title: Characterization of myelin pathology in the hippocampal complex of a transgenic mouse model of Alzheimer's disease.
abstract: We have characterized the myelin changes observed within the hippocampal complex (HC) of a transgenic (Tg) mouse model of Alzheimer's disease (AD). Individual myelinated fibers were labeled with Black-Gold II while amyloid plaques were labeled with either Congo Red or Pan-A-beta immunofluoresence. Myelinated fibers were never seen passing through amyloid plaques in any region, while conspicuous myelin pathology was seen within, and immediately adjacent to, the amyloid plaques in the HC of the AD-Tg mouse. This pathology consisted of a complete disruption of myelinated fibers passing through the plaque and the region immediately adjacent to the plaques exhibited an edematous swelling of the fibers. This pathology was most frequently observed within the molecular and polymorph layers of the dentate gyrus and the molecular layer of Ammon's horn. The remaining layers of Ammon's horn exhibited minimal myelin pathology, while moderate myelinopathy was observed in the subiculum. Since the HC is integral for memory function, these findings may help account for the memory problems so characteristic of the disease process. Because the molecular layers of the dentate gyrus and Ammon's horn are the sites of inputs to the HC, the extensive myelin pathology observed in these regions would imply functional deafferentation of the HC. The appearance of some Black-Gold II positive debris within the plaques may reflect a possible cascade mechanism whereby the presence of plaques results in myelin degeneration, some of which is incorporated within the plaque, causing it to further expand in a self-perpetuating fashion.
authors.affiliation: Division of Neurotoxicology, National Center for Toxicological Research/FDA, Jefferson AR 72079, USA. larry.schmued@fda.hhs.gov
authors.forename: Larry C
authors.initials: LC
authors.lastname: Schmued
authors.forename: James
authors.initials: J
authors.lastname: Raymick
authors.forename: Merle G
authors.initials: MG
authors.lastname: Paule
authors.forename: Melanie
authors.initials: M
authors.lastname: Dumas
authors.forename: Sumit
authors.initials: S
authors.lastname: Sarkar
mesh_terms: D000367:Age Factors; D000544:Alzheimer Disease / Q000235:genetics / Q000473:pathology*; D016229:Amyloid beta-Peptides / Q000378:metabolism; D016564:Amyloid beta-Protein Precursor / Q000235:genetics; D000818:Animals; D004195:Disease Models, Animal; D006624:Hippocampus / Q000473:pathology*; D006801:Humans; D051379:Mice; D008822:Mice, Transgenic; D009154:Mutation / Q000235:genetics; D009186:Myelin Sheath / Q000473:pathology*; D010446:Peptide Fragments / Q000378:metabolism; D058225:Plaque, Amyloid / Q000473:pathology; D053764:Presenilin-1 / Q000235:genetics; D013194:Staining and Labeling
chemical_list: D016229:Amyloid beta-Peptides; D016564:Amyloid beta-Protein Precursor; C508853:PSEN1 protein, human; D010446:Peptide Fragments; D053764:Presenilin-1; C078592:amyloid beta-protein (1-40)