Targeted proteomics of hip articular cartilage in OA and fracture patients

Osteoarthritis (OA) is a common chronic disease, causing joint pain and reduced physical function. OA progresses slowly over a period of several years; to avoid an exacerbation of symptoms, it is critical to able to diagnose the disease as early as possible. The identification of disease-specific biomarkers may enable such an early diagnosis. The aim of this study was to investigate potential biomarkers of cartilage metabolism in OA using a targeted multiplex approach by single reaction monitoring. Intact looking cartilage of femoral heads from patients with OA (n = 9) or femoral neck fractures (n = 12) was examined. Variations and relative quantifications of 35 selected extracellular matrix (ECM) proteins were analyzed using nano-LC coupled to tandem mass spectrometry. Our study showed statistically significantly increased levels of asporin (ASPN), mimecan (MIME), matrilin-3 (MATN3), cartilage intermediate layer protein 2 (CILP-2), collagen VI, collagen II, and collagen III N-propeptide in OA cartilage compared with non-OA cartilage. The other proteins in the protein panel did not appear to be different between the two groups. In conclusion, we identified a number of cartilage matrix proteins which may represent early molecular changes in the OA process and may have potential to predict the development of OA. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.

Evidence for enhanced collagen type III deposition focally in the territorial matrix of osteoarthritic hip articular cartilage

OBJECTIVE

To determine if type III collagen is concentrated in the chymotrypsin-extractable collagen pool from osteoarthritic articular cartilage to assess its potential as a biomarker of Osteoarthritis (OA) pathogenic mechanisms.

METHODS

Full thickness articular cartilage from grossly normal surfaces was analyzed from femoral heads, obtained at hip replacement surgery, from OA (n = 10) and fracture (n = 10) patients. Collagen, extracted by α-chymotrypsin, was characterized by SDS-PAGE/Western blot analysis, ELISA and immunohistochemistry using monoclonal antibodies specific to collagens types II and III.

RESULTS

α-Chymotrypsin extracted more collagen from OA than control cartilage. The extractable pool included collagen types II and III from both OA and control hips. Importantly, OA cartilage contained 6-fold more collagen type III than control cartilage, based on ELISA. The estimated total tissue ratio of collagen III/II was in the 1-10% range for individual OA cartilage samples, based on pepsin-solubilized collagen using SDS-PAGE densitometry. Collagen type III N-propeptide trimers were the main molecular fragments seen on Western blot analysis of OA and control extracts. The chymotrypsin-extracted type II collagen gave primarily full-length α1(II) chains and chain fragments of α1(II) on Western blot analysis from both OA and control tissues. Immunohistochemistry showed that type III collagen was more concentrated in the upper half of OA cartilage and in the territorial matrix around individual chondrocytes and chondrocyte clusters.

CONCLUSIONS

The findings confirm that collagen type III deposition occurs in adult articular cartilage but significantly more pronounced in osteoarthritic joints, presenting a potential marker of matrix repair or pathobiology.

Polymorphisms of GSTT1, GSTM1, and EPHX genotypes in patients with cryptogenic polyneuropathy: a case-control study

The aim of this study was to analyze whether polymorphisms for the null alleles of Glutathione S-Transferase Mu-1 (GSTM1), Glutathione S-Transferase Theta-1 (GSTT1), and a low-activity genetic variation of epoxide hydrolase exon three (EPHX*3) affect the risk of developing polyneuropathy. The enzymes of these genes are important in the metabolism of toxic compounds. Seventy-nine patients with cryptogenic polyneuropathy (equivalent to chronic idiopathic axonal neuropathy) and 398 controls were tested for the genetic polymorphism. Medical records were reviewed to collect data regarding clinical findings at diagnosis, and exposure data was collected via questionnaires. The odds ratios (ORs) for the null forms of GSTM1 and GSTT1 and the normal activity YY form of EPHX*3 were close to one except GSTT1, which reached 1.86. The highest risk of polyneuropathy was found in smokers with GSTT1 null, who had a 3.7 times increased risk. Interactions between genes were analyzed and confirmed the increased OR for GSTT1, which was strongest if the patients had the low-activity HH form of EPHX*3 (OR 2.37). Our hypothesis is that the GSTT1 null polymorphism may be related to an impaired metabolism of toxic substances that could lead to nerve damage in the peripheral nervous system.