Myelination of the human hippocampal formation in Down syndrome
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1
University of Pécs, Central Electron Microscopic Laboratory, Medical School, Hungary
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2
University of Pécs, Department of Pathology, Medical School, Hungary
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3
University of Pécs, Department of Obstetrics and Gynecology, Medical School, Hungary
In our present study, myelination of the hippocampal formation was examined and compared in Down syndrome (DS) and control human cases form the 20th gestational weeks to adulthood using immunocytochemistry for myelin basic protein (MBP) synthesized by oligodendroglial (OLG) cells. We found that cytoarchitectonics of the hippocampal formation in DS were very similar to the controls. The first MBP-immunoreactive OLGs appeared in fornix and alveus in both DS fetuses and controls, but their overall number was decreased in DS. The sequence of myelination in the different regions and layers of hippocampal formation in DS was identical with that of the controls, although, in DS patients, the overall density of myelinated fibers were apparently reduced compared to age-matched controls, even at 2 years of age. In contrast to Ammon’s horn where myelination starts prenatally, the first myelinated axons in the hilus could be detected only postnatally. The hilus of the dentate gyrus contains a relatively low density of myelinated axons, because axons of granule cells are unmyelinated. Therefore, a difference in density of myelin staining could be observed between the hilus of the dentate gyrus and layers of Ammon’s horn, in both children and adults. A significant reduction of density of myelinated fibers could be detected in the hilus in DS compared to controls, even in adulthood. Density of myelin staining in young adult DS patients (17 and 23 years old) did not reach the level found in early school age of controls (5 years). The density of myelination further decreased between the 20th and 65th years in DS. Due to the key role of subcortical projection in hippocampal function, we hypothesize that mental retardation in DS patients may be either the result of lower number of subcortical axons terminating in hippocampal formation including the hilus, or a diminished myelination and abnormal conducting velocity of these pathway.
Supported by the Bolyai Scholarship to H. Ábrahám.
Conference:
IBRO International Workshop 2010, Pécs, Hungary, 21 Jan - 23 Jan, 2010.
Presentation Type:
Poster Presentation
Topic:
Development
Citation:
Vincze
A,
Kravják
A,
Veszprémi
B,
Seress
L and
Ábrahám
H
(2010). Myelination of the human hippocampal formation in Down syndrome.
Front. Neurosci.
Conference Abstract:
IBRO International Workshop 2010.
doi: 10.3389/conf.fnins.2010.10.00018
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Received:
16 Apr 2010;
Published Online:
16 Apr 2010.
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Correspondence:
Andras Vincze, University of Pécs, Central Electron Microscopic Laboratory, Medical School, Pécs, Hungary, vinczeandras83@gmail.com