Modulation of endochondral ossification by MEK inhibitors PD0325901 and AZD6244 (Selumetinib)

• Published in: Bone (New York, N.Y.) Vol. 59; pp. 151 - 161
• Main Authors: El-Hoss, J, Kolind, M, Jackson, M.T, Deo, N, Mikulec, K, McDonald, M.M, Little, C.B, Little, D.G, Schindeler, A
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Inc 01.02.2014; Elsevier
• Subjects: Animals; Benzamides - pharmacology; Benzimidazoles - pharmacology; Biological and medical sciences; Bone Marrow Cells - cytology; Bone Marrow Cells - drug effects; Bone Marrow Cells - metabolism; Bony Callus - drug effects; Bony Callus - pathology; Cancer; Cartilage - drug effects; Cartilage - growth & development; Cartilage remodeling; Cell Differentiation - drug effects; Chondrocytes - drug effects; Chondrocytes - metabolism; Chondrocytes - pathology; Diphenylamine - analogs & derivatives; Diphenylamine - pharmacology; Endochondral ossification; Fracture healing; Fracture Healing - drug effects; Fundamental and applied biological sciences. Psychology; Injuries of the limb. Injuries of the spine; MAP Kinase Signaling System - drug effects; Medical sciences; Mice; Mice, Inbred C57BL; Mitogen-Activated Protein Kinase Kinases - antagonists & inhibitors; Mitogen-Activated Protein Kinase Kinases - metabolism; Multiple tumors. Solid tumors. Tumors in childhood (general aspects); Orthopedics; Osteoblasts - cytology; Osteoblasts - drug effects; Osteoblasts - enzymology; Osteoclasts - drug effects; Osteoclasts - enzymology; Osteogenesis - drug effects; Osteoprotegerin - blood; Protein Kinase Inhibitors - pharmacology; RANK Ligand - blood; Ras–MAPK; Sheep; Skull - cytology; Traumas. Diseases due to physical agents; Tumors; Vertebrates: anatomy and physiology, studies on body, several organs or systems; X-Ray Microtomography; Fracture healing; Cartilage remodeling; Endochondral ossification; Ras–MAPK; Cancer; Diseases of the osteoarticular system; Fracture; Malignant tumor; Trauma; Ossification; Cartilage; Morphology; Ras―MAPK; Cicatrization
• DOI: 10.1016/j.bone.2013.11.013
• ISSN: 8756-3282

Abstract MEK inhibitors (MEKi) PD0325901 and AZD6244 (Selumetinib) are drugs currently under clinical investigation for cancer treatment, however the Ras–MAPK pathway is also an important mediator of normal bone cell differentiation and function. In this study we examined the effects of these compounds on endochondral processes using both in vitro and in vivo models. Treatment with PD0325901 or AZD6244 significantly increased Runx2 and Alkaline phosphate gene expression in calvarial osteoblasts and decreased TRAP + cells in induced osteoclast cultures. To test the effects of these drugs on bone healing, C57/Bl6 mice underwent a closed tibial fracture and were treated with PD0325901 or AZD6244 at 10 mg/kg/day. Animals were culled at day 10 and at day 21 post-fracture for analysis of the fracture callus and the femoral growth plate in the contralateral leg. MEKi treatment markedly increased cartilage volume in the soft callus at day 10 post-fracture (+ 60% PD0325901, + 20% AZD6244) and continued treatment led to a delay in cartilage remodeling. At the growth plate, we observed an increase in the height of the hypertrophic zone relative to the proliferative zone of + 78% in PD0325901 treated mice. Osteoclast surface was significantly decreased both at the terminal end of the growth plate and within the fracture calluses of MEKi treated animals. The mechanistic effects of MEKi on genes encoding cartilage matrix proteins and catabolic enzymes were examined in articular chondrocyte cultures. PD0325901 or AZD6244 led to increased matrix protein expression ( Col2a1 and Acan ) and decreased expression of catabolic factors ( Mmp13 and Adamts-5 ). Taken together, these data support the hypothesis that MEKi treatment can impact chondrocyte hypertrophy, matrix resorption, and fracture healing. These compounds can also affect bone architecture by expanding the hypertrophic zone of the growth plate and reducing osteoclast surface systemically.