Arteriogenesis requires toll-like receptor 2 and 4 expression in bone-marrow derived cells.
Adaptive collateral growth (arteriogenesis) is an important protective mechanism against ischemic injury in patients with cardiovascular disease. Arteriogenesis involves enlargement of pre-existent arterial anastomoses and shares many mechanistic similarities with inflammatory processes. Although infusion of the Toll-like receptor (TLR) 4 ligand lipopolysaccharide (LPS) has shown to result in a significant stimulation of arteriogenesis and both Toll-like receptor 2 and 4 are involved in structural arterial adaptations, the requirement for TLRs in arteriogenesis has not yet been established. We therefore subjected TLR 2 null and TLR 4 defective mice to unilateral femoral artery occlusion. At 7 days, both TLR 2 null and TLR 4 defective mice showed a significant reduction (~35%) of collateral perfusion. Histological staining showed that TLR 2 and TLR 4 expression during arteriogenesis is mostly restricted to infiltrating leukocytes. To distinguish between the functional importance of vascular and leukocytic TLRs in arteriogenesis, cross-over bone marrow transplantation was performed 6 weeks before femoral artery occlusion. Perfusion measurements showed that transplantation of wild-type bone marrow into TLR 2 null and TLR 4 defective mice rescued the impaired arteriogenesis, while injection of TLR 2 null and TLR 4 defective bone marrow into wild-type mice significantly reduced collateral vessel growth to levels of TLR null/defective mice. RT-PCR analysis demonstrated a significant upregulation of two endogenous TLR ligands EDA and Hsp60 (91.7 fold and 1.9 fold respectively) in regions of collateral vessel formation. This study illustrates the involvement of TLR 2 and TLR 4 in adaptive collateral artery growth and shows the importance of TLR 2 and 4 expression by bone-marrow derived cells for this process.
de Groot
Daphne
D
Laboratory of Experimental Cardiology, HLCU, UMC, University of Utrecht, The Netherlands.
Hoefer
Imo E
IE
Grundmann
Sebastian
S
Schoneveld
Arjan
A
Haverslag
René T
RT
van Keulen
J Karlijn
JK
Bot
Pieter T
PT
Timmers
Leo
L
Piek
Jan J
JJ
Pasterkamp
Gerard
G
de Kleijn
Dominique P V
DP
D000818:Animals; D001158:Arteries / Q000166:cytology*; D001854:Bone Marrow Cells / Q000166:cytology / Q000378:metabolism*; D016026:Bone Marrow Transplantation; D005434:Flow Cytometry; D007113:Immunity, Innate / Q000235:genetics / Q000502:physiology; D051379:Mice; D008817:Mice, Mutant Strains; D018919:Neovascularization, Physiologic / Q000235:genetics / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D051195:Toll-Like Receptor 2 / Q000235:genetics / Q000378:metabolism*; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000378:metabolism*
D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4