Coupling of Chemical Sensing, Mechanosensing, and Wound Healing in Mammalian Cells through Collective Calcium Dynamics

Abstract

Collective behavior of mammalian cells dictates various crucial physiological processes throughout the lifetime of an organism. The cellular decision making process to achieve such processes stems from an understanding of how cell cultures collectively sense their environments. We use experimental techniques to study the collective behavior in mammalian cells using NIH-3T3 fibroblast cells as our model system, particularly how chemical and mechanical sensing processes integrate into the process of wound healing. We utilize the quantifications and analysis of collective calcium dynamics to highlight the significance of regulated agonist-induced and wound-induced calcium dynamics in cell cultures, and present a plausible mechanism of wound healing on diverse mechanical environments that may be important in complex biological processes.

Chemical sensing is a stochastic process in individual cells, yet highly regulated in multicellular organisms. We characterize the collective chemosensing process by studying the spatial-temporal calcium dynamics of fibroblast cells in response to external ATP stimulation in Chapter 2. Our observations highlight the crucial role of the two key elements of collective chemosensing, intercellular communications and pacemaker cells, in generating regulated spatial and temporal dynamics in cell cultures. The work presented in Chapter 3 discusses the effect of substrate mechanics on the ATP-induced collective calcium response in fibroblast cell cultures where emergent behavior exists. Such coupling of the chemical and mechanical sensing processes results in calcium responses that are more persistent and re-excitable on soft substrates. We conclude that actin dynamics and gap junctions determine the ATP-induced, substrate-dependent collective calcium dynamics in the culture by maintaining collective cell responsiveness and oscillatory behavior.

Lastly, one of the complex physiological activities involving both chemical and mechanical sensing is wound healing. Chapter 4 discusses the effect of substrate mechanics on the wound-induced collective calcium oscillations of fibroblast cells in various tissue environments. Our observations from the spatial distribution of calcium oscillations and traction forces in a wound suggest the different mechanisms of wound healing for various substrates. Overall, we are able to conclude that maintaining collective calcium response behavior requires cell-substrate interaction through the arrangement of cytoskeletons, which consequently affects the spatial regulation of wound healing.