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A RANKL-based Osteoclast Culture Assay of Mouse Bone Marrow to Investigate the Role of mTORC1 in Osteoclast Formation
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Receptor tyrosine kinase inhibition causes simultaneous bone loss and excess bone formation within growing bone in

Mirja Nurmio1, Henna Joki, Jenny Kallio

  • 1Department of Physiology, University of Turku, Finland. Mirja.Nurmio@utu.fi

Toxicology and Applied Pharmacology
|May 19, 2011
PubMed

Insights

The receptor tyrosine kinase inhibitor imatinib disrupts normal bone growth in young rats. Imatinib causes osteopetrosis at the growth plate and bone loss in trabecular bone, altering skeletal development.

Area of Science:

  • Skeletal Biology
  • Pharmacology
  • Developmental Biology

Background:

  • Postnatal skeletal growth involves cellular adaptation to mechanical loading at the growth plate.
  • Receptor tyrosine kinase (RTK) inhibitors, like imatinib mesylate, impact bone-forming and bone-resorbing cells.
  • Imatinib targets multiple receptors (PDGF, ABL, c-Kit, c-Fms) crucial for bone microenvironment functions.

Purpose of the Study:

  • To investigate the effects of imatinib on bone physiology during postnatal skeletal growth in young rats.
  • To evaluate how RTK inhibition by imatinib influences bone modeling and remodeling processes in vivo.

Main Methods:

  • Young rats were treated with imatinib at different doses and durations during postnatal development.
  • Evaluations included X-ray imaging, computer tomography (CT), histomorphometry, RNA analysis, and immunohistochemistry.
  • Peripheral quantitative CT (pQCT) and micro-CT were used to analyze bone structure and remodeling.

Main Results:

  • Imatinib treatment eliminated osteoclasts at the metaphyseal osteochondral junction, causing resorption arrest and local osteopetrosis.
  • Increased osteoblast activity and bone apposition were observed at the osteochondral junction.
  • Conversely, distal trabecular bone showed increased osteoclast activity and bone loss.
  • These alterations in bone remodeling persisted from early postnatal stages into adulthood.

Conclusions:

  • Imatinib significantly alters bone modeling and remodeling during postnatal skeletal growth.
  • The drug induces site-specific effects, leading to osteopetrosis at the growth plate and bone loss in trabecular regions.
  • These findings highlight the critical role of RTKs in regulating bone development and the potential consequences of their inhibition.

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