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New Differentiation Strategy Aims to Boost Cell Therapies for Vascular Disease

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Review of “Highly Efficient Differentiation of Endothelial Cells from Pluripotent Stem Cells Requires the MAPK and the PI3K Pathways” from STEM CELLS by Stuart P. Atkinson

The specific and efficient differentiation of endothelial cells (ECs) from human pluripotent stem cell (hPSCs) may allow the construction of enhanced cell therapies for vascular disease [1, 2]. However, for this to become a clinical reality, we require a simple, efficient, and cost-effective means to generate functional ECs based on our current understanding of the mechanisms that govern endothelial fate.

A report from the laboratory of Ping Zhou (University of California Davis, California, USA) has recently described a highly efficient and cost-effective new differentiation strategy that yields a nearly pure population of ECs from hPSCs without the need for intensive cell sorting. Furthermore, the group now identify a signaling duo (the MAPK and PI3K pathways) with vital roles in the determination of endothelial lineages and, therefore, the potential success of cell therapies for vascular disease [3].

Using human induced pluripotent stem cells (hiPSCs), the study aimed to establish the factors required for the efficient and effective differentiation of ECs. The study discovered that:

  • Elevated WNT signaling (using a GSK3 inhibitor for 2 days) efficiently induced mesodermal differentiation of hiPSCs and subsequent potentiation of VEGF, BMP, and FGF signaling pathways (two days) induced the production of vascular progenitor cells expressing EC markers (PECAM1 and VE-cadherin)
    • This step required the action of MAPK signaling and PI3K pathways via the regulation of the EST family transcription factors (ERG, FLI1)
    • The easy removal of “central” cells by Accutase treatment to leave “peripheral” vascular progenitor cells permitted the maintenance of a pure cell population
  • Application of endothelial differentiation medium (ECGM-MV2) supplemented with VEGF (4-6 days) to the vascular progenitors allowed the production of a nearly pure endothelial cell population (iPSC-ECs) without the need for cell sorting or magnet bead separation
    • This step also required the action of the MAPK and PI3K pathways
    • iPSC-ECs produced expressed elevated levels of additional endothelial markers (vWF, Tie2, NOS3) 
    • iPSC-ECs exhibited cell-specific functions such as uptake of low-density lipoprotein, the formation of tubes in vitro or vessels in vivo on Matrigel
  • Importantly, the iPSC-ECs derived via this new differentiation strategy grafted and formed patent blood vessels connecting to the host vasculature when injected into a mouse ischemic limb mode (See Figure - FITC-Dextran (Green) marks mouse blood, while hCD31 (red) marks human CD31+ ECs)

These data suggests that iPSC-ECs may prove useful for the treatment of vascular disease and the quick, cheap, and effective new differentiation strategy described may provide a means to produce highly pure populations of ECs from hiPSCs and bring patient-specific treatments for CVDs to the masses. Furthermore, the ease of EC production may also permit the detailed study of EC differentiation to deeply understand the molecular mechanisms as play, while the success of iPSCs may also allow us to model patient-specific EC-related diseases/disorders and screen drugs as treatment options.

Discussion Points

  • What other signaling pathways are vital for EC generation from iPSCs?
  • Can we apply disease-specific iPSCs to model disease progression and screen drugs?
  • How can we potentiate the regenerative effect of iPSC-ECs in vivo?

References

  1. Wilson HK, Canfield SG, Shusta EV, et al. Concise review: tissue-specific microvascular endothelial cells derived from human pluripotent stem cells. Stem Cells 2014;32:3037-3045.
  2. Yoder MC. Differentiation of pluripotent stem cells into endothelial cells. Curr Opin Hematol 2015;22:252-257.
  3. Harding A, Cortez-Toledo E, Magner NL, et al. Highly Efficient Differentiation of Endothelial Cells from Pluripotent Stem Cells Requires the MAPK and the PI3K Pathways. STEM CELLS 2017;35:909-919.