gms | German Medical Science

Objectives: Degenerative disc disease (DDD) is characterized by degradation of extracellular matrix, release of proinflammatory cytokines and altered spinal biomechanics and is the main cause of low back pain (LBP). Disease modifying anti-rheumatic drugs (DMARDs) recently showed their potential in the treatment of LBP. The present study investigates the effects of the TNF-α-inhibitor Etanercept and the selective JAK3-inhibitor Tofacitinib on inflammation and degeneration in an ex vivo intervertebral disc (IVD) organ culture model.

Methods: Bovine caudal IVDs were cultured in a bioreactor for 4 days to simulate the degenerative conditions of mechanical and nutritional strain. The control group was cultured under physiological loading (0.02-0.2 MPa; 0.2 Hz; 2h/day) and high glucose (4.5g/L) medium. Degeneration was induced by detrimental loading (0.32-0.5 MPa; 5Hz; 2h/day) and low glucose (2g/L) medium. TNF-α was injected into the nucleus pulposus (100ng/IVD) to trigger inflammation.

Drug treatment was performed by either intradiscal injection of Etanercept (3.5mg/IVD) or addition of Tofacitinib (2.5µg/ml) to the culture medium. Gene expression was measured in the IVD tissue. Nitric oxide (NO), glycosaminoglycan (GAG) and cytokine release were determined in conditioned medium. One-way ANOVA or Kruskal-Wallis tests were used to determine statistical differences (n=6-8).

Results and conclusion: Degenerative culture condition and TNF-α injection significantly upregulated the expression of proinflammatory cytokines IL-1β, IL-6, and IL-8, catabolic enzymes MMP1 and MMP3, cyclooxygenase-2 (COX-2) and nerve growth factor (NGF). Degenerative culture condition and TNF- α injection induced release of GAG and NO compared to control group and caused an upregulation of IL-8 protein release. Both Etanercept injection and the addition of Tofacitinib to the culture medium showed a partial reduction of the proinflammatory and degenerative effects on gene expression levels of IL-1β, IL-6 and IL-8 with a stronger effect on the NP cells. Etanercept seems to have a stronger effect on the interleukins than Tofacitinib. Treatment with the drugs showed no effect on IL-6 and IL-8 protein release to the medium. Etanercept partial reduced NO and GAG release into the medium, Tofacitinib showed a partial reduction of cumulative GAG release and had none effect on NO release.

The combination of detrimental dynamic loading, limited nutrition and intradiscal injection of TNF-α could synergistically mimic the proinflammatory and biomechanical conditions within a degenerative IVD. Though targeting different inflammatory pathways and administered differently, both drugs indicate similar potential to slow down inflammation by reduced expression of proinflammatory cytokines. Though, combination of anti-inflammatory treatment and anabolic treatment may be required to completely stop or reverse the degenerative processes. Furthermore, our ex vivo model showed its potential for further screening of treatments of DDD.