Objective: Chronically ill patients heal recalcitrant ulcerative wounds more slowly. Human adipose-derived stem cells (hADSCs) play an important role in tissue regeneration and exosomes secreted by hADSC contribute to their paracrine signaling. In addition to cytokines, lipids and growth factors, hADSC secrete mRNA, miRNA, and long noncoding (lnc) RNA into exosomes. In this study we examined the role of lncRNA MALAT1 (metastasis-associated lung adenocarcinoma transcript 1), an abundant lncRNA in exosomes from conditioned media (CM), on cell migration and ischemic wound healing.Approach: CM and isolated exosomes from hADSC were applied to human dermal fibroblast (HDF) in scratch assays and electric cell-substrate impedance sensing (ECIS) assays. CM was also applied to a rat model of ischemic wound healing and wound closure was followed.Results: CM stimulated cell migration of HDFs in vitro by 48%. CM stimulated the closure of ischemic wounds in a rat model 50% faster than unconditioned media. The depletion of MALAT1 in adipose-derived stem cell (ADSC) CM significantly reduced cell migration. Since MALAT1 is secreted into exosomes, a purified population of exosomes was applied to HDF where they enhanced cell migration in a similar manner to FGF-2 or basic fibroblast growth factor (bFGF) in ECIS wound healing assays. The uptake of exosomes by HDF was shown using dynasore, an inhibitor that blocks clathrin- and caveolin-dependent endocytosis. Depletion of MALAT1 in hADSC with antisense oligonucleotides resulted in exosomes without MALAT1. These exosomes had an effect similar to the unconditioned, control media in ECIS assays.Innovation: Exosomes contain lncRNA MALAT1 and other factors that have the potential to stimulate HDF cell migration and angiogenesis involved in wound healing without applying stem cells to wounds.Conclusion: Our results show the potential of using topically applied ADSC-derived exosomes containing MALAT1 for treating ischemic wounds. This allows for harnessing the power of stem cell paracrine signaling capabilities without applying the cells.

Advertisements targeted at the elderly population suggest that antioxidant therapy will reduce free radicals and promote wound healing, yet few scientific studies substantiate these claims. To better understand the potential utility of supplemental antioxidant therapy for wound healing, we tested the hypothesis that age and tissue ischemia alter the balance of endogenous antioxidant enzymes. Using a bipedicled skin flap model, ischemic and non-ischemic wounds were created on young and aged rats. Wound closure and the balance of the critical antioxidants superoxide dismutase and glutathione in the wound bed were determined. Ischemia delayed wound closure significantly more in aged rats. Lower superoxide dismutase 2 and glutathione in non-ischemic wounds of aged rats indicate a basal deficit due to age alone. Ischemic wounds from aged rats had lower superoxide dismutase 2 protein and activity initially, coupled with decreased ratios of reduced/oxidized glutathione and lower glutathione peroxidase activity. De novo glutathione synthesis, to restore redox balance in aged ischemic wounds, was initiated as evidenced by increased glutamate cysteine ligase. Results demonstrate deficiencies in two antioxidant pathways in aged rats that become exaggerated in ischemic tissue, culminating in profoundly impaired wound healing and prolonged inflammation.

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Increasing evidence shows that limited energy and nutrient exchange is associated with age‐related impairment of wound healing. Ketone bodies, including β‐Hydroxybutyrate (βHB), are naturally occurring energy substrates, which may augment wound healing. We hypothesized that oral ketone supplementation without dietary restriction would enhance wound closure in young and aged Fisher rats by improving blood flow and supplying an alternative energy substrate. In our preliminary studies, we measured the magnitude and duration of ketosis following administration of a single 6.5g/kg dose of ketone precursors: R,S‐1,3‐Butanediol (KS1), Na+/K+ βHB salt and medium chain triglyceride (MCT) oil 1:1 mixture (KS2), or water in young and aged fisher 344 rats (n=6). Substances were administered through an intragastric gavage and whole blood samples (10 μl) were acquired for analysis of glucose and βHB at 0, 0.5, 1, 1.5, 2, 4, 8, and 12 hours following administration. Using an ischemic wound‐healing model, the ketogenic supplements were added to a standard diet fed ad libitum for 28 days. Laser Doppler imaging of the ischemic peri‐wound tissue every 7 days demonstrated significantly increased blood flow in young rats (n=10) fed KS1 at day 14 and 28 (p<0.001) and KS2 at day 7, 14, and 28 (p<0.01). In aged rats, blood flow was significantly increased in KS1‐fed at day 14 and KS2‐fed at days 7 and 14 (p<0.05). Wound size was significantly smaller in young rats fed KS1 and KS2 at 11 and 14 days following wound creation (p<0.05). In aged rats, KS1‐fed wounds were significantly smaller at days 11 and 14 (p<0.05) and in KS2‐fed at days 11, 14, and 28 (p<0.05). Wound healing improved by 3 days in aged KS1‐fed, 7 days in young KS2‐fed, and 10 days in aged KS2‐fed. Grant Funding Source: Funded by the Office of Naval Research