Transient Exposure to Hypoxic and Anoxic Oxygen Concentrations Promotes Either Osteogenic or Ligamentogenic Characteristics of PDL Cells
Bibliographic record
Abstract
The periodontal ligament (PDL) has a reservoir of mesenchymal stem cells (MSCs) and this tissue is easily available following teeth removal procedures. However, PDL-derived cells (PDLCs) availability for tissue engineering is limited because they are heterogeneous cells at various differentiation and lineage commitments. Therefore, efficient culture conditions to increase MSCs number are needed to use PDLCs in tissue engineering. Recent reports indicate that low-oxygen conditions amplified stem/progenitor cell numbers and inhibited cell differentiation. Our aim was to establish which low-oxygen culture conditions favored bone or tendon/ligament regeneration in cultured PDLCs. Human PDLCs were cultured and exposed to either hypoxic (O2≤5%) or anoxic (O2<0.1%) oxygen conditions in low-glucose/serum-free media for 24 hours. After 24 h, as expected, cell survival was significantly less in PDLCs exposed to anoxic conditions as compared with cells under normal or hypoxic conditions. PDLCs exposed to hypoxic conditions had the highest percentages for MSC markers (CD105, CD166, Stro-1). For both hypoxic and anoxic conditions, stem cell marker genes (oct4, sox2, p75) were upregulated after 6 h. At 24 h, these stem cell markers were maintained in PDLCs under hypoxic condition. Interestingly under anoxic conditions, expression of scleraxis gene (a key transcription factor for tendo/ligamentogenesis) was upregulated markedly. When hypoxic PDLCs were subcultured into osteogenic medium, in vitro calcification and prominent in vivo bone formation in mice calvaria were observed. When anoxic PDLCs were subcultured into tendo/ligamentogenic medium, expression of aggrecan (a mature tenogenic gene) increased remarkably. No obvious differences were detectable on chondrogenic and adipogenic inducibilities. We propose that transient exposure to low-oxygen during the culture enhanced MSC population in PDL. In addition, different low-oxygen concentrations favored osteogenic or tendo/ligamentogenic inducibilities of cultured PDLCs.
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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 | 0.002 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.001 |
| 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 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".