Recent research has highlighted the importance of mesoscale heterogeneity—variability among groups of cells at intermediate scales—in the formation of spiral patterns during the development of the social amoeba Dictyostelium discoideum. This study reveals how structural differences within cell populations influence the dynamics of intercellular communication and pattern formation.
Multicellular organisms are known to exhibit complex pattern formations reminiscent of waves, with examples ranging from neural activity to cardiac rhythms. Traditionally, studies have acknowledged microscale heterogeneity at the level of individual cells and macroscale differences impacting entire systems. Yet, the impacts of mesoscale heterogeneity—consisting of cellular clusters with distinct properties—had been largely overlooked until now.
The research team detailed their investigation of spiral wave formation via rigorous experimental methods, utilizing advanced imaging techniques to observe signals from these amoeba cells as they aggregated during nutrient starvation. Signals were communicated among cells through cyclic adenosine monophosphate (cAMP), acting as their primary sex pheromone. The analysis underscored the dynamics of cell excitability, where cells vary significantly in their ability to respond to these signaling cues.
Utilizing novel pulse-count analysis, the researchers successfully visualized areas of high and low excitability within cell clusters, emphasizing how patches of cells with varying levels of responsiveness influenced the spiraling waves. "We propose mesoscale heterogeneity, in addition to microscale and macroscale heterogeneities, is a key determinant of diverse multicellular pattern formations," stated the authors of the article.
The findings point to the presence of spatially heterogeneous wave propagation capabilities before spiral wave emergence, indicating how these structural differences acted as scaffolds for wave dynamics. Through experimental observations, the study documented the fascinating transition from collapsing to stably rotating spiral waves, attributed directly to the functional role of these heterogeneous clusters.
Notably, the emergence of rotating waves demonstrated similarities to mechanisms seen within cardiac tissues, where such dynamics give rise to more complex biological activities. The authors noted, "This study highlights the unexplored aspects of mesoscale heterogeneity beyond the well-studied micro- and macro-scales," reinforcing the notion of how cellular dynamics are influenced by internal variabilities.
Through their analysis, the researchers not only unveiled the previously underrecognized role of mesoscale heterogeneity but also provided valuable insights with significant implications for broader biological systems. Understanding these dynamics might inform future research on developmental processes and self-organizing systems across various multicellular organisms.
Overall, this work paves the way for new explorations of how different heterogeneity scales contribute to the emergent phenomena observed across biological systems, holding promise for advances ranging from developmental biology to medical applications associated with cell signaling and pattern formation.