Login to Access Video or Poster Abstract: MP42-06
Sources of Funding: Ana Coelho is supported by an individual post-doc fellowship from Fundacao para a Ciencia e Tecnologia (SFRH/BPD/108468/2015). This work was financed by FEDER funds through COMPETE 2020, Operacional Programme for Competitiveness and Internationalisation (POCI) and Portugal 2020 under the framework of the project "Institute for Research and Innovation in Health Sciences" (POCI-01-0145-FEDER-007274).

Introduction

The urethral epithelium is deeply involved in the control of lower urinary tract functioning. Key elements of this process may be paraneuronal cells located among urethral epithelium that act as local sensors and influence urethral function through a putative paracrine mechanism. This work aimed to explore the expression of serotonin (5-HT) paraneuronal cells in human and rodent urethra in normal and pathological conditions as well as the contribution of 5-HT to the urethral function.

Methods

Female urethras were collected from human organ donors and rats and processed for immunohistochemistry (IHC). Antibodies against 5-HT, the pan-neuronal marker Beta3-Tubulin, calcitonin gene-related peptide (CGRP), vesicular acetylcholine transporter (VAChT) and the synaptic vesicle 2 (SV2) were used. Female urethras from rats with lypopolyshaccaride (LPS, 5 mg/ml) -induced inflammation or chronic spinal cord transection (SCT) at T8/T9 were also collected and processed for IHC or 5-HT quantification by HPLC. Bladder reflex activity of normal rats was evaluated by cistometry during infusion of 5-HT (1 mM).

Results

In human and rat urethra, cells expressing 5-HT were detected along the entire length of the urethral epithelium. These cells had a long thin extension reaching the urethral surface and stained for Beta3-Tubulin and SV2 confirming the paraneuronal function. Underneath the epithelium, a dense neuronal network contained cholinergic (VAChT+) and sensory (CGRP+) fibers. Appositions between CGRP fibers and the basal aspect of 5-HT paraneurons were observed. In inflamed rats the number of 5-HT paraneurons was significantly decreased when compared to intact animals (181,3+/-7,80 to 117,1+/-10,35; p?0.01). Accordingly, 5-HT levels measured by HPLC analysis were decreased (15,36+/-2,81 to 7,45+/-0,42; p?0.01). In SCT rats the number of 5-HT paraneurons was markedly increased (152,3+/-14,82 to 208,8+/-18,8; p?0.01). During 5-HT infusion in intact rats the frequency of voiding contractions was unaltered, however, maximal detrusor pressure was increased over controls (50,79+/-7.906 over 33,52+/-0,830; p?0.01) suggesting an increase in urethral resistance to flow.

Conclusions

Paraneurons are strongly expressed in the human and rat urethral epithelium exhibiting close contacts with sensory neurons and in close proximity to cholinergic fibers. The expression of 5-HT paraneurons is influenced by inflammation and neurogenic bladder dysfunction. The release of 5-HT from these cells might increase urethral resistance and may contribute to continence regulation.

Funding

Ana Coelho is supported by an individual post-doc fellowship from Fundacao para a Ciencia e Tecnologia (SFRH/BPD/108468/2015). This work was financed by FEDER funds through COMPETE 2020, Operacional Programme for Competitiveness and Internationalisation (POCI) and Portugal 2020 under the framework of the project "Institute for Research and Innovation in Health Sciences" (POCI-01-0145-FEDER-007274).