Yejia Zhang

Intervertebral disk repair by protein, gene, or cell injection: a framework for rehabilitation-focused biologics in the spine.

Low back pain carries an enormous socioeconomic burden. Current treatment modalities for symptomatic intervertebral disk (IVD) degeneration have limited and often inconsistent clinical benefits. Novel approaches with the potential to halt or even reverse disk degeneration and restore physiologic disk function, such as biological treatments, are therefore very attractive. The following barriers are impeding the development of successful therapeutic interventions: (1) the biology and pathophysiology of disk degeneration are not well understood, and (2) the precise relationship between IVD degeneration and low back pain remains unclear. This article reviews the structural changes that take place during IVD degeneration and their relationship to diskogenic back pain. It also presents treatment modalities that currently are under laboratory investigation and are being studied in clinical trials. The authors of recent studies have shown that the content of large proteoglycans, such as aggrecan and versican, decreases with aging and IVD degeneration, whereas the content of certain small proteoglycans, such as biglycan, increases. Proinflammatory cytokines such as interleukin‐1 and tumor necrosis factor‐α also are associated with IVD degeneration and are potential biomarkers of IVD degeneration and repair. Our group of investigators and others have developed in vitro models of IVD cell and explant culture in addition to in vivo animal models to study IVD degeneration and repair. With the use of these models, we have tested candidate therapeutic agents to assess their therapeutic potential for matrix restoration. When a rabbit annular puncture model of IVD degeneration was used, injections of either bone morphogenetic protein‐7 (also known as osteogenic protein‐1) or bone morphogenetic protein‐14 (also known as growth differentiation factor‐5) were shown to be effective in restoring IVD structures. On the basis of these data, the Food and Drug Administration has recently allowed the initiation of Investigational New Drug clinical trials on osteogenic protein‐1 and growth differentiation factor‐5 in the United States. Protein therapies such as other growth factors, inhibitors of degradation enzymes or cytokines, and cell therapies also are being investigated in laboratory settings with the goal of restoring disk function and alleviating back pain symptoms. These therapies may be used by physiatrists with the skills required to administer intradiskal injections and supervise a comprehensive rehabilitation program after the procedures. Ultimately, the clinical use of any biological treatment discussed in this article would require the collective efforts of clinicians and researchers.

Primary bovine intervertebral disc cells transduced with adenovirus overexpressing 12 BMPs and Sox9 maintain appropriate phenotype.

Zhang Y, Markova D, Im H-J, Hu W, Thonar EJ-MA, He T-C, An HS, Phillips FM, Anderson DG: Primary bovine intervertebral disc cells transduced with adenovirus over-expressing 12 BMPs and Sox9 maintain appropriate phenotype. Objective:To confirm that primary intervertebral disc cells cultured in monolayer transduced with adenovirus maintained their phenotype, hence is an appropriate system to test gene therapy agents. Design:Adult bovine nucleus pulposus and anulus fibrosus cells cultured in monolayer were transduced with adenoviruses expressing human bone morphogenetic proteins (AdBMPs) or Sox9 (AdSox9), or green fluorescence protein (AdGFP, as control). Chondrocyte phenotypic markers (e.g., type II collagen and aggrecan) and the chondrocyte hypertrophy marker (type X collagen) were measured 6 days after viral transduction by reverse-transcription polymerase chain reaction. Results:Primary nucleus pulposus and anulus fibrosus cells transduced with AdBMPs, AdSox9, or adenovirus-expressing green fluorescence protein only (AdGFP, as control) continue to express healthy chondrocyte phenotypic markers and showed no evidence of the expression of the chondrocyte hypertrophy marker (type X collagen gene). Thus, we have shown that bovine nucleus pulposus and anulus fibrosus cells transduced with adenovirus overexpressing 12 different bone morphogenetic proteins or Sox9 maintain their phenotype in short-term culture. Conclusions:In this study, primary bovine intervertebral disc cells transduced with adenovirus overexpressing 12 bone morphogenetic proteins or Sox9 preserved their phenotype in short-term culture. These cells did not express the type X collagen gene, an undesirable chondrocyte hypertrophic gene that could lead to ossification. Therefore, low-passage intervertebral disc cells cultured in monolayer is an appropriate culture system to test therapeutic genes. We further suggest that these cells may also be appropriate for engineering tissues or for cell therapy for degenerative disc diseases.

Sensory neurons and fibers from multiple spinal cord levels innervate the rabbit lumbar disc.

Zhang Y, Kerns JM, Anderson DG, Lee YS, Chen E-Y, Tannoury C, An HS: Sensory neurons and fibers from multiple spinal cord levels innervate the rabbit lumbar disc. Am J Phys Med Rehabil 2006;85:865–871. Objective:To establish the neurotransmission pathway from the lumbar L5/6 intervertebral disc (IVD) to the spinal cord in the rabbit. Design:Fluorogold particles injected into the posterior portion of the rabbit L5/6 IVD were traced by examining gold-positive neurons and fibers in the dorsal root ganglion (DRG) and spinal cord at various root levels. Results:Fluorogold-labeled neurons were observed bilaterally in primary afferent DRG neurons from the L3 through L5 segments; a small number of gold-labeled neurons were found at the L1 level. Fluorogold-labeled neurons were predominantly present in the ipsilateral DRG (the side of the injection) at the L5 level, but they were more equally distributed (on both sides) at the L4 and L3 levels. In the posterior horn of the spinal cord, Fluorogold particles were found in nerve fibers as rostral as the T12 level. Conclusions:Our study has shown that Fluorogold particles injected into the rabbit L5/6 IVD are taken up by primary sensory neurons in the DRGs and primary sensory fibers in the posterior horn of the spinal cord at multiple levels. This diffuse innervation pattern of the lumbar disc may help explain why discogenic back pain in humans is often poorly localized.

Retroperitoneal approach to the intervertebral disc for the annular puncture model of intervertebral disc degeneration in the rabbit

BACKGROUND CONTEXT The rabbit annular puncture model of degeneration is among the most widely used models of intervertebral disc (IVD) degeneration. There are no published reports of the specific surgical technique used to produce this model. PURPOSE To describe the model in detail in an effort to reduce center-to-center variability and hopefully improve the reproducibility of future experimental results. STUDY DESIGN Technical report of surgical approach and experience. PATIENT SAMPLE New Zealand White Rabbits. METHODS A detailed report of the annular puncture technique in rabbits is provided including preparation of the animals, instrumentation, a description of retroperitoneal approach to the lumbar area, and the technique for IVD injury. Common pitfalls and complications of the procedure are described. CONCLUSIONS The methods described can serve to standardize the implementation of this important preclinical model of disc degeneration.

The Nonsurgical Treatment of Back Pain

Each spinal motion segment is a three-joint complex comprised of the intervertebral disc, two facet joints, and a host of ligamentous and muscular attachments. This complex allows for multiaxial movement and loading of the spine while maintaining an upright posture and protection of the neural elements. The anatomic complexity of this articulation has complicated the search for a specific pathoanatomic cause for low back pain. The most common etiologies can be broadly categorized as neural, muscular, osseous, disc-related, and facet-related and have been the subject of much debate (Lutz et al. 2003). In the early decades of the twentieth century, nerve dysfunction, including neuritis and neuralgia, as well as muscular dysfunction were proposed as the leading causes of back pain. As the use of radiographs became more widespread, the classic bony changes associated with disc degeneration and spondylosis were found in many patients complaining of low back pain; hence, osseous etiologies became a popular theory. Initially, an inflammatory etiology for these bony changes was assumed; however, when no consistent marker of inflammation was found, it was then seen as a degenerative disorder. In the late 1930s and early 1940s, intervertebral disc pathology began to be recognized as a major low back pain generator (Barr 1938; Key 1945) and became the dominant theory for several decades. This resulted in an increase in the number and variety of surgical procedures directed at the intervertebral disc. By the end of the twentieth century, evidence emerged that anatomic abnormalities, as visualized by diagnostic imaging tests, often did not correlate with clinical symptoms (Boden et al. 1990). As a result, most modern treatments for low back pain are pragmatic in approach rather than searching for a specific anatomic directed cause (Lutz et al. 2003), with nonsurgical intervention taking center stage.

413 CYTOKINE PROFILE IN INTERVERTEBRAL DISC TISSUES FROM PATIENTS WITH DISCOGENIC AXIAL BACK PAIN CONFIRMED BY DISCOGRAPHY

Background: Opioids remain unsurpassed analgesics to relieve pain. However, it has been shown that opioids increase postoperative pain and hypersensitivity. Animal studies reported that nitrous oxide (N2O) prevents hyperalgesia, induced due to large perioperative doses of opioids. This trial was designed to evaluate the effect of N2O on hypersensitivity induced by both, nociceptive inputs and remifentanil, in healthy volunteers. Methods: Twenty-one volunteers have been connected to an electrical stimulation device, generating pain intensity of 60mm on a 100mm VAS. Intensity was kept constant for 160 minutes. Each volunteer underwent four sessions at random: Placebo group: 50%–50% N2-O2 and placebo; Remifentanil group: 50%–50% N2-O2 and remifentanil with 0.1mg/kg/min; N2O group 50%–50% N2OO2 and placebo; N2O+ Remifentanil group: 50%–50% N2O-O2 and i.v. remifentanil with 0.1mg/kg/min. Inhaled gas mixtures started from T20 to T80 and i.v. administration of remifentanil or placebo started from T50 to T80. Pin-prick hyperalgesia and allodynia were assessed at T0, T10 and then every 15 minutes. VAS pain was rated in 5-minute intervals. Results: Hyperalgesia in Remifentanil group was observed from T110. Mean area of hyperalgesia was significantly reduced in N2O + Remifentanil group versus Remifentanil group (35.88±22.37 vs. 43.55±18.48cm2, p = 0.004). Mean area of allodynia was significantly reduced in N2O + Remifentanil group versus Remifentanil group (29.95±16.15 vs. 34.80±15.35cm2, p = 0.008). Mean of pain intensity was significantly reduced in N2O + Remifentanil group versus Remifentanil group (37.96±12.78 vs. 42.15±13.34mm, p < 0.0001). Conclusion: N2O reduces hyperalgesia, allodynia and pain intensity significantly after remifentanil administration.