P21 Novel ex-vivo model of septic arthritis identifies role of neutrophils in joint destruction and identifies a potential biomarker for diagnosis

Abstract Background Septic arthritis (SA) caused by bacterial species, such as Staphylococcus aureus, has high morbidity and mortality. Currently diagnosis is often prolonged and unreliable, with no suitable near-patient biomarkers available. To generate more reliable biomarkers and to understand pathogenesis we sought to develop a novel ex vivo system to explore the effect of pathogenic Staph. aureus strains in promoting cartilage degradation. Methods Human cartilage explants were obtained from femoral heads being surgically removed following trauma. Explants were infected for 48h with 106 cfu bacteria from two Staph. aureus SA-derived patient isolates (28g & 36v strains). In the final 24h of bacterial infection, neutrophils purified from healthy donor blood were added to explant cultures at 3 x 106 cells/well. Chondrocyte viability was assessed using CellTracker green CMFDA and propidium iodide. Images were captured using confocal microscopy (LSM880) and cells counted using Imaris software. Structural damage was measured by glycosaminoglycan (GAG) and a neo-epitope of MMP-mediated degradation of type II collagen (C2M) release. Statistical analysis was performed using GraphPad Prism software. Results When cartilage explants were co-cultured with bacteria +/- neutrophils, cell death was significantly increased compared to the negative control or addition of neutrophils alone, (Friedman multiple comparisons test, N = 3, negative control vs. bacteria - neutrophils p <0.05, negative control vs. bacteria + neutrophils p < 0.01). Cartilage breakdown, estimated via GAG release, was induced by Staph. aureus alone, whereas it was significantly enhanced upon neutrophil addition in the final 24h of co-culture (Friedman multiple comparisons test, N = 8, neutrophil vs. neutrophil + bacterial strain 36v p <0.0001, neutrophil vs. neutrophil + bacterial strain 28g p <0.0005). Therefore, it is the combined effect with neutrophils that results in significant cartilage destruction. Although cartilage is damaged with the bacterial infection, shown by GAG release, C2M was only released when the bacteria is co-cultured with neutrophils (Friedman multiple comparisons test, N = 8, 36v vs. 36v + neutrophil p <0.0001, 28g vs. 28g + neutrophil p <0.005). This indicates that C2M is a biomarker that could potentially be used to diagnose septic arthritis as neutrophils infiltrate the joint in response to a bacterial infection. Conclusion A co-culture model of septic arthritis has been developed which allows precise examination of the contribution of the host neutrophil response to cartilage damage. We used this to identify a collagen breakdown product as a biomarker of host response to infected cartilage. This novel model will be a valuable tool in understanding the pathology of joint infection and can be used for the identification of future diagnostic biomarkers. Disclosures K.E. McCall None. C. Atherton None. C. Thudium None. C. Goodyear Grants/research support; C.G. has received funding for research from Celgene, AstraZeneca, MedAnnex, UCB & Jannsen. T. Evans None. N. Millar Grants/research support; Novartis. I. McInnes Consultancies; I.M. has received consultancies fees from BMS, Abbvie, Lilly, GSK & Pfizer. Grants/research support; I.M received research funding from Calgene, Janssen, Novartis, Boehringer Ingelheim & BMS.

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The Hexosamine Biosynthetic Pathway as a Therapeutic Target after Cartilage Trauma: Modification of Chondrocyte Survival and Metabolism by Glucosamine Derivatives and PUGNAc in an Ex Vivo Model

International Journal of Molecular Sciences ◽

10.3390/ijms22147247 ◽

2021 ◽

Vol 22 (14) ◽

pp. 7247

Author(s):

Jana Riegger ◽

Julia Baumert ◽

Frank Zaucke ◽

Rolf E. Brenner

Keyword(s):

Biosynthetic Pathway ◽

Ex Vivo ◽

Type Ii Collagen ◽

Cartilage Explants ◽

Uridine Diphosphate ◽

Cell Protection ◽

Ex Vivo Model ◽

Human Cartilage ◽

Hexosamine Biosynthetic Pathway ◽

Cellular Processes

The hexosamine biosynthetic pathway (HBP) is essential for the production of uridine diphosphate N-acetylglucosamine (UDP-GlcNAc), the building block of glycosaminoglycans, thus playing a crucial role in cartilage anabolism. Although O-GlcNAcylation represents a protective regulatory mechanism in cellular processes, it has been associated with degenerative diseases, including osteoarthritis (OA). The present study focuses on HBP-related processes as potential therapeutic targets after cartilage trauma. Human cartilage explants were traumatized and treated with GlcNAc or glucosamine sulfate (GS); PUGNAc, an inhibitor of O-GlcNAcase; or azaserine (AZA), an inhibitor of GFAT-1. After 7 days, cell viability and gene expression analysis of anabolic and catabolic markers, as well as HBP-related enzymes, were performed. Moreover, expression of catabolic enzymes and type II collagen (COL2) biosynthesis were determined. Proteoglycan content was assessed after 14 days. Cartilage trauma led to a dysbalanced expression of different HBP-related enzymes, comparable to the situation in highly degenerated tissue. While GlcNAc and PUGNAc resulted in significant cell protection after trauma, only PUGNAc increased COL2 biosynthesis. Moreover, PUGNAc and both glucosamine derivatives had anti-catabolic effects. In contrast, AZA increased catabolic processes. Overall, “fueling” the HBP by means of glucosamine derivatives or inhibition of deglycosylation turned out as cells and chondroprotectives after cartilage trauma.

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Raman Needle Arthroscopy for In Vivo Molecular Assessment of Cartilage

10.1101/2021.06.15.448529 ◽

2021 ◽

Author(s):

Kimberly Kroupa ◽

Man I Wu ◽

Juncheng Zhang ◽

Magnus Jensen ◽

Wei Wong ◽

...

Keyword(s):

Ex Vivo ◽

Low Cost ◽

Femoral Condyle ◽

Cartilage Explants ◽

Anatomical Site ◽

Superficial Zone ◽

Human Cartilage ◽

Polarized Raman ◽

Bovine Cartilage

The development of treatments for osteoarthritis (OA) is burdened by the lack of standardized biomarkers of cartilage health that can be applied in clinical trials. We present a novel arthroscopic Raman probe that can optically biopsy cartilage and quantify key ECM biomarkers for determining cartilage composition, structure, and material properties in health and disease. Technological and analytical innovations to optimize Raman analysis include: 1) multivariate decomposition of cartilage Raman spectra into ECM-constituent-specific biomarkers (glycosaminoglycan [GAG], collagen [COL], water [H2O] scores), and 2) multiplexed polarized Raman spectroscopy to quantify superficial zone collagen anisotropy via a PLS-DA-derived Raman collagen alignment factor (RCAF). Raman measurements were performed on a series of ex vivo cartilage models: 1) chemically GAG-depleted bovine cartilage explants (n=40), 2) mechanically abraded bovine cartilage explants (n=30), 3) aging human cartilage explants (n=14), and 4) anatomical-site-varied ovine osteochondral explants (n=6). Derived Raman GAG score biomarkers predicted 95%, 66%, and 96% of the variation in GAG content of GAG-depleted bovine explants, human explants, and ovine explants, respectively (p<0.001). RCAF values were significantly different for explants with abrasion-induced superficial zone collagen loss (p<0.001). The multivariate linear regression of Raman-derived ECM biomarkers (GAG and H2O scores) predicted 94% of the variation in elastic modulus of ovine explants (p<0.001). Finally, we demonstrated the first in vivo Raman arthroscopy assessment of an ovine femoral condyle through intraarticular entry into the synovial capsule. This work advances Raman arthroscopy towards a transformative low cost, minimally invasive diagnostic platform for objective monitoring of treatment outcomes from emerging OA therapies.

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Resveratrol and Curcumin Attenuate Ex Vivo Sugar-Induced Cartilage Glycation, Stiffening, Senescence, and Degeneration

Cartilage ◽

10.1177/1947603520988768 ◽

2021 ◽

pp. 194760352098876

Author(s):

Shikhar Mehta ◽

Cameron C. Young ◽

Matthew R. Warren ◽

Sumayyah Akhtar ◽

Sandra J. Shefelbine ◽

...

Keyword(s):

Ex Vivo ◽

Binding Energies ◽

Cartilage Explants ◽

Tissue Stiffness ◽

Human Cartilage ◽

Nonenzymatic Glycation ◽

Docking Analysis ◽

Cartilage Explant ◽

Age Related ◽

Collagen Ii

Objective Advanced glycation end-product (AGE) accumulation is implicated in osteoarthritis (OA) pathogenesis in aging and diabetic populations. Here, we develop a representative nonenzymatic glycation-induced OA cartilage explant culture model and investigate the effectiveness of resveratrol, curcumin, and eugenol in inhibiting AGEs and the structural and biological hallmarks of cartilage degeneration. Design Bovine cartilage explants were treated with AGE–bovine serum albumin, threose, and ribose to determine the optimal conditions that induce physiological levels of AGEs while maintaining chondrocyte viability. AGE crosslinks, tissue stiffness, cell viability, metabolism and senescence, nitrite release and loss of glycosaminoglycans were assessed. Explants were cotreated with resveratrol, curcumin, or eugenol to evaluate their anti-AGE properties. Blind docking analysis was conducted to estimate binding energies of drugs with collagen II. Results Treatment with 100 mM ribose significantly increased AGE crosslink formation and tissue stiffness, resulting in reduced chondrocyte metabolism and enhanced senescence. Blind docking analysis revealed stronger binding energies of both resveratrol and curcumin than ribose, with glycation sites along a human collagen II fragment, indicating their increased likelihood of competitively inhibiting ribose activity. Resveratrol and curcumin, but not eugenol, successfully inhibited AGE crosslink formation and its associated downstream biological response. Conclusions We establish a cartilage explant model of OA that recapitulates several aspects of aged human cartilage. We find that resveratrol and curcumin are effective anti-AGE therapeutics with the potential to decelerate age-related and diabetes-induced OA. This in vitro nonenzymatic glycation-induced model provides a tool for screening OA drugs, to simultaneously evaluate AGE-induced biological and mechanical changes.

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Amentadione from the Alga Cystoseira usneoides as a Novel Osteoarthritis Protective Agent in an Ex Vivo Co-Culture OA Model

Marine Drugs ◽

10.3390/md18120624 ◽

2020 ◽

Vol 18 (12) ◽

pp. 624 ◽

Cited By ~ 1

Author(s):

Nuna Araújo ◽

Carla S. B. Viegas ◽

Eva Zubía ◽

Joana Magalhães ◽

Acácio Ramos ◽

...

Keyword(s):

Gene Expression ◽

Protective Factor ◽

Inflammatory Responses ◽

Therapeutic Potential ◽

Ex Vivo ◽

Cartilage Explants ◽

Protective Agent ◽

Human Cartilage ◽

Effective Prevention ◽

Anti Inflammatory

Osteoarthritis (OA) remains a prevalent chronic disease without effective prevention and treatment. Amentadione (YP), a meroditerpenoid purified from the alga Cystoseira usneoides, has demonstrated anti-inflammatory activity. Here, we investigated the YP anti-osteoarthritic potential, by using a novel OA preclinical drug development pipeline designed to evaluate the anti-inflammatory and anti-mineralizing activities of potential OA-protective compounds. The workflow was based on in vitro primary cell cultures followed by human cartilage explants assays and a new OA co-culture model, combining cartilage explants with synoviocytes under interleukin-1β (IL-1β) or hydroxyapatite (HAP) stimulation. A combination of gene expression analysis and measurement of inflammatory mediators showed that the proposed model mimicked early disease stages, while YP counteracted inflammatory responses by downregulation of COX-2 and IL-6, improved cartilage homeostasis by downregulation of MMP3 and the chondrocytes hypertrophic differentiation factors Col10 and Runx2. Importantly, YP downregulated NF-κB gene expression and decreased phosphorylated IkBα/total IkBα ratio in chondrocytes. These results indicate the co-culture as a relevant pre-clinical OA model, and strongly suggest YP as a cartilage protective factor by inhibiting inflammatory, mineralizing, catabolic and differentiation processes during OA development, through inhibition of NF-κB signaling pathways, with high therapeutic potential.

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Antibacterial Power of Sodium Hypochlorite Combined with Surfactants and Acetic Acid

Brazilian Dental Journal ◽

10.1590/0103-6440201300075 ◽

2014 ◽

Vol 25 (4) ◽

pp. 289-294 ◽

Cited By ~ 3

Author(s):

Luciano Giardino ◽

Carlos Estrela ◽

Zahed Mohammadi ◽

Flavio Palazzi

Keyword(s):

Acetic Acid ◽

Ex Vivo ◽

Multiple Comparisons ◽

Positive Control ◽

Negative Control ◽

Parametric Methods ◽

Colony Forming Units ◽

Root Dentin ◽

Ex Vivo Study ◽

One Way Anova

The aim of this ex vivo study was to compare the antibacterial power of 1% NaOCl with 1% acetic acid, 5.25% NaOCl and two commercially available NaOCl modified with surfactants in bovine root dentin. A total of 120 dentin tubes prepared from intact bovine incisors were infected for 21 days with Enterococcus faecalis and randomly divided into six groups as follows: 5.25%NaOCl; Hypoclean; Chlor-Xtra; 1% NaOCl with 1% acetic acid; infected dentin tubes (positive control); and sterile dentin tubes (negative control). At experimental times of 0, 7, 14, 21 and 28 days, dentin chips were collected using sequential round burs with increasing diameters in separate test tubes containing 3 mL of freshly prepared BHI. Statistical analysis were performed using parametric methods (one-way ANOVA, and Bonferroni's multiple comparisons test, α=0.01). After culturing, the number of colony-forming units (CFU) was counted. All the NaOCl solutions showed small number of CFU over 28 days. ChlorXtra and Hypoclean had the smallest number of CFU at all times with greater antimicrobial efficacy than 5.25% NaOCl and 1% NaOCl solution with 1% acetic acid.

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Anti-Inflammatory Effects of Novel Standardized Platelet Rich Plasma Releasates on Knee Osteoarthritic Chondrocytes and Cartilage in vitro

Current Pharmaceutical Biotechnology ◽

10.2174/1389201020666190619111118 ◽

2019 ◽

Vol 20 (11) ◽

pp. 920-933 ◽

Cited By ~ 3

Author(s):

Lucía Gato-Calvo ◽

Tamara Hermida-Gómez ◽

Cristina R. Romero ◽

Elena F. Burguera ◽

Francisco J. Blanco

Keyword(s):

Gene Expression ◽

Ex Vivo ◽

Platelet Rich Plasma ◽

Cartilage Explants ◽

Ex Vivo Model ◽

Chondrocyte Viability ◽

Platelet Concentration ◽

The Absolute ◽

Anti Inflammatory

Background: Platelet Rich Plasma (PRP) has recently emerged as a potential treatment for osteoarthritis (OA), but composition heterogeneity hampers comparison among studies, with the result that definite conclusions on its efficacy have not been reached. Objective: 1) To develop a novel methodology to prepare a series of standardized PRP releasates (PRP-Rs) with known absolute platelet concentrations, and 2) To evaluate the influence of this standardization parameter on the anti-inflammatory properties of these PRP-Rs in an in vitro and an ex vivo model of OA. Methods: A series of PRPs was prepared using the absolute platelet concentration as the standardization parameter. Doses of platelets ranged from 0% (platelet poor plasma, PPP) to 1.5·105 platelets/µl. PRPs were then activated with CaCl2 to obtain releasates (PRP-R). Chondrocytes were stimulated with 10% of each PRP-R in serum-free culture medium for 72 h to assess proliferation and viability. Cells were co-stimulated with interleukin (IL)-1β (5 ng/ml) and 10% of each PRP-R for 48 h to determine the effects on gene expression, secretion and intra-cellular content of common markers associated with inflammation, catabolism and oxidative stress in OA. OA cartilage explants were co-stimulated with IL-1β (5 ng/ml) and 10% of either PRP-R with 0.75·105 platelets/µl or PRP-R with 1.5·105 platelets/µl for 21 days to assess matrix inflammatory degradation. Results: Chondrocyte viability was not affected, and proliferation was dose-dependently increased. The gene expression of all pro-inflammatory mediators was significantly and dose-independently reduced, except for that of IL-1β and IL-8. Immunoblotting corroborated this effect for inducible NO synthase (NOS2). Secreted matrix metalloproteinase-13 (MMP-13) was reduced to almost basal levels by the PRP-R from PPP. Increasing platelet dosage led to progressive loss to this anti-catabolic ability. Safranin O and toluidine blue stains supported the beneficial effect of low platelet dosage on cartilage matrix preservation. Conclusion: We have developed a methodology to prepare PRP releasates using the absolute platelet concentration as the standardization parameter. Using this approach, the composition of the resulting PRP derived product is independent of the donor initial basal platelet count, thereby allowing the evaluation of its effects objectively and reproducibly. In our OA models, PRP-Rs showed antiinflammatory, anti-oxidant and anti-catabolic properties. Platelet enrichment could favor chondrocyte proliferation but is not necessary for the above effects and could even be counter-productive.

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Optical Biomarkers for the Diagnosis of Osteoarthritis through Raman Spectroscopy: Radiological and Biochemical Validation Using Ex Vivo Human Cartilage Samples

Diagnostics ◽

10.3390/diagnostics11030546 ◽

2021 ◽

Vol 11 (3) ◽

pp. 546

Author(s):

Paula Casal-Beiroa ◽

Vanesa Balboa-Barreiro ◽

Natividad Oreiro ◽

Sonia Pértega-Díaz ◽

Francisco J. Blanco ◽

...

Keyword(s):

Raman Spectroscopy ◽

Articular Cartilage ◽

Ex Vivo ◽

Cartilage Degradation ◽

Calcium Pyrophosphate ◽

Calcium Pyrophosphate Dihydrate ◽

Label Free ◽

Molecular Fingerprint ◽

Human Cartilage ◽

Biochemical Validation

Osteoarthritis (OA) is the most common rheumatic disease, characterized by progressive articular cartilage degradation. Raman spectroscopy (RS) has been recently proposed as a label-free tool to detect molecular changes in musculoskeletal tissues. We used cartilage samples derived from human femoral heads to perform an ex vivo study of different Raman signals and ratios, related to major and minor molecular components of articular cartilage, hereby proposed as candidate optical biomarkers for OA. Validation was performed against the radiological Kellgren–Lawrence (K-L) grading system, as a gold standard, and cross-validated against sulfated glycosaminoglycans (sGAGs) and total collagens (Hyp) biochemical contents. Our results showed a significant decrease in sGAGs (SGAGs, A1063 cm−1/A1004 cm−1) and proteoglycans (PGs, A1375 cm−1/A1004 cm−1) and a significant increase in collagen disorganization (ColD/F, A1245 cm−1/A1270 cm−1), with OA severity. These were correlated with sGAGs or Hyp contents, respectively. Moreover, the SGAGs/HA ratio (A1063 cm−1/A960 cm−1), representing a functional matrix, rich in proteoglycans, to a mineralized matrix-hydroxyapatite (HA), was significantly lower in OA cartilage (K-L I vs. III–IV, p < 0.05), whilst the mineralized to collagenous matrix ratio (HA/Col, A960 cm−1/A920 cm−1) increased, being correlated with K-L. OA samples showed signs of tissue mineralization, supported by the presence of calcium crystals-related signals, such as phosphate, carbonate, and calcium pyrophosphate dihydrate (MGP, A960 cm−1/A1004 cm−1, MGC, A1070 cm−1/A1004 cm−1 and A1050 cm−1/A1004 cm−1). Finally, we observed an increase in lipids ratio (IL, A1450 cm−1/A1670 cm−1) with OA severity. As a conclusion, we have described the molecular fingerprint of hip cartilage, validating a panel of optical biomarkers and the potential of RS as a complementary diagnostic tool for OA.

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Optimizing cisplatin delivery to triple-negative breast cancer through novel EGFR aptamer-conjugated polymeric nanovectors

Journal of Experimental & Clinical Cancer Research ◽

10.1186/s13046-021-02039-w ◽

2021 ◽

Vol 40 (1) ◽

Author(s):

Lisa Agnello ◽

Silvia Tortorella ◽

Annachiara d’Argenio ◽

Clarissa Carbone ◽

Simona Camorani ◽

...

Keyword(s):

Breast Cancer ◽

Triple Negative Breast Cancer ◽

Tumor Targeting ◽

Triple Negative ◽

Ex Vivo ◽

Treatment Options ◽

Negative Control ◽

Therapeutic Effects ◽

Metastatic Setting

Abstract Background Management of triple-negative breast cancer (TNBC) is still challenging because of its aggressive clinical behavior and limited targeted treatment options. Cisplatin represents a promising chemotherapeutic compound in neoadjuvant approaches and in the metastatic setting, but its use is limited by scarce bioavailability, severe systemic side effects and drug resistance. Novel site-directed aptamer-based nanotherapeutics have the potential to overcome obstacles of chemotherapy. In this study we investigated the tumor targeting and the anti-tumorigenic effectiveness of novel cisplatin-loaded and aptamer-decorated nanosystems in TNBC. Methods Nanotechnological procedures were applied to entrap cisplatin at high efficacy into polymeric nanoparticles (PNPs) that were conjugated on their surface with the epidermal growth factor receptor (EGFR) selective and cell-internalizing CL4 aptamer to improve targeted therapy. Internalization into TNBC MDA-MB-231 and BT-549 cells of aptamer-decorated PNPs, loaded with BODIPY505-515, was monitored by confocal microscopy using EGFR-depleted cells as negative control. Tumor targeting and biodistribution was evaluated by fluorescence reflectance imaging upon intravenously injection of Cyanine7-labeled nanovectors in nude mice bearing subcutaneous MDA-MB-231 tumors. Cytotoxicity of cisplatin-loaded PNPs toward TNBC cells was evaluated by MTT assay and the antitumor effect was assessed by tumor growth experiments in vivo and ex vivo analyses. Results We demonstrate specific, high and rapid uptake into EGFR-positive TNBC cells of CL4-conjugated fluorescent PNPs which, when loaded with cisplatin, resulted considerably more cytotoxic than the free drug and nanovectors either unconjugated or conjugated with a scrambled aptamer. Importantly, animal studies showed that the CL4-equipped PNPs achieve significantly higher tumor targeting efficiency and enhanced therapeutic effects, without any signs of systemic toxicity, compared with free cisplatin and untargeted PNPs. Conclusions Our study proposes novel and safe drug-loaded targeted nanosystems for EGFR-positive TNBC with excellent potential for the application in cancer diagnosis and therapy.

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A Tumbling Magnetic Microrobot System for Biomedical Applications

Micromachines ◽

10.3390/mi11090861 ◽

2020 ◽

Vol 11 (9) ◽

pp. 861

Author(s):

Elizabeth E. Niedert ◽

Chenghao Bi ◽

Georges Adam ◽

Elly Lambert ◽

Luis Solorio ◽

...

Keyword(s):

Ultrasound Imaging ◽

Biomedical Applications ◽

Imaging System ◽

Ex Vivo ◽

Negative Control ◽

Circular Path ◽

Rotational Axis ◽

Significant Difference

A microrobot system comprising an untethered tumbling magnetic microrobot, a two-degree-of-freedom rotating permanent magnet, and an ultrasound imaging system has been developed for in vitro and in vivo biomedical applications. The microrobot tumbles end-over-end in a net forward motion due to applied magnetic torque from the rotating magnet. By turning the rotational axis of the magnet, two-dimensional directional control is possible and the microrobot was steered along various trajectories, including a circular path and P-shaped path. The microrobot is capable of moving over the unstructured terrain within a murine colon in in vitro, in situ, and in vivo conditions, as well as a porcine colon in ex vivo conditions. High-frequency ultrasound imaging allows for real-time determination of the microrobot’s position while it is optically occluded by animal tissue. When coated with a fluorescein payload, the microrobot was shown to release the majority of the payload over a 1-h time period in phosphate-buffered saline. Cytotoxicity tests demonstrated that the microrobot’s constituent materials, SU-8 and polydimethylsiloxane (PDMS), did not show a statistically significant difference in toxicity to murine fibroblasts from the negative control, even when the materials were doped with magnetic neodymium microparticles. The microrobot system’s capabilities make it promising for targeted drug delivery and other in vivo biomedical applications.

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A Novel High Sensitivity Type II Collagen Blood-Based Biomarker, PRO-C2, for Assessment of Cartilage Formation

International Journal of Molecular Sciences ◽

10.3390/ijms19113485 ◽

2018 ◽

Vol 19 (11) ◽

pp. 3485 ◽

Cited By ~ 10

Author(s):

Yunyun Luo ◽

Yi He ◽

Ditte Reker ◽

Natasja Gudmann ◽

Kim Henriksen ◽

...

Keyword(s):

Rheumatoid Arthritis ◽

Growth Factor ◽

Knee Osteoarthritis ◽

High Sensitivity ◽

Type Ii Collagen ◽

Cartilage Explants ◽

Type Ii ◽

Serum Samples ◽

Human Cartilage ◽

Cartilage Formation

N-terminal propeptide of type II collagen (PIINP) is a biomarker reflecting cartilage formation. PIINP exists in two main splice variants termed as type IIA and type IIB collagen NH2-propeptide (PIIANP, PIIBNP). PIIANP has been widely recognized as a cartilage formation biomarker. However, the utility of PIIBNP as a marker in preclinical and clinical settings has not been fully investigated yet. In this study, we aimed to characterize an antibody targeting human PIIBNP and to develop an immunoassay assessing type II collagen synthesis in human blood samples. A high sensitivity electrochemiluminescence immunoassay, hsPRO-C2, was developed using a well-characterized antibody against human PIIBNP. Human cartilage explants from replaced osteoarthritis knees were cultured for ten weeks in the presence of growth factors, insulin-like growth factor 1 (IGF-1) or recombinant human fibroblast growth factor 18 (rhFGF-18). The culture medium was changed every seven days, and levels of PIIBNP, PIIANP, and matrix metalloproteinase 9-mediated degradation of type II collagen (C2M) were analyzed herein. Serum samples from a cross-sectional knee osteoarthritis cohort, as well as pediatric and rheumatoid arthritis samples, were assayed for PIIBNP and PIIANP. Western blot showed that the antibody recognized PIIBNP either as a free fragment or attached to the main molecule. Immunohistochemistry demonstrated that PIIBNP was predominately located in the extracellular matrix of the superficial and deep zones and chondrocytes in both normal and osteoarthritic articular cartilage. In addition, the hsPRO-C2 immunoassay exhibits acceptable technical performances. In the human cartilage explants model, levels of PIIBNP, but not PIIANP and C2M, were increased (2 to 7-fold) time-dependently in response to IGF-1. Moreover, there was no significant correlation between PIIBNP and PIIANP levels when measured in knee osteoarthritis, rheumatoid arthritis, and pediatric serum samples. Serum PIIBNP was significantly higher in controls (KL0/1) compared to OA groups (KL2/3/4, p = 0.012). The hsPRO-C2 assay shows completely different biological and clinical patterns than PIIANP ELISA, suggesting that it may be a promising biomarker of cartilage formation.

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