Light-dark and circadian melatonin rhythms are established de novo in re-aggregates of the embryonic chicken retina

In a century from agitated cells to human organoids

Reaching back more than a century, suspension cultures have provided major insights into processes of histogenesis; e.g., cell communication, distinction of self/nonself, cell sorting and cell adhesion. Besides studies on lower animals, the vertebrate retina served as excellent reaggregate model to analyze 3D reconstruction of a complex neural laminar tissue. Methodologically, keeping cells under suspension is essential to achieve tissue organisation in vitro; thereby, the environmental conditions direct the emergent histotypic particulars. Recent progress in regenerative medicine is based to a large extent on human induced pluripotent stem cells (hiPSCs), which are cultured under suspension. Following their genetically directed differentiation into various histologic 3D structures, organoids provide excellent multipurpose in vitro assay models, as well as tissues for repair transplantations. Historically, a nearly fully laminated retinal spheroid from avian embryos was achieved already in 1984, foreshadowing the potential of culturing stem cells under suspension for tissue reconstruction purposes.

Activation of phospholipase C mimics the phase shifting effects of light on melatonin rhythms in retinal photoreceptors

Many aspects of retinal photoreceptor function and physiology are regulated by the circadian clocks in these cells. It is well established that light is the primary stimulus that entrains these clocks; yet, the biochemical cascade(s) mediating light’s effects on these clocks remains unknown. This deficiency represents a significant gap in our fundamental understanding of photoreceptor signaling cascades and their functions. In this study, we utilized re-aggregated spheroid cultures prepared from embryonic chick retina to determine if activation of phospholipase C in photoreceptors in the absence of light can phase shift the melatonin secretion rhythms of these cells in a manner similar to that induced by light. We show that spheroid cultures rhythmically secrete melatonin and that these melatonin rhythms can be dynamically phase shifted by exposing the cultures to an appropriately timed light pulse. Importantly, we show that activation of phospholipase C using m-3M3FBS in the absence of light induces a phase delay in photoreceptor melatonin rhythms that mirrors that induced by light. The implication of this finding is that the light signaling cascade that entrains photoreceptor melatonin rhythms involves activation of phospholipase C.

An automatic monitoring of the hatching process based on the noise of the hatching chicks

In this manuscript, a new tool is presented for automatic monitoring of the hatching process of eggs without opening the incubator doors. The amount of energy in the noise produced by the hatchlings was registered by means of a microphone and a personal computer for signal treatment. Evidence is shown that it is possible to detect exactly when the first chicks are hatched, the mean hatching time, and the finish of hatch. The information generated by this tool can be used by the hatchery manager to make the decision to end the incubation at the right moment, resulting in a higher number of first quality chicks without the risk of a reduced hatchability due to too early termination of the incubation process. The presented research also shows evidence that there is already a circadian rhythm in the newborn hatchling even when no external stimulus is present.