An Initial Research On The Bladder Pacemaker And Its Relationship With Detrusor Instability

Detrusor instability (DI) is one of the most common bladder micturition dysfunction in clinic. The incidence rate could be about 39% in the patients of lower urinary tract obstruction.The patient often suffers from urinary frequency, urinary urgency and urgency incontinence.These symptoms always ruin the patient's life and can cause even more serious damages such as hydronephrosis, hydroureterosis and renal dysfunction. However, as the pathogenic mechanism of DI is still unclear,the treatment of DI is not satisfactory right now.The most recently research shows that the bladder detrusor is a special kind of excitable muscle, the change of excitability of detrusor may play a significant role in the occurance of DI.Besides, scientists also find that this kind of excitability probably originates from the Cajal-like cells of interstitial,which are very similar to the interstitial cells of Cajal (ICCs) in the enteric nervous system.If the Cajal-like cells of interstitial really innervate the spontaneously contraction of bladder detrusor,there must be a bladder pacemaker to keep the contraction smooth and coordinate. Unfortunately, there are a few reports about the bladder pacemaker.The object of the study is to establish a model of rat DI and explore the change difference of number, function, excitability and signal trans- mission of bladder Cajal-like cells of interstitial in the dome, lateral,base and triangle zone between the DI and normal rats, so as to investigate the position of bladder pacemaker and its distribution to DI.The result is expected to be helpful to the research of the pathogenesis and treatment of DI. Objective:To establish and evaluate the model of rat DI and provide a simple and reliable experiment platform for the further research of DI.Methods:We selected 25 healthy female Wistar rats and divided them into DI group(n=15) and control group(n=10) randomly. The rat of DI group was performed a surgery of bladder outlet obstruction. The rats of both groups underwent cystemetry after intra-urethral cannula 6 weeks after the surgery and the result of bladder capacity, residual volume, voiding volume and maximum voiding pressure was compared between the two groups.Results:2 rats of DI group died and DI ratio of the rest experiment rats was 69.2% according to the urodynamic test 6 weeks after the operation. Compared to the control group, the bladder capacity, residual volume, voiding volume and maximum voiding pressure were significantly increased in the DI group.Conclusion:The bladder function of DI rat is compensable enhanced during the early period of BOO. Partly ligation of the rat bladder outlet and filling cystemetry under urethane anesthetic can be a easy and reliable method to establish a DI model. Objective:To investigate the change of cell number and function of Cajal-like cells of interstitial in different parts between DI and control grpups of rat.Methods:(1)The existence of Cajal-like cells of interstitial was detected by immunofluorescence methods, and the quantity change and change range of different part of DI group compared to control group was also assessed; (2)The change of expression of c-kit protein of different part of DI group compared to control group was analyzed using Western blot.Results:(1)The quantity of Cajal-like cells of interstitial of bladder dome was significantly higher than other three parts in both two groups, and the cell number of each part of DI rat was significantly increased compared to normal rat, especially the dome wall; (2)The expression of c-kit of each part of DI rat was obviously higher than its counterpart of normal rat. There was no difference of expression of c-kit among the four parts of bladder wall of normal rat.The expression of c-kit of the dome wall of DI rat was significantly higher than other parts while the difference was not obvious in the lateral,base and triangle parts.Conclusion:There is a significantly difference of quantity and expression of c-kit between the dome wall and other parts of DI rat bladder. The change range of Cajal-like cells of interstitial of the dome wall of DI rat compared with its counertpart of normal rat is also larger than other parts. The quantity and function of Cajal-like cells of interstitial are enhanced significantly in DI rats and the dome wall is probably the location of bladder pacemaker. Objective:To investigate the change of excitability of Cajal-like cells of interstitial in differentparts between DI and control groups of rat.Methods:(1)The relationship of HCN2 protein and Cajal-like cells of interstitial was accessed by double-labeled immunofluorescence with HCN2 and c-kit.(2) The change of expression of HCN2 protein of different part of DI group compared to control group was analyzed on the level of protein and gene using Western blot and RT-PCR assay respectively.Results:(1)HCN was identified in Cajal-like cells of interstitial of rat bladder.(2) The expression of HCN2 protein and mRNA of each part of DI rat was obviously higher than its counterpart of normal rat. There was no difference of expression of HCN2 among the four parts of bladder wall of normal rat.The expression of HCN2 of the dome wall of DI rat was significantly higher than other parts while the difference was not obvious in the lateral,base and triangle parts.Conclusion:There is a significantly difference of expression of HCN2 between the dome wall and other parts of DI rat bladder. The change range of Cajal-like cells of interstitial of the dome wall of DI rat compared to its counertpart of normal rat is also larger than other parts. The excitability of Cajal-like cells of interstitial are enhanced significantly in DI rats and the bladder pacemaker dome wall is more likely located in the dome wall. Objective:To investigate the change of signal transmission of detrusor tissues in different parts between DI and control groups of rat.Methods:(1)The relationship of connexin43 protein and Cajal-like cells of interstitial was acessed by double-labeled immunofluorescence with connexin43 and c-kit. (2) The change of expression of connexin43 protein of different part of DI group compared to control group was analyzed by Western blot assay.Results:(1)connexin43 was mainly identified in Cajal-like cells of interstitial of rat bladder.(2) The expression of connexin43 of each part of DI rat was obviously higher than its counterpart of normal rat. There was no difference of expression of connexin43 among the four parts of bladder wall of normal rat.The expression of connexin43 of the dome wall of DI rat was significantly higher than other parts while the difference was not obvious in the lateral,base and triangle parts.Conclusion:There is a significantly difference of expression of connexin43 between the dome wall and other parts of DI rat bladder. The change range of the dome wall of DI rat compared to its counertpart of normal rat is also larger than other parts. The signal transmission of Cajal-like cells of interstitial are enhanced significantly in DI rats and the electric activity is more active in the dome wall than in other three parts.