Up-regulated expression of the phosphodiesterase nucleotide pyrophosphatase family member PC-1 is a marker and pathogenic factor for knee meniscal cartilage matrix calcification
Bibliographic record
Abstract
OBJECTIVE: Elevated cartilage inorganic pyrophosphate (PPi) production and PPi-generating nucleoside triphosphate pyrophosphohydrolase (NTPPPH) activity are strongly linked with aging-related cartilage calcification in meniscal and articular cartilages. We hypothesized that there were divergent relationships of 3 NTPPPH isozymes with cartilage matrix calcification and sought to identify them. METHODS: We studied knee medial meniscal expression in situ of 3 NTPPPH isozymes of the phosphodiesterase nucleotide pyrophosphatase (PDNP) family: plasma cell membrane glycoprotein 1 (PC-1, or PDNP1), autotaxin (ATX, or PDNP2), and B10/PDNP3. We also used complementary DNA transfection to assess differential functions in matrix calcification of each NTPPPH isozyme in vitro in meniscal cells. RESULTS: We observed diffuse cell-associated ATX and B10/PDNP3 expression in central (chondrocytic) and, to a lesser degree, peripheral (fibroblastic) regions of normal, degenerative uncalcified, and degenerative calcified menisci. In contrast, PC-1 expression was only robust at sites of apoptotic cells and calcification in central regions of degenerative menisci. Only PC-1 was abundant at the perimeter of meniscal cells and in association with meniscal cell-derived matrix vesicles (MVs). Because each PDNP-family isozyme was expressed by cells near calcifications, we transfected the isozymes in nonadherent knee meniscal cells cultured with ascorbic acid, beta-glycerophosphate, and dexamethasone supplementation to stimulate them to calcify the matrix. PC-1, but not ATX or B10/PDNP3, consistently promoted increased MV NTPPPH, MV-associated PPi, and extracellular PPi. PC-1 also increased matrix calcification (with hydroxyapatite crystals) by meniscal cells. ATX uniquely induced alkaline phosphatase activity, but promoted only moderately increased matrix calcification. CONCLUSION: We identified divergent effects of 3 PDNP-family NTPPPH isozymes on meniscal cell matrix calcification. Increased expression of PC-1 is both a marker and a potential pathogenic factor for knee meniscal cartilage matrix calcification.
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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) | 0.001 | 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".