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Background: Fresh stem cell exosomes are usually obtained and reused in the same individual. It cannot be kept viable for a long period of time regardless of the lengthy preparation time. Freezing is typically used to preserve the viability of perishable materials and increase their lifetime. Regrettably, normal freezing of biomaterials leads to cell damage. Therefore, a cryoprotectant can save the cells from the conventional cryodamage. Sodium carboxymethylcellulose (NA-CMC) is a powdery substance that is used to manufacture bio-safe hydrofilm gels because of its high viscosity, cytocompatibility, and nonallergenic nature. Materials and Methods: Sterile CMC hydrogel was prepared, part of which was loaded with exosomal solution derived from MSCs. The gel was kept at −20°C for preservation. Two bilateral full-thickness circular skin wounds of 2-cm diameter were created on the back of experimental dogs. The wounds were at least 2.5 cm apart. Treatment started 24 hours after wound creation. Group I received CMC gel solely, whereas group II received frozen CMC exosomal gel. The gel was applied 4 times, a single application per day with 1- day interval. Results: Clinically, the frozen exosomal gel significantly promoted wound healing with no scaring. Histologically, enhanced dermal fibroblasts and organized collagen deposition were seen in the treated group. Conclusion: CMC proved to be an efficient cryoprotectant and a suitable vehicle for exosomes. Deep freezing was proven to conserve the viability, extended the preservation, and facilitated the usage of exosomal gel. This technique of preserved cell-free therapy is inexpensive, time-saving, and proficient and seems suitable for treating cutaneous wounds.

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Background: Corneal ulcer is the discontinuation of the surface epithelial layer of the cornea with variable amounts of the stroma affected. Recent research suggests that Extracellular Vesicles (EVs) of stem cells have the same effects on target cells that their parental stem cells act, these effects are brought on by paracrine signaling involves the release of cytokines and nucleic acids (DNA, mRNA, and miRNA) which may lead to alteration of the gene expression, proliferation, and differentiation of the recipient cells. Methodology: 24 male New Zealand albino rabbits were used in this study, divided randomly into 4 groups (6 rabbits per group), induction of corneal ulcers centrally in groups (I, II) and peripherally in (III, IV). Treated groups are (I, III) using topical lyophilized canine Mesenchymal Stem Cells derived EVs & control groups are (II, IV) using topical normal saline. Result: both treated groups appeared fluorescein negative at the 5th day and are characterized by rapid reepithelization significantly earlier than control groups which were still fluorescein positive. AS-OCT (Anterior Segment Optical Coherence Tomography) showed well-healed epithelium with intact and homogenous stroma on the 5th day in both treated groups, but control groups showed irregular arrangements of epithelial plaques and presented some abnormalities as stromal fibrosis and sub-epithelial cyst formation. Histopathology in both treated groups showed the development of a complete layer of epithelium within 1week which increased in rows at 2nd and 3rd weeks of treatment and the stromal edema decreased with time unlike control groups that showed weak fragmented epithelium development, sub-epithelial hemorrhage and vascularization. These findings prove that EVs have the ability to heal corneal wounds even if in the peripheral parts of the cornea that are deficient in limbal stem cells. Conclusion: In terms of safety, quality, regulatory concerns, and cost, EVs are superior to corneal transplantation and live stem cell therapy.

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