title: TLR4 accessory molecule RP105 (CD180) regulates monocyte-driven arteriogenesis in a murine hind limb ischemia model.
abstract: OBJECTIVE
  We investigated the role of the TLR4-accessory molecule RP105 (CD180) in post-ischemic neovascularization, i.e. arteriogenesis and angiogenesis. TLR4-mediated activation of pro-inflammatory Ly6Chi monocytes is crucial for effective neovascularization. Immunohistochemical analyses revealed that RP105+ monocytes are present in the perivascular space of remodeling collateral arterioles. As RP105 inhibits TLR4 signaling, we hypothesized that RP105 deficiency would lead to an unrestrained TLR4-mediated inflammatory response and hence to enhanced blood flow recovery after ischemia.
  
  
  RESULTS
  RP105-/- and wild type (WT) mice were subjected to hind limb ischemia and blood flow recovery was followed by Laser Doppler Perfusion Imaging. Surprisingly, we found that blood flow recovery was severely impaired in RP105-/- mice. Immunohistochemistry showed that arteriogenesis was reduced in these mice compared to the WT. However, both in vivo and ex vivo analyses showed that circulatory pro-arteriogenic Ly6Chi monocytes were more readily activated in RP105-/- mice. FACS analyses showed that Ly6Chi monocytes became activated and migrated to the affected muscle tissues in WT mice following induction of hind limb ischemia. Although Ly6Chi monocytes were readily activated in RP105-/- mice, migration into the ischemic tissues was hampered and instead, Ly6Chi monocytes accumulated in their storage compartments, bone marrow and spleen, in RP105-/- mice.
  
  
  CONCLUSIONS
  RP105 deficiency results in an unrestrained inflammatory response and monocyte over-activation, most likely due to the lack of TLR4 regulation. Inappropriate, premature systemic activation of pro-inflammatory Ly6Chi monocytes results in reduced infiltration of Ly6Chi monocytes in ischemic tissues and in impaired blood flow recovery.
authors.affiliation: Department of Surgery, Leiden University Medical Center, Leiden, the Netherlands; Einthoven Laboratory for Experimental Vascular Medicine, Leiden University Medical Center, Leiden, the Netherlands.
authors.forename: Antonius J N M
authors.initials: AJ
authors.lastname: Bastiaansen
authors.affiliation: Department of Surgery, Leiden University Medical Center, Leiden, the Netherlands; Einthoven Laboratory for Experimental Vascular Medicine, Leiden University Medical Center, Leiden, the Netherlands.
authors.forename: Jacco C
authors.initials: JC
authors.lastname: Karper
authors.affiliation: Department of Surgery, Leiden University Medical Center, Leiden, the Netherlands; Einthoven Laboratory for Experimental Vascular Medicine, Leiden University Medical Center, Leiden, the Netherlands; Department of Biopharmaceutics, Leiden Academic Centre for Drug Research, Leiden University, Leiden, the Netherlands.
authors.forename: Anouk
authors.initials: A
authors.lastname: Wezel
authors.affiliation: Einthoven Laboratory for Experimental Vascular Medicine, Leiden University Medical Center, Leiden, the Netherlands; Department of Nephrology, Leiden University Medical Center, Leiden, the Netherlands.
authors.forename: Hetty C
authors.initials: HC
authors.lastname: de Boer
authors.affiliation: Department of Surgery, Leiden University Medical Center, Leiden, the Netherlands; Einthoven Laboratory for Experimental Vascular Medicine, Leiden University Medical Center, Leiden, the Netherlands.
authors.forename: Sabine M J
authors.initials: SM
authors.lastname: Welten
authors.affiliation: Department of Surgery, Leiden University Medical Center, Leiden, the Netherlands; Einthoven Laboratory for Experimental Vascular Medicine, Leiden University Medical Center, Leiden, the Netherlands.
authors.forename: Rob C M
authors.initials: RC
authors.lastname: de Jong
authors.affiliation: Department of Surgery, Leiden University Medical Center, Leiden, the Netherlands; Einthoven Laboratory for Experimental Vascular Medicine, Leiden University Medical Center, Leiden, the Netherlands.
authors.forename: Erna A B
authors.initials: EA
authors.lastname: Peters
authors.affiliation: Department of Surgery, Leiden University Medical Center, Leiden, the Netherlands; Einthoven Laboratory for Experimental Vascular Medicine, Leiden University Medical Center, Leiden, the Netherlands.
authors.forename: Margreet R
authors.initials: MR
authors.lastname: de Vries
authors.affiliation: Einthoven Laboratory for Experimental Vascular Medicine, Leiden University Medical Center, Leiden, the Netherlands; Department of Nephrology, Leiden University Medical Center, Leiden, the Netherlands.
authors.forename: Annemarie M
authors.initials: AM
authors.lastname: van Oeveren-Rietdijk
authors.affiliation: Einthoven Laboratory for Experimental Vascular Medicine, Leiden University Medical Center, Leiden, the Netherlands; Department of Nephrology, Leiden University Medical Center, Leiden, the Netherlands.
authors.forename: Anton Jan
authors.initials: AJ
authors.lastname: van Zonneveld
authors.affiliation: Department of Surgery, Leiden University Medical Center, Leiden, the Netherlands.
authors.forename: Jaap F
authors.initials: JF
authors.lastname: Hamming
authors.affiliation: Department of Surgery, Leiden University Medical Center, Leiden, the Netherlands; Einthoven Laboratory for Experimental Vascular Medicine, Leiden University Medical Center, Leiden, the Netherlands.
authors.forename: A Yaël
authors.initials: AY
authors.lastname: Nossent
authors.affiliation: Department of Surgery, Leiden University Medical Center, Leiden, the Netherlands; Einthoven Laboratory for Experimental Vascular Medicine, Leiden University Medical Center, Leiden, the Netherlands.
authors.forename: Paul H A
authors.initials: PH
authors.lastname: Quax
mesh_terms: D000818:Animals; D015703:Antigens, CD / Q000235:genetics / Q000378:metabolism*; D000950:Antigens, Ly / Q000235:genetics / Q000378:metabolism; D001783:Blood Flow Velocity; D001854:Bone Marrow Cells / Q000166:cytology; D002465:Cell Movement; D003097:Collateral Circulation; D004195:Disease Models, Animal; D017353:Gene Deletion; D015870:Gene Expression; D006614:Hindlimb / Q000098:blood supply / Q000378:metabolism* / Q000473:pathology; D007511:Ischemia / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D017078:Laser-Doppler Flowmetry; D051379:Mice; D018345:Mice, Knockout; D009000:Monocytes / Q000378:metabolism* / Q000473:pathology; D018919:Neovascularization, Physiologic / Q000235:genetics*; D013154:Spleen / Q000166:cytology; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000378:metabolism*
chemical_list: D015703:Antigens, CD; D000950:Antigens, Ly; C494192:Ly-6C antigen, mouse; C490500:Ly78 protein, mouse; C493487:Tlr4 protein, mouse; D051197:Toll-Like Receptor 4