A Novel Gut Contractile Organoid Model for Studying Coordinated Signaling between Interstitial Cells of Cajal and Smooth Muscle Cells

Core Concepts

The gut contractile organoid developed in this study offers a useful model to understand the mechanisms underlying the rhythm coordination between/among interstitial cells of Cajal and smooth muscle cells during gut peristaltic movements.

Abstract

The researchers developed a novel "gut contractile organoid" derived from the muscle layer of chicken embryonic hindgut. The organoid undergoes periodic contractions and is composed primarily of interstitial cells of Cajal (ICCs) and smooth muscle cells (SMCs), with few enteric neurons.
Key highlights:

The organoid forms through self-organization, with ICCs residing internally and SMCs at the periphery, allowing distinction between the two cell types.
GCaMP-Ca2+ imaging revealed coordinated Ca2+ transients between ICC-ICC, SMC-SMC, and SMC-ICC, with Ca2+ rise in ICCs preceding that in SMCs.
Pharmacological studies suggested a role for gap junctions in ICC-to-SMC signaling, and possible feedback from SMC contraction to ICC pacemaking.
When two organoids with different rhythms were placed in a hydrogel, their rhythms became synchronized, mediated by SMCs, revealing a novel contribution of SMCs to ICC pacemaking.
Blebbistatin, an inhibitor of myosin II, abolished contractions and oscillatory Ca2+ patterns in both ICCs and SMCs, implying that contractility feeds back to regulate ICC rhythmic activity.
The gut contractile organoid provides a useful model to study the mechanisms underlying rhythm coordination between ICCs and SMCs during gut peristalsis.

Stats

The average frequencies of contractions in each cluster/spheroid at day 3, day 5, and day 7 were 3.32, 3.04, and 2.97 contractions/min, respectively.
The latency time between the rise of Ca2+ transient in ICCs and that in SMCs was 690 msec in average.

Quotes

"The gut contractile organoid developed in this study offers a useful model to understand the mechanisms underlying the rhythm coordination between/among interstitial cells of Cajal and smooth muscle cells during gut peristaltic movements."
"Blebbistatin ceased periodic contractions of organoids in a concentration-dependent manner, with 10 μM ceasing it completely."
"When two organoids with different oscillatory rhythm eventually coordinate their phases upon the fusion, this suggests the ability of ICCs to adjust their rhythm to their neighbors."

Key Insights Distilled From

The gut contractile organoid: a novel model for studying the gut motility regulated by coordinating signals between interstitial cells of Cajal and smooth muscles

by Yagasaki,R.,... at www.biorxiv.org 03-13-2024

https://www.biorxiv.org/content/10.1101/2024.03.12.584544v2

Deeper Inquiries

How might the addition of enteric nervous system components to the gut contractile organoid further elucidate the role of neural regulation in coordinating ICC and SMC interactions?

The addition of enteric nervous system (ENS) components to the gut contractile organoid could provide valuable insights into the neural regulation of ICC and SMC interactions. By incorporating ENS cells, such as neurons and glial cells, into the organoid model, researchers can study how neural signals influence the coordination between ICCs and SMCs during gut peristalsis. ENS components play a crucial role in regulating gut motility and coordinating the rhythmic contractions of smooth muscle cells.
Specifically, the presence of ENS cells in the organoid can help elucidate how neural signals modulate the pace-making activity of ICCs and the contractility of SMCs. Neurons in the ENS are known to release neurotransmitters that can affect the excitability of ICCs and SMCs, influencing their coordination and synchronization. By observing the interactions between ENS components and ICCs/SMCs in the organoid, researchers can gain a better understanding of the complex neural regulation of gut motility.

What other signaling pathways, beyond gap junctions, might be involved in the feedback mechanisms between SMC contractility and ICC pacemaking activity?

In addition to gap junctions, several other signaling pathways may be involved in the feedback mechanisms between SMC contractility and ICC pacemaking activity in the gut contractile organoid. These pathways play crucial roles in mediating the communication and coordination between ICCs and SMCs during peristalsis. Some of the key signaling pathways include:

Neurotransmitter Signaling: Neurotransmitters released by ENS neurons can directly influence the activity of ICCs and SMCs, modulating their contractions and pace-making activities. Neurotransmitter receptors on ICCs and SMCs allow for rapid communication and coordination between these cell types.

Calcium Signaling: Calcium ions play a central role in regulating smooth muscle contractions and ICC pace-making. Intracellular calcium dynamics in ICCs and SMCs are tightly controlled and coordinated, allowing for synchronized contractions. Calcium signaling pathways, including voltage-dependent calcium channels and calcium release mechanisms, are essential for the feedback loop between ICCs and SMCs.

Mechanical Signaling: Mechanical forces generated by SMC contractions can transmit signals to neighboring ICCs, influencing their pace-making activity. Mechanosensitive channels and receptors on ICCs may respond to mechanical stimuli from contracting SMCs, leading to adjustments in the rhythmic coordination between the two cell types.

Second Messenger Pathways: Signaling pathways involving second messengers, such as cyclic AMP (cAMP) and protein kinase pathways, can also contribute to the feedback mechanisms between SMC contractility and ICC pacemaking activity. Activation of these pathways can modulate the excitability and contractile properties of ICCs and SMCs, impacting their coordination during gut peristalsis.

Could insights from the gut contractile organoid model be applied to understand rhythm coordination in other smooth muscle-containing organs, such as the cardiovascular or urinary systems?

The insights gained from studying rhythm coordination in the gut contractile organoid model have the potential to be applied to understand similar mechanisms in other smooth muscle-containing organs, such as the cardiovascular or urinary systems. The principles of cellular interactions, coordination, and synchronization observed in the gut contractile organoid can be extrapolated to these systems to enhance our understanding of rhythmic activities in different physiological contexts.

Cardiovascular System: In the cardiovascular system, smooth muscle cells in blood vessels exhibit rhythmic contractions that regulate blood flow and pressure. By applying the knowledge of ICC-SMC interactions and neural regulation from the gut model, researchers can investigate how pacemaker cells and smooth muscle cells coordinate their activities in blood vessels. This can provide insights into vascular tone regulation and cardiovascular function.

Urinary System: Smooth muscle cells in the urinary system, such as the bladder and ureters, undergo rhythmic contractions to facilitate urine storage and voiding. Understanding the mechanisms of rhythm coordination between ICCs, SMCs, and neural components in the gut model can help unravel similar processes in the urinary system. Insights from the gut contractile organoid may shed light on bladder function and urinary tract motility disorders.

By leveraging the findings and methodologies developed in the gut contractile organoid model, researchers can explore the common principles of rhythmic coordination in smooth muscle-containing organs and advance our knowledge of physiological processes in various systems.