Liposomal alendronate inhibits systemic innate immunity and reduces in-stent neointimal hyperplasia in rabbits.
BACKGROUND
Innate immunity is of major importance in vascular repair. The present study evaluated whether systemic and transient depletion of monocytes and macrophages with liposome-encapsulated bisphosphonates inhibits experimental in-stent neointimal formation.


RESULTS
Rabbits fed on a hypercholesterolemic diet underwent bilateral iliac artery balloon denudation and stent deployment. Liposomal alendronate (3 or 6 mg/kg) was given concurrently with stenting. Monocyte counts were reduced by >90% 24 to 48 hours after a single injection of liposomal alendronate, returning to basal levels at 6 days. This treatment significantly reduced intimal area at 28 days, from 3.88+/-0.93 to 2.08+/-0.58 and 2.16+/-0.62 mm2. Lumen area was increased from 2.87+/-0.44 to 3.57+/-0.65 and 3.45+/-0.58 mm2, and arterial stenosis was reduced from 58+/-11% to 37+/-8% and 38+/-7% in controls, rabbits treated with 3 mg/kg, and rabbits treated with 6 mg/kg, respectively (mean+/-SD, n=8 rabbits/group, P<0.01 for all 3 parameters). No drug-related adverse effects were observed. Reduction in neointimal formation was associated with reduced arterial macrophage infiltration and proliferation at 6 days and with an equal reduction in intimal macrophage and smooth muscle cell content at 28 days after injury. Conversely, drug regimens ineffective in reducing monocyte levels did not inhibit neointimal formation.


CONCLUSIONS
Systemic transient depletion of monocytes and macrophages, by a single liposomal bisphosphonates injection concurrent with injury, reduces in-stent neointimal formation and arterial stenosis in hypercholesterolemic rabbits.
Danenberg
Haim D
HD
Harvard-MIT Division of Health Sciences and Technology, Massachusetts Institute of Technology, Cambridge, Mass 02139, USA. danen@mit.edu
Golomb
Gershon
G
Groothuis
Adam
A
Gao
Jianchuan
J
Epstein
Hila
H
Swaminathan
Rajesh V
RV
Seifert
Philip
P
Edelman
Elazer R
ER
D019386:Alendronate / Q000008:administration & dosage / Q000494:pharmacology*; D000818:Animals; D002452:Cell Count; D002455:Cell Division / Q000187:drug effects; D002465:Cell Movement / Q000187:drug effects / Q000276:immunology; D004036:Diet, Atherogenic; D004195:Disease Models, Animal; D006083:Graft Occlusion, Vascular / Q000276:immunology / Q000473:pathology / Q000517:prevention & control*; D006965:Hyperplasia / Q000276:immunology / Q000473:pathology / Q000517:prevention & control*; D007083:Iliac Artery / Q000187:drug effects / Q000293:injuries / Q000473:pathology; D007113:Immunity, Innate / Q000187:drug effects*; D007958:Leukocyte Count; D008081:Liposomes; D008264:Macrophages / Q000187:drug effects / Q000473:pathology; D009000:Monocytes / Q000187:drug effects / Q000473:pathology; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000473:pathology; D011817:Rabbits; D015607:Stents / Q000009:adverse effects; D017539:Tunica Intima / Q000187:drug effects* / Q000276:immunology / Q000473:pathology
D008081:Liposomes; D019386:Alendronate