Transcriptional regulation of ski and scleraxis in primary cardiac myofibroblasts
Bibliographic record
Abstract
Transforming growth factor-β1 (TGFβ1) is a mediator of the fibrotic response through activation of quiescent cardiac fibroblasts to hypersynthetic myofibroblasts. Scleraxis (Scx) is a pro-fibrotic transcription factor that is induced by TGFβ1-3 and works synergistically with Smads to promote collagen expression. Ski is a negative regulator of TGFβ/Smad signaling through its interactions with Smad proteins at the promoter region of TGFβ regulated genes. To date, no studies have examined the direct DNA:protein transcriptional mechanisms that regulate Scx expression by TGFβ1-3 or Ski, nor the mechanisms that govern Ski expression by Scx. We hypothesize that Ski and Scx regulate one another, and form a negative feedback loop that represses gene expression and is a central regulator of the fibrotic response in cardiac myofibroblasts. Primary adult rat cardiac myofibroblasts were isolated via retrograde Langendorff perfusion. First passage (P1) cells were infected with adenovirus encoding HA-Ski, HA-Scx, or LacZ at the time of plating. Twenty-four hours later, cells were harvested for Western blot, quantitative real-time PCR (qPCR), and electrophoretic gel shift assays (EMSA). NIH-3T3 or Cos7 cells were transfected with equal quantities of plasmid DNA for 24 hours prior to harvesting for luciferase, qPCR, and EMSA analysis. Ski overexpression in P1 myofibroblasts resulted in a reduction in both Scx mRNA and protein levels. Overexpression of Scx had no effect on Ski expression. Luciferase reporter assays demonstrated that Scx was induced by TGFβ1 treatment in a concentration dependent manner. However, ectopic Smad2/3 expression was unable to transactivate the Scx promoter in a luciferase reporter assay. Inhibition of p44/42-MAPK signaling modestly counteracted the effect of TGFβ1 on Scx expression. Scx had no effect on Ski promoter expression, however, both tumor necrosis factor-α (TNFα) and p65 expression repressed the Ski promoter and correlated with reduced Ski mRNA levels. We conclude that Ski is a repressor of Scx and that Scx expression is partially mediated through a Smad-independent, p44/42-MAPK pathway in cardiac myofibroblasts. Furthermore, this study proposes a role for TNFα/p65 NF-κΒ signaling in the regulation of Ski gene expression in the cardiac myofibroblast.
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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) | 0.000 | 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 | 0.000 |
| 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".