Biophysical properties of Striae Distensae evaluated in vivo using non-invasive assays.

BACKGROUND: Striae Distensae (SD) or stretch marks are manifestations of epidermal atrophy that occurs after tissue tearing due to rapid growth or over-stretching and are characterized by distinct microstructural features. The objective of this in vivo study was to investigate the biophysical properties of SD lesions, including skin barrier function, skin surface hydration, mechanical properties, and chromophore concentrations, compared to normal adjacent skin.

METHODS: Non-invasive methods were used on 29 volunteers with SD to characterize: (i) visual appearance (visual assessment and clinical imaging), (ii) skin barrier function by measuring transepidermal water loss, (iii) skin surface hydration using corneometry (skin capacitance), (iv) mechanical properties measuring skin elasticity under vacuum and surface propagation of a sonic wave, (v) the presence of erythema and pigmentation using diffuse reflectance spectroscopy, and (vi) the levels of interleukin-1α on the skin surface.

RESULTS: No difference was observed in skin barrier function and a slight difference in skin hydration between the striae and adjacent uninvolved skin. Viscoelasticity measurements showed that SD lesions were significantly less firm, less elastic, and less deformable than normal skin (P < 0.05). Mechanical anisotropy was increased in SD compared to normal skin, reflecting the skin surface anisotropy reported previously. Diffuse reflectance spectroscopy showed no differences in the apparent hemoglobin concentrations between SD and control. Skin pigmentation and light scattering values were significantly lower in SD (P < 0.001) compared to adjacent skin and there was no correlation between them indicating independent causes: lower melanin production for pigmentation and altered collagen fiber structure in the dermis for light scattering.

CONCLUSIONS: Based on these results, the distinct microstructural features characterizing SD lesions are accompanied by changes in the mechanical and optical properties. These changes however do not seem to affect the skin barrier and moisturization properties.