Acta Neuropathol

DOI 10.1007/s00401-016-1565-x

ORIGINAL PAPER

Dura mater is a potential source of Aβ seeds

Gabor G. Kovacs1 · Mirjam I. Lutz1 · Gerda Ricken1 · Thomas Ströbel1 ·
Romana Höftberger1 · Matthias Preusser2 · Günther Regelsberger1 ·
Selma Hönigschnabl3 · Angelika Reiner3 · Peter Fischer4 · Herbert Budka1,5 ·
Johannes A. Hainfellner1

Received: 16 February 2016 / Revised: 14 March 2016 / Accepted: 15 March 2016

© The Author(s) 2016. This article is published with open access at Springerlink.com

Abstract Deposition of amyloid-β (Aβ) in the brain cognitive decline carrying one or two APOE4 alleles, and
parenchyma and vessels is one of the hallmarks of Alzhei- from that related to traumatic brain injury. Our novel find-
mer disease (AD). Recent observations of Aβ deposition ings of Aβ deposits in the dura mater, including the grafted
in iatrogenic Creutzfeldt-Jakob disease (iCJD) after dural dura, and the distinct cerebral Aβ distribution in iCJD sup-
grafting or treatment with pituitary extracts raised concerns port the seeding properties of Aβ. However, in contrast to
whether Aβ is capable of transmitting disease as seen in prion diseases, our study suggests that such Aβ seeding is
prion diseases by the disease-associated prion protein. To unable to reproduce the full clinicopathological phenotype
address this issue, we re-sampled and re-evaluated archi- of AD.
val material, including the grafted dura mater of two cases
with iCJD (28 and 33-years-old) without mutations in the Keywords Alzheimer disease · Amyloid-β · Dura mater ·
AβPP, PSEN1 and PSEN2 genes, and carrying ε3/ε3 alleles Iatrogenic Creutzfeldt-Jakob disease · Prion · Propagon
of the APOE gene. In addition, we evaluated 84 dura mater
samples obtained at autopsy (mean age 84.9 ± 0.3) in the
community-based VITA study for the presence of Aβ depo- Introduction
sition. We show that the dura mater may harbor Aβ depos-
its (13 %) in the form of cerebral amyloid angiopathy or Neurodegenerative diseases are characterized by progres-
amorphous aggregates. In both iCJD cases, the grafted dura sive loss of neurons and dysfunction of functional systems
mater had accumulated Aβ. The morphology and distribu- associated with deposition of pathological forms of proteins
tion pattern of cerebral Aβ deposition together with the predominantly in the central nervous system [31]. These
lack of tau pathology distinguishes the Aβ proteinopathy in proteins, such as amyloid-β (Aβ), tau, α-synuclein, TAR
iCJD from AD, from that seen in young individuals without DNA-binding protein TDP-43 or prion protein (PrP) can be
used as biomarkers. However, a further important aspect is
whether these proteins are capable of transmitting disease
* Gabor G. Kovacs between individuals, which would have significant public
gabor.kovacs@meduniwien.ac.at
health implications. This issue has received support from
1
Institute of Neurology, Medical University Vienna, AKH 4J, experimental observations; furthermore, the hierarchical
Währinger Gürtel 18‑20, 1097 Vienna, Austria involvement of anatomical regions, considered as phases or
2
Department of Medicine I and Comprehensive Cancer Center stages of disease, has been also considered to support the
CNS Unit, Medical University Vienna, Vienna, Austria prion-like spread of disease-associated proteins [9, 15, 21,
3
Institute of Pathology, Danube Hospital Vienna, Vienna, 37, 55, 56]. Indeed, prion diseases are still the only protein
Austria misfolding disorders where human- or animal-to-human
4
Psychiatric Department, Medical Research Society Vienna, transmission has been proven. To fine-tune the terminology,
D.C., Danube Hospital, Vienna, Austria recently the term propagon has been introduced and at least
5
Institute of Neuropathology, University Hospital Zurich, four conceptual levels have been defined, such as molec-
Zurich, Switzerland ular, tissue, systemic and infectious propagons [15]. As

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suggested, only prion diseases fulfill all four levels, while Materials and methods
this has not yet been shown convincingly for other neuro-
degeneration-related proteins [15, 37, 55]. However, recent Acquisition of cases
reports showed that iatrogenic Creutzfeldt-Jakob disease
(iCJD) due to cadaveric pituitary hormones [25] or dura Two cohorts were examined in this study. The first cohort
mater implantation [18, 46] frequently associates with Aβ consisted of two autopsy cases of iCJD collected in the
deposition, suggesting that Aβ acts as a seed or infectious frame of the Austrian Surveillance for human prion dis-
propagon as defined recently [15]. However, these studies eases. Both patients underwent dura mater transplan-
did not evaluate the original source material nor focused on tation: case iCJD-1 was a 33-year-old female patient,
distinctive neuropathological features of these cases. and iCJD-2 was a 28-year-old male patient. The latter
Aβ deposition is one important component of neuro- case was reported previously [46]. We re-evaluated both
pathological alterations that together with the accumulation cases carefully and sampled further anatomical areas
of abnormally phosphorylated intracellular tau allows the including the implanted and host dura mater. The sec-
tissue diagnosis of Alzheimer disease (AD) [14]. In con- ond cohort consisted of 84 consecutive dura mater sam-
trast to prion diseases, AD is characterized by slowly pro- ples collected in the frame of the community-based VITA
gressive cognitive decline. Importantly, Aβ shows on one study [16, 34]. The mean age at death (±standard error)
hand a maturation process [42] and on the other hand a of individuals in the VITA cohort was 84.9 ± 0.3 (range
hierarchical involvement of brain regions [53]. Moreover, 79–89 years); male/female ratio was 33/51). The study
two distinct patterns of neocortical involvement have been was performed following local regulations as approved by
suggested, namely a homogenous distribution in all lay- the local ethical committee (EK07-056-VK, 206/05/2008,
ers or a laminar pattern [12]. Cerebral amyloid angiopathy EK396-2011).
(CAA) with Aβ immunoreactivity is a frequent observation
in the ageing and AD brains, which is thought to be related Neuropathology
to failure of the interstitial fluid drainage of the brain [5,
10]. Two types of CAA are distinguished and three stages Formalin-fixed, paraffin-embedded tissue blocks were eval-
of brain involvement have been proposed [51, 52]. uated. Tissue blocks examined in iCJD cases comprised
Importantly, Aβ plaques can be observed in young indi- bilateral samples of the frontal (frontobasal area of trau-
viduals associated with the presence of the ε4 allele of the matic surgery and dorsolateral), anterior cingular, lower,
apolipoprotein E (APOE) gene [45]. On the other hand middle and upper temporal, parietal, and occipital cortices
neuronal phospho-tau pathology can be seen in subcortical with white matter, hippocampus, entorhinal cortex, basal
nuclei from the second decade of life and precedes cortical ganglia, thalamus, mesencephalon, pons, medulla oblon-
involvement [7, 8, 20, 50]. Furthermore, accelerated neuro- gata, and cerebellum. In case iCJD-1 we evaluated the
degeneration has been reported after traumatic brain injury implanted and immediately adjacent host dura mater. In
(TBI) either after single or, as chronic traumatic encepha- case iCJD-2 the whole dura mater was available; thus we
lopathy (CTE), following repetitive brain trauma [27, 28, evaluated samples from the implanted areas and from those
40, 41]. Aβ deposits together with tau-positive neurofibril- parts of the dura mater not involved in the traumatic injury
lary tangles reminiscent of AD are seen already after single (host dura, at least 5 cm distance from the surgical inter-
TBI [28], while in CTE, tau pathology with stages of brain vention from both sides).
involvement is the major finding, which is associated with In the VITA cohort we sampled the left temporal region
deposition of further neurodegeneration-related proteins, of the dura mater including branches of the middle menin-
including Aβ [39–41]. geal artery (2 × 2 cm) as well as three cross-sections in the
In the present study we were thus interested to clarify area of the superior sagittal sinus and confluence of sinuses.
whether (1) the pattern of Aβ deposition in iCJD following In addition to Hematoxylin and Eosin (HE), Congo red,
cadaveric dura mater implantation would be distinguisha- van Gieson elastica, and Bielschowsky stainings, the fol-
ble from that seen in AD, in cognitively normal young indi- lowing monoclonal antibodies were used for immunohis-
viduals, or in TBI; (2) the dural grafts in iCJD cases would tochemistry: anti-PrP (1:1000, 12F10, Cayman Chemical,
show Aβ deposition; and (3) the dura mater would accu- Ann Arbor, MI, USA), anti-Aβ (1:100, clone 6F/3D, Dako,
mulate Aβ in non-CJD cases. To answer these questions Glostrup, Denmark), anti-Aβ (1:4000, clone 4G8, Signet,
we re-sampled and carefully re-evaluated archival material, San Diego, CA, USA), anti-Aβ1-40 (1:800, clone 139-5,
including the grafted dura mater of two cases with iCJD. In Signet, San Diego, CA USA), anti-Aβ1–42 (1:200, clone
addition, we systematically evaluated dura mater samples 1-11-3, Signet, San Diego, CA USA), anti-AβPP (1:8000,
collected in the community-based Vienna Trans-Danube clone 22C11, Millipore, Temecula, CA, USA), anti-phos-
Aging (VITA) study for the presence of Aβ deposition. pho-tau (1:200, clone AT8, Pierce Endogen, Waltham, MA,

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USA), smooth muscle actin (1:200, clone HHF35, Dako, by surgical implantation of lyophilized cadaveric dura
Glostrup, Denmark), anti-ubiquitin (1:50,000, Millipore, 25 years before death. After the operation epileptic seizures
Temecula, CA, USA), anti-HLA-DR (1:100, clone CR3/43, occurred; the last one 15 years before death. She developed
Dako), anti-CD-68 (1:5000, clone KP1, Dako), and colla- progressive dementia at the age of 33 associated with cer-
gen IV (1:100, clone CIV22, Dako, Glostrup, Denmark; to ebellar ataxia, myoclonus and pyramidal signs. She died
label basement membrane). The following tissue pretreat- due to bronchopneumonia after 4 months disease duration.
ments were used for the Aβ antibodies prior to incubation CSF 14-3-3 protein was positive and EEG revealed tripha-
with primary antibodies: for 6F/3D and 4G8 1 h 80 % sic waves. There was a lack of reports on amnestic or focal
formic acid (FA); for anti-Aβ1–40 and anti-Aβ1–42 10 min cortical symptoms before the development of progressive
70 % FA, for AT8 no pretreatment. Additional enhanced neurological symptoms. There was no family history of
Proteinase K (PK) treatment (50 μg/ml) was used for dementia or any other neurological disease.
6F/3D and 4G8 for 5 min at 37°C to test for PK resistance Case iCJD-2 was a 28-year-old man who had suffered
of the detected dural Aβ deposits. The Dako EnVision™ a traumatic open left frontobasal skull fracture with brain
FLEX + Mouse / Rabbit detection system (Dako, Glostrup, contusion and tearing of the dura mater 22 years before
Denmark) was used for visualization of antibody reactions. death [46]. The dural defect was surgically covered using
In the VITA cohort we correlated the presence of dif- lyophilized cadaveric dura. At the age of 27 he devel-
ferent Aβ deposits in the dura with neuropathological oped progressive dementia, myoclonus and seizures, later
variables, including presence and phase of Aβ deposi- pyramidal signs and akinetic mutism. There were no pre-
tion, presence and type of CAA, stages of neurofibrillary ceding symptoms. CSF 14-3-3 protein was positive, EEG
degeneration, presence of Lewy body, TDP-43 and vascular revealed periodic sharp waves, and cranial MRI showed
pathology (see Ref. [34]). Chi square test and Fisher’s exact discrete hyperintensity of the caudate nucleus and putamen
test were used to evaluate association between variables of in T2 weighted images. Two months before death a diag-
interest. IBM SPSS Statistics Version 20 was used for sta- nostic brain biopsy of the left frontal lobe was performed.
tistical analysis. A significance level of 0.05 was used. Disease duration was 8 months. There was no family his-
tory of dementia or any other neurological disease.
Gene analysis Genetic analysis of presenilin 2 (PSEN2) revealed
polymorphic sites at codons 23, 43 and 87 (c.69T>C;
Genomic DNA was isolated using the QIAamp DNA Mini p.Ala23Ala, c.129C>T; p.Asn43Asn and c.261C>T;
Kit (QIAGEN, Hilden, Germany) according to the manu- p.His87His, respectively) in both iCJD patients. These pol-
facturer’s instructions using frozen brain tissue of the two ymorphisms have been reported as having no pathogenic
iCJD cases (Case 1 and 2). All primer pairs were designed impact. In AβPP exons 16 and 17, presenilin 1 (PSEN1)
to amplify the coding exons of PSEN1, PSEN2 (preseni- and PRNP no pathogenic mutation was observed in both
lin 1, 2), PRNP (prion protein gene) and exon 16 and 17 patients. Case iCJD-1 was heterozygous (methionine/
of AβPP (Aβ precursor protein) including adjacent exon/ valine) and iCJD-2 was homozygous for methionine at the
intron boundaries. The PCR fragments were purified by polymorphic codon 129 of PRNP. Both cases carried only
agarose gel electrophoresis and sequenced using the Dye ε3 alleles (ε3/ε3) in the APOE gene.
Terminator cycle sequencing kit (Version 3.1; Applied Bio-
systems, Foster City, CA) with electrophoresis on an ABI Neuropathology of iCJD cases
3130 Genetic Analyzer (Applied Biosystems). To genotype
APOE, restriction fragment length polymorphism was used Histology of both iCJD cases revealed mild to moder-
as described previously [22]. In brief, a fragment within ate spongiform change associated with prominent gliosis
exon 4 of the APOE gene was amplified by PCR. Then the and neuronal loss and diffuse/synaptic immunoreactiv-
amplified 244 bp fragment was cut with restriction enzyme ity for disease-associated PrP (Fig. 1a–f). There were
HhaI. Restriction fragments were separated on a 16 % pol- no PrP plaques or kuru type plaques. The pattern was
yacrylamide gel and visualized. compatible with MV/MM type 1 [44]. Immunostaining
for Aβ revealed parenchymal plaques and CAA in both
cases (see below). Immunostaining for phosphorylated
Results tau (AT8) revealed occasional small neuritic profiles as
described in different forms of CJD [32, 47]. However,
Description of cases examined there was a complete lack of neurofibrillary tangles, pre-
tangles (including subcortical nuclei), neuropil threads,
Case iCJD-1 was a 33-year-old woman who had suffered or glial tau immunoreactivity. We did not observe any
a traumatic open right frontobasal skull fracture followed tau immunoreactive dystrophic neurites surrounding Aβ

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◂Fig. 1  Neuropathology of iCJD cases. Mild to moderate spongiform in both cases, showing also birefringence under polar-
change in the HE staining (a, d) associated with diffuse/synaptic PrP ized light in the Congo red staining (Fig. 1j, k). Only
immunoreactivity (b, e) and focal tau immunoreactive neuritic pro-
files (c, f indicated by arrows, a representative one is enlarged in right very rare mature plaques showed weakly stained argy-
upper inset) in case iCJD-1 (a–c) and iCJD-2 (d–f). The same mature rophilic neurites (Fig. 1l, m), which were however AT8
plaque with a corona in iCJD-2 as seen in immunostaining for Aβ (g), negative. Immunostaining for ubiquitin revealed neuritic
Bielschowsky (h), AT8 (i arrows indicate small neuritic profiles as profiles around some mature plaques (Fig. 1n, o). In the
seen in CJD cases but not around the mature plaque), HE (j arrow-
head) and Congo staining (k arrowhead indicates the plaque as seen white matter close to the area of the traumatic lesion
under polarized light). Bielschowsky staining (l, m) of two mature focal AβPP deposits were seen in both cases (Fig. 1p,
plaques lacking tau immunoreactivity close to each other in iCJD- q). In case iCJD-2 there was a mononuclear granuloma-
2. Immunostaining for Aβ (n) and ubiquitin (o) in the same cortical like inflammation in the area of the brain biopsy in the
regions close to the dura transplant in iCJD-1. Immunostaining for
AβPP in frontal white matter in iCJD-1 (p) and iCJD-2 (q). Immu- left frontal lobe together with ventriculitis and meningitis
nostaining for HLA-DR (microgliosis) in the frontal cortex (r) and with mononuclear inflammatory infiltrates, interpreted as
white matter (s) in iCJD-1. The bar in image “a” represents 100 μm inflammatory sequel of CSF leakage following the biopsy
for a–f, r, s; 40 μm for g–m; and 60 μm for n–q [46]. Microglial reaction, together with macrophages, was
most prominent in the cortex and white matter close to the
plaques although Bielschowsky silver staining did visual- lesion (Fig. 1r, s), while in other areas mostly the cortex
ize the mature and immature plaques, but mostly without showed moderate accumulation of ramified microglia. In
abundant argyrophilic neuritic components (Fig. 1g–i). iCJD-2 microgliosis was much more prominent due to the
In the HE staining we observed several amyloid cores recent inflammation.

Table 1  Anatomical Region/Aβ iCJD-1 iCJD-2

distribution of Aβ deposits in
the two cases of iatrogenic CAA Focal Diffuse Further CAA Focal Diffuse Further
Creutzfeldt-Jakob disease
(iCJD). Focal Aβ deposits are Mature Other Mature Other
stratified as mature (classic)
plaques and other (immature Frontobasal La − − + − − ++ ++ ++ + −
primitive plaques or compact Frontobasal Rb ++ +++ +++ − +++ + − + − +
plaques). Diffuse Aβ deposits Middle Fr L − + + − − ++ ++ ++ − −
include here only subpial
Middle Fr R + − + − − + − + − −
deposits. If there was no
difference between the two Middle-Upper Te L + + + − − + − ++ + −
sides (R: right, L: left) they are Middle-Upper Te R + + + − + + − + − −
summarized in one row. Further Inferior Pa R-L − − − − − + + + − −
Aβ deposition indicates lake-
Occ R-L + − − − − + − + − −
like immunoreactivity in the
lesion area, deposits in a venous Hippocampusc R-L − − − − − + − − − −
dilatation (temporal in iCJD-1) Basal GGl R-L − − − − − − − − − −
and amorphous deposits in the Thalamus R-L − − − − − − − − − −
dura
Mesencephalon − − − − − − − − − −
Pons − − − − − − − − − −
Medulla oblongata − − − − − − − − − −
Cerebellum − − − − − − − − − −
Dura graft + − − − + + − − − +
Dura hostd − − − − − − − − − −

R right, L left, Fr frontal, Te temporal, Pa parietal, Occ occipital, GGl Ganglia, − indicates negative, +,
++, +++ indicates positive (mild, moderate, severe, respectively)
a
Site of dural grafting in iCD-2
b
Site of dural grafting in iCD-1
c
Cornu ammonis, subiculum, entorhinal and inferior temporal cortex
d
Host dura was examined beside the grafted dura in iCJD-1 and more than 5 cm away from the operation
site in iCJD-2

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Distribution and morphology of dural and brain Aβ Fig. 2  Aβ immunoreactivity in iCJD-1. Immunostaining using the ▸
deposits in the iCJD cases 6F/3D Aβ antibody (a, b, f, g, i–m, p–s), the 4G8 Aβ antibody (c,
h), anti-Aβ1–40 (e, n), and anti-Aβ1–42 (d, o) demonstrated wide-
spread immunoreactivity in the lesion area (a upper part enlarged
Both cases showed similar morphology of Aβ immuno- in b–e); radiating deposits in the cortex (f) and white matter (g, h);
reactivities, characterized by CAA (type 2) [51] and pre- focal deposits with columnar alignment perpendicular to the sur-
dominantly focal cortical deposits, including cored mature face of the cortex (i–l); in a dilated vein (m), as immunostaining of
plaques (n, o); and as dural deposits (p–s). The right upper inset in
plaques, immature primitive plaques and focal cores p is the enlargement of the area indicated by an arrowhead; r and s
without a surrounding corona. Parenchymal Aβ deposits are enlargements of areas indicated by arrow and arrowhead in q,
accumulated closer to the area of the operation (Table 1), respectively. The bar in image “a” represents 150 μm for a, f, l, m–o;
appeared in clusters, and were seen mostly in the frontal 60 μm for b–e; 40 μm for g, h, j, k; 100 μm for i, p, q and 15 μm
for r, s
and temporal cortex. In iCJD-2 we observed mature and
primitive plaques and focal deposits in the anterior cin-
gulate gyrus on the lesion side; furthermore, occasional were seen only focally in the temporal lobe (Table 1), and
perivascular focal deposits in the occipital cortex and occa- these also showed mini-cores (Fig. 3c). Furthermore, cor-
sional plaques in the parietal cortex were also observed. tical Aβ deposition showed clustering of plaques, which
Accordingly, both cases were classified as phase 1 accord- were mostly focal deposits including mature and primitive
ing to Thal et al. [53], with the note that in iCJD-2 the plaques (Fig. 3d). In preserved cortical areas adjacent to the
involvement of the anterior cingulate suggested phase 2, lesion we recognized columns of Aβ deposits perpendicular
however, the complete lack of parenchymal Aβ deposits to the surface (Fig. 3d). Several samples of dura mater from
in the entorhinal cortex, hippocampus, and insular cortex the host (more than 5 cm from the operated area) lacked Aβ
deviated from the established phase 2. CAA was seen in deposition (Fig. 3e). In contrast, there was amorphous Aβ
neocortical areas but not in subcortical areas or cerebel- immunoreactivity in the grafted dura (Fig. 3f–i).
lum (stage 1) [52]. There was a lack of dyshoric angiopathy In summary, common features comprise (1) amorphous
or fibrinoid necrosis of vessels. In case iCJD-1 mostly the Aβ deposits in the grafted but not host dura mater; (2)
leptomeningeal vessels showed CAA, while in iCJD-2 the presence of parenchymal deposits (iCJD-1 > iCJD-2) and
cortical vasculature additionally exhibited prominent CAA. CAA (iCJD-2 > iCJD-1); (3) predominance of focal depos-
In case iCJD-1, the traumatic lesion area where the its (mature and immature plaques) and lack of ill-defined
graft was implanted showed prominent tissue damage. Aβ irregular diffuse plaques; (4) predominance of plaques
showed unusual lake-like appearance in the white matter in areas close to the traumatic lesion where the graft was
adjacent to the tissue defect, strongly labeled by Aβ1–40 implanted; (5) clustering of plaques in cortical areas with-
and Aβ1–42 as well (Fig. 2a–e). Aβ deposits radiated from out laminar preference or homogenous involvement of all
the lesion (Fig. 2f) and included linear and fine granular, layers; (6) tendency for columnar alignment of focal depos-
but not axonal bulb-like Aβ depositions in the perilesional its perpendicular to the surface in the vicinity of the lesion;
white matter (Fig. 2g, h) and at the gray-white matter junc- and (7) complete lack of neuronal or glial tau pathology
tion. In addition, in the adjacent cortical area, columns and particularly of plaque-associated tau-positive dys-
of Aβ deposits, oriented perpendicular to the brain sur- trophic neurites.
face, were noted (Fig. 2i–l). In further cortical areas, with
decreasing density away from the lesion (Table 1), either Morphology and frequency of dural Aβ deposits
single cores or clusters of plaques, both primitive and in the VITA cohort
mature, were seen. CAA involved mostly the meningeal
vessels including large venous dilatations (Fig. 2m) and the In the VITA cohort we observed typical morphology of
cortical arteries were less involved. The plaques and CAA CAA with congophilia in 11/84 cases (13.09 %; median
were observed using all anti-Aβ antibodies; Aβ1–40 showed age: 85 years, range 82–89); and amorphous deposits
mostly CAA and the cores of plaques, while Aβ1–42 immu- of Aβ in the connective tissue mostly adjacent to dural
nolabeled the corona of the plaques as well (Fig. 2n, o). sinuses in 11/84 cases (13.09 %; median age: 86 years,
The grafted dura mater also showed amorphous Aβ depo- range 84–88; only five of these cases with CAA also).
sitions including adjacent sinus-like dilatations (Fig. 2p–s). The age was not significantly different between groups
In case iCJD-2 we observed two focal deposits and a sin- showing or lacking Aβ immunoreactivity in the dura.
gle vessel with CAA already in the brain biopsy from the Both CAA and the amorphous deposits were detectable
frontal cortex. In the post mortem specimens the operated by the 4G8, 6F/3D, anti-Aβ 1–40, and anti-Aβ 1–42 anti-
area showed prominent inflammatory changes. In addition bodies (Fig. 4a–o, r, s). In the connective tissue, where
to CAA (Fig. 3a), we observed perivascular focal deposits, we observed amorphous Aβ immunoreactivity, collagen
including cored plaques (Fig. 3b). Subpial diffuse deposits IV decorated basement membranes (Fig. 4d, e inset).

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Combined presence of CAA and amorphous deposits brain or leptomeningeal vessels, vascular lesions in the
was seen only in five cases. Using enhanced protein- brain and Braak neurofibrillary stage. It is of note that
ase K treatment, both types of lesions were detectable cases with the presence of typical CAA detected by all
by both 4G8 and 6F/D3 anti-Aβ antibodies (Fig. 4c, antibodies in the examined dura samples showed Aβ
t); furthermore, focally they showed birefringence in deposits in the brain (100 %), while 8 (72.7 %) of them
Congo staining under polarized light (Fig. 4p, q). In showed also CAA in the examined brain samples. Simi-
addition, some vessels showed fine granular deposits larly, dural amorphous deposits were significantly asso-
without congophilia, detectable only by the 4G8 anti- ciated with Aβ deposits in the brain (100 %), and in 10
body in the media of arteries, in 41/84 cases (48.8 %; cases (90.9 %) there was also CAA in the brain and lep-
median age: 85 years, range 82–89). Detectability of tomeningeal vessels (p < 0.01 according to χ2 and Fisher
these morphologies using anti-Aβ antibodies did not exact test for both comparisons). In contrast, presence of
correlate with the duration of the formalin fixation of fine granular Aβ immunoreactivity detectable only with
samples. the 4G8 antibody in the media of large arteries did not
Next we compared the presence of the different mor- show correlation with any of these. Furthermore, none
phologies with neuropathological variables including the of the dural Aβ morphologies was associated with tau,
presence of Lewy body pathology, TDP-43 proteinopa- TDP-43, Lewy body, or vascular pathologies detected in
thy, tauopathy, parenchymal Aβ deposits or CAA in the the brain.

Fig. 3  Aβ immunoreactivity in iCJD-2. Immunostaining using the face of the cortex is labeled by a dashed line); lack of immunoreactiv-
6F/3D Aβ antibody (a–i) representing cerebral amyloid angiopathy ity in the host dura mater (e) and amorphous Aβ depositions in the
(a), perivascular cored plaque (b upper right inset is the enlarged graft dura mater (f–i; h and i is the enlargement of the areas indicated
image of the vessel below the letter “b”), single area with subpial by an arrow and arrowhead in g, respectively). The bar in image
deposits (c including minicored plaques indicated by an arrowhead “a” represents 150 μm for a; 40 μm for b, f; 100 μm for c, d, e, g;
and as enlarged in the right upper inset); columnar alignment of 15 μm for h, i
plaques in the cortex (d indicated by a row of arrowheads; the sur-

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Fig. 4  Aβ in the dura mater in the aging brain. Image a–m repre- immunostaining for Aβ1–40 (n), Aβ1–42 (o), Congo staining under
sents dura mater samples from a representative patient as visualized polarized light (p deposit in the connective tissue, q angiopathy), and
by 4G8 (a–c; in c using enhanced PK treatment of the sections), 6F/3D (r–t; areas indicated with asterisk enlarged in the right upper
6F/3D Aβ antibody (d–g; insets in d and e represent immunostaining inset; in t using enhanced PK-pretreatment). The bar in image “a”
for collagen IV; f and g are enlargements of the areas indicated by represents 20 μm for c, f, g, n, p, q, t; 40 μm for a, b, d, e, o, r, and
asterisk in d and e, respectively), Aβ1–40 (h, j), Aβ1–42 (i, k) and van s; and 80 μm for h–m
Gieson elastica (l, m). Further representative cases are shown using

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Discussion Αβ immunoreactivity frequently appears in certain forms

of genetic CJD (e.g. E200K mutation) even in younger

cognitive decline may have Αβ deposits in the neocortex

To contribute to the emerging issue of potential transmis- patients [19, 35]; furthermore, young individuals without
sibility of neurodegenerative conditions and related pro-
teins we re-evaluated two iCJD cases in which the grafted [45]. Importantly, these are also different from that seen
dura mater was available. In addition, we addressed the in the present iCJD cases, since they are predominated by
question whether Aβ can deposit in the dura mater in aged irregular diffuse plaques with ill-defined border lacking
individuals. amyloid cores. Moreover, in young individuals the pres-
ence of the ε4 allele of the APOE gene is significantly
Comparison of Aβ pathology with sporadic AD associated with the appearance of Aβ plaques [44]. Our
and TBI‑related neurodegeneration iCJD cases, representing the youngest cases where Aβ
deposits were observed in iCJD [18, 25], carried only ε3
In sporadic AD, deposits of Aβ are classified as diffuse, allele in the APOE gene; furthermore, there was a lack of
stellate and focal [14]. Diffuse deposits are poorly immu- pathogenic mutations in genes associated with altered Aβ
noreactive and their borders are ill-defined. Depending on metabolism (i.e. AβPP, PSEN1, PSEN2). It is important to
the localization they show lake-like or fleecy morphology emphasize that apart from the sparse small neuritic profiles
or they appear as subpial bands. Focal deposits are dif- detected in all prion disease types [32, 35, 47], we did not
ferent and they are further stratified whether they have a observe neuronal tau pathology in subcortical neuronal
neuritic corona or not [2, 14]. Importantly, a grading sys- groups [7, 8, 20, 50] or thread like profiles [33] as reported
tem was suggested for these lesions, beginning with purely in young individuals.
focal Aβ deposition, followed by appearance of Congo A possible explanation for the increased frequency of
red positive material with neurites and variable degree Aβ pathology in our iCJD cases might be simply the effect
of ubiquitination, which later show immunoreactivity for of brain trauma. Recent studies indicate that following
hyperphosphorylated tau, and finally associate with neu- repetitive injury CTE develops, which pathognomistically
rofibrillary tangles in the vicinity of plaques [42]. Impor- shows tau pathology [39], although Aβ deposition can be
tantly, diffuse Aβ deposits are considered as the earliest additionally seen [40, 41]. In our patients there was neither
form, while mature plaques can be seen later [14, 15]. repeated trauma documented nor were any clinical symp-
Another important aspect of Aβ pathology is the hierar- toms or tau pathologies compatible with CTE observed.
chical and stereotypical involvement of different brain Another form of neurodegeneration has been documented
regions, which follows five distinct phases [53]; the neo- in individuals many years after a single TBI, showing Aβ
cortex is involved in the first phase. Moreover, the study but also tau deposition [28]. We also observed chronic
by Cupidi et al. suggested considerable heterogeneity of lesions, such as accentuated microgliosis and macrophages
neocortical Aβ deposition in late phases of AD [12]. That and occasional axonal bulbs, which may persist years
study identified two patterns: a laminar intracortical pat- after TBI as described by Johnson and colleagues [26].
tern and another one where the six isocortical layers were In contrast, TBI cases were reportedly less likely to dis-
homogeneously involved [12]. Further studies showed that play smaller clustered regions of plaques and more likely
diffuse and focal deposits distinctly appear in different to have widespread plaques across the entire cortex [28].
layers of the cortex [13], which was not seen in our cases. Together with the lack of tau pathology in the iCJD cases
Indeed, the two iCJD cases examined here revealed a dis- examined, the distribution of plaques has to be emphasized:
tinct pattern. On one hand there was neither an unequivo- it showed higher density close to the dura mater graft.
cal laminar pattern nor homogenous involvement of corti- Interestingly, another study on TBI did not find Aβ plaques
cal layers even in regions with many mature and primitive in long-term survivors suggesting regression with time
plaques. Aβ deposition frequently appeared in clusters [11]. In short-term survivors of acute TBI mostly Aβ1–42
away from the lesion site or showed columnar alignment immunoreactivity was seen as non-neuritic plaques [23]. A
close to the lesion. On the other hand, the maturation pro- recent study using the amyloid tracer 11C-Pittsburgh com-
cess of plaques [42] was not recognizable; neither diffuse pound B to evaluate amyloid pathology in vivo in individu-
Aβ deposits with ill-defined borders, nor any tau immu- als with a history of TBI (11 months to 17 years) demon-
noreactivities in the corona of mature plaques were seen. strated a distinct involvement of the cerebellum [49] unlike
Thus, in spite of the presence of mature plaques, only in our patients. Importantly, the images showed no binding
grade 2 (out of 4 as proposed by Metsaars et al [42].) of in the vicinity of focal cortical lesions in TBI evident on
isocortical Alzheimer lesions could be recognized. There- structural MRI [49], which also contrasts with our iCJD
fore, we conclude that the Aβ deposition seen in our iCJD cases where most of the amyloid pathology was in cortical
cases is distinct from that seen in AD. It must be noted that regions close to the graft. Finally, ε4 carriers of the APOE

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Acta Neuropathol

gene have been discussed to be at increased risk for devel- predominantly affects CNS tissue and vessels in the CNS
oping Aβ pathology after TBI [27]. and leptomeninges [6]. Here we expand the spectrum of
Interestingly, CAA is less emphasized in TBI. Less than tissues showing Aβ deposition in cerebral Aβ amyloidosis
10 % frequency has been reported in individuals with TBI by demonstrating that the dura mater indeed accumulates
shortly after the injury, mostly associated with the presence pathological Aβ without selectivity for Aβ1–40 or Aβ1–42 in
of the APOE ε4 allele [36]. CAA was seen in the brain in the amorphous deposits. It has long been suggested that the
ex-boxers [54]. In sporadic CAA the pathogenesis includes dura mater is a metabolically inert, avascular, fibrous cov-
altered clearance or increased production of Aβ [52]. In the ering of the brain. However, the dura mater also contains
present iCJD cases CAA was observed only in the leptome- basal membranes [3], including in the abundant micro-
ninges and in the neocortex (stage 1). It might be theorized vascularization, which is not commensurate with the role
that the grafted dura containing Aβ deposits impaired the previously attributed to the dura mater [48]. Many studies
physiological clearance facilitated by additional seeding of have suggested that CAA is a protein elimination failure
Aβ to the vessels. Interestingly, perivascular Aβ deposits angiopathy where CAA reflects impaired perivascular lym-
frequently showed cores (Fig. 3b), which is unusual in AD. phatic drainage (for reviews see [5, 10, 57]). Until recently,
In summary, the pathology seen in the two iCJD cases however, the lymphatic system of the dura mater received
was distinct not only from AD brains but also from that less attention. Early studies already emphasized that the
described in long-term survivors of TBI or in CTE. The lymphatic system might play a role in the fluid circulation
observation of Aβ deposits in the grafted but not in the host of the brain [17, 30]. Interestingly, recent studies confirmed
dura mater suggests a scenario of seeding of the pathologi- that a lymphatic system lining the dural sinuses drains the
cal protein to the underlying CNS. However, the Aβ seeds brain interstitial fluid [4, 38], which might have relevance
alone seem to be inefficient in reproducing the complete to understand our observation of the accumulation of amor-
clinicopathological phenotype of AD. Lack of the clini- phous Aβ deposits in the vicinity of dural sinuses in a
cal phenotype of AD has been emphasized in recipients of cohort of elderly individuals.
cadaveric human growth hormone [24]. This contrasts with
prion diseases, where the seeding of disease-associated PrP
leads to widespread involvement of the brain together with Conclusions
the entire phenotype.
We provide novel observations complementing a recent
Dural Aβ pathology in the aging brain study on the increased frequency of Aβ pathology in iCJD
associated with dura mater transplantation [18]. The pat-
Next we addressed the question how frequently and in what tern of Aβ deposition together with the lack of accompa-
form does Aβ pathology involve the dura mater in aging. In nying tau pathology differentiates the Aβ proteinopathy in
spite the small size of the dura sample examined (4 cm2) iCJD from sporadic and genetic forms of AD; from that
we were able to detect deposits associated with AD type seen in young individuals without cognitive decline carry-
pathology in the CNS. CAA and amorphous deposits were ing one or two APOE4 alleles; from that in young genetic
labeled by all antibodies even following harsh PK-pretreat- CJD patients with mutation in the PRNP gene; and from
ment of sections and showed birefringence in Congo red that related to TBI and CTE. Additionally, the presence
staining using polarized light. These morphologies were of Aβ in the grafted but not the host dura mater suggests
similar to that seen in the grafted dura samples in iCJD that we observe here an example of ‘infectious propagon’
cases. The fine granular immunoreactivity detectable only [15]. Infectious propagons have been defined as “proteins
with antibody 4G8 in the media of vessels showed no spe- that transmit pathological conformation between individu-
cific correlation with neuropathological variables and was als” [15]. However, of significance is the lack of clinical
not interpreted as CAA, in particular since antibody 4G8 symptoms reminiscent of AD and of the full neuropatho-
also detects intracellular AβPP [1]. logical picture of AD, which contrast with the phenotype-
It was suggested that amyloid proteins have a ubiqui- reproducing property of prions in prion diseases. In fact,
tous affinity to basement membranes [6] as demonstrated we demonstrate here that pathological Aβ protein, rather
for dura-related Aβ deposits in our study and also by than AD, can be propagated between humans. Therefore,
Keable and colleagues [29]. Indeed, amyloid deposits in we propose to distinguish Aβ as an ‘infectious propagon’
the dura mater (pachymeninx), but not in the leptomenin- (when only the pathological conformation is transmit-
ges, have been shown in cases with generalized (systemic) ted between individuals) from disease-associated PrP as a
amyloidosis, which on the other hand involve CNS tis- ‘phenotype propagon’ (when the pathological conformation
sue usually only in regions where the blood brain barrier of the protein and the full clinicopathological phenotype is
is not sufficient [6]. In contrast, cerebral Aβ amyloidosis transmitted between individuals; e.g. prion disease). This

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 Acta Neuropathol

concept would also help to better understand reports on angiopathies (PEFA) in neurodegenerative disease with a focus
horizontal transmission of other amyloids like the AA amy- on therapy. Neuropathol Appl Neurobiol 39:593–611
11. Chen XH, Johnson VE, Uryu K, Trojanowski JQ, Smith DH
loid in captive cheetahs [43]. In addition, our observations (2009) A lack of amyloid beta plaques despite persistent accu-
in a cohort of elderly individuals show that the dura mater mulation of amyloid beta in axons of long-term survivors of trau-
does not infrequently harbor Aβ, especially in the vicin- matic brain injury. Brain Pathol 19:214–223
ity of sinuses, which provides an important aspect to the 12. Cupidi C, Capobianco R, Goffredo D et al (2010) Neocortical
variation of Abeta load in fully expressed, pure Alzheimer’s dis-
understanding of the drainage of this protein from the CNS. ease. J Alzheimers Dis 19:57–68
13. Delaere P, Duyckaerts C, He Y, Piette F, Hauw JJ (1991) Sub-
Acknowledgments Open access funding provided by Medical Uni- types and differential laminar distributions of beta A4 deposits in
versity of Vienna. The Vienna Trans-Danube Ageing (VITA) study Alzheimer’s disease: relationship with the intellectual status of
was supported and organized by the Ludwig Boltzmann Institute of 26 cases. Acta Neuropathol 81:328–335
Ageing Research. The neuropathology study was supported by the 14. Duyckaerts C, Delatour B, Potier MC (2009) Classification
European Commission’s 7th Framework Programme under GA No and basic pathology of Alzheimer disease. Acta Neuropathol
278486, “DEVELAGE”. The Austrian Reference Centre for Human 118:5–36
Prion Diseases is supported by the Federal Ministry of Health, 15. Eisele YS, Duyckaerts C (2016) Propagation of Aβ pathol-
Austria. ogy: hypotheses, discoveries, and yet unresolved questions
from experimental and human brain studies. Acta Neuropathol
Compliance with ethical standards 131:5–25
16. Fischer P, Jungwirth S, Krampla W, et al. (2002) Vienna Trans-
Conflict of interest Authors report no conflict of interest. danube Aging “VITA”: study design, recruitment strategies and
level of participation. J Neural Transm Suppl 62:105–116
Open Access This article is distributed under the terms of the 17. Földi M, Csanda E, Simon M et al (1968) Lymphogenic haeman-
Creative Commons Attribution 4.0 International License (http://crea- giopathy. “Prelymphatic” pathways in the wall of cerebral and
tivecommons.org/licenses/by/4.0/), which permits unrestricted use, cervical blood vessels. Angiologica 5:250–262
distribution, and reproduction in any medium, provided you give 18. Frontzek K, Lutz MI, Aguzzi A, Kovacs GG, Budka H (2016)
appropriate credit to the original author(s) and the source, provide a Amyloid-beta pathology and cerebral amyloid angiopathy are
link to the Creative Commons license, and indicate if changes were frequent in iatrogenic Creutzfeldt-Jakob disease after dural graft-
made. ing. Swiss Med Wkly 146:w14287
19. Ghoshal N, Cali I, Perrin RJ et al (2009) Codistribution of
amyloid beta plaques and spongiform degeneration in famil-
ial Creutzfeldt-Jakob disease with the E200K-129M haplotype.
Arch Neurol 66:1240–1246
References 20. Grinberg LT, Rub U, Ferretti RE et al (2009) The dorsal raphe
nucleus shows phospho-tau neurofibrillary changes before the
1. Aho L, Pikkarainen M, Hiltunen M, Leinonen V, Alafuzoff I transentorhinal region in Alzheimer’s disease. A precocious
(2010) Immunohistochemical visualization of amyloid-beta pro- onset? Neuropathol Appl Neurobiol 35:406–416
tein precursor and amyloid-beta in extra- and intracellular com- 21. Guo JL, Lee VM (2014) Cell-to-cell transmission of pathogenic
partments in the human brain. J Alzheimers Dis 20:1015–1028 proteins in neurodegenerative diseases. Nat Med 20:130–138
2. Alafuzoff I, Thal DR, Arzberger T et al (2009) Assessment of 22. Hixson JE, Vernier DT (1990) Restriction isotyping of human
beta-amyloid deposits in human brain: a study of the BrainNet apolipoprotein E by gene amplification and cleavage with HhaI.
Europe Consortium. Acta Neuropathol 117:309–320 J Lipid Res 31:545–548
3. Andres KH (1967) On the fine structure of the arachnoidea and 23. Horsburgh K, Cole GM, Yang F et al (2000) beta-amyloid
dura mater of mammals. Z Zellforsch Mikrosk Anat 79:272–295 (Abeta)42(43), abeta42, abeta40 and apoE immunostaining
4. Aspelund A, Antila S, Proulx ST et al (2015) A dural lymphatic of plaques in fatal head injury. Neuropathol Appl Neurobiol
vascular system that drains brain interstitial fluid and macromol- 26:124–132
ecules. J Exp Med 212:991–999 24. Irwin DJ, Abrams JY, Schonberger LB et al (2013) Evaluation of
5. Attems J, Jellinger K, Thal DR, Van Nostrand W (2011) Review: potential infectivity of Alzheimer and Parkinson disease proteins
sporadic cerebral amyloid angiopathy. Neuropathol Appl Neuro- in recipients of cadaver-derived human growth hormone. JAMA
biol 37:75–93 Neurol 70:462–468
6. Bohl J, Storkel S, Steinmetz H (1989) Involvement of the central 25. Jaunmuktane Z, Mead S, Ellis M et al (2015) Evidence for
nervous system and its coverings in different forms of amyloido- human transmission of amyloid-beta pathology and cerebral
sis. Prog Clin Biol Res 317:1007–1019 amyloid angiopathy. Nature 525:247–250
7. Braak H, Del Tredici K (2011) The pathological process under- 26. Johnson VE, Stewart JE, Begbie FD, Trojanowski JQ, Smith
lying Alzheimer’s disease in individuals under thirty. Acta Neu- DH, Stewart W (2013) Inflammation and white matter degenera-
ropathol 121:171–181 tion persist for years after a single traumatic brain injury. Brain
8. Braak H, Del Tredici K (2015) The preclinical phase of the path- 136:28–42
ological process underlying sporadic Alzheimer’s disease. Brain 27. Johnson VE, Stewart W, Smith DH (2010) Traumatic brain injury
138:2814–2833 and amyloid-beta pathology: a link to Alzheimer’s disease? Nat
9. Brettschneider J, Del Tredici K, Lee VM, Trojanowski JQ (2015) Rev Neurosci 11:361–370
Spreading of pathology in neurodegenerative diseases: a focus 28. Johnson VE, Stewart W, Smith DH (2012) Widespread tau and
on human studies. Nat Rev Neurosci 16:109–120 amyloid-beta pathology many years after a single traumatic brain
10. Carare RO, Hawkes CA, Jeffrey M, Kalaria RN, Weller RO injury in humans. Brain Pathol 22:142–149
(2013) Review: cerebral amyloid angiopathy, prion angiopa- 29. Keable A, Fenna K, Yuen HM et al (2015) Deposition of amyloid
thy, CADASIL and the spectrum of protein elimination failure beta in the walls of human leptomeningeal arteries in relation to

13
Acta Neuropathol

perivascular drainage pathways in cerebral amyloid angiopathy. 44. Parchi P, de Boni L, Saverioni D et al (2012) Consensus clas-
Biochim Biophys Acta. doi:10.1016/j.bbadis.2015.08.024: sification of human prion disease histotypes allows reliable
30. Kida S, Pantazis A, Weller RO (1993) CSF drains directly from identification of molecular subtypes: an inter-rater study among
the subarachnoid space into nasal lymphatics in the rat. Anat- surveillance centres in Europe and USA. Acta Neuropathol
omy, histology and immunological significance. Neuropathol 124:517–529
Appl Neurobiol 19:480–488 45. Pletnikova O, Rudow GL, Hyde TM et al (2015) Alzheimer
31. Kovacs GG (2016) Molecular pathological classification of neu- lesions in the autopsied brains of people 30 to 50 years of age.
rodegenerative diseases: turning towards precision medicine. Int Cogn Behav Neurol 28:144–152
J Mol Sci 17:189. doi:10.3390/ijms17020189 46. Preusser M, Ströbel T, Gelpi E et al (2006) Alzheimer-type neu-
32. Kovacs GG, Budka H (2013) The spectrum of tau pathology in ropathology in a 28 year old patient with iatrogenic Creutzfeldt-
human prion disease. In: Zou W-Q, Gambetti P (eds) Prions and Jakob disease after dural grafting. J Neurol Neurosurg Psychiatry
diseases. Springer, New York, pp 103–119 77:413–416
33. Kovacs GG, Horvath MC, Majtenyi K, Lutz MI, Hurd YL, Kel- 47. Reiniger L, Lukic A, Linehan J et al (2011) Tau, prions and
ler E (2015) Heroin abuse exaggerates age-related deposition of Abeta: the triad of neurodegeneration. Acta Neuropathol
hyperphosphorylated tau and p62-positive inclusions. Neurobiol 121:5–20
Aging 36:3100–3107 48. Roland J, Bernard C, Bracard S et al (1987) Microvasculariza-
34. Kovacs GG, Milenkovic I, Wohrer A et al (2013) Non-Alzheimer tion of the intracranial dura mater. Surg Radiol Anat 9:43–49
neurodegenerative pathologies and their combinations are more 49. Scott G, Ramlackhansingh AF, Edison P et al (2016) Amyloid
frequent than commonly believed in the elderly brain: a commu- pathology and axonal injury after brain trauma. Neurology
nity-based autopsy series. Acta Neuropathol 126:365–384 86:821–828
35. Kovacs GG, Seguin J, Quadrio I et al (2011) Genetic Creutzfeldt- 50. Stratmann K, Heinsen H, Korf HW et al (2015) Precortical phase
Jakob disease associated with the E200K mutation: characteriza- of Alzheimer’s disease (AD)-related tau cytoskeletal pathology.
tion of a complex proteinopathy. Acta Neuropathol 121:39–57 Brain Pathol. doi:10.1111/bpa.12289:
36. Leclercq PD, Murray LS, Smith C, Graham DI, Nicoll JA, Gen- 51. Thal DR, Ghebremedhin E, Rub U, Yamaguchi H, Del Tredici K,
tleman SM (2005) Cerebral amyloid angiopathy in traumatic Braak H (2002) Two types of sporadic cerebral amyloid angiopa-
brain injury: association with apolipoprotein E genotype. J Neu- thy. J Neuropathol Exp Neurol 61:282–293
rol Neurosurg Psychiatry 76:229–233 52. Thal DR, Griffin WS, de Vos RA, Ghebremedhin E (2008) Cer-
37. Lewis J, Dickson DW (2016) Propagation of tau pathology: ebral amyloid angiopathy and its relationship to Alzheimer’s dis-
hypotheses, discoveries, and yet unresolved questions from ease. Acta Neuropathol 115:599–609
experimental and human brain studies. Acta Neuropathol 53. Thal DR, Rub U, Orantes M, Braak H (2002) Phases of A beta-
131:27–48 deposition in the human brain and its relevance for the develop-
38. Louveau A, Smirnov I, Keyes TJ et al (2015) Structural and ment of AD. Neurology 58:1791–1800
functional features of central nervous system lymphatic vessels. 54. Tokuda T, Ikeda S, Yanagisawa N, Ihara Y, Glenner GG (1991)
Nature 523:337–341 Re-examination of ex-boxers’ brains using immunohistochemis-
39. McKee AC, Cairns NJ, Dickson DW et al (2016) The first try with antibodies to amyloid beta-protein and tau protein. Acta
NINDS/NIBIB consensus meeting to define neuropathological Neuropathol 82:280–285
criteria for the diagnosis of chronic traumatic encephalopathy. 55. Uchihara T, Giasson BI (2016) Propagation of alpha-synuclein
Acta Neuropathol 131:75–86 pathology: hypotheses, discoveries, and yet unresolved questions
40. McKee AC, Stein TD, Kiernan PT, Alvarez VE (2015) The neu- from experimental and human brain studies. Acta Neuropathol
ropathology of chronic traumatic encephalopathy. Brain Pathol 131:49–73
25:350–364 56. Uchihara T, Giasson BI, Paulus W (2016) Propagation of Abeta,
41. McKee AC, Stern RA, Nowinski CJ et al (2013) The spectrum of tau and alpha-synuclein pathology between experimental models
disease in chronic traumatic encephalopathy. Brain 136:43–64 and human reality: prions, propagons and propaganda. Acta Neu-
42. Metsaars WP, Hauw JJ, van Welsem ME, Duyckaerts C (2003) A ropathol 131:1–3
grading system of Alzheimer disease lesions in neocortical areas. 57. Weller RO, Subash M, Preston SD, Mazanti I, Carare RO (2008)
Neurobiol Aging 24:563–572 Perivascular drainage of amyloid-beta peptides from the brain
43. Murakami T, Ishiguro N, Higuchi K (2014) Transmission of sys- and its failure in cerebral amyloid angiopathy and Alzheimer’s
temic AA amyloidosis in animals. Vet Pathol 51:363–371 disease. Brain Pathol 18:253–266

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