Extracellular vesicles (EVs) are small membrane-bound particles that play a vital role in intercellular communication by facilitating the transfer of molecular cargo. In this review, we provide an overview of EV biology in corneal diseases, along with current approaches to therapeutic uses of EVs. Since EVs generally retain surface markers indicative of their cell of origin, they possess a degree of tissue specificity, which benefits drug delivery systems and highlights their potential as biomarkers to study disease processes. Further advances in technology and methodology will accelerate our understanding of EVs and help guide the field towards improved diagnostic techniques and therapeutic targets. We summarize EVs and their potential impact in medicine with a discussion of the limitations that remain in current approaches, as well as areas to focus on for future growth.

Keratoconus (KC) is a degenerative corneal disease, characterized by stromal thinning and abnormal ECM remodeling, leading to fibrosis. Corneal fibrosis is a leading cause of visual impairment. Corneal stromal keratocytes differentiate into myofibroblasts, which alters extracellular matrix (ECM) protein deposition. Nintedanib (NIN) is an antifibrotic FDA-approved tyrosine kinase inhibitor, but its function in the cornea is largely unknown. This study examined the impact of NIN within the human corneal stromal microenvironment. Healthy corneal stromal fibroblasts (HCFs) and KC fibroblasts (HKCs) in 2D and 3D in vitro cultures were treated with 1 μM or 2.5 μM NIN. Cell types were evaluated in 2D cultures for metabolic activity, viability, and migration. Protein expression of alpha-smooth muscle actin (α-SMA), collagens (COLs) 1, 3, and 5, cellular fibronectin containing extra domain A (EDA-FN), and thrombospondin-1 (TSP-1) were evaluated in 3D cultures. NIN reduced metabolic activity in HKCs without affecting cell viability. NIN reduced cell migration, downregulated COL3, COL5, EDA-FN, and TSP-1 expression in HCFs and HKCs. COL1 was upregulated in HCFs, whereas α-SMA was upregulated in HKCs. Overall, these findings demonstrate that NIN modulates corneal stromal cell migration and fibrotic marker expression, highlighting its potential as a therapeutic strategy for reducing corneal fibrosis associated with keratoconus.

Down syndrome (DS) is a common genetic disorder that has been strongly associated with keratoconus (KC). However, the underlying mechanism linking these conditions remains unexplored. KC is a corneal disorder characterized by corneal steepening, thinning, and scarring. The primary objective of this study was to determine the role of gonadotropin-releasing hormone (GnRH), follicle-stimulating hormone (FSH), and luteinizing hormone (LH) in the context of DS and KC. A total of 58 healthy (29 male, 29 female), 227 KC (167 male, 60 female), and 80 DS participants (44 male, 36 female) were recruited. Hormone levels from plasma were analyzed using enzyme-linked immunosorbent assays, and differences between disease status, sex, and age were examined. GnRH was reduced in KC compared to healthy and DS participants, particularly in males. In contrast, FSH was elevated across both sexes in DS participants compared to healthy and KC participants. LH was also significantly elevated in DS, particularly among females and among participants from 30–45 age group, mirroring the pattern seen for FSH. These cross-sectional findings reveal distinct hormonal patterns across KC and DS cohorts while providing novel descriptive data on hypothalamic–pituitary–gonadal axis hormones. Further studies are warranted to determine the relationship between gonadotropins and the phenotypic manifestations in these populations.