The biomechanical properties of the skin

Consensus Agreements on Regenerative Aesthetics: A Focus on Regenerative Biostimulation With Calcium Hydroxylapatite

BACKGROUND

A growing population of patients is seeking treatments that not only affect their overlying features but also restore a more biologically youthful structure and function to the underlying tissue. These strategies are part of what is known as regenerative aesthetics (RA). As an emergent field, clarity regarding the precise definitions and aims of RA and methods to measure the regenerative capacity of RA treatments are lacking.

METHODS

A panel of 6 multidisciplinary experts discussed the foundational aspects of RA. Consensus statements covered aspects of RA including terminology, goals of treatment, treatment strategies, and biological benchmarks indicating regeneration. Consensus on a statement was defined as ≥75% agreement.

RESULTS

Panelists emphasized the importance of natural, youthful tissue architecture and function including cellular and extracellular components. Replacement of a single biological component was not considered sufficient for an aesthetic treatment to be described as regenerative. Rather, the relative amounts, ratios, types, and organization are important to determine regenerative potential. Calcium hydroxylapatite is an example of an aesthetic injectable with evidence of regenerative capacity, as demonstrated by its ability to improve collagen type I/III ratios as well as induce the production of elastin and proteoglycans, which ultimately improve measures of skin quality.

Application of Modified Skin Stretching for Soft Tissue Defect Reconstruction in the Ankle and Foot: A Retrospective Report

OBJECTIVE

The failure rate of foot and ankle soft tissue defect reconstruction with flap is relatively high, often posing a significant burden on patients. The aim of this study is to explore the effectiveness of repeated stretch sutures in repairing skin and soft tissue defects of the ankle and foot.

METHODS

Twenty-three patients with ankle and foot skin and soft tissue defects were retrospectively analyzed between February 2016 and February 2019. Sutures were repeatedly stretched every 3-5 days. Local skin grafting was performed if necessary after wound surfaces disappeared or exposed tendons and bones were covered by soft tissue. Wound healing time, postoperative healing area, Vancouver Scar Assessment Scale, sensation, and function of the new skin were evaluated.

RESULTS

Healing time was 17-35 (24.43 ± 5.29) days. Ten patients wholly healed, and 13 healed by approximately 70.08% ± 6.59%. The Vancouver Scar Assessment Scale average score was 2.83 ± 1.19 points, of which 15 cases were excellent (0-3 points) and 8 cases were good (4-7 points). The sensation and function of the new skin after repair were equivalent to those of normal skin after the last follow-up.

CONCLUSIONS

Applying repeated tension sutures on the skin and soft defects of the ankle and foot reduced the skin graft area and decreased complex high-risk surgical flaps' use and transplantation area.

Chitosan as a tool for tissue engineering and rehabilitation: Recent developments and future perspectives - A review

Chitosan has established itself as a multifunctional and auspicious biomaterial within the domain of tissue engineering, presenting a decade of uninterrupted advancements and novel implementations. This article provides a comprehensive overview of the most recent developments in chitosan-based tissue engineering, focusing on significant progress made in the last ten years. An exploration is conducted of the various techniques utilized in the modification of chitosan and the production of scaffolds, with an analysis of their effects on cellular reactions and tissue regeneration. The investigation focuses on the integration of chitosan with other biomaterials and the addition of bioactive agents to improve their functionalities. Upon careful analysis of the in vitro and in vivo research, it becomes evident that chitosan effectively stimulates cell adhesion, proliferation, and differentiation. Furthermore, we offer valuable perspectives on the dynamic realm of chitosan-based approaches tailored to distinct tissue categories, including nerve, bone, cartilage, and skin. The review concludes with a discussion of prospective developments, with particular attention given to possible directions for additional study, translational implementations, and the utilization of chitosan to tackle existing obstacles in the field of tissue engineering. This extensive examination provides a significant amalgamation of the advancements achieved over the previous decade and directs scholars towards uncharted territories in chitosan-based tissue engineering.

The effect of female breast surface area on skin stiffness and tactile sensitivity at rest and following exercise in the heat

Female development includes significant morphological changes across the breast. Yet, whether differences in breast surface area (BrSA) modify breast skin stiffness and tactile sensitivity at rest and after exercise in the heat remain unclear. We investigated the relationship between BrSA and skin stiffness and tactile sensitivity in 20 young to middle-aged women (27 ± 8 years of age) of varying breast sizes (BrSA range: 147-502 cm2) at rest and after a submaximal run in a warm climatic chamber (32 C ${\mathrm{C}}$  ± 0 . 6 C ; ${\mathrm{0}}{\mathrm{.6C;}}$ 53% ± 1.7% relative humidity). Skin stiffness above and below the nipple and tactile sensitivity from the nipple down were measured. Associations between BrSA and both skin stiffness and tactile sensitivity at rest were determined via correlation analyses. Effects of exercise and test site were assessed by a two-way ANOVA. Skin stiffness was positively correlated with BrSA 3 cm above the areola edge (r = 0.61, P = 0.005) and at the superior areola border (r = 0.54, P = 0.016), but not below the nipple (P > 0.05). The area 3 cm below the areola was also significantly stiffer than all other test sites (P < 0.043). Tactile sensitivity did not vary with BrSA (P > 0.09), but it varied across the breast (i.e., the area 3 cm below the areola was more sensitive than the inferior areola edge; P = 0.018). Skin stiffness and tactile sensitivity across the breast decreased after exercise by ∼37% (P < 0.001) and ∼45% (P = 0.008), respectively. These findings expand our fundamental understanding of the mechanosensory properties of the female breast, and they could help to inform sportswear innovation to better meet the support needs of women of different breast sizes at rest and following exercise.

Pericardium decellularization in a one-day, two-step protocol

Scaffolds used in tissue engineering can be obtained from synthetic or natural materials, always focusing the effort on mimicking the extracellular matrix of human native tissue. In this study, a decellularization process is used to obtain an acellular, biocompatible non-cytotoxic human pericardium graft as a bio-substitute. An enzymatic and hypertonic method was used to decellularize the pericardium. Histological analyses were performed to determine the absence of cells and ensure the integrity of the extracellular matrix (ECM). In order to measure the effect of the decellularization process on the tissue's biological and mechanical properties, residual genetic content and ECM biomolecules (collagen, elastin, and glycosaminoglycan) were quantified and the tissue's tensile strength was tested. Preservation of the biomolecules, a residual genetic content below 50 ng/mg dry tissue, and maintenance of the histological structure provided evidence for the efficacy of the decellularization process, while preserving the ECM. Moreover, the acellular tissue retains its mechanical properties, as shown by the biomechanical tests. Our group has shown that the acellular pericardial matrix obtained through the super-fast decellularization protocol developed recently retains the desired biomechanical and structural properties, suggesting that it is suitable for a broad range of clinical indications.

Serial tissue expansion and excision for reconstruction of giant dorsal congenital melanocytic nevus: A case report

Giant congenital melanocytic nevus often necessitates meticulous planning and multiple treatment stages for complete surgical excision. This report presents a case of giant congenital melanocytic nevus on the back managed through serial tissue expansion and excision. Initially, two expanders were placed at the deep fascia level. Sequential outpatient expansions over 10 weeks were followed by expander removal, partial nevus excision, defect coverage with expanded skin flaps, and simultaneous placement of a new expander. The subsequent single expander expansion over 12 weeks involved a total of 600 mL of saline. After three operations spanning approximately 6 months, 54 cm × 36 cm of giant congenital melanocytic nevus skin, covering 65% of the patient's back, was completely excised. Serial tissue expansion and excision may be an effective surgical approach for managing dorsal giant congenital melanocytic nevus, reducing the need for multiple surgeries and achieving favorable aesthetic outcomes.

Chitosan based extruded nanofibrous bioscaffold for local delivery of mesenchymal stem cells to improve diabetic wound healing

BACKGROUND

Mesenchymal stem cells (MSCs)-based treatment strategy has shown promise in bolstering the healing process of chronic wounds in diabetic patients, who are at risk of amputation and mortality. To overcome the drawbacks of suboptimal cell retention and diminished cell viability at the injury site, a novel nanofibrous biomaterial-based scaffold was developed by using a controlled extrusion of a polymeric solution to deliver the cells (human adipose-derived MSCs (ADMSCs) and placenta-derived MSCs (PLMSCs)) locally to the animal model of diabetic ulcers.

METHODS

The physicochemical and biological properties of the nano-bioscaffold were characterized in terms of microscopic images, FTIR spectroscopy, tensile testing, degradation and swelling tests, contact angle measurements, MTT assay, and cell attachment evaluation. To evaluate the therapeutic efficacy, a study using an excisional wound model was conducted on diabetic rats.

RESULTS

The SEM and AFM images of scaffolds revealed a network of uniform nanofibers with narrow diameters between 100-130 nm and surface roughness less than 5 nm, respectively. ADMSCs and PLMSCs had a typical spindle-shaped or fibroblast-like morphology when attached to the scaffold. Desired characteristics in terms of swelling, hydrophilicity, biodegradation rate, and biocompatibility were achieved with the CS70 formulation. The wound healing process was accelerated according to wound closure rate assay upon treatment with MSCs loaded scaffold resulting in increased re-epithelialization, neovascularization, and less inflammatory reaction. Our findings unequivocally demonstrated that the cell-loaded nano-bioscaffold exhibited more efficacy compared with its acellular counterpart. In summation, our study underscores the potential of this innovative cellular scaffold as a viable solution for enhancing the healing of diabetic ulcers.

CONCLUSION

The utilization of MSCs in a nanofibrous biomaterial framework demonstrates significant promise, providing a novel avenue for advancing wound care and diabetic ulcer management.

Artificial keloid skin models: understanding the pathophysiological mechanisms and application in therapeutic studies

Keloid is a type of scar formed by the overexpression of extracellular matrix substances from fibroblasts following inflammation after trauma. The existing keloid treatment methods include drug injection, surgical intervention, light exposure, cryotherapy, etc. However, these methods have limitations such as recurrence, low treatment efficacy, and side effects. Consequently, studies are being conducted on the treatment of keloids from the perspective of inflammatory mechanisms. In this study, keloid models are created to understand inflammatory mechanisms and explore treatment methods to address them. While previous studies have used animal models with gene mutations, chemical treatments, and keloid tissue transplantation, there are limitations in fully reproducing the characteristics of keloids unique to humans, and ethical issues related to animal welfare pose additional challenges. Consequently, studies are underway to create in vitro artificial skin models to simulate keloid disease and apply them to the development of treatments for skin diseases. In particular, herein, scaffold technologies that implement three-dimensional (3D) full-thickness keloid models are introduced to enhance mechanical properties as well as biological properties of tissues, such as cell proliferation, differentiation, and cellular interactions. It is anticipated that applying these technologies to the production of artificial skin for keloid simulation could contribute to the development of inflammatory keloid treatment techniques in the future.

Effect of negative pressure therapy on the treatment response to scar thickness and viscoelasticity

Patients with scars face a grave threat to their mental and physical health. Negative pressure has been used for scar therapy in medical care and provides a microenvironment conducive to scar healing while stimulating cell regeneration. Negative pressure may disrupt scar tissue regeneration when the pressure is too high or too low, so finding a suitable negative pressure is important. We hypothesized that different negative pressure magnitudes would affect scar tissue properties differently. This research aimed to provide practical recommendations for scar therapy. This study used three negative pressures (-105 mmHg, -125 mmHg, and -145 mmHg) to compare scar material properties. We measured scar tissue thickness and viscoelasticity with a motor-driven ultrasound indentation system. According to the results of this study, scar thickness is most effectively reduced at a negative pressure of -105 mmHg. In comparison, scar viscoelasticity continuously increases at a negative pressure of -125 mmHg. Negative pressure therapy can be recommended to scar care clinics based on the results of this study.

What are optimum cycles for immediate primary closure of large cutaneous defects?

BACKGROUND

In the reconstruction of large complex cutaneous wounds, a myriad of mechanical devices has been designed to facilitate primary wound closure. However, there is a dearth of studies elucidating how best to achieve optimum use and efficiency of skin stretching (SS) when using the device for immediate primary closure of defects.

METHODS

Skin defect wounds (7 × 7 cm) were prepared on the back of three Bama miniature pigs. A total of 15 cycles of SS (cycle loading) were subsequently performed on the skin edges of the wound by EASApprox® SS system. Then, the changes in equidistant points were recorded after each cycle. After the SS test, all wounds were sutured under low tension.

RESULTS

Skin elongation was observed at all equidistant points on the back wounds of three Bama miniature pigs. Up to an additional 1.10 to 3.75 cm of tissue was garnered. The maximum skin elongation was typically achieved within eight cycles of stretching and relaxation. Beyond this range, additional stretching cycles did not result in further skin extension.

CONCLUSION

There may be a close link between mobilization range and the times of acute cyclic stretching (cycle loading) during the process of primary wound closure. However, larger studies are required to further evaluate the accuracy and effectiveness.

Post-Hyaluronic Acid Recurrent Eyelid Edema: Pathophysiologic Mechanisms and a Proposed Treatment Protocol

Background

Hyaluronic acid (HA) filler injections for facial augmentation are commonly administered but can lead to post-hyaluronic acid recurrent eyelid edema (PHAREE). The pathophysiology of this condition has not been fully understood.

Objectives

To report the successful treatment of PHAREE using serial hyaluronidase and fractionated radiofrequency microneedling, with additional carbon dioxide laser skin resurfacing in selected patients.

Methods

Five patients with PHAREE were treated with serial hyaluronidase injections and fractionated radiofrequency microneedling, with 2 patients receiving carbon dioxide laser treatment. The patients were followed up for a minimum of 24 months.

Results

All patients reported a resolution of PHAREE signs/symptoms with no adverse effects or recurrence. One patient demonstrated complete resolution after a single treatment; 4 required a series of treatments.

Conclusions

The proposed treatment protocol may provide advantages over hyaluronidase alone for PHAREE. The impermeable malar septum, vulnerable eyelid lymphatics, and potential immunogenicity of HA fragments likely contribute to PHAREE pathophysiology. Further research on pathophysiologic mechanisms is warranted.

Level of Evidence 4

Layer-by-Layer Analysis of In Vitro Skin Models

In vitro human skin models are evolving into versatile platforms for the study of skin biology and disorders. These models have many potential applications in the fields of drug testing and safety assessment, as well as cosmetic and new treatment development. The development of in vitro skin models that accurately mimic native human skin can reduce reliance on animal models and also allow for more precise, clinically relevant testing. Recent advances in biofabrication techniques and biomaterials have led to the creation of increasingly complex, multilayered skin models that incorporate important functional components of skin, such as the skin barrier, mechanical properties, pigmentation, vasculature, hair follicles, glands, and subcutaneous layer. This improved ability to recapitulate the functional aspects of native skin enhances the ability to model the behavior and response of native human skin, as the complex interplay of cell-to-cell and cell-to-material interactions are incorporated. In this review, we summarize the recent developments in in vitro skin models, with a focus on their applications, limitations, and future directions.

A Skin-Inspired Multifunctional Conductive Hydrogel with High Stretchable, Adhesive, Healable, and Decomposable Properties for Highly Sensitive Dual-Sensing of Temperature and Strain

Developing smart hydrogels with excellent physicochemical properties and multi-sensing capabilities for various simulation of human skin's functions still remains a great challenge. Here, based on simple and convenient one-step covalent cross-linking method enhanced by dynamic RS-Ag interactions, a skin-inspired multifunctional conductive hydrogel with desirable physicochemical properties (including high stretchability, self-adhesion, self-healing, decomposition and removability) is developed for highly sensitive dual-sensing of temperature and strain. Benefiting from the synergistic action of multiple hydrogen bonds, RS-Ag bonds and S-S bonds, the gel exhibited a novel thermosensitive mechanism. The prepared hydrogels exhibited extremely high mechanical properties (maximum tensile strength of 0.35 MPa, elongation at break nearly 1800%, compressive stress over 4.43 MPa), excellent self-healing (96.82% (stress), 88.45% (temperature), 73.89% (mechanical property)), decomposition (the molecular weight after decomposition is below 700) and self-adhesion (enhanced contact with the material interface). In addition, this conductive hydrogel could also simultaneously achieve highly sensitive temperature-sensing (TCR: 10.89) and stress-sensing (GF: 1.469). As a proof-to-concept, the hydrogel displayed superior capability for simulation of human skin to perception of touch, pressure and ambient temperature simultaneously, indicating promising applications in the fields of wearable devices, personal health care, and human-machine interfaces.

Improved tropoelastin synthesis in the skin by codon optimization and nucleotide modification of tropoelastin-encoding synthetic mRNA

Loss of elastin due to aging, disease, or injury can lead to impaired tissue function. In this study, de novo tropoelastin (TE) synthesis is investigated in vitro and in vivo using different TE-encoding synthetic mRNA variants after codon optimization and nucleotide modification. Codon optimization shows a strong effect on protein synthesis without affecting cell viability in vitro, whereas nucleotide modifications strongly modulate translation and reduce cell toxicity. Selected TE mRNA variants (3, 10, and 30 μg) are then analyzed in vivo in porcine skin after intradermal application. Administration of 30 μg of native TE mRNA with a me1 Ψ modification or 10 and 30 μg of unmodified codon-optimized TE mRNA is required to increase TE protein expression in vivo. In contrast, just 3 μg of a codon-optimized TE mRNA variant with the me1 Ψ modification is able to increase protein expression. Furthermore, skin toxicity is investigated in vitro by injecting 30 μg of mRNA of selected TE mRNA variants into a human full-thickness skin model, and no toxic effects are observed. Thereby, for the first time, an increased dermal TE synthesis by exogenous administration of synthetic mRNA is demonstrated in vivo. Codon optimization of a synthetic mRNA can significantly increase protein expression and therapeutic outcome.

Application of Adjustable Skin Stretchers in Repairing Wound-Related Defects

Objective

To explore the application value of adjustable skin stretchers for repairing skin wound defects.

Methods

Twenty patients with skin defects were included in this study. The largest defect was measured to be 45.4 cm × 13.3 cm (length × width) and the smallest one was 4.4 cm × 3.2 cm (length × width). All patients were subjected to adjustable skin stretchers and the short- and long-term clinical efficacy was evaluated.

Results

The wounds of all enrolled patients were healed completely except for one patient with a dorsal foot infection (the patient requested to return to the local county hospital for further treatment), with a total satisfaction of 100%. Postoperative 3-month follow-up showed scar formation, a little local hyperpigmentation, normal skin elasticity, and intact organs of involved cases, thus signifying the significant impact of adjacent joint activities.

Conclusion

Adjustable skin stretchers can accurately control the tension on wound margins, breaking the limitation of previous stretchers to provide objective quantitative indicators for clinical application. These stretchers are characterized by high use-value and are worth promoting.

Assessing the risk of a clinically significant infection from a Microneedle Array Patch (MAP) product

Microneedle Array Patches (MAPs) are an emerging dosage form that creates transient micron-sized disruptions in the outermost physical skin barrier, the stratum corneum, to facilitate delivery of active pharmaceutical ingredients to the underlying tissue. Numerous MAP products are proposed and there is significant clinical potential in priority areas such as vaccination. However, since their inception scientists have hypothesized about the risk of a clinically significant MAP-induced infection. Safety data from two major Phase 3 clinical trials involving hundreds of participants, who in total received tens of thousands of MAP applications, does not identify any clinically significant infections. However, the incumbent data set is not extensive enough to make definitive generalizable conclusions. A comprehensive assessment of the infection risk is therefore advised for MAP products, and this should be informed by clinical and pre-clinical data, theoretical analysis and informed opinions. In this article, a group of key stakeholders identify some of the key product- and patient-specific factors that may contribute to the risk of infection from a MAP product and provide expert opinions in the context of guidance from regulatory authorities. Considerations that are particularly pertinent to the MAP dosage form include the specifications of the finished product (e.g. microbial specification), it's design features, the setting for administration, the skill of the administrator, the anatomical application site, the target population and the clinical context. These factors, and others discussed in this article, provide a platform for the development of MAP risk assessments and a stimulus for early and open dialogue between developers, regulatory authorities and other key stakeholders, to expedite and promote development of safe and effective MAP products.

Study of Elastin, Hydrolyzed Collagen and Collagen-like Products in a Tri-Layered Chitosan Membrane to Test Anti-Aging Skin Properties

The use of animal testing in the cosmetic industry is already prohibited in more than 40 countries, including those of the EU. The pressure for it to be banned worldwide in the future is increasing, so the need for animal alternatives is of great interest today. In addition, using animals and humans in scientific research is ethically reprehensible. This study aimed to prove some of the anti-aging properties of elastin (EL), hydrolyzed collagen (HC), and two vegan collagen-like products (Veg Col) in a tri-layered chitosan membrane that was ionically crosslinked with sodium tripolyphosphate (TPP). In the first approach, as a way of representing different layers of a biological system, such as the epidermis and the two dermis sublayers, EL, HC, or Veg Col were independently introduced into the two inner layers (2L_(i+b)). Their effects were compared with those of their introduction into three layers (3L). Different experiments were performed on the membrane to test its elasticity, hydration, moisture retention, and pore reduction at different concentrations of EL, HC, and Veg Col, and the results were normalized vs. a blank membrane. This new alternative to animal or human testing can be suitable for proving certain efficacy claims for active ingredients or products in the pharmaceutical, nutritional, and cosmetic fields.

Recent advances in in vitro skin-on-a-chip models for drug testing

INTRODUCTION

The skin is an organ that has the largest surface area and provides a barrier against external environment. While providing protection, it also interacts with other organs in the body and has implications in various diseases. Development of physiologically realistic in vitro models of the skin in the context of the whole body is important for studying these diseases, and will be a valuable tool for pharmaceutical, cosmetics, and food industry.

AREA COVERED

This article covers the basic background in skin structure, physiology, as well as drug metabolism in the skin, and dermatological diseases. We summarize various in vitro skin models currently available, and novel in vitro models based on organ-on-a-chip technology. We also explain the concept of multi-organ-on-a-chip and describe recent developments in this field aimed at recapitulating the interaction of the skin with other organs in the body.

EXPERT OPINION

Recent development in the organ-on-a-chip field has enabled the development of in vitro model systems that resemble human skin more closely than conventional models. In near future, we will be seeing various model systems that allow researchers to study complex diseases in a more mechanistic manner, which will help the development of new pharmaceuticals for such diseases.

The Darker the Skin, the Greater the Disparity? Why a Reliance on Visible Injuries Fosters Health, Legal, and Racial Disparities in Domestic Violence Complaints Involving Strangulation

The reliance on external injuries for justice is misguided given that assault injuries may be less visible among victims of color due to increased melanin in the skin. To date, however, less is known whether racial/ethnic disparities extend to officers' identification of signs of nonfatal strangulation (NFS). The current study estimates the extent of NFS indicators identified by officers who completed a standardized strangulation assessment in 133 family violence complaints. Breathing difficulties were the most common symptoms identified by officers (98%), followed by external signs (89%), and symptoms of impeded blood circulation (87%). Compared to cases involving White/Asian survivors, officers were less likely to identify external injuries on Black survivors' neck, chin, and chest/shoulders. While racial/ethnic differences did not emerge for symptoms of disrupted airflow, Hispanic survivors were twice as likely to report losing control of bodily functions. Implications for policy and practice are discussed.

Serial excision surgery for giant dorsal congenital melanocytic nevus: Case report

INTRODUCTION AND IMPORTANCE

Giant congenital melanocytic nevus increases the risk of melanoma and seriously affects the aesthetics and psychology of patients, influencing the personality development of children.

CASE PRESENTATION

A 7-year-old female child presented with a giant congenital melanocytic nevus on the back, which extended from the right anterior abdominal wall to the left flank Taking advantage of the elasticity of children's skin, we performed serial excision and obtained favourable results. The procedure included seven surgeries, and the average interval between the surgeries was 7 months. The nevus was partially resected from the periphery to the centre, and the direction of excision of the nevus depended on the mobilisation of the surrounding normal skin, including from the shoulder downward, lateral to medial, and from the bottom upward. After the seventh surgery at 11 years of age, the nevus was completely removed, and there were no complications.

CLINICAL DISCUSSION

Serial excision is a simple and less invasive surgical technique that can achieve both complete excision and a satisfactory aesthetic result for giant congenital melanocytic nevus. The giant nevus of the back can be removed completely after several procedures due to the very good elasticity of the skin and the great ability of natural expansion of healthy skin under a considerable stretching force in children.

CONCLUSION

Serial excision is an effective method for treating dorsal giant congenital melanocytic nevus in children because of excellent natural skin elasticity.

Eggshell Membrane as a Biomaterial for Bone Regeneration

The physicochemical features of the avian eggshell membrane play an essential role in the process of calcium carbonate deposition during shell mineralization, giving rise to a porous mineralized tissue with remarkable mechanical properties and biological functions. The membrane could be useful by itself or as a bi-dimensional scaffold to build future bone-regenerative materials. This review focuses on the biological, physical, and mechanical properties of the eggshell membrane that could be useful for that purpose. Due to its low cost and wide availability as a waste byproduct of the egg processing industry, repurposing the eggshell membrane for bone bio-material manufacturing fulfills the principles of a circular economy. In addition, eggshell membrane particles have has the potential to be used as bio-ink for 3D printing of tailored implantable scaffolds. Herein, a literature review was conducted to ascertain the degree to which the properties of the eggshell membrane satisfy the requirements for the development of bone scaffolds. In principle, it is biocompatible and non-cytotoxic, and induces proliferation and differentiation of different cell types. Moreover, when implanted in animal models, it elicits a mild inflammatory response and displays characteristics of stability and biodegradability. Furthermore, the eggshell membrane possesses a mechanical viscoelastic behavior comparable to other collagen-based systems. Overall, the biological, physical, and mechanical features of the eggshell membrane, which can be further tuned and improved, make this natural polymer suitable as a basic component for developing new bone graft materials.

Calcium hydroxylapatite microspheres activate fibroblasts through direct contact to stimulate neocollagenesis

BACKGROUND

Calcium hydroxylapatite (CaHA; Radiesse, Merz North America) restores volume and stimulates collagen production. The aim of this research was to explore the role of dilution and diffusion in microsphere distribution and the effect of CaHA concentration on activation of fibroblasts to produce collagen.

METHODS

Ex vivo: Tissue dispersion of CaHA was assessed in abdominal tissue segments obtained from patients which were subsequently injected with CaHA diluted to 1:1 and hyperdiluted to 1:2. In vitro: Collagen type III (COLIII) and type I (COLI) expression of fibroblasts was evaluated after 24 and 72 h of incubation with CaHA concentrations of 1.5 (high dilution), 3.0, and 4.5 mg/ml (low dilution).

RESULTS

Ex vivo: The 1:2 CaHA hyperdilution increased dispersion and decreased concentration of CaHA microspheres compared with the 1:1 dilution. In vitro: CaHA incubation resulted in an increased mean COLIII expression of 123% at 24 h. COLI synthesis did not change after 24 h but increased up to 124% at 72 h. Only fibroblasts in direct contact with CaHA increased COLIII expression. COLIII high-expressing cells were fully activated by CaHA and resulted in the same level of COLIII expression per cell independent of the CaHA dilution.

CONCLUSIONS

A 1:2 hyperdilution of CaHA increased tissue dispersion of CaHA microspheres. Direct contact of CaHA with fibroblasts was a key factor for inducing neocollagenesis. COLIII high-expressing cells were fully activated by CaHA and resulted in the same expression level of COLIII per cell independent of the CaHA amount in each dilution. This indicates that increased collagen expression was due to the activation of more fibroblasts.

Mesoscopic Monitoring of Human Skin Explants Viscoelastic Properties

The investigation of the mechanical properties of skin is of great interest for monitoring physiological and pathological changes in the cutaneous barrier function for dermatological and cosmetic issues. Skin constitutes a complex tissue because of its multi-layered organisation. From a rheological point of view, it can be considered to be a soft tissue with viscoelastic properties. In order to characterise ex vivo mechanical properties of skin on the mesoscopic scale, a biosensor including a thickness shear mode transducer (TSM) in contact with a skin explant was used. A specific experimental set-up was developed to monitor continuously and in real-time human skin explants, including the dermis and the epidermis. These were kept alive for up to 8 days. Skin viscoelastic evolutions can be quantified with a multi-frequency impedance measurement (from 5 MHz to 45 MHz) combined with a dedicated fractional calculus model. Two relevant parameters for the non-destructive mesoscopic characterisation of skin explants were extracted: the structural parameter αapp and the apparent viscosity ηapp. In this study, the validity of the biosensor, including repeatability and viability, was controlled. A typical signature of the viscoelastic evolutions of the different cutaneous layers was identified. Finally, monitoring was carried out on stripped explants mimicking a weakened barrier function.

Perirenal adipose tissues as a human elastin source, and optimize the extraction process

Elastin is very rarely repaired extracellular matrix (ECM) in physiological condition. The commercial human elastin for exogenous medical treatment is very expensive, and has a potential for disease transmission. Animal-origin elastin is relatively low price, but has concerns for xenogeneic immune responses. Considering cost and safety, we focused on the perirenal adipose tissue, donated from healthy young people via donor nephrectomy. Until now, all of the perirenal adipose tissues are discarded as a medical waste after kidney transplantation. In the present study, we applied perirenal adipose tissues as the source of human elastin, and optimized the extraction process to get high purified and quantified elastin. Through pre-processing step, the delipidated and decellularized ECM was prepared. Next, with four different elastin extraction process (acidic solvents, neutral salt, organic solvents or hot alkali method), elastin was extracted, and the concentration of amino acid between each product was compared, and bright-field/electron microscopy, Fourier transform infrared (FT-IR) spectroscopy and cytotoxicity analysis were also performed. As controls, bovine neck ligament-derived and human skin-derived elastin were used. Among the elastin extraction methods, the hot alkali insoluble product showed (1) relatively high positive area of Verhoeff's and low Masson's trichrome stain, (2) 64.24% purity, 159.29 mg/g quantity, and ∼6.37% yield in amino acid analysis, (3) β-sheet second structure, and (4) thin fiber composed mesh-like sheet structure in SEM image. These values were higher than those of the commercial human skin elastin. When comparing hydrolyzed forms, α-elastin from hot alkali insoluble product showed enhanced cell proliferation and maintained cell properties compared to the κ-elastin. Therefore, we confirmed that the perirenal adipose tissue is an ideal source of human elastin with safety assurance, and the hot alkali process combined with pre-process seems to be the optimal method for elastin extraction with high purity and quantity.

Efficacy and safety of external tissue expansion technique in the treatment of soft tissue defects: a systematic review and meta-analysis of outcomes and complication rates

Background

Currently, various external tissue expansion devices are becoming widely used. Considering the scarcity of relevant application standards, this systematic review was performed to explore the effectiveness and safety of external tissue expansion techniques for the reconstruction of soft tissue defects.

Method

A systematic review and meta-analysis on the efficacy and safety of external tissue expansion technique was conducted. A comprehensive search was performed in the following electronic databases: PubMed/Medline, Embase, Cochrane Library (Wiley Online Library), and Web of Science. Studies reporting patients with soft tissue defects under the treatment of external tissue expansion technique were included.

Results

A total of 66 studies with 22 different types of external tissue expansion devices met the inclusion criteria. We performed a descriptive analysis of different kinds of devices. A single-arm meta-analysis was performed to evaluate the efficacy and safety of the external tissue expansion technique for different aetiologies. The pooled mean wound healing time among patients with defects after fasciotomy was 10.548 days [95% confidence interval (CI) = 5.796-15.299]. The pooled median wound healing times of patients with defects after excisional surgery, trauma, chronic ulcers and abdominal defects were 11.218 days (95% CI = 6.183-16.253), 11.561 days (95% CI = 7.062-16.060), 15.956 days (95% CI = 11.916-19.996) and 12.853 days (95% CI=9.444-16.227), respectively. The pooled wound healing rates of patients with defects after fasciotomy, excisional surgery, trauma, chronic ulcers and abdominal defects were 93.8% (95% CI=87.1-98.2%), 97.2% (95%CI=92.2-99.7%), 97.0% (95%CI=91.2-99.8%), 99.5% (95%CI=97.6-100%), and 96.8% (95%CI=79.2-100%), respectively. We performed a subgroup analysis in patients with diabetic ulcers and open abdominal wounds. The pooled median wound healing time of patients with diabetic ulcers was 11.730 days (95% CI = 10.334-13.125). The pooled median wound healing time of patients with open abdomen defects was 48.810 days (95% CI = 35.557-62.063) and the pooled successful healing rate was 68.8% (95% CI = 45.9-88.1%). A total of 1686 patients were included, 265 (15.7%) of whom experienced complications. The most common complication was dehiscence (n = 53, 3.14%).

Conclusions

Our systematic review is the first to demonstrate the efficacy and safety of external tissue expansion in the management of soft tissue defects. However, we must interpret the meta-analysis results with caution considering the limitations of this review. Large-scale randomized controlled trials and long-term follow-up studies are still needed to confirm the effectiveness and evaluate the quality of healing.

Adaptive multi-degree-of-freedom in situ bioprinting robot for hair-follicle-inclusive skin repair: A preliminary study conducted in mice

Skin acts as an essential barrier, protecting organisms from their environment. For skin trauma caused by accidental injuries, rapid healing, personalization, and functionality are vital requirements in clinical, which are the bottlenecks hindering the translation of skin repair from benchside to bedside. Herein, we described a novel design and a proof-of-concept demonstration of an adaptive bioprinting robot to proceed rapid in situ bioprinting on a full-thickness excisional wound in mice. The three-dimensional (3D) scanning and closed-loop visual system integrated in the robot and the multi-degree-of-freedom mechanism provide immediate, precise, and complete wound coverage through stereotactic bioprinting, which hits the key requirements of rapid-healing and personalization in skin repair. Combined with the robot, epidermal stem cells and skin-derived precursors isolated from neonatal mice mixed with Matrigel were directly printed into the injured area to replicate the skin structure. Excisional wounds after bioprinting showed complete wound healing and functional skin tissue regeneration that closely resembling native skin, including epidermis, dermis, blood vessels, hair follicles and sebaceous glands etc. This study provides an effective strategy for skin repair through the combination of the novel robot and a bioactive bioink, and has a promising clinical translational potential for further applications.

Staged Excision Technique to Reduce Scar Length

Patients and surgeons are often disappointed with the scar length after conventional staged excision of large disfiguring skin lesions. We have developed an alternative approach to facilitate scar length reduction. We aimed to report the efficacy of our staged excision method, which includes a hexagonal-pattern excision, wide undermining, and purse-string suture. Sixty-five patients, each with one lesion, were included in the current study. The lesion length and width were recorded, and the scar area was calculated at each stage. The final scar length after performing the altered staged excision method was compared with that obtained after the conventional staged excision method, which was calculated using a theoretical scar model. Patient satisfaction was also evaluated. The mean longest axis length was 9.41 ± 3.83 cm preoperatively, 9.50 ± 3.92 cm after the first stage postoperatively, and 10.19 ± 3.98 cm after the final stage. The mean lesion width was 6.50 ± 3.48 cm preoperatively, 3.60 ± 1.77 cm after the first stage postoperatively, and 0.42 ± 0.31 cm after the final stage. The final scar length obtained using the altered procedure was much shorter than what would be obtained using conventional staged excision. The patient satisfaction score was 8.8 ± 1.1 out of a possible 10.0 rating. Staged excision with a hexagonal-pattern excision, wide undermining, and purse-string closure may improve aesthetic results.

Inhibition of Collagenase Q1 of Bacillus cereus as a Novel Antivirulence Strategy for the Treatment of Skin-Wound Infections

Despite the progress in surgical techniques and antibiotic prophylaxis, opportunistic wound infections with Bacillus cereus remain a public health problem. Secreted toxins are one of the main factors contributing to B. cereus pathogenicity. A promising strategy to treat such infections is to target these toxins and not the bacteria. Although the exoenzymes produced by B. cereus are thoroughly investigated, little is known about the role of B. cereus collagenases in wound infections. In this report, the collagenolytic activity of secreted collagenases (Col) is characterized in the B. cereus culture supernatant (csn) and its isolated recombinantly produced ColQ1 is characterized. The data reveals that ColQ1 causes damage on dermal collagen (COL). This results in gaps in the tissue, which might facilitate the spread of bacteria. The importance of B. cereus collagenases is also demonstrated in disease promotion using two inhibitors. Compound 2 shows high efficacy in peptidolytic, gelatinolytic, and COL degradation assays. It also preserves the fibrillar COLs in skin tissue challenged with ColQ1, as well as the viability of skin cells treated with B. cereus csn. A Galleria mellonella model highlights the significance of collagenase inhibition in vivo.

Clinical Relevance of Elastin in the Structure and Function of Skin

Elastin is the main component of elastic fibers, which provide stretch, recoil, and elasticity to the skin. Normal levels of elastic fiber production, organization, and integration with other cutaneous extracellular matrix proteins, proteoglycans, and glycosaminoglycans are integral to maintaining healthy skin structure, function, and youthful appearance. Although elastin has very low turnover, its production decreases after individuals reach maturity and it is susceptible to damage from many factors. With advancing age and exposure to environmental insults, elastic fibers degrade. This degradation contributes to the loss of the skin's structural integrity; combined with subcutaneous fat loss, this results in looser, sagging skin, causing undesirable changes in appearance. The most dramatic changes occur in chronically sun-exposed skin, which displays sharply altered amounts and arrangements of cutaneous elastic fibers, decreased fine elastic fibers in the superficial dermis connecting to the epidermis, and replacement of the normal collagen-rich superficial dermis with abnormal clumps of solar elastosis material. Disruption of elastic fiber networks also leads to undesirable characteristics in wound healing, and the worsening structure and appearance of scars and stretch marks. Identifying ways to replenish elastin and elastic fibers should improve the skin's appearance, texture, resiliency, and wound-healing capabilities. However, few therapies are capable of repairing elastic fibers or substantially reorganizing the elastin/microfibril network. This review describes the clinical relevance of elastin in the context of the structure and function of healthy and aging skin, wound healing, and scars and introduces new approaches being developed to target elastin production and elastic fiber formation.

Closure of Complex Wounds by a Simple Skin Stretching System Associated With Vacuum Sealing Drainage-Clinical Outcome of 34 Patients

Management of complex wounds with large skin defects presents a real challenge for orthopedic or reconstructive surgeons. We developed a simple skin stretching system associated with vacuum sealing drainage to examine the efficiency and complication. A total of 34 patients with different types of complex wounds were retrospectively included from January 2015 to March 2021. All patients in the study were underwent the treatment by 2 stages. The method was used to the wounds from 4.71 to 169.65 cm² with a median defect size of 25.13 cm². The median time for wound closure was 11.5 days (range: 5-32 days), although the median absolute reduction was 2.08 cm²/day (range: 0.15-25.66 cm²/day). Depending on the site of the wounds, the cause of the wound, and the rate of max-width/max-length (W/L), these complex wounds could be separately divided into several groups. There were statistically significant differences in the median value of the above variables (P < .05 Kruskal-Wallis test). The results showed that different anatomical sites had different viscoelastic properties, the complex wounds caused by trauma were easier to close than caused by diabetic foot and the complex wounds in group A (W/L ＞ 0.5) were more difficult to close than in group B (W/L ≤ 0.5). No major complications were encountered in this study. In summary, the results of our study showed that the simple skin stretching system associated with vacuum sealing drainage was a safe approach for closure of complex wounds. Nevertheless, more attention should be paid to the viscoelasticity of the wounds to ensure closure and avoid undue complications when applying the method.

Skin Quality - A Holistic 360° View: Consensus Results

Introduction

Skin quality is an important component of human attractiveness. To date, there are no standardized criteria for good skin quality. To establish a consensus for good skin quality parameters and measurement and treatment options, a virtual skin quality advisory board consisting of a global panel of highly experienced aesthetic dermatologists/aesthetic physicians was convened.

Methods

A total of 10 dermatologists/aesthetic physicians served on the advisory board. A modified version of the Delphi method was used to arrive at consensus. Members accessed an online platform to review statements on skin quality criteria from their peers, including treatment and measurement options, and voted to indicate whether they agreed or disagreed. Statements that did not have agreement were modified and the members voted again. Consensus was defined as: strong consensus = greater than 95% agreement; consensus = 75% to 95% agreement; majority consent = 50% to 75% agreement; no consensus = less than 50% agreement.

Results

There was strong consensus that good skin quality is defined as healthy, youthful in appearance (appearing younger than a person's chronological age), undamaged skin and that skin quality can be described across all ethnicities by four emergent perceptual categories (EPCs): skin tone evenness, skin surface evenness, skin firmness, and skin glow. The EPCs can be affected by multiple tissue layers (ie, skin surface quality can stem from and be impacted by deep structures or tissues). This means that topical approaches may not be sufficient. Instead, improving skin quality EPCs can require a multilayer treatment strategy.

Conclusion

This global advisory board established strong consensus that skin quality can be described by four EPCs, which can help clinicians determine the appropriate treatment option(s) and the tissue or skin layer(s) to address. Skin quality is important to human health and wellbeing and patients' perception for the need for aesthetic treatment.

Fast protocol for the processing of split-thickness skin into decellularized human dermal matrix

BACKGROUND

Dermal scaffolds for tissue regeneration are nowadays an effective alternative in not only wound healing surgeries but also breast reconstruction, abdominal wall reconstruction and tendon reinforcement. The present study describes the development of a decellularization protocol applied to human split-thickness skin from cadaveric donors to obtain dermal matrix using an easy and quick procedure.

METHODS

Complete split-thickness donor was decellularized through the combination of hypertonic and enzymatic methods. To evaluate the absence of epidermis and dermal cells, and ensure the integrity of the extracellular matrix (ECM) structure, histological analysis was performed. Residual genetic content and ECM biomolecules (collagen, elastin, and glycosaminoglycan) were quantified and tensile strength was tested to measure the effect of the decellularization technique on the mechanical properties of the tissue.

RESULTS

Biomolecules quantification, residual genetic content (below 50 ng/mg dry tissue) and histological structure assessment showed the efficacy of the decellularization process and the preservation of the ECM. The biomechanical tests confirmed the preservation of native properties in the acellular tissue.

CONCLUSIONS

The acellular dermal matrix obtained from whole split-thickness skin donor with the newly developed decellualrization protocol, maintains the desired biomechanical and structural properties and represents a viable treatment option for patients.

A role for estrogen in skin ageing and dermal biomechanics

The skin is the body's primary defence against the external environment, preventing infection and desiccation. Therefore, alterations to skin homeostasis, for example with skin ageing, increase susceptibility to skin disease and injury. Skin biological ageing is uniquely influenced by a combination of intrinsic and extrinsic (primarily photoageing) factors, with differential effects on skin structure and function. Interestingly, skin architecture rapidly changes following the menopause, as a direct result of reduced circulating 17β-estradiol. The traditional clinical benefit of estrogens are supported by recent experimental data, where 17β-estradiol supplementation prevents age-related decline in the skin's structural and mechanical properties. However, the off-target effects of 17β-estradiol continue to challenge therapeutic application. Here we discuss how ageing alters the physiological and structural properties of the dermal extracellular matrix, and explore how estrogen receptor-targeted therapies may restore the mechanical defects associated with skin ageing.

Three-Dimensional Quantification of Collagen Microstructure During Tensile Mechanical Loading of Skin

Skin is a heterogeneous tissue that can undergo substantial structural and functional changes with age, disease, or following injury. Understanding how these changes impact the mechanical properties of skin requires three-dimensional (3D) quantification of the tissue microstructure and its kinematics. The goal of this study was to quantify these structure-function relationships via second harmonic generation (SHG) microscopy of mouse skin under tensile mechanical loading. Tissue deformation at the macro- and micro-scale was quantified, and a substantial decrease in tissue volume and a large Poisson’s ratio was detected with stretch, indicating the skin differs substantially from the hyperelastic material models historically used to explain its behavior. Additionally, the relative amount of measured strain did not significantly change between length scales, suggesting that the collagen fiber network is uniformly distributing applied strains. Analysis of undeformed collagen fiber organization and volume fraction revealed a length scale dependency for both metrics. 3D analysis of SHG volumes also showed that collagen fiber alignment increased in the direction of stretch, but fiber volume fraction did not change. Interestingly, 3D fiber kinematics was found to have a non-affine relationship with tissue deformation, and an affine transformation of the micro-scale fiber network overestimates the amount of fiber realignment. This result, along with the other outcomes, highlights the importance of accurate, scale-matched 3D experimental measurements when developing multi-scale models of skin mechanical function.

Engineering Microneedle Patches for Improved Penetration: Analysis, Skin Models and Factors Affecting Needle Insertion

Transdermal microneedle (MN) patches are a promising tool used to transport a wide variety of active compounds into the skin. To serve as a substitute for common hypodermic needles, MNs must pierce the human stratum corneum (~ 10 to 20 µm), without rupturing or bending during penetration. This ensures that the cargo is released at the predetermined place and time. Therefore, the ability of MN patches to sufficiently pierce the skin is a crucial requirement. In the current review, the pain signal and its management during application of MNs and typical hypodermic needles are presented and compared. This is followed by a discussion on mechanical analysis and skin models used for insertion tests before application to clinical practice. Factors that affect insertion (e.g., geometry, material composition and cross-linking of MNs), along with recent advancements in developed strategies (e.g., insertion responsive patches and 3D printed biomimetic MNs using two-photon lithography) to improve the skin penetration are highlighted to provide a backdrop for future research.

New prospects in skin regeneration and repair using nanophased hydroxyapatite embedded in collagen nanofibers

This study reflects an exploitation of a composite matrix produced by electrospinning of collagen and electrospraying of nanophased hydroxyapatite (nanoHA), for skin regeneration applications. The main goal was to evaluate the effect of nanoHA, as source of localized calcium delivery, on human dermal fibroblasts, keratinocytes, and human mesenchymal stem cells (hMSCs) growth, proliferation, differentiation, and extracellular matrix production. This study revealed that calcium ions provided by nanoHA significantly enhanced cellular growth and proliferation rates and prevented adhesion of pathogenic bacteria strains typically found in human skin flora. Moreover, hMSCs were able to differentiate in both osteogenic and adipogenic lineages. Rat subcutaneous implantation of the membranes also revealed that no adverse reaction occurred. Therefore, the mechanically fit composite membrane presents a great potential to be used either as cell transplantation scaffold for skin wound regeneration or as wound dressing material in plastic surgery, burns treatment or skin diseases.

Iatrogenic Compartment Syndrome After Delayed Primary Closure of the Tibial Fracture-Related Leg Fasciotomy Wound: A Case Report

CASE

Compartment syndrome can occur after tibial fracture and requires prompt diagnosis and immediate fasciotomy. Because of post-traumatic swelling, delayed primary wound closure can be difficult requiring significant tension on the skin. Closing the skin in this setting theoretically puts the patient at risk of elevated compartment pressures, although compartment syndrome has never been reported in these circumstances. We describe a case of compartment syndrome that developed after delayed primary skin closure of a single incision 4-compartment fasciotomy wound after tibial fracture.

CONCLUSION

This is the first published description of compartment syndrome after delayed primary closure of a leg fasciotomy wound.

Seasonal variations in the skin parameters of Caucasian women from Central Europe

BACKGROUND

The human skin is greatly affected by external factors such as UV radiation (UVR), ambient temperature (T), and air humidity. These factors oscillate during the year giving rise to the seasonal variations in the skin properties. The aim of this study was to evaluate the effect of seasons, environmental T, relative and absolute humidity on the skin parameters of Caucasian women, perform a literature review and discuss the possible factors lying behind the found changes.

MATERIALS AND METHODS

We measured stratum corneum (SC) hydration, transepidermal water loss (TEWL), sebum level, erythema index, and elasticity parameters R2 and R7 on the forehead and the cheek of Caucasian women from the Czech Republic throughout the year. We also performed a non-systematic literature review focused on the seasonal variations in these skin parameters.

RESULTS

We confirmed a well-documented low SC hydration and sebum production in winter. In spring, we found the lowest TEWL (on the forehead) and the highest SC hydration but also the highest erythema index and the lowest elasticity presumably indicating skin photodamage. For most of the skin parameters, the seasonal variations probably arise due to a complex action of different factors as we extensively discussed.

CONCLUSION

The data about the seasonal variations in the skin parameters are still highly inconsistent and further studies are needed for better understanding of the normal skin changes throughout the year.

Do static and dynamic activities induce potentially damaging breast skin strain?

Background/Aim

This study aimed to quantify breast skin strain and strain rate and the effect of support garments at reducing strain and to determine characteristics that correlate with strain during static and dynamic activity.

Methods

39 women (UK size 32C to 36G) had electromagnetic sensors applied to their breast skin. Sensor coordinates were recorded while standing, walking, running, in no, low and high breast support conditions, plus bare-breasted in the estimated neutral position to calculate strain. Relative breast coordinates and 35 inter-sensor distances identified peak breast skin strain (%) and strain rate (%·s^-1), which were then correlated with nipple kinematics, breast pain and participant characteristics.

Results

Mean peak breast skin strain was generally <60% during standing, walking and running; however, some individuals exhibited 93% strain in bare-breasted running. Compared with low support, high support did not further reduce strain during standing and walking. Peak breast skin strain/strain rate location was longitudinal, in lateral and medial breast regions and displayed strong correlations with breast volume, body mass index and bust circumference.

Conclusion

Static and dynamic activity did not result in excessive breast skin strain, suggesting low risk of skin damage. However, during running, some individuals experienced excessive skin strains (up to 93%) and strain rates (up to 1258%·s^-1). Breast skin strain/strain rate location suggests lift is required in the lateral and medial bra cup to reduce strain, particularly in larger breast volumes due to increased skin strain risk.

Heterogeneity of fibrillin-rich microfibrils extracted from human skin of diverse ethnicity

The dermal elastic fibre network is the primary effector of skin elasticity, enabling it to extend and recoil many times over the lifetime of the individual. Fibrillin-rich microfibrils (FRMs) constitute integral components of the elastic fibre network, with their distribution showing differential deposition in the papillary dermis across individuals of diverse skin ethnicity. Despite these differential findings in histological presentation, it is not known if skin ethnicity influences FRM ultrastructure. FRMs are evolutionarily highly conserved from jellyfish to man and, regardless of tissue type or species, isolated FRMs have a characteristic 'beads-on-a-string' ultrastructural appearance, with an average inter-bead distance (or periodicity) of 56 nm. Here, skin biopsies were obtained from the photoprotected buttock of healthy volunteers (18-27 years; African: n = 5; European: n = 5), and FRMs were isolated from the superficial papillary dermis and deeper reticular dermis and imaged by atomic force microscopy. In the reticular dermis, there was no significant difference in FRM ultrastructure between European and African participants. In contrast, in the more superficial papillary dermis, inter-bead periodicity was significantly larger for FRMs extracted from European participants than from African participants by 2.20 nm (p < .001). We next assessed whether these differences in FRM ultrastructure were present during early postnatal development by characterizing FRMs from full-thickness neonatal foreskin. Analysis of FRM periodicity identified no significant difference between neonatal cohorts (p = .865). These data suggest that at birth, FRMs are developmentally invariant. However, in adults of diverse skin ethnicity, there is a deviation in ultrastructure for the papillary dermal FRMs that may be acquired during the passage of time from child to adulthood. Understanding the mechanism by which this difference in papillary dermal FRMs arises warrants further study.

Role of scattering and birefringence in phase retardation revealed by locus of Stokes vector on Poincaré sphere

SIGNIFICANCE

Biological tissues are typically characterized by high anisotropic scattering and may also exhibit linear form birefringence. Both scattering and birefringence bias the phase shift between transverse electric field components of polarized light. These phase alterations are associated with particular structural malformations in the tissue. In fact, the majority of polarization-based techniques are unable to distinguish the nature of the phase shift induced by birefringence or scattering of light.

AIM

We explore the distinct contributions of scattering and birefringence in the phase retardation of circularly polarized light propagated in turbid tissue-like scattering medium.

APPROACH

The circularly polarized light in frame of Stokes polarimetry approach is used for the screening of biotissue phantoms and chicken skin samples. The change of optical properties in chicken skin is accomplished by optical clearing, which reduces scattering, and mechanical stretch, which induces birefringence. The change of optical properties of skin tissue is confirmed by spectrophotometric measurements and second-harmonic generation imaging.

RESULTS

The contributions of scattering and birefringence in the phase retardation of circularly polarized light propagated in biological tissues are distinguished by the locus of the Stokes vector mapped on the Poincaré sphere. The phase retardation of circularly polarized light due to scattering alterations is assessed. The value of birefringence in chicken skin is estimated as 0.3  ×  10^-3, which agrees with alternative studies. The change of birefringence of skin tissue due to mechanical stretch in the order of 10^-6 is detected.

CONCLUSIONS

While the polarimetric parameters on their own do not allow distinguishing the contributions of scattering and birefringence, the resultant Stokes vector trajectory on the Poincaré sphere reveals the role of scattering and birefringence in the total phase retardation. The described approach, applied independently or in combination with Mueller polarimetry, can be beneficial for the advanced characterization of various types of malformations within biological tissues.

Remodelling of fibrillin-rich microfibrils by solar-simulated radiation: impact of skin ethnicity

Cutaneous fibrillin-rich microfibrils (FRMs) should be considered as two distinct populations that differentially accrue damage in response to SSR. Furthermore, FRMs derived from black African skin show greater change following UVR challenge.

Optimising Wound Closure Following a Fasciotomy: A narrative review

Compartment syndrome is a surgical emergency that could be resolved by a fasciotomy. However, performing substantial skin incisions may lead to life-threatening complications. This narrative review aimed to present the available methods of wound closure and preferential factors for using each technique. Viable and non-infected wounds were most often treated by gradual approximation techniques, such as the simple or modified shoelace technique, the prepositioned intracutaneous suture or several commercially-available mechanical devices. In addition, applying negative pressure therapy was found to be feasible, particularly when combined with approximation techniques. Skin grafting was reserved for severely-dehiscent wounds while other non-invasive approaches were considered for other subsets of patients with inadvisable surgical interventions. Treatment decision should be made in view of the patient’s condition, ease of application, availability of resources, cost of treatment and aesthetic outcomes.

Exploring the degrees of distortion in simulated human bite marks

The properties of the skin and the posture of the body during photographic recording are factors that cause distortion in the bite mark injury. This study aimed to explore the degree of distortion between a ‘touch mark’ (method 1) and a ‘bite mark’ (method 2) on the left upper arm at three different positions (arm relaxed; arm flexed in two different positions). A pair of dental casts with biting edges coated in ink was used to create a mark in 30 subjects (6 ♂, 24 ♀) aged 20–50 years old. Photographs were taken using a Nikon DX digital camera (D5000). The mesiodistal widths and angle of rotations of both upper right central incisor and lower right central incisor and the inter-canine distances were analysed and compared with the true measurements using Adobe Photoshop CC 2017. Statistical analysis was carried out using SPSS Statistics 22 applying a 2 (mark type) × 3 (position) repeated measures ANOVA. For all measures studied, there was a statistically significant difference between mark types and positions. In the case of bite marks, a great degree of distortion was detected, and this increased further when changing the position of the arm. The findings demonstrated that skin properties and posture influence distortion. This could lead to inaccurate measurements and misleading pattern interpretation of bite mark injuries.