All rats were used according to protocols approved by the Animal Experimental Committee of Beijing Friendship Hospital, Capital Medical University.
1. Surgical preparation, anesthetization, and surgical techniques
NOTE: A total of 40 female Wistar rats, weighing 200&#8211;220 g, were commercially obtained for the present study. Of the 40 rats, 10 were randomly selected as the control group, and the rest were treated as the test group. All animals were housed in a sterile environment in the animal facilities of Beijing Friendship Hospital, Capital Medical University.
<ol>
	<li>Perform general anesthesia by administering sodium pentobarbital intraperitoneally (40 mg/kg). Alternatively, induce&#160;anesthesia using 3%-4% isoflurane and maintain it at 1%-3% (inhaled). Apply ophthalmic ointment on the&#160;eyes to prevent dryness. Then, place the rat on the surgical platform&#160;and provide thermal support.&#160; 
	NOTE:&#160;Administer analgesics such as buprenorphine, 0.05 mg/kg, SC, 0.1-0.2 mL at the beginning of the procedure.</li>
	<li>Check for the depth of anesthesia by the lack of response to the toe pinch. Shave the fur from the whole back area with a razor.</li>
	<li>Sterilize the surgical site with at least 3 cycles of a two-stage scrub such as Chlorhexidine or Povidone iodine followed by Isopropyl alcohol. Secure the limbs with surgical tape and make a median incision of about 3 cm on the back with surgical scissors.</li>
	<li>Deepen the incision through the subcutaneous tissues using surgical scissors&#160;and cut off the muscles attached to the spine.</li>
	<li>Visually identify and expose the 13th rib (the intervertebral space connected to that rib is interval T13&#8210;L1). Mark the 13th rib using a suture.</li>
	<li>After identification, carefully resect the muscles attached to the spine and expose the vertebral column. Resect the supraspinous ligament and interspinous ligament for an accurate identification of the vertebral column. Expose the level of L4&#8210;L5 with surgical scissors&#160;and forceps. 
	NOTE: The supraspinous ligament can be identified easily because of the presence of thin subcutaneous tissue. After the resection of supraspinous ligament, the ligament between spinous process is interspinous ligament.</li>
	<li>Carefully dissect away the L4&#8210;L5 vertebral spinous process and parts of the transverse process using Kelly forceps to expose the spinal cord (Figure 1).</li>
	<li>Completely expose the conus medullaris at the L4&#8210;L5 level and transect the conus medullaris totally with iridectomy scissors. Insert some tissue packing to block the recovery of the spinal cord.</li>
	<li>Close the overlying muscle and skin on the outer skin layer using 4-0 non-absorbable suture.</li>
	<li>For the control group, perform steps 1.1&#8210;1.7, and leave the conus medullaris intact. Close the incision according to step 1.9.</li>
</ol>
2. Animal recovery
<ol>
	<li>Keep the rats in a temperature-controlled incubator (37&#160;&#176;C) during the first hour post-operation and monitor them until they are&#160;sternal or actively moving. 
	NOTE: It takes about half an hour for total recovery.</li>
	<li>Transfer the animal to a clean cage with sufficient food and water. Keep the rats in separate cages. 
	NOTE: The transection&#39;s success is indicated when the rats in the test group move only with the help of forelegs, whereas the rats in the control group could walk normally.</li>
</ol>
3. Post-operation management
<ol>
	<li>Inject Penicillin G, an antibiotic (50,000 U/mL per animal) intraperitoneally. Administer analgesics such as buprenorphine, 0.05 mg/kg, SC, 0.1-0.2 mL&#160;every 6-12 hr for 48 hr post-operation.</li>
	<li>Compress the urinary bladder at the hypogastrium to help with the voiding. Perform this twice daily at the same time (8 am and 8 pm) for six weeks. 
	NOTE: The loss of normal constriction of detrusor is the symbol of DU.</li>
	<li>House all rats in metabolic cages, each containing a urine collection funnel placed over a previously weighed absorbent paper to monitor the micturition and incontinence.</li>
	<li>Collect and note the weight change of absorbent paper, which indicates the voided volume (VV), and the residual urine volume separately.</li>
</ol>
4. Urodynamic testing
<ol>
	<li>At six-weeks post-operation, perform a cystometrogram, using urodynamic measurement equipment as follows.
	<ol>
		<li>Anesthetize rats by injecting 10% chloral hydrate into the peritoneal cavity (3 mL/kg).</li>
		<li>Compress the bladder for voiding, then fix the rat to the surgical platform using a tape.</li>
		<li>Insert the epidural catheter (3F) into the bladder and connect the urodynamic measurement equipment, epidural catheter, and infusion pump by the three-limb tube.</li>
		<li>Pump physiological saline at a speed of 0.2 mL/min for urodynamic measurement (see Table of Materials). Record the MCC and DOP, and compliance of the bladder (calculated by dividing &#948; bladder volume with &#948; pressure of the detrusor).</li>
	</ol>
	</li>
</ol>
5. Statistical analysis
<ol>
	<li>Perform statistical analysis using commercially available software.</li>
	<li>Use Kolmogorov-Smirnov test to test the normality of data.</li>
	<li>Express the normally distributed variables as mean values with standard deviations. Use the two-tailed paired Student&#8217;s t-tests to compare the parameters of cystometrogram in both groups. 
	NOTE: p &#60; 0.05 indicates that the difference had statistical significance.</li>
</ol>

<ol><li>van Koeveeringe, G. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Detrusor+underactivity%3A+Pathophysiological+considerations%2C+models+and+proposals+for+future+research%5BTitle%5D)+AND+%22Neurourology+and+Urodynamics%22%5BJournal%5D)">Detrusor underactivity: Pathophysiological considerations, models and proposals for future research.</a> Neurourology and Urodynamics. 33 (5), ICI-RS 2013 591-596 (2014).</li>
<li>Osman, N. I., Esperto, F., Chapple, C. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Detrusor+Underactivity+and+the+Underactive+Bladder%3A+A+Systematic+Review+of+Preclinical+and+Clinical+Studies%5BTitle%5D)+AND+%22European+Urology%22%5BJournal%5D)">Detrusor Underactivity and the Underactive Bladder: A Systematic Review of Preclinical and Clinical Studies.</a> European Urology. 74 (5), 633-643 (2018).</li>
<li>Osman, N. I., Chapple, C. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Contemporary+concepts+in+the+aetiopathogenesis+of+detrusor+underactivity%5BTitle%5D)+AND+%22Nature+Reviews.+Urology%22%5BJournal%5D)">Contemporary concepts in the aetiopathogenesis of detrusor underactivity.</a> Nature Reviews. Urology. 11 (11), 639-648 (2014).</li>
<li>Panicker, J. N., Nagaraja, D., Kovoor, J. M. E., Nair, K. P. S., Subbakrishna, D. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Lower+urinary+tract+dysfunction+in+acute+disseminated+encephalomyelitis%5BTitle%5D)+AND+%22Multiple+Sclerosis%22%5BJournal%5D)">Lower urinary tract dysfunction in acute disseminated encephalomyelitis.</a> Multiple Sclerosis. 15 (9), Houndmills, Basingstoke, England. 1118-1122 (2009).</li>
<li>Lee, W. C., Wu, H. P., Tai, T. Y., Yu, H. J., Chiang, P. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Investigation+of+urodynamic+characteristics+and+bladder+sensory+function+in+the+early+stages+of+diabetic+bladder+dysfunction+in+women+with+type+2+diabetes%5BTitle%5D)+AND+%22The+Journal+of+Urology%22%5BJournal%5D)">Investigation of urodynamic characteristics and bladder sensory function in the early stages of diabetic bladder dysfunction in women with type 2 diabetes.</a> The Journal of Urology. 181 (1), 198-203 (2009).</li>
<li>Araki, I., Kitachara, M., Oida, T., Kuno, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Voiding+dysfunction+and+Parkinson%E2%80%99s+disease%3A+urodynamic+abnormalities+and+urinary+symptoms%5BTitle%5D)+AND+%22The+Journal+of+Urology%22%5BJournal%5D)">Voiding dysfunction and Parkinson’s disease: urodynamic abnormalities and urinary symptoms.</a> The Journal of Urology. 164 (5), 1640-1643 (2000).</li>
<li>Meng, N. H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Incomplete+bladder+emptying+in+patients+with+stroke%3A+is+detrusor+external+sphincter+dyssynergia+a+potential+cause%5BTitle%5D)+AND+%22Archives+of+Physical+Medicine+and+Rehabilitation%22%5BJournal%5D)">Incomplete bladder emptying in patients with stroke: is detrusor external sphincter dyssynergia a potential cause.</a> Archives of Physical Medicine and Rehabilitation. 91 (7), 1105-1109 (2010).</li>
<li>FitzGerald, M. P., Brubaker, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((The+etiology+of+urinary+retention+after+surgery+for+genuine+stress+incontinence%5BTitle%5D)+AND+%22Neurourology+and+Urodynamics%22%5BJournal%5D)">The etiology of urinary retention after surgery for genuine stress incontinence.</a> Neurourology and Urodynamics. 20 (1), 13-21 (2001).</li>
<li>Rahman, M., Siddik, A. B. Neuroanatomy, Pontine Micturition Center. <a target="_blank" href="http://scholar.google.com/scholar?hl=en&safe=off&q=author%3aRahman%2C+M+%22StatPearls%22">StatPearls</a>. , (2020).</li>
<li>Wrobel, A., Lancut, M., Rechberger, T. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((A+new+model+of+detrusor+overactivity+in+conscious+rats+induced+by+retinyl+acetate+instillation%5BTitle%5D)+AND+%22Journal+of+Pharmacological+and+Toxicological+Methods%22%5BJournal%5D)">A new model of detrusor overactivity in conscious rats induced by retinyl acetate instillation.</a> Journal of Pharmacological and Toxicological Methods. 74 (7), 16(2015).</li>
<li>Rosenzweig, E. S., McDonald, J. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Rodent+models+for+treatment+of+spinal+cord+injury%3A+research+trends+and+progress+toward+useful+repair%5BTitle%5D)+AND+%22Current+Opinion+in+Neurology%22%5BJournal%5D)">Rodent models for treatment of spinal cord injury: research trends and progress toward useful repair.</a> Current Opinion in Neurology. 17 (2), 121-131 (2004).</li>
<li>Yoo, K. H., Lee, S. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Experimental+animal+models+of+neurogenic+bladder+dysfunction%5BTitle%5D)+AND+%22International+Neurourology+Journal%22%5BJournal%5D)">Experimental animal models of neurogenic bladder dysfunction.</a> International Neurourology Journal. 14 (1), 1-6 (2010).</li>
<li>Kanai, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Sophisticated+models+and+methods+for+studying+neurogenic+bladder+dysfunction%5BTitle%5D)+AND+%22Neurourology+and+Urodynamics%22%5BJournal%5D)">Sophisticated models and methods for studying neurogenic bladder dysfunction.</a> Neurourology and Urodynamics. 30 (5), 658-667 (2011).</li>
<li>Nomiya, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Progressive+vascular+damage+may+lead+to+bladder+underactivity+in+rats%5BTitle%5D)+AND+%22The+Journal+of+Urology%22%5BJournal%5D)">Progressive vascular damage may lead to bladder underactivity in rats.</a> The Journal of Urology. 191 (5), 1462-1469 (2014).</li>
<li>Seki, T., Hida, K., Tada, M., Koyanagi, I., Iwasaki, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Graded+contusion+model+of+the+mouse+spinal+cord+using+a+pneumatic+impact+device%5BTitle%5D)+AND+%22Neurosurgery%22%5BJournal%5D)">Graded contusion model of the mouse spinal cord using a pneumatic impact device.</a> Neurosurgery. 50 (5), discussion 1081-1082 1075-1081 (2002).</li>
<li>Yeo, S. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Development+of+a+rat+model+of+graded+contusive+spinal+cord+injury+using+a+pneumatic+impact+device%5BTitle%5D)+AND+%22Journal+of+Korean+Medical+Science%22%5BJournal%5D)">Development of a rat model of graded contusive spinal cord injury using a pneumatic impact device.</a> Journal of Korean Medical Science. 19 (4), 574-580 (2004).</li>
<li>Bergman, B. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Spinal+cord+transplants+permit+the+growth+of+serotonergic+axons+across+the+site+of+neonatal+spinal+cord+transection%5BTitle%5D)+AND+%22Brain+Research%22%5BJournal%5D)">Spinal cord transplants permit the growth of serotonergic axons across the site of neonatal spinal cord transection.</a> Brain Research. 431 (2), 265-279 (1987).</li>
<li>Chancellor, M. B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Underactive+bladder%3B+Review+of+progress+and+impact+from+the+International+CURE-UAB+Initiative%5BTitle%5D)+AND+%22International+Neurourology+Journal%22%5BJournal%5D)">Underactive bladder; Review of progress and impact from the International CURE-UAB Initiative.</a> International Neurourology Journal. 24 (1), 3-11 (2020).</li>
<li>Pfisterer, M. H. D., Griffiths, D. J., Schaefer, W., Resnick, N. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((The+effect+of+age+on+lower+urinary+tract+function%3A+a+study+in+women%5BTitle%5D)+AND+%22Journal+of+the+American+Geriatrics+Society%22%5BJournal%5D)">The effect of age on lower urinary tract function: a study in women.</a> Journal of the American Geriatrics Society. 54 (3), 405-412 (2006).</li>
<li>Duchen, L. W., Anjorin, A., Watkins, P. J., Mackay, J. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Pathology+of+autonomic+neuropathy+in+diabetes+mellitus%5BTitle%5D)+AND+%22Annals+of+Internal+Medicine%22%5BJournal%5D)">Pathology of autonomic neuropathy in diabetes mellitus.</a> Annals of Internal Medicine. 92 (2), 301-303 (1980).</li>
<li>Schneider, T., Hein, P., Bai, J., Michel, M. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((A+role+for+muscarinic+receptors+or+rho-kinase+in+hypertension+associated+rat+bladder+dysfunction%5BTitle%5D)+AND+%22The+Journal+of+Urologoy%22%5BJournal%5D)">A role for muscarinic receptors or rho-kinase in hypertension associated rat bladder dysfunction.</a> The Journal of Urologoy. 173 (6), 2178-2181 (2005).</li>
<li>Drake, M. J., Harvey, I. J., Gillespie, J. I., Van Duyl, W. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Localized+contractions+in+the+normal+human+bladder+and+in+urinary+urgency%5BTitle%5D)+AND+%22BJU+International%22%5BJournal%5D)">Localized contractions in the normal human bladder and in urinary urgency.</a> BJU International. 95 (7), 1002-1005 (2005).</li>
<li>Suskind, A. M., Smith, P. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((A+new+look+at+detrusor+underactivity%3A+impaired+contractility+versus+afferent+dysfunction%5BTitle%5D)+AND+%22Current+Urology+Reports%22%5BJournal%5D)">A new look at detrusor underactivity: impaired contractility versus afferent dysfunction.</a> Current Urology Reports. 10 (5), 347-351 (2009).</li>
<li>Osman, N. I., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Detrusor+underactivity+and+the+underactive+bladder%3A+A+new+clinical+entity%3F+A+review+of+current+terminology%2C+definitions%2C+epidemiology%2C+aetiology%2C+and+diagnosis%5BTitle%5D)+AND+%22European+Urology%22%5BJournal%5D)">Detrusor underactivity and the underactive bladder: A new clinical entity? A review of current terminology, definitions, epidemiology, aetiology, and diagnosis.</a> European Urology. 65 (2), 389-398 (2014).</li>
</ol>

The authors have nothing to disclose.

DU is a common cause of lower urinary tract symptoms in both men and women. It is a complex constellation of symptoms with few treatment options that can significantly diminish the quality-of-life (Qol) of those affected18. Although it is believed that DU is multifactorial, the understanding of its pathogenesis remains rudimentary. Studies have shown that the pathogenesis of DU might be related to myogenic and neurogenic factors.
In the myogenic hypotheses, it was obser...

Detrusor underactivity (DU) is a typical lower urinary tract dysfunction that has remained under studied. Even though DU has been defined by the International Continence Society (ICS)1, numerous different terminologies are used to refer to this disease, e.g., &#8220;detrusor failure,&#8221; &#8220;acontractile bladder,&#8221; &#8220;detrusor areflexia&#8221;2. DU, as defined by the International Continence Society (ICS) in 2002, is a contraction of reduced strength and duration, which results in prolonged increase in time for bladder emptying, thereby resulting in failure to achieve complete bladder emptying within a normal period.
DU may affect 48% of men and 12% of women (aged &#62;70 years)3 with lower urinary tract symptoms. It seems to be multifactorial, and no effective treatment exists. It is reported that DU is ubiquitous in patients with neurogenic bladder dysfunction, such as multiple sclerosis4, diabetes mellitus5, Parkinson&#8217;s disease6, or cerebral stroke7. DU can also be caused by iatrogenic nerve damage, such as laparoscopic hysterectomy, prostatectomy, or other surgical interventions in the small pelvis8. The pathophysiology changes and available treatments of DU are still confusing because of the lack of an appropriate animal model for study.
The micturition reflex is controlled by spino-bulbospinal pathways that combines the pontine micturition center, sacral parasympathetic nucleus, and more senior cortex centers9. Activation and maintenance of the micturition reflex mainly depend on the regular transport of sensory signals from the bladder to more senior cortex centers. It may be postulated that sensory dysfunction contributes to DU.
Most experimental animal studies related to lower urinary tract dysfunctions have focused on overactive bladder (OAB) models10. These models provide a reasonable understanding of OAB pathophysiology and prognosis. However, only a few DU models have been reported, e.g., supraspinal injury (local lesions, decerebration, and middle cerebral artery occlusion), spinal cord transection or contusion injury, systemic (e.g., cyclophosphamide) or intravesical administration of irritant or in&#64258;ammatory agents (e.g., acid, acrolein, and lipopolysaccharide)11,12,13,14. Among these methods, only the spinal cord transection or contusion injury method can be used in establishing an animal model of DU13. Attempts involving the injury of the pontine micturition center and higher cortex centers were abandoned because of the severe trauma. So, increased attention is being paid to find an accurate location in the micturition reflex center to induce the DU with minimum side effects.
As mentioned previously, one of the mechanisms of inducing DU is to injure the spinal cord to damage the signaling pathway of the micturition reflex. Allen&#8217;s weight-drop method was developed to establish laboratory animals with injured spinal cords15. However, there are no further experimental data available on this method. Moreover, since parts of the animals recovered spinal function after stroke without DU, it cannot be considered as a perfect method for generating a DU animal model16.
In 1987, Bregman excogitated a process of transecting the spinal cord for generating the DU animal model and acquired experimental data17. Nevertheless, this method was not applied to establish the DU animal model. At that time, researchers were still confused about the pathogenesis of DU. As locations in the spinal cord associated with the induction of OAB or DU are adjacent to each other, they were unable to find the accurate site of damage to the spinal cord to induce DU17. OAB and DU were introduced either together or separately by this method. So, although this method introduced DU, it was imprecise and could not be used for the understanding of DU&#8217;s occurrence and processing.
As stated above, the lack of a suitable animal model of DU is one of the main obstacles for the study of DU. Researchers are continuously looking for an accurate and manageable model that can simulate the pathology of DU. Even the treatment options for DU have not significantly improved during the last 20 years. Collectively, there is a great need to describe a standard protocol for establishing an animal model of DU.
So, in this paper, we describe a method to successfully establish a rat model of DU by conus medullaris transection. Transection was performed at the L4&#8210;L5 level to separate the conus medullaris. The maximum cystometric capacity (MCC), detrusor opening pressure (DOP), and compliance of the bladder were recorded and analyzed to validate the protocol. The protocol stated below combines both feasibility and reliability in a standardized manner to establish the DU animal model, simulating the occurrence and processing of DU. The protocol can be used as a technique for further study of DU.

<table><tbody><tr><td>0.9% saline</td><td>Wuhan Prosai Company</td><td>EY-C1178</td><td>pump for urodynamic measurement</td></tr><tr><td>10% chloral hydrate</td><td>Shandong Yulong Co., Ltd</td><td>H37022673</td><td>3mL/kg, administered intraperitoneally</td></tr><tr><td>Buprenorphine Hydrochloride Injection</td><td>Tianjin Pharmaceutical Research Institute Pharmaceutical Co. LTD</td><td>H12020275</td><td>0.05mg/kg subcutaneously 24h and 48h postoperation</td></tr><tr><td>Epidural Catheter</td><td>Shandong Xinghua Co, Ltd</td><td>VABR3L</td><td>for urodynamic measurement</td></tr><tr><td>Penicillin G</td><td>Alta Technology Co., Ltd</td><td>1ST5637</td><td>50,000 unit/ml per animal</td></tr><tr><td>pentobarbital</td><td>Beijing solabo Technology Co., Ltd</td><td>NK-WF0001</td><td>40 mg/kg, administered intraperitoneally</td></tr><tr><td>Suture line(4-0)</td><td>ETHICON</td><td>VCP422H</td><td>suture the injury</td></tr><tr><td>Three-limb tube</td><td>Shandong Xinghua Co, Ltd</td><td>VAB3T</td><td>for urodynamic measurement</td></tr><tr><td>Trace infusion pump</td><td>Zhejiang Smith Medical Instrument Co., Ltd</td><td>20162540335</td><td>Pump the saline at a speed of 0.2ml/min for urodynamic measurement</td></tr><tr><td>Urodynamic measurement equipment</td><td>Medical Measurement SystemsB.V.</td><td>08-0467</td><td>urodynamic measurement equipment can not only help the diagnosis of dysuria, but also provide objective materials for treatment and therapeutic effect. It is the most commonly used examination method in clinical diagnosis and treatment of lower urinary tract functional diseases</td></tr><tr><td>Wistar Rats</td><td>HFK Biotechnology Co.Ltd,Beijing ,China</td><td>SCXK2012-0023</td><td>200-220g</td></tr></tbody></table>

detrusor underactivity model in rats by conus medullaris transection

The goal of the presented protocol was to establish a detrusor underactivity (DU) model in the rat through conus medullaris transection. Laminectomy was performed in a total of 40 female Wistar rats (control group: 10 rats; test group: 30 rats) weighing 200&#8211;220 g, and the conus medullaris was transected at the L4&#8210;L5 level in the test group. All the rats were housed and fed under the same environmental conditions for six weeks. In the test group, urine voiding was performed twice daily for six weeks, and mean residual urine volume was recorded. A cystometrogram was performed in both groups. Maximum cystometric capacity (MCC), detrusor opening pressure (DOP), and compliance of the bladder were recorded and calculated. The test group showed significant urinary retention after the surgery, both during and after the spinal shock. However, no abnormality was observed in the control group. When compared to the control group, the MCC and compliance of bladder in the test group was significantly higher than that of the test group (3.24 &#177; 2.261 mL versus 1.04 &#177; 0.571 mL; 0.43 &#177; 0.578 mL/cmH2O versus 0.032 &#177; 0.016 mL/cmH2O), whereas DOP in the test group was lower than control (20.28 &#177; 14.022 cmH2O versus 35 &#177; 13.258 cmH2O). This method of establishing an animal model of DU by the conus medullaris transection offers an excellent opportunity to understand DU&#8217;s pathophysiology in a better manner.

The entire procedure of the conus medullaris transection can be completed within 45 min by experienced surgeons. Our laboratory has performed over 100 cases of conus medullaris transection surgeries. The success rate is over 95%, as defined by the rats&#8217; survival and successful induction of DU. The urodynamic test confirmed the induction of DU.
Based on our experience, the induction of DU can be preliminarily evaluated by the residual urine volume. The retention of urine was observed imme...

Watch this Scientific Journal Video about Detrusor Underactivity Model in Rats by Conus Medullaris Transection at JoVE.com

Detrusor Underactivity Model in Rats by Conus Medullaris Transection

We present a method for establishing a detrusor underactivity model by conus medullaris transection in rats. Detrusor underactivity was successfully stimulated in these animals. The model can be used for studying urinary tract function.

The goal of the presented protocol was to establish a detrusor underactivity (DU) model in the rat through conus medullaris transection. Laminectomy was ...

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2.0K Views.  Capital Medical University. We presenteren een methode voor het vaststellen van een detrusor onderactiviteitsmodel door conus medullaris transection bij ratten. Detrusor onderactiviteit werd bij deze dieren met succes gestimuleerd. Het model kan worden gebruikt voor het bestuderen van de urinewegfunctie.

Video: Detrusor Underactivity Model in Rats by Conus Medullaris Transection

Evaluation of Biomaterials for Bladder Augmentation using Cystometric Analyses in Various Rodent Models

Renal function and continence of urine are critically dependent on the proper function of the urinary bladder, which stores urine at low pressure and expels it with a precisely orchestrated contraction. A number of congenital and acquired urological anomalies including posterior urethral valves, benign prostatic hyperplasia, and neurogenic bladder secondary to spina bifida/spinal cord injury can result in pathologic tissue remodeling leading to impaired compliance and reduced capacity1. Functional or anatomical obstruction of the urinary tract is frequently associated with these conditions, and can lead to urinary incontinence and kidney damage from increased storage and voiding pressures2. Surgical implantation of gastrointestinal segments to expand organ capacity and reduce intravesical pressures represents the primary surgical treatment option for these disorders when medical management fails3. However, this approach is hampered by the limitation of available donor tissue, and is associated with significant complications including chronic urinary tract infection, metabolic perturbation, urinary stone formation, and secondary malignancy4,5.
Current research in bladder tissue engineering is heavily focused on identifying biomaterial configurations which can support regeneration of tissues at defect sites. Conventional 3-D scaffolds derived from natural and synthetic polymers such as small intestinal submucosa and poly-glycolic acid have shown some short-term success in supporting urothelial and smooth muscle regeneration as well as facilitating increased organ storage capacity in both animal models and in the clinic6,7. However, deficiencies in scaffold mechanical integrity and biocompatibility often result in deleterious fibrosis8, graft contracture9, and calcification10, thus increasing the risk of implant failure and need for secondary surgical procedures. In addition, restoration of normal voiding characteristics utilizing standard biomaterial constructs for augmentation cystoplasty has yet to be achieved, and therefore research and development of novel matrices which can fulfill this role is needed.
In order to successfully develop and evaluate optimal biomaterials for clinical bladder augmentation, efficacy research must first be performed in standardized animal models using detailed surgical methods and functional outcome assessments. We have previously reported the use of a bladder augmentation model in mice to determine the potential of silk fibroin-based scaffolds to mediate tissue regeneration and functional voiding characteristics.11,12 Cystometric analyses of this model have shown that variations in structural and mechanical implant properties can influence the resulting urodynamic features of the tissue engineered bladders11,12. Positive correlations between the degree of matrix-mediated tissue regeneration determined histologically and functional compliance and capacity evaluated by cystometry were demonstrated in this model11,12. These results therefore suggest that functional evaluations of biomaterial configurations in rodent bladder augmentation systems may be a useful format for assessing scaffold properties and establishing in vivo feasibility prior to large animal studies and clinical deployment. In the current study, we will present various surgical stages of bladder augmentation in both mice and rats using silk scaffolds and demonstrate techniques for awake and anesthetized cystometry.

Surgical stages of bladder augmentation are described using 3-D scaffolds in murine and rat models. To test the efficacy of biomaterial configurations for use in bladder augmentation, techniques for both awake and anesthetized cystometry are presented.

Renal function and continence of urine are critically dependent on the proper function of the urinary bladder, which stores urine at low pressure and ...

Bioengineering

The Use of Cystometry in Small Rodents: A Study of Bladder Chemosensation

The lower urinary tract (LUT) functions as a dynamic reservoir that is able to store urine and to efficiently expel it at a convenient time. While storing urine, however, the bladder is exposed for prolonged periods to waste products. By acting as a tight barrier, the epithelial lining of the LUT, the urothelium, avoids re-absorption of harmful substances. Moreover, noxious chemicals stimulate the bladder's nociceptive innervation and initiate voiding contractions that expel the bladder's contents. Interestingly, the bladder's sensitivity to noxious chemicals has been used successfully in clinical practice, by intravesically infusing the TRPV1 agonist capsaicin to treat neurogenic bladder overactivity1. This underscores the advantage of viewing the bladder as a chemosensory organ and prompts for further clinical research. However, ethical issues severely limit the possibilities to perform, in human subjects, the invasive measurements that are necessary to unravel the molecular bases of LUT clinical pharmacology. A way to overcome this limitation is the use of several animal models2. Here we describe the implementation of cystometry in mice and rats, a technique that allows measuring the intravesical pressure in conditions of controlled bladder perfusion.
	After laparotomy, a catheter is implanted in the bladder dome and tunneled subcutaneously to the interscapular region. Then the bladder can be filled at a controlled rate, while the urethra is left free for micturition. During the repetitive cycles of filling and voiding, intravesical pressure can be measured via the implanted catheter. As such, the pressure changes can be quantified and analyzed. Moreover, simultaneous measurement of the voided volume allows distinguishing voiding contractions from non-voiding contractions3.
	Importantly, due to the differences in micturition control between rodents and humans, cystometric measurements in these animals have only limited translational value4. Nevertheless, they are quite instrumental in the study of bladder pathophysiology and pharmacology in experimental pre-clinical settings. Recent research using this technique has revealed the key role of novel molecular players in the mechano- and chemo-sensory properties of the bladder.

Cystometry is an efficient technique to measure bladder function of small animals in vivo. The bladder is continuously infused at rates controlled through an intravesical catheter, whereas the urethra is left free for micturition. This allows for repetitive filling and emptying of the bladder, while intravesical pressure and voided volume are recorded.

	The lower urinary tract (LUT) functions as a  dynamic reservoir that is able to store urine and to efficiently expel it at a  convenient time. While ...

Medicine

Urinary Bladder Distention Evoked Visceromotor Responses as a Model for Bladder Pain in Mice

Approximately 3-8 million people in the United States suffer from interstitial cystitis/bladder pain syndrome (IC/BPS), a debilitating condition characterized by increased urgency and frequency of urination, as well as nocturia and general pelvic pain, especially upon bladder filling or voiding. Despite years of research, the cause of IC/BPS remains elusive and treatment strategies are unable to provide complete relief to patients. In order to study nervous system contributions to the condition, many animal models have been developed to mimic the pain and symptoms associated with IC/BPS. One such murine model is urinary bladder distension (UBD). In this model, compressed air of a specific pressure is delivered to the bladder of a lightly anesthetized animal over a set period of time. Throughout the procedure, wires in the superior oblique abdominal muscles record electrical activity from the muscle. This activity is known as the visceromotor response (VMR) and is a reliable and reproducible measure of nociception. Here, we describe the steps necessary to perform this technique in mice including surgical manipulations, physiological recording, and data analysis. With the use of this model, the coordination between primary sensory neurons, spinal cord secondary afferents, and higher central nervous system areas involved in bladder pain can be unraveled. This basic science knowledge can then be clinically translated to treat patients suffering from IC/BPS.

Approximately 3-8 million people in the United States suffer from interstitial cystitis/bladder pain syndrome (IC/BPS), a debilitating condition characterized in part by pelvic pain. In order to study nervous system contributions to the condition, a physiological model of urinary bladder pain is used in mice and rats.

Approximately 3-8 million people in the United States suffer from interstitial cystitis/bladder pain syndrome (IC/BPS), a debilitating condition ...

Bladder Smooth Muscle Strip Contractility as a Method to Evaluate Lower Urinary Tract Pharmacology

We describe an in vitro method to measure bladder smooth muscle contractility, and its use for investigating physiological and pharmacological properties of the smooth muscle as well as changes induced by pathology. This method provides critical information for understanding bladder function while overcoming major methodological difficulties encountered in in vivo experiments, such as surgical and pharmacological manipulations that affect stability and survival of the preparations, the use of human tissue, and/or the use of expensive chemicals. It also provides a way to investigate the properties of each bladder component (i.e. smooth muscle, mucosa, nerves) in healthy and pathological conditions.
The urinary bladder is removed from an anesthetized animal, placed in Krebs solution and cut into strips. Strips are placed into a chamber filled with warm Krebs solution. One end is attached to an isometric tension transducer to measure contraction force, the other end is attached to a fixed rod. Tissue is stimulated by directly adding compounds to the bath or by electric field stimulation electrodes that activate nerves, similar to triggering bladder contractions in vivo. We demonstrate the use of this method to evaluate spontaneous smooth muscle contractility during development and after an experimental spinal cord injury, the nature of neurotransmission (transmitters and receptors involved), factors involved in modulation of smooth muscle activity, the role of individual bladder components, and species and organ differences in response to pharmacological agents. Additionally, it could be used for investigating intracellular pathways involved in contraction and/or relaxation of the smooth muscle, drug structure-activity relationships and evaluation of transmitter release.
The in vitro smooth muscle contractility method has been used extensively for over 50 years, and has provided data that significantly contributed to our understanding of bladder function as well as to pharmaceutical development of compounds currently used clinically for bladder management.

This manuscript presents a simple, yet powerful, in vitro method for evaluating smooth muscle contractility in response to pharmacological agents or nerve stimulation. Main applications are drug screening and understanding tissue physiology, pharmacology,&#160;and pathology.

We describe an in vitro method to measure bladder smooth muscle contractility, and its use for investigating physiological and pharmacological properties ...

Nerve-sparing Mid-urethral Obstruction (NeMO) in Female Small Rodents

Partial bladder outlet obstruction (pBOO) has a high prevalence, causes significant patient burden, and immense health care costs. The most common animal model to investigate bladder remodeling in pBOO are female rodents undergoing partial obstruction at the proximal urethra. Variability in the degree of obstruction and animal mortality are major concerns with proximal obstruction. Furthermore, dissecting around the proximal urethra and bladder neck jeopardizes bladder innervation.
We developed a nerve-sparing mid-urethral obstruction (NeMO) model for pBOO avoiding the disadvantages of the traditional model. We approached the urethra just inferior to the pubic symphysis, which obviated the need for laparotomy as well as for dissection in this area; also, the striated urethral sphincter remained untouched. We performed NeMO in female Sprague-Dawley rats (12 obstructions, 6 sham animals) as well as in female C57/bl6 mice (20 obstructions, 18 sham animals). After two weeks, we evaluated bladder function, bladder mass, and body mass.
We had no mortalities among obstructed- or sham-operated female rats; as described for the traditional proximal pBOO-method, we tied the suture around the proximal urethra and a temporarily placed 0.9 mm metal rod. NeMO induced an 85% increase in bladder mass after two weeks, average residual urine volume was 0.4 mL in partially obstructed rats while only 0.03 mL in sham animals. In mice, we tested 3 sizes of cannulas that we placed along the urethra when tying the suture. We found that using a 27-gauge cannula resulted in over 50% animal mortality; placing the 25-gauge cannula did not yield the desired response in increasing bladder mass; utilizing a 26-gauge cannula yielded favorable results with minimal animal mortality (1/8) yet a significant 2-fold increase in bladder mass.

Nerve-sparing Mid-urethral Obstruction NeMO in Female Small Rodents

Traditional modeling of partial bladder outlet obstruction in rodents is fraught with animal mortality. A denervation injury from dissection around the proximal urethra and bladder neck is also of major concern. We developed and evaluated a safe and reliable mid-urethral obstruction model, avoiding the shortcomings of the traditional model.

Partial bladder outlet obstruction (pBOO) has a high prevalence, causes significant patient burden, and immense health care costs. The most common animal ...

Evaluating the Procedure for Performing Awake Cystometry in a Mouse Model

Awake filling cystometry has been used for a long time to evaluate bladder function in freely moving mice, however, the specific methods used, vary among laboratories. The goal of this study was to describe the microsurgical procedure used to implant an intravesical tube and the experimental technique for recording urinary bladder pressure in an awake, freely moving mouse. In addition, experimental data is presented to show how surgery, as well as tubing type and size, affect lower urinary tract function and recording sensitivity. The effect of tube diameter on pressure recording was assessed in both polyethylene and polyurethane tubing with different internal diameters. Subsequently, the best performing tube from both materials was surgically implanted into the dome of the urinary bladder of male C57BL/6 mice. Twelve-hour, overnight micturition frequency was recorded in healthy, intact animals and animals 2, 3, 5, and 7 days post-surgery. At harvest, bladders were assessed for signs of swelling using gross observation and were subsequently processed for pathological analysis. The greatest extent of bladder swelling was observed on day 2 and 3, which correlated with behavioral voiding data showing significantly impaired bladder function. By day 5, bladder histology and voiding frequency had normalized. Based on the literature and evidence provided by our studies, we propose the following steps for in vivo recording of intravesical pressure and voided volume in an awake mouse: 1) Perform the surgery using an operating microscope and microsurgical tools, 2) Use polyethylene-10 tubing to minimize movement artifacts, and 3) Perform cystometry on post-operative day 5, when bladder swelling resolves.

This study describes the surgical procedures and experimental techniques for performing awake cystometry in a freely moving mouse. In addition, it provides experimental evidence to support its optimization and standardization.

Awake filling cystometry has been used for a long time to evaluate bladder function in freely moving mice, however, the specific methods used, vary among ...

A Decentralized (Ex Vivo) Murine Bladder Model with the Detrusor Muscle Removed for Direct Access to the Suburothelium during Bladder Filling

Previous studies have established the release of chemical substances from flat bladder mucosa sheets affixed in Ussing chambers and exposed to changes in hydrostatic pressure or mechanical stretch and from cultured urothelial cells upon hydrostatic pressure changes, stretch, cell swelling, or drag forces, and in bladder lumen at end of filling. Such findings led to the assumption that these mediators are also released in suburothelium (SubU)/lamina propria (LP) during bladder filling, where they affect cells deep in the bladder wall to ultimately regulate bladder excitability. There are at least two obvious limitations in such studies: 1) none of these approaches provide direct information about the presence of mediators in SubU/LP, and 2) the stimuli used are not physiological and do not recapitulate authentic filling of the bladder. Here, we discuss a procedure that enables direct access to the suburothelial surface of the bladder mucosa in the course of bladder filling. The murine detrusor-free preparation we created closely resembles filling of the intact bladder and allows pressure-volume studies to be performed on the bladder in the absence of confounding signaling from spinal reflexes and detrusor smooth muscle. Using the novel detrusor-free bladder model, we recently demonstrated that intravesical measurements of mediators cannot be used as a proxy to what has been released or present in the SubU/LP during bladder filling. The model enables examination of urothelium-derived signaling molecules that are released, generated by metabolism and/or transported into the SubU/LP during the course of bladder filling to transmit information to neurons and smooth muscle of the bladder and regulate its excitability during continence and micturition.

A Decentralized Ex Vivo Murine Bladder Model with the Detrusor Muscle Removed for Direct Access to the Suburothelium during Bladder Filling

The detrusor-free bladder model enables direct access to the suburothelium to study local mechanisms for regulation of biologically active mediator availability in suburothelium/lamina propria during storage and voiding of urine. The preparation closely resembles filling of an intact bladder and allows pressure-volume studies to be performed without systemic influences.

Previous studies have established the release of chemical substances from flat bladder mucosa sheets affixed in Ussing chambers and exposed to changes in ...

Cystometric and External Urethral Sphincter Measurements in Awake Rats with Implanted Catheter and Electrodes Allowing for Repeated Measurements

Lower urinary tract function is mainly assessed by means of cystometric bladder function analysis in rodents. Conventional cystometries are usually performed as terminal analysis under urethane anesthesia. It is well known that anesthetic drugs can influence bladder function. Hence, the aim of this technique is to perform cystometric measurements of the urinary bladder and external urethral sphincter in lightly restrained awake rats. For this purpose, a bladder catheter is implanted into the bladder dome. Subsequently, two electrodes are implanted bilateral to the external urethral sphincter and a ground electrode is sutured to a non-responsive skeletal muscle. The bladder catheter and the three electrodes are finally tunneled subcutaneously to the neck region and affixed to a harness. With this technique, the lower urinary tract can be measured at multiple time points in the same animal to assess lower urinary tract function. The main application of this technique is the follow-up of simultaneous urinary bladder and external urethral sphincter function in awake healthy rats and after induction of a disease or injury. Moreover, subsequent lower urinary tract monitoring can be performed during evaluation of the disease/injury and to monitor treatment efficacy.

This protocol first describes the surgical procedure of the permanent implantation of a urinary bladder catheter combined with external urethral sphincter electrodes, and second, the measurement of the function of the urinary bladder and external urethral sphincter in implanted awake animals.

Lower urinary tract function is mainly assessed by means of cystometric bladder function analysis in rodents. Conventional cystometries are usually ...

Biology

Urethral Stricture Induction Followed by Buccal Mucosa Graft Urethroplasty in a Rat Model

Urethral reconstruction is an important area of expertise for urologists. The buccal mucosa is considered the best option when urethral grafting is necessary, although in some cases, it is inappropriate or needs to be optimized to repair a given stricture. Therefore, developing innovative procedures and evaluating their putative success in experimental models is crucial to fit the clinical need. With this goal, this study describes a protocol in which urethral stricture was induced by electrocautery in Wistar rats. Urethral reconstruction was performed 1 week later with a buccal mucosa graft, harvested from the lower lip, and placed in a ventral onlay fashion. A retrograde urethrogram showed a significant improvement in urethral diameter after urethroplasty compared to the respective value after stricture induction. Additionally, the graft placement was assessed by blood perfusion analysis using laser Doppler. As expected, a dark blue area corresponded to the non-vascularized buccal mucosa graft. This procedure can successfully simulate the normal pathophysiological process of urethral injury and tissue modulation, as well as urethral reconstruction using a buccal mucosa graft in a reproducible manner, and serve as the basis for future research based on tissue engineering or urethral grafts.

In the present protocol, a urethral stricture induction was developed in Wistar rats, followed by urethral reconstruction with a buccal mucosa graft. A retrograde urethrogram and laser Doppler assessment were performed, validating urethral reconstruction (after stricture formation) and graft placement.

Urethral reconstruction is an important area of expertise for urologists. The buccal mucosa is considered the best option when urethral grafting is ...

Efficient Rat Model for Urethral Stricture: Electric Knife Method

Iatrogenic Injury Recapitulated: Electroexcision Technique for Urethral Stricture Modeling in Rats

Urethral stricture (US) is a common clinical condition in urology, characterized by high prevalence and morbidity across all ages. Current treatments for US, such as urethral dilatation and internal urethrotomy, fail to fully resolve the condition and are associated with high rates of recurrence and complications. 
Additionally, the pathogenesis of US is not well understood. To explore the pathogenesis of US and develop new therapeutic strategies, it is crucial to establish a standardized rat model that accurately reflects the clinical manifestations. This study outlines a straightforward and repeatable method for inducing US in rats using a high-frequency electric knife. The method involves making a longitudinal incision with the electric knife set to a unipolar mixed cutting mode at 4 W, which inflicts significant urethral damage. Histopathological analysis shows thickening of the urothelium, inflammatory infiltration, and disorganized collagen fibers. This model effectively replicates iatrogenic injury through electroexcision in the rat urethra. In summary, this study successfully establishes a new, efficient, and stable rat model of US that closely mimics the clinical scenario, providing a valuable tool for further research into the mechanisms and novel treatments for US.

In this study, we present a novel, efficient, and stable rat model of urethral stricture created through electroexcision of the rat urethra, which effectively simulates iatrogenic injury observed in clinical settings.

Urethral stricture (US) is a common clinical condition in urology, characterized by high prevalence and morbidity across all ages. Current treatments for ...

Detrusor Underactivity Model in Rats by Conus Medullaris Transection

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