Human cartilage chitinase 3-like protein 2: cloning, expression, and production of polyclonal and monoclonal antibodies for osteoarthritis detection and identification of potential binding partners

[Expression profile of intervertebral disc degeneration-specific genes: a transcriptome sequencing-based analysis]

OBJECTIVE

To identify new therapeutic targets for intervertebral disc degeneration (IDD) by analyzing gene variations in IDD.

OBJECTIVE

We analyzed surgical samples of intervertebral disc from 4 patients with IDD and 3 patients with non-IDD using RNA sequencing (RNA-seq) technology to identify significant differentially expressed genes (DEGs) in IDD. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases were utilized for gene enrichment studies to acquire the key genes and signal pathways during IDD progression. The differential expressions of the identified genes in IDD were validated in clinical samples with qRT-PCR.

OBJECTIVE

The transcriptome profile revealed 512 significant DEGs, which were enriched in terms of keratinization, extracellular matrix (ECM) components, growth factor binding, and inflammatory chemotaxis in GO analysis. The top 10 terms of KEGG enrichment included amoebiasis, viral protein interaction with cytokine and cytokine receptor, ECM-receptor interaction, IL-17 signaling pathway, cytokine-cytokine receptor interaction, TNF signaling pathway, AGE-RAGE signaling pathway in diabetic complications, PI3K-Akt signaling pathway, chemokine signaling pathway and estrogen signaling pathway. Thirteen DEGs selected as the targets for qRT-PCR validation showed significant differential expressions in IDD (P < 0.001), and their expression trends were all consistent with the results of RNA-seq. Among these genes, 10 genes showed significant intergroup fold change (Log2FoldChange>1).

OBJECTIVE

ECM, growth factors, collagen components, inflammatory chemokines and such signal pathways as TNF-α and PI3K-Akt all have important contributions to IDD progression and may thus serve as new therapeutic targets for treatment of IDD.

Identification of Novel Targets of Knee Osteoarthritis Shared by Cartilage and Synovial Tissue

Arthritis is the leading cause of disability among adults, while osteoarthritis (OA) is the most common form of arthritis that results in cartilage loss. However, accumulating evidence suggests that the protective hyaline cartilage should not be the sole focus of OA treatment. Particularly, synovium also plays essential roles in OA’s initiation and progression and warrants serious consideration when battling against OA. Thus, biomarkers with similar OA-responsive expressions in cartilage and synovium should be the potential targets for OA treatment. On the other hand, molecules with a distinguished response during OA in cartilage and synovium should be ruled out as OA therapeutic(s) to avoid controversial effects in different tissues. Here, to pave the path for developing a new generation of OA therapeutics, two published transcriptome datasets of knee articular cartilage and synovium were analyzed in-depth. Genes with statistically significantly different expression in OA and healthy cartilage were compared with those in the synovium. Thirty-five genes with similar OA-responsive expression in both tissues were identified while recognizing three genes with opposite OA-responsive alteration trends in cartilage and synovium. These genes were clustered based on the currently available knowledge, and the potential impacts of these clusters in OA were explored.

A microfluidic capacitive immunosensor system for human cartilage chitinase-3-like protein 2 (hYKL-39) quantification as an osteoarthritis marker in synovial joint fluid

Flow-based electrochemical osteoarthritis biomarker quantification in joint synovial fluid has been established as first alternative to optical ELISA assays.

Structural and thermodynamic insights into chitooligosaccharide binding to human cartilage chitinase 3-like protein 2 (CHI3L2 or YKL-39)

Four crystal structures of human YKL-39 were solved in the absence and presence of chitooligosaccharides. The structure of YKL-39 comprises a major (β/α)8 triose-phosphate isomerase barrel domain and a small α + β insertion domain. Structural analysis demonstrates that YKL-39 interacts with chitooligosaccharides through hydrogen bonds and hydrophobic interactions. The binding of chitin fragments induces local conformational changes that facilitate tight binding. Compared with other GH-18 members, YKL-39 has the least extended chitin-binding cleft, containing five subsites for sugars, namely (-3)(-2)(-1)(+1)(+2), with Trp-360 playing a prominent role in the sugar-protein interactions at the center of the chitin-binding cleft. Evaluation of binding affinities obtained from isothermal titration calorimetry and intrinsic fluorescence spectroscopy suggests that YKL-39 binds to chitooligosaccharides with Kd values in the micromolar concentration range and that the binding energies increase with the chain length. There were no significant differences between the Kd values of chitopentaose and chitohexaose, supporting the structural evidence for the five binding subsite topology. Thermodynamic analysis indicates that binding of chitooligosaccharide to YKL-39 is mainly driven by enthalpy.