Mini-review finds preclinical promise but substantial barriers for amniotic membrane extracellular vesicles in ophthalmology

A 2026 narrative mini-review concludes that extracellular vesicles derived from human amniotic membrane show neuroprotective, anti-inflammatory, antioxidant and pro-regenerative activity in experimental models of eye disease, but remain preclinical and face major manufacturing, delivery, safety and regulatory hurdles before clinical use. The review synthesizes a limited and heterogeneous literature, much of it based on cultured cells or small-animal models rather than patients.

The authors searched PubMed and other relevant databases for combinations of “human amniotic membrane,” “extracellular vesicles,” “exosomes,” “microvesicles” and “ophthalmology.” Because the number of studies was limited and their methods varied, they did not perform a formal systematic review. Instead, the mini-review critically summarizes key findings, methodological limitations and unresolved translational questions, following the MISEV 2023 guidance for extracellular-vesicle research.

Human amniotic membrane is a layered tissue containing epithelial and mesenchymal stromal cells, and it has long been used in skin and corneal wound repair. Its secretome includes an extracellular-vesicle fraction alongside soluble factors and extracellular-matrix components. Recent studies indicate that vesicles from amniotic epithelial cells and mesenchymal stromal cells carry proteins, microRNAs, lipids and other signaling molecules, but their molecular cargo and functional contributions remain incompletely characterized.

Preclinical evidence links human amniotic membrane-derived vesicles with several potentially relevant biological functions. In mouse and rat models of chronic liver fibrosis, vesicles reduced inflammatory and fibrotic measures, suppressed hepatic stellate-cell activation and migration, and shifted macrophages from a pro-inflammatory toward a pro-regenerative phenotype. In contrast, one study of peripheral blood mononuclear cells found that the EV-free fraction, rather than the EV-enriched fraction, produced the measured immunomodulatory effects. The authors therefore caution that outcomes depend on the cellular source, target cell and biological context, and that soluble mediators may account for some reported effects.

In ocular models, vesicles derived from amniotic mesenchymal stromal cells protected retinal pigment epithelial cells from oxidative stress in vitro and in mice. The reported effects included activation of the PI3K/Akt/FoxO3 pathway, less apoptosis and reactive oxygen species, maintenance of retinal thickness and improved photoreceptor survival in age-related macular degeneration models. In diabetic retinopathy, subconjunctival administration of EV-rich conditioned medium delayed retinal vascular pathology, reduced lens opacity and lessened ocular inflammation in rats.

Other experiments examined the optic nerve, ocular surface and cornea. Intravitreal injection of EV-enriched conditioned medium from amniotic mesenchymal stromal cells or epithelial cells lowered intraocular pressure and preserved retinal ganglion-cell survival in a rat glaucoma model, although the study could not separate vesicle effects from those of soluble factors. Topical epithelial-cell-derived vesicles improved tear-film stability, reduced corneal staining and promoted epithelial regeneration in a mouse dry-eye model. In mouse corneal alkali-burn experiments, the vesicles accelerated re-epithelialization and reduced opacity. Reported molecular and signaling findings included activation of focal adhesion kinase, modulation of extracellular-matrix genes and attenuation of the TGF-beta/SMAD2/3 fibrotic pathway.

These results support further investigation of human amniotic membrane vesicles as cell-free candidates, but they do not establish clinical efficacy. Isolation and enrichment methods used across the literature include ultracentrifugation, affinity purification, size-exclusion chromatography, precipitation kits and filtration or concentration of conditioned media. These approaches can differ substantially in particle recovery, purity and retention of soluble proteins. Studies using EV-enriched conditioned medium are especially difficult to interpret because the specific contribution of vesicles cannot be separated confidently from co-isolated factors.

Translation also faces variability associated with donor, gestational age and anatomical region of the membrane. The review reports that vesicles have been observed at the apical surface of amniotic epithelial cells in the central region, but static microscopy alone cannot establish a specific biogenesis pathway. It also states that no Good Manufacturing Practice manufacturing protocol specific to human amniotic membrane-derived vesicles has yet been reported, although characterization and quality-control work on mesenchymal-cell vesicular fractions provides a starting point. Validated potency assays, reproducible release criteria and larger-animal studies remain necessary.

Route of administration presents further uncertainty. Topical eye drops may lose vesicles through tear turnover, nasolacrimal drainage and the corneal epithelial barrier, while subconjunctival or intravitreal delivery can improve tissue access but requires injection and may introduce procedure-related risks. Biomaterial depots, ligand targeting and membrane engineering are being investigated to improve retention and delivery, but dosing, biodistribution, clearance, long-term efficacy and reproducibility remain unresolved. The established ophthalmic safety record of amniotic membrane tissue also cannot be directly applied to purified vesicles, particularly for intraocular administration.

Overall, the mini-review describes human amniotic membrane-derived vesicles as a promising experimental platform for regenerative ophthalmology, not as an established treatment. The strongest available evidence comes from cell cultures and small-animal models, with incomplete molecular attribution and substantial technical heterogeneity limiting direct comparisons. Before clinical development can proceed, the field will need standardized preparation and characterization, functional potency testing, rigorous contaminant and immunogenicity screening, delivery optimization, long-term safety evaluation and regulatory oversight under frameworks for complex biological medicinal products.

Subject of Research: Preclinical evidence and translational limitations for human amniotic membrane extracellular vesicles in ophthalmology

Article Title: Activities of human amniotic membrane extracellular vesicles with a focus on ophthalmology

Article References: Lulli, M., Calcagno, S., Peppicelli, S., Isoldi, G., Kaur, I.-P., Papucci, L., Magnelli, L., Mannini, A., & Schiavone, N. (2026). Activities of human amniotic membrane extracellular vesicles with a focus on ophthalmology. Molecular Biology Reports, 53(1), Article 1593. https://doi.org/10.1007/s11033-026-12756-0

Image Credits: AI Generated

DOI: 10.1007/s11033-026-12756-0

Keywords: human amniotic membrane, extracellular vesicles, ophthalmology, regenerative medicine, corneal repair, retinal disease, ocular inflammation, cell-free therapy, extracellular-vesicle manufacturing, Activities, human, amniotic