Smooth muscle contractility causes the gut to grow anisotropically.

The intestine is the most anisotropically shaped organ, but, when grown in culture, embryonic intestinal stem cells form star- or sphere-shaped organoids. Here, we present evidence that spontaneous tonic and phasic contractions of the circular smooth muscle of the embryonic gut cause short-timescale elongation of the organ by a purely mechanical, self-squeezing effect. We present an innovative culture set-up to achieve embryonic gut growth in culture and demonstrate by three different methods (embryological, pharmacological and microsurgical) that gut elongational growth is compromised when smooth muscle contractions are inhibited.

Embryogenesis of the peristaltic reflex.

Key Points: Neurogenic gut movements start after longitudinal smooth muscle differentiation in three species (mouse, zebrafish, chicken), and at E16 in the chicken embryo. The first activity of the chicken enteric nervous system is dominated by inhibitory neurons. The embryonic enteric nervous system electromechanically couples circular and longitudinal spontaneous myogenic contractions, thereby producing a new, rostro-caudally directed bolus transport pattern: the migrating motor complex.