Comparison of breast skin resistance against protease digestion between young and elderly individual based on attenuation-of-sound values
Authors: Miura Katsutoshi , Iwashita Toshihide 
Published: November 2024

The skin is a gateway through which bacteria can establish infection. Evidence has shown that the components of the skin change with age, with elderly individuals exhibiting fewer epidermal rete ridges, dermal collagen, and elastic fibers. In the present study, paraffin sections of breast skin were digested with proteolytic enzymes of bacterial origin, after which skin fragility was assessed by observing attenuation-of-sound (AOS) images over time. Accordingly, studies have shown that AOS values are correlated with tissue viscosity and can serve as a numerical indicator of protein density. Breast skin sections were digested using two types of collagenases and actinase E, a broader peptidase. Notably, our results showed that skin sections from young and elderly patients showed resistance to digestion with the two types of collagenases. However, the epidermis and dermis were successfully digested using actinase over time. All layers of the epidermis, except for the keratin layer, were digested, whereas collagen and elastic fibers in the dermis were broken down, along with a decrease in AOS levels. Although actinase affected both young and aged skin, elderly skin showed much lower AOS values given its naturally reduced thickness and density due to aging. This finding suggests that older patients experience greater damage from proteolytic enzymes. AOS is an excellent approach to visualizing the process of protease digestion over time and statistically comparing proteolytic damage.The skin is a gateway through which bacteria can establish infection. Evidence has shown that the components of the skin change with age, with elderly individuals exhibiting fewer epidermal rete ridges, dermal collagen, and elastic fibers. In the present study, paraffin sections of breast skin were digested with proteolytic enzymes of bacterial origin, after which skin fragility was assessed by observing attenuation-of-sound (AOS) images over time. Accordingly, studies have shown that AOS values are correlated with tissue viscosity and can serve as a numerical indicator of protein density. Breast skin sections were digested using two types of collagenases and actinase E, a broader peptidase. Notably, our results showed that skin sections from young and elderly patients showed resistance to digestion with the two types of collagenases. However, the epidermis and dermis were successfully digested using actinase over time. All layers of the epidermis, except for the keratin layer, were digested, whereas collagen and elastic fibers in the dermis were broken down, along with a decrease in AOS levels. Although actinase affected both young and aged skin, elderly skin showed much lower AOS values given its naturally reduced thickness and density due to aging. This finding suggests that older patients experience greater damage from proteolytic enzymes. AOS is an excellent approach to visualizing the process of protease digestion over time and statistically comparing proteolytic damage.