Single-cell characterization of neovascularization using hiPSC-derived endothelial cells in a 3D microenvironment

Comparative Evaluation of Endothelial Colony-Forming Cells from Cord and Adult Blood vs. Human Embryonic Stem Cell-Derived Endothelial Cells: Insights into Therapeutic Angiogenesis Potential

The discovery of endothelial progenitor cells has revolutionized our understanding of postnatal blood vessel formation, with endothelial colony-forming cells (ECFCs) emerging as key players in vasculogenesis. Among various ECFC sources, cord blood-derived ECFCs (CB-ECFCs) are of particular interest due to their superior proliferative and clonogenic potential and their ability to promote vascular network formation. Human embryonic stem cell-derived endothelial cells (hESC-ECs) have also shown potential in regenerative medicine, though their vasculogenic efficacy remains unclear compared to CB- and adult blood-derived ECFCs (AB-ECFCs). This study aimed to directly compare the angiogenic and vasculogenic capabilities of CB-ECFCs, AB-ECFCs, and hESC-ECs in vitro and in vivo. Our results demonstrated that CB-ECFCs had a significantly higher proliferation rate than both AB-ECFCs and hESC-ECs (p < 0.01). In tube formation assays, CB-ECFCs exhibited superior ability to form capillary-like structures compared to hESC-ECs (p < 0.0001) and AB-ECFCs (p < 0.01). In vivo, CB-ECFCs significantly improved blood flow recovery in ischemic tissue (p < 0.01), outperforming both AB-ECFCs and hESC-ECs, with no significant recovery observed in the latter two groups. These findings suggest that CB-ECFCs represent a more effective cell source for therapeutic angiogenesis, while further optimization is needed to enhance the efficacy of hESC-ECs for clinical applications. Future research should explore the molecular mechanisms underlying the superior regenerative potential of CB-ECFCs and focus on improving the stability and functionality of stem cell-derived ECs for therapeutic use.

Protocol to generate a microfluidic vessels-on-chip platform using human pluripotent stem cell-derived endothelial cells

Here, we present a protocol for producing a microfluidic vessel-on-chip platform using human pluripotent stem cell-derived endothelial cells (SC-ECs). We describe steps for manufacturing the 3D-printed chip, cell culturing to generate SC-ECs, hydrogel patterning, and the formation and cultivation of barrier-forming vessels. We then detail procedures for the retrieval of cells and media from the open microfluidic chip platform to enable multi-omics analysis. For complete details on the use and execution of this protocol, please refer to Marder et al.1.

BCL6B-dependent suppression of ETV2 hampers endothelial cell differentiation

BACKGROUND

B-cell CLL/lymphoma 6 member B (BCL6B) operates as a sequence-specific transcriptional repressor within the nucleus, playing crucial roles in various biological functions, including tumor suppression, immune response, stem cell self-renew, and vascular angiogenesis. However, whether BCL6B is involved in endothelial cell (EC) development has remained largely unknown. ETS variant transcription factor 2 (ETV2) is well known to facilitate EC differentiation. This study aims to determine the important role of BCL6B in EC differentiation and its potential mechanisms.

METHODS

Doxycycline-inducible human induced pluripotent stem cell (hiPSC) lines with BCL6B overexpression or BCL6B knockdown were established and subjected to differentiate into ECs and vessel organoids (VOs). RNA sequencing analysis was performed to identify potential signal pathways regulated by BCL6B during EC differentiation from hiPSCs. Quantitative real-time PCR (qRT-PCR) was used to detect the expression of pluripotency and vascular-specific marker genes expression. EC differentiation efficiency was determined by Flow cytometry analysis. The performance of EC was evaluated by in vitro Tube formation assay. The protein expression and the vessel-like structures were assessed using immunofluorescence analysis or western blot. Luciferase reporter gene assay and chromatin immunoprecipitation (ChIP)-PCR analysis were used to determine the regulatory relationship between BCL6B and ETV2.

RESULTS

Functional ECs and VOs were successfully generated from hiPSCs. Notably, overexpression of BCL6B suppressed while knockdown of BCL6B improved EC differentiation from hiPSCs. Additionally, the overexpression of BCL6B attenuated the capacity of derived hiPSC-ECs to form a tubular structure. Furthermore, compared to the control VOs, BCL6B overexpression repressed the growth of VOs, whereas BCL6B knockdown had little effect on the size of VOs. RNA sequencing analysis confirmed that our differentiation protocol induced landscape changes for cell/tissue/system developmental process, particularly vascular development and tube morphogenesis, which were significantly modulated by BCL6B. Subsequent experiments confirmed the inhibitory effect of BCL6B is facilitated by the binding of BCL6B to the promoter region of ETV2, led to the suppression of ETV2's transcriptional activity. Importantly, the inhibitory effect of BCL6B overexpression on EC differentiation from hiPSCs could be rescued by ETV2 overexpression.

CONCLUSIONS

BCL6B inhibits EC differentiation and hinders VO development by repressing the transcriptional activity of ETV2.

Stem cell-derived vessels-on-chip for cardiovascular disease modeling

The metabolic syndrome is accompanied by vascular complications. Human in vitro disease models are hence required to better understand vascular dysfunctions and guide clinical therapies. Here, we engineered an open microfluidic vessel-on-chip platform that integrates human pluripotent stem cell-derived endothelial cells (SC-ECs). The open microfluidic design enables seamless integration with state-of-the-art analytical technologies, including single-cell RNA sequencing, proteomics by mass spectrometry, and high-resolution imaging. Beyond previous systems, we report SC-EC maturation by means of barrier formation, arterial toning, and high nitric oxide synthesis levels under gravity-driven flow. Functionally, we corroborate the hallmarks of early-onset atherosclerosis with low sample volumes and cell numbers under flow conditions by determining proteome and secretome changes in SC-ECs stimulated with oxidized low-density lipoprotein and free fatty acids. More broadly, our organ-on-chip platform enables the modeling of patient-specific human endothelial tissue and has the potential to become a general tool for animal-free vascular research.