Effect of Oxygen Levels on Proteoglycan Synthesis by Intervertebral Disc Cells
Bibliographic record
Abstract
STUDY DESIGN: the response of cells from the annulus fibrosus (AF) and nucleus pulposus (NP) to varying oxygen (O2) concentrations was examined when cultured in alginate. OBJECTIVE: to study the effect of O2 concentration on AF and NP cells. SUMMARY OF BACKGROUND DATA: AF and NP cells possess different metabolic profiles in situ. However, it is not clear whether this difference is maintained in in vitro culture conditions. AF and NP cells can respond differently in the different systems, which may differ from the in vivo environment in terms of nutrient supply and O2 levels. In vivo, O2 levels vary from 1% to 5% within the intervertebral disc, and there is evidence that disc cell metabolism can vary with O2 concentrations. METHODS: an alginate scaffold was seeded with bovine AF or NP cells and maintained in culture for up to 18 days under different O2 concentrations. The sulfated glycosaminoglycan (GAG) content in the culture medium and the expression of aggrecan, type I (COL1A2) and II (COL2A1) collagen genes were analyzed at day 9 and day 18. RESULTS: in both NP and AF cells cultured either in normoxia (21% O2) or in hypoxia (5% and 1% O2), the GAG content of the culture medium increased with time, though the rate of increase was diminished in 5% O2. With a decrease in O2 levels, the expression of aggrecan mRNA increased in NP cells. There was little effect of O2 on aggrecan mRNA level in AF cells. However, there was a slight decrease with time. Interestingly, aggrecan mRNA levels did not reflect GAG release for either NP or AF cells. There was no effect with time or O2 levels on COL2A1 message in NP cells. The highest Aggrecan/COL2 message ratio for NP cells was with 1% O2, suggesting this to be the best condition for maintaining the NP phenotype. COL1A2 gene expression in NP and AF cells increased with time, but showed little change with O2 levels in NP cells. The highest COL2/COL1 ratio in NP cells was also observed with 1% O2. Finally, NP cells tended to remain localized in the alginate beads, whereas AF cells tended to migrate from the beads. CONCLUSION: both NP and AF cells showed little change in GAG production with O2 levels ranging from 1% to 21%. Disc cell metabolism is not impaired at low O2 concentrations, which appear beneficial to matrix composition. Furthermore, low oxygen may promote a gelatinous NP matrix, whereas increased oxygen levels may promote a fibrous matrix.
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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) | 0.001 | 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 | 0.000 |
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".