Degeneration of Lumbar Intervertebral Discs: Characterization of Anulus Fibrosus Tissue and Cells of Different Degeneration Grades

Abstract

Intervertebral disc (IVD) herniation and degeneration is a major source of back pain. In order to regenerate a herniated and degenerated disc, closure of the anulus fibrosus (AF) is of crucial importance. For molecular characterization of AF, genome-wide Affymetrix HG-U133plus2.0 microarrays of native AF and cultured cells were investigated. To evaluate if cells derived from degenerated AF are able to initiate gene expression of a regenerative pattern of extracellular matrix (ECM) molecules, cultivated cells were stimulated with bone morphogenetic protein 2 (BMP2), transforming growth factor β1 (TGFβ1) or tumor necrosis factor-α (TNFα) for 24 h. Comparative microarray analysis of native AF tissues showed 788 genes with a significantly different gene expression with 213 genes more highly expressed in mild and 575 genes in severe degenerated AF tissue. Mild degenerated native AF tissues showed a higher gene expression of common cartilage ECM genes, whereas severe degenerated AF tissues expressed genes known from degenerative processes, including matrix metalloproteinases (MMP) and bone associated genes. During monolayer cultivation, only 164 differentially expressed genes were found. The cells dedifferentiated and altered their gene expression profile. RTD-PCR analyses of BMP2- and TGFβ1-stimulated cells from mild and severe degenerated AF tissue after 24 h showed an increased expression of cartilage associated genes. TNFα stimulation increased MMP1, 3, and 13 expression. Cells derived from mild and severe degenerated tissues could be stimulated to a comparable extent. These results give hope that regeneration of mildly but also strongly degenerated disc tissue is possible.

Identification of Core Genes and Screening of Potential Targets in Intervertebral Disc Degeneration Using Integrated Bioinformatics Analysis

“…Intervertebral disc degeneration (IDD) is recognized as the major cause of LBP ( Smolders et al, 2013 ). Current treatment of IDD, including conservative therapies and surgical interventions, often only alleviates the patients’ pain without preventing the progression of IDD ( Stich et al, 2020 ). Furthermore, the clinical results are suboptimal ( Wang H. et al, 2020 ).…”

Mechanical Stretch Induced Osteogenesis on Human Annulus Fibrosus Cells through Upregulation of BMP-2/6 Heterodimer and Activation of P38 and SMAD1/5/8 Signaling Pathways

“…Jin et al also demonstrated that an osteogenic medium could induce osteogenic transformation of rabbit AF cells by increased mineralization and expressions of Runx2, BMP-2, and osteopontin genes [ 18 ]. On the other hand, Stich et al used genome-wide microarray to evaluate the differences between human lumbar AF tissues from mild and severe degenerated IVDs and the results exhibited that Runx2 and other osteogenic-related genes were highly expressed in native AF tissues of severe degenerated IVD [ 48 ]. Similarly, Yeh et al confirmed that human AF cells of degenerated IVDs exhibited a higher tendency to osteogenic differentiation over native AF cells by an increase in the expression of mRNAs for BMP-2, Runx2, ALP, and osteocalcin and calcium deposition over native AF cells [ 49 ].…”

Advanced Strategies for the Regeneration of Lumbar Disc Annulus Fibrosus

“…Moreover, the selection of appropriate therapeutic genes, while important, is difficult and requires extensive knowledge of the pathogenesis of degradation, specifically timing and stage of degeneration. Besides, the AF cell apoptosis in degenerated IVDs is a barrier to the successful execution of gene-based therapies [ 95 , 96 , 97 ].…”

“…The effect of growth differentiation factors (GDFs) to enhance the anabolism-catabolism ratio in the ECM has been considered as an effective biomolecule-based regenerative strategy [ 93 , 97 ]. An increasing body of evidence indicated that GDFs were central to the IVD homeostatic processes, upregulation of the healthy cell marker genes in degenerative cells, and differentiation of mesenchymal stem cells to the NP cells [ 98 , 99 , 100 ].…”