How do injured cells communicate with the surviving cell monolayer?

Abstract

Mechanically scratching cell monolayers relieves contact inhibition and induces surviving cells near the wound edge to move and proliferate. The present work was designed to test whether surviving cells passively respond to newly available space, or whether cells are actively stimulated by signals from injured cells nearby. We monitored intracellular free Ca2+ ([Ca2+]i) while scratching confluent monolayers of bovine pulmonary endothelial cells and mouse mammary epithelial cells. Within seconds after wounding, a transient elevation of [Ca2+]i was observed in surviving cells. In endothelial cells, the [Ca2+]i elevation propagated into the monolayer for a distance of 10 to 12 cell rows at a speed of 20 to 28 microm/second. The amplitude of the wave of [Ca2+]i was reduced as it propagated into the monolayer, but the velocity of the wave was nearly constant. Cells that experienced the [Ca2+]i elevation had intact plasma membranes, and survived for over 24 hours post wounding. Removing extracellular Ca2+ decreased the amplitude by two-thirds and reduced the propagation rate by half, suggesting that Ca2+ influx contributed to the increased [Ca2+]i. To determine how [Ca2+]i waves were stimulated, we blocked extracellular communication by fluid perfusion or intercellular communication by breaks in the monolayer. In bovine pulmonary artery endothelial cultures, the [Ca2+]i wave passed over breaks in the monolayer, and was prevented from traveling upstream in a perfusion chamber. Conditioned media from injured cells also elevated [Ca2+]i in unwounded reporter cultures. In mouse mammary epithelial monolayers with established cell-cell contacts, the [Ca2+]i wave passed over breaks in the monolayer, but was only partially prevented from traveling upstream during perfusion. These experiments showed that mechanical wounds lead to long distance, [Ca2+]i-dependent communication between the injured cells and the surviving cell monolayer through at least two mechanisms: first, extracellular release of a chemical stimulus from wounded cells that diffused to neighboring cells (present in both monolayers); second, transmission of an intercellular signal through cell-cell junctions (present in the mammary epithelial monolayers). Thus, mechanical injury provided a direct, chemical stimulus to nearby cells which have not themselves been damaged.

A vascular injury model using focal heat-induced activation of endothelial cells

“…11 Flow assays that include monolayers of cultured EC typically involve stimulation by chemical, mechanical and laser methods. [12][13][14] For example, exposure to inflammatory agents such as TNF-a and interleukin-1 leads to P-selectin exposure on EC, among other prothrombotic molecules, and the recruitment of platelets. 11,15 Stimulation of endothelialized microfluidic channels with TNF-a and shiga toxin mimics the pathology of microvascular diseases such acute inflammation and hemolytic uremic syndrome.…”

Emergence of target waves in paced populations of cyclically competing species

“…Spatially extended excitable systems are investigated frequently due to their omnipresence in several biological, chemical and physical settings [1,2,3,4,5,6], as reviewed comprehensively in [7,8]. Especially pattern formation and the related self-organized emergence of target waves have received ample attention in the past [9].…”

The first digestive movements in the embryo are mediated by mechanosensitive smooth muscle calcium waves

“…4b). It is known that calcium waves are emitted after wounding of epithelia (22) or whole organisms (23). The calcium up-rise is probably due to influx from the extracellular medium due to disruption of membrane integrity after wounding (24,25), and has been shown to orchestrate wound healing (23,26).…”