title: Novel in vivo method for measuring cholesterol mass flux in peripheral macrophages.
abstract: OBJECTIVE
  Reverse cholesterol transport is the process by which excess cholesterol is removed from peripheral tissue by HDL and delivered to the liver for excretion. Presently, methods of measuring in vivo reverse cholesterol transport do so by monitoring the appearance in the feces of labeled cholesterol that originated from peripheral macrophage foam cells. These methods do not account for changes in macrophage cholesterol mass. We have developed an in vivo assay to measure cholesterol mass changes in atherosclerotic foam cells.
  
  
  RESULTS
  Macrophages are entrapped in semipermeable (pore size 0.2 μm) hollow fibers and surgically implanted into the peritoneum of recipient mice. The fibers are removed from the peritoneum 24 hours after implantation. This method allows the complete recovery of the macrophages for quantification of changes in cholesterol mass and cellular protein. In wild-type mice we measured a significant reduction in total cell cholesterol (TC) when hollow fibers containing cholesterol-enriched macrophage cells were implanted (TC before implantation=105±18 μg/mg cell protein, TC 24 hours after implantation=60±16 μg/mg protein). Additionally, there was an increase in cholesterol content when hollow fibers containing cholesterol-normal macrophages were implanted in an atherogenic mouse model (LDLr/apobec dko) compared to a wild-type mouse (initial TC content=57±24 μg/mg protein, TC 24 hours after implantation: wild-type mice=52±10 μg/mg protein; LDLr/apobec dko mice=118±27 μg/mg protein).
  
  
  CONCLUSIONS
  This assay can quantify in vivo both cholesterol mass accumulation, and reduction, in macrophages. This method permits quantitative analysis of the progression and regression of foam cells.
authors.affiliation: Division of Gastroenterology, Hepatology and Nutrition, The Children's Hospital of Philadelphia, Philadelphia, PA, USA. weibel@email.chop.edu
authors.forename: Ginny L
authors.initials: GL
authors.lastname: Weibel
authors.forename: Sara
authors.initials: S
authors.lastname: Hayes
authors.forename: Aisha
authors.initials: A
authors.lastname: Wilson
authors.forename: Michael C
authors.initials: MC
authors.lastname: Phillips
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Billheimer
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Rader
authors.forename: George H
authors.initials: GH
authors.lastname: Rothblat
mesh_terms: D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters / Q000378:metabolism; D000818:Animals; D001692:Biological Transport; D002478:Cells, Cultured; D002784:Cholesterol / Q000378:metabolism*; D003584:Cytological Techniques / Q000295:instrumentation / Q000379:methods*; D005487:Foam Cells / Q000378:metabolism* / Q000473:pathology; D008099:Liver / Q000378:metabolism; D017737:Macrophages, Peritoneal / Q000378:metabolism* / Q000473:pathology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D023421:Models, Animal; D058226:Plaque, Atherosclerotic / Q000378:metabolism / Q000473:pathology
chemical_list: D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters; D002784:Cholesterol