# Tissue microenvironment dictates the state of human iPSC-derived endothelial cells of distinct developmental origin in 3D cardiac microtissues

## TL;DR

This study shows that the heart's microenvironment can reshape the identity of human stem cell-derived blood vessel cells, regardless of their origin.

## Contribution

The study reveals that the 3D cardiac microtissue environment can override the developmental origin of endothelial cells to establish heart-specific traits.

## Key findings

- hiPSC-derived endothelial cells in 3D cardiac microtissues upregulate heart-specific markers like CD36 and CLDN5.
- Endothelial cells from cardiac and paraxial mesoderm acquire similar identities in cardiac microtissues.
- The tissue microenvironment, not developmental origin, dictates organ-specific endothelial cell identity in 3D models.

## Abstract

Each tissue and organ in the body has its own type of vasculature. Here, we demonstrate that organotypic vasculature for the heart can be recreated in a three-dimensional cardiac microtissue (MT) model composed of human induced pluripotent stem cell (hiPSC)-derived cardiomyocytes (CMs), cardiac fibroblasts (CFs), and endothelial cells (ECs). ECs in cardiac MTs upregulated expression of markers enriched in human intramyocardial ECs, including CD36, CLDN5, APLNR, NOTCH4, IGFBP3, and ARHGAP18. We further show that the local microenvironment largely dictates the organ-specific identity of hiPSC-derived ECs: we compared ECs derived from cardiac and paraxial mesoderm and found that, regardless of origin, they acquired similar identities upon integration into cardiac MTs. Overall, the results indicated that while the initial gene profile of ECs was dictated by developmental origin, this could be modified by the local tissue environment. This developmental “plasticity” in ECs has implications for multiple pathological and disease states.

•Compared hiPSC-derived endothelial cells (ECs) from cardiac vs. paraxial mesoderm•ECs isolated on day 6 and day 8 retained their developmental lineage history•No organ-specific EC signature in day 6 or day 8 cardiac/paraxial mesoderm ECs•3D Cardiac microtissues support organ-specific EC signature in cardiac/paraxial ECs

Compared hiPSC-derived endothelial cells (ECs) from cardiac vs. paraxial mesoderm

ECs isolated on day 6 and day 8 retained their developmental lineage history

No organ-specific EC signature in day 6 or day 8 cardiac/paraxial mesoderm ECs

3D Cardiac microtissues support organ-specific EC signature in cardiac/paraxial ECs

Stem cells research; Developmental biology; Transcriptomics