Abstract
ABSTRACTScanning acoustic microscopy (SAM) can assess tissue stiffness by calculating the speed of sound (SOS) through tissues. SOS increases as tissue stiffness increases. Sensitivity to protease digestion depends on protein type, concentration, and modification. We analyzed the SOS images of formalin-fixed paraffin-embedded skin sections from elderly, young, diabetic, and nondiabetic subjects, as well as chronic and acute wounds. SAM provided high-resolution histology similar to LM and revealed characteristic SOS alteration following pepsin treatment. SOS values of dermis samples from elderly subjects (especially females) were lower than those of younger adults, which was indicative of age-related dermal softening and loosening. SOS values of elderly females were lower than those of younger females and elderly males. Dermal SOS showed a positive correlation with epidermal thickness. SOS values of epidermis of elderly subjects were higher than those of younger adults and showed a rapid decline 0.5h after protease digestion. Reticular dermis of diabetic patients exhibited greater pepsin resistance than that of nondiabetic patients. Chronic wounds exhibited greater SOS values and pepsin resistance than acute wounds. SOS variation with aging, diabetes mellitus, and wound fibrosis reflected histological and mechanical changes associated with senescence and disease duration. Epidermal thickness reflects age-related changes in dermal stiffness.
Highlights
Increasing age and exposure to environmental factors are known to affect the physical properties of skin [1,2]
Differences in speed of sound (SOS) imaging associated with skin aging and gender
SOS skin images of younger adults (Figure 1(a)) showed a greater number of regions comprised of thick bundles in the reticular and papillary dermis, which corresponded to a dense collagen network
Summary
Increasing age and exposure to environmental factors are known to affect the physical properties of skin [1,2]. Light microscopy (LM), in conjunction with special ancillary techniques (such as immunostaining), is useful for evaluation of both structural and biochemical changes during histological evaluation of biopsy specimens; assessment of mechanical properties that are relevant for diagnosis of several pathological conditions is not possible by LM. To understand the effect of histological changes on the mechanical properties of tissues, it is necessary to use techniques to measure elastic properties across usual thickness slides for routine histology [3]. Atomic force microscopy-based nanoindentation is a candidate technique for mechanical testing [3,6]. This method offers higher resolution in length scale, identification of the observed material is difficult on light microscopic histology
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