Understanding Molecular Mechanisms and Identifying Key Processes in Chronic Radiation Cystitis

The effect of myeloablative radiation on urinary bladder mast cells

Radiation-induced cystitis is an inflammatory condition affecting the urinary bladder, which can develop as a side effect of abdominopelvic radiotherapy, specifically external-beam radiation therapy or myeloablative radiotherapy. A possible involvement of mast cells in the pathophysiology of radiation-induced cystitis has been indicated in cases of external-beam radiation therapy; however, there is no evidence that these findings apply to the myeloablative aetiology. As such, this study investigated potential changes to urinary bladder mast cell prevalence when exposed to myeloablative radiation. Lethally irradiated C57BL/6J mice that received donor rescue bone marrow cells exhibited an increased mast cell frequency amongst host leukocytes 1 week following irradiation. By 4 weeks, no significant difference in either frequency or cell density was observed. However mast cell diameter was smaller, and a significant increase in mast cell number in the adventitia was observed. This study highlights that mast cells constitute a significant portion of the remaining host leukocyte population following radiation exposure, with changes to mast cell distribution and decreased cell diameter four weeks following radiation-induced injury.

The effects of radiation on myeloid lineage immune cells within the rodent urinary bladder: a systematic review

PURPOSE

Radiotherapy is a prominent therapy for many malignant and non-malignant disorders, though it can cause side effects such as radiation-induced cystitis. Current research has highlighted a role for mast cells and macrophages in the prognosis of such radiation-induced toxicities. However, the prognostic value of these immune cells in the pathophysiology of radiation-induced cystitis is not clear. As such, a systematic review was conducted to assess myeloid-lineage immune cells for their prognostic value in radiation-induced cystitis to address this gap in literature.

METHODS

The protocol was registered in PROSPERO, and searches were performed in PubMed, Embase and Web of Science databases for pre-clinical rodent studies on radiation-induced cystitis.

RESULTS

After de-duplication, 153 articles were screened for relevancy by title and abstract. Title and abstract screening deemed 64 studies irrelevant. The remaining 85 studies were full-text screened, yielding seven unique articles for data extraction. Most included studies had an unclear risk of bias. The findings of this systematic review suggest that the prognostic value of myeloid-lineage immune cells in radiation-induced cystitis is still unclear, indicating a need for further research in this field.

CONCLUSION

Although the studies reviewed provide some insight into the role of these immune cells in disease pathology, the limited number of studies and unclear risk of bias further highlights a need for additional, high-quality research in this area. In summary, this systematic review highlights a need to understand the involvement of immune cells in radiation-induced cystitis pathophysiology and lay the groundwork for further research in this area.

TRIAL REGISTRATION

PROSPERO registration: CRD42022345960.

Maintaining Serum Hemoglobin Levels Within the Physiological Range Prevented Bladder Tamponade Recurrence Due to Radiation-Induced Hemorrhagic Cystitis: A Case Report

Radiation-induced hemorrhagic cystitis is a refractory disease that can cause severe hematuria and bladder tamponade. Bladder tamponade due to radiation-induced hemorrhagic cystitis can often recur repeatedly and markedly reduce the quality of life. However, no blood test parameter has been studied yet regarding the prevention of bladder tamponade recurrence. An 84-year-old patient with a history of radiation therapy for cervical cancer was repeatedly hospitalized for bladder tamponade due to radiation-induced hemorrhagic cystitis. At each hospitalization, blood transfusions were performed to treat severe anemia as the first treatment, resulting in hematuria improvement, and the patient was discharged without invasive treatments such as transurethral coagulation. However, anemia developed gradually after each discharge. The anemia progression was obviously unrelated to macrohematuria because macrohematuria did not appear during that period. When the serum hemoglobin level decreased below the physiological range, bladder tamponade recurred. Based on these findings, we posited that the monitoring of the serum hemoglobin level could be useful to predict the occurrence of bladder tamponade. We hypothesized that if the serum hemoglobin level did not fall below the physiological range, bladder tamponade would not occur. We treated chronic anemia after determining its cause and kept serum hemoglobin levels within the physiological range. Since the treatment was initiated, bladder tamponade has not recurred in over 27 months. In this case, the monitoring of the serum hemoglobin level was useful to predict the occurrence of bladder tamponade due to radiation-induced hemorrhagic cystitis. By maintaining serum hemoglobin levels within the physiological range, we successfully prevented the recurrence of bladder tamponade due to radiation-induced hemorrhagic cystitis.

Advances in the management of radiation-induced cystitis in patients with pelvic malignancies

OBJECTIVE

Radiotherapy plays a vital role as a treatment for malignant pelvic tumors, in which the bladder represents a significant organ at risk involved during tumor radiotherapy. Exposing the bladder wall to high doses of ionizing radiation is unavoidable and will lead to radiation cystitis (RC) because of its central position in the pelvic cavity. Radiation cystitis will result in several complications (e.g. frequent micturition, urgent urination, and nocturia) that can significantly reduce the patient's quality of life and in very severe cases become life-threatening.

METHODS

Existing studies on the pathophysiology, prevention, and management of radiation-induced cystitis from January 1990 to December 2021 were reviewed. PubMed was used as the main search engine. Besides the reviewed studies, citations to those studies were also included.

RESULTS AND DISCUSSIONS

In this review, the symptoms of radiation cystitis and the mainstream grading scales employed in clinical situations are presented. Next, preclinical and clinical research on preventing and treating radiation cystitis are summarized, and an overview of currently available prevention and treatment strategies as guidelines for clinicians is provided. Treatment options involve symptomatic treatment, vascular interventional therapy, surgery, hyperbaric oxygen therapy (HBOT), bladder irrigation, and electrocoagulation. Prevention includes filling up the bladder to remove it from the radiation field and delivering radiation based on helical tomotherapy and CT-guided 3D intracavitary brachytherapy techniques.

Mesenchymal stem cells limit vascular and epithelial damage and restore the impermeability of the urothelium in chronic radiation cystitis

BACKGROUND

Cellular therapy seems to be an innovative therapeutic alternative for which mesenchymal stem cells (MSCs) have been shown to be effective for interstitial and hemorrhagic cystitis. However, the action of MSCs on chronic radiation cystitis (CRC) remains to be demonstrated. The aim of this study was to set up a rat model of CRC and to evaluate the efficacy of MSCs and their mode of action.

METHODS

CRC was induced by single-dose localized irradiation of the whole bladder using two beams guided by tomography in female Sprague-Dawley rat. A dose range of 20-80 Gy with follow-up 3-12 months after irradiation was used to characterize the dose effect and the kinetics of radiation cystitis in rats. For the treatment, the dose of 40 Gy was retained, and in order to potentiate the effect of the MSCs, MSCs were isolated from adipose tissue. After expansion, they were injected intravenously during the pre-chronic phase. Three injections of 5 million MSCs were administered every fortnight. Follow-up was performed for 12 months after irradiation.

RESULTS

We observed that the intensity and frequency of hematuria are proportional to the irradiation dose, with a threshold at 40 Gy and the appearance of bleeding from 100 days post-irradiation. The MSCs reduced vascular damage as well as damage to the bladder epithelium.

CONCLUSIONS

These results are in favor of MSCs acting to limit progression of the chronic phase of radiation cystitis. MSC treatment may afford real hope for all patients suffering from chronic radiation cystitis resistant to conventional treatments.