Stem cell extracellular vesicles (EVs) have been widely studied because of their excellent therapeutic potential. EVs from different types of stem cell can improve vascularization as well as aid in the treatment of cancer and neurodegenerative diseases. The skin is a complex organ that is susceptible to various types of injury. Strategies designed to restore epithelial tissues’ integrity with stem cell EVs have shown promising results. Different populations of stem cell EVs are able to control inflammation, accelerate skin cell migration and proliferation, control wound scarring, improve angiogenesis, and even ameliorate signs of skin aging. However, large-scale production of such stem cell EVs for human therapy is still a challenge. This review focuses on recent studies that explore the potential of stem cell EVs in skin wound healing and skin rejuvenation, as well as challenges of their use in therapy.

Mesenchymal stem/stromal cells (MSCs) are promising tools in cell therapy. They secrete extracellular vesicles (EVs) that carry different classes of molecules that can promote skin repair, but the mechanisms are poorly understood. Skin wound healing is a complex process that requires the activity of several signaling pathways and cell types, including keratinocytes and fibroblasts. In this study, we explored whether adipose tissue MSC-derived EVs could accelerate migration and proliferation of keratinocytes and fibroblasts, activate the AKT pathway, and promote wound healing in vivo. Furthermore, we evaluated if EV effects are miR-205 dependent. We found that MSC EVs had an average diameter of 135 nm. Keratinocytes and fibroblasts exposed to EVs exhibited higher levels of proliferation, migration, and AKT activation. Topical administration of EVs accelerated skin wound closure. Knockdown of miR-205 decreased AKT phosphorylation in fibroblasts and keratinocytes, whereas migration was decreased only in keratinocytes. Moreover, knockdown of miR-205 failed to inhibit AKT phosphorylation in fibroblasts and keratinocytes exposed to EVs. About the mechanism of EV effects, we found that incubation with EVs prevented inhibition of AKT activation by miR-205 knockdown, suggesting that EVs activate AKT independently of miR-205. In conclusion, we demonstrated that EVs are a promising tool for wound healing.

Perforin‐2 (P‐2) is a recently described antimicrobial protein with unique properties to kill intracellular bacteria. We investigated P‐2 expression pattern and cellular distribution in human skin and its importance in restoration of barrier function during wound healing process and infection with the common wound pathogen Staphylococcus aureus. We describe a novel approach for the measurement of P‐2 mRNA within individual skin cells using an amplified fluorescence in situ hybridization (FISH) technique. The unique aspect of this approach is simultaneous detection of P‐2 mRNA in combination with immune‐phenotyping for cell surface proteins using fluorochrome‐conjugated antibodies. We detected P‐2 transcript in both hematopoietic (CD45+) and non‐hematopoietic (CD45−) cutaneous cell populations, confirming the P‐2 expression in both professional and non‐professional phagocytes. Furthermore, we found an induction of P‐2 during wound healing. P‐2 overexpression resulted in a reduction of intracellular S. aureus, while infection of human wounds by this pathogen resulted in P‐2 suppression, revealing a novel mechanism by which S. aureus may escape cutaneous immunity to cause persistent wound infections.

BackgroundTreatment of spinal cord injury is dependent on neuronal survival, appropriate synaptic circuit preservation, and inflammatory environment management. In this sense, mesenchymal stem cell (MSC) therapy is a promising tool that can reduce glial reaction and provide trophic factors to lesioned neurons.MethodsLewis adult female rats were submitted to a unilateral ventral funiculus cut at the spinal levels L4, L5, and L6. The animals were divided into the following groups: IA (intramedullary axotomy), IA + DMEM (Dulbecco’s modified Eagle’s medium), IA + FS (fibrin sealant), IA + MSC (106 cells), and IA + FS + MSC (106 cells). Seven days after injury, qPCR (n = 5) was performed to assess gene expression of VEGF, BDNF, iNOS2, arginase-1, TNF-α, IL-1β, IL-6, IL-10, IL-4, IL-13, and TGF-β. The cellular infiltrate at the lesion site was analyzed by hematoxylin-eosin (HE) staining and immunohistochemistry (IH) for Iba1 (microglia and macrophage marker) and arginase-1. Fourteen days after injury, spinal alpha motor neurons (MNs), evidenced by Nissl staining (n = 5), were counted. For the analysis of astrogliosis in spinal lamina IX and synaptic detachment around lesioned motor neurons (GAP-43-positive cells), anti-GFAP and anti-synaptophysin immunohistochemistry (n = 5) was performed, respectively. Twenty-eight days after IA, the gait of the animals was evaluated by the walking track test (CatWalk; n = 7).ResultsThe site of injury displayed strong monocyte infiltration, containing arginase-1-expressing macrophages. The FS-treated group showed upregulation of iNOS2, arginase-1, proinflammatory cytokine (TNF-α and IL-1β), and antiinflammatory cytokine (IL-10, IL-4, and IL-13) expression. Thus, FS enhanced early macrophage recruitment and proinflammatory cytokine expression, which accelerated inflammation. Rats treated with MSCs displayed high BDNF-positive immunolabeling, suggesting local delivery of this neurotrophin to lesioned motoneurons. This BDNF expression may have contributed to the increased neuronal survival and synapse preservation and decreased astrogliosis observed 14 days after injury. At 28 days after lesion, gait recovery was significantly improved in MSC-treated animals compared to that in the other groups.ConclusionsOverall, the present data demonstrate that MSC therapy is neuroprotective and, when associated with a FS, shifts the immune response to a proinflammatory profile.Electronic supplementary materialThe online version of this article (10.1186/s12974-018-1268-4) contains supplementary material, which is available to authorized users.

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Caffeine is an alkaloid that is widely consumed due to its presence in drugs, coffee, tea, and chocolate. This compound passes to offspring through the placenta and milk; can cause teratogenic mutations; and reduces the formation, growth, and mass of bone. Because mesenchymal stem cells (MSCs) are responsible for generating the entire skeleton, we hypothesized that these cells are targets of caffeine. This study evaluated the osteogenic differentiation of MSCs derived from the offspring of rats treated with caffeine during pregnancy and lactation. Twenty-four adult Wistar rats were randomly divided into four groups, including one control group and three experimental groups treated with 25, 50, or 100 mg/kg of caffeine. At weaning, three 21-day-old pups from each dam in each group were euthanized for extraction of bone marrow cells for in vitro tests. Caffeine doses of 50 and 100 mg/kg significantly reduced the activity of alkaline phosphatase at 7, 14, and 21 days and the expression of collagen I at 21 days. However, the expression of gene transcripts for alkaline phosphatase, Runx-2, and bone sialoprotein, as well as the synthesis of mineralization nodules, decreased significantly in all groups treated with caffeine. The expression of osteocalcin was significantly reduced only in the group treated with 50 mg/kg caffeine. The caffeine that passes from the mother to the offspring during pregnancy and lactation reduces the osteogenic differentiation of MSCs. We propose that this reduction in the osteogenic potential of MSCs may be involved in the pathogenesis of osteopenia resulting from caffeine consumption.

Nuclear Epidermal Growth Factor Receptor (EGFR) has been associated with worse prognosis and treatment resistance for several cancer types. After Epidermal Growth Factor (EGF) binding, the ligand-receptor complex can translocate to the nucleus where it functions in oncological processes. By three-dimensional quantification analysis of super-resolution microscopy images, we verified the translocation kinetics of fluorescent conjugated EGF to the nucleus in two mesenchymal cell types: human adipose tissue-derived stem cells (hASC) and SK-HEP-1 tumor cells. The number of EGF clusters in the nucleus does not change after 10 min of stimulation with EGF in both cells. The total volume occupied by EGF clusters in the nucleus of hASC also does not change after 10 min of stimulation with EGF. However, the total volume of EGF clusters increases only after 20 min in SK-HEP-1 cells nuclei. In these cells the nuclear volume occupied by EGF is 3.2 times higher than in hASC after 20 min of stimulation, indicating that translocation kinetics of EGF differs between these two cell types. After stimulation, EGF clusters assemble in larger clusters in the cell nucleus in both cell types, which suggests specific sub-nuclear localizations of the receptor. Super-resolution microscopy images show that EGF clusters are widespread in the nucleoplasm, and can be localized in nuclear envelope invaginations, and in the nucleoli. The quantitative study of EGF-EGFR complex translocation to the nucleus may help to unravel its roles in health and pathological conditions, such as cancer.