PDGFRα+ subepithelial interstitial cells act as a pacemaker to drive smooth muscle of the guinea pig seminal vesicle

• Published in: The Journal of physiology Vol. 600; no. 7; pp. 1703 - 1730
• Main Authors: Takeya, Mitsue, Higashi, Ryuhei, Hashitani, Hikaru, Nakamura, Kei‐ichiro, Hayashi, Tokumasa, Nakashima, Noriyuki, Takano, Makoto
• Format: Journal Article
• Language: English
• Published: England Wiley Subscription Services, Inc 01-04-2022
• Subjects: Calcium (intracellular); Calcium imaging; Calcium signalling; Cyclopiazonic acid; electrical slow wave; Epithelial cells; Growth factors; Immunohistochemistry; interstitial cell; Interstitial cells; Mucosa; Nifedipine; Oscillations; Pacemakers; PDGFRα; Physical characteristics; Platelets; Scanning electron microscopy; Seminal vesicle; Smooth muscle; spontaneous Ca2+ transient; PDGFRα; seminal vesicle; interstitial cell; spontaneous Ca2+ transient; mucosa; electrical slow wave
• ISSN: 0022-3751; 1469-7793
• DOI: 10.1113/JP281686

Smooth muscle cells (SMCs) of the guinea pig seminal vesicle (SV) develop spontaneous phasic contractions, Ca2+ flashes and electrical slow waves in a mucosa‐dependent manner, and thus it was envisaged that pacemaker cells reside in the mucosa. Here, we aimed to identify the pacemaker cells in SV mucosa using intracellular microelectrode and fluorescence Ca2+ imaging techniques. Morphological characteristics of the mucosal pacemaker cells were also investigated using focused ion beam/scanning electron microscopy tomography and fluorescence immunohistochemistry. Two populations of mucosal cells developed spontaneous Ca2+ transients and electrical activity, namely basal epithelial cells (BECs) and subepithelial interstitial cells (SICs). Pancytokeratin‐immunoreactive BECs were located on the apical side of the basement membrane (BM) and generated asynchronous, irregular spontaneous Ca2+ transients and spontaneous transient depolarisations (STDs). The spontaneous Ca2+ transients and STDs were not diminished by 10 μM nifedipine but abolished by 10 μM cyclopiazonic acid (CPA). Platelet‐derived growth factor receptor α (PDGFRα)‐immunoreactive SICs were distributed just beneath the basal side of the BM and developed synchronous Ca2+ oscillations and electrical slow waves, which were suppressed by 3 μM nifedipine and abolished by 10 μM CPA. In SV mucosal preparations in which some smooth muscle bundles remained attached, SICs and residual SMCs developed temporally correlated spontaneous Ca2+ transients. Neurobiotin injected into SICs spread not only to neighbouring SICs but also to neighbouring SMCs or vice versa. These results suggest that PDGFRα+ SICs electrotonically drive the spontaneous contractions of SV smooth muscle.
Key points
In many visceral smooth muscle organs, spontaneous contractions are electrically driven by non‐muscular pacemaker cells. In guinea pig seminal vesicles (SVs), as yet unidentified mucosal cells appear to drive neighbouring smooth muscle cells (SMCs).
Two populations of spontaneously active cells are distributed in the SV mucosa. Basal epithelial cells (BECs) generate asynchronous, irregular spontaneous Ca2+ transients and spontaneous transient depolarisations (STDs). In contrast, subepithelial interstitial cells (SICs) develop synchronous Ca2+ oscillations and electrical slow waves.
Pancytokeratin‐immunoreactive (IR) BECs are located on the apical side of the basement membrane (BM), while platelet‐derived growth factor receptor α (PDGFRα)‐IR SICs are located on the basal side of the BM.
Spontaneous Ca2+ transients in SICs are synchronised with those in SV SMCs. Dye‐coupling between SICs and SMCs suggests that SICs act as pacemaker cells to drive the spontaneous contractions of SV smooth muscle.
figure legend The seminal vesicles (SVs) of guinea pig generate spontaneous phasic contractions (SPCs). SV smooth muscle cells (SMCs, pink) develop SPCs associated with spontaneous electrical slow waves and Ca2+ flashes, which require the attachment of the mucosal layer. Histological examination demonstrated a layer of PDGFRα‐immunoreactive subepithelial interstitial cells (SICs, green) underneath the basement membrane. The SICs spontaneously develop synchronous Ca2+ oscillations and electrical slow waves, at a frequency corresponding to those of SPCs. The dye‐coupling between SICs and SMCs further suggested that the synchronous electrical slow waves in the SICs electrotonically conduct to the SV SMCs via gap junctions (orange). Thus, the SICs appear to act as electrical pacemaker cells driving SPCs of SVs. The basal epithelial cells (BECs, brown) also generated asynchronous, irregular spontaneous Ca2+ transients and spontaneous transient depolarisations, although their role in developing SPCs remains to be explored.