Abstract
Vitamin D3, known to regulate bone homeostasis, has recently been shown to have many pleiotropic effects in different tissues and organs due to the presence of its receptor in a wide range of cells. Our previous study demonstrated that vitamin D3 was able to increase the wound healing respect to the control sample, 24 h after cutting, without however leading to a complete repair. The aim of the study was to combine vitamin D3 with silver nanoparticles to possibly enable a faster reparative effect. The results showed that this association was capable of inducing a complete wound healing only after 18 h. Moreover, a treatment of vitamin D3 + silver nanoparticles yielded a small percentage of keratinocytes vimentin-positive, suggesting the possibility that the treatment was responsible for epithelial to mesenchymal transition of the cells, facilitating wound healing repair. Since vitamin D3 acts via sphingolipid metabolism, we studied the expression of gene encoding for the metabolic enzymes and protein level. We found an increase in neutral sphingomyelinase without involvement of neutral ceramidase or sphingosine kinase2. In support, an increase in ceramide level was identified by Ultrafast Liquid Chromatography–Tandem Mass Spectrometry, suggesting a possible involvement of ceramides in wound healing process.
Highlights
The production of vitamin D3 or cholecalciferol occurs in the skin by ultraviolet radiation from sunlight starting from its precursor 7-dehydrocholesterol, located in the keratinocyte membranes of the basal and spinous layer of epidermis [1]
It was reported that 100 nM vitamin D3 (VD3) was a physiological dose [16] and that AgNPs at 25 ppm, 2.5 ppm, and 0.25 ppm do not have a toxic effect in a model of human reconstructed epidermis [17]
100 nM, 133 nM, and 166 nM VD3 induced more than 80% cell viability; 1% and 2% DMSO were used as positive controls
Summary
The production of vitamin D3 or cholecalciferol occurs in the skin by ultraviolet radiation from sunlight starting from its precursor 7-dehydrocholesterol, located in the keratinocyte membranes of the basal and spinous layer of epidermis [1]. Keratinocytes are the only cells in the body containing the entire pathway of vitamin D3 and here calcitriol negatively regulates its own levels [3]. This is relevant considering that keratinocytes are located in the stratum basale of epidermis that rests on the basal lamina separating the dermis and epidermis. Subsequent studies demonstrated that physiological doses of calcitriol were able to regulate keratinocytes differentiation [5] and pharmacological concentrations exerted a pro-apoptotic effect in keratinocytes [6]. It is known that wound repair takes place thanks to the proliferation of keratinocytes and their transdifferentiation to mesenchymal cells epithelial–mesenchymal transition (EMT) [9]. Among EMT forms, the type 2 is specific of wound healing [10]
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