Abstract
The two-dimensional (2D) monoculture does not recapitulate the three-dimensional (3D) environment of in vivo vasculature. Endothelial cell (ECs) spheroids have been introduced as a 3D in vitro model exhibiting angiogenic responses and sprouting behavior in vivo. However, mural cells (MCs), including the phenotypic range from pericytes to smooth muscle cells (SMCs), play an essential organotypic role in vascular homeostasis (vascular remodeling/stabilization) and disease. Therefore, the development of 3D cell structures (small-scale vascular organoids) containing both ECs and MCs subtypes provide enhanced cell–cell interactions that closely mimic the natural/physiological vascular microenvironment with beneficial effects on cell survival, phenotypic stability, and function. Due to limitations of isolation/expansion of primary MCs as well as their phenotypic plasticity during in vitro culture, human pluripotent stem cells (hPSCs) (human induced pluripotent stem cells-hiPSCs and human embryonic stem cells-hESCs) are a source for the generation of defined MC populations.
We generated a flexible, small-scale 3D organoid-like platform consisting of hPSC-SMCs/ECs, which undergo self-assembly into a segregated 3D structure characterized by a multicellular spheroidal SMC core and an outer EC layer. The structure can be regarded as an inside-out assembly of a resting vessel wall. When these vascular organoids are implanted in 3D extracellular matrices, they are superior to sole ECs regarding the development of a mature vascular network.