Login to Access Video or Poster Abstract: MP31-02
Sources of Funding: NIH DK088836

Introduction

MicroRNAs (miRs) are involved in the post-transcriptional regulation of gene expression, and there is growing evidence for their pathological role in overactive bladder (OAB). We recently reported on the perturbed expression of miR-132 in acetic acid induced bladder overactivity (BO). Here, we investigate the functional significance of miR-132 overexpression in bladder and its effect on acetylcholinesterase (AChE) and other target genes in absence of acetic acid exposure.

Methods

Under isoflurane anesthesia, adult female Sprague-Dawley rats were either given bladder wall injection of either 10µg of plasmid vector pLV-[hsa-mir-132] or reporter plasmid encoding luciferase gene complexed with protamine and liposomes in a volume of 80µl. Bladder wall injection was performed at 4 separate sites (20 µL at each anterior, posterior and bilateral) with a 30-gauge needle. 7 days after transfection, transurethral open cystometry under urethane anesthesia ( 1g/kg s.c) was performed and harvested bladder was weighed prior to bladder strip contractility, histology and quantitative real time PCR analysis for AChE, Nerve growth factor (NGF), connexin-43 (Cx-43), monocyte chemoattractant protein (MCP-1) and soluble intracellular adhesion molecule (sICAM-1).

Results

Bladder wall transfection of miR-132 plasmid upregulated the miR-132 expression and evoked BO in absence of acetic acid. The intercontractile interval of 22.28± 1.49 min noted in luciferase transfected group was significantly reduced to 10.5± 0.8 min, while bladder weight was raised from 118.4± 1.12mg to 146.8 ±7.66mg and so was the contractile response of strips to KCl and electric field after transfection of miR-132 plasmid(*p<0.01, n=5). These changes in miR-132 group were associated with a 3 fold downregulation of AChE, 5 fold upregulation of NGF and MCP-1, while a 2 fold upregulation of Cx 43 and sICAM-1.

Conclusions

Observed BO and bladder hypertrophy following exogenous overexpression of miR-132 demonstrate the pathological role of miR-132 in OAB. The miR-132 mediated downregulation of AChE and upregulation of Cx43 explain the enhanced detrusor strip contractility. Upregulation of NGF and chemokines by miR-132 support it as a putative mediator of communication between neural and immune cells of bladder and therefore a suitable OAB drug target.

Funding

NIH DK088836