Osteogenic effects of a potent Src-over-Abl-selective kinase inhibitor in the mouse.

Murrills RJ, Fukayama S, Boschelli F, Matteo JJ, Owens J, Golas JM, Patel D, Lane G, Liu YB, Carter L, Jussif J, Spaulding V, Wang YD, Boschelli DH, McKew JC, Li XJ, Lockhead S, Milligan C, Kharode YP, Diesl V, Bai Y, Follettie M, Bex FJ, Komm B, Bodine PV.
Source: J Pharmacol Exp Ther
Publication Date: (2012)
Issue: 340(3): 676-87
Research Area:
Stem Cells
Basic Research
Cells used in publication:
Mesenchymal stem cell (MSC), human
Species: human
Tissue Origin: bone marrow
Osteoclast precursor (OCP), human
Species: human
Tissue Origin: bone marrow
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, ß (ß-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 ß-CGRP.