Blocking the Expression of Both Bone Sialoprotein (BSP) and Osteopontin (OPN) Impairs the Anabolic Action of PTH in Mouse Calvaria Bone
Bibliographic record
Abstract
Osteopontin (OPN) and bone sialoprotein (BSP) are coexpressed in osteoblasts and osteoclasts, and display overlapping properties. We used daily injection of parathyroid hormone 1-84 (iPTH) over the calvaria of BSP knockout (-/-) mice to investigate further their functional specificity and redundancy. iPTH stimulated bone formation in both +/+ and -/- mice, increasing to the same degree periosteum, osteoid and total bone thickness. Expression of OPN, osterix, osteocalcin (OCN) and DMP1 was also increased by iPTH in both genotypes. In contrast to +/+, calvaria cell cultures from -/- mice revealed few osteoblast colonies, no mineralization and little expression of OCN, MEPE or DMP1. In contrast, OPN levels were 5× higher in -/- versus +/+ cultures. iPTH increased alkaline phosphatase (ALP) activity in cell cultures of both genotypes, with higher OCN and the induction of mineralization in -/- cultures. siRNA blocking of OPN expression did not alter the anabolic action of the hormone in BSP +/+ calvaria, while it blunted iPTH effects in -/- mice, reduced to a modest increase in periosteum thickness. In -/- (not +/+) cell cultures, siOPN blocked the stimulation by iPTH of ALP activity and OCN expression, as well as the induction of mineralization. Thus, full expression of either OPN or BSP is necessary for the anabolic effect of PTH at least in the ectopic calvaria injection model. This suggests that OPN may compensate for the lack of BSP in the response to this hormonal challenge, and provides evidence of functional overlap between these cognate proteins.
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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 | 0.001 | 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) | 0.000 | 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".