes in the short term. However, techniques to address the failure of vertebroplasty have not been addressed. We present two cases of failed vertebroplasty that were revised with a kyphoplasty technique. Both patients had near complete resolution of preoperative symptoms and had a significant vertebral height restoration more than 10 months after revision with kyphoplasty. In conclusion, kyphoplasty technique can be utilized to salvage failed vertebroplasty.

Aged↗

PubMed2005

Open vertebral cement augmentation combined with lumbar decompression for the operative management of thoracolumbar stenosis secondary to osteoporotic burst fractures.

Osteoporotic burst fractures with neurologic symptoms are typically treated with neural decompression and multilevel instrumented fusion. These large surgical interventions are challenging because of patients' advanced ages, medical co-morbidities, and poor fixation secondary to osteoporosis. The purpose of this retrospective clinical study was to describe a novel technique for the treatment of osteoporotic burst fractures and symptomatic spinal stenosis via a limited thoracolumbar decompression with open cement augmentation [vertebroplasty (VP) or kyphoplasty (KP)]. Indications for decompression and cement augmentation were intractable pain at the level of a known osteoporotic burst fracture with symptoms of spinal stenosis. As such, 25 patients (mean age, 76.1 years) with low-energy, osteoporotic, thoracolumbar burst fractures (7 males, 18 females; 39 fractures) were included. In all cases, laminectomy of the stenotic level(s) was followed by vertebral cement augmentation (9 VP; 16 KP). When a spondylolisthesis at the decompressed level was present, instrumentation was applied across the listhetic level (n = 9). Clinical outcome (1 = poor to 4 = excellent) was assessed on last clinical follow-up (mean, 44.8 wks). In addition, a modified MacNab's grading criteria was used to objectively assess patient outcomes postoperatively. Radiographic analysis of sagittal contour was assessed preoperatively, immediately postoperatively, and at final follow-up. The average time from onset of symptoms to intervention was 19 weeks (range, 0.3-94 wks). A mean of 1.6 fractures/patient was augmented (range, 1-3 fractures) and 2.8 levels were decompressed (range, 1-6 levels). No statistical difference in anatomic distribution or number of fractures between the VP and KP groups or in the instrumented versus noninstrumented patients was noted (P > 0.05). An overall subjective outcome score of 3.4 was noted. Twenty of 25 patients were graded as excellent/good according to the modified MacNab's criteria. The choice of augmentation procedure or use of instrumentation did not predict outcome (P = 0.08). Overall, 1.7 degrees of sagittal correction was obtained at final follow-up. One patient was noted to have progressive kyphosis after KP. The use of a limited-posterior decompression and open cement augmentation via VP or KP is a safe treatment option for patients who have osteoporotic burst fractures and who are incapacitated from fracture pain and concomitant stenosis. After thoracolumbar decompression, open VP/KP provides direct visualization of the posterior vertebral body wall, allowing for safe cement augmentation of burst fractures, stabilizing the spine, and obviating the need for extensive spinal reconstruction. Although clinically successful, this technique warrants careful patient selection.

Aged↗

PubMed2004

The potential of gene therapy for the treatment of disc degeneration.

Research in biologic methods of treating disc degeneration is still in its infancy. Many different strategies are being evaluated, but the gene therapy strategy stands out because of its potential for long-term efficacy. Choosing the correct gene for use in gene therapy is critically important. Of the many different classes of potentially therapeutic genes, the regulatory genes hold the most promise. Of the different gene therapy delivery methods, the most work has been performed with viral vectors, either ex vivo or in vivo. Current research now is turning toward in vivo experiments in rabbits. Efficacy and safety will be demonstrated first with smaller animal models. Beyond that, nonhuman primate experiments demonstrating efficacy and safety will be the penultimate step before initiation of human studies.

Adaptor Proteins, Signal Transducing↗

PubMed2004

The effect of blocking a nutritional pathway to the intervertebral disc in the dog model.

BACKGROUND: The hypothesis that injecting bone cement adjacent to one or both endplates would bring about degeneration in the intervening disc was tested. METHODS: In 11 dogs, bone cement was injected just below the superior endplates of L1, L2, and L3 to block the nutritional supply through these endplates to the three intervertebral discs T13-L1, L1-L2, and L2-L3. In one other dog, both the superior and the inferior endplates of the same discs (T13-L1, L1-L2, and L2-L3) were blocked with bone cement. All 12 dogs were euthanized between 31 and 70 weeks after the surgery. The three experimental discs (T13-L1, L1-L2, and L2-L3) and two control discs (T12-T13 and L4-L5) were excised and assessed using enzyme-linked immunosorbent assay (ELISA) and histology. RESULTS: Radiographs of the lumbar spine at the time of death did not show any signs of disc bulging, disc space narrowing, or peripheral osteophyte formation in any of the 12 dogs. The experimental discs as well as the control discs appeared normal in every dog. After the discs were bisected, they were carefully inspected for any visible signs of degeneration. The experimental discs showed no clear signs of disc degeneration and were not distinguishable from the control discs on a gross level. The numerical results from the ELISA showed that in the experimental discs as opposed to the control discs, there were significant increases in proteoglycan content in both the nucleus (P = 0.033) and annulus (P = 0.01) and clear histologic changes in some of the discs. CONCLUSION: The results show that injecting bone cement adjacent to one or both endplates for up to 70 weeks does not produce degeneration in any visible form in the intervening disc. There were no disc bulging, no apparent annular fissures, and no disc spacing narrowing. There were, however, increases in protoglycan content in both the nucleus and the annulus and clear histologic changes in some of the discs.

Animals↗

PubMed2004

Effect of bone morphogenetic protein-2 (BMP-2) on matrix production, other BMPs, and BMP receptors in rat intervertebral disc cells.

OBJECTIVE: An in vitro experiment study using rat disc cells was carried out to determine the effect of bone morphogenetic protein-2 (BMP-2) on extracellular matrix production, other BMPs, and BMP receptors (BMPRs). METHODS: Cells from the anulus fibrosus and transition zone were harvested and cultured. When the cells reached 80% confluence, BMP-2 was added to reach a final concentration of 200 ng/mL. Three days later, the culture media were collected for the assay of sulfated glycosaminoglycans (sGAG) and collagen types I and II. The cells were harvested for RNA extraction to determine the genes expressed. All experiments were performed at least three times to ensure repeatability. RESULTS: BMP-2 significantly increased aggrecan and collagen type II mRNA expression 8.30 and 4.61 times, respectively, and decreased versican mRNA expression 0.54 times as compared with control. Collagen type I production and mRNA level were not changed. BMP-2 significantly increased transforming growth factor-beta1 (TGFbeta1) and BMP-7 mRNA expression 2.32 and 2.45 times, respectively, compared with control. There was no significant change in BMP-6 mRNA expression. BMPR type IB and II mRNA expressions were increased and BMPR type 1A mRNA expression was decreased, but none of these differences was significant. CONCLUSIONS: The results of this study show that in rat intervertebral disc cells, BMP-2 increases aggrecan and collagen type II mRNA expression and decreases versican gene expression. BMP-2 also up-regulates mRNA expression for BMP-7 and TGFbeta but has no significant effect on the BMPRs.

Aggrecans↗

PubMed2003

The effect of bone morphogenetic protein-2 on rat intervertebral disc cells in vitro.

STUDY DESIGN: An in vitro experiment to determine the molecular and cellular effect of recombinant human bone morphogenetic protein-2 on cultured rat intervertebral disc cells was performed. OBJECTIVES: To determine the effect of recombinant human bone morphogenetic protein-2 on cell proliferation, production of sulfated-glycosaminoglycan, and the expression of genes specific for chondrocytes (Type II collagen, aggrecan, and Sox9) in cultured rat intervertebral disc cells. SUMMARY OF BACKGROUND DATA: Intervertebral disc degeneration is associated with cellular and biochemical changes, which include decreased synthesis of cartilage specific gene products such as Type II collagen and aggrecan. Although bone morphogenetic protein-2 is known to induce chondrogenesis during new bone formation, the effects on intervertebral disc cells have not been characterized. METHOD: Cells were isolated from the anulus fibrosus and transition zones of lumbar discs from Sprague-Dawley rats. The cells were grown in monolayer and treated with recombinant human bone morphogenetic protein-2 (0, 10, 100, 1000 ng/mL) in Dulbecco's Modified Eagle Medium/F-12 with 1% fetal bovine serum (day 0). On days 2, 4, and 7 after recombinant human bone morphogenetic protein-2 treatment, sulfated-glycosaminoglycan content in the media was quantified using 1,9-dimethylmethylene blue staining. The results were normalized according to culture duration and cell number. On day 7, mRNA was extracted for reverse transcriptase-polymerase chain reaction and real-time polymerase chain reaction to quantitate mRNAs of Type I collagen, Type II collagen, aggrecan, Sox9, osteocalcin, and glyceraldehyde phosphate dehydrogenase. Cell number was determined with a hemocytometer. RESULTS: Recombinant human bone morphogenetic protein-2 at 100 and 1000 ng/mL yielded a 17% and 42% increase in cell number on day 4, and a 59% and 79% on day 7, respectively. Recombinant human bone morphogenetic protein-2 at 10 ng/mL had no effect on cell number. Sulfated-glycosaminoglycan increase was greatest at day 7, increasing by 1.3-, 2.1-, and 3.6-fold with recombinant human bone morphogenetic protein-2 treatments of 10, 100, and 1000 ng/mL, respectively. Increases in mRNA levels of Type II collagen, aggrecan, Sox9, and osteocalcin were observed with recombinant human bone morphogenetic protein-2 concentrations of 100 and 1000 ng/mL on day 7 as determined by reverse transcriptase-polymerase chain reaction. No detectable increase in mRNA level of Type I collagen was observed with any levels of recombinant human bone morphogenetic protein-2. Real-time polymerase chain reaction showed the greatest effect at 1000 ng/mL recombinant human bone morphogenetic protein-2, leading to an 11.5-fold increase in aggrecan, a 4.6-fold increase in Type II collagen, a 5.3-fold increase in Sox9, and a 1.9-fold increase in osteocalcin mRNA above untreated controls at day 7. CONCLUSION: The results of this study show that recombinant human bone morphogenetic protein-2 enhances disc matrix production and chondrocytic phenotype of intervertebral disc cells. Recombinant human bone morphogenetic protein-2 increases cell proliferation and sulfated-glycosaminoglycan (proteoglycan) synthesis. It increases mRNA of Type II collagen, aggrecan, and Sox9 genes (chondrocyte specific genes), and osteocalcin, but not Type I collagen or glyceraldehyde phosphate dehydrogenase.

Aggrecans↗

PubMed2003

Adjacent segment motion after a simulated lumbar fusion in different sagittal alignments: a biomechanical analysis.

STUDY DESIGN: An in vitro biomechanical study of adjacent segment motion (at L3-L4 and L5-S1) after a simulated lumbar interbody fusion of L4-L5 in different sagittal alignments was carried out. OBJECTIVES: To test the hypothesis that an L4-L5 fixation in different sagittal alignments causes increased angular motion at the adjacent levels (L3-L4 and L5-S1) in comparison with the intact spine. SUMMARY OF BACKGROUND DATA: Clinical experience has suggested that lumbar fusion in a nonanatomic sagittal alignment can increase degeneration of the adjacent levels. It has been hypothesized that this is the result of increased motion at these levels; however, to the authors' knowledge no mechanical studies have demonstrated this. METHODS: Eight fresh human cadaveric lumbar spines (L3-S1) were biomechanically tested. Total angular motion at L3-L4 and L5-S1 under flexion-extension load conditions (7-Nm flexion and 7-Nm extension) was measured. Each specimen was tested intact, and then again after each of three different sagittal fixation angles (at L4-L5): (1) in situ (21 degrees lordosis), (2) hyperlordotic (31 degrees lordosis), and (3) hypolordotic (7 degrees lordosis). The simulated anterior/posterior fusion was performed at L4-L5 with pedicle screws posteriorly, vertebral body screws anteriorly, and an interbody dowel. RESULTS: The averaged values for flexion-extension motion at L3-L4 were as follows: intact specimen 2.0 degrees, in situ fixation 4.0 degrees, hyperlordotic fixation 1.7 degrees, hypolordotic fixation 6.5 degrees. The averaged values for flexion-extension motions at L5-S1 were as follows: intact specimen 2.3 degrees, in situ fixation 2.6 degrees, hyperlordotic fixation 3.6 degrees, hypolordotic fixation 2.9 degrees. CONCLUSION: Hypolordotic alignment at L4-L5 caused the greatest amount of flexion-extension motion at L3-L4, and the differences were statistically significant in comparison with intact specimen, in situ fixation, and hyperlordotic fixation. Hyperlordotic alignment at L4-L5 caused the greatest amount of flexion-extension motion at L5-S1, and the difference was statistically significant in comparison with intact specimen but not in situ fixation or hypolordotic fixation.

Aged↗

PubMed2003

BMP-2 and CDMP-2: stimulation of chondrocyte production of proteoglycan.

A hallmark of intervertebral disc degeneration is loss of proteoglycans. Cytokines may be used to stimulate proteoglycan production in the disc to reverse or prevent disc degeneration. The effects of bone morphogenetic protein 2 (BMP-2) and cartilage-derived morphogenetic protein 2 (CDMP-2) (singly and jointly) on proteoglycan synthesis by a chondrocytic cell line (MC615) were studied. MC615 cells were dosed with BMP-2, CDMP-2, or both, cultured for 6 days, and then assayed as follows: (1). The proteoglycan content of the medium and extracellular matrix were determined by dimethyl-methylene blue staining; (2). cell numbers were determined after 6 days of culture using the Hoechst dye DNA assay; (3). aggrecan mRNA was measured with the reverse transcription-polymerase chain reaction and Northern blotting assays. Both BMP-2 and CDMP-2 significantly enhanced proteoglycan production and aggrecan mRNA expression in a dose-dependent manner, although BMP-2 is more effective than CDMP-2 in increasing sulfated proteoglycan production. But BMP-2 and CDMP-2 have only a slight, nonsignificant effect on cell proliferation. There is no evidence of antagonism or synergy between the two growth factors in the aggrecan gene expression.

Animals↗

PubMed2003

Transdiscal L5-S1 screws for the fixation of isthmic spondylolisthesis: a biomechanical evaluation.

The current study is a biomechanical study using a cadaveric model of L5-S1 spondylolisthesis. The purpose of the current study was to compare, in a cadaveric model of simulated L5-S1 spondylolisthesis, the biomechanical stiffness of transdiscal fixation with traditional pedicle screw fixation, and transdiscal fixation with combined interbody/pedicle screw fixation. The surgical management of L5-S1 spondylolisthesis is a challenge because of the difficulties in achieving a reliable arthrodesis in the face of high mechanical forces. A method of lumbosacral fixation that has been used successfully in moderate grades of spondylolisthesis at our institution involves the use of transdiscal S1 pedicle screws. With this technique, S1 pedicle screws are placed through the S1 pedicle, through the superior endplate of S1, through the inferior endplate of L5, to terminate in the L5 body. Eighteen fresh human cadaveric (age 59-88 years) L5-S1 motion segments were obtained. The end of each intact motion segment was potted up to its midbody in a 10-cm-diameter polyvinylchloride end-cap using dental cement. The intact specimen was then biomechanically tested as follows: 1) axial compression (500 N), 2) flexion (10 Nm), 3) extension (10 Nm), 4) right lateral bending (10 Nm), and 5) left lateral bending (10 Nm). Stiffness values were calculated from the load-deflection curves obtained. Spondylolisthesis was then simulated by displacing L5 on S1 (% slip average = 41.3%) after performing a radical L5-S1 discectomy, L5 laminectomy, and bilateral L5-S1 facetectomies. The 18 motion segments were divided into two groups. Group I (n = 10) was biomechanically tested (as above) after pedicle screw fixation and again after replacing the S1 pedicle screws with transdiscal screws. Group II (n = 8) was biomechanically tested (as above) after combined interbody/pedicle screw fixation and again after fixation with transdiscal screws. Load-deflection curves were obtained each time, and stiffness values were calculated from the curves. Transdiscal fixation was 1.6-1.8 times stiffer than pedicle screw fixation (p < 0.05) in all loading modes tested. There were no differences in stiffness between transdiscal fixation and combined interbody/pedicle screw fixation. In a cadaveric model of simulated L5-S1 spondylolisthesis, transdiscal L5-S1 fixation produced a 1.6-1.8 times stiffer construct than traditional pedicle screw fixation. Further, the stiffness of the transdiscal fixation was equal to that of a combined interbody/pedicle screw fixation.

Aged↗

PubMed2003

Inhibition of proteoglycan and type II collagen synthesis of disc nucleus cells by nicotine.

OBJECT: Systemic nicotine has been hypothesized to cause degeneration of the intervertebral disc which in turn decreases vascular supply to the disc through a cholinergic receptor-mediated process. Another possible mechanism may be through direct regulatory effects on disc cells. In this study, the authors tested the hypothesis that nicotine adversely affects nucleus pulposus cells by directly inhibiting proteoglycan synthesis and gene expression of type II collagen (Phase I study). They also assessed the hypothesis that nicotine inhibits the bone morphogenetic protein (BMP)-2-induced upregulation of extracellular matrix (Phase II study). METHODS: Cells were isolated from nucleus pulposus obtained in rat lumbar discs and cultured on a monolayer. Media were treated with nicotine and/or recombinant human (rh)BMP-2 for 7 days. Sulfated glycosaminoglycan (SO4-GAG) in media was quantified using 1,9-dimethylmethylene blue (DMMB) assay. Gene assay of types I and II collagen, Sox9, and glyceraldehyde-3-phosphate dehydrogenase were quantified using reverse transcriptase-polymerase chain reaction (RT-PCR) and real time PCR. In the Phase I study, nicotine-treated (100 microg/ml) and non-treated cells were compared. The s-GAG production and messenger RNA (mRNA) of type II collagen and Sox9 decreased significantly in the nicotine-treated group. In the Phase II study, five groups were compared: 1) non-treatment; 2) rhBMP-2 only (100 ng/ml); and 3-5) with rhBMP-2 (100 ng/ml) and increasing doses of nicotine (1 [third group], 10, [fourth group], 100 [fifth group] microg/ml). The SO4-GAG production and mRNA of type II collagen and Sox9 decreased significantly in the groups treated with rhBMP-2 combined with 10 and 100 microg/ml of nicotine compared with the group treated with rhBMP-2. CONCLUSIONS: The results of this study raise the possibility that nicotine may contribute to the process of disc degeneration by a direct effect on the nucleus pulposus cells, possibly by antagonizing the effect of BMP-2.

Animals↗

PubMed2002

Effect of tail suspension (or simulated weightlessness) on the lumbar intervertebral disc: study of proteoglycans and collagen.

STUDY DESIGN: An experiment to measure the proteoglycan and collagen content of the lumbar intervertebral discs of rats that had been tail-suspended for up to 4 weeks. OBJECTIVES: To determine the effect of tensile force (or simulated weightlessness) on the intervertebral disc. SUMMARY OF BACKGROUND DATA: During space flight the intervertebral disc experiences low compressive force (because of so-called "weightlessness"), which, in turn, produces, among other things, low hydrostatic pressure acting on the disc cells. Although disc cells respond (in vitro) to changes in hydrostatic pressure, it is unclear what effect low levels of hydrostatic pressure have in vivo and whether they lead to a degenerative catabolic process. The rat tail-suspension model is appropriate for studying the effects of tensile force on the disc. The disc (especially the anulus) is subjected to tension during various body movements (e.g., bending stretches the posterior anulus, and twisting tensions the whole anulus). METHODS: Thirty-two Sprague-Dawley rats were tail-suspended for either 2 weeks (16 rats) or 4 weeks (16 rats). Sixteen other rats were left unsuspended for 4 weeks; these were used as controls. At the end of 2 or 4 weeks, as appropriate, the rats were killed and their lumbar spines were removed. In each rat the six lumbar discs were bisected and the discs (anulus and nucleus together) were carefully removed. The six lumbar discs from one rat were pooled with the six lumbar discs of a second matching rat (i.e., from the same group) to give one sample. The disc samples were then assessed using enzyme-linked immunosorbent assays. RESULTS: There was a 35% statistically significant decrease in proteoglycan content going from the control group down to the 4-week group, but no significant differences between the control group and the 2-week group or between the 2-week group and the 4-week group. There were no statistically significant differences between the three groups for collagen I or collagen II. CONCLUSIONS: These findings clearly establish a link between decreased proteoglycan content and tension on the disc, as modeled by the tail-suspended rat.

Animals↗

PubMed2002

Osteoinductive molecules in orthopaedics: basic science and preclinical studies.

Osteoinductive molecules are characterized by their ability to promote the formation of bone. Most osteoinductive molecules are cytokines, which are extracellular proteins or peptides that mediate cell to cell signaling. Examples of osteoinductive cytokines are certain bone morphogenetic proteins and some growth and differentiation factors. Some osteoinductive molecules are not secreted molecules. LIM mineralization protein-1 is an example of an intracellular osteoinductive molecule. Significant advances have been made in characterizing the molecular composition and mechanism of action of these osteoinductive molecules. Preclinical studies with these molecules have provided better understanding of the doses, formulation, and delivery mechanism necessary for effective bone formation in model systems of spinal fusion and other orthopaedic problems. The current authors will review the most important basic science and preclinical studies involving these osteoinductive molecules.

Animals↗

PubMedDate not supplied

The effects of doxorubicin (adriamycin) on spinal fusion: an experimental model of posterolateral lumbar spinal arthrodesis.

BACKGROUND CONTEXT: Malignant spinal lesions may require surgical excision and segmental stabilization. The decision to perform a concomitant fusion procedure is influenced in part by the need for adjunctive chemotherapy as well as the patient's anticipated survival. Although some evidence exists that suggests that chemotherapy may inhibit bony healing, no information exists regarding the effect of chemotherapy on spinal fusion healing. PURPOSE: To determine the effect of a frequently used chemotherapeutic agent, doxorubicin, on posterolateral spinal fusion rates. STUDY DESIGN/SETTING: Prospective animal model of posterolateral lumbar fusion. OUTCOME MEASURES: Determination of spinal fusion by manual palpation of excised spines. Plain radiographic evaluation of denuded spines to evaluate intertransverse bone formation. METHODS: Thirty-two New Zealand White rabbits underwent posterior intertransverse process fusion at L5-L6 with the use of iliac autograft bone. Rabbits randomly received either intravenous doxorubicin (2.5 mg/kg) by means of the central vein of the ear at the time of surgery (16 animals) or no treatment (16 animals; the control group). The animals were euthanized at 5 weeks, and the lumbar spines were excised. Spine fusion was assessed by manually palpating (by observers blinded to the treatment group) at the level of arthrodesis, and at the adjacent levels proximal and distal. This provided similar information to surgical fusion assessment by palpation in humans. Fusion was defined as the absence of palpable motion. Posteroanterior radiographs of the excised spines were graded in a blinded fashion using a five-point scoring system (0 to 4) devised to describe the amount of bone observed between the L5-L6 transverse processes. Power analysis conducted before initiation of the study indicated that an allocation of 16 animals to each group would permit detection of at least a 20% difference in fusion rates with statistical significance at p=.05. RESULTS: Eleven of the 16 spines (69%) in the control group and 6 of the 16 spines (38%) in the doxorubicin group fused. This difference was statistically significant (=.038). There was no significant correlation (p>.05) between the radiographic grade of bone formation (0 to 4) and fusion as determined by palpation. There were four wound infections in the control group and four in the doxorubicin group. However, solid fusions were palpated in three of these four spines in both the control and treatment groups. CONCLUSIONS: No significant differences in wound complications were noted with doxorubicin administration. A single dose of doxorubicin administered intravenously at the time of surgery appears to play a significant inhibitory role in the process of spinal fusion. If similar effects occur in humans, these data suggest that doxorubicin may be harmful to bone healing in a spine fusion if given during the perioperative period. Further investigation will be necessary to determine the effect of time to aid at determining whether doxorubicin administered several weeks pre- or postoperatively results in improved fusion rate, and whether bone morphogenetic proteins can overcome these inhibitory effects.

Animals↗