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Wound healing is essential for skin repair after injury, and it consists of hemostasis, inflammation, re-epithelialization, and remodeling phases. Successful re-epithelialization, which relies on proliferation and migration of epidermal keratinocytes, requires a reduction in tissue inflammation. Therefore, understanding the molecular mechanism underlying the transition from inflammation to re-epithelialization will help to better understand the principles of wound healing. Currently, the in vivo functions of specific microRNAs in wound healing are not fully understood. We observed that miR-31 expression is strongly induced in wound edge keratinocytes, and is directly regulated by the activity of NF-κB and signal transducer and activator of transcription 3 signaling pathways during the inflammation phase. We used miR-31 loss-of-function mouse models to demonstrate that miR-31 promotes keratinocyte proliferation and migration. Mechanistically, miR-31 activates the Ras/mitogen-activated protein kinase signaling by directly targeting Rasa1, Spred1, Spred2, and Spry4, which are negative regulators of the Ras/mitogen-activated protein kinase pathway. Knockdown of these miR-31 targets at least partially rescues the delayed scratch wound re-epithelialization phenotype observed in vitro in miR-31 knockdown keratinocytes. Taken together, these findings identify miR-31 as an important cell-autonomous mediator during the transition from inflammation to re-epithelialization phases of wound healing, suggesting a therapeutic potential for miR-31 in skin injury repair.

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A soft, pasty, high-moisture surface defect occurs with progressive brining of Mozzarella cheese. Addition of calcium is traditionally used to prevent this defect but the underlying mechanism is not clear. Mozzarella cheese was formed into a cylinder inside brine on its plane surface to ensure semi-infinite, unidirectional mass transfer and placed into brine containing 0, 0.1, or 0.25% (wt/wt) calcium chloride. To monitor the effect on cheese composition of calcium in brine, we measured calcium and water contents of the cheese during brining. The extent of calcium loss from the cheese decreased significantly with the addition of calcium. Addition of calcium to a final concentration of 0.25% decreased the loss of calcium from 94.13 to 18.22% from the outside region of the cheese after 30 d, and the water content of the cheese was decreased from 67.8 to 48.8%. To further elucidate the effect of calcium in brine, the Boltzmann method was used to determine the effective diffusion coefficient value, and low-field nuclear magnetic resonance was used to measure the cheese transversal relaxation time. The migration of calcium interfered with salt diffusion. At the end of brining, the amount of water bound to the protein of the cheese significantly increased. Addition of calcium to a final concentration of 0.25% diminished the proportion of bound water by 20.96%. In conclusion, addition of calcium hinders the diffusion of sodium and modifies the distribution of water in Mozzarella cheese during brining.

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Milk fat globule membrane polar lipids (MPL) are increasingly used as the surface-active components for emulsions in many infant food products. However, the precise effect of the emulsifier MPL on the digestion of lipids during gastrointestinal digestion has not been elucidated. This study investigated the lipid digestion of droplets covered with MPL with different sizes in a simulated in vitro infant gastrointestinal digestion assay. The well-used surface-active component casein was used as a control. Four types of emulsions were formulated: small and large droplets covered with MPL concentrate (MPL-S and MPL-L, with volumetric means of 0.35 ± 0.01 and 4.04 ± 0.01 μm, respectively), and small and large droplets covered with casein (CN-S and CN-L, with volumetric means of 0.44 ± 0.01 and 4.09 ± 0.03 μm, respectively). The emulsions were subjected to in vitro gastrointestinal digestion using a semidynamic model mimicking infant digestion. Through the determination of particle size evolution, zeta-potential, and microstructure of emulsions, the lipid droplets covered with MPL were found to be more stable than that of the CN-S and CN-L during gastrointestinal digestion. Moreover, although CN-S and CN-L showed a higher initial lipolysis rate at the beginning of gastric digestion, droplets covered by MPL exhibited a significantly higher amount of free fatty acid release during later digestion. The amount of free fatty acid release of the emulsions in both gastric and intestinal digestion could be generally classified as MPL-S ≥ MPL-L > CN-S > CN-L. Our study highlights the crucial role of MPL in the efficient digestion of emulsions and brings new insight for the design of infant food products. Figure 6. Total free fatty acid (FFA) release of droplets from different emulsions during in vitro gastric (A) and intestinal digestion (B). MPL-S and MPL-L indicate small and large globules covered with milk polar lipids, and CN-S and CN-L indicate small and large globules covered with casein, respectively. Error bars represent the SD of triplicate experiments.