gms | German Medical Science

Objectives: Intervertebral disc (IVD) degeneration represents a major public health problem worldwide and is often associated with severe back pain. IVD degeneration (IVDD) is characterised by an imbalance of matrix anabolism and catabolism that consequently leads to a reduced amount of matrix in the disc. A number of inflammatory cytokines induce degradation of matrix proteins, leading to reduced hydration of the disc that finally results in spine instability. In contrast to these catabolic factors, Transforming Growth Factor beta 1 (TGFb1) is one of the anabolic factors increasing the production of matrix proteins like aggrecan and collagen. In our study we are analysing differences in the TGFb1 expression and the TGFb1 signalling pathway of annulus fibrosus (AF) tissue and cells derived from patients with IVDD to find new treatment strategies.

Methods: IVDs of the lumbar spine were scored according to the Modified Pfirrmann Score and divided into mild degeneration (score of 1-4) and severe degeneration (score of 6-8). All donors gave written informed consent (approval EA4/004/16). AF tissue was enzymatically digested and the amount of TGFb1 protein was measured by ELISA. To analyse TGFb1 signalling, cells were enzymatically isolated from AF tissue and stimulated with recombinant TGFb1 protein for selected time points between 6 and 48 hours. Subsequently, RNA was isolated and transcribed into cDNA for gene expression analysis by qRT-PCR.

Results and Conclusion: We observed significant higher levels of TGFb1 in AF tissues obtained from donors with mild IVDD (n=13) compared to donors with severe IVDD (n=23) (Figure 1 [Fig. 1]). For comparison of the two groups the unpaired, two-tailed Mann-Whitney U test was used. In preliminary experiments (n=2-3 per group) analysing TGFb1 signalling, we observed differences between cells isolated from donors with mild IVDD compared to those with severe IVDD. In chondrocytes of severe IVDD donors, TGFb1 stimulation increased collagen10 expression, a marker for differentiation of the hypertrophic phenotype. In contrast, cells from donors with mild IVDD showed elevated collagen1 transcription levels upon TGFb1 stimulation.

Our results demonstrate that in IVDs with severe degeneration the amount of TGFb1 protein is reduced. The reduced TGFb1 availability results in a lower matrix production and might be one of the reasons for the reduced matrix content in IVDD. In addition our data show that TGFb1 signalling is altered in IVDD implying molecular changes of the cell characteristics during degeneration processes. Understanding of these molecular mechanisms changed during degeneration will support to find new treatment strategies for IVDD.