Isolation methods of large and small extracellular vesicles derived from cardiovascular progenitors: A comparative study

Since the discovery of the beneficial therapeutical effects of extracellular vesicles (EVs), these agents have been attracting great interest as next-generation therapies. EVs are nanosized membrane bodies secreted by all types of cells that mediate cell-cell communication. Although the classification of different subpopulations of EVs can be complex, they are broadly divided into microvesicles and exosomes based on their biogenesis and in large and small EVs based on their size. As this is an emerging field, current investigations are focused on basic aspects such as the more convenient method for EV isolation. In the present paper, we used cardiac progenitor cells (CPCs) to study and compare different cell culture conditions for EV isolation as well as two of the most commonly employed purification methods: ultracentrifugation (UC) and size-exclusion chromatography (SEC). Large and small EVs were separately analysed. We found that serum starvation of cells during the EV collecting period led to a dramatic decrease in EV secretion and major cell death. Regarding the isolation method, our findings suggest that UC and SEC gave similar EV recovery rates. Separation of large and small EV-enriched subpopulations was efficiently achieved with both purification protocols although certain difference in sample heterogeneity was observed. Noteworthy, while calnexin was abundant in large EVs, ALIX and CD63 were mainly found in small EVs. Finally, when the functionality of EVs was assessed on primary culture of adult murine cardiac fibroblasts, we found that EVs were taken up by these cells, which resulted in a pronounced reduction in the proliferative and migratory capacity of the cells. Specifically, a tendency towards a larger effect of SEC-related EVs was observed. No differences could be found between large and small EVs. Altogether, these results contribute to establish the basis for the use of EVs as therapeutic platforms, in particular in regenerative fields.