Early and long-term effects of radiation on intercellular adhesion molecule 1 (ICAM-1) expression in mouse urinary bladder endothelium

Modeling normal bladder injury after radiation therapy

PURPOSE

For decades, Dr. John Moulder has been a leading radiation biologist and one of the few who consistently supported the study of normal tissue responses to radiation. His meticulous modeling and collaborations across the field have offered a prime example of how research can be taken from the bench to the bedside and back, with the ultimate goal of providing benefit to patients. Much of the focus of John's work was on mitigating damage to the kidney, whether as the result of accidental or deliberate clinical exposures. Following in his footsteps, we offer here a brief overview of work conducted in the field of radiation-induced bladder injury. We then describe our own preclinical experimental studies which originated as a response to reports from a clinical genome-wide association study (GWAS) investigating genomic biomarkers of normal tissue toxicity in prostate cancer patients treated with radiotherapy. In particular, we discuss the use of Renin-Angiotensin System (RAS) inhibitors as modulators of injury, agents championed by the Moulder group, and how RAS inhibitors are associated with a reduction in some measures of toxicity. Using a murine model, along with precise CT-image guided irradiation of the bladder using single and fractionated dosing regimens, we have been able to demonstrate radiation-induced functional injury to the bladder and mitigation of this functional damage by an inhibitor of angiotensin-converting enzyme targeting the RAS, an experimental approach akin to that used by the Moulder group. We consider our scientific trajectory as a bedside-to-bench approach because the observation was made clinically and investigated in a preclinical model; this experimental approach aligns with the exemplary career of Dr. John Moulder.

CONCLUSIONS

Despite the differences in functional endpoints, recent findings indicate a commonality between bladder late effects and the work in kidney pioneered by Dr. John Moulder. We offer evidence that targeting the RAS pathway may provide a targetable pathway to reducing late bladder toxicity.

Pre-clinical Research on Bladder Toxicity After Radiotherapy for Pelvic Cancers: State-of-the Art and Challenges

Despite the dramatic advancements in pelvic radiotherapy, urinary toxicity remains a significant side-effect. The assessment of clinico-dosimetric predictors of radiation cystitis (RC) based on clinical data has improved substantially over the last decade; however, a thorough understanding of the physiopathogenetic mechanisms underlying the onset of RC, with its variegated acute and late urinary symptoms, is still largely lacking, and data from pre-clinical research is still limited. The aim of this review is to provide an overview of the main open issues and, ideally, to help investigators in orienting future research. First, anatomy and physiology of bladder, as well as the current knowledge of dose and dose-volume effects in humans, are briefly summarized. Subsequently, pre-clinical radiobiology aspects of RC are discussed. The findings suggest that pre-clinical research on RC in animal models is a lively field of research with growing interest in the development of new radioprotective agents. The availability of new high precision micro-irradiators and the rapid advances in small animal imaging might lead to big improvement into this field. In particular, studies focusing on the definition of dose and fractionation are warranted, especially considering the growing interest in hypo-fractionation and ablative therapies for prostate cancer treatment. Moreover, improvement in radiotherapy plans optimization by selectively reducing radiation dose to more radiosensitive substructures close to the bladder would be of paramount importance. Finally, thanks to new pre-clinical imaging platforms, reliable and reproducible methods to assess the severity of RC in animal models are expected to be developed.

A non-invasive ultrasound imaging method to measure acute radiation-induced bladder wall thickening in rats

Background

Methods for the non-invasive quantification of changes in bladder wall thickness as potential predictors of radiation cystitis in pre-clinical research would be desirable. The use of ultrasound for this aim seems promising, but is still relatively unexplored. A method using ultrasound for bladder wall thickness quantification in rats was developed and applied to measure early radiation-induced bladder wall thickness changes.

Methods

Two groups (n = 9 each) of female Fischer rats were treated with a single radiation dose of 25–30 and 35–40 Gy respectively, using an image-guided micro-irradiator; six untreated rats were monitored as a control group. Empty, half-filled and fully-filled bladder volumes were determined for four non-irradiated rats by measuring axes from ultrasound 3D-images and applying the ellipsoid formula. Mean bladder wall thickness was estimated for both ventral and dorsal bladder sides through the measurement of the bladder wall area along a segment of 4 mm in the central sagittal scan, in order to minimize operator-dependence on the measurement position. Ultrasound acquisitions of all fully-filled rat bladders were also acquired immediately before, and 4 and 28 days after irradiation. Mean bladder wall thickness normalized to the baseline value and corrected for filling were then used to evaluate acute bladder wall thickening and to quantify the dose–effect.

Results

The relationship between mean bladder wall thickness and volume in unirradiated rats showed that for a bladder volume > 1.5 mL the bladder wall thickness is almost constant and equal to 0.30 mm with variations within ± 15%. The average ratios between post and pre irradiation showed a dose–effect relationship. Bladder wall thickening was observed for the 25–30 Gy and 35–40 Gy groups in 2/9 (22%) and 5/9 (56%) cases at day 4 and in 4/9 (44%) and 8/9 (89%) cases at day 28, respectively. The two groups showed significantly different bladder wall thickness both relative to the control group (p < 0.0001) and between them (p = 0.022). The bladder wall thickness increment was on average 1.32 ± 0.41, and was 1.30 ± 0.21 after 25–30 Gy and 1.47 ± 0.29 and 1.90 ± 0.83 after 35–40 Gy at days 4 and 28 respectively.

Conclusions

The feasibility of using ultrasound on a preclinical rat model to detect bladder wall thickness changes after bladder irradiation was demonstrated, and a clear dose–effect relationship was quantified. Although preliminary, these results are promising in addressing the potential role of this non-invasive approach in quantifying radiation cystitis.

An evaluation of the effect of bortezomib on radiation-induced urinary bladder dysfunction

PURPOSE

The urinary bladder is one major organ at risk in radiotherapy of pelvic malignancies. The radiation response manifests in early and chronic changes in bladder function. These are based on inflammatory effects and changes in urothelial cell function and proliferation. This study evaluates the effect of bortezomib as an anti-proliferative and anti-inflammatory compound in an established mouse bladder model. The early radiation-induced bladder dysfunction in the mouse occurs in two phases during the first month after irradiation (phase I: day 0-15, phase II: days 16-30).

MATERIALS AND METHODS

Daily bortezomib injections (0.02 mg/ml, subcutaneously) were administered between days 0-15 or 15-30 in separate groups. Single graded radiation doses were administered in five dose groups. Cystometry was carried out before (individual control) and during the first month after irradiation. When bladder capacity was decreased by ≥50%, mice were considered as responders. Statistical analysis was performed by the SPSS software version 24.

RESULTS

Daily bortezomib injections between days 0-15 resulted in a significant decrease in responders for phase I. There was no significant effect with daily bortezomib injections between days 16-30.

CONCLUSION

Two separate waves of acute radiation-induced urinary bladder dysfunction have distinct mechanisms that need further biological studies.

Evaluation of the Effects of Prostate Radiation Therapy on Occludin Expression and Ultrasonography Characteristics of the Bladder

PURPOSE

To evaluate the effects of radiation dose in prostate radiation therapy (RT) on occludin expression and ultrasonography characteristics of the bladder.

METHODS AND MATERIALS

Urine samples of 64 prostate RT patients were collected before, at regular intervals during, and 3 months after RT. Occludin expression analysis was performed, and bladder wall echogenicity and echotexture were investigated by ultrasound and the gray-scale histogram analysis method. The bladder equivalent uniform dose (EUD) was derived from individually produced dose treatment plan for each patient. Clinical scoring for bladder-specific symptoms was done using the Radiation Therapy Oncology Group Acute Radiation Morbidity Scoring Criteria Scale.

RESULTS

Thirty patients (47%) experienced at least 1 of the studied bladder symptoms (grade ≥1 endpoints), including urinary pain, frequency, urgency, straining, incontinence, hematuria, dysuria, and nocturia. For these patients there were significant changes in urine occludin levels after starting the treatment compared with the baseline urine samples (P=.023). The mean bladder EUD that caused a significant change in occludin level, which occurred after the 15th RT session, was 26.9 Gy (range, 13.2-36.5 Gy, P=.020). In all patients a significant reduction in bladder echogenicity (P=.0137) and a significant change in its echotexture (P=.047) was found after the 10th RT session, after which the EUD to the bladder reached 17.9 Gy (range, 8.8-24.3 Gy).

CONCLUSIONS

Significant changes in occludin expression level and bladder wall echogenicity and echotexture occurred during prostate RT. Our findings suggest that a significant reduction in bladder echogenicity and increase in occludin expression during treatment can be associated with acute urinary complications.

Can filling phase urodynamic parameters predict the success of the bulbar artificial urinary sphincter in treating post-prostatectomy incontinence?

OBJECTIVE

To evaluate whether filling phase urodynamic parameters can predict the success of the artificial urinary sphincter (AUS) in treating post-prostatectomy incontinence (PPI).

MATERIALS AND METHODS

We reviewed the pre-AUS urodynamics of 99 patients with PPI at two tertiary referral centers. We documented the peak DO pressure (P_det ), capacity, and compliance (C). We defined success as patient-reported continence or only using one safety pad. Patients' perception of improvement was assessed using the PGI-I score.

RESULTS

Sixty-eight percent (n = 68) of patients had a successful outcome. The mean compliance for the "success" and "failure" group was 112.3 mL/cmH₂ O (±119.7) and 34.1 mL/cmH₂ O (±36.2), respectively. Fifty-five percent (17/31) of patients in the "failure" group demonstrated DO(P_det  = 36.2 ± 18.2 cmH₂ O) compared to 18% (12/68) in the success group. The differences between the two groups in P_det and compliance were statistically significant (all P < 0.01). There was, however, no statistical difference between the mean cystometric capacities of patients in the two outcome groups. Thirteen out of 18 (72%) patients who had radiotherapy had a poor outcome ("success" group only 15% [9/59]). These results were used to develop a nomogram for the probability of AUS success. A good inverse correlation (r = -0.65) was demonstrated between the probability of AUS success as deduced from the nomogram and PGI-I score post-AUS implantation CONCLUSION: Compliance and P_det are predictors of outcome following AUS implantation for PPI. We have developed and internally validated a nomogram that may be used to determine an individualized likelihood of AUS success. This nomogram may be used as a counseling tool to objectively set realistic expectations of continence post-AUS implantation.

Basic Fibroblast Growth Factor Ameliorates Endothelial Dysfunction in Radiation-Induced Bladder Injury

This study was designed to explore the effect of basic fibroblast growth factor (bFGF) on radiation-induced endothelial dysfunction and histological changes in the urinary bladder. bFGF was administrated to human umbilical vein cells (HUVEC) or urinary bladder immediately after radiation. Reduced expression of thrombomodulin (TM) was indicated in the HUVEC and urinary bladder after treatment with radiation. Decreased apoptosis was observed in HUVEC treated with bFGF. Administration of bFGF increased the expression of TM in HUVEC medium, as well as in the urinary bladder at the early and delayed phases of radiation-induced bladder injury (RIBI). At the early phase, injection of bFGF increased the thickness of urothelium and reduced inflammation within the urinary bladder. At the delayed phase, bFGF was effective in reducing fibrosis within the urinary bladder. Our results indicate that endothelial dysfunction is a prominent feature of RIBI. Administration of bFGF can ameliorate radiation-induced endothelial dysfunction in urinary bladder and preserve bladder histology at early and delayed phases of RIBI.

Assessment of the effect of local application of amifostine on acute radiation-induced oral mucositis in guinea pigs

The aim of present study was to assess the radioprotective effects of the local application of amifostine to treat acute buccal mucositis in guinea pigs. A total of 32 guinea pigs were randomized into four groups: (Group A) topically administered 50 mg of amifostine plus radiotherapy (RT); (Group B) 100 mg amifostine plus RT; (Group C) normal saline plus RT; and (Group D) normal saline plus sham RT. The opportunity for administration was 15 min before irradiation. When administered, the cotton pieces that had been soaked with 0.5 ml amifostine solution or saline were applied gently on the buccal mucosa of each guinea pig for 30 min. The animals in Groups A, B and C were irradiated individually with a single dose of 30 Gy to the bilateral buccal mucosa. Eight days after irradiation, the animals were scored macroscopically; they were then euthanized, and the buccal mucosal tissues were processed for hematoxylin-eosin staining and ICAM-1 immunohistochemical analysis. In Groups A and B, the mean macroscopic scores were 2.9 ± 0.6 and 2.4 ± 1.1, respectively. There was no significant difference between the two groups (P > 0.05). However, when they were separately compared with Group C (4.4 ± 0.7), a noticeable difference was obtained (P < 0.05). No mucositis was observed in Group D. Comparisons of the expression of ICAM-1 were in agreement with the macroscopic data. Histologically, superficial erosion, exudate and ulcer formation were all observed in the RT groups; only the severity and extent were different. The microscopic observations in the amifostine-treated groups were better than in Group C. The results demonstrated that topical administration of amifostine to the oral mucosa is effective treatment of acute radiation-induced mucositis.

Late effects of local irradiation on the expression of inflammatory markers in the Arteria saphena of C57BL/6 wild-type and ApoE-knockout mice

Combined action of irradiation (IR), shear stress, and high blood pressure is well recognized to induce damage to vasculature, while data on pathological effects of IR in large peripheral vessels with low blood pressure are scarce. The purpose of the present study was hence to investigate time- and dose-dependent effects of local IR on inflammatory and prothrombotic processes in the Arteria (A.) saphena of C57BL/6 wild-type and apolipoprotein E (ApoE)-knockout mice. Single doses of 2, 5, 8, 10, or 16 Gy were locally delivered to the A. saphena of the left leg of the animals. The expression of CD31, intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), E-selectin, monocyte chemoattractant protein-1 (MCP-1), and thrombomodulin (TM) was quantified by semiautomatic TissueFax fluorescence analysis in frozen arterial sections. Follow-up periods were 3, 6, 9, 12, or 18 months. Protein expression in the arterial wall displayed dose-dependent changes. Proinflammatory reactions were observed for CD31, E-selectin, ICAM, and VCAM already at doses of 2 Gy. Anti-inflammatory changes were detected for MCP-1 and TM. The effects were more pronounced in wild-type versus ApoE(-/-) mice. Changes remain mostly transient up to 16 Gy. Dose- and time-dependent changes in inflammatory and thrombotic mediators in the wall of the A. saphena were found after local IR but did not transform into histopathological consequences.

ICRP publication 118: ICRP statement on tissue reactions and early and late effects of radiation in normal tissues and organs--threshold doses for tissue reactions in a radiation protection context

This report provides a review of early and late effects of radiation in normal tissues and organs with respect to radiation protection. It was instigated following a recommendation in Publication 103 (ICRP, 2007), and it provides updated estimates of 'practical' threshold doses for tissue injury defined at the level of 1% incidence. Estimates are given for morbidity and mortality endpoints in all organ systems following acute, fractionated, or chronic exposure. The organ systems comprise the haematopoietic, immune, reproductive, circulatory, respiratory, musculoskeletal, endocrine, and nervous systems; the digestive and urinary tracts; the skin; and the eye. Particular attention is paid to circulatory disease and cataracts because of recent evidence of higher incidences of injury than expected after lower doses; hence, threshold doses appear to be lower than previously considered. This is largely because of the increasing incidences with increasing times after exposure. In the context of protection, it is the threshold doses for very long follow-up times that are the most relevant for workers and the public; for example, the atomic bomb survivors with 40-50years of follow-up. Radiotherapy data generally apply for shorter follow-up times because of competing causes of death in cancer patients, and hence the risks of radiation-induced circulatory disease at those earlier times are lower. A variety of biological response modifiers have been used to help reduce late reactions in many tissues. These include antioxidants, radical scavengers, inhibitors of apoptosis, anti-inflammatory drugs, angiotensin-converting enzyme inhibitors, growth factors, and cytokines. In many cases, these give dose modification factors of 1.1-1.2, and in a few cases 1.5-2, indicating the potential for increasing threshold doses in known exposure cases. In contrast, there are agents that enhance radiation responses, notably other cytotoxic agents such as antimetabolites, alkylating agents, anti-angiogenic drugs, and antibiotics, as well as genetic and comorbidity factors. Most tissues show a sparing effect of dose fractionation, so that total doses for a given endpoint are higher if the dose is fractionated rather than when given as a single dose. However, for reactions manifesting very late after low total doses, particularly for cataracts and circulatory disease, it appears that the rate of dose delivery does not modify the low incidence. This implies that the injury in these cases and at these low dose levels is caused by single-hit irreparable-type events. For these two tissues, a threshold dose of 0.5Gy is proposed herein for practical purposes, irrespective of the rate of dose delivery, and future studies may elucidate this judgement further.

Radiation effects on cellularity, proliferation and EGFR expression in mouse bladder urothelium

This study was designed to determine changes in cell numbers, proliferation (using Ki-67) and EGFR expression in mouse bladder urothelium during the early and late radiation response. Groups of mice were irradiated with a single dose of 20 Gy and assayed 0-360 days later. Urothelial cells were counted. After immunohistochemistry, the absolute and relative numbers of Ki-67(+) and EGFR(+) cells were analyzed. Radiation exposure resulted in a decrease in total urothelial cell numbers to 49% by day 31, with restoration of cellularity by day 180. In contrast, at day 360, an increase in total cell number (143%) was seen. Slightly increased Ki-67 expression was found at days 120 and 180 after treatment, followed by a pronounced elevation at days 240 and 360. Compared to controls, higher EGFR expression was detected up to day 360 after irradiation. A positive correlation was found between total urothelial cells numbers and Ki-67 as well as EGFR expression. Radiation exposure results in an increased urothelial expression of EGFR that precedes urothelial restoration, indicating a contribution of the EGF/EGFR system to urothelial proliferation and differentiation. Further studies are needed to evaluate the impact of EGFR inhibition on radiation effects in the urinary bladder.

Effect of recombinant human keratinocyte growth factor (rHuKGF, Palifermin) on radiation-induced mouse urinary bladder dysfunction

PURPOSE

To determine the effect of Palifermin (rHuKGF) on acute and late radiation effects in mouse urinary bladder.

METHODS AND MATERIALS

Graded radiation doses were applied on day 0. Single subcutaneous injections of Palifermin (15 mg/kg) were given on day -2 or day +2. Changes in bladder function (i.e., a reduction in bladder volume by >or=50% of the individual preirradiation value) were assessed by cystometry.

RESULTS

Early changes in mouse bladder after irradiation occur in two phases. In the first early phase, a single injection of Palifermin on day -2 increased the ED(50) (dose associated with a positive bladder response in 50% of the mice) from 20.0 +/- 3.3 Gy to 27.1 +/- 6.9 Gy (p < .0051). Palifermin given on day +2 was not beneficial. No significant effects of Palifermin were seen in the second early phase. However, Palifermin administration before, but not after, irradiation, also modified late radiation effects, with an ED50 of 22.2 +/- 4.8 Gy compared with 16.2 +/- 4.9 Gy in control animals (p < .0187).

CONCLUSIONS

Initial early functional changes in the mouse urinary bladder after irradiation as well as late effects can be significantly reduced by a single administration of Palifermin before irradiation.

Radiation Induced Late Damage to the Barrier Function of Small Blood Vessels in Mouse Bladder

PURPOSE

We identified changes in vascular barrier function in relation to collagen deposition during the late radiation response of mouse bladders. In this study albumin leakage was assessed as a marker of blood vessel barrier disruption.

MATERIALS AND METHODS

Female C3H/Neu mice were irradiated with a single dose of 20 Gy and sacrificed for (immuno) histological studies after 90, 120, 180, 240 and 360 days. The fractional area of subepithelial tissue with extravascular albumin signal was defined. Moreover, the amount of collagen was determined after Masson's trichrome staining on an arbitrary score of 0 to 3.

RESULTS

Subepithelial albumin infiltration due to leakage from the blood vessels was seen in irradiated animals during the entire late phase. It was most pronounced at days 120 and 180 after treatment (vs control p <0.0001). Similarly an increase in collagen deposition in the bladder wall was seen during the whole late radiation phase but with increasing values toward the end of the experiment (day 360 vs control p <0.0001).

CONCLUSIONS

Irradiation of the bladder results in late damage to the barrier function of small subepithelial blood vessels, causing pronounced albumin leakage at the early steps of the chronic radiation reaction, clearly preceding excessive collagen deposition in the bladder wall. Current data suggest a vascular component in the development of late radiation induced changes in the bladder.

Radiation-induced damage to mouse urothelial barrier

PURPOSE

To determine changes of the urothelial barrier during the early as well as late radiation response in mouse urinary bladder.

MATERIALS AND METHODS

Groups of mice were irradiated with a single dose of 20Gy and sacrificed between days 0 and 360. Urothelial cell numbers were counted, and the fraction of urothelium with a positive immunohistochemical signal for uroplakin-III (UP-III) on the luminal surface of the bladder was defined. Also, cytoplasmic UP-III staining signal in urothelium was quantified using an arbitrary score (0-3).

RESULTS

Irradiation resulted in a significant decrease in the number of superficial umbrella cells during the early response phase (days 0-31) as well as during the initial late radiation reaction (days 90, 120). Progressive loss of the UP-III layer on the bladder luminal surface correlated with the decrease in the number of umbrella cells (p=0.002). Also, increased cytoplasmic staining of UP-III in the urothelium was seen after irradiation, correlating negatively with the reduction of the superficial UP-III layer (p<0.0001).

CONCLUSION

Irradiation of the urinary bladder results in morphological impairment of the urothelial barrier that is associated with a loss of superficial umbrella cells during the early as well as initial late radiation response phase.

Radiation Induced Inflammatory Changes in the Mouse Bladder: The Role of Cyclooxygenase-2

PURPOSE

We assessed the effect of irradiation on COX-2 expression in blood vessels of the mouse bladder wall during the early and late radiation response phases. Vasodilatation was quantified as an additional marker of inflammation related to COX-2 activity.

MATERIALS AND METHODS

Female C3H/Neu mice were irradiated with a single dose of 20 Gy. The intensity of the COX-2 immunohistochemical staining signal was assessed using an arbitrary semiquantitative score of 0 to 3. To evaluate vasodilatation the percent of the bladder wall covered by the lumen of the blood vessels, depicted as vascular area, was determined.

RESULTS

Constitutive COX-2 expression was found in the tunica intima and media of bladder blood vessels. During the early response significant biphasic changes were detected in the COX-2 staining signal as well as in the vascular area with peak values on days 4 and 16 after irradiation. A significant association was found between vascular area and COX-2 expression in blood vessels during the early radiation response (p <0.0001). No changes in COX-2 expression were observed during the late phase, that is between days 90 and 360 after irradiation. Minor vasodilatation seen during the late phase did not correlate with COX-2 activity.

CONCLUSIONS

Irradiation resulted in pronounced COX-2 dependent inflammatory changes in the bladder wall during the early but not during the late radiation reaction. Therefore, a potential effect of COX-2 inhibition on early radiation side effects in the bladder can be proposed.