Differential gene expression and regulation of the bone morphogenic protein antagonists follistatin and gremlin in normal and osteoarthritic human chondrocytes and synovial fibroblasts
Bibliographic record
Abstract
To compare gene expression and regulation of the bone morphogenic protein (BMP) antagonists follistatin, gremlin, chordin and noggin in human normal and osteoarthritis (OA) chondrocytes and synovial fibroblasts. Follistatin protein production was measured using a specific ELISA, and localization of follistatin and gremlin in cartilage was determined by immunohistochemistry. Basal and induced gene expression was determined using real-time PCR. Gene expression was monitored following treatment with inflammatory, antiinflammatory, growth and developmental factors. All BMP antagonists, except noggin, were expressed in chondrocytes and synovial fibroblasts. Follistatin and gremlin were significantly upregulated in OA chondrocytes, but not in OA synovial fibroblasts. Chordin was weakly expressed in normal and OA cells. Production of follistatin protein paralleled the gene expression pattern. Follistatin was expressed preferentially by the chondrocytes at the superficial zone of cartilage. Gremlin was not detected in normal cartilage; in OA it was found at the superficial zone, not at the very superficial layers of cartilage but rather at the upper intermediary layers. Tumor necrosis factor alpha and interferon gamma stimulated follistatin expression, but downregulated gremlin. IL-1β had no effect on follistatin, but reduced gremlin. Conversely, BMP-2 and BMP-4 significantly stimulated gremlin, but downregulated follistatin. IL-13, dexamethasone, transforming growth factor beta1, basic fibroblast growth factor, platelet-derived growth factor BB and epidermal growth factor down-regulated the expression of both antagonists. We show, for the first time, the involvement of the BMP antagonists follistatin and gremlin in OA pathophysiology. Data suggest that follistatin and gremlin expression is timed with specific stages in the progression of OA. The balance of BMP antagonist levels during the OA process may play a critical role in influencing the progression of OA, making these antagonists interesting new targets for the treatment of this disease.
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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 | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| 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".