Download PHENOTYPIC CHANGES IN IRRADIATED ENDOTHELIAL CELLS

PHENOTYPIC CHANGES IN IRRADIATED ENDOTHELIAL CELLS:
IMPLICATION OF THE ENDOTHELIAL TO MESENCHYMAL
TRANSITION IN THE DEVELOPMENT OF HEALTHY DIGESTIVE
TISSUE INJURY FOLLOWING RADIATION EXPOSURE
Elodie Minteta, Valérie Buarda, Jean-Christophe Sabourinb, Marc Benderittera, Fabien
Milliata and Agnès Françoisa
a Radiobiology and Radiopathology Research Laboratory, Institute for Radiological
Protection and Nuclear Safety, Fontenay-aux-Roses, France.
b Department of Pathology, Rouen University Hospital, France
Corresponding author’s email: [email protected]
The exposure of the abdomino-pelvic region to ionizing radiation is associated
with untoward healthy digestive tissue injury. Radiation fibrosis is characterized by
an excessive and uncontrolled synthesis of extracellular matrix by mesenchymal cells.
The endothelial to mesenchymal transition (EndoMT) is a process in which
endothelial cells transdifferentiate into mesenchymal cells in response to stress.
EndoMT was recently described as a possible source of mesenchymal cells
contributing to fibrosis in injured heart, lung, and kidney, in a preclinical model of
gastrointestinal inflammation, and in patients with ulcerative colitis and Crohn’s
disease. The aim of this study was to determine the role of the EndoMT during the
development of radio-induced intestinal fibrosis.
Radiation-induced EndoMT was studied in vitro by analyzing the gene and
protein expression profiles of irradiated human umbilical vein and intestinal
microvascular endothelial cells (HUVEC and HIMEC) for different doses and times
after irradiation.
The induction of EndoMT was studied in vivo by using a model of transgenic
mice expressing the green fluorescent protein (GFP) under the control of an
endothelial specific promoter, Tie2. The Tie2-GFP mice received a single dose
(27Gy) focalized on the colorectal region. A co-immunostaining of alpha-smooth
muscle actin (α-SMA) and green fluorescent protein (GFP) was performed to identify
mesenchymal cells having an endothelial origin.
Irradiation induced the EndoMT process in HUVEC and HIMEC by
increasing mesenchymal markers such as α-SMA and decreasing endothelial markers
such as von Willebrand Factor (vWF), 7 days after 10Gy exposure. We also
visualized an up-regulation at both gene and protein levels of the transcription factor
Hey2, already known to take part in non-radio-induced EndoMT. Moreover, colocalization of α-SMA and vWF suggesting radiation-induced EndoMT was observed
in mucosal and submucosal vessels of human rectum 6 weeks following radiation
therapy for rectal adenocarcinoma. Finally, EndoMT process exists in our mouse
model of radiation proctitis 7 and 14 days after irradiation.
In conclusion, this is the first report of EndoMT as a putative participant to
radiation-induced gut damage in vivo, and further studies will try to determine the role
of Hey2 in the radio-induced EndoMT process in vitro and in vivo.