Background:
Between 2005 and 2015 the number of new cancer cases per year in Canada rose by 29% and this number is projected to increase to 277,000 cases per year. Ionizing radiation is used as therapy in the majority of cancer cases; however, it can have long-term detrimental effects on the hematopoietic system. Recent work from our lab, in a preclinical model of radiation damage, demonstrated that endurance exercise training can enhance hematopoietic recovery, while obesity can impair it. Extracellular vesicles (EVs) are a mode of cellular communication that has been implicated in regulating hematopoiesis acutely following radiation exposure. However, the long-term, radiation-induced changes to EVs, and the role of exercise and/or obesity at modulating marrow EVs remains unknown. Thus, the purpose of this project was to determine the extent to which obesity and exercise influence the regenerative potential of bone marrow-EVs following radiation.
Method:
Mice were randomly divided into control (n=20; CON) or high fat diet (n=20; HF) groups, then subdivided into exercise-trained (EX, n=10) or sedentary (SED, n=10). Mice underwent whole-body exposure to a 3 Gy dose of gamma-radiation at age 13 weeks of age followed by bone marrow collection at 20 weeks of age. EVs were then isolated from the bone marrow by ExoQuick and ultracentrifugation. A non-irradiated, sedentary, control diet group (n=10) was used to determine the effects of radiation alone. Data was evaluated using repeated-measures three-factor (diet, exercise, time) and two-factor ANOVA.
Results:
High fat diet-induced changes in body weight and composition and altered food consumption (p<0.05). Isolated EVs measured between 78 and 195 nm and western blot confirmed the presence of EV protein markers Alix, TSG101, and Flotillin. No size difference was observed between the groups. The concentration of EVs in irradiated mice was significantly lower compared to EVs from control mice (p<0.01). Radiation, obesity, exercise, or their combination had no significant effect on hematopoietic stem progenitor cells (HSPC) content in co-culture assays. Conversely, EVs from irradiated mice significantly increased the number of CFU-GEMM, CFU-G, and the TOTAL number of colonies compared to EVs from non-irradiated mice (p<0.01). However, EVs from the CON+SED, CON+EX, HF+SED, and HF+EX groups did not have a significant effect on colony formation.
Conclusion:
Our findings demonstrate that ionizing radiation can diminish the concentration of bone marrow-EVs and that irradiated bone marrow-EVs can increase the total number of myeloid colonies formed in vitro. These results suggest that radiation induces myelopoiesis via a mechanism that includes EVs; however, exercise and obesity induce their effects via a different mechanism.
| Identifer | oai:union.ndltd.org:uottawa.ca/oai:ruor.uottawa.ca:10393/40472 |
| Date | 07 May 2020 |
| Creators | Ngu, Matthew |
| Contributors | De Lisio, Michael |
| Publisher | Université d'Ottawa / University of Ottawa |
| Source Sets | Université d’Ottawa |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
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