Cartilage intermediate layer protein is regulated by mechanical stress and affects extracellular matrix synthesis
MOLECULAR MEDICINE REPORTS
Authors: He, Jinyue; Feng, Chencheng; Sun, Jing; Lu, Kang; Chu, Tongwei; Zhou, Yue; Pan, Yong
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.
Expression of cartilage intermediate layer protein/nucleotide pyrophosphohydrolase parallels the production of extracellular inorganic pyrophosphate in response to growth factors and with aging
ARTHRITIS AND RHEUMATISM
Authors: Hirose, J; Masuda, I; Ryan, LM
Objective, To evaluate the role of the extracellular inorganic pyrophosphate (ePPi)-generating ectoenzyme cartilage intermediate layer protein/nucleotide pyrophosphohydrolase (CILP/NTPPH) in chondrocyte PPI elaboration, we studied CILP/NTPPH expression in response to growth factors during aging. Methods. Porcine chondrocytes from adult (3-4-year-old) and young (2-week-old) animals were stimulated with transforming growth factor beta1 (TGF beta1), which enhances ePPi elaboration, and/or insulin-like growth factor 1 (IGF-1), which diminishes ePPi elaboration. Measurements of ePPi, NTPPH enzyme activity, Western blot analysis, reverse transcriptase-polymerase chain reaction (RT-PCR), and Northern blot analysis were performed. Results. Elaboration of ePPi into conditioned media from adult chondrocytes was significantly increased by TGF beta1 and significantly inhibited by IGF-1, but no significant differences were observed in young chondrocytes. The protein levels of CILP/NTPPH by Western analysis in the media from adult and young porcine chondrocytes were increased by TGF beta1, RT-PCR and Northern analysis showed that CILP/NTPPH messenger RNA (mRNA) expression in both adult and young chondrocytes was increased by TGF beta1 and decreased by IGF-1, but these changes were less significant in the young chondrocytes, Basal and TGF beta1-upregulated levels of CILP/NTPPH expression were higher in adult chondrocytes than in young chondrocytes, Conclusion. These results provide evidence that CILP/NTPPH expression and ePPi elaboration are concomitantly stimulated by TGF beta1 and down-regulated by IGF-1, especially in adult chondrocytes, implicating CILP/NTPPH as a functional participant in ePPi elaboration. Increased CILP/NTPPH mRNA expression in chondrocytes derived from aged animals compared with young animals might promote the formation of calcium pyrophosphate dihydrate crystals in aged cartilage.