Quantification of thermal damage in skin tissue

Skin thermal damage or skin burns are the most commonly encountered type of trauma in civilian and military communities. Besides, advances in laser, microwave and similar technologies have led to recent developments of thermal treatments for disease and damage involving skin tissue, where the objective is to induce thermal damage precisely within targeted tissue structures but without affecting the surrounding, healthy tissue. Further, extended pain sensation induced by thermal damage has also brought great problem for burn patients. Thus, it is of great importance to quantify the thermal damage in skin tissue. In this paper, the available models and experimental methods for quantification of thermal damage in skin tissue are discussed.

Biothermomechanical behavior of skin tissue

Advances in laser, microwave and similar technologies have led to recent developments of thermal treatments involving skin tissue. The effectiveness of these treatments is governed by the coupled thermal, mechanical, biological and neural responses of the affected tissue： a favorable interaction results in a procedure with relatively little pain and no lasting side effects. Currently, even though each behavioral facet is to a certain extent established and understood, none exists to date in the interdisciplinary area. A highly interdisciplinary approach is required for studying the biothermomechanical behavior of skin, involving bioheat transfer, biomechanics and physiology. A comprehensive literature review pertinent to the subject is presented in this paper, covering four subject areas： （a） skin structure, （b） skin bioheat transfer and thermal damage, （c） skin biomechanics, and （d） skin biothermomechanics. The major problems, issues, and topics for further studies are also outlined. This review finds that significant advances in each of these aspects have been achieved in recent years. Although focus is placed upon the biothermomechanical behavior of skin tissue, the fundamental concepts and methodologies reviewed in this paper may also be applicable for studying other soft tissues.

A Constitutive Model for Softening Behaviors of Skin Tissue

Skin tissue is a kind of complex biological material abundant with fibers.A new constitutive model,relating macroscopic responses with microstructural fiber configuration alteration,is developed to investigate the stress softening behaviors of skin tissue observed during cyclic loading-unloading tests.Two influential factors are introduced to describe the impact of fiber configuration change and stretch-induced damage.The present model achieves good agreement between predicted stress distribution of human skin and corresponding ex vivo experimental data obtained from the literature,affirming its capability to effectively capture the characteristic softening behaviors of human skin under cyclic loading conditions.

Skin and Soft Tissue Infections in the Surgical Area at the Kara Teaching Hospital

Objective: To report the management of skin and soft tissue infections in the surgical area of Kara University Hospital in Togo. Material and Methods: This study was conducted retrospectively from January 1, 2021, to December 31, 2022, in the general surgery and orthopedic trauma departments. The study focused on soft tissue infections of the pelvic and thoracic limbs and analyzed epidemiological, clinical, paraclinical, therapeutic, and evolutionary data. Results: We registered 165 patients, comprising 109 men and 56 women.The sex ratio (F/H) were 0.51. The mean age was 45 years with extremes ranging from 23 to 90 years. Farmers (64.8%) followed by housewives (34.0%) were the social strata most affected. The consultation period varied between 1 and 90 days. The pathologies found were necrotizing fasciitis (53.3%), erysipelas (18.2%), infected limb wounds (12.1%), pyomyositis (9.7%), and necrotizing dermo-hypodermitis (1.8%). The main procedures performed were necrosectomy and grafting (62.9%), sample necrosectomy (18.8%), drainage (9.7%), and pelvic limb amputation (1.2%). Follow-up was favorable in 86.7% of cases. The study noted a death rate of 13.3% due to septic shock secondary to a delay in consultation. Conclusion: Skin and soft tissue infections were a common reason for surgical hospitalization at Kara University Hospital, with a high mortality rate due to delayed consultations.

Skin tissue engineering advances in severe burns:review and therapeutic applications

Current advances in basic stem cell research and tissue engineering augur well for the development of improved cultured skin tissue substitutes:a class of products that is still fraught with limitations for clinical use.Although the ability to grow autologous keratinocytes in-vitro from a small skin biopsy into sheets of stratified epithelium(within 3 to 4 weeks)helped alleviate the problem of insufficient donor site for extensive burn,many burn units still have to grapple with insufficient skin allografts which are used as intermediate wound coverage after burn excision.Alternatives offered by tissue-engineered skin dermal replacements to meet emergency demand have been used fairly successfully.Despite the availability of these commercial products,they all suffer from the same problems of extremely high cost,sub-normal skin microstructure and inconsistent engraftment,especially in full thickness burns.Clinical practice for severe burn treatment has since evolved to incorporate these tissue-engineered skin substitutes,usually as an adjunct to speed up epithelization for wound closure and/or to improve quality of life by improving the functional and cosmetic results long-term.This review seeks to bring the reader through the beginnings of skin tissue engineering,the utilization of some of the key products developed for the treatment of severe burns and the hope of harnessing stem cells to improve on current practice.

Recent advancements in applications of chitosan-based biomaterials for skin tissue engineering

The use of polymer based composites in the treatment of skin tissue damages,has got huge attention in clinical demand,which enforced the scientists to improve the methods of biopolymer designing in order to obtain highly efficient system for complete restoration of damaged tissue.In last few decades,chitosan-based biomaterials have major applications in skin tissue engineering due to its biocompatible,hemostatic,antimicrobial and biodegradable capabilities.This article overviewed the promising biological properties of chitosan and further discussed the various preparation methods involved in chitosan-based biomaterials.In addition,this review also gave a comprehensive discussion of different forms of chitosan-based biomaterials including membrane,sponge,nanofiber and hydrogel that were extensively employed in skin tissue engineering.This review will help to form a base for the advanced applications of chitosan-based biomaterials in treatment of skin tissue damages.

Reversibly immortalized keratinocytes(iKera)facilitate re-epithelization and skin wound healing:Potential applications in cell-based skin tissue engineering

Skin injury is repaired through a multi-phase wound healing process of tissue granulation and re-epithelialization.Any failure in the healing process may lead to chronic non-healing wounds or abnormal scar formation.Although significant progress has been made in developing novel scaffolds and/or cell-based therapeutic strategies to promote wound healing,effective management of large chronic skin wounds remains a clinical challenge.Keratinocytes are critical to re-epithelialization and wound healing.Here,we investigated whether exogenous keratinocytes,in combination with a citrate-based scaffold,enhanced skin wound healing.We first established reversibly immortalized mouse keratinocytes(iKera),and confirmed that the iKera cells expressed keratinocyte markers,and were responsive to UVB treatment,and were non-tumorigenic.In a proof-of-principle experiment,we demonstrated that iKera cells embedded in citrate-based scaffold PPCN provided more effective re-epithelialization and cutaneous wound healing than that of either PPCN or iKera cells alone,in a mouse skin wound model.Thus,these results demonstrate that iKera cells may serve as a valuable skin epithelial source when,combining with appropriate biocompatible scaffolds,to investigate cutaneous wound healing and skin regeneration.

A Two-Dimensional Mathematical Model to Analyze Thermal Variations in Skin and Subcutaneous Tissue Region of Human Limb during Surgical Wound Healing

During wound healing, the metabolic activity associated with each phase must occur in the proper sequence, at a specific time, and continue for a specific duration at an optimal intensity. Any disturbance in appropriate thermal environment may complicate the wound healing process and may give rise to wound infection. In the presented paper a transient state two-dimensional mathematical model has been developed to analyse thermal variations in skin and subcutaneous tissue (SST) region of human limb. Due to circular shape of human limb, model has been developed in polar coordinates. The domain of the study consists of two types of tissues: abnormal tissues and normal tissues. The post surgery peripheral tissue of human limb during healing time is considered as abnormal tissues. The effect of variable density of blood vessels in dermal layer of both tissues on the physical and physiological parameters is incorporated in the model. The effect of healing on physiological parameters of abnormal tissue is incorporated by considering the physiological parameters to be function of time “t”. The effect of different climatic conditions is considered in the model. Taking into account the variable core temperature due to anatomy of arteries and variable physiological parameters in dermal layer of peripheral region, the well known Pennes’ bio heat equation is used to analyse the time-dependent temperature distribution of both normal and abnormal tissues. Comparison between temperature profiles of both normal and abnormal tissue has been done using finite element approach with bilinear shape functions in polar coordinates. A computer program in MATLAB has been developed to simulate the results.

Antibacterial biomaterials for skin wound dressing

Bacterial infection and the ever-increasing bacterial resistance have imposed severe threat to human health.And bacterial contamination could significantly menace the wound healing process.Considering the sophisticated wound healing process,novel strategies for skin tissue engineering are focused on the integration of bioactive ingredients,antibacterial agents included,into biomaterials with different morphologies to improve cell behaviors and promote wound healing.However,a comprehensive review on antibacterial wound dressing to enhance wound healing has not been reported.In this review,various antibacterial biomaterials as wound dressings will be discussed.Different kinds of antibacterial agents,including antibiotics,nanoparticles(metal and metallic oxides,lightinduced antibacterial agents),cationic organic agents,and others,and their recent advances are summarized.Biomaterial selection and fabrication of biomaterials with different structures and forms,including films,hydrogel,electrospun nanofibers,sponge,foam and three-dimension(3D)printed scaffold for skin regeneration,are elaborated discussed.Current challenges and the future perspectives are presented in thismultidisciplinary field.We envision that this review will provide a general insight to the elegant design and further refinement of wound dressing.

Intraoperative bioprinting of human adipose-derived stem cells and extra-cellular matrix induces hair follicle-like downgrowths and adipose tissue formation during full-thickness craniomaxillofacial skin reconstruction

Craniomaxillofacial(CMF)reconstruction is a challenging clinical dilemma.It often necessitates skin replacement in the form of autologous graft or flap surgery,which differ from one another based on hypodermal/dermal content.Unfortunately,both approaches are plagued by scarring,poor cosmesis,inadequate restoration of native anatomy and hair,alopecia,donor site morbidity,and potential for failure.Therefore,new reconstructive approaches are warranted,and tissue engineered skin represents an exciting alternative.In this study,we demonstrated the reconstruction of CMF full-thickness skin defects using intraoperative bioprinting(IOB),which enabled the repair of defects via direct bioprinting of multiple layers of skin on immunodeficient rats in a surgical setting.Using a newly formulated patient-sourced allogenic bioink consisting of both human adipose-derived extracellular matrix(adECM)and stem cells(ADSCs),skin loss was reconstructed by precise deposition of the hypodermal and dermal components under three different sets of animal studies.adECM,even at a very low concentration such as 2%or less,has shown to be bioprintable via droplet-based bioprinting and exhibited de novo adipogenic capabilities both in vitro and in vivo.Our findings demonstrate that the combinatorial delivery of adECM and ADSCs facilitated the reconstruction of three full-thickness skin defects,accomplishing near-complete wound closure within two weeks.More importantly,both hypodermal adipogenesis and downgrowth of hair follicle-like structures were achieved in this two-week time frame.Our approach illustrates the translational potential of using human-derived materials and IOB technologies for full-thickness skin loss.

Effect of viscoelasticity on skin pain sensation

Pain sensation may appear under long-lasting mechanical stimulation. Although people have the experience that pain sensation generally decreases with time while the stimulation remains, the underlying mechanism remains elusive. We experimentally studied the thermal and strain rate- dependent viscoelastic behavior of skin in uniaxial stretch and numerically investigated the effects of temperature and strain rate on pain sensation. The results indicate that the viscosity of skin tissue decreases with increasing temperature and reducing strain rate, which subsequently decreases the discharge frequency of skin nociceptor and thus relieves the pain sensation. The results would contribute to the understanding of pain relief mechanism and optimizing for mechanical treatment.

AnalysisofdifferencesofgeneexpressionsinkeloidandnormalskinwiththeaidofcDNAmicroarray

Background:Microarray analysis is a popular tool to investigate the function of genes that are responsi-ble for the phenotype of the disease.Keloid is a intricate lesion which is probably modulated by interplay of manygenes.We ventured to study the differences of gene expressions between keloids and normal skins with the aid ofcDNA microarray in order to explore the molecular mechanism underlying keloid formation.Methods:The PCRproducts of 8400 human genes were spotted on a chip in array.The DNAs were t...

Noncoding RNAs and Their Potential Therapeutic Applications in Tissue Engineering

Tissue engineering is a relatively new but rapidly developing field in the medical sciences. Noncoding RNAs(ncRNAs) are functional RNA molecules without a protein-coding function; they can regulate cellular behavior and change the biological milieu of the tissue. The application of ncRNAs in tissue engineering is starting to attract increasing attention as a means of resolving a large number of unmet healthcare needs, although ncRNA-based approaches have not yet entered clinical practice. In-depth research on the regulation and delivery of ncRNAs may improve their application in tissue engineering.The aim of this review is: to outline essential ncRNAs that are related to tissue engineering for the repair and regeneration of nerve, skin, liver, vascular system, and muscle tissue; to discuss their regulation and delivery; and to anticipate their potential therapeutic applications.

Application of a pre-filled tissue expander for preventing soft tissue incarceration during tibial distraction osteogenesis

BACKGROUND Bone transport and distraction osteogenesis has been widely used to treat bone defects after traumatic surgery,but,skin and soft tissue incarceration can be as high as 27.6%.AIM To investigate the efficacy of inserting a tissue expander to prevent soft tissue incarceration.METHODS Between January 2016 and December 2018,12 patients underwent implantation of a tissue expander in the subcutaneous layer in the vicinity of a tibial defect to maintain the soft tissue in position.A certain amount of normal saline was injected into the tissue expander during surgery and was then gradually extracted to shrink the expander during the course of transport distraction osteogenesis.The tissue expander was removed when the two ends of the tibial defect were close enough.RESULTS In all 12 patients,the expanders remained intact in the subcutaneous layer of the bone defect area during the course of transport distraction osteogenesis.When bone transport was adequate,the expander was removed and the bone transport process was completed.During the whole process,there was no incarceration of skin and soft tissue in the bone defect area.Complications occurred in one patient,who experienced poor wound healing.CONCLUSION The pre-filled expander technique can effectively avoid soft tissue incarceration.The authors’primary success with this method indicates that it may be a valuable tool in the management of incarcerated soft tissue.

Genetic and histological relationship between pheromone-secreting tissues of the musk gland and skin of juvenile Chinese forest musk deer(Moschus berezovskii Flerov,1929)

Background The musk glands of adult male Chinese forest musk deer(Moschus berezovskii Flerov,1929)(FMD),which are considered as special skin glands,secrete a mixture of sebum,lipids,and proteins into the musk pod.Together,these components form musk,which plays an important role in attracting females during the breeding season.However,the relationship between the musk glands and skin of Chinese FMD remains undiscovered.Here,the musk gland and skin of Chinese FMD were examined using histological analysis and RNA sequencing(RNA-seq),and the expression of key regulatory genes was evaluated to determine whether the musk gland is derived from the skin.Methods A comparative analysis of musk gland anatomy between juvenile and adult Chinese FMD was conducted.Then,based on the anatomical structure of the musk gland,skin tissues from the abdomen and back as well as musk gland tissues were obtained from three juvenile FMD.These tissues were used for RNA-seq,hematoxylin-eosin(HE)staining,immunohistochemistry(IHC),western blot(WB),and quantitative real-time polymerase chain reaction(qRT-PCR)experiments.Results Anatomical analysis showed that only adult male FMD had a complete glandular organ and musk pod,while juvenile FMD did not have any well-developed musk pods.Transcriptomic data revealed that 88.24%of genes were co-expressed in the skin and musk gland tissues.Kyoto Encyclopedia of Genes and Genomes(KEGG)signaling pathway analysis found that the genes co-expressed in the abdomen skin,back skin,and musk gland were enriched in biological development,endocrine system,lipid metabolism,and other pathways.Gene Ontology(GO)enrichment analysis indicated that the genes expressed in these tissues were enriched in biological processes such as multicellular development and cell division.Moreover,the Metascape predictive analysis tool demonstrated that genes expressed in musk glands were skin tissue-specific.qRT-PCR and WB revealed that sex-determining region Y-box protein 9(Sox9),Caveolin-1(Cav-1),and androgen receptor(AR)were expressed in all three tissues,although the expression levels differed among the tissues.According to the IHC results,Sox9 and AR were expressed in the nuclei of sebaceous gland,hair follicle,and musk gland cells,whereas Cav-1 was expressed in the cell membrane.Conclusions The musk gland of Chinese FMD may be a derivative of skin tissue,and Sox9,Cav-1,and AR may play significant roles in musk gland development.

Characteristics of a kHz helium atmospheric pressure plasma jet interacting with two kinds of targets

This study investigates the influence of two types of target,skin tissue and cell culture medium,with different permittivities on a k Hz helium atmospheric pressure plasma jet(APPJ)during its application for wound healing.The basic optical-electrical characteristics,the initiation and propagation and the emission spectra of the He APPJ under different working conditions are explored.The experimental results show that,compared with a jet freely expanding in air,the diameter and intensity of the plasma plume outside the nozzle increase when it interacts with the pigskin and cell culture medium targets,and the mean velocity of the plasma bullet from the tube nozzle to a distance of 15 mm is also significantly increased.There are also multiple increases in the relative intensity of OH(A^(2)Σ→X^(2)Π)and O(3p^(5)S-3s^(5)S)at a position 15 mm away from nozzle when the He APPJ interacts with cell culture medium compared with the air and pigskin targets.Taking the surface charging of the low permittivity material capacitance and the strengthened electric field intensity into account,they make the various characteristics of He APPJ interacting with two different targets together.

Engineered artificial skins:Current construction strategies and applications

Skin damage resulting from burns,injuries,or diseases can lead to significant functional and esthetic deficits.However,traditional treatments,such as skin grafting,have limitations including limited donor skin availability,poor aesthetics,and functional impairment.Skin tissue engineering provides a promising alternative,with engineered artificial skins offering a highly viable avenue.Engineered artificial skin is designed to mimic or replace the functions of natural human skin and find applications in various medical treatments,particularly for severe burns,chronic wounds,and other skin injuries or defects.These artificial skins aim to promote wound healing,provide temporary coverage,permanent skin replacement,and restore the skin’s barrier function.Artificial skins have diverse applications in medicine and wound care,addressing burns,chronic wounds,and traumatic injuries.They also serve as valuable tools for research in tissue engineering,offering experimental models for studying wound healing mechanisms,testing new biomaterials,and exploring innovative approaches to skin regeneration.This review provides an overview of current construction strategies for engineered artificial skin,including cell sources,biomaterials,and construction techniques.It further explores the primary application areas and future prospects of artificial skin,highlighting their potential to revolutionize skin reconstruction and advance the field of regenerative medicine.

Molecular Epidemiology of Staphylococcus aureus among Patients with Skin and Soft Tissue Infections in Two Chinese Hospitals

Background：Staphylococcus aureus is one of the predominant causes of skin and soft tissue infections （SSTIs）,but limited data were available regarding the characterization of S.aureus from SSTIs patients in Jiangsu Province in China.We aimed to investigate the molecular epidemiology ofS.aureus among SSTIs patients in two hospitals of Jiangsu Province.Methods：Sixty-two patients with SSTIs from two Chinese hospitals in Jiangsu Province were enrolled in this study,and 62 S.aureus isolates were collected from February 2014 to January 2015.S.aureus isolates were characterized by antimicrobial susceptibility testing,toxin gene detection,and molecular typing with sequence type,Staphylococcus protein A gene type,accessorygeneregulator（agr）group,and Staphylococcal cassette chromosome mec type.Results：Sixteen （25.8%） methicillin-resistant S.aureus （MRSA） isolates were detected,and there was no isolate found resistant to vancomycin,teicoplanin,sulfamethoxazole-trimethoprim,and linezolid.The sei was the toxin gene most frequently found,and no lukS/F-PV-positive isolates were detected among the SSTIs＆#39; patients.Molecular analysis revealed that ST398 （10/62,16.1%;2 MRSA and 8 methicillin-susceptible S.aureus） to be the dominant clone,followed by ST5 （8/62,12.9%） and ST7 （8/62,12.9%）.Conclusions：The livestock ST398 was the most common clone among patients with S.aureus SSTIs in Jiangsu Province,China.Surveillance and further studies on the important livestock ST398 clone in human infections are necessarily requested.