Ionic Mechanisms of Murine Urethral Smooth Muscle Contractility

Gupta, Neha and Drumm, Bernard (2026) Ionic Mechanisms of Murine Urethral Smooth Muscle Contractility. Doctoral thesis, Dundalk Institute of Technology.

PDF (Neha Gupta PhD Thesis) - Accepted Version Download (11MB)

Abstract

Urethral smooth muscle (USM) contraction is essential for continence, and dynamic spontaneous calcium (Ca2+) activity in interstitial cells of Cajal-like cells (ICC-LC) is thought to influence USM cells (USMC) by generating Ca2+ signals that help regulate USMC excitability and basal tone. We studied ICC-LC in the murine urethra using a transgenic Kit-GCaMP6f mouse model, which expresses the GCaMP Ca2+ sensor in kit+ cells through kit-promoter-driven iCre. This approach allowed us to visualise ICCLC in intact tissue, whereas earlier studies depended mainly on isolated cells and identified ICC-LC by morphology rather than definitive cellular markers. ICC-LC in USM were spindle-shaped, sparsely distributed, and exhibited asynchronous Ca2+ activity. ICC-LC lacked functional innervation, as they showed no response to endogenous excitatory or inhibitory neurotransmitter release evoked by neural stimulation. However, they responded to the exogenous α1-adrenergic receptor (α1- AR) agonist phenylephrine (PE), but not to a nitric oxide (NO) donor, indicating that they possess α1-AR. ICC-LC Ca2+ activity was primarily sustained by store-operated Ca2+ entry (SOCE). ANO1 (anoctamin-1, Ca2+ -activated-chloride channel) was expressed in USMC but not in ICC-LC; however, modulating ANO1 did not alter murine urethral contractility under the conditions tested. In addition, L-type Ca2+ channels (LTCC) or T-type Ca2+ channels (TTCC) inhibition had no effect, whereas Orai channel (Ca2+ -release activated Ca2+ channel) inhibition reduced agonist- or EFS-induced contractions in both male and female USM. In contrast, inhibition of Kv7 and BKCa channels enhanced nifedipine-sensitive phasic contractions during agonist and EFS stimulation in male USM, indicating their role in limiting LTCC activity, a mechanism largely absent in female USM, most likely due to lower functional LTCC. Overall, our findings show that Orai-mediated SOCE and SR Ca2+ release generate and maintain tonic contractions in murine USM, while BKCa and Kv7 limit LTCC dependent phasic contractions in male USM. These findings enhance understanding of the cellular and ionic mechanisms controlling USM contractility and provide a foundation for future studies aimed at developing strategies to treat UI.

Item Type:	Thesis (Doctoral)
Subjects:	Science > Biology Science
Research Centres:	UNSPECIFIED
Depositing User:	Bernard Drumm
Date Deposited:	02 Apr 2026 07:40
Last Modified:	02 Apr 2026 07:40
License:	Creative Commons: Attribution-Noncommercial-Share Alike 4.0
URI:	https://eprints.dkit.ie/id/eprint/1045

Actions (login required)

View Item

Downloads