title: Tissue factor detection for selectively discriminating unstable plaques in an atherosclerotic rabbit model.
abstract: Tissue factor (TF), a transmembrane glycoprotein that acts as an essential cofactor to factor VII/VIIa, initiates the exogenous blood coagulation cascade leading to thrombin generation and subsequent thrombus formation in vivo. TF expression is closely related to plaque vulnerability, and high TF expression is shown in macrophage-rich atheromatous lesions, making TF a potential target for detecting atheromatous lesions in vivo. Thus, we prepared (99m)Tc-labeled anti-TF-monoclonal antibody (TF-mAb) IgG as a molecular probe and evaluated its usefulness to achieve TF-specific imaging using myocardial infarction-prone Watanabe heritable hyperlipidemic (WHHLMI) rabbits.
  
  
  METHODS
  Anti-TF-mAb was created using a standard hybridoma technique and was labeled by (99m)Tc with 6-hydrazinonicotinic acid (HYNIC) as a chelating agent to obtain (99m)Tc-TF-mAb. The immunoreactivity of HYNIC-TF-mAb was estimated by flow cytometry. WHHLMI and control rabbits were injected intravenously with (99m)Tc-TF-mAb. Twenty-four hours after the injection, the aorta was removed and radioactivity was measured. Autoradiography and histologic studies were performed using serial aorta sections. Subclass matched antibody (IgG(1)) was used as a negative control.
  
  
  RESULTS
  HYNIC-TF-mAb showed 93% immunoreactivity of the anti-TF-mAb. The radioactivity accumulation in WHHLMI aortas was 6.1-fold higher than that of control rabbits. Autoradiograms showed a heterogeneous distribution of radioactivity in the intima of WHHLMI aortas. Regional radioactivity accumulation was positively correlated with TF expression density (R = 0.64, P < 0.0001). The highest radioactivity accumulation in percentage injected dose × body weight/mm(2) × 10(2) was found in atheromatous lesions (5.2 ± 1.9) followed by fibroatheromatous (2.1 ± 0.7), collagen-rich (1.8 ± 0.7), and neointimal lesions (1.8 ± 0.6). In contrast, (99m)Tc-IgG(1) showed low radioactivity accumulation in WHHLMI aortas that was independent of the histologic grade of lesions.
  
  
  CONCLUSIONS
  The TF-detecting ability and preferential accumulation in atheromatous lesions of (99m)Tc-TF-mAb were demonstrated, indicating its potential for selective imaging of macrophage-rich atheromatous lesions in vivo.
authors.affiliation: Department of Patho-Functional Bioanalysis, Graduate School of Pharmaceutical Sciences, Kyoto University, Sakyo-ku, Kyoto, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Temma
authors.forename: Yuki
authors.initials: Y
authors.lastname: Ogawa
authors.forename: Yuji
authors.initials: Y
authors.lastname: Kuge
authors.forename: Seigo
authors.initials: S
authors.lastname: Ishino
authors.forename: Nozomi
authors.initials: N
authors.lastname: Takai
authors.forename: Kantaro
authors.initials: K
authors.lastname: Nishigori
authors.forename: Masashi
authors.initials: M
authors.lastname: Shiomi
authors.forename: Masahiro
authors.initials: M
authors.lastname: Ono
authors.forename: Hideo
authors.initials: H
authors.lastname: Saji
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal; D050197:Atherosclerosis / Q000000981:diagnostic imaging* / Q000473:pathology; D001345:Autoradiography; D005434:Flow Cytometry; D006834:Hydrazines / Q000737:chemistry / Q000493:pharmacokinetics; D006949:Hyperlipidemias / Q000150:complications / Q000473:pathology; D007074:Immunoglobulin G / Q000737:chemistry; D008297:Male; D015335:Molecular Probes; D009539:Nicotinic Acids / Q000737:chemistry / Q000493:pharmacokinetics; D011817:Rabbits; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals / Q000138:chemical synthesis / Q000493:pharmacokinetics; D012044:Regression Analysis; D017556:Technetium Compounds / Q000138:chemical synthesis; D013925:Thromboplastin / Q000096:biosynthesis; D014018:Tissue Distribution
chemical_list: C120392:6-hydrazinopyridine-3-carboxylic acid; D000911:Antibodies, Monoclonal; D006834:Hydrazines; D007074:Immunoglobulin G; D015335:Molecular Probes; D009539:Nicotinic Acids; D019275:Radiopharmaceuticals; D017556:Technetium Compounds; D013925:Thromboplastin