Endothelial cells provide a niche for placental hematopoietic stem/progenitor cell expansion through broad transcriptomic modification

Abstract

Umbilical cord blood (UCB) is an attractive source of hematopoietic stem cells (HSCs). However, the number of HSCs in UCB is limited, and attempts to amplify them in vitro remain inefficient. Several publications have documented amplification of hematopoietic stem/progenitor cells (HSPCs) on endothelial or mesenchymal cells, but the lack of homogeneity in culture conditions and HSC definition impairs direct comparison of these results. We investigated the ability of different feeder layers, mesenchymal progenitors (MPs) and endothelial cells (ECs), to amplify hematopoietic stem/progenitor cells. Placental derived HSPCs (defined as Lin(-)CD45(-/dim)CD34(+)CD38(-)CD90(+)) were maintained on confluent feeder layers and the number of cells and their marker expression were monitored over 21 days. Although both types of feeder layers supported hematopoietic expansion, only endothelial cells triggered amplification of Lin(-)CD45(-/dim)CD34(+)CD38(-)CD90(+) cells, which peaked at 14 days. The amplified cells differentiated into all cell lineages, as attested by in vitro colony-forming assays, and were capable of engraftment and multi-lineage differentiation in sub-lethally irradiated mice. Mesenchymal progenitors promoted amplification of CD38(+) cells, previously defined as precursors with more limited differentiation potential. A competitive assay demonstrated that hematopoietic stem/progenitor cells had a preference for interacting with endothelial cells in vitro. Cytokine and transcriptomic analysis of both feeder cell types identified differences in gene expression that correlated with propensity of ECs and MPs to support hematopoietic cell amplification and differentiation respectively. Finally, we used RNA sequencing of endothelial cells and HSPCs to uncover relevant networks illustrating the complex interaction between endothelial cells and HSPCs leading to stem/progenitor cell expansion.

Endothelial Cells Provide a Notch-Dependent Pro-Tumoral Niche for Enhancing Breast Cancer Survival, Stemness and Pro-Metastatic Properties

“…This observation was in line with previous work by our group on E4-ECs effect on hematopoietic stem cell (HSC) expansion [8], [36]. Our results showed that without contact, E4-ECs were not capable of sustaining BCC survival under starvation.…”

Angiocrine functions of organ-specific endothelial cells

“…Direct contact between haematopoietic cells and ECs is essential for the self-renewal and differentiation of HSPCs 45, 46, 47 . Compared with mesenchymal cells, ECs are more efficient at expanding umbilical cord blood-derived HSPCs 50 . Other angiocrine factors, such as prostaglandin E2 (PGE2) (refs 51, 52), pleiotrophin 53 and epidermal growth factor (EGF) 54 , drive haematopoietic reconstitution, which establishes ECs as a physiological repository of HSPC-supportive factors.…”

Human mesenchymal and murine stromal cells support human lympho-myeloid progenitor expansion but not maintenance of multipotent haematopoietic stem and progenitor cells

“…This finding is in line with the observation that in murine HSC niches, both MSCs and endothelial cells are required for the HSC maintenance. [28][29][30] It will be interesting to learn whether MSCs together with endothelial cells or other cell types may allow for the in vitro expansion of HSCs/MPPs. Altogether, these data support our previous conclusion that testing for the erythroid potential of CD133 C CD34 C HSPCs provides a simple but meaningful assay to test for the presence of HSCs/MPPs.…”