A novel in vitro stripping method to study geometry of corneocytes with fluorescent microscopy: example of aging skin

Corneocytes: Relationship between Structural and Biomechanical Properties

BACKGROUND

Skin is the interface between an organism and the external environment, and hence the stratum corneum (SC) is the first to withstand mechanical insults that, in certain conditions, may lead to integrity loss and the development of pressure ulcers. The SC comprises corneocytes, which are vital elements to its barrier function. These cells are differentiated dead keratinocytes, without organelles, composed of a cornified envelope and a keratin-filled interior, and connected by corneodesmosomes (CDs).

SUMMARY

The current review focusses on the relationship between the morphological, structural, and topographical features of corneocytes and their mechanical properties, to understand how they assist the SC in maintaining skin integrity and in responding to mechanical insults. Key Messages: Corneocytes create distinct regions in the SC: the inner SC is characterized by immature cells with a fragile cornified envelope and a uniform distribution of CDs; the upper SC has resilient cornified envelopes and a honeycomb distribution of CDs, with a greater surface area and a smaller thickness than cells from the inner layer. The literature indicates that this upward maturation process is one of the most important steps in the mechanical resistance and barrier function of the SC. The morphology of these cells is dependent on the body site: the surface area in non-exposed skin is about 1,000-1,200 μm2, while for exposed skin, for example, the cheek and forehead, is about 700-800 μm2. Corneocytes are stiff cells compared to other cellular types, for example, the Young's modulus of muscle and fibroblast cells is typically a few kPa, while that of corneocytes is reported to be about hundreds of MPa. Moreover, these skin cells have 2 distinct mechanical regions: the cornified envelope (100-250 MPa) and the keratin matrix (250-500 MPa).

Assessment of non-invasive techniques and herbal-based products on dermatological physiology and intercellular lipid properties

Skin is the largest external organ of the human body. It acts as a barrier to protect the human body from environmental pollution, mechanical stress, and excessive water loss. The defensive function resides primarily on top of the epidermis layer commonly known as stratum corneum (SC). Human SC consists of three major lipids, namely ceramide, free fatty acid, and cholesterol that comprise approximately 50%, 25%, and 25% of the total lipid mass, respectively. The optimal composition of SC lipids is the vital epidermal barrier function of the skin. On the other hand, skin barrier serves to limit passive water loss from the body, reduces chemical absorption from the environment, and prevents microbial infection. In contrast, epidermal lipids are important to maintain the cell structure, growth and differentiation, cohesion and desquamation as well as formation of a permeability barrier. Multiple non-invasive in vivo approaches were implemented on a regular basis to monitor skin physiological and intercellular lipid properties. The measurement of different parameters such as transepidermal water loss (TEWL), hydration level, skin elasticity, collagen intensity, melanin content, sebum, pH, and tape stripping is essential to evaluate the epidermal barrier function. Novel non-invasive techniques such as tape stripping, ultrasound imaging, and laser confocal microscopy offer higher possibility of accurate and detailed characterisation of skin barrier. To date, these techniques have also been widely used to determine the effects of herbal plants in dermatology. Herbal plants have been traditionally used for ages to treat a variety of skin diseases, as reported by the World Health Organisation (WHO). Their availability, lower cost, and minimal or no side effects have created awareness among society, thus increase the demand for natural sources as the remedy to treat various skin diseases. This paper reviews several non-invasive techniques and evaluations of herbal-based product in dermatology.

Nanoscale compositional mapping of cells, tissues, and polymers with ringing mode of atomic force microscopy

Recently developed sub-resonance tapping modes (such as Digital Pulse, Peak Force Tapping, HybriD, etc.) of atomic force microscopy (AFM) allow imaging of compositional contrast of (bio)materials and biological cells down to the nanoscale. Here we report on a powerful extension of those modes, “ringing” mode, which more than doubles the number of non-trivial physical channels that can be collected with a regular sub-resonance tapping. It can simultaneously record five new additional compositional parameters related to adhesive and viscoelastic properties of the sample surface: the restored (averaged) adhesion, adhesion height, pull-off neck height, detachment distance, and detachment energy losses. Ringing mode can be up to 20 times faster and showing fewer artifacts compared to the existing sub-resonance tapping modes. Ringing mode is based on an analysis of ringing signal of the AFM cantilever after detaching the AFM probe from the sample surface (this signal is currently treated as noise, and typically filtered out in the existing modes). We demonstrate that this new mode allows recording robust and unique information on fixed human epithelial cells, corneocyte skin flakes, and polymers used for bioimplants.

Nontraditional Methods to Evaluate Wound Healing

BACKGROUND

Traditional evaluation of wound healing is sometimes subjective. It is necessary to develop qualitative and quantitative methods to enable more efficient and accurate evaluation of wounds. Recently, new techniques have been introduced and the correspondence between these techniques and clinician judgment is critical.

OBJECTIVE

Some nontraditional techniques that analyze wound healing were reviewed, which include measurements of the wound area, tissue color, skin barrier function, skin humidity, and keratinocyte morphology.

METHODS

This review article is based on medical research that focuses on the evaluation of wound healing.

RESULTS

Software-based and advanced device-based techniques generally provide more accurate and precise results than traditional ones, such as the ruler-based technique. Measurement of tissue color can also help to identify the type of tissue. Evaluation of skin barrier function can assist clinicians to analyze functional restoration of skin, whereas skin humidity demonstrates the exudate production status of the wound. In addition, keratinocyte morphology in the wound bed indicates quality of wound healing and side effects of treatment.

CONCLUSION

There is no gold standard method for qualitative and quantitative evaluation of wound healing. It is important to understand the type of wound, sample size, results obtained, advantages, and limitations of each technique.

Recovery of aging-related size increase of skin epithelial cells: in vivo mouse and in vitro human study

The size increase of skin epithelial cells during aging is well-known. Here we demonstrate that treatment of aging cells with cytochalasin B substantially decreases cell size. This decrease was demonstrated on a mouse model and on human skin cells in vitro. Six nude mice were treated by topical application of cytochalasin B on skin of the dorsal left midsection for 140 days (the right side served as control for placebo treatment). An average decrease in cell size of 56±16% resulted. A reduction of cell size was also observed on primary human skin epithelial cells of different in vitro age (passages from 1 to 8). A cell strain obtained from a pool of 6 human subjects was treated with cytochalasin B in vitro for 12 hours. We observed a decrease in cell size that became statistically significant and reached 20–40% for cells of older passage (6–8 passages) whereas no substantial change was observed for younger cells. These results may be important for understanding the aging processes, and for cosmetic treatment of aging skin.

Exploring the feasibility of bioaerosol analysis as a novel fingerprinting technique

The purpose of this review is to investigate the feasibility of bioaerosol fingerprinting based on current understanding of cellular debris (with emphasis on human-emitted particulates) in aerosols and arguments regarding sampling, sensitivity, separations, and detection schemes. Target aerosol particles include cellular material and proteins emitted by humans, animals, and plants and can be regarded as information-rich packets that carry biochemical information specific to the living organisms present where the sample is collected. In this work we discuss sampling and analysis techniques that can be integrated with molecular (e.g. protein)-detection procedures to properly assess the aerosolized cellular material of interest. Developing a detailed understanding of bioaerosol molecular profiles in different environments suggests exciting possibilities of bioaerosol analysis with applications ranging from military defense to medical diagnosis and wildlife identification.