Research ArticleCELL THERAPY

Circulating exosomes derived from transplanted progenitor cells aid the functional recovery of ischemic myocardium

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Science Translational Medicine  22 May 2019:
Vol. 11, Issue 493, eaau1168
DOI: 10.1126/scitranslmed.aau1168

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Tracking therapeutic effects

Stem and progenitor cells are being pursued for a number of regenerative medicine applications; however, tracking cells after transplant and determining therapeutic efficacy can be challenging. Saha et al. isolated exosomes from blood to monitor human cardiosphere-derived cells (CDCs) and cardiac progenitor cells (CPCs) transplanted into rat hearts after myocardial infarction. They found that they could purify CDC/CPC-derived exosomes based on major histocompatibility complex mismatch and that the exosomes contained microRNAs associated with myocardial recovery. Exosomes produced from CPCs and CDCs in culture differed in contents from exosomes produced by transplanted cells in vivo. This study suggests that circulating exosomes can be used to noninvasively monitor transplanted cells.

Abstract

The stem cell field is hindered by its inability to noninvasively monitor transplanted cells within the target organ in a repeatable, time-sensitive, and condition-specific manner. We hypothesized that quantifying and characterizing transplanted cell–derived exosomes in the recipient plasma would enable reliable, noninvasive surveillance of the conditional activity of the transplanted cells. To test this hypothesis, we used a human-into-rat xenogeneic myocardial infarction model comparing two well-studied progenitor cell types: cardiosphere-derived cells (CDCs) and c-kit+ cardiac progenitor cells (CPCs), both derived from the right atrial appendage of adults undergoing cardiopulmonary bypass. CPCs outperformed the CDCs in cell-based and in vivo regenerative assays. To noninvasively monitor the activity of transplanted CDCs or CPCs in vivo, we purified progenitor cell–specific exosomes from recipient total plasma exosomes. Seven days after transplantation, the concentration of plasma CPC-specific exosomes increased about twofold compared to CDC-specific exosomes. Computational pathway analysis failed to link CPC or CDC cellular messenger RNA (mRNA) with observed myocardial recovery, although recovery was linked to the microRNA (miRNA) cargo of CPC exosomes purified from recipient plasma. We further identified mechanistic pathways governing specific outcomes related to myocardial recovery associated with transplanted CPCs. Collectively, these findings demonstrate the potential of circulating progenitor cell–specific exosomes as a liquid biopsy that provides a noninvasive window into the conditional state of the transplanted cells. These data implicate the surveillance potential of cell-specific exosomes for allogeneic cell therapies.

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