In vitro intermittent hypoxia: challenges for creating hypoxia in cell culture

Intermittent hypoxia has been implicated in morbidities associated with sleep apnea, and may be a novel cellular signal for inflammation [J. Appl. Physiol. 90 (2001) 1986]. Standard cell culture has two major limitations for studying the effects of steady-state Po-2 and intermittent hypoxia. First, convective mixing in the culture media can be variable, making precise control of cellular Po-2 difficult. Second, diffusion of oxygen through the culture media slows changes in cellular Po-2 after rapid changes in the gas phase Po-2. Our estimates of diffusional transients for standard cell culture suggest significant restrictions in the ability to cycle Po, at frequencies relevant to intermittent hypoxia. We present a novel system for forced convection cell culture with adherent cells inside capillary tubing. Steady state cellular Po-2 is regulated to an accuracy of approximately 1 Torr. The response time for cycling of Po-2 is less than 1.6 sec. This system is ideally suited for studies of intermittent hypoxia in adherent cells. (C) 2003 Elsevier Science B.V. All rights reserved.