Identification of novel collagen breakdown products by human osteoclasts in vitro and in vivo
Notice bibliographique
Résumé
Abstract Bone resorption involves dissolution of mineral and enzymatic degradation of bone matrix. The primary enzyme is cathepsin K but other proteases including matrix metalloproteinases are involved. Some cleavage products of cathepsin K have been partially identified, including crossed-linked telopeptides of type I collagen. However, the pathway of type I bone collagen degradation has not been fully elucidated. The aim of this study was to comprehensively characterise the entire complement of bone breakdown products resulting from osteoclast action under controlled conditions in vitro . Complete characterisation of these breakdown products will advance understanding of osteoclast biology and has the potential to reveal new biomarkers of bone resorption. We analysed extracellular media from osteoclasts cultured on dentine substrates, using untargeted liquid chromatography mass spectrometry. We discovered 22 breakdown products resulting from osteoclastic action. These products were peptide fragment sequences that mapped to various collagen proteins present in bone and dentine matrix. Nine peptide fragments mapped exclusively to collagen I alpha-1 chain (COL1A1), the most abundant protein in bone. Analysis of the reported cleavage sites in the COL1A1 protein sequence indicated 7/9 COL1A1-specific fragments not explained by known proteolytic events. We subsequently showed that 14 of the fragment products were present in human serum and/or urine from metabolomic datasets obtained from patients with the inherited metabolic disease alkaptonuria (serum) and lung cancer (urine). Two products were at higher concentration (P <0.05, fold change >2) in urine from patients with bone metastasis (29/112) from the lung cancer cohort. The range of collagen peptide fragments we discovered as a direct result of osteoclast activity indicates a complexity of bone resorption pathways not previously known. Monitoring the concentrations of these novel bone markers in biofluids has the potential to capture multiple pathways of bone resorption activity beyond the existing assays based on Cathepsin K. Lay summary Breakdown of bone tissue is performed by specialised bone cells called osteoclasts in a process known as bone resorption. Knowledge of specific molecules produced from osteoclasts acting on bone is important for a) understanding bone resorption in health and disease, and b) clinical tests of bone resorption from measurement of these breakdown products. Here we aimed to characterise the entire complement of bone breakdown products resulting from osteoclast action under controlled conditions in the laboratory. We found a total of 22 breakdown products produced from osteoclasts cultured on wafers of dentine, a tissue with almost identical composition to bone. Analysis of the structures of these products revealed fragments of varying size produced from digestion of specific proteins present in bone. We then showed that 14/22 bone protein fragments observed in our cell culture experiments were also present in human blood and/or urine. In our analysis of urine from patients with lung cancer, we found that two of the protein fragments we identified were higher in a subset (29/112) of patients with bone metastasis. Our findings provide new insights into the mechanisms of bone resorption and show the potential for monitoring the range of urine bone protein fragments in bone disorders.
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Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».