Bioelectric Signals and Calcium Waves Coordinate Skin Progenitor Cell Movement Patterns during the Polarization of Feather Buds

Abstract

A crucial challenge for tissue engineering is how to guide stem cells and their progeny to assemble into the unique organ shapes and structures. Currently known organizers for organogenesis include biochemical molecules, physical forces and bioelectric signals. One manifestation of bioelectric signaling in developing embryos is a relatively steady and long-lasting direct current (DC) and associated electric field. Using a vibrating probe, we detected the endogenous DC currents at different developmental stages of chicken feather buds. Interestingly, reversion of the direction of DC currents was observed at embryonic day 9 in anterior regions of feather buds. Perturbation of the endogenous DC currents by applying pulsed electric fields in the developing feather buds led to reorientation of the feather buds. Molecular studies revealed that T-type voltage-gated calcium channels (VGCCs) were expressed in anterior bud epithelial cells and mesenchymal cells, but rarely in posterior regions. Perfusion of high KCl solution induced cytoplasmic calcium elevations in epithelial and mesenchymal cells. The epithelial cells showed mosaic patterns of calcium fluctuations, while the mesenchymal cells had synchronized calcium fluctuations. Long-term calcium imaging demonstrated brief calcium transients in epithelial cells but systematic calcium waves in mesenchymal cells during feather polarization. Moreover, cell nucleus imaging revealed the movement of anterior bud epithelial cells toward posterior regions and the upward movement of mesenchymal cells during feather polarization. Functional perturbation of T-type VGCCs disrupted the patterns of cell movement and feather polarity, confirming the importance of bioelectric signals and calcium waves in feather polarity establishment.