TY - JOUR
T1 - Angiogenesis is required for stress fracture healing in rats
AU - Tomlinson, Ryan E.
AU - McKenzie, Jennifer A.
AU - Schmieder, Anne H.
AU - Wohl, Gregory R.
AU - Lanza, Gregory M.
AU - Silva, Matthew J.
N1 - Funding Information:
This study was funded by a grant from the National Institutes of Health ( NIH R01 AR050211 ) and was performed at a facility supported by the Washington University Musculoskeletal Research Center ( NIH P30 AR057235 ). In addition, we acknowledge additional nanomedicine research support from the NIH ( HL113392 , CA100623 , CA154737 , HL094470 , AR056468 , NS073457 , CA136398 ) and the American Heart Association ( 0835426N and 11IRG5690011 ). Dr. Lanza is a scientific cofounder of Kereos, Inc, St. Louis, which has licensed angiogenesis-targeted perfluorocarbon nanotechnology intellectual property from Washington University/Barnes-Jewish Hospital for clinical development. The authors would like to thank Dr. Huiying Zhang for her assistance with immunohistochemistry and Ralph W. Fuhrhop for preparation of the nanoparticle formulations.
PY - 2013/1
Y1 - 2013/1
N2 - Although angiogenesis and osteogenesis are critically linked, the importance of angiogenesis for stress fracture healing is unknown. In this study, mechanical loading was used to create a non-displaced stress fracture in the adult rat forelimb. Fumagillin, an anti-angiogenic agent, was used as the water soluble analogue TNP-470 (25mg/kg) as well as incorporated into lipid-encapsulated αvβ3 integrin targeted nanoparticles (0.25mg/kg). In the first experiment, TNP-470 was administered daily for 5days following mechanical loading, and changes in gene expression, vascularity, and woven bone formation were quantified. Although no changes in vascularity were detected 3days after loading, treatment-related downregulation of angiogenic (Pecam1) and osteogenic (Bsp, Osx) genes was observed at this early time point. On day 7, microCT imaging of loaded limbs revealed diminished woven bone formation in treated limbs compared to vehicle treated limbs. In the second experiment, αvβ3 integrin targeted fumagillin nanoparticles were administered as before, albeit with a 100-fold lower dose, and changes in vascularity and woven bone formation were determined. There were no treatment-related changes in vessel count or volume 3days after loading, although fewer angiogenic (CD105 positive) blood vessels were present in treated limbs compared to vehicle treated limbs. This result manifested on day 7 as a reduction in total vascularity, as measured by histology (vessel count) and microCT (vessel volume). Similar to the first experiment, treated limbs had diminished woven bone formation on day 7 compared to vehicle treated limbs. These results indicate that angiogenesis is required for stress fracture healing, and may have implications for inducing rapid repair of stress fractures.
AB - Although angiogenesis and osteogenesis are critically linked, the importance of angiogenesis for stress fracture healing is unknown. In this study, mechanical loading was used to create a non-displaced stress fracture in the adult rat forelimb. Fumagillin, an anti-angiogenic agent, was used as the water soluble analogue TNP-470 (25mg/kg) as well as incorporated into lipid-encapsulated αvβ3 integrin targeted nanoparticles (0.25mg/kg). In the first experiment, TNP-470 was administered daily for 5days following mechanical loading, and changes in gene expression, vascularity, and woven bone formation were quantified. Although no changes in vascularity were detected 3days after loading, treatment-related downregulation of angiogenic (Pecam1) and osteogenic (Bsp, Osx) genes was observed at this early time point. On day 7, microCT imaging of loaded limbs revealed diminished woven bone formation in treated limbs compared to vehicle treated limbs. In the second experiment, αvβ3 integrin targeted fumagillin nanoparticles were administered as before, albeit with a 100-fold lower dose, and changes in vascularity and woven bone formation were determined. There were no treatment-related changes in vessel count or volume 3days after loading, although fewer angiogenic (CD105 positive) blood vessels were present in treated limbs compared to vehicle treated limbs. This result manifested on day 7 as a reduction in total vascularity, as measured by histology (vessel count) and microCT (vessel volume). Similar to the first experiment, treated limbs had diminished woven bone formation on day 7 compared to vehicle treated limbs. These results indicate that angiogenesis is required for stress fracture healing, and may have implications for inducing rapid repair of stress fractures.
KW - Angiogenesis
KW - Fumagillin
KW - Mechanical loading
KW - Stress fracture
KW - TNP-470
KW - Woven bone formation
UR - http://www.scopus.com/inward/record.url?scp=84867896144&partnerID=8YFLogxK
U2 - 10.1016/j.bone.2012.09.035
DO - 10.1016/j.bone.2012.09.035
M3 - Article
C2 - 23044046
AN - SCOPUS:84867896144
SN - 8756-3282
VL - 52
SP - 212
EP - 219
JO - Bone
JF - Bone
IS - 1
ER -