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Lumbar disc disease (LDD) is common in aged populations, and it is primarily caused by intervertebral disc degeneration (IDD). Cartilage intermediate layer protein (CILP), which is specifically expressed in intervertebral discs (IVDs), is suspected to be associated with IDD. However, it remains unclear whether CILP contributes to IDD in humans. Furthermore, the regulation of CILP in human IVDs is poorly understood, especially by mechanical stimuli, which are regarded as primary factors promoting IDD. To address these issues, the present study collected nucleus pulposus (NP) cells from patients undergoing lumbar spinal surgery for degenerative disc disease (DDD). Subsequently, CILP expression was measured in human NP cells in response to mechanical stimuli, including cyclic compressive stress and cyclic tensile strain (CTS), by reverse transcription‑quantitative polymerase chain reaction and western blotting. Aggrecan and collagen II, which are the main components of the extracellular matrix (ECM) and traditional degenerative markers for IDD, were detected following the treatment with CILP small interfering (si)RNA or recombinant human CILP (rhCILP) at various concentrations to determine whether CILP contributes to IDD by negatively regulating expression of the ECM. The results revealed that CILP expression in loaded NP cells was significantly increased compared with that in non‑loaded cells under compressive loading, and that it was markedly decreased in cells under tensile loading, in contrast with the expression of aggrecan and collagen II in response to the same stimuli. Furthermore, CILP siRNA effectively inhibited CILP expression and significantly increased the expression of aggrecan and collagen II. In addition, treatment of NP cells with a high concentration of rhCILP resulted in significantly decreased expression of aggrecan and collagen II. In conclusion, these results demonstrated for the first time, to the best of our knowledge, that in human NP cells, CILP is regulated by mechanical stress and that its expression affects ECM synthesis. Therefore, CILP represents a promising therapeutic target for preventing loss of the matrix during IDD as a novel treatment strategy. [ABSTRACT FROM AUTHOR]

Mechanical compression is important in disc degeneration. N-cadherin (N-CDH)-mediated signaling contributes to the maintenance of the normal nucleus pulposus (NP) cell phenotype and NP matrix biosynthesis. Our preliminary study demonstrated that a high-magnitude compression (20% deformation) promotes NP cell senescence in a three-dimensional scaffold culture system. The aim of the present study was to investigate whether N-CDH-mediated signaling alleviates NP cell senescence under the above-mentioned high-magnitude compression. NP cells were transfected with recombinant lentiviral vectors to enhance N-CDH expression. All the transfected or un-transfected NP cells were seeded into the scaffolds and subjected to 20% deformation at a frequency of 1.0 Hz for 4 h once per day for 5 days. Results indicated that N-CDH overexpressed NP cells exhibited decreased senescence-associated β-galactosidase activity and downregulated expression levels of senescence-associated markers (p16 and p53). Furthermore, the N-CDH overexpressed NP cells exhibited increased cell proliferation potency, telomerase activity and matrix biosynthesis compared with NP cells without N-CDH overexpression under high-magnitude compression. Thus, N-CDH-mediated signaling contributes to the attenuation of NP cell senescence under high-magnitude compression. [ABSTRACT FROM AUTHOR]

Degenerative disc disease (DDD) is a common degenerative condition initiated mainly within the nucleus pulposus (NP). To date, the etiopathogenesis of DDD remains unclear, and because no effective therapeutic strategies are available to target its pathological processes, DDD is still treated with symptomatic interventions that are far from adequate. Collagen type II is one of the major matrix components of the NP, and is considered to be essential to NP homeostasis. However, the specific mechanisms by which collagen type II influences NP cells remain unknown. In the present study, collagen type II expression was detected using immunohistochemistry analysis and quantitative polymerase chain reaction, and it was demonstrated to be significantly downregulated in NP tissues from patients with DDD compared with nondegenerative controls. To further explore the mechanism in vitro, interleukin (IL)‑1β stimulation was used to induce degeneration of a human NP cell line. IL‑1β stimulation upregulated both the mRNA and protein levels of the catabolic markers matrix metalloproteinase 13 (MMP13) and a disintegrin and metalloproteinase with thrombospondin motifs 4 (ADAMTS4), while it downregulated the anabolic makers aggrecan and collagen type II. However, addition of purified collagen type II prevented this IL‑1β‑induced metabolic disturbance of the NP cells. Furthermore, IL‑1β stimulation significantly promoted apoptosis in NP cells, while collagen type II treatment decreased the apoptotic rate and the protein levels of cleaved caspase‑3. In conclusion, collagen type II exhibited protective effects in suppressing NP cell degeneration through its anticatabolic, proanabolic and antiapoptotic effects, suggesting that it may be a promising therapeutic agent for the prevention and treatment of DDD. [ABSTRACT FROM AUTHOR]