Faculty Bibliography

STUDY DESIGN/METHODS:A kinematic magnetic resonance imaging study. OBJECTIVE:To investigate the distribution of Schmorl nodes (SNs) in the lumbar spine in healthy adults, and determine the association with lumbar disk degeneration and lumbar spine motion. SUMMARY OF BACKGROUND DATA/BACKGROUND:SNs have been associated with several pathologies of the lumbar spine, although it has been demonstrated that they also occur in the healthy adult population without a clearly identified cause. A thorough understanding of SN distribution may help reveal reasons for their formation. How disk degeneration and lumbar spine motion relate to SNs is poorly understood. METHODS:Kinematic magnetic resonance images (0.6 T) were available for 1179 healthy individuals from 15 to 85 years of age. Spine specialists performed computer-based measurements. All parameters were measured and calculated automatically using the eRAD PACS Viewer (eRAD Inc., version 6.2.1.1). Lumbar disk degeneration was documented according to the Pfirrmann classification system. Lumbar spine lordosis was quantified as the angle between the inferior endplate of L1 and superior endplate of S1. The level of significance was defined as P ≤ 0.05. The distribution of SNs along the lumbar spine and their relationship with age and sex was investigated using the single factor analysis of variance χ test. The relationship between SNs, age group, disk location, and overall grades of lumbar disk degeneration were investigated by multiple logistic regression analysis. Lumbar spine motion was compared between patients with and without SNs via independent t test among 585 individuals with qualified kinematic images. Multiple logistic regression analysis was performed on associations of lumbar motion range among the SN population. RESULTS:The prevalence of SNs in our study population was 28.4%, and SNs were observed to be present more frequently in males (34.6%) than in females (20.2%) (ρ< 0.01). There was no significant difference in the incidence of SNs between age groups (ρ= 0.18). SNs were more common at the L2 and L3 vertebral bodies (14.3% and 14.4%), whereas SNs were least common at S1 vertebral bodies (1.5%). The highest incidences of SNs presentation was on disks with degeneration grade III (41.9%) and grade IV (45.3%). SN occurrence, aging, and disk location were positively correlated with lumbar disk degeneration grade. The lumbar spine range of motion was significantly different between individuals with and without SNs (31.4° vs. 37.9°, ρ< 0.01). The frequency of SNs was associated with decreased lumbar range of motion in all age groups except 51 to 60 years and 61 to 70 years. CONCLUSION/CONCLUSIONS:SNs have a high incidence in individuals without persistent lumbar disorders and were found in disks at all degrees of degeneration. SNs occurrence were positively associated with lumbar disk degeneration In addition, the presence of SNs was correlated with decreased overall lumbar motion across all age groups.

Intervertebral disc (IVD) degeneration is a complex process characterized by elevated concentrations of proinflammatory cytokines and proteolytic enzymes. Because of pro-healing constituents, we hypothesized that fibrin sealant (FS) can reduce inflammation and augment soft tissue healing within the damaged or degenerative IVD. To test this, human and porcine nucleus pulposus (NP) and annulus fibrosus (AF) cells were extracted from tissues and encapsulated into alginate beads (NP cells) and type I collagen sponges (AF cells). Half of the alginate and collagen scaffolds were embedded in FS. To provoke inflammatory behaviours, the constructs were cultured with and without continuous IL-1α (10 ng/ml) for 4, 7 and 14 days. ELISA was used to quantify the cellular synthesis (ng/µg DNA) of clinically relevant cytokines, proteolytic enzymes and growth factors. In NP cell constructs with IL-1α, the syntheses of TNFα, IL-1β, IL-6, IL-8 was elevated at all culture durations. In the presence of FS, secretion of several pro-inflammatory cytokines were significantly reduced [IL-6 and IL-8 (porcine); and TNFα, IL-1β, IL-6, IL-8 (human)]. Consistent with these reductions, human NP cultures exposed to FS and FS + IL-1α synthesized significantly reduced amounts of MMP-1 and -3 compared to constructs with IL-1α. For porcine and human AF cells, there were no significant differences in the synthesis of the inflammatory or proteolytic cytokines relative to controls (without IL-1α) at any culture duration. However, the porcine AF cells exposed to FS synthesized elevated amounts of the anti-inflammatory cytokine IL-4. The results suggest that FS may have beneficial effects for patients with degenerated intervertebral discs.

STUDY DESIGN/METHODS:Surgically denucleated porcine intervertebral discs (IVD) were injected with BIOSTAT BIOLOGX Fibrin Sealant (FS), and the in vivo effects were assessed over time by histological, biochemical, and mechanical criteria. OBJECTIVE:The objectives were to test whether the intradiscal injection of FS stimulates disc healing. SUMMARY OF BACKGROUND DATA/BACKGROUND:Disc avascularity prevents the deposition of a provisional fibrin scaffold that typically facilitates soft tissue repair. Poor disc wound healing leads to disc damage accumulation and chronic inflammation characterized by overproduction of proinflammatory cytokines and proteolytic enzymes. METHODS:Four lumbar IVDs from each of 31 Yucatan minipigs were randomized to untreated controls; degenerative injury (nucleotomy); and nucleotomy plus FS injection. Animals were killed at 1, 2, 3, 6, and 12 weeks postsurgery. IVDs were harvested to quantify (1) architecture using morphological and histological grading; (2) proteoglycan composition using DMMB assay; (3) cytokine content using ELISA; and (4) mechanical properties using quantitative pressure/volume testing. RESULTS:There was progressive invasion of annular tissue into the nucleus of nucleotomy discs and concomitant reduction in proteoglycan content. By contrast, FS supplementation inhibited nuclear fibrosis and facilitated proteoglycan content recovery over time. FS discs synthesized significantly less TNF-α than degenerate discs (66% vs. 226%, P < 0.05) and had upregulation of IL-4 (310% vs. 166%) and TGF-β (400% vs. 117%) at 2 to 3 weeks posttreatment. At the third week postsurgery, the denucleated discs were less stiff than controls (pressure modulus 779.9 psi vs. 2754.8 psi; P < 0.05) and failed at lower pressures (250.5 psi vs. 492.5 psi; P < 0.05). The stiffness and leakage pressure of the FS-treated discs recovered to control values after 6 and 12 weeks, respectively. CONCLUSION/CONCLUSIONS:FS facilitated structural, compositional, and mechanical repair of the surgically damaged IVD. These FS-derived benefits are likely due to its conductive scaffold properties and metabolically active constituents such as thrombin, factor XIII, and aprotinin acetate.

BACKGROUND CONTEXT/BACKGROUND:Harnessing the potential of stem cells is an important strategy for regenerative medicine. This study explores the use of bilaminar coculture pellets (BCPs) of mesenchymal stem cells (MSCs) and nucleus pulposus cells (NPCs) as a cell-based therapy for intervertebral disc regeneration. Prior in vitro experiments have shown that BCP can help differentiate MSCs and substantially improve new matrix deposition. PURPOSE/OBJECTIVE:To evaluate the clinical relevance of BCPs by testing the system in vivo. STUDY DESIGN/SETTING/METHODS:We have designed a novel spherical BCP where MSCs are enclosed in a shell of NPCs. The pellets were tested in vivo in a rat tail model of disc degeneration. METHODS:Rat caudal intervertebral discs were denucleated and treated with BCP in a fibrin sealant (FS) carrier (controls were MSCs suspended in FS; NPCs suspended in FS; MSCs and NPCs suspended in FS; FS only; and surgery only). At 14 and 35 days after implantation, the animals were euthanized and discs were evaluated for proteoglycan content, enzyme-linked immunosorbent assay for inflammatory cytokines, cell retention using polymerase chain reaction, disc height, histology, and disc grade based on a blinded scoring system. RESULTS:The proteoglycan and cytokine levels were not significantly different among groups. The BCP group had higher cell retention than controls. Disc height and disc grade increased over time only in the BCP group. Bilaminar coculture pellets were the only treatment to show proteoglycan staining in the nucleus space at 35 days. CONCLUSIONS:This study shows that BCPs may prevent postnucleotomy disc degeneration in vivo. Larger animals and longer time points will be necessary to further judge potential clinical impact. As opposed to strategies that require growth factor supplements, predifferentiation, or genetic manipulations, BCPs are a self-sustaining and targeted method for tissue regeneration in situ.

STUDY DESIGN/METHODS:The influence of mechanical load on pleiotrophin (PTM) and aggrecan expression by intervertebral disc (IVD) cells, and the effects of disc cell conditioned medium on endothelial cell migration was investigated. OBJECTIVE:To examine possible interactions of mechanical loads and known pro- and antiangiogenic factors, which may regulate disc angiogenesis during degeneration. SUMMARY OF BACKGROUND DATA/BACKGROUND:Pleiotrophin expression can be influenced by mechanical stimulation and has been associated with disc vascularization. Disc aggrecan inhibits endothelial cell migration, suggesting an antiangiogenic role. A possible interplay between these factors is unknown. METHODS:The influence of the respective predominant load (cyclic strain for anulus fibrosus and hydrostatic pressure for nucleus pulposus cells) on PTN and aggrecan expression by IVD cells was determined by real-time RT-PCR and Western blotting (PTN only). The effects of IVD cell conditioned medium on endothelial cell migration were analyzed in a bioassay using human microvascular endothelial (HMEC-1) cells. RESULTS:Application of both mechanical loads resulted in significant alterations of gene expression of PTN (+67%, P = 0.004 in anulus cells; +29%, P = 0.03 in nucleus cells) and aggrecan (+42%, P = 0.03 in anulus cells, -25%, P = 0.03 in nucleus cells). These effects depended on the cell type, the applied load, and timescale. Conditioned media of nucleus pulposus cells enhanced HMEC-1 migration, but this effect was diminished after 2.5 MPa hydrostatic pressure, when aggrecan expression was diminished, but not 0.25 MPa, when expression levels were unchanged. CONCLUSION/CONCLUSIONS:Mechanical loading influences PTN expression by human IVD cells. Conditioned media from nucleus pulposus cell cultures stimulated HMEC-1 endothelial cell migration. This study demonstrates that the influence of mechanical loads on vascularization of the human IVD is likely to be complex and does not correlate simply with altered expression of known pro- and antiangiogenic factors.