Abstract
Radiotherapy is a widely used treatment for various malignant and non-malignant disorders, but can lead to side effects such as radiation-induced cystitis. While the role of mast cells in the pathophysiology of radiation-induced toxicities has been highlighted in current research, the prognostic value of mast cells in the presentation of radiation-induced cystitis remains unclear. Consequently, this thesis aims to examine mast cells in the urinary bladder and their response to radiation exposure. This will involve a systematic review of myeloid-lineage leukocytes in radiation-induced cystitis, the determination of mast cell prevalence and distribution in healthy, non-irradiated urinary bladders, as well as the exploration of potential alterations in mast cell prevalence and distribution following exposure to myeloablative radiation.A systematic review was first conducted to investigate the potential prognostic value of myeloid-lineage leukocytes in the pathophysiology of radiation-induced cystitis. The systematic review revealed seven unique articles for data extraction. The findings of these determined that myeloid-lineage leukocytes do not offer substantive prognostic value in preclinical rodent models, and that continued research is necessary to investigate the myeloablative aetiology of radiation-induced cystitis.
Following this systematic review, the prevalence and distribution of mast cells in the healthy murine urinary bladder of C57BL/6J mice were investigated to establish a baseline for later comparison with myeloablative radiation exposure. Mast cell prevalence in female C57BL/6Jmice was determined using flow cytometry, whereas mast cell distribution was assessed using the metachromatic stain toluidine blue. This study found that mast cells comprise less than 4%of all live leukocytes in the urinary bladder and are more prominent in the lamina propria and detrusor muscle layers. Additionally, one-fifth of the identified mast cells were located near vasculature, which may be relevant to their function and contribution to bladder pathologies.
After establishing baseline values for mast cell prevalence and distribution, the effects of myeloablative radiation on urinary bladder mast cells were examined. C57BL/6J mice were exposed to 9.5Gy total body irradiation to induce myeloablation. Using flow cytometry and toluidine blue histological staining, mast cell prevalence, distribution and morphology were assessed. The findings of this study revealed that mast cell frequency increased in relation to the broader leukocyte populations one week after irradiation, but did not differ between nonirradiated and irradiated bladders four weeks following irradiation. Mast cell density per layer of the urinary bladder wall remained unchanged, except for the adventitia, which showed a significant increase four weeks after radiation exposure. Mast cell diameter also differed between non-irradiated and irradiated bladders four weeks following radiation.
In conclusion, this thesis provides insight into the effects of myeloablative radiation on the immune environment in the urinary bladder. Collectively, these findings indicate that there is much work to be done to fully understand the roles of myeloid-lineage leukocytes in the pathophysiology and prognosis of radiation-induced cystitis, with particular regard to mast cells. These findings contribute to the understanding of the pathophysiology of radiation induced cystitis and may inform future therapeutic methods for lower urinary tract dysfunction associated with radiation-induced toxicities.
| Date of Award | 17 Jun 2024 |
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| Original language | English |
| Supervisor | Christian Moro (Supervisor), Jonathan Tan (Supervisor) & Helen O'Neill (Supervisor) |