Inactivation of Pten in osteo-chondroprogenitor cells leads to epiphyseal growth plate abnormalities and skeletal overgrowth

J Bone Miner Res. 2007 Aug;22(8):1245-59. doi: 10.1359/jbmr.070420.


To study the role of the Pten tumor suppressor in skeletogenesis, we generated mice lacking this key phosphatidylinositol 3'-kinase pathway regulator in their osteo-chondroprogenitors. A phenotype of growth plate dysfunction and skeletal overgrowth was observed.

Introduction: Skeletogenesis is a complex process relying on a variety of ligands that activate a range of intracellular signal transduction pathways. Although many of these stimuli are known to activate phosphatidylinositol 3'-kinase (PI3K), the function of this pathway during cartilage development remains nebulous. To study the role of PI3K during skeletogenesis, we used mice deficient in a negative regulator of PI3K signaling, the tumor suppressor, Pten.

Materials and methods: Pten gene deletion in osteo-chondrodroprogenitors was obtained by interbreeding mice with loxP-flanked Pten exons with mice expressing the Cre recombinase under the control of the type II collagen gene promoter (Pten(flox/flox):Col2a1Cre mice). Phenotypic analyses included microcomputed tomography and immunohistochemistry techniques.

Results: MicroCT revealed that Pten(flox/flox):Col2a1Cre mice exhibited both increased skeletal size, particularly of vertebrae, and massive trabeculation accompanied by increased cortical thickness. Primary spongiosa development and perichondrial bone collar formation were prominent in Pten(flox/flox):Col2a1Cre mice, and long bone growth plates were disorganized and showed both matrix overproduction and evidence of accelerated hypertrophic differentiation (indicated by an altered pattern of type X collagen and alkaline phosphatase expression). Consistent with increased PI3K signaling, Pten-deficient chondrocytes showed increased phospho-PKB/Akt and phospho-S6 immunostaining, reflective of increased mTOR and PDK1 activity. Interestingly, no significant change in growth plate proliferation was seen in Pten-deficient mice, and growth plate fusion was found at 6 months.

Conclusions: By virtue of its ability to modulate a key signal transduction pathway responsible for integrating multiple stimuli, Pten represents an important regulator of both skeletal size and bone architecture.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apoptosis
  • Bone and Bones / abnormalities
  • Bone and Bones / enzymology*
  • Cell Differentiation*
  • Chondrocytes / cytology*
  • Chondrocytes / metabolism*
  • Collagen Type II / genetics
  • Enzyme Activation
  • Gene Deletion
  • Gene Expression Regulation, Enzymologic
  • Growth Plate / abnormalities
  • Growth Plate / enzymology*
  • Mice
  • Mice, Knockout
  • Osteoblasts / cytology
  • Osteoblasts / enzymology*
  • PTEN Phosphohydrolase / deficiency
  • PTEN Phosphohydrolase / genetics
  • PTEN Phosphohydrolase / metabolism*
  • Promoter Regions, Genetic / genetics


  • Collagen Type II
  • PTEN Phosphohydrolase