Introduction and Objectives
Cyclophosphamide (CYP) damages all mucosal defence lines of urinary bladder and induces chemical cystitis leading to overactive bladder (OAB). The aim of this study was to estimate the effect of CYP on bladder wall architecture, as well as inflammatory cells and mast cells activity.
Material and Methods
Twenty four female Wistar rats were randomly divided into four equal groups: I – control, II – acute OAB, III – chronic OAB, IV – sham group. Acute and chronic OAB were induced by CYP in single dose (200 mg/kg ip.) and four doses (75 mg/kg ip. every 3rd day for 7 days of experiment), respectively. All animals were sacrificed by pentobarbital overdose. After bladder removal, thin sections were cut and stained with hematoxylin and eosin for histological assessment and with toluidine blue for mast cells evaluation. In each fragment 10 consecutive cross sections were examined. The severity of inflammation was examined according to 4 criteria (mucosal abrasion, hemorrhage, leukocyte infiltration and oedema). In addition, the total number of mast cells was counted at 200× magnification.
Results
The CYP-treated rats exhibited macroscopical signs of urinary bladder inflammation, i.e. redness, oedema (in group II, III) and also wall thickening, mucosal erosions, ulcerations, petechial hemorrhages on the serosal surface (in group III). In some animals of the group III the urine contained blood. Rats in the groups I and IV had healthy bladders and normal urine. Microscopic evaluations of acute and chronic OAB walls revealed increased severity of inflammatory cells infiltration of bladder wall (neutrophils and mononuclear cells). Compared to the control group, a single dose of CYP caused increased activity of mast cells. However, chronic administration of CYP suppressed the activity of mast cells within bladder wall. Furthermore, CYP-treated rats showed clear signs of inflammation; however the alteration of bladder histological structure depends on the mode of CYP administration. Acute model caused more severe mucosal abrasion compared to chronic one which revealed more developed haemorrhage changes within bladder wall. Additionally, in acute and chronic OAB we observed similar tissue oedema changes. Optional comparison bladder histological architecture and hyperemia degree between rats after (group I) and without (group IV) bladder catheter implantation showed no significant changes.
Conclusions
CYP induces chemical cystitis with alteration in histological structure and inflammatory cells activity. The suppression of mast cells in chronic OAB seems to be a result of direct cytotoxic effect of CYP, as well as stems from a decrease of peripherally (within bladder) substance P release by afferent C fibres endings. Our results prove that acute model of CYP-induced cystitis in rats is more credible for further evaluation of neurogenic inflammation response in overactive bladder.
Article info
Identification
Copyright
© 2009 European Association of Urology. Published by Elsevier Inc. All rights reserved.
