Neurobiology of stress urinary incontinence: New insights and implications for treatment

Bladder outlet physiology in the context of lower urinary tract dysfunction

Physiological function of the bladder outlet is complex and symptomatic consequences can result from outlet dysfunction. Within the outlet, smooth, and skeletal muscles constitute the contractile apparatus, but additional cell types include interstitial cells and neuroendocrine cells, and various transmitters are present in the innervation, raising the possibility of unrecognized functional subtleties. Key outlet functions are; maintained closure for urine storage, increased closure (guarding) during exertion, sustained opening for voiding, transient opening for territorial marking in animals and orthograde male ejaculation. These are co-ordinated by several spinal and higher CNS centers, with overlap of the somatic, sympathetic and parasympathetic nervous systems. During voiding, urethral afferents may be important in maintaining detrusor contraction until completion of bladder emptying. Some of the bladder outlet afferents may be shared with the anal sphincter. Dysfunction of the outlet leads to conditions such as retrograde ejaculation, Fowler's syndrome, and detrusor sphincter dyssynergia. Urethral relaxation during urine storage may lead to urinary urgency, which may be misleadingly labeled as overactive bladder. Research priorities are numerous, including; peripheral cellular integrative physiology, interactions with other pelvic organs, interconnectivity of the CNS centers at all levels of the neuraxis, and standardized animal models of outlet functions such as reflex-driven voiding.

Periurethral injection of autologous adipose-derived stem cells with controlled-release nerve growth factor for the treatment of stress urinary incontinence in a rat model

BACKGROUND

Stem cell therapy is a promising therapeutic strategy for stress urinary incontinence (SUI). However, its current efficacy is insufficient.

OBJECTIVE

We designed a stem cell transplantation system that contains autologous adipose-derived stem cells (ADSC) and controlled-release nerve growth factor (NGF). We evaluated whether this system could enhance the therapeutic efficacy of ADSCs by periurethral coinjection in SUI rats.

DESIGN, SETTING, AND PARTICIPANTS

We first tested for the presence of NGF receptors in rat ADSCs and observed the effect of NGF on ADSCs in vitro and in vivo. NGF was encapsulated within poly(lactic-co-glycolic acid-PLGA) microspheres (PLGA/NGF) to control its release. SUI was created in rats, and ADSCs were harvested, cultured from fat tissue, and retained for later transplantation. SUI rats then received different forms of periurethral injection therapy. Their urodynamic index was monitored. Eight weeks after injection, the SUI rats were sacrificed and their urethra removed for histologic evaluation.

INTERVENTION

Forty SUI rats were allocated to five groups for receiving periurethral injection with phosphate-buffered saline (PBS), ADSC, ADSC+PLGA, ADSC+NGF, or ADSC+PLGA/NGF. Bladder capacities, abdominal leak point pressure (ALPP), and retrograde urethral perfusion pressure (RUPP) were reassessed at 2, 6, and 8 wk after injection.

MEASUREMENTS

The rat SUI model was generated by bilateral pudendal nerve transection (PNT). Real-time polymerase chain reaction (RT-PCR) and western blotting detected the NGF receptor Ark-A. The regeneration of muscles and peripheral nerves was evaluated by Masson's trichrome and immunohistochemical staining.

RESULTS AND LIMITATIONS

Results revealed the presence of the NGF receptor Trk-A on rat ADSCs. Short-term observations showed that NGF could improve ADSCs' viability in vitro and in vivo. ADSCs delivered intramuscularly into the urethra in combination with PLGA/NGF resulted in significant improvements in ALPP and RUPP as well as the amount of muscle and ganglia. There was a significant difference between the ADSC+PLGA/NGF group and other groups.

CONCLUSIONS

Periurethral coinjection of autologous ADSCs with controlled-release NGF may be a potential strategy for SUI treatment.