Holmium:YAG Laser-Assisted Induction of Bladder Neck Contracture in a Rat Model

Welcome.In this video, we demonstrate a novel and reproducible rat model for bladder neck contracture, BNC, using a Holmium:YAG laser. Bladder neck contracture is a challenging fibrotic complication following transrethral surgeries. This established model provides a reliable in vivo platform to study its pathogenesis and evaluate potential therapies.

Please note that all animal experiments and procedures performed in this study were strictly approved by the Institutional Animal Care and Use Committee of Experimental Animal Welfare Ethics Committee of Beijing Institute of Traditional Chinese Medicine. Begin the procedure by carefully recording the rat's body weight using a calibrated electronic scale. Place the animal in an induction chamber and induce anesthesia with 3-4%desflurane in oxygen.

Disinfect the exposed lower abdominal skin with povidone-iodine solution, and proceed with sterile draping. For postoperative analgesia, administer a subcutaneous. Make a 3-5 centimeter midline longitudinal incision through the skin and abdominal muscle layers to enter the peritoneal cavity.

Carefully expose the bladder and proximal urethra using fine retractors or forceps, avoiding injury to internal organs. Next, insert a sterile IV cannula through the urethra into the bladder to serve as a catheter. Fill the bladder with 1 milliliter of sterile saline through the catheter to distend it.

Bluntly separate the connective tissue around the bladder neck and secure the area with a blunt probe to provide stabilization. Using micro scissors, create a 5 centimeter longitudinal incision on the anterior dome of the distended bladder. Set the Ho:YAG laser parameters to a pulse energy of 1.0 joule and a frequency of 10 hertz, yielding a total power of 10 watts.

Insert a 0.2 millimeter core laser fiber through the cystotomy, guided by the visible aiming beam. Advance the fiber tip into gentle contact with the mucosal surface at the bladder neck. Deliver the laser energy at the 9 o'clock position for 5 seconds.

Then briefly cauterize the 3 o'clock position for another 5 seconds to achieve uniform mucosal thermal injury. Remove the laser fiber and close the bladder wall incision in a watertight manner using an 8-0 absorbable monofilament suture. Instill additional sterile saline through the urethral catheter to test the repair and confirm the absence of leakage.

Close the abdominal muscle layer and the skin and layers using appropriate sutures. Finally, monitor the rat on a heating pad until it has fully recovered from anesthesia. After a four-week recovery period, the bladder neck can be harvested to evaluate the development of fibrotic contracture.

Control bladder neck appears thin and patent while laser-treated specimens show fibrotic thickening and luminal stenosis. Histological analysis reveals normal layered architecture and controls. The lesion site shows marked mucosal hyperplasia, disorganized muscularis, and extensive collagen deposition.

Adjacent tissues exhibit intermediate pathological changes. Picrosirius staining under polarized light shows an enhanced birefringent collagen signal in the lesion site, indicating mature collagen accumulation. Immunostaining reveals dense collagen I and III deposition in lesions.

Minimal expression in controls and intermediate levels in adjacent tissues. In conclusion, the Holmium:YAG laser-assisted method effectively and safely induces bladder neck contracture in a rat model. As demonstrated by our histological and immunohistomical results, the laser-treated specimens successfully mimic the pathological features of human BNC, exhibiting marked mucosal hyperplasia, luminal stenosis, and extensive collagen type I and III deposition.

This standardized approach offers a highly reproducible and valuable platform for future research into the molecular mechanisms of fibrotic strictures and the testing of novel anti-fibrotic interventions. Thank you for watching.