Cartilage intermediate layer protein promotes lumbar disc degeneration

Lumbar disc disease (LDD) is one of the most common musculoskeletal disorders, and accompanies intervertebral disc degeneration. CILP encodes cartilage intermediate layer protein, which is highly associated with LDD. Moreover, CILP inhibits transcriptional activation of cartilage matrix genes in nucleus pulposus (NP) cells in vitro by binding to TGF-β1 and inhibiting the phosphorylation of Smads. However, the aetiology and mechanism of pathogenesis of LDD in vivo are unknown. To demonstrate the role of CILP in LDD in vivo, we generated transgenic mice that express CILP specifically in the intervertebral disc tissues and assessed whether CILP exacerbates disc degeneration. Degeneration of the intervertebral discs was assessed using magnetic resonance imaging (MRI) and histology. The level of phosphorylation of Smad2/3 in intervertebral discs was measured to determine whether overexpressed CILP suppressed TGF-beta signalling. Although the macroscopic skeletal phenotype of transgenic mice appeared normal, histological findings revealed significant degeneration of lumbar discs. MRI analysis of the lumbar intervertebral discs indicated a significantly lower signal intensity of the nucleus pulposus where CILP was overexpressed. Intervertebral disc degeneration was also observed. The number of phosphorylation of Smad2/3 immuno-positive cells in the NP significantly was decreased in CILP transgenic mice compared with normal mice. In summary, overexpression of CILP in the NP promotes disc degeneration, indicating that CILP plays a direct role in the pathogenesis of LDD.

Functional polymorphisms in asporin and CILP together with joint loading predispose to hand osteoarthritis

Background

Osteoarthritis (OA) is the most common degenerative joint disease afflicting people in the Western world and has a strong genetic influence. The aim of this study was to examine the association of two known functional polymorphisms in the TGF-β inhibiting genes, asporin (ASPN) and cartilage intermediate layer protein (CILP), with hand OA and potential gene-occupational hand loading interaction.

Results

Statistically significant interaction of the CILP rs2073711 T and ASPN D15 alleles with hand OA was observed (OR = 2.48, 95% CI 1.27–4.85, p = 0.008) in a Finnish hand OA cohort of 543 women (aged 45–63). When stratified by variation in working tasks, low variation of working tasks increased the risk further (OR = 3.00, 95% CI 1.35–6.66, p = 0.007). Based on the analysis of ASPN and CILP protein-coding regions, functional studies were performed with one observed variant, rs41278695 in the ASPN gene. Analyses showed that bone morphogenetic protein 2 (BMP2) mediated expression of aggrecan (Agc1) and type II collagen (Col2a1) was significantly suppressed (p = 0.011 and p = 0.023, respectively) in a murine chondrocytic cell line (ATDC5) with cells stably expressing ASPN rs41278695.

Conclusions

The carriage of either ASPN D15 or CILP rs2073711 TT is associated with increased risk of symmetrical hand OA, particularly in individuals with low variation in work tasks. ASPN rs41278695 SNP had an effect on Agc1 and Col2a1 gene expression when induced with BMP-2 suggesting an effect on the cartilage extracellular matrix composition.

CILP-2 expression in the intervertebral discs of patients with lumbar radiculopathy

BACKGROUND

Intervertebral disc (IVD) degeneration (IVDD) is one of the main causes of low back pain. One of the most important features of IVDD is the loss of extracellular matrix (ECM) with its structural components. Cartilage intermediate layer proteins (CILPs), minor glycoproteins residing in ECM, have been found to be increased in IVD as degeneration and aging progresses. The aim of the present study was to evaluate the expression of CILP-2 in the IVD of patients with lumbar radiculopathy.

METHODS

The IVD samples were collected from 25 patients during spinal surgery (interlaminectomy, herniated disc removal). The control IVD samples were obtained from nine patients who underwent lateral corpectomies in the thoracic region. CILP-2 expression was detected by immunohistochemistry. The patients were divided into two groups - aged under or over 50 years. A standardized clinical examination with assessment of radicular signs and deficits was performed. Subjective disability and pain were assessed using the visual analogue scale and Oswestry Disability Index (ODI). The pre-operative MRI was graded for the degree of IVD degeneration by Pfirrmann grading system. IVD samples obtained during operations were subjected to the standardized histopathological analysis applying modified Boos classification. The data were analysed by t-test, Mann-Whitney U-test, and Spearman correlation test.

RESULTS

Both histopathology scores and Pfirrmann grades did not differ between patients' groups. Also, no correlations were found between histopathology and Pfirrmann grades, neither were any differences seen when correlating both grades to ODI, back pain or leg pain scores. CILP-2 staining was noted in all studied samples, notably strong staining was seen around large cell clusters. However, no differences in CILP-2 staining were seen between the age groups of patients. No correlations were found between CILP-2 staining and Pfirrmann grades. Grading of CILP-2 immunostaining in nine control patient samples resulted in significantly lower values. The difference is statistically significant (P = 0.002) compared to CILP-2 staining scores of all 25 patients' samples.

CONCLUSION

In this study, we detected increased CILP-2 expression in the human IVD as compared to the control group patients. CILP-2 can be a possible IVDD marker; however, as knowledge about the role of CILP-2 is limited, further studies are required.