PC1106: Loss of Smooth Muscle Cell piezo1 Leads to Impaired Contractility in the Small Bowel

Saturday, October 8, 2022

5:15 PM – 6:00 PM US PDT

Location: Anaheim Convention Center, Hall A, Board # 106

Background: Piezo1 is a mechanosensitive cation channel expressed in the gut's smooth muscle cells (SMCs). Yet, its role in the small bowel external muscularis and its contractility has not been determined. Here we aim to elucidate the role of SMC Piezo1 in small bowel contractility at baseline and with stretch.

Methods: In vivo, ex vivo, and in vitro methods were used to determine whether Piezo1 in SMCs is necessary for mediating intestinal motility. A Piezo1/Myh11-ERT2/Cre-LoxP system was used to generate a tamoxifen-inducible Piezo1 knockout (Piezo1ΔSMC) and control (Piezo1WT) mice. Intestinal muscle cells (IMCs) were obtained from murine pups and seeded on thermosensitive hydrogels to simulate stretch in vitro. Isotonic force and contractility measurements were obtained on ex vivo segments of distal small bowel from adult mice at baseline and with stretch. Samples were also exposed to nicardipine, an L-type channel inhibitor, and GsMTx4, a Piezo channel inhibitor, to characterize the interplay between Piezo1 and L-type channels.

Results: Adult Piezo1ΔSMC mice had diminished caloric consumption, impaired growth, and prolonged gut transit times compared to Piezo1WT mice (p < 0.001). In vivo histological assessment showed a thinning of the muscularis layer (p < 0.01) and a decline in interstitial cells of Cajal (ICC) in Piezo1ΔSMC mice (p < 0.01). Ex vivo, myograph experiments showed that Piezo1ΔSMC led to decreased amplitude, frequency and rhythmicity of contractility compared to Piezo1WT. Addition of nicardipine to Piezo1ΔSMC led to a further reduction in contractility. In Piezo1WT, the remaining contractility seen with nicardipine is further reduced with GsMTx4. In vitro, Piezo1ΔSMC IMCs had decreased frequency and a dysrhythmic and asynchronous pattern of Ca2+flux/contractility compared to Piezo1WT IMCs, which was further reduced with stretch (p < 0.01). Piezo1shRNA in murine IMCs showed significantly diminished Ca2+flux/contractility compared to control IMCs treated with scramble lentivirus (p < 0.01).

Conclusion: Our data suggest that Piezo1 in the SMCs of the intestinal muscularis is critical for maintaining baseline and stretch-induced contractility, normal width of the external muscularis and ICC abundance in the small bowel. Furthermore, our data shows that both Piezo1 channels and L-type channels are essential components in small bowel motility, with a drastic reduction in contractility and response to stretch when both channels are inhibited.

Presenting Author(s)

Geoanna Bautista, MD

Assistant Professor of Pediatrics-Neonatology
University of California, Davis
University of California, Davis
Sacramento, California

Co-Author(s)

YD

Yingjie Du, n/a

PhD student
University of California, Los Angeles
Los Angeles, California
NM

Nicolle Martin, n/a

PhD student
University of California, Davis
Davis, California
MM

Michael Matthews, n/a

Research Associate
University of California, Los Angeles
Los Angeles, California
ET

Elmira Tokhtaeva, PhD

Staff Research Associate
University of California, Los Angeles
Los Angeles, California
RS

RS Solorzano-Vargas, n/a

Staff Research Associate
University of California, Los Angeles
Los Angeles, California

Senior Author(s)

James Dunn, MD, PhD

Professor of Surgery, Pediatrics
Stanford University
Stanford University
Palo Alto, California
MM

Martin Martin, Martin, MD

Professor of Pediatrics, Gastroenterology
University of California, Los Angeles
Los Angeles, California