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* These authors contributed equally
This protocol presents a novel experimental model of proinflammatory, degenerative bovine organ culture to simulate early-stage intervertebral disc degeneration.
Symptomatic intervertebral disc (IVD) degeneration (IDD) is a major socioeconomic burden and is characterized by inflammation and tissue degradation. Due to the lack of causative therapies, there is an urgent need for innovative experimental organ culture models to study the mechanisms involved in the progression of the disease, find therapeutic targets, and reduce the need for animal models. We here present a novel, three-dimensional organ culture model protocol mimicking the proinflammatory and catabolic microenvironment, which is present during IDD.
Initially, bovine caudal IVDs were dissected, cleaned, and cultured in the tissue culture medium. Dynamic physiologic or pathologic loading was applied in a custom-made bioreactor for 2 hours per day. IVDs were assigned to a control group (high glucose medium, physiological loading, phosphate-buffered saline injection) and a pathological group (low glucose medium, pathological loading, tumor necrosis factor-alpha injection) for four days. Gene expression analysis from collected nucleus pulposus cells of the IVDs and enzyme-linked immunosorbent assay of the conditioned organ culture media was performed.
Our data revealed a higher expression of inflammatory markers and reduced disc heights after loading in the pathological group compared to the control group. This protocol is reliable to simulate IVD inflammation and degeneration and can be further expanded to broaden its application scope.
Low back pain (LBP) can affect individuals of all ages and is a leading cause for disability worldwide1,2,3. The total cost associated with LBP exceeds $100 billion per year4,5. Symptomatic intervertebral disc (IVD) degeneration (IDD), a condition characterized by inflammation and tissue degradation, is a major cause of LBP6,7. Specifically, IDD is characterized by a gradually evolving breakdown of the IVD's extracellular matrix (ECM), induced and triggered by multiple factors that lead to an accelerated pathology, neurological disorders, and eventually disability. Furthermore, IDD is associated with the release of proinflammatory cytokines, altered spine biomechanics, angiogenesis, and nerve ingrowth, which increases pain sensation, altogether causing chronic LBP (active discopathy)6,8. To date, treatment options include discectomy and subsequent fusion of the adjacent vertebrae, implantation of an IVD prosthesis, or non-surgical approaches, such as non-steroidal anti-inflammatory drugs, opioids, and muscle relaxants for patients with IDD9. Both current standard therapeutic options, surgical and non-surgical, are only partly effective and fail to address the underlying biological problem9,10. Early-stage degenerative disc disease is characterized by an initial inflammatory tissue response, especially an increase in tumor necrosis factor-alpha (TNF-alpha) expression11. These early disc changes primarily occur at the cellular level without disrupting the disc architecture and could previously be mimicked by nutritional deficiency under pro-inflammatory conditions12. Therefore, precise simulation of the in vivo situation to investigate these degeneration mechanisms and find suitable therapeutic targets is crucial. Additionally, to these simulations of molecular properties, the mechanical loading environment of the discs plays a key role in pathological and physiological changes of IVD. Consequently, combining these approaches would bring us one step forward to mimic the complex microenvironment of IVDs in vivo. There are currently no studies considering the aspect of dynamic loading along with the pro-inflammatory and nutritional setting to the best of our knowledge.
Although large animal models allow the investigation of potential relevant in vivo interactions, they are costly and work intensive. Moreover, as the use of animal models in research has long been a matter of controversy, the reduction of the number of animals needed to answer important research questions is of great interest. Finally, there is currently no ideal animal model to mimic IDD in IVD research13,14. Therefore, it is necessary to establish a cost-effective and reliable replacement, such as an organ culture model to simulate IDD and associated inflammatory and degenerative processes. Recently, the application of the present protocol on the establishment of a proinflammatory and degenerative organ culture model to simulate early-stage intervertebral disc disease allowed us to investigate the effect of anti-inflammatory drugs in the IDD organ culture15.
Here, we describe how to obtain bovine intervertebral discs and induce the state of early-stage IDD via a catabolic and proinflammatory microenvironment caused by direct intradiscal injection of tumor necrosis factor-alpha (TNF-α) and degenerative loading in a bioreactor under low nutritive medium conditions. Figure 1 illustrates the experimental model and shows the bioreactor used to simulate degenerative and physiological loading conditions.
Figure 1: Illustration of the experimental setup. A: bovine tail; B: dissected bovine intervertebral discs; C: transfer of the disc to a well-plate with culture medium; D: loading the simulation in a bioreactor; E: intradiscal injection technique; F: IVD after injection of PBS/trypan blue dye to reveal distribution. IDD: intervertebral disc degeneration. Please click here to view a larger version of this figure.
Experiments were performed using bovine tails obtained from local abattoirs. The biological materials used in the current study are taken from the food chain and require no ethical approval in Swiss and European law.
1. Dissection of the bovine intervertebral disc
2. IVD culture and loading
3. Intradiscal tumor necrosis factor-alpha (TNF-α) injection
4. Gene expression
5. Quantification of protein content in the IVD medium
Degenerative loading in low glucose medium combined with TNF-α injection caused a significant increase of the gene expression of proinflammatory markers interleukin 6 (IL-6) and interleukin 8 (IL-8) compared to the physiological control group in NP cells after 4 days of culture (Figure 2). In contrast, we did not observe significant changes for the proinflammatory genes interleukin 1β (IL-1β) and TNF-α in NP cells (data not shown). Furthermore, degenerative culture condit...
We here provided a detailed protocol to simulate degenerative and inflammatory IVDD. This protocol can be applied for detailed examinations of inflammatory pathways leading to the destructive effects on the disc. Moreover, the protocol can help to determine promising therapeutic targets involved in the progression of the disease.
We recently showed that human recombinant TNF-α could induce inflammation in both bovine and human NP cells21, which is in accordance wit...
The authors have nothing to disclose.
This work was supported by AO Foundation and AOSpine International. Babak Saravi received fellowship support from the German Spine Foundation and the German Osteoarthritis Foundation. Gernot Lang was supported by the Berta-Ottenstein-Programme for Advanced Clinician Scientists, Faculty of Medicine, University of Freiburg, Germany.
Name | Company | Catalog Number | Comments |
1-Bromo-3-chloropropane(BCP) | Sigma-Aldrich, St. Louis, USA | B9673 | |
Ascorbate-2-phosphate | Sigma-Aldrich, St. Louis, USA | A8960 | |
Band saw | Exakt Apparatebau, Norderstedt, Germany | model 30/833 | |
Betadine | Munndipharma, Frankfurt, Germany | ||
Bovine IL-8 Do.it-Yourself ELISA | Kingfisher Biotech, St. Paul, USA | DIY1028B-003 | |
Corning ITS Premix | Corning Inc., New York, USA | 354350 | |
DMEM high glucose | Gibco by life technologies, Carlsbad, USA | 10741574 | |
DMEM low glucose | Gibco by life technologies, Carlsbad, USA | 11564446 | |
Ethanol for molecular biology | Sigma-Aldrich, St. Louis, USA | 09-0851 | |
Fetal Bovine Serum (FBS) | Gibco by life technologies, Carlsbad, USA | A4766801 | |
Non-essential amino acid solution | Gibco by life technologies, Carlsbad, USA | 11140050 | |
Penicillin/Streptomycin(P/S) | gibco by life technologies, Carlsbad, USA | 11548876 | |
Phosphate Buffer Solution, tablet | Sigma-Aldrich, St. Louis, USA | P4417 | |
Pronase | Sigma-Aldrich, St. Louis, USA | 10165921001 | |
Primocin | InvivoGen, Sandiego, USA | ant-pm-05 | |
Pulsavac Jet Lavage System | Zimmer, IN,USA | ||
TissueLyser II | Quiagen, Venlo, Netherlands | 85300 | |
Streptavidinn-HRP | Kingfisher Biotech, St. Paul, USA | AR0068-001 | |
Superscript VILO | Invitrogen by life Technologies, Carlsbad, USA | 10704274 | |
cDNA Synthesis Kit | Applied Biosystems by life technologies | 10400745 | |
TaqMan Universal Master Mix | Applied Biosystems by life technologies | ||
TNF-alpha, recombinant human protein | R&D systems, Minnesota, USA | 210-TA-005 | |
TRI Reagent | Molecular Research Center, Cincinnati, USA | TR 118 | |
Tris-EDTA buffer solution | sigma-Aldrich, St. Louis, USA | 93283 | |
Gene bIL-6 | Applied Biosystems by life technologies | Custom made probes | Primer fw (5′–3′) TTC CAA AAA TGG AGG AAA AGG A Primer rev (5′–3′) TCC AGA AGA CCA GCA GTG GTT Probe (5′FAM/3′TAMRA) CTT CCA ATC TGG GTT CAA TCA GGC GATT |
Gene bIL8 | Applied Biosystems by life technologies | Bt03211906_m1 | |
Gene bTNF-alpha | Applied Biosystems by life technologies | Custom made probes | Primer fw (5′–3′) CCT CTT CTC AAG CCT CAA GTA ACA A Primer rev (5′–3′) GAG CTG CCC CGG AGA GTT Probe (5′FAM/3′TAMRA) ATG TCG GCT ACA ACG TGG GCT ACC G |
GENE bIL1beta | Applied Biosystems by life technologies | Custom made probes | Primer fw (5′–3′) TTA CTA CAG TGA CGA GAA TGA GCT GTT Primer rev (5′–3′) GGT CCA GGT GTT GGA TGC A Probe (5′FAM/3′TAMRA) CTC TTC ATC TGT TTA GGG TCA TCA GCC TCA A |
RPLP0 | Applied Biosystems by life technologies | Bt03218086_m1 |
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