Testosterone and 17β-estradiol induce glandular prostatic growth, bladder outlet obstruction, and voiding dysfunction in male mice

Abstract

Benign prostatic hyperplasia (BPH) and bladder outlet obstruction (BOO) are common in older men and can contribute to lower urinary tract symptoms that significantly impact quality of life. Few existing models of BOO and BPH use physiological levels of hormones associated with disease progression in humans in a genetically manipulable organism. We present a model of BPH and BOO induced in mice with testosterone (T) and 17β-estradiol (E(2)). Male mice were surgically implanted with slow-releasing sc pellets containing 25 mg T and 2.5 mg E(2) (T+E(2)). After 2 and 4 months of hormone treatment, we evaluated voiding patterns and examined the gross morphology and histology of the bladder, urethra, and prostate. Mice treated with T+E(2) developed significantly larger bladders than untreated mice, consistent with BOO. Some mice treated with T+E(2) had complications in the form of bladder hypertrophy, diverticula, calculi, and eventual decompensation with hydronephrosis. Hormone treatment caused a significant decrease in the size of the urethral lumen, increased prostate mass, and increased number of prostatic ducts associated with the prostatic urethra, compared with untreated mice. Voiding dysfunction was observed in mice treated with T+E(2), who exhibited droplet voiding pattern with significantly decreased void mass, shorter void duration, and fewer sustained voids. The constellation of lower urinary tract abnormalities, including BOO, enlarged prostates, and voiding dysfunction seen in male mice treated with T+E(2) is consistent with BPH in men. This model is suitable for better understanding molecular mechanisms and for developing novel strategies to address BPH and BOO.

Fig. 1.

Effects of T+E₂ treatment on the urinary tract of male C57BL/6 mice. A, After 2 months of treatment with T+E₂, the bladder was somewhat enlarged and contained residual urine compared with the small, deflated bladder of the untreated (UNT) mouse at the time of euthanasia. High-magnification H&E-stained sections (bottom panels) of representative mice revealed increased detrusor thickness after 2 months of T+E₂ treatment. Four months of treatment with T+E₂ caused very large bladders distended with large amounts of residual urine. After 4 months of T+E₂ treatment, the bladder was distended with marked thinning of the detrusor seen with H&E staining. Bl, Bladder; SV, seminal vesicles. B, After 4 months of T+E₂ treatment, some mice had bladder diverticula (red arrows) and hydronephrosis (middle panel), indicating increased intravesical pressure relative to pressure of the ureters and renal pelves. Irregular bladder calculi were occasionally found (right panel), indicating urinary stasis in the setting of obstruction. C, Male mice were untreated or treated with T+E₂ for 2 and 4 months, and bladders were processed and stained with Masson's trichrome stain (cells stain red and collagen stains blue). After 2 months of treatment, bladders from T+E₂-treated mice showed increased collagen staining (blue), whereas very little collagen was observed in untreated normal bladders. After 4 months of hormone treatment, layers of disorganized collagen had mostly replaced the thinned detrusor. D, Localization of smooth muscle ACTA2 and MYH11 in serial sectioned bladders collected from untreated and T+E₂-treated male mice at 2 and 4 months. After T+E₂ treatment for 2 months, both smooth muscle markers (red) stained intensely and were found throughout the thickened detrusor relative to untreated bladders, indicating detrusor hypertrophy. After 4 months of T+E₂-treatment, when distended bladders were observed, very little smooth muscle marker staining was present. This is consistent with the trichrome staining in C where cells (red) are primarily found in the urothelium and the stroma is rich with collagen (blue) but contains few red stained cells. *, Bladder lumen.

Fig. 2.

T+E₂ treatment of C57BL/6 mice causes urethral narrowing, increased anterior prostate mass, and increased prostatic ducts in the proximal urethra. A, Measurements were contoured by hand in ImageJ to determine the cross-sectional area of the urethral lumen (blue). B, Mice treated with T+E₂ for 4 months had a significantly smaller average cross-sectional area of the prostatic urethral lumen compared with untreated controls (**, P = 0.004). C, Compared with untreated mice, the mass of the anterior prostate from mice treated with T+E₂ for 4 months was significantly greater (***, P < 0.0001). D, Mice treated for 4 months with T+E₂ had significantly more prostatic ducts in the proximal urethra compared with untreated controls (*, P = 0.015). E, Prostatic ducts were counted in a representative section of the prostatic urethra, and untreated mice (left) were compared with mice treated with T+E₂ for 4 months (right). Prostate cancer and prostatic intraepithelial neoplasia were not observed in the urethra.*, Prostatic ducts, ED, ejaculatory ducts; SVD, main seminal vesicle ducts; UL, urethral lumen.

Fig. 3.

Treatment of male BALB/c mice with T+E₂ causes voiding dysfunction in the form of droplet voiding pattern. A, Representative uroflow session with net mass on balance recorded over time from an untreated mouse (UNT; blue) compared with a mouse treated with T+E₂ (red). The untreated mouse exhibits three sustained voids. The mouse treated with T+E₂ has frequent small-mass, short-duration voids. Analysis of a synchronized video stream determined the voiding events in the mouse treated with T+E₂ consist of a droplet of urine striking the balance (droplet voiding pattern). B–D, Median uroflow curves reflecting all voids across all sessions from 2–4 months of hormone treatment for all mice in the study (individual lines represent individual mice). B, Four untreated mice show median uroflow curves consistent with sustained voiding pattern. C, Four mice treated with T+E₂ have median uroflow curves, reflecting sustained voiding pattern, similar to untreated mice in B. D, Among five mice treated with T+E₂, median uroflow curves reflect droplet voiding pattern.

Fig. 4.

Urinary voiding events across all sessions are plotted by void mass (grams) and void duration (seconds) for each BALB/c mouse (each dot represents a void). A, Individual voiding profiles show sustained voiding pattern in untreated (UNT) mice. B, Individual voiding profiles for four of nine mice treated with T+E₂ show a combination of sustained voiding and droplet voiding pattern, although some mice display sustained voids similar in duration and mass to untreated mice. C, Five of nine mice treated with T+E₂ demonstrate predominantly droplet voiding pattern.