Gas Partial Pressure in Cultured Cells: Patho-Physiological Importance and Methodological Approaches

Abstract

Gas partial pressures within the cell microenvironment are one of the key modulators of cell pathophysiology. Indeed, respiratory gases (O2 and CO2) are usually altered in respiratory diseases and gasotransmitters (CO, NO, H2S) have been proposed as potential therapeutic agents. Investigating the pathophysiology of respiratory diseases in vitro mandates that cultured cells are subjected to gas partial pressures similar to those experienced by each cell type in its native microenvironment. For instance, O2 partial pressures range from ∼13% in the arterial endothelium to values as low as 2–5% in cells of other healthy tissues and to less than 1% in solid tumor cells, clearly much lower values than those used in conventional cell culture research settings (∼19%). Moreover, actual cell O2 partial pressure in vivo changes with time, at considerably different timescales as illustrated by tumors, sleep apnea, or mechanical ventilation. Unfortunately, the conventional approach to modify gas concentrations at the above culture medium precludes the tight and exact control of intra-cellular gas levels to realistically mimic the natural cell microenvironment. Interestingly, well-controlled cellular application of gas partial pressures is currently possible through commercially available silicone-like material (PDMS) membranes, which are biocompatible and have a high permeability to gases. Cells are seeded on one side of the membrane and tailored gas concentrations are circulated on the other side of the membrane. Using thin membranes (50–100 μm) the value of gas concentration is instantaneously (<0.5 s) transmitted to the cell microenvironment. As PDMS is transparent, cells can be concurrently observed by conventional or advanced microscopy. This procedure can be implemented in specific-purpose microfluidic devices and in settings that do not require expensive or complex technologies, thus making the procedure readily implementable in any cell biology laboratory. This review describes the gas composition requirements for a cell culture in respiratory research, the limitations of current experimental settings, and also suggests new approaches to better control gas partial pressures in a cell culture.

Extended hypoxia‐mediated H2S production provides for long‐term oxygen sensing

“…The physioxic Po 2 for cells used in this study is quite variable (Po 2 in parenthesis); HEK293 (50-70), BPASMC (42-100), stem (100 in peritoneum, 15 or lower for most cells), A549 (100-200), PTE (140), HTC116 (85 in crypt to <10 at villus tip). [51][52][53][54][55][56][57][58] In the present experiments, we clearly show that H 2 S production in a variety of cells varies inversely with Po 2 over a range of O 2 tensions from hyperoxic to physioxic to hypoxic. We also show that H 2 S production in HCT116 cells is less sensitive to Po 2 , which presumably reflects their relatively hypoxic environment in vivo.…”

“…Even normoxia (or more appropriately physioxia) will vary depending on the environment inhabited by cells in situ. The physioxic P o 2 for cells used in this study is quite variable (Po 2 in parenthesis); HEK293 (50‐70), BPASMC (42‐100), stem (100 in peritoneum, 15 or lower for most cells), A549 (100‐200), PTE (140), HTC116 (85 in crypt to <10 at villus tip) . In the present experiments, we clearly show that H 2 S production in a variety of cells varies inversely with Po 2 over a range of O 2 tensions from hyperoxic to physioxic to hypoxic.…”

Bioengineering a novel 3D in-vitro model to recreate physiological oxygen levels and tumor-immune interactions

“…Physiological oxygen levels in solid tumors are very heterogeneous ranging from 0.5 -4% oxygen saturation compared to 4 -14% in healthy tissues (59,(61)(62)(63). In addition, circulating and immune cells are exposed to a full dynamic range of blood physiological O2, in which the pO2 varies from 13.5% in alveoli and 9.5% in arterial blood to 6.5% at the venous end of circulation (64)(65)(66)(67)(68). Therefore, studies employing models incubated at atmospheric oxygen (21% O2) culture conditions are hyperoxic with respect to the tissue of origin (65,69).…”

Investigating Disturbances of Oxygen Homeostasis: From Cellular Mechanisms to the Clinical Practice

“…Several systems using cell culture dishes with gas-permeable membranes have been introduced. These membrane-based systems offer the advantage of direct delivery of gases to the cultured cell layer without the need for slow equilibration of the culture medium ( Wu et al, 2016b ; Farre et al, 2018 ). Depending on the material of the gas-permeable membrane, very fast transition times can be achieved (below 0.5 s for polydimethylsiloxane (PDMS) membranes on silicone basis).…”