Cytohistologycal and immunohistochemical characteristics of the aortic intima and media in coarctation of the aorta - adult type
Authors: Vukovic Irena , Lackovic Vesna , Todorovic Vera , Kanjuh Vladimir , Ilic Slobodan 
Published: May 2015

INTRODUCTION. Classically, coarctation of the aorta has been divided into
infantile and adult forms. The vascular malformation responsible for
coarctation is a defect of the vessel intima and media giving rise to a
prominent posterior infolding (?the posterior shelf?) which, in some cases,
may extend around the entire circumference of the aorta. Histological
examination of the coarcted aortic segment discloses intimal and medial
lesion consisting of thickened ridges that protrude posteriorly into the
aortic lumen. Intimal proliferation and disruption of elastic tissue may
occur in adult type. OBJECTIVE. The smooth muscle cells phenotype in the
aortic intimal thickening, presence of inflammatory cells and contents of the
intimal and medial pseudocysts were investigated. MATERIAL AND METHODS. The
samples of coarctation segments excised at surgery from 10 patients aged from
2 to 13 years were examined. For light microscopy, the specimens were
dehydrated in graded ethanol (70-100%), cleared in xylol and embedded in
paraffin. Sections of 5 ?m thick were cut on Leica SM 2000R and Leica
Reinhart Austria microtome and stained with orcein and Alcian blue-PAS at pH
1.0 and pH 2.5. Immunocytochemical staining was performed on 5 ?m sections
from formaldehyde-fixed paraffin-embedded blocks, using a labeled
streptavidin-biotin method with an LSkit (Dako). Sections were
deparaffinized and rehydrated. After microwave treatment of 21 minutes in
citrate buffer pH 6.0, endogenous peroxidase activity was blocked with 3%
H2O2 for 15 minutes. The sections were first incubated with the primary
antibody for 60 minutes (?-smooth muscle actin-?-SMA, vimentin, desmin,
myosin haevy chains-MHC, CD3, CD45, S-100 and Proliferating Cell Nuclear
Antigen-PCNA), then with biotinylated link antibody and finally with
peroxidase-labeled streptavidin. Slides were counterstained with hematoxylin,
washed in water and mounted. For electron microscopy, the primary fixative
consisted of 2.5% glutaraldehyde in 0.1 M sodium cacodylate-HCl buffer (pH
7.4) for 24 h at 4?C. The specimens were postfixed for 1 h at 4?C in 1%
osmium tetroxide in 0.1 M cacodylate buffer and 4.8% uranyl acetate for 24 h
at 4?C. The samples were dehydrated in graded ethanol (70-100%) and embedded
in Epon 812. The samples were cut with a diamond knife on an LKB Ultratome.
Ultra-thin sections were stained with 2% uranyl acetate and alkaline lead
citrate. RESULTS. All samples had focal intimal thickening on the posterior
aortic wall, with accumulation of mucins which were stained with Alcian
blue-PAS on pH 1.0, followed by prominent hypocellularity. Rare smooth muscle
cells (SMC) showed immunoreactivity on ?-SMA and vimentin, but not on desmin,
MHC or CD3 and CD45. A large number of cells in apoptosis was noticed in the
inner media on the posterior wall. On the anteromedial wall, a large number
of PCNA- and S-100- positive cells was noted in the inner media while one
layer of MHC- and desmin- positive cells was noted in the outer media. The
elastic lamellae were focally disrupted by pools which were stained with
Alcian blue-PAS at pH 1.0. DISCUSSION. In all examined samples, the
immunocytochemical and TEM results revealed the presence of dedifferentiated
smooth muscle cells which express ?-SMA and vimentin, with a lack of
expression of desmin and MHC. Results of this study also showed the reduction
of cell number in the intima and media, followed by apoptotic smooth muscle
cells in the inner media of the posterior wall and the absence of
inflammatory cells. Such finding suggests that apoptosis but not necrosis may
be the mechanism of reduction of cell number. The presence of smooth muscle
cell proliferation in the inner media of the anteromedial wall and one layer
of differentiated SMC in the outer part may lead us to suppose that changes
of media (including dedifferentiation of the cells and disruption of elastic
tissue) appear from inner to outer part and from posterior to anteromedial
wall. The presence of pseudocysts which are stained with Alcian blue-PAS at
pH 1.0 show large amount of mucins in elastic fibers. CONCLUSION. The intimal
thickening on the posterior aortic wall is composed of small number of
dedifferentiated smooth muscle cells (SMC). Some of these cells are in
apoptosis. On the anteromedial wall, the intima and media are composed of
proliferated SMC and small number of SMC which exhibit contractile phenotype.
In all parts of the aortic wall, there is a large number of pseudocysts with
large amount of mucins, without presence of inflammatory cells.