A Fluid Dynamic In Vitro System to Study the Effect of Hyaluronic Acid Administration on Collagen Organization in Human Skin Explants.

Hyaluronic acid (HA) is an unbranched polysaccharide particularly abundant in the extracellular matrix (ECM) of soft connective tissues. In humans, about 50% of the total HA in the organism is localized in the skin. HA plays an essential role in the hydration of the ECM, in the regulation of tissue homeostasis, in the resistance to mechanical stimuli/forces, and in the modulation of tissue regeneration. For these reasons, HA is widely used in regenerative medicine and cosmetics. In this study we used an innovative fluid dynamic system to investigate the effects of a cross-linked macrostructural HA formulation on dermal collagen of healthy human skin explants. The good preservation of skin explants provided by the bioreactor allowed applying refined high-resolution microscopy techniques to analyze in situ the HA-induced modifications on the ECM collagen fibrils up to 48 h from the application on the skin surface. Results demonstrated that this HA formulation, commercially proposed for subcutaneous injection, may act on dermal ECM also when applied transcutaneously, improving ECM hydration and modifying the organization of the collagen fibrils. These findings, obtained by the original combination of explanted human skin use with an advanced culture system and multiscale imaging techniques, are consistent with the volumizing and anti-aging effect of HA.