Consistent expression pattern of myogenic regulatory factors in whole muscle and isolated human muscle satellite cells after eccentric contractions in humans
Bibliographic record
Abstract
Skeletal muscle satellite cells (SC) play an important role in muscle repair following injury. The regulation of SC activity is governed by myogenic regulatory factors (MRF), including MyoD, Myf5, myogenin, and MRF4. The mRNA expression of these MRF in humans following muscle damage has been predominately measured in whole muscle homogenates. Whether the temporal expression of MRF in a whole muscle homogenate reflects SC-specific expression of MRF remains largely unknown. Sixteen young men (23.1 ± 1.0 yr) performed 300 unilateral eccentric contractions (180°/s) of the knee extensors. Percutaneous muscle biopsies from the vastus lateralis were taken before (Pre) and 48 h postexercise. Fluorescence-activated cell sorting analysis was utilized to purify NCAM+muscle SC from the whole muscle homogenate. Forty-eight hours post-eccentric exercise, MyoD, Myf5, and myogenin mRNA expression were increased in the whole muscle homogenate (~1.4-, ~4.0-, ~1.7-fold, respectively, P < 0.05) and in isolated SC (~19.3-, ~17.5-, ~58.9-fold, respectively, P < 0.05). MRF4 mRNA expression was not increased 48 h postexercise in the whole muscle homogenate ( P > 0.05) or in isolated SC ( P > 0.05). In conclusion, our results suggest that the directional changes in mRNA expression of the MRF in a whole muscle homogenate in response to acute eccentric exercise reflects that observed in isolated muscle SC. NEW & NOTEWORTHY The myogenic program is controlled via transcription factors referred to as myogenic regulatory factors (MRF). Previous studies have derived MRF expression from whole muscle homogenates, but little work has examined whether the mRNA expression of these transcripts reflects the pattern of expression in the actual population of satellite cells (SC). We report that MRF expression from an enriched SC population reflects the directional pattern of expression from skeletal muscle biopsy samples following eccentric contractions.
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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 | 0.001 | 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) | 0.001 | 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 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".