Exosomes in Corneal Homeostasis and Wound Healing

PURPOSE: The cornea is a transparent avascular tissue that serves as the first line of defense against opportunistic pathogens and provides a smooth refractive surface for vision. Due to its external location, the cornea is vulnerable to stress from the outer environment. This can lead to corneal epithelial breakdown and subsequent corneal disease. Extracellular vesicles (EVs) are nano-sized vesicles enclosed within a lipid bilayer that are secreted by all cells in the body and play a key role in cell-to-cell communication. Within the cornea field, EVs and exosomes, the latter of which represents a subpopulation of small EVs, have emerged as potential therapies for treating corneal diseases and have increased our understanding of the mechanisms by which EVs, and more specifically, exosomes released by stressed or unhealthy cells, leads to corneal dysfunction and disease. METHODS: We conducted a literature search using PubMed and Google Scholar using keywords relevant to exosomes, extracellular vesicles, and cornea. We reviewed the literature focusing on EV studies on corneal wound healing and therapy. RESULTS: This review provides a comprehensive overview of the current state of exosome biology as it relates to corneal disease and wound healing. Studies to date provide compelling data indicating that EVs and exosomes may play an integral role in the maintenance of corneal homeostasis. EVs and exosomes also have exciting potential as therapeutics in corneal wound healing and disease; and their presence in tear fluid may serve as potential diagnostic biomarkers for ocular and systemic diseases. CONCLUSION: While corneal exosome biology is still in its infancy state, continued progress in this area will improve our understanding of the functional capacity of these small vesicles in the human cornea and may lead to the development of novel regenerative therapies.