Treatment of stress urinary incontinence with adipose tissue-derived stem cells

Abstract

Background aims: Effective treatment for stress urinary incontinence (SUI) is lacking. This study investigated whether transplantation of adipose tissue-derived stem cells (ADSC) can treat SUI in a rat model.

Methods: Rats were induced to develop SUI by postpartum vaginal balloon dilation and bilateral ovariectomy. ADSC were isolated from the peri-ovary fat, examined for stem cell properties, and labeled with thymidine analog BrdU or EdU. Ten rats received urethral injection of saline as a control. Twelve rats received urethral injection of EdU-labeled ADSC and six rats received intravenous injection of BrdU-labeled ADSC through the tail vein. Four weeks later, urinary voiding function was assessed by conscious cystometry. The rats were then killed and their urethras harvested for tracking of ADSC and quantification of elastin, collagen and smooth muscle contents.

Results: Cystometric analysis showed that eight out 10 rats in the control group had abnormal voiding, whereas four of 12 (33.3%) and two of six (33.3%) rats in the urethra-ADSC and tail vein-ADSC groups, respectively, had abnormal voiding. Histologic analysis showed that the ADSC-treated groups had significantly higher elastin content than the control group and, within the ADSC-treated groups, rats with normal voiding pattern also had significantly higher elastin content than rats with voiding dysfunction. ADSC-treated normal-voiding rats had significantly higher smooth muscle content than control or ADSC-treated rats with voiding dysfunction.

Conclusions: Transplantation of ADSC via urethral or intravenous injection is effective in the treatment and/or prevention of SUI in a pre-clinical setting.

Fig. 1. Cytometric analysis of rat ADSCs

ADSCs were isolated from peri-ovary fat pads, allowed to attach to plastic dishes, expanded through one passage, and then harvested for flow cytometric analysis for the indicated markers. Percent of positive cells is shown in the right lower corner of each plot.

Fig. 2. Determination of urinary continence by 4-channel conscious cystometric analysis

(A) Normal micturition patterns were defined as pressure increases resulting in voiding with a frequency of ≤ 4 times in 10 min. (B) Abnormal voiding patterns were defined as continuous or intermittent urine leakage at low bladder pressure during the filling phase.

Fig. 3. Cystometric analysis results

“Control” indicates rats treated with PBS. “ADSC-TI” and “ADSC-UI” are rats injected with ADSCs in the tail vein and urethra, respectively. (A) Comparison of percent of rats with abnormal voiding patterns. * indicates significant difference when compared to control (P<0.05). (B) Comparison of baseline bladder pressure. # indicates insignificant difference when compared to control (P>0.05). (C) Comparison of leak point pressure. * indicates significant difference when compared to control (P<0.05).

Fig. 4. Tracking of transplanted ADSCs and identification of SDF-1 expression in the urethra

(A) ADSCs were labeled with BrdU and autologously injected into the tail vein. Four weeks later, the urethra was harvested and stained for BrdU (Brown). Boxed area in the top photograph (×100) is enlarged and shown in the bottom photograph (×400). (B) The same urethra tissue samples were also stained for SDF-1 (Brown). Boxed area in the top photograph (×100) is enlarged and shown in the bottom photograph (×400). (C) ADSCs were labeled with EdU and autologously injected into the bladder neck, which was then harvested at 4w and stained with Alexa-594 (red fluorescence), DAPI (blue fluorescence), and anti-α-SMA antibody (green fluorescence). The stained images were digitally merged. (D) ADSCs were labeled and transplanted as in panel C. Boxed areas in the 400× graphs are shown in the corresponding 1000× graphs.

Fig. 5. Assessment of muscle, collagen, and elastin contents in the urethra

“Control” indicates rats treated with PBS. “ADSC-treated” indicates rats injected with ADSCs in the tail vein or urethra. “Normal” and “Abnormal” indicate micturition patterns identified by cystometric analysis. The urethras of all 28 rats were stained for elastin and α-SMA. They were also stained by the trichrome method to determine the muscle/collagen ratio (Table 1). Representative photographs shown here were originally taken at 20× magnification.