b2815 Tissue Engineering and Nanotheranostics “9.61x6.69”
94 Tissue Engineering and Nanotheranostics
maintaining homeostasis. These cells are known to malfunction in a
variety of conditions including atherosclerosis, stroke, and Alzheimer’s.
As these cells are important components of blood vessel and heart
tissue, stem cell derived endothelial cells hold interest for engineering
new blood vessels and cell based myocardial repair.
In 2004, Wang et al. used hESCs to form embryoid bodies and
identified endothelial-like progenitor cells, or hemangioblasts, that
were multipotent for endothelial and hematopoietic lineages.^68 These
cells were marked by expressions of PECAM-1, Flk-1, and VE-cadherin
and lacked CD45 expression.^68 In 2007, Lu et al. published a two-
step protocol to culture human embryoid bodies and achieve heman-
gioblasts.^69 Their serum free technique used cytokine additions of
BMP4, VEGF, SCF, TPO, and Flt-3 ligand; however their efficiency
was very low with less than 1% of the cells actually differentiating to
a hemangioblast state.^69 In 2007, Wang et al. showed a 2D coculture
system with hESCs, MEF cells, and fetal bovine serum supplement
that was able to produce hematopoietic progenitors and endothelial
progenitors marked by the expression of PECAM-1.^70 While this
technique did not rely on spontaneous differentiation of embryoid
bodies, which has very low efficiency, it relied on murine coculture
minimizing therapeutic application and lacking definition.
Interestingly, they demonstrated that when these cells were trans-
planted into SCID mice, they contributed to blood vessel develop-
ment and integrated into the circulatory system.^70
In 2010, James et al. initially stimulated human embryoid bodies
with BMP4, Activin A, FGF-2, and VEGF and then dissociated the
embryoid bodies for further culture.^71 While these conditions pro-
duced endothelial progenitors as marked by VE-cadherin expression,
the method lacked efficiency, and the endothelial cells were not read-
ily expanded.^71 They found by adding a small molecule inhibitor of
TGF-β, SB431542, they were able to increase their yield of
VE-cadherin positive cells; however SB431542 addition was only
effective when added after the cells differentiated to the point of vas-
cular commitment.^71 In 2013, Kusuma et al. developed a 2D culture
technique which used serum supplemented media in the initial stage
and then treated the cells with VEGF and SB431542.^72 They were
