Human Umbilical Cord Blood Endothelial Progenitor Cell-Derived Extracellular Vesicles Control Important Endothelial Cell Functions

Circulating endothelial progenitor cells (EPCs) play a pivotal role in the repair of diseases in which angiogenesis is required. Although they are a potentially valuable cell therapy tool, their clinical use remains limited due to suboptimal storage conditions and, especially, long-term immune rejection. EPC-derived extracellular vesicles (EPC-EVs) may be an alternative to EPCs given their key role in cell-cell communication and expression of the same parental markers. Here, we investigated the regenerative effects of umbilical cord blood (CB) EPC-EVs on CB-EPCs in vitro. After amplification, EPCs were cultured in a medium containing an EVs-depleted serum (EV-free medium). Then, EVs were isolated from the conditioned medium with tangential flow filtration (TFF). The regenerative effects of EVs on cells were investigated by analyzing cell migration, wound healing, and tube formation. We also analyzed their effects on endothelial cell inflammation and Nitric Oxide (NO) production. We showed that adding different doses of EPC-EVs on EPCs does not alter the basal expression of the endothelial cell markers nor change their proliferative potential and NO production level. Furthermore, we demonstrated that EPC-EVs, when used at a higher dose than the physiological dose, create a mild inflammatory condition that activates EPCs and boosts their regenerative features. Our results reveal for the first time that EPC-EVs, when used at a high dose, enhance EPC regenerative functions without altering their endothelial identity.

Abstract 3665: Umbilical cord blood endothelial progenitor cell-derived extracellular vesicles control important endothelial cell functions

Background: Circulating endothelial progenitor cells (EPCs) play a pivotal role in vascular regeneration and the repair of diseases in which angiogenesis is required, including ischemia and tissue transplantation. Although they are a potentially valuable cell therapy tool, their clinical use remains limited due to suboptimal storage conditions and especially, immune rejection. Even if these cells have been shown to be tolerated by the immune system, their in vivo long-term effects still remain to be elucidated. EPC-derived extracellular vesicles (EPC-EVs) may be an attractive alternative to EPCs given their key role in cell-cell communication and expression of the same parental markers. In this study, we investigated the regenerative effects of umbilical cord blood EPC-EVs on EPCs in vitro.

Methods: EPCs were obtained from human umbilical cord blood (CB) and characterized by flow cytometry. After amplification, EPCs were cultured in a medium containing an EVs-depleted serum (EV-free medium). Then the conditioned medium was used to isolate the EVs with Tangential Flow Filtration (TFF). The EVs were characterized by a series of tests defining their size, number, and protein content. The regenerative effects of EPC-EVs on endothelial cells were investigated by analyzing cell migration, wound healing, and tube formation. We also analyzed the effect of EPC-EVs on endothelial cell inflammation and NO production.

Results: We showed that adding different doses of EPC-EVs on EPCs does not alter the basal expression of the endothelial cell markers CD31, CD144, and KDR, nor change their proliferative potential and NO production level. Furthermore, we demonstrated that EPC-EVs, when used at a higher than physiologic dose, create a mild inflammatory condition that activates EPCs and boosts their regenerative features like migration and tube formation functions.

Conclusions: Our results reveal for the first time that EPC-EVs, when used at a high dose, could enhance EPC regenerative functions without altering their endothelial identity.

Citation Format: Sawssen Ben Fraj, Sina Naserian, Bileyle Lorenzini, Sylvie Goulinet, Philippe Mauduit, Georges Uzan, Houda Haouas. Umbilical cord blood endothelial progenitor cell-derived extracellular vesicles control important endothelial cell functions. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3665.

Producing vesicle-free cell culture additive for human cells extracellular vesicles manufacturing

A new paradigm has emerged recently, which consists in shifting from cell therapy to a more flexible acellular "extracellular vesicle (EV) therapy" approach, thereby opening a new and promising field in nanomedicine. Important technical limitations have still to be addressed for the large-scale production of clinical-grade EV. Cells are cultured in media supplemented with human platelet lysate (hPL) (xenogenic-free) or GMP-grade fetal calf serum (FCS). However, these additives contain high amounts of EV that cannot be separated from cell-secreted -EV. Therefore, cells are generally maintained in additive-free medium during the EV secretion phase, however this can substantially limit their survival. In the present work, we developed a method to prepare vesicle-free hPL (EV-free hPL) or vesicle-free FCS (EV-free FCS) using tangential flow filtration (TFF). We show a very efficient EV depletion (>98%) for both pure hPL and FCS, with a highly conserved protein content. Culture medium containing our EV-free additives supported the survival of human bone marrow MSC (BM-MSC). MSC could survive at least 216 h, their conditioned medium being collected and changed every 72 h. Both the cell survival and the cumulative EV production were substantially higher than in the starving conditions classically used for EV production. In EV-free hPL containing medium, we show that purified EV kept their morphologic and molecular characteristics throughout the production. Finally, we tested our additives with 3 other cell types, human primary Endothelial Colony Forming Cells (ECFC) and two non-adherent human cell lines, Jurkat and THP-1. We confirmed that both EV-free hPL and FCS were able to maintain cell survival and EV production for at least 216 h. Our method provides therefore a new option to help producing large amounts of EV from virtually any mammalian cells, particularly those that do not tolerate starvation. This method can apply to any animal serum for research and development purpose. Moreover, EV-free hPL is clinical-grade compatible and allows preparing xenobiotic-free media for massive therapeutic EV production in both 2D (cell plates) and 3D (bioreactor) setting.

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