Ionising radiation can induce toxic effects on body. They provoke physiological modifications of tissues and organs which can be lethal. Total body irradiation or local abdominal irradiation can induce serious complications. Intestine is the first tissue concerned by these side effects. Radiation induces malabsorption of the intestine and lost of it integrity. Radio-induced physiopatological effects on intestine could lead to distant effects on other tissues and organs such as liver.
The actual treatments have a limited efficiency or are not adapted to gastrointestinal damages. Indeed, in this type of lesions, the heterogeneous systems which are concerned and the gravity of lesions complicates the medical care.
Our purpose is to show that cell therapy using human mesenchymal stem cells (MSC) constitutes resolution in this type of illness. The works which are presented in this thesis show that MSC are multipotent and have heterogeneous expression of molecules. These cells are able to establish themself in many organs and tissues after injection into irradiated body. Thus we have shown that MSC can prevent the small intestine from radio-induced damages. Indeed we demonstrate that through their actions on gut, MSC can indirectly restore hepatic integrity.