Controlled mechanical vibration and impacts on skin biology

Different biological models have shown how mechanical stimulation may induce physiological responses from solicited cells, tissues, or organs. In models of cultured skin cells, the frequency of the mechanical stress appears to be a paramount parameter, generating a biological response in some cells, particularly from dermal fibroblasts. Our objective was to explore in ex vivo human skin explants the effects of mechanical stimulation.

Mechanical stimulations were provided by a torque test device, with different end effectors, able to generate cyclic strains at different frequencies (from 40 to 120 Hz). Skin explant samples were stimulated twice daily by the device for one minute, over 10 days.

At days 0, 5, and 10, samples were processed by immunohistological procedures, allowing some structural dermal proteins to be quantified (fluorescence). As compared to untreated skin explant samples, the stimulation procedure clearly led some proteins of the dermal-epidermal and some dermal proteins to be overexpressed. This stimulation was found to be frequency-dependent, with the greatest overall increases occurring at 60 and 90 Hz.

For the first time, ultrafast ultrasound imaging in vitro (phantom mimicking skin mechanical properties) was used to analyze mechanical waves transmitted to the skin layers as a function of end effector shape.