Related Experiment Video
Updated: May 26, 2026
Methods for Evaluating the Role of c-Fos and Dusp1 in Oncogene Dependence
Published on: January 7, 2019
Osteogenic effects of a potent Src-over-Abl-selective kinase inhibitor in the mouse
Richard J Murrills1, Shoichi Fukayama, Frank Boschelli
1Department of Osteoporosis and Frailty, Women's Health and Musculoskeletal Biology, Wyeth Research, Collegeville, Pennsylvania, USA. murrills@aol.com
Abstract:
Src-null mice have higher bone mass because of decreased bone resorption and increased bone formation, whereas Abl-null mice are osteopenic, because of decreased bone formation. Compound I, a potent inhibitor of Src in an isolated enzyme assay (IC(50) 0.55 nM) and a Src-dependent cell growth assay, with lower activity on equivalent Abl-based assays, potently, but biphasically, accelerated differentiation of human mesenchymal stem cells to an osteoblast phenotype (1-10 nM). Compound I (≥0.1 nM) also activated osteoblasts and induced bone formation in isolated neonatal mouse calvariae. Compound I required higher concentrations (100 nM) to inhibit differentiation and activity of osteoclasts. Transcriptional profiling (TxP) of calvaria treated with 1 μM compound I revealed down-regulation of osteoclastic genes and up-regulation of matrix genes and genes associated with the osteoblast phenotype, confirming compound I's dual effects on bone resorption and formation. In addition, calvarial TxP implicated calcitonin-related polypeptide, β (β-CGRP) as a potential mediator of compound I's osteogenic effect. In vivo, compound I (1 mg/kg s.c.) increased vertebral trabecular bone volume 21% (microcomputed tomography) in intact female mice. Increased trabecular volume was also detected histologically in a separate bone, the femur, particularly in the secondary spongiosa (100% increase), which underwent a 171% increase in bone formation rate, a 73% increase in mineralizing surface, and a 59% increase in mineral apposition rate. Similar effects were observed in ovariectomized mice with established osteopenia. We conclude that the Src inhibitor compound I is osteogenic, presumably because of its potent stimulation of osteoblast differentiation and activation, possibly mediated by β-CGRP.
Insights
A novel Src inhibitor, compound I, effectively promotes bone formation and increases bone mass by stimulating osteoblasts and inhibiting osteoclasts. This compound shows therapeutic potential for treating bone loss conditions like osteopenia.
Area of Science:
- Biochemistry
- Bone Biology
- Pharmacology
Background:
- Src-null mice exhibit increased bone mass due to reduced resorption and enhanced formation.
- Abl-null mice display osteopenia resulting from decreased bone formation.
- Src kinase plays a critical role in regulating bone metabolism.
Purpose of the Study:
- To investigate the effects of a potent Src inhibitor, compound I, on bone metabolism.
- To determine compound I's impact on osteoblast differentiation and osteoclast activity.
- To evaluate compound I's therapeutic potential in vivo for bone loss.
Main Methods:
- Enzyme inhibition assays and cell-based assays to assess compound I's potency against Src and Abl.
- In vitro studies on human mesenchymal stem cells and neonatal mouse calvariae to evaluate osteogenic and osteoclastogenic effects.
- Transcriptional profiling (TxP) of calvaria to identify molecular mechanisms and mediators.
- In vivo studies using microcomputed tomography and histology in intact and ovariectomized mice to assess bone mass and formation rates.
Main Results:
- Compound I potently accelerated human mesenchymal stem cell differentiation into osteoblasts (1-10 nM) and activated osteoblasts in vitro.
- Compound I demonstrated dual effects, inhibiting osteoclast differentiation and activity at higher concentrations (100 nM) while promoting osteoblast function.
- Transcriptional profiling revealed down-regulation of osteoclastic genes and up-regulation of osteoblast-related genes, implicating calcitonin-related polypeptide, β (β-CGRP) as a potential mediator.
- In vivo, compound I (1 mg/kg) significantly increased vertebral trabecular bone volume (21%) and enhanced bone formation rates in the femur (171%) in intact and ovariectomized mice.
Conclusions:
- The Src inhibitor compound I exhibits significant osteogenic properties.
- Compound I effectively stimulates osteoblast differentiation and activity, leading to increased bone formation and mass.
- Compound I's dual action on bone resorption and formation, potentially mediated by β-CGRP, suggests its therapeutic utility for osteoporosis and other bone loss conditions.
