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Microchamber, Mega mESC Pluripotency!

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Review of  “Embryonic Stem Cells Cultured in Microfluidic Chambers Take Control of Their Fate by Producing Endogenous Signals Including LIF” from Stem Cells by Stuart P. Atkinson

Culturing embryonic stem cells (ESCs) requires a high level of care, a significant amount of time, and the near constant supply of exogenous signals from added factors and/or the presence of fibroblast feeder layers [1-3]. However, do ESCs really need all this outside help? ESCs can produce their own endogenous pro-pluripotency factors [3, 4] and so should be able to “care” for themselves. 

To investigate this possibility, researchers from the laboratory of Alexander Revzin (University of California, Davis, USA) studied mouse (m)ESCs cultured in a microfluidic culture device in the absence of feeders or exogenously added factors. In their new Stem Cells study, they show how culture at the microscale allows mESCs to harness endogenous signaling and maintain the pluripotent state [5]. Could this lead to the cheaper and more efficient micro-culture of ESCs?

The microchambers employed measured 5 mm × 3 mm × 75 μm, allowing for a functional volume of around 1 μl. To enhance the retention and accumulation of secreted factors, the authors also used minimal media perfusion. Importantly, the authors first confirmed the absence of significant changes to the glucose and oxygen levels in the microchambers, so making correlations between changes to the ESC pluripotent state and enhanced autocrine signaling more evident.

And changes they found! mESCs grown in microchambers had a dome-shaped morphology reminiscent of naïve state mESCs and had enhanced pluripotency-associated gene expression and reduced post-implantation markers. Interestingly, the study also found that an increase in microchamber volume mediated a decrease in pluripotency, possibly due to a dilution in cell-secreted factors such as LIF and BMP4. These pluripotency-associated factors tended to accumulate at high levels in the microchambers and mediated heightened endogenous signaling through the LIF-JAK-STAT3 and SMAD1/5 pathways respectively.

So, micro-scale culture boosts pluripotency, but does this affect ESC differentiation potential? Although, as we mentioned, BMP4 is linked to pluripotency, it can also mediate mesodermal differentiation if other signaling pathways are altered. This study found that LIF-JAK-STAT3 signaling inhibition mediated the efficient differentiation of mESCs into mesodermal-like cells, so suggesting that endogenous signaling can also be harnessed to promote ESC differentiation.

Improved multiplexing, lower reagent costs, and improved control are just some of the advantages that microchamber-mediated cultures offer over standard widely-used milliliter-scale culture. Will hESCs behave in a similar manner? Keep yourself tuned to the Stem Cells Portal to find out!

Discussion Points

  • Can microchambers become a standard part of ESC culture labs?
  • Will the same approach work with human embryonic stem cells?
  • Are other stem cell populations amenable for growth in microscale conditions?

References

  1. Martin GR Isolation of a pluripotent cell line from early mouse embryos cultured in medium conditioned by teratocarcinoma stem cells. Proc Natl Acad Sci U S A 1981;78:7634-7638.
  2. Thomson JA, Itskovitz-Eldor J, Shapiro SS, et al. Embryonic stem cell lines derived from human blastocysts. Science 1998;282:1145-1147.
  3. Ying QL, Nichols J, Chambers I, et al. BMP induction of Id proteins suppresses differentiation and sustains embryonic stem cell self-renewal in collaboration with STAT3. Cell 2003;115:281-292.
  4. Davey RE, Onishi K, Mahdavi A, et al. LIF-mediated control of embryonic stem cell self-renewal emerges due to an autoregulatory loop. FASEB J 2007;21:2020-2032.
  5. Guild J, Haque A, Gheibi P, et al. Embryonic Stem Cells Cultured in Microfluidic Chambers Take Control of Their Fate by Producing Endogenous Signals Including LIF. STEM CELLS 2016;34:1501-1512.