Exposure to ionizing radiations and starvation culture does not modify phenotype, functions and genetic profile of mesenchymal stromal cells isolated from bone marrow of healthy donors

Abstract

Mesenchymal stromal cells (MSCs) are multipotent cells located in different human tissues, including bone marrow (BM), where they sustain the creation of the hematopoietic stem cell niche by regulating its differentiation and functions. Many studies have demonstrated that BM exposure to ionizing radiations induces the rapid depletion of hematopoietic precursors, however radiation effects on MSCs have been poorly investigated. Moreover, little is known about MSCs behavior in starvation culture conditions. In this study, we examined morphology, proliferative capacity (in terms of population doublings), immunophenotype, differentiation potential, immunomodulatory properties (PHA-induced T cell proliferation assay) and genetic profile (array-CGH and caryotype) of MSCs isolated from BM of healthy donors and exposed to ionizing radiations and starvation culture. MSCs were isolated from 10 healthy donors (median age: 16 years; range: 5-32) and expanded in culture medium supplemented with 5% platelet lysate up to passage 2. Thereafter MSCs were exposed both to escalating doses of ionizing radiations (3000, 10000 and 20000 rad) and to starvation culture conditions (culture medium supplemented with 1% platelet lysate instead of 5%). With escalating doses of ionizing radiations, MSCs lose their typical spindle-shaped morphology, their boundaries are less regular and their growth rate slows down (at 3000 rad) or even stops (at 10000 and 20000 rad). Nonetheless, in the presence of 1% platelet lysate, although showing a slower growth rate as compared with non irradiated MSCs, the effects on morphology are less evident, thus suggesting that the lack of growing factors can slow down the senescent process induced by ionizing radiations. Furthermore, irradiated and starved MSCs maintain the same immunophenotype, differentiation potential, immunomodulatory properties and genetic profile of normal MSCs. Our data indicate that irradiated and starved MSCs, although presenting altered morphology and growth rate, maintain the typical characteristics of normal MSCs.