Abstract: PD70-04
Sources of Funding: This work was funded by a grant from the NIH Common Fund - SPARC program, U18EB021793 to RG. McDonnell Center for Cellular and Molecular Neurology Postdoctoral Fellowship supported AM.

Introduction

Millions of people in the United States suffer from bladder dysfunction and pain caused by interstitial cystitis/bladder pain syndrome and overactive bladder. The underling pathologies for many of these diseases are poorly understood. To better delineate the role of sensory nerve fibers in bladder function, we have utilized optogenetics to spatially and temporally control bladder afferent activity.

Methods

Optogenetics involves the use of optically activatable pumps, channels or receptors (opsins) expressed in neurons to modulate their activity. We crossed mice expressing the Cre-dependent genes for the excitatory opsin channelrhodopsin-2 (ChR2) and the inhibitory archaerhodopsin (Arch) with mice that express Cre recombinase in Nav 1.8 or TRPV1 populations to restrict expression to nociceptive neurons (TRPV1-ChR2 and Nav 1.8-Arch). These opsins were activated be either blue (ChR2) or green (Arch) laser or LED illumination of the bladder. We then measured the influence of opsin activation on bladder function using continuous infusion cystometry. In order to translate this into a more clinically relevant gene delivery system, bladder wall injection of herpes simplex viral vector (HSV) with a pan-neuronal promotor controlling expression of ChR2 or Arch were used in rats.

Results

In TRPV1-ChR2 mice, ChR2 activation with blue light resulted in voiding events in a half full bladder that increased in magnitude with increase of light intensity. Activation of Arch with green light could delay regular cystometric contractions in Nav 1.8-Arch mice. In rats transduced with HSV-ChR2, we were able to evoke voiding events with ChR2 activation by blue light illumination of the bladder, after less filling than under normal conditions (non-stimulated). These effects were not seen in rats injected with the control viral vector, HSV-eYFP. Finally, illumination of the bladder with green light delayed regular cystometric contractions in rats injected with HSV-Arch but not in animals injecting with HSV-eYFP.

Conclusions

Here we demonstrate bidirectional modulation of bladder function using optogenetics.. This bidirectional control of bladder function can be induced by selective targeting of nociceptive afferents. Further restriction of opsin expression to specific populations of bladder sensory fibers could lead to a better understanding of their role in bladder function and disease. The refinement of virally delivery methods for optogenetic proteins, together with the development of medical devices for light delivery could lead to development of future therapies for bladder dysfunction.

Funding

This work was funded by a grant from the NIH Common Fund - SPARC program, U18EB021793 to RG. McDonnell Center for Cellular and Molecular Neurology Postdoctoral Fellowship supported AM.