title: Biodistribution and PET imaging of a novel [68Ga]-anti-CD163-antibody conjugate in rats with collagen-induced arthritis and in controls.
abstract: OBJECTIVE
  The hemoglobin scavenger receptor CD163 is exclusively expressed on monocytes and tissue macrophages, also at sites of inflammation. We examined whether gallium-68 (Ga-68)-labeled anti-CD163-antibody can detect the receptor in vivo.
  
  
  METHODS
  We radiolabeled anti-CD163 antibody with Ga-68 and evaluated stability and binding specificity of the conjugate ([(68)Ga]ED2) in vitro. Furthermore, tracer biodistribution was assessed in vivo in healthy rats and rats with acute collagen-induced arthritis (CIA) by MicroPET and tissue analysis.
  
  
  RESULTS
  Radiosynthesis of [(68)Ga]ED2 antibody yielded a tracer with high-specific activity and radiochemical purity. [(68)Ga]ED2 bound specifically to CD163 in vitro. In rats, [(68)Ga]ED2 rapidly accumulated in macrophage-rich tissues. The arthritic paws exhibited a low but significant [(68)Ga]ED2 uptake. Interestingly, the systemic distribution was also changed in the sense that a significantly higher liver uptake and lower spleen uptake of [(68)Ga]ED2 was measured in CIA rats that accordingly showed a corresponding change in level of CD163 expression.
  
  
  CONCLUSIONS
  [(68)Ga]ED2 specifically binds CD163 in vitro and in vivo. Biodistribution studies in CIA rats suggest that this novel tool may have applications in studies of inflammatory diseases.
authors: Department of Biomedicine, Aarhus University, Ole Worms Alle 3, Blng 1170, 8000, Aarhus, Denmark.
authors: Sascha
authors: S
authors: Eichendorff
authors: Pia
authors: P
authors: Svendsen
authors: Dirk
authors: D
authors: Bender
authors: Susanne
authors: S
authors: Keiding
authors: Erik I
authors: EI
authors: Christensen
authors: Bent
authors: B
authors: Deleuran
authors: Søren K
authors: SK
authors: Moestrup
mesh_terms: D000818:Animals; D015703:Antigens, CD / Q000737:chemistry*; D015214:Antigens, Differentiation, Myelomonocytic / Q000737:chemistry*; D001168:Arthritis / Q000139:chemically induced / Q000000981:diagnostic imaging*; D016466:CHO Cells; D003094:Collagen / Q000737:chemistry*; D006224:Cricetinae; D003412:Cricetulus; D004195:Disease Models, Animal; D005260:Female; D005708:Gallium / Q000737:chemistry; D005710:Gallium Radioisotopes / Q000737:chemistry*; D006454:Hemoglobins / Q000737:chemistry; D006571:Heterocyclic Compounds / Q000737:chemistry; D006573:Heterocyclic Compounds, 1-Ring; D007249:Inflammation; D008264:Macrophages / Q000000981:diagnostic imaging / Q000473:pathology; D049268:Positron-Emission Tomography; D051381:Rats; D011917:Rats, Inbred Lew; D011956:Receptors, Cell Surface / Q000737:chemistry*; D000098902:CD163 Antigen
chemical_list: D015703:Antigens, CD; D015214:Antigens, Differentiation, Myelomonocytic; D000098902:CD163 Antigen; D005710:Gallium Radioisotopes; D006454:Hemoglobins; D006571:Heterocyclic Compounds; D006573:Heterocyclic Compounds, 1-Ring; D011956:Receptors, Cell Surface; C048993:1,4,7-triazacyclononane-N,N',N''-triacetic acid; D003094:Collagen; D005708:Gallium