# Selective MicroRNA Packaging Reveals Distinct Core Signatures in Human Mesenchymal-Stromal-Cell-Derived Extracellular Vesicles

## TL;DR

This study identifies unique microRNA signatures in extracellular vesicles derived from human mesenchymal stromal cells, which may help improve their use in therapies.

## Contribution

The study provides a standardized profiling of microRNA cargo in MSC-derived extracellular vesicles under clinically relevant conditions.

## Key findings

- NanoString profiling identified 590 mature microRNAs, with 42 significantly differentially expressed between MSC-EVs and parental MSCs.
- Five microRNAs were highly expressed in MSCs, five in MSC-EVs, and fifteen of the top twenty were abundant in both.
- Functional analysis showed enrichment in biological processes like cell proliferation, differentiation, and immune regulation.

## Abstract

Mesenchymal stromal cells (MSCs) have demonstrated therapeutic efficacy across numerous clinical applications, with evidence suggesting their paracrine effects, particularly through extracellular vesicles (EVs), possibly driving functional outcomes. In this study we perform the comprehensive characterization of microRNA expression profiles in human MSC-derived EVs (MSC-EV) compared to their parental cells, cultured under clinically relevant xeno-free conditions. MSCs were isolated from the bone marrows of healthy donors and characterised according to the International Society for Cellular Therapy criteria, while MSC-EVs were isolated using differential ultracentrifugation and validated according to the International Society for Extracellular Vesicle guidelines. NanoString profiling identified 590 mature microRNAs expressed across both populations, with 42 being significantly differentially expressed between MSC-EVs and parental MSCs. Five microRNAs were distinctly highly expressed in MSCs and five in MSC-EVs, while fifteen of the top twenty most abundant microRNAs showed high expression in both populations. MicroRNA expression patterns were validated in an independent cohort. Functional pathway analysis of differentially expressed microRNAs showed enrichment of key biological processes including cell proliferation, differentiation, and immune regulation. This standardised profiling approach develops our understanding of MSC/MSC-EV microRNA cargo, using a transparent methodological approach that allows for the improved comparability of datasets for the development and advancement of MSC-EV therapeutics.