Cartilage oligomeric matrix protein in systemic sclerosis

Understanding Keloid Pathobiology From a Quasi-Neoplastic Perspective: Less of a Scar and More of a Chronic Inflammatory Disease With Cancer-Like Tendencies

Keloids are considered as benign fibroproliferative skin tumors growing beyond the site of the original dermal injury. Although traditionally viewed as a form of skin scarring, keloids display many cancer-like characteristics such as progressive uncontrolled growth, lack of spontaneous regression and extremely high rates of recurrence. Phenotypically, keloids are consistent with non-malignant dermal tumors that are due to the excessive overproduction of collagen which never metastasize. Within the remit of keloid pathobiology, there is increasing evidence for the various interplay of neoplastic-promoting and suppressing factors, which may explain its aggressive clinical behavior. Amongst the most compelling parallels between keloids and cancer are their shared cellular bioenergetics, epigenetic methylation profiles and epithelial-to-mesenchymal transition amongst other disease biological (genotypic and phenotypic) behaviors. This review explores the quasi-neoplastic or cancer-like properties of keloids and highlights areas for future study.

COMP serum levels: A new non-invasive biomarker of liver fibrosis in patients with chronic viral hepatitis

BACKGROUND & AIMS

Recently we have shown that cartilage oligomeric matrix protein (COMP), a fibrillar collagen assembly regulator, is strongly associated with cirrhosis and hepatocellular carcinoma progression. Therefore, we assessed whether serum COMP levels can be used as a non-invasive fibrosis marker in patients with chronic viral hepatitis (CVH) and compared this marker with standard methods for disease stage assessment [histology, transient elastography (TE), APRI, FIB-4].

METHODS

Sera from 116 CVH patients, 66 HBV [24 female; median age 53(22-76)] and 50 HCV [21 female; median age 48.5(25-69)] were investigated by COMP-ELISA. APRI and FIB-4 score was calculated in all along with TE. Liver biopsy was performed in 61. Patients were divided into two groups (F1/F2 and F3/F4) according to Metavir score.

RESULTS

55/116 (47%) CVH patients were classified in F3/F4-group according to TE [14.3(9.3-75)kPa]. APRI score was >1.5 in 21/116 and FIB-4>3.25 in 20/116. Liver histology revealed 24/61 (39%) patients with significant fibrosis (stage 3-4), while 12/61 (19.7%) had cirrhosis. COMP levels correlated with TE measurements (r=0.5; p<0.001) and APRI score (r=0.23; p<0.02). The diagnostic accuracy of COMP in detecting cirrhosis was as good as TE, APRI and FIB-4 index (AUC 0.884) with sensitivity and specificity of 83.3% and 83.7% (cut-off 11.5U/L).

CONCLUSIONS

COMP serum levels performed as well as TE, APRI and FIB4 score in detecting cirrhosis in CVH patients, suggesting COMP as a sensitive non-invasive, easy to perform biomarker of liver fibrosis. Further studies are needed in order to validate our findings in CVH patients.

Cartilage Oligomeric Matrix Protein Increases in Photodamaged Skin

Cartilage oligomeric matrix protein (COMP) is a structural component of cartilage. Recent studies have described COMP as a pathogenic factor that promotes collagen deposition in fibrotic skin disorders such as scleroderma and keloid skin. Although collagen, a major dermis component, is thought to decrease in photoaged skin, recent reports have demonstrated the presence of tightly packed collagen fibrils with a structural resemblance to fibrosis in the papillary dermis of photoaged skin. Here we examined how photoaging damage relates to COMP expression and localization in photoaged skin. In situ hybridization revealed an increase in COMP-mRNA-positive cells with the progress of photoaging in preauricular skin (sun-exposed skin). The signal intensity of immunostaining for COMP increased with photoaging in not only the papillary dermis but also the reticular dermis affected by advancing solar elastosis. Immunoelectron microscopy detected the colocalization of COMP with both elastotic materials and collagen fibrils in photoaged skin. Ultraviolet light A irradiation of human dermal fibroblasts induced COMP expression at both the mRNA and protein levels. Ultraviolet light A-induced COMP expression was inhibited by an anti-transforming growth factor-β antibody or SB431542, an activin receptor-like kinase 5 inhibitor. These results suggest that the transforming growth factor-β-mediated upregulation of COMP expression may contribute to the modulation of dermal extracellular matrix in the photoaging process.

Cartilage oligomeric matrix protein-induced complement activation in systemic sclerosis

Introduction

Complexes between cartilage oligomeric matrix protein (COMP) and the complement activation product C3b have been found in the circulation of patients with rheumatoid arthritis and systemic lupus erythematosus. In systemic sclerosis (SSc) COMP expression in the skin is upregulated both in lesional and non-lesional skin, which is also reflected in an increased amount of circulating COMP. We investigated the presence of COMP-C3b complexes in serum and skin biopsies of patients with SSc.

Methods

The presence of COMP and COMP-C3b complexes in the serum of 80 patients with limited cutaneous SSc (lcSSc, n = 40) and diffuse cutaneous SSc (dcSSc, n = 40) and 97 healthy controls was measured by ELISA and correlated to different clinical parameters. Samples were collected both at baseline and after three to five years to assess longitudinal changes in COMP-C3b complex levels. Furthermore, skin biopsies from seven patients with dcSSc and three healthy controls were analyzed for expression of COMP and deposition of C3b and IgG.

Results

Serum levels of COMP-C3b were found to be elevated in both dcSSc and lcSSc compared to healthy controls and decreased at the second measurement in patients on immunosuppressive therapy. No co-localization of COMP and C3b was found in the skin biopsies, indicating that the COMP-C3b complexes are formed upon release of COMP into the circulation.

Conclusion

COMP-C3b complexes are found in the serum of patients with SSc. The lack of co-localization between COMP and C3b in the skin suggests that COMP does not drive complement activation in the skin in SSc.

Cartilage oligomeric matrix protein in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive and life threatening disease with median survival of 2.5-3 years. The IPF lung is characterized by abnormal lung remodeling, epithelial cell hyperplasia, myofibroblast foci formation, and extracellular matrix deposition. Analysis of gene expression microarray data revealed that cartilage oligomeric matrix protein (COMP), a non-collagenous extracellular matrix protein is among the most significantly up-regulated genes (Fold change 13, p-value <0.05) in IPF lungs. This finding was confirmed at the mRNA level by nCounter® expression analysis in additional 115 IPF lungs and 154 control lungs as well as at the protein level by western blot analysis. Immunohistochemical analysis revealed that COMP was expressed in dense fibrotic regions of IPF lungs and co-localized with vimentin and around pSMAD3 expressing cells. Stimulation of normal human lung fibroblasts with TGF-β1 induced an increase in COMP mRNA and protein expression. Silencing COMP in normal human lung fibroblasts significantly inhibited cell proliferation and negatively impacted the effects of TGF-β1 on COL1A1 and PAI1. COMP protein concentration measured by ELISA assay was significantly increased in serum of IPF patients compared to controls. Analysis of serum COMP concentrations in 23 patients who had prospective blood draws revealed that COMP levels increased in a time dependent fashion and correlated with declines in force vital capacity (FVC). Taken together, our results should encourage more research into the potential use of COMP as a biomarker for disease activity and TGF-β1 activity in patients with IPF. Hence, studies that explore modalities that affect COMP expression, alleviate extracellular matrix rigidity and lung restriction in IPF and interfere with the amplification of TGF-β1 signaling should be persuaded.

Identification and characterization of cartilage oligomeric matrix protein as a novel pathogenic factor in keloids

To elucidate pathogenic molecules in keloids, microarray analysis was performed using RNAs extracted from keloid-derived fibroblasts and normal skin-derived fibroblasts from the same patient with a typical keloid. Among 11 up-regulated extracellular matrix genes, cartilage oligomeric matrix protein (COMP) was most prominently increased. Up-regulation of COMP mRNA and protein was confirmed in the keloid tissue by quantitative RT-PCR and Western blot. Using immunohistochemistry, we compared 15 keloids and 6 control normal tissues using a COMP-specific antibody and found that COMP stained positively in 10 keloids (66.7%), whereas no staining was observed in normal tissues, demonstrating the ectopic expression of COMP in keloids. Comparing keloids smaller or larger than 10 cm(2), the larger keloids were significantly more intensely stained with the COMP-specific antibody. Because COMP reportedly accelerates collagen type I fibril assembly, we examined whether extracellular type I collagen deposition is altered by silencing COMP mRNA by small interfering RNA (siRNA). Immunocytochemistry showed at 96 hours after transfection with COMP siRNA that the extracellular deposition of type I collagen was decreased compared to that observed with control siRNA. Further, COMP knockdown decreased amount collagens type I to V in the medium and on the cell surfaces. Our data suggest that COMP facilitates keloid formation by accelerating collagen deposition, thus providing a new therapeutic target.