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Ali R Djalilian, John Kink, Medi Eslani, Reza Dana, Peiman Hematti; Exosomes from corneal mesenchymal stem cells modulate the immunophenotype of macrophages. Invest. Ophthalmol. Vis. Sci. 2018;59(9):3310. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Mesenchymal stem cells (MSCs) have been under study for their therapeutic immunomodulatory properties. At ARVO 2017 we reported that cornea derived mesenchymal stem cells can modulate the immunophenotype of macrophages in a distinct manner. We demonstrated that the modulatory effects are mediated through MSC secreted factors. In this study, we focused on exosomes / extra-cellular vesicles derived from MSCs to determine their specific modulatory effects on macrophages.
Peripheral blood mononuclear cells were isolated from the buffy coats by density-gradient separation. Monocytes were isolated using anti-human CD14 microbeads. Purified CD14+ monocytes were plated in cell culture plates at a concentration of 106 per well in IMDM media supplemented with 10% human serum blood type AB. Monocytes were cultured for 7 days to differentiate into macrophages. On day +7, macrophages were supplemented with fresh media and either co-cultured with human corneal MSCs (in transwells) to obtain MSC educated macrophages (MEMs), or else treated with exosomes isolated from human corneal MSCs to get exosome educated macrophages (EEMs). After 3 days, the macrophages were collected and subjected to flow cytometry.
Corneal MSCs were found to produce extracellular vesicles that primarily consisted of exosome-sized vesicles. By flow cytometry, macrophages educated using corneal MSCs (cMEM) or corneal exosomes (cEEM) showed similar but a distinct surface marker profile. For the M2 markers, the mean fluorescent intensity (MFI) of CD206, PD-L2 and CD39 for both MEM and EEM were significantly elevated compared to controls, however CD206, PD-L1, PD-L2 was also significantly higher in the EEMs compared to the MEMs. Interestingly, in contrast both CD163 and CD16 were significantly lower in the EEMs compared to the MEMs. For the M1 markers, HLA-DR, there was no difference in surface expression in either the MEMs or EEMs, while CD86 was significantly lower in the MEMs compared to both controls and EEMs.
These results demonstrate the distinct modulatory effects of cornea MSCs and cornea MSC derived exosomes on macrophages. Further functional and gene expression studies are underway to better characterize the exosomes and exosome educated macrophages. Likewise, additional studies are needed to determine the therapeutic potential of cornea MSC exosomes in ocular inflammatory disorders.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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