This account is by Julie Clark, a Field Application Scientist at Stemgent in San Diego.
Some five dozen abstracts published for ISSCR this year included the word “oxygen”. Each highlighted the benefits of low oxygen (0.2-10% O2) for embryonic, hematopoietic, and mesenchymal stem cell culture. Indeed a steady stream of publications describes how hypoxia inducible factors and reactive oxygen species affect stem cell self-renewal and differentiation. This makes scientists wonder what might be missing in standard in vitro culture conditions.
A discussion with Jit Hin Tan from MIT highlighted the need for continuous hypoxia: Oxygen diffuses from the media surface to the attached cell layer, creating an oxygen gradient over a period of 24 hours. Exposure to atmospheric oxygen can undo this gradient within minutes. Kristiina Rajala from the Karolinska Institute found that low oxygen tension prevented spontaneous differentiation, increased proliferation and supported self-renewal of human embryonic stem cells (hESCs). Sandra Varum from the University of Texas described an alternate way to achieve some effects of low oxygen: antimycin A could mimic the enhanced pluripotency effect of hypoxia by inhibiting complex III of the mitochondrial respiratory chain, thereby reducing oxidative phosphorylation.
Diverse labs have thus identified benefits of hypoxia to cell culture. But, getting these benefits comes at a price. The cost of a hypoxic-incubator closed system starts at $70,000 (about 50,000 Euros). Given the success of culture under atmospheric conditions, researchers will have to think hard about whether to replicate in vitro the low-oxygen atmosphere that cells encounter in vivo.
Note from Niche editor This post comes as a result to my solicitation in June calling for people to submit their accounts of ISSCR 2009. I’d asked people to describe what most interested them, not to write about their own or their collaborators’ work, and to disclose any conflicts of interest. I’m very grateful for these volunteers’ help making more information available.