Mesenchymal Stem Cells-Derived Exosomes Improved Healing of a Rabbit Model of Corneal Alkali Burn: A Histological and Immunohistochemical Study

Abstract Introduction: Corneal alkali burns represent a potentially blinding ocular injury that requires immediate treatment. Exosomes are cell-free therapies used to treat corneal alkali burns. Aim: We aimed to examine the possible role of mesenchymal stem cell (MSC)-derived exosomes on the healing of induced corneal alkali burn in adult male rabbits by histological and immunohistochemical techniques. Materials and Methods: Forty adult male New Zealand white rabbits were divided into group I (control); group II (alkali burn), which was left for spontaneous healing; and group III (exosomes treated): rabbits were given a subconjunctival injection of 100 µg of purified MSC-exosomes after 1 h from corneal alkali burn induction. The injection of exosomes was repeated every other day. All groups were subdivided into two subgroups: subgroups a and b, where corneal specimens were collected after 7 and 14 days, respectively. Characterization of exosomes was performed using transmission electron microscopy. A gross examination of the cornea was performed on days 1, 7, and 14. Corneas were collected and then subjected to proper histological techniques (hematoxylin and eosin, periodic acid Schiff’s base, Masson’s trichrome stains, transforming growth factor-beta, and vascular endothelial growth factor). Histomorphometric study and statistical analysis were carried out. Results: MSC-derived exosomes in group III improved the healing of corneal alkali burn by inhibiting angiogenesis and inflammation, enhancing corneal reepithelization, providing better organization of newly formed stromal collagen fibers, and proper healing of Descemet’s membrane as well as decreasing expression of transforming growth factor-β. Conclusion: Early and repeated subconjunctival injection of MSC-derived exosomes is effective in healing corneal alkali burns in adult rabbits.