AAT – A Novel Cartilage‐Protective Mediator
Bibliographic record
Abstract
Introduction The resolution of inflammation is a process that ensures repair and restoration of tissue physiology. Using integrated approach with proteomic analyses and bio‐assays with human chondrocytes and experimental arthritis, we identified α 1 ‐Antitrypsin(AAT), the chief neutrophil elastase(NE) inhibitor, as a novel chondroprotective protein produced in resolving exudates. Methods Resolving rat pleural exudates (24h post‐carrageenan injection) were run for mass spectrometry using ion‐trap mass analyzer (MS/MS LTQ Orbitrap XL). Human C28/I2 chondrocytes were grown in high‐density micromass(MM) 1 incubated with AAT with/without catabolic stimuli interleukin(IL)‐1β (20ng/ml) or osteoarthritic synovial fluids (OASF; 1:100) for 48h. Glycosaminoglycans (GAG) deposition was assessed using Alcian Blue(AB) staining. Gene expression was quantified by qPCR. Data are expressed as 2 −ΔΔCt equation–relative amount of target genes, normalized to GAPDH and vehicle, with expression set to 1.0 (N=3). Inflammatory arthritis was induced though K/BxN serum transfer model 2 . Knee joint structure and cartilage integrity were determined 48h after intra‐articular(i.a.) or intra‐peritoneal(i.p.) injection of AAT (n=8) by the GAG‐sensitive toluidine blue staining of knee sections. Knee inflammation (diameter; n=14), changes in leukocyte kinetics (number of rolling and adherent leukocytes; intravital microscopy; n=8), blood perfusion (Laser Speckle Contrast Analysis; n=8), and pain (von Frey algesiometry; n=8) were evoked by i.a. injection of NE (5μg) 3 with/without AAT(100ng) and quantified 4h post‐injection. One‐way ANOVA, or student's T‐test were applied for stats. Results Proteomics identified AAT in pro‐resolving (24h post‐carrageenan) exudates. Exogenous AAT abrogated the effect of IL‐1β on MMP13 ( p <0.05). Incubation of chondrocyte MM with OASF augmented IL6 and MMP13 mRNA, with concomitant down‐regulation of COL2A1 and ACAN gene products: tested at 3–10 μg/ml, AAT significantly attenuated these effects ( p <0.01). GAG deposition confirmed the chondroprotection afforded by AAT: ~80% reduction by OASF and reversal to control levels with AAT ( p <0.01). In the model of arthritis, knee joint cartilage was eroded by ~65% (GAG content; p <0.05). Intra‐articular injection of AAT(100ng) recovered cartilage integrity by 52% compared to vehicle‐injected contralateral joints ( p <0.05). Systemic AAT (10μg i.p.) reduced cartilage destruction by ~30%, compared to vehicle‐injected animals ( p <0.05). NE induced acute inflammation and pain in knee joints of mice: it caused a marked increase in knee diameter, synovial microcirculation, vascular response with increased leukocyte kinetics and a decrease in hindpaw withdrawal threshold ( p <0.01). Co‐administration of NE and AAT(100ng) significantly counteracted NE‐induced knee inflammation ( p <0.01) and potently reverted the NE‐induced pain ( p <0.01). Conclusion Using resolving exudates as a bio‐source, we identified the neutrophil elastase inhibitor AAT as a novel tissue‐protective protein with a broad spectrum of activities, thus paving the way for new strategies to prevent joint pain and repair/restore compromised cartilage functions.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".