%0 Journal Article
%T Cobalt-Alloy Implant Debris Induce HIF-1¦Á Hypoxia Associated Responses: A Mechanism for Metal-Specific Orthopedic Implant Failure
%A Lauryn Samelko
%A Marco S. Caicedo
%A Seung-Jae Lim
%A Craig Della-Valle
%A Joshua Jacobs
%A Nadim J. Hallab
%J PLOS ONE
%D 2013
%I Public Library of Science (PLoS)
%R 10.1371/journal.pone.0067127
%X The historical success of orthopedic implants has been recently tempered by unexpected pathologies and early failures of some types of Cobalt-Chromium-Molybdenum alloy containing artificial hip implants. Hypoxia-associated responses to Cobalt-alloy metal debris were suspected as mediating this untoward reactivity at least in part. Hypoxia Inducible Factor-1¦Á is a major transcription factor involved in hypoxia, and is a potent coping mechanism for cells to rapidly respond to changing metabolic demands. We measured signature hypoxia associated responses (i.e. HIF-1¦Á, VEGF and TNF-¦Á) to Cobalt-alloy implant debris both in vitro (using a human THP-1 macrophage cell line and primary human monocytes/macrophages) and in vivo. HIF-1¦Á in peri-implant tissues of failed metal-on-metal implants were compared to similar tissues from people with metal-on-polymer hip arthroplasties, immunohistochemically. Increasing concentrations of cobalt ions significantly up-regulated HIF-1¦Á with a maximal response at 0.3 mM. Cobalt-alloy particles (1 um-diameter, 10 particles/cell) induced significantly elevated HIF-1¦Á, VEGF, TNF-¦Á and ROS expression in human primary macrophages whereas Titanium-alloy particles did not. Elevated expression of HIF-1¦Á was found in peri-implant tissues and synovial fluid of people with failing Metal-on-Metal hips (n = 5) compared to failed Metal-on-Polymer articulating hip arthroplasties (n = 10). This evidence suggests that Cobalt-alloy, more than other metal implant debris (e.g. Titanium alloy), can elicit hypoxia-like responses that if unchecked can lead to unusual peri-implant pathologies, such as lymphocyte infiltration, necrosis and excessive fibrous tissue growths.
%U http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0067127