Development of a novel immunoassay for the measurement of type II collagen neoepitope generated by collagenase cleavage

From biochemical markers to molecular endotypes of osteoarthritis: a review on validated biomarkers

INTRODUCTION

Osteoarthritis (OA) affects over 500 million people worldwide. OA patients are symptomatically treated, and current therapies exhibit marginal efficacy and frequently carry safety-risks associated with chronic use. No disease-modifying therapies have been approved to date leaving surgical joint replacement as a last resort. To enable effective patient care and successful drug development there is an urgent need to uncover the pathobiological drivers of OA and how these translate into disease endotypes. Endotypes provide a more precise and mechanistic definition of disease subgroups than observable phenotypes, and a panel of tissue- and pathology-specific biochemical markers may uncover treatable endotypes of OA.

AREAS COVERED

We have searched PubMed for full-text articles written in English to provide an in-depth narrative review of a panel of validated biochemical markers utilized for endotyping of OA and their association to key OA pathologies.

EXPERT OPINION

As utilized in IMI-APPROACH and validated in OAI-FNIH, a panel of biochemical markers may uncover disease subgroups and facilitate the enrichment of treatable molecular endotypes for recruitment in therapeutic clinical trials. Understanding the link between biochemical markers and patient-reported outcomes and treatable endotypes that may respond to given therapies will pave the way for new drug development in OA.

Pd@Pt nanoparticle-linked immunosorbent assay for quantification of Collagen type II

The evaluation of specific protein content in engineered tissues provides a gateway for developing regenerative medicine treatments. Since collagen type II, the major component of articular cartilage, is critical for the blossoming field of articular cartilage tissue engineering, the interest in this protein is growing rapidly. Accordingly, the need for quantification of collagen type II is increasing as well. In this study, we provide recent results for a new quantifying nanoparticle sandwich immunoassay technique for collagen type II. Since mesoporous palladium@platinum (Pd@Pt) nanoparticles have peroxidase-like catalytic activities, these nanoparticles were utilized in an enzyme-linked immunosorbent assay (ELISA)-like format to circumvent the need for traditional enzymes. These nanoparticles were easily conjugated with anti-collagen type II antibodies by the natural affinity interaction and used to develop a direct sandwich ELISA-like format for nanoparticle-linked immunosorbent assays. Using this method, we obtained a limit of detection of 1 ng mL-1, a limit of quantification of 9 ng mL-1. and a broad linear range between 1 ng mL-1 and 50 μg mL-1 for collagen type II with an average relative standard deviation of 5.5%, useable over a pH range of 7 - 9 at least. The assay was successfully applied to quantify collagen type II in cartilage tissues and compared with the results of commercial ELISAs and gene expression by reverse transcription-quantitative polymerase chain reaction. This method provides a thermally stable and cost-efficient alternative to traditional ELISAs. It also extends the application of nanoparticle-linked immunosorbent assays, thereby providing the potential to quantify other proteins and apply the technology in the medical, environmental, and biotechnology industry fields.

Soluble biological markers in osteoarthritis

In recent years, markers research has focused on the structural components of cartilage matrix. Specifically, a second generation of degradation markers has been developed against type II collagen neoepitopes generated by specific enzymes. A particular effort has been made to measure the degradation of minor collagens III and X of the cartilage matrix. However, because clinical data, including longitudinal controlled studies, are very scarce, it remains unclear whether they will be useful as an alternative to or in combination with current more established collagen biological markers to assess patients with osteoarthritis (OA). In addition, new approaches using high-throughput technologies allowed to detect new types of markers and improve the knowledge about the metabolic changes linked to OA. The relative advances coming from phenotype research are a first attempt to classify the heterogeneity of OA, and several markers could improve the phenotype characterization. These phenotypes could improve the selection of patients in clinical trials limiting the size of the studies by selecting patients with OA characteristics corresponding to the metabolic pathway targeted by the molecules evaluated. In addition, the inclusion of rapid progressors only in clinical trials would facilitate the demonstration of efficacy of the investigative drug to reduce joint degradation. The combination of selective biochemical markers appears as a promising and cost-effective approach to fulfill this unmet clinical need. Among the various potential roles of biomarkers in OA, their ability to monitor drug efficacy is probably one of the most important, in association with clinical and imaging parameters. Biochemical markers have the unique property to detect changes in joint tissue metabolism within a few weeks.

KLF15 is an essential negative regulatory factor for the cardiac remodeling response to pressure overload

OBJECTIVE

To investigate the mechanism of Krüppel-like factor 15 (KLF15) in cardiac remodeling and interstitial fibrosis.

METHODS

A rat model was established by in vivo aortic coarctation followed by a period of pressure unloading and used to measure heart function, myocardial pathological changes, and KLF15, transforming growth factor-β (TGF-β), connective tissue growth factor (CTGF), and myocardin-related transcription factor A (MRTF-A) expression levels. In addition, cardiac fibroblasts were cultured in vitro and treated with KLF15-shRNA or KLF15 recombinant adenovirus to establish a TGF-β-mediated cardiac fibroblast hypertrophy model and analyze cell morphology, collagen secretion, and changes in the expression levels of 4 cytokines.

RESULTS

In vivo pressure overload impaired cardiac function and resulted in myocardial hypertrophy and fibrosis. These changes were accompanied by the downregulation of KLF15 mRNA levels and increased expression of the other factors. The response to unloading was the opposite. In in vitro cell experiments, by specifically targeting the KLF15 gene, changes in the expression levels of the 4 cytokines and the amounts of collagen I and III were observed.

CONCLUSIONS

In myocardial remodeling processes induced by mechanical or metabolic factors, KLF15 regulates TGF-β, CTGF, and MRTF-A expression and can ameliorate or even reverse myocardial fibrosis and improve cardiac function.

Cartilage turnover reflected by metabolic processing of type II collagen: a novel marker of anabolic function in chondrocytes

The aim of this study was to enable measurement of cartilage formation by a novel biomarker of type II collagen formation. The competitive enzyme-linked immunosorbent assay (ELISA) Pro-C2 was developed and characterized for assessment of the beta splice variant of type II procollagen (PIIBNP). This is expected to originate primarily from remodeling of hyaline cartilage. A mouse monoclonal antibody (Mab) was raised in mouse, targeting specifically PIIBNP (QDVRQPG) and used in development of the assay. The specificity, sensitivity, 4-parameter fit and stability of the assay were tested. Levels of PIIBNP were quantified in human serum (0.6–2.2 nM), human amniotic fluid (163–188 nM) and sera from different animal species, e.g., fetal bovine serum (851–901 nM) with general good linearity (100% (SD 7.6) recovery) and good intra- and inter-assay variation (CV% < 10). Dose (0.1 to 100 ng/mL) and time (7, 14 and 21 days) dependent release of PIIBNP were evaluated in the conditioned medium from bovine cartilage explants (BEX) and human cartilage explants (HEX) upon stimulation with insulin-like growth factor (IGF-1), transforming growth factor (TGF)-β1 and fibroblastic growth factor-2 (FGF-2). TGF-β1 and IGF-1 in concentrations of 10–100 ng/mL significantly (p < 0.05) induced release of PIIBNP in BEX compared to conditions without treatment (WO). In HEX, IGF-1 100 ng/mL was able to induce a significant increase of PIIBNP after one week compared to WO. FGF-2 did not induce a PIIBNP release in our models. To our knowledge this is the first assay, which is able to specifically evaluate PIIBNP excretion. The Pro-C2 assay seems to provide a promising and novel marker of type II collagen formation.

Current and emerging therapeutic strategies for preventing inflammation and aggrecanase-mediated cartilage destruction in arthritis

Arthritis is a multifactorial disease for which current therapeutic intervention with high efficacy remains challenging. Arthritis predominately affects articular joints, and cartilage deterioration and inflammation are key characteristics. Current therapeutics targeting inflammatory responses often cause severe side effects in patients because of the systemic inhibition of cytokines or other global immunosuppressive activities. Furthermore, a lack of primary response or failure to sustain a response to treatment through acquired drug resistance is an ongoing concern. Nevertheless, treatments such as disease-modifying anti-rheumatic drugs, biological agents, and corticosteroids have revealed promising outcomes by decreasing pain and inflammation in patients and in some cases reducing radiographic progression of the disease. Emerging and anecdotal therapeutics with anti-inflammatory activity, alongside specific inhibitors of the A Disintegrin-like And Metalloproteinase domain with Thrombospondin-1 repeats (ADAMTS) cartilage-degrading aggrecanases, provide promising additions to current arthritis treatment strategies. Thus, it is paramount that treatment strategies be optimized to increase efficacy, reduce debilitating side effects, and improve the quality of life of patients with arthritis. Here, we review the current strategies that attempt to slow or halt the progression of osteoarthritis and rheumatoid arthritis, providing an up-to-date summary of pharmaceutical treatment strategies and side effects. Importantly, we highlight their potential to indirectly regulate ADAMTS aggrecanase activity through their targeting of inflammatory mediators, thus providing insight into a mechanism by which they might inhibit cartilage destruction to slow or halt radiographic progression of the disease. We also contrast these with anecdotal or experimental administration of statins that could equally regulate ADAMTS aggrecanase activity and are available to arthritis sufferers worldwide. Finally, we review the current literature regarding the development of synthetic inhibitors directed toward the aggrecanases ADAMTS4 and ADAMTS5, a strategy that might directly inhibit cartilage destruction and restore joint function in both rheumatoid arthritis and osteoarthritis.

CIINE Reflects Collagenase-Specific CII Breakdown in Cartilage Explant and Whole Body of Canine

To evaluate collagenase inhibitors for the treatment of osteoarthritis and to correlate them with clinical pathology, canine cartilage explant and anterior cruciate ligament transection (ACLT) models were examined by quantifying the CII neoepitope (CIINE). This peptide is a putative marker for collagenase-specific type II collagen (CII) degradation, which is a critical step in osteoarthritis pathology.

The concentration of CIINE in supernatants of canine cartilage explants showed increase upon IL-1β—stimulation and collagenase inhibitors suppressed this elevation of CIINE. In the canine ACLT model, levels of CIINE in urine (uCIINE) increased as lesions of knee joint cartilage developed and decreased in response to collagenase inhibitors.

Our results suggest that CIINE reflects collagenase-specific CII degradation in canine explants and whole bodies. It is anticipated that these data will establish a tool for clarifying and bridging the efficacy and mechanism of collagenase inhibitors at the preclinical stage of drug discovery.