Mesenchymal Stem Cell-Derived Exosomes for Keratoconus: A Novel Therapeutic Approach

Abstract

Keratoconus (KC) is a progressive corneal ectatic disorder with limited treatment options addressing its underlying pathophysiology. Current therapies, including corneal cross-linking and transplantation, focus on halting progression rather than reversing damage. Mesenchymal stem cell-derived exosomes (MSC-Exo) have emerged as promising cell-free therapeutic agents with regenerative, anti-inflammatory, and immunomodulatory properties. This short communication synthesizes current evidence on MSC-Exo for KC treatment. Preclinical studies demonstrate that MSC-Exo enhances keratocyte proliferation, reduces fibrosis and inflammation, modulates extracellular matrix proteins, and promotes epithelial wound healing. Exosomes from various MSC sources show therapeutic efficacy across in vitro and animal models. While clinical evidence remains limited, early studies support safety and feasibility for ocular applications. MSC-Exo represents a promising therapeutic approach capable of modulating key KC pathological mechanisms, warranting further clinical investigation.

INTRODUCTION

Keratoconus (KC) is a bilateral, progressive corneal ectatic disorder, characterized by stromal thinning, corneal protrusion, and irregular astigmatism, leading to significant visual impairment.1 The pathogenesis involves complex interactions between genetic predisposition, environmental factors, oxidative stress, and inflammatory mediators, resulting in keratocyte apoptosis, extracellular matrix (ECM) degradation, and biomechanical weakening.2

Current management strategies are primarily palliative. Corneal cross-linking (CXL) effectively halts progression but cannot reverse existing damage. Advanced cases require surgical intervention through keratoplasty, which carries risks of rejection, infection, and donor tissue shortage.3 These limitations underscore the need for regenerative therapies addressing the underlying molecular pathology.

Mesenchymal stem cells (MSCs) have shown promise in corneal regeneration through paracrine signaling mediated by extracellular vesicles, particularly exosomes.4 These nano-sized vesicles (30–150 nm) carry bioactive cargo including proteins, lipids, and nucleic acids that modulate intercellular communication and tissue repair. MSC-derived exosomes (MSC-Exo) retain the therapeutic properties of parent cells – including anti-inflammatory, anti-fibrotic, and proregenerative effects – while avoiding risks associated with cell transplantation.5

This communication reviews the current evidence on MSC-Exo as a novel therapeutic approach for KC, synthesizing findings from preclinical studies and discussing clinical translation potential.

CURRENT EVIDENCE

Preclinical studies

Recent investigations have demonstrated the therapeutic potential of MSC-Exo in KC models. Shojaati et al. showed that human corneal MSC-derived exosomes significantly reduced corneal fibrosis and inflammation through miRNA-mediated mechanisms.6 The exosomes modulated key ECM proteins, including collagen I, lumican, and keratocan, while suppressing matrix metalloproteinases implicated in KC pathogenesis.

Samaeekia et al. demonstrated that corneal MSC-Exo enhanced epithelial wound healing in scratch assay models, with rapid cellular internalization and improved migration patterns.7 This finding is particularly relevant for post-CXL recovery, where epithelial damage can delay healing and cause patient discomfort.

Lozano et al. characterized the molecular cargo of exosomes from KC patients, revealing altered miRNA and protein profiles compared to healthy controls.8 Notably, KC-derived exosomes increased pathological keratocyte migration and proliferation, while healthy MSC-Exo restored cellular homeostasis. This differential effect suggests that exosome therapy could reverse molecular abnormalities characteristic of KC.

Animal model studies have further validated these findings. MSC-Exo administered via topical, intrastromal, or subconjunctival routes demonstrated enhanced corneal transparency, reduced inflammation, and improved stromal architecture in rabbit and mouse models mimicking KC-like pathology.9

Clinical translation

While KC-specific clinical trials are lacking, related studies provide encouraging evidence. Del Barrio et al. conducted a pilot study using adipose-derived stem cells in advanced KC patients, demonstrating safety and improved corneal transparency.10 Although this study used whole cells rather than exosomes, it established the feasibility of MSC-based therapy for KC.

Clinical investigations in other ocular conditions have shown MSC-Exo to be safe and effective. Studies in dry eye disease and neurotrophic keratopathy reported improved ocular surface health without adverse events, supporting the translational potential for KC applications.11

Mechanisms of action

MSC-Exo exerts therapeutic effects through multiple mechanisms relevant to KC pathophysiology:

1. Anti-inflammatory modulation: Exosomal miRNAs downregulate pro-inflammatory cytokines (interleukin-1 beta and tumor necrosis factor-alpha) implicated in KC progression5

2. ECM remodeling: MSC-Exo restores the expression of structural proteins (keratocan and lumican) while suppressing pathological matrix metalloproteinases6

3. Antifibrotic effects: Reduction in α-smooth muscle actin and SPARC expression prevents myofibroblast transformation and scarring12

4. Cellular regeneration: Enhanced keratocyte proliferation and survival through growth factor delivery and antiapoptotic signaling7

5. Immunomodulation: Exosomes modulate immune responses, potentially beneficial for postsurgical recovery and reducing inflammation-driven progression13

ADVANTAGES OVER CURRENT THERAPIES

MSC-Exo offers several advantages compared to existing KC treatments:

• Cell-free therapy: Eliminates risks of immune rejection, tumorigenesis, and ectopic differentiation associated with cell transplantation

• Stability: Exosomes are more stable than cells, allowing easier storage and transportation

• Targeted delivery: Can be administered topically or locally, minimizing systemic exposure

• Regenerative potential: Unlike CXL, which stabilizes tissue, exosomes actively promote tissue repair

• Combinatorial approach: Can potentially enhance outcomes when combined with existing treatments.

CHALLENGES AND FUTURE DIRECTIONS

Several challenges must be addressed before clinical implementation:

• Standardization: Lack of standardized protocols for exosome isolation, characterization, and quality control hampers reproducibility. Establishing good manufacturing practice compliant procedures is essential14

• Optimal source: While various MSC sources (adipose, bone marrow, and corneal) show efficacy, comparative studies are needed to identify the most therapeutically relevant source for KC

• Delivery methods: The optimal route of administration – topical drops, intrastromal injection, or scaffold-based delivery – requires systematic evaluation

• Dosing regimens: Dose–response relationships and treatment frequency need establishment through rigorous preclinical studies

• Bioengineering potential: Engineering exosomes with specific therapeutic cargo (e.g., antifibrotic miRNAs) could enhance efficacy.15

CONCLUSION

MSC-derived exosomes represent a promising therapeutic paradigm for KC, offering a cell-free approach to address underlying molecular pathology. Preclinical evidence consistently demonstrates their ability to modulate inflammation, restore ECM homeostasis, and promote corneal regeneration. While clinical translation remains in early stages, the favorable safety profile in related ocular applications supports continued development.

Future research should focus on standardizing production protocols, optimizing delivery strategies, and conducting well-designed clinical trials. Given the limited treatment options for KC and the regenerative potential of MSC-Exo, this approach warrants accelerated investigation to potentially transform KC management and improve patient outcomes.

Conflicts of interest

There are no conflicts of interest.

Funding Statement

Nil.