Effect of Sodium Bicarbonate on Extracellular pH, Matrix Accumulation, and Morphology of Cultured Articular Chondrocytes
Bibliographic record
Abstract
Tissue engineering is a promising approach for articular cartilage repair; however, attempts to develop tissue that mimic native cartilage have been problematic. The synthesis and accumulation of extracellular matrix macromolecules may be adversely affected by a change in pH of the media during cell culture. Typically, zwitterion buffers (e.g., HEPES) are used in culture media because they can perform under both slightly acidic and alkaline conditions. However, because chondrocytes tend to rapidly acidify the media, better pH maintenance may be achieved by utilizing additional buffering agents that operate under acidic conditions (e.g., bicarbonate). The purpose of this study was to investigate the combined effect of HEPES and sodium bicarbonate (NaHCO(3)) on extracellular pH and matrix accumulation by cultured articular chondrocytes. Isolated bovine articular chondrocytes were seeded on Millicell filters and cultured in HEPES-buffered media containing 0, 7, or 14 mM NaHCO(3). Throughout the 4-week culture period, the extracellular pH was more neutral with increasing NaHCO(3) concentration. Addition of NaHCO(3) increased synthesis (140 +/- 29%) and accumulation (20 +/- 2%) of proteoglycans whereas collagen was unaffected. There was also an increase in tissue cellularity (41 +/- 13%). Morphologically, increasing numbers of flattened cells, resembling superficial zone chondrocytes, localized to the surface of the in vitro-formed tissue with increasing NaHCO(3) supplementation were observed by light and transmission electron microscopy. Experiments are underway to determine whether these effects are due to pH maintenance or to the increased concentration of bicarbonate ions, which regulate intracellular pH.
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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) | 0.001 | 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) | 0.001 | 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".