Urodynamic and molecular characteristics of detrusor underactivity in a rat cryoinjury model and effects of low energy shock wave therapy

Abstract

Aims: Low energy shock wave (LESW) has been shown to facilitate tissue regeneration and reduce inflammation. We investigated the effects of LESW in an underactive (DU) model induced by cryoinjury of rat detrusor.

Methods: Forty-six female Sprague-Dawley rats were divided into sham, cryoinjury with or without LESW (0.12 mJ/mm² ; 200 pulses). Under halothane anesthesia, a low midline incision was made and a cryoinjury of detrusor was induced by placing an aluminum rod (chilled with dry ice) for 30 s on the serosal side of the bladder filled with 1 mL sterile saline bilaterally. Awake cystometrogram (CMG), molecular and histopathology studies were performed on Day 8 or 15 after cryoinjury.

Results: Significant urodynamic, histological, and molecular changes induced by cryoinjury of rat detrusor were detected on Day 8 and decrease in the contraction amplitude (54.3%), a significant increase in wet bladder weight (64.1%), edematous changes, muscle thinning and downregulation of α-SMA, IL-6, and upregulation of COX-2. LESW reversed the cryoinjury induced histological and COX-2 expression to cause a 49.0% increase in the contraction amplitude (P < 0.05). LESW induced cell proliferation was revealed by increased CD31 and Ki67 immunostaining. The effect of cryoinjury on urodynamic and histological changes was maintained till Day 15.

Conclusion: The cryoinjury of rat detrusor models myogenic DU, which is partially reversed by LESW. LESW may afford a simple, non-invasive modality to facilitate tissue regeneration and improve voiding function in myogenic detrusor underactivity.

Keywords: cryoinjury; detrusor underactivity; shock wave.