Abstract
Purpose :
There is overwhelming evidence in animal studies demonstrating that mesenchymal stem cells (MSCs) can promote epithelial healing in the cornea after injuries, mainly through secreted trophic factors. Because exosomes are involved in cell-to-cell communication, we investigated the corneal mesenchymal stromal cell-derived exosomes (cMSC exo) as the potential paracrine effectors of MSCs in healing corneal epithelial wounds.
Methods :
Cornea-derived MSCs (cMSC) were isolated from healthy cadaver donors. The secretome was collected after 72 hours and exosomes were isolated using the differential ultracentrifugation. Morphology and size of exosomes were determined by TEM imaging and dynamic light scattering. Exosomes were also characterized by western blotting and probing for exosome markers CD9, CD63, CD81, and HSP70. Cellular uptake of exosomes was studied in vitro by incubating calcein-stained exosomes with either MSCs, human corneal epithelial cells (HCEC), or macrophages, and in vivo by scratching cornea of C57BL/6J mice and topical treatment with stained exosome for 4hrs. Effect of exosome on wound closure and healing was measure in vitro using scratch assay and in vivo by removing a 2-mm area of the central epithelium from mice cornea and treating topically with exosome for 30 minutes.
Results :
characterization studies showed that exosomes derived from human corneal MSCs were morphologically round and ranged between 30 – 260 nm in diameter with a Z-average of 71 nm. They also expressed several exosomes markers including CD63, CD81, CD9, and HSP70. Stained cMSC exosome were successfully taken up by MSCs, HCECs, and macrophages after 4h hrs of incubation. Topical treatment of scratched mouse cornea with stained exosomes indicated penetration of exosome into stroma and uptake of exosomes by corneal epithelial cells. Mechanically wounded HCECs that were incubated in MSC exosomes had 30.1 ± 14 percent remaining wound area after 16 hours while control had 72.9 ± 8 percent (P<0.005). Similar significant effect was observed in vivo: after 24 hours, cMSC exo-treated mice had 77.5 ± 3.0 percent corneal wound healing compared to 41.6 ± 7.0 percent in MEM-α group (P <0.05).
Conclusions :
Human cMSC exosomes can significantly accelerate corneal epithelial wound healing, and thus, may serve as targets for potential therapeutic interventions in ocular surface diseases.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.