Lower urinary tract dysfunction (LUTD) occurs as a complication of pelvic surgery. Pelvic nerve injury is known to cause LUTD such as an underactive bladder; however, the consequences of hypogastric nerve injury remain unknown. On the other hand, a recent review reported that stem cell transplantation is effective in the treatment of LUTD. [1] However, there are many hurdles in stem cell therapy such as complicated handling of cells, high risk of immune response, and high cost, among others. In addition, many reports have suggested that the improvements following stem cell therapy are due to the paracrine effects such as growth factors or cytokines from the cells, and not the differentiation ability of the stem cells.[1] We focused on the contents of stem cells, which have the potential to solve these problems. In this study, we investigated the effectiveness of filtered bone marrow-derived stem cell lysate (FBMSCL) in a model of overflow urinary incontinence caused by bilateral hypogastric nerve injury.

We collected bone marrow stem cells (BMSC) and diluted in phosphate-buffered saline (PBS) (1×10⁶ cells/1 mL PBS).Subsequently, the cells were crushed by freeze-thaw method and the filtrate (FBMSCL) was collected. Seven- and eight-week-old male Wistar-ST rats were categorized into (1) Sham+PBS (n=7), (2) hypogastric nerve injury (HGNI) +PBS (n=10), and (3) HGNI+FBMSCL (n=10) groups. Bilateral hypogastric nerves were injured by pinching with reverse acting tweezers for one minute. PBS or FBMSCL (100 μl/body) was administered intravenously. After 1 week, cystometrogram was performed, and the intercontraction intervals (ICIs), maximum voiding pressure (MP), baseline, and threshold values were evaluated in each group. Bladder weight and morphology were evaluated by Masson trichrome staining. Statistical analyses were performed using ANOVA and Bonferroni multiple t-tests.

Representative charts are shown in Figure 1A. In the HGNI+PBS group, all rats presented with symptoms of overflow urinary incontinence. Peaks of intravesical pressure were not observed in seven of ten rats. In the HGNI+FBMSCL group, only three of ten rats presented with symptoms of overflow urinary incontinence. Peaks of intravesical pressure were not observed in seven of ten rats. ICIs in the HGNI+PBS group were significantly longer than that in the Sham+PBS group (P<0.01). The ICIs in the HGNI+FBMSCL group were significantly shorter than that in the HGNI+PBS group (P<0.05) (Figure 1B). MP, baseline, and threshold did not change among the three groups (Figure 1B). The bladder weight/body ratio of rats in the HGNI+PBS group was significantly higher than that in the Sham+PBS group (P<0.01), while that of the HGNI+FBMSCL group was significantly lower than in the HGNI+PBS group (P<0.01). Images of the stained bladder body of the three groups are shown in Figure 2A. The observations signified thinning and enlargement of the bladder body due to HGNI. The fibrotic area/total area ratio in the HGNI+PBS group was higher than that in the Sham+PBS group, while that of the HGNI+FBMSCL group was lower than in the HGNI+PBS group (Figure 2B).

Rats with HGNI exhibited overflow incontinence and prolonged urination interval. The hypogastric nerve is known to control the function of the bladder neck and urethra [2]; therefore, LUTD in this study could be attributed to impairment of function due to injury of the nerve. In this study, FBMSCL improved urinary function, suggesting that it might be involved in the repair of nerve injury. This functional improvement might prevent bladder fibrosis.

FBMSCL improved overflow urinary incontinence in rats, caused by injury to the hypogastric nerve, suggesting that intravesical injection of FBMSCL may be useful in the treatment of neurogenic bladder.

Sun DZ, et al. Harnessing the mesenchymal stem cell secretome for regenerative urology. Nat Rev Urol. 2019;16(6):363-37.5.
Hehemann M, et al. Pelvic and hypogastric nerves are injured in a rat prostatectomy model, contributing to development of stress urinary incontinence. Sci Rep. 2018;8(1):16432.