The Oxygen Gradient in Hypoxic Conditions Enhances and Guides Dictyostelium discoideum Migration

Abstract

Spatiotemporal variations of oxygen concentration affect the cell behaviors that are involved in physiological and pathological events. In our previous study with Dictyostelium discoideum (Dd) as a model of cell motility, aggregations of Dd cells exhibited long-lasting and highly stable migration in a self-generated hypoxic environment, forming a ring shape that spread toward the outer higher oxygen region. However, it is still unclear what kinds of changes in the migratory properties are responsible for the observed phenomena. Here, we investigated the migration of Dd to clarify the oxygen-dependent characteristics of aerokinesis and aerotaxis. Migratory behaviors of Dd cells were analyzed under various oxygen concentration gradients and uniform oxygen conditions generated in microfluidic devices. Under hypoxic conditions below 2% O2, corresponding to less than 25 µM O2 in the culture medium, the migration of Dd cells was enhanced (aerokinesis) and the oxygen gradient guided the cells toward the oxygen-rich region (aerotaxis). The aerotaxis was attributed to the increase in the frequency of migration associated with the direction of higher O2, the acceleration of migration velocity, and the enhancement of migration straightness. Thus, aerokinesis and aerotaxis are dependent on both the oxygen level and possibly relative gradient and are essential mechanisms for the migration of Dd.

Hypoxia suppresses glucose-induced increases in collective cell migration in vascular endothelial cell monolayers

“…The microfluidic device used for oxygen concentration control was fabricated with PDMS, a polycarbonate (PC) film, and a glass coverslip (Fig. 1 ) 36 . The device was square, with sides of 30 mm, and two gas channels (width 2 mmμ, height 150 μm) were placed at a height of 500 μm, perpendicular to three parallel media channels (width 2 mm, height 150 μm) on the bottom.…”

“…The oxygen concentration in the three media channels was controlled to the same condition by supplying gas mixtures with 21%, 1%, or 0% O 2 , maintaining 5% CO 2 balanced with nitrogen, to both gas channels using a gas blender (3MFC GAS MIXER, KOFLOC, Japan). Using these gas mixtures, an actual oxygen concentration of 21%, 1.3%, or 0.3% O 2 was generated in the media channels, respectively (normoxic condition N, hypoxic conditions H1, or H0) 36 , focusing on cell migration under very low oxygen concentrations. By supplying a gas mixture containing 21% O 2 and 5% CO 2 to the gas channels for 1 h, a steady normoxic state was first generated, and the temperature and pH in the device were stabilized.…”

The aerotaxis of Dictyostelium discoideum is independent of mitochondria, nitric oxide and oxidative stress

“…A double-layer microfluidic device with oxygen-controllability was used ( Supplementary Figure S1 ) ( Hirose et al, 2022 ). The device was 30 × 30 mm square, and the thickness was 4 mm.…”

“…In a confined spot assay, Dictyostelium cells exhibited long-lasting and highly stable migration towards oxygen-rich regions (i.e., aerotaxis) guided by a self-generated oxygen gradient, forming a stable ring of cells to escape from the hypoxic region ( Biondo et al, 2021 ; Cochet-Escartin et al, 2021 ). Moreover, the aerotaxis of Dictyostelium was successfully confirmed under controlled oxygen gradient generated by microfluidic devices with gas channels for supply of gas mixture of nitrogen and oxygen ( Hirose et al, 2022 ). Under hypoxic conditions, below 2% O 2 , which corresponds to 25 µM O 2 in the culture medium, the migration of Dictyostelium cells was enhanced (aerokinesis), and the oxygen gradient guided the cells toward the oxygen-rich region (aerotaxis).…”

Microphase separation of living cells

“…Each cell is endowed with aerotactic behavior, which sets in below a characteristic concentration c aer . We assume logarithmic sensing 51 and a drift velocity v aer ∼ ∇ðln cÞ. To a move from site m to a neighboring site m 0 , we associate an energy…”