Abnormal collagen type I production in osteoarthritic subchondral bone is associated with a reduced capacity of osteoblasts to mineralize in vitro
Bibliographic record
Abstract
Osteoarthritis (OA) is characterized by cartilage loss, synovial inflammation, osteophytes, and abnormal subchondral bone remodeling including sclerosis. Bone sclerosis in OA is due to an abundant osteoid collagen matrix. Collagen type 1 synthesis is increased in in vivo OA bone tissue and there is an abnormal ratio of collagen type 1α1 chains (Coll1α1) to Coll1α2 chains in this tissue. The mechanisms responsible for this abnormal osteoid matrix remain unknown. In this study using in vitro subchondral osteoblasts (Ob) from normal and OA individuals, we investigated the mechanisms responsible for abnormal collagen production. We used primary human subchondral Ob from normal and OA individuals. Cells were stimulated or not with 100 ng/ml parathyroid hormone (PTH), 500 nM prostaglandin E 2 (PGE 2 ) or 50 nM 1,25(OH) 2 D 3 . RNA was extracted with TRIzol and used to perform RT-PCR and real-time PCR of Coll1A1 and Coll1A2. Coll1 synthesis was assessed as the release of the carboxy terminal peptide fragment (CICP), which reflects de novo collagen synthesis. Proteins were separated by SDS-PAGE and detected using selective antibodies against Coll1α1, Coll1α2, or membrane-type 1 or membrane-type 2 matrix metalloprotease (MT1-MMP and MT2-MMP). MMP-2 and MMP-9 activities were assessed by zymography. Mineralization was evaluated by the von Kossa staining of cells after 30 days of culture in the presence or not of 10 ng/ml bone morphogenic protein-2 (BMP-2). Data showed that basal Coll1A1 mRNA levels were significantly increased in OA Ob compared with normal using real-time PCR, whereas Coll1A2 levels in OA Ob were similar to normal. This translated into an α1 to α2 collagen type I ratio of 2.5 in normal Ob whereas it increased to 7.2 in OA Ob. PTH and PGE 2 both reduced Coll1A1 and Coll1A2 mRNA levels in normal Ob yet this was reduced for OA Ob. Indeed, PGE 2 reduced Coll1A1 and Coll1A1 mRNA levels about half as in normal, and the effect of PTH was virtually absent in OA Ob. Basal collagen type I synthesis, determined by the release of the C-terminal propeptide and by western blot analysis, was also higher in OA Ob than normal. MMP-2 and MMP-9 were increased in OA Ob compared with normal as determined by zymography. Western blot analysis showed an increase in MT2-MMP but not in MT1-MMP in OA Ob. Finally, the mineralization of OA Ob was significantly reduced compared with normal as determined by Von Kossa staining under both basal conditions and following BMP-2 stimulation. These results suggest that a cellular defect of OA Ob and an abnormal response to PTH and PGE 2 challenge could explain abnormal production and ratio of α1 to α2 chains of mature collagen type 1 in these cells. Coupled to the increase in MMP activities, this could explain the abnormal collagen remodeling observed in OA bone tissue in vivo .
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.002 | 0.003 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.004 |
| 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) | 0.000 | 0.000 |
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 teacher head, 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".