Histological analyses of the effects of MGP overexpression on limb long bone development. In the control limb, femur (fe), tibia (ti), and tarsal (ta) elements display normal elongated morphology (A). Their diaphyses stain positively with alizarin red (A), are surrounded by an intramembranous bone collar (C and E, arrow), and display fully hypertrophic chondrocytes (E, arrowhead) and invading marrow cells (E, double arrow). In RCAS-MGP limb, tibia is completely cartilaginous and does not stain with alizarin red (B); its diaphysis lacks both a bone collar (D, arrow) and fully hypertrophic chondrocytes (F, arrowheads). Bars (A and B) 2.5 mm; (C–F) 80 μm.
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