Mesenchymal Stem Cell-Derived Extracellular Vesicles and Plant-Derived Nanovesicles as Cell-Free Therapies for Thermal Burn Healing: A Systematic Review of Preclinical Evidence and Delivery Strategies

Background/Objectives: Thermal injuries represent a significant global health burden, often complicated by hypertrophic scarring, chronic inflammation, and delayed re-epithelialization. While Mesenchymal Stem Cell (MSC) transplantation has shown promise, its clinical translation is hindered by risks of tumorigenicity and immunological concerns. This study evaluates the efficacy of cell-free Extracellular Vesicle (EV) therapy—derived from both mammalian MSCs and plant sources (PDNVs)—as standardized, off-the-shelf alternatives. This study synthesizes evidence focusing on re-epithelialization velocity, angiogenic activity, and anti-fibrotic outcomes, while assessing the impact of second-generation delivery scaffolds on therapeutic durability. Methods: Conducted in accordance with PRISMA 2020 guidelines and registered in PROSPERO (CRD420261305379), this review interrogated PubMed, Scopus, Embase, and Web of Science for studies published between 2015 and 2026. Eligible studies included in vivo animal models of thermal injury using purified vesicles from mammalian MSC sources or plant-derived nanovesicles compared with placebo, standard care, or untreated controls. Data were synthesized narratively; methodological quality was appraised using the SYRCLE risk of bias tool and compliance with MISEV guidelines. Results: Synthesis of 50 studies revealed that vesicle-based interventions consistently accelerate wound closure and improve histological healing. Mammalian ADSC-derived vesicles demonstrated superior anti-fibrotic effects via the miR-192-5p and miR-125b-5p axes, while hUC-MSC vesicles attenuated systemic inflammatory signaling via miR-181c. Plant-derived nanovesicles (PDNVs) showed potent antioxidant and re-epithelialization effects, with emerging potential as engineered genetic carriers. Crucially, advanced delivery systems, including bioactive hydrogels and microneedle patches, were repeatedly associated with improved local retention and more durable effects than bolus injections. Conclusions: Vesicle-based therapies show consistent pro-healing signals in preclinical models, suggesting source-dependent profiles: MSC-derived vesicles excel in immunomodulation and anti-fibrotic remodeling, while PDNVs provide a scalable, low-immunogenicity platform. As a cell-free strategy, these therapies circumvent the safety risks of live cell transplantation. This review identifies a critical shift toward second-generation delivery scaffolds to overcome the clearance crisis of topical applications, emphasizing the need for harmonized MISEV-aligned characterization in future clinical translation.