From decoding the perception of tightness to a clinical proof of soothing effects derived from natural ingredients in a moisturizer.
International journal of cosmetic science
OBJECTIVE: To decode the feeling of skin tightness after application of a cosmetic product and how to soothe this discomfort. To pursue this aim, we considered the ingredient's effect on stratum corneum (SC) biomechanics to differentiate between consumers prone to tightness from those that are not and correlate these effects with mechanoreceptor activation.METHODS: In vivo clinical trials were used to assess the tightness perception dichotomy between groups of Caucasian women; in vitro experiments were used to measure the mechanical stresses induced in the SC after cleanser and moisturizer application; and in silico simulations were used to illustrate how the measured mechanical stresses in the SC result in the development of strains at the depth of cutaneous mechanoreceptors, triggering tightness perceptual responses.RESULTS: Before any cream application, women prone to tightness tend to have a more rigid SC than their less sensitive counterparts, however cleanser application increases SC stiffness in all women. Surprisingly, no correlation was found between tightness perception and hydration measurements by the Corneometer or barrier function, as evaluated by transepidermal water loss (TEWL). Self-declared tightness and dryness scores were strongly associated with a self-described sensitive skin. After application of the optimized moisturizing formula, Osmoskin containing natural waxes with good filming properties, consumers report a strong decrease in tightness and dryness perception. These results match with laboratory experiments where the cleanser was shown to increase SC drying stresses by 34%, while subsequent application of Osmoskin decreased stresses by 48%. Finite element modeling (FEM), using experimental results as input, elucidates the differences in perception between the two groups of women. It makes clear that Osmoskin changes the mechanical status of the stratum corneum, producing strains in underlying epidermis that activates multiple cutaneous mechano-receptors at a level correlated with the self-perceived comfort.CONCLUSION: Integration of the in vivo, in vitro, and in silico approaches provides a novel framework for fully understanding how skin tightness sensations form and propagate, and how these sensations can be alleviated through the design of an optimized moisturizer.
View details for DOI 10.1111/ics.12797
View details for PubMedID 35775314
Biomechanical Analysis of the Ross Procedure in an Ex Vivo Left Heart Simulator.
World journal for pediatric & congenital heart surgery
2022; 13 (2): 166-174
BACKGROUND: Neo-aortic pulmonary autografts often experience root dilation and valve regurgitation over time. This study seeks to understand the biomechanical differences between aortic and neo-aortic pulmonary roots using a heart simulator.METHODS: Porcine aortic, neo-aortic pulmonary, and pulmonary roots (n=6) were mounted in a heart simulator (parameters: 100 mm Hg, 37 °C, 70 cycles per minute, 5.0 L/min cardiac output). Echocardiography was used to study root distensibility (percentage change in luminal diameter between systole and diastole) and valve function. Leaflet motion was tracked with high-speed videography. After 30 min in the simulator, leaflet thickness (via cryosectioning), and multiaxial modulus (via lenticular hydrostatic deformation testing) were obtained.RESULTS: There were no significant differences between aortic and neo-aortic pulmonary leaflet motion, including mean opening velocity (218 vs 248 mm/s, P=.27) or mean closing velocity (116 vs 157 mm/s, P=.12). Distensibility was similar between aortic (8.5%, 1.56 mm) and neo-aortic pulmonary (7.8%, 1.12 mm) roots (P=.59). Compared to virgin controls, native pulmonic roots exposed to systemic pressure for 30 min had reduced leaflet thickness (630 vs 385 m, P=.049) and a reduced Young's modulus (3,125 vs 1,089 kPa, P=.077). In contrast, the aortic roots exposed to pressure displayed no significant difference in aortic leaflet thickness (1,317 vs 1,256 m, P=.27) or modulus (5,931 vs 3,631 kPa, P=.56).CONCLUSIONS: Neo-aortic pulmonary roots demonstrated equivalence in valve function and distensibility but did experience changes in biomechanical properties and morphology. These changes may contribute to long-term complications associated with the Ross procedure.
View details for DOI 10.1177/21501351211070288
View details for PubMedID 35238706