TGFβ and osteoblast differentiation in a novel, serum‐free co‐culture system
Bibliographic record
Abstract
Our lab has previously described the production of large quantities of activated TGFβ coincident with chondrocyte hypertrophy. In this study, we investigated osteoblast differentiation in response to chondrocyte‐produced TGFβ. Early (EH) and late (LH) hypertrophic chondrocyte populations were isolated from avian sterna and placed in serum‐free alginate cultures. At day 5, the chondrocytes were transferred to serum‐free co‐culture with subconfluent monolayer of early mature osteoblasts (HOB‐03‐CE6; EMOB). At 24 hours, EMOB responded to EH and LH chondrocytes with a decrease in osterix gene expression, an osteoblast transcription factor. These data paralleled TGFβ‐treated control EMOB monolayers and previous experiments with EH and LH conditioned media‐treated EMOBs. Osteopontin gene expression, an extracellular matrix molecule, was increased in TGFβ‐treated EMOB controls and EH and LH co‐cultures, again, paralleling previous results with conditioned media‐treatment. Smad2 and its phosphorylated form are the second messenger system for the TGFβ receptor. Immunocytochemistry revealed Smad2 staining in the cytoplasm of all cultured conditions. When compared to control monolayers of EMOBs, TGFβ‐treated, EH and LH co‐cultured EMOBs demonstrated a shift to predominantly nuclear localization for the phosphorylated Smad2. These data suggest that TGFβ produced by hypertrophic chondrocytes can alter osteoblast gene expression at the chondro‐osseous border.
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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 | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 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".