Rat animal model for preclinical testing of microparticle urethral bulking agents.

OBJECTIVES: To develop an economic, practical and readily available animal model for preclinical testing of urethral bulking therapies, as well as to establish feasible experimental methods that allow for complete analysis of hard microparticle bulking agents. METHODS: Alumina ceramic beads suspended in hyaluronic acid were injected into the proximal urethra of 15 female rats under an operating microscope. We assessed overall lower urinary tract function, bulking material intraurethral integrity and local host tissue response over time. Microphotographs were taken during injection and again 6 months postoperatively, before urethral harvest. Urinary flow rate and voiding frequency were assessed before and after injection. At 6 months, the urethra was removed and embedded in resin. Hard tissue sections were cut using a sawing microtome, and processed for histological analysis using scanning electron microscopy, light microscopy and immunohistochemistry. RESULTS: Microphotographs of the urethra showed complete volume retention of the bulking agent at 6 months. There was no significant difference between average urinary frequency and mean urinary flow rate at 1 and 3 months postinjection as compared with baseline. Scanning electron microscopy proved suitable for evaluation of microparticle size and integrity, as well as local tissue remodeling. Light microscopy and immunohistochemistry allowed for evaluation of an inflammatory host tissue reaction to the bulking agent. CONCLUSIONS: The microsurgical injection technique, in vivo physiology and novel hard tissue processing for histology, described in the present study, will allow for future comprehensive preclinical testing of urethral bulking therapy agents containing microparticles made of a hard material.

Comparison of intraprostatic ethanol diffusion using a microporous hollow fiber catheter versus a standard needle.

PURPOSE: Transurethral intraprostatic ethanol chemoablation of the prostate has shown promising preliminary clinical results for benign prostatic hyperplasia with some variability in clinical outcome. This is likely due to the uneven prostate diffusion caused by varying resistance of the tissue type in which the tip of the needle is embedded. We examined whether the distribution of the injectable in the canine prostate could be improved using a microporous hollow fiber catheter (Twin Star Medical, Minneapolis, Minnesota). MATERIALS AND METHODS: The prostate was exposed in 9 mongrel dogs. A single injection of 98% ethanol was delivered in each lobe using a microporous hollow fiber catheter and a standard needle. Prostates were harvested and fixed in 10% formalin. After injection 2.5 mm step sections were obtained and scanned. The ethanol induced tissue lesions were traced on hematoxylin and eosin sections. Three-dimensional reconstructions were created and the volume of each prostate lesion was calculated using stereology. RESULTS: Ethanol induced tissue changes were seen bilaterally in 8 of 9 ethanol injected prostates. In all cases the lesion created by microporous hollow fiber catheter injection was larger than that in the contralateral lobe injected with the control needle. When data were pooled, the hollow fiber catheter injection produced significantly greater tissue changes than the control needle injection (p = 0.03). CONCLUSIONS: Improved distribution and absent backflow were seen when using the microporous hollow fiber catheter, supporting its potential as a new method to treat prostate disease.

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.

Novel Bioceramic Urethral Bulking Agents Elicit Improved Host Tissue Responses in a Rat Model.

Objectives. To test the physical properties and host response to the bioceramic particles, silica-calcium phosphate (SCPC10) and Cristobalite, in a rat animal model and compare their biocompatibility to the current clinically utilized urethral bulking materials. Material and Methods. The novel bulking materials, SCPC10 and Cristobalite, were suspended in hyaluronic acid sodium salt and injected into the mid urethra of a rat. Additional animals were injected with bulking materials currently in clinical use. Physiological response was assessed using voiding trials, and host tissue response was evaluated using hard tissue histology and immunohistochemical analysis. Distant organs were evaluated for the presence of particles or their components. Results. Histological analysis of the urethral tissue five months after injection showed that both SCPC10 and Cristobalite induced a more robust fibroblastic and histiocytic reaction, promoting integration and encapsulation of the particle aggregates, leading to a larger bulking effect. Concentrations of Ca, Na, Si, and P ions in the experimental groups were comparable to control animals. Conclusions. This side-by-side examination of urethral bulking agents using a rat animal model and hard tissue histology techniques compared two newly developed bioactive ceramic particles to three of the currently used bulking agents. The local host tissue response and bulking effects of bioceramic particles were superior while also possessing a comparable safety profile.