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COMPARISON OF DAMAGE FROM INTERNAL ALPHA IRRADIATION TO THE HEMOPOIETIC AND STROMAL SYSTEM IN ADULT AND PRE- AND POST- NATAL ANIMALS

Objective

THIS STUDY AIMS AT ELUCIDATING THE EARLY EFFECTS ON STROMAL AND HEMOPOIETIC STEM CELLS AFTER CONTAMINATION WITH ALPHA EMITTING BONE-SEEKERS WITH RESPECT TO BONE TUMOR INDUCTION AND OTHER BONE MALIGNANCIES IN MICE. SPECIAL ATTENTION WILL BE PAID TO THE FIBROBLAST-LIKE AND HEMOPOIETIC CELLS IN 1)ADULT BONE MARROW AND 2)FOETAL AND NEONATAL BONE MARROW, LIVER AND SPLEEN.
WE SHALL STUDY THE FIBROBLAST-LIKE CELLS QUALITATIVELY WITH RESPECT TO THEIR FUNCTION IN OSTEOGENESIS AND HEMATOPOIESIS.
MARROW STROMAL CELLS APPEAR TO BE MORE RADIOSENSITIVE THAN HITHERTO THOUGHT. RADIATION COULD INDUCE A SPECTRUM OF QUALITATIVELY DIFFERENT ALTERATIONS IN THESE CELLS DEPENDING ON THE DOSE. WITH SMALL DOSES THE STROMA COULD SUSTAIN REVERSIBLE DAMAGE WHICH COULD AFFECT SOME CELLULAR FUNCTIONS. THIS DAMAGE MAY NORMALLY GO UNDETECTED. WHEN THE PROLIFERATIVE ACTIVITY OF THESE NORMALLY QUIESCENT CELLS IS CALLED INTO ACTION, THEIR SENSITIVITY TO RADIATION INCREASES. THIS CAN HAVE IMPORTANT CONSEQUENCES IN THE GROWING FOETUS. BY CONTRAST, LARGER DOSES COULD LEAD TO CELL DEATH OR PRODUCE OTHER TYPES OF DAMAGE THAT COULD NOT READILY BE REPAIRED.
The results indicated that the age of animals at exposure determined the radiation induced effects. A supplementary intake of americium-241 via lactation seemed important. Using the LTC culture system, damage was observed at lower radiation doses if americium contamination occured at the foetal rather than at the adult stage. These observations are important for risk estimation during pregnancy and for neonates.
A. THE INVESTIGATION OF THE RADIOSENSITIVITY OF ADULT BONE MARROW FIBROBLASTS AFTER CONTAMINATION OF MICE WITH VARIOUS DOSES OF AM-241 IS BASED ON QUALITATIVE CHANGES IN THE CFU-F POPULATION.
BONE MARROW FIBROBLASTS HAVE BEEN IMPLICATED AS AN INTEGRAL PART OF THE HEMATOPOIETIC MICROENVIRONMENT WHICH IS RESPONSIBLE FOR THE IN VIVO REGULATION (GROWTH AND DIFFERENTIATION) OF ADULT GRANULOPOIESIS EITHER THROUGH CELL-CELL INTERACTIONS AND/OR THE PRODUCTION OF GROWTH PROMOTING FACTORS. DIFFERENT IN VITRO TECHNIQUES ARE AVAILABLE TO STUDY THIS INTERACTION.
ECTOPIC BONE MARROW TRANSPLANTATION (UNDER RENAL CAPSULE AND SUBCUTANEOUS) WILL BE USED TO STUDY THE OSTEOGENIC AND HEMOPOIETIC POTENTION OF THE STROMAL CELLS. IMPLANTATION RESULTS IN THE INDUCTION OF A DEFINED, TEMPORAL SEQUENCE OF CHANGES WHICH STARTS WITH BONE-FORMATION AND IS FOLLOWED BY A COMPLETE RECONSTRUCTION OF THE HEMOPOIETIC MICROENVIRONMENT. THIS SYSTEM IS A PROTOTYPE FOR THE STUDY OF THE ROLE OF EXTRACELLULAR MATRIX PRODUCED BY STROMAL CELLS AND IT IS A USEFUL EXPERIMENTAL MODEL FOR STUDIES ON REGULATION OF HEMATOPOIESIS.
ATTENTION WILL BE PAID TO THE BIOSYNTHETIC CAPABILITIES OF THE BONE MARROW FIBROBLASTS IN VITRO, TO CHECK CHANGES IN THEIR PRODUCTION OF EXTRACELLULAR MATRIX COMPONENTS. THESE ARE IMPORTANT
1) FOR THE ADHESION AND SPREADING OF THE FIBROBLASTS WHICH IS REQUIRED TO ALLOW CELLS TO PROLIFERATE AND
2) BY THEIR ROLE IN THE INTERACTION BETWEEN STROMAL ELEMENTS AND HEMATOPOIETIC CELLS. THESE COMPONENTS INCLUDE COLLAGEN AND RETICULUM FIBERS, FIBRONECTIN AND GLYCOSAMINOGLYCANS.
B. THE STUDY IN FOETAL AND NEONATAL MOUSE AIMS AT THE DETECTION OF RADIATION EFFECTS AFTER SHORT AND LONGER PERIODS OF INTERNAL ALPHARADIOCONTAMINATION.
THREE ASPECTS ARE CONSIDERED:
- CHARACTERISATION OF THE RADIOSENSITIVE AND RADIORESISTANT CELL POPULATIONS IN LIVER, SPLEEN AND BONE MARROW AT DIFFERENT GESTATIONAL AGES. HEMOPOIETIC (PLURIPOTENT STEM CELLS OR CFU-S AND GRANULOCYTE-MACROPHAGE PROGENITORS OR CFU-C) AND STROMAL (CFU-F) CELL CLONING ASSAYS WILL BE USED TO IDENTIFY THE QUANTITATIVE CELLULAR RESPONSE. THE PERCENTAGE OF CFU-S, CFU-C AND CFU-F IN S-PHASE WILL BE SIMULTANEOUSLY INVESTIGATED.
- COMPARISON OF QUALITATIVE CHANGES INDUCED BY IN VIVO ALPHA IRRADIATION IN THE STROMAL CELLS IN FOETAL LIVER, SPLEEN AND BONE MARROW WITH THOSE OBTAINED IN ADULT MICE. STROMAL CELLS WILL BE TESTED FOR THEIR CAPACITY IN VITRO TO SUPPORT HEMOPOIESIS IN LONG-TERM MARROW CULTURES AND WILL BE TESTED FOR THEIR OSTEOGENIC AND REGENERATIVE POTENTIAL BY ECTOPIC TRANSPLANTATION.
- SPATIAL AND TEMPORAL DISTRIBUTION OF DOSE (BIOLOGICAL DOSIMETRY) WILL BE PERFORMED AND CORRELATED WITH THE BEHAVIOUR OF THE EXPOSED TARGET CELLS TO CHECK WHETHER IN VITRO HEMOPOIETIC AND STROMAL CELL CLONING ASSAYS MAY BE USED AS BIOLOGICAL INDICATORS OF RADIATION HARM TO THE BLOOD FORMATION AND INJURY TO BONE FORMATION DUE TO INTERNAL ALPHA-EMITTERS.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

CENTRE D'ETUDES DE L'ENERGIE NUCLEAIRE
Address
Parc Seny Rue Charles Lemaire 1
1160 Brussels
Belgium