Inhibition of angiotensin-converting enzyme stimulates fracture healing and periosteal callus formation - role of a local renin-angiotensin system.
OBJECTIVE
The renin-angiotensin system (RAS) regulates blood pressure and electrolyte homeostasis. In addition, 'local' tissue-specific RAS have been identified, regulating regeneration, cell growth, apoptosis, inflammation and angiogenesis. Although components of the RAS are expressed in osteoblasts and osteoclasts, a local RAS in bone has not yet been described and there is no information on whether the RAS is involved in fracture healing. Therefore, we studied the expression and function of the key RAS component, angiotensin-converting enzyme (ACE), during fracture healing.


METHODS
In a murine femur fracture model, animals were treated with the ACE inhibitor perindopril or vehicle only. Fracture healing was analysed after 2, 5 and 10 weeks using X-ray, micro-CT, histomorphometry, immunohistochemistry, Western blotting and biomechanical testing.


RESULTS
ACE was expressed in osteoblasts and hypertrophic chondrocytes in the periosteal callus during fracture healing, accompanied by expression of the angiotensin type-1 and type-2 receptors. Perindopril treatment reduced blood pressure and bone mineral density in unfractured femora. However, it improved periosteal callus formation, bone bridging of the fracture gap and torsional stiffness. ACE inhibition did not affect cell proliferation, but reduced apoptotic cell death. After 10 week treatment, a smaller callus diameter and bone volume after perindopril treatment indicated an advanced stage of bone remodelling.


CONCLUSIONS
Our study provides evidence for a local RAS in bone that influenced the process of fracture healing. We show for the first time that inhibition of ACE is capable of accelerating bone healing and remodelling.
Department of Trauma-, Hand- and Reconstructive Surgery, University of Saarland, Homburg/Saar, Germany. chpgar@uniklinikum-saarland.de
P
P
Garcia
S
S
Schwenzer
J E
JE
Slotta
C
C
Scheuer
A E
AE
Tami
J H
JH
Holstein
T
T
Histing
M
M
Burkhardt
T
T
Pohlemann
M D
MD
Menger
D000806:Angiotensin-Converting Enzyme Inhibitors / Q000494:pharmacology*; D000818:Animals; D002146:Bony Callus; D005260:Female; D005264:Femoral Fractures; D017102:Fracture Healing / Q000187:drug effects*; D008297:Male; D051379:Mice; D007703:Peptidyl-Dipeptidase A / Q000378:metabolism*; D010521:Periosteum / Q000187:drug effects*; D012084:Renin-Angiotensin System
D000806:Angiotensin-Converting Enzyme Inhibitors; D007703:Peptidyl-Dipeptidase A