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Three-dimensional (3D) cultured skin containing vascular networks is a useful skin substitute that enables rapid reperfusion after transplantation. During its cultivation, however, insufficient nutrient delivery to the thick cultured tissue from the surrounding culture medium decreases the tissue viability. To solve this problem, in this study, we applied photobiomodulation (PBM), which can optically activate the electron transport chain of mitochondria, to human 3D skin cultures constructed using the layer-by-layer cell coating technique. PBM was applied once 5 days after the start of epidermal differentiation using a light-emitting diode array with a center wavelength of 440, 523, 658 or 823 nm at a constant light intensity of 15 mW cmsup-2/supfor 50 or 600 s. Two days after PBM, we assessed the viability of the tissues by a water-soluble tetrazolium-8 assay, adenosine triphosphate measurements and live/dead cell imaging, and the results showed that the PBM at 823 nm for 50 s (0.75 J cmsup-2/sup) significantly improved the viability of the 3D-cultured skin.

Microfluidic spinning technology (MST), incorporating microfluidics with chemical reactions, has fastened considerable interests in constructing anisotropic advanced microfibers, especially helical microfibers. However, subsistent efforts suffer from the limited material choices, restricting their applications. Here, a new phase inversion-based microfluidic spinning (PIMS) method is proposed for producing helical microfibers. This method undergoes a physicochemical phase inversion process, which is capable of efficiently manufacturing strong (tensile stress of more than 25 MPa), stretchable, flexible and biocompatible helical microfibers. The helical microfibers can be used to fabricate bi-oriented stretchable artificial abdominal skin, preventing incisional hernia formation and promoting the wound healing without conglutination. This research not only offers a universal approach to design helical microfibers, but also provides a new insight into artificial skins.

Optimal treatment of full‐thickness skin injuries requires dermal and epidermal replacement. To spare donor dermis, dermal substitutes can be used ahead of split‐thickness skin graft (STSG) application. However, this two‐stage procedure requires an additional general anaesthetic, often prolongs hospitalisation, and increases outpatient services. Although a few case series have described successful single‐stage reconstructions, with application of both STSG and dermal substitute at the index operation, we have little understanding of how the physical characteristics of dermal substitutes affects the success of a single‐stage procedure. Here, we evaluated several dermal substitutes to optimise single‐stage skin replacement in a preclinical porcine model. A porcine full‐thickness excisional wound model was used to evaluate the following dermal substitutes: autologous dermal graft (ADG; thicknesses 0.15‐0.60 mm), Integra (0.4‐0.8 mm), Alloderm (0.9‐1.6 mm), and chitosan‐based hydrogel (0.1‐0.2 mm). After excision, each wound was treated with either a dermal substitute followed by STSG or STSG alone (control). Endpoints included graft take at postoperative days (PODs) 7 and 14, wound closure at POD 28, and wound contracture from POD 28‐120. Graft take was highest in the STSG alone and hydrogel groups at POD 14 (86.9% ± 19.5% and 81.3% ± 12.3%, respectively; P

To investigate the effect of artificial skin on the expression of miR-155 and miR-506-3p in patients with second-degree burns.The study subjects included 50 patients with second-degree burns treated from July 2019 to July 2021. The control group received routine nursing, while the research group received both routine and artificial skin intervention simultaneously. The changes in wound tissue fibrosis and prognosis were observed. The expression levels of miR-155 and miR-506-3p and their downstream regulatory factors were detected and correlated with the rehabilitation of patients after artificial skin treatment.After treating second-degree burns with artificial skin membranes, the patient's wound tissue fibrosis and inflammation level improved. At the same time, the expression levels of miR-155 and miR-506-3p in related tests were higher than those in patients with available treatment.The effect of artificial skin membrane on the wound healing of second-degree burn patients may be realized by influencing the expression levels of miR-155 and miR-506-3p and their related signaling pathways.

Current wound scaffold dressing constructs can facilitate wound healing but do not exhibit antibacterial activity, resulting in high infection rates. We aimed to endow wound scaffold dressing with anti-infective ability by polyhexamethylenebiguanide (PHMB). We prepared PHMB hydrogel at varying concentrations (0.25%, 0.5%, 1%, 2%) and assessed release and cytotoxicity. PHMB hydrogel was added to the wound scaffold dressing to generate a PHMB hydrogel-modified wound scaffold dressing. Wound healing and infection prevention were evaluated using a full-thickness skin defect model in rats. In vitro, the hydrogel PHMB release time positively correlated with PHMB concentration, with 1% allowing sufficiently long release time to encompass the high-incidence period (3-5 days) of infection following wound scaffold dressing implantation. Implantation of 1% PHMB hydrogel into the skin did not cause adverse responses. in vitro cytotoxicity assays showed the PHMB hydrogel-modified wound scaffold dressing did not significantly affect proliferation of fibroblasts or vascular endothelial cells, 99.90% vs 99.84% for fibroblasts and 100.21% vs 99.28% for vascular endothelial cells at 21 days. Transplantation of PHMB hydrogel-modified wound scaffold dressing/unmodified wound scaffold dressing on the non-infected wounds of rats yielded no significant difference in relative vascularization rate, 47.40 vs 50.87 per view at 21 days, whereas bacterial content of the wound tissue in the PHMB hydrogel-modified wound scaffold dressing group was significantly lower than the unmodified wound scaffold dressing group, (1.80 ± 0.35) × 103 vs (9.34 ± 0.45) × 103 at 14 days. Prevalence of persistent wound infection in the rats receiving PHMB hydrogel-modified wound scaffold dressing transplantation onto infected wounds was significantly lower than the unmodified wound scaffold dressing group, 30% vs 100%. PHMB hydrogel-modified wound scaffold dressing exhibited suitable antibacterial ability, and its biological activity did not significantly differ from that of the unmodified wound scaffold dressing, thereby allowing it to effectively prevent infection following wound scaffold dressing implantation.

Background There is not an ideal biomaterial for tissue-engineered skin substitutes (TESSs), and most of the studies or existing therapies use xenogeneic origin natural biomaterials or biosynthetic scaffolds. Objective To analyse clinical, histological integration and homeostasis parameters of a human TESS manufactured with fibrin-hyaluronic acid biomaterial (HA-Skin), grafted in immunodeficient mice for 8 weeks, and compared with the gold standard treatment (Autograft), a human TESS manufactured with fibrin-agarose biomaterial (AG-Skin) and secondary wound healing dressings. Methods Human TESSs and autografts were implanted into BALB/c mice after surgical excision. Secondary wound healing approach was achieved with biosynthetic collagen wound dressing (Biobrane® ) and fibrin-hyaluronic acid or fibrin-agarose biomaterial without cells (Total N = 44). Clinical integration and homeostasis parameters were evaluated every two weeks for two months. Histological and immunohistochemical analyses were performed four and eight weeks after grafting. Results HA-Skin, AG-Skin and Autograft groups showed a proper clinical integration and epithelization eight weeks later. Scar evaluation revealed better results for Autograft and HA-Skin. Homeostasis analysis indicated similar values of transepidermal water loss and elasticity between HA-Skin (6.42 ± 0.75 g/h/m2 , 0.42 ± 0.08 AU), Autograft (6.91 ± 1.28 g/h/m2 , 0.40 ± 0.08 AU) and healthy mouse skin (6.40 ± 0.43 g/h/m2 , 0.35 ± 0.03 AU). Histological results showed that human TESSs and autografts presented better skin structuration and higher expression of cytokeratins. Conclusions This study suggests that human TESS based on fibrin-hyaluronic acid biomaterial could be suitable for clinical application in the treatment of several dermatological pathologies (wound healing).

Polysiloxane-based artificial skins are able to emulate the mechanical and barrier performance of human skin. However, they are usually fabricated in vitro, restricting their diverse applications on human body. Herein, we presented one-component waterborne cross-linkable polysiloxane coatings prepared from emulsified vinyl dimethicone, emulsified hydrogen dimethicone, and Karstedt catalyst capsules that were first synthesized by solvent evaporation method. The coating had good storage stability and meanwhile could form an elastic film quickly through merging of silicone oil droplets and subsequent hydrosilylation reaction. It was found that the mass ratio of vinyl dimethicone emulsion/hydrogen dimethicone emulsion (V/H), and the dosage of Karstedt catalyst capsules (K/(V + H)) were critical to the curing time, morphology, and mechanical properties of the coatings. With appropriate values of V/H and K/(V + H), the polysiloxane film had the mechanical performance comparable to that from solvent-based one. The coating could be topically applied to human skin in vivo and in situ turned into an elastic, invisible thin film with good water resistance. In contrast to those reported polysiloxane materials, the one-component waterborne polysiloxane coating was nontoxic and convenient for in vivo application on human body, making it be a promising candidate as artificial skin in the fields of cosmetics, medical treatment, and E-skin.

Patients with extensive and deep burns who do not have enough donor sites for autologous skin grafts require alternative treatment methods. Tissue engineering is a useful tool to solve this problem. The aim of this study was to find the optimal method for the production of a biovital skin substitute based on acellular dermal matrix (ADM) and in vitro cultured fibroblasts and keratinocytes. In this work, nine methods of ADM production were assessed. The proposed methods are based on the use of the following enzymes: Dispase II, collagenase I/ethylenediaminetetraacetic acid (EDTA), collagenase II/EDTA, and mechanical perforation using DermaRoller and mesh dermatome. The obtained ADMs were examined (both on the side of the basement membrane and on the "cut-off" side) by means of scanning electron microscopy, immunohistochemistry tests and strength tests. ADM was revitalized with human fibroblasts and keratinocytes. The ability of in-depth revitalization of cultured fibroblasts and their ability to secrete collagen IV was examined. The obtained results indicate that the optimal method of production of live skin substitutes is the colonization of autologous fibroblasts and keratinocytes on the scaffold obtained using two-step incubation method: Trypsin/EDTA and dispase II.

Cell-based skin substitute generation has seen considerable development. Combining synthetic scaffolds with biomimetic fibrin does direct both exogenous and endogenous stem cell differentiation, addressing needs for reliable tissue engineering. However, lack of immediate vasculature within implantable grafts remains critical for its sustenance and integration. Multipotency, high proliferation potential, ability to release multiple growth factors (GFs), and autologous availability highlight the use of human adipose derived mesenchymal stem cells (hADMSCs) in tissue-engineered dermal grafts (TEDG) construction. However, hADMSCs' insufficiency to independently establish angiogenesis within tissue constructs demands improvement of stem cell application for dermal graft survival. Approaches to harness microenvironmentally sensitive paracrine interactions could improve the angiogenic efficiency of hADMSCs within TEDG. This study conceptualized a fibrin-based niche, to direct hADMSCs toward a nonfibrotic fibroblast commitment and incorporation of bioengineered hADMSCs, specifically releasing potent angiogenic factors within TEDG. Coexistence of tuned fibroblast and endothelial lineage committed cells contributed to well-regulated extracellular matrix formation and prevascularization. Adequate cell proliferation; sustained transient release of angiogenic GFs till 20 days; directed dermal, endothelial, fibroblast, and vascular smooth muscle cell differentiation; and favored elastin and collagen deposition were achieved in vitro. In conclusion, specific niche composition and employment of bioengineered hADMSCs favor implantable TEDG construction.

Ultrafast artificial skin enables unprecedented tactile internet applications in prosthetics, robotics, and human-machine interactions. However, current artificial skin systems that rely on front-end interface electronics typically perform redundant data transfer and analogue-to-digital conversions for decision-making, causing long latency (milliseconds). Here, a near-sensor analogue computing system based on a flexible memristor array for artificial skin applications is reported. This system, which seamlessly integrates a tactile sensor array with a flexible hafnium oxide memristor array, can simultaneously sense and compute raw multiple analogue pressure signals without interface electronics. As a proof-of-concept, the system is used for real-time noise reduction and edge detection of tactile stimuli. One sensing-computing operation of this system takes about 400 ns and consumes on average 1000 times less power than a conventional interface electronic system. The results demonstrate that near-sensor analogue computing offers an ultrafast and energy-efficient route to large-scale artificial skin systems. Agency for Science, Technology and Research (A*STAR) Ministry of Education (MOE) National Research Foundation (NRF) Submitted/Accepted version The project was partially supported by the National Key R&D Program of China under Grant (2021YFB3601200), the National Nature Science Foundation of China (62104042), the Agency for Science, Technology and Research (A*STAR) under its AME Programmatic Funding Scheme (Project #A18A1b0045), the National Research Foundation (NRF), Prime Minister’s office, Singapore, under its NRF Investigatorship (NRF-NRFI2017-07), and Singapore Ministry of Education (MOE2019-T2-2-022).

While rapid wound healing is essential yet challenging, there is also an unmet need for functional restoration of sensation. Inspired by natural skin, an ultra‐conformable, adhesive multi‐functional ionic skin (MiS) with multi‐modal sensing capability is devised for smart and expedited wound care. The base of MiS is a unique skin‐like, conductive and self‐adaptive adhesive polyacrylamide/starch double‐network hydrogel (PSH) and self‐powered, flexible, triboelectric sensor(s) is integrated on top of PSH for multi‐tactile sensing. MiS could enhance wound contraction, collagen deposition, angiogenesis, and epidermis formation in a full‐thickness skin defect wound model in vivo, while significantly inhibiting the biofilm formation of a wide range of microorganisms. MiS also exhibits multi‐modal sensing capability for smart and instant therapeutics and diagnostics, including skin displacement or joint motion, temperature, pressure and tissue exudate changes of wound bed, and locally releasing drugs in a pH‐responsive manner. More importantly, MiS could restore the skin‐mimicking tactile sensing function of both touch location and intensity, and thus could be used as a human‐machine interface for accurate external robotic control. MiS demonstrates a new comprehensive paradigm of combining wound diagnosis and healing, broad‐spectrum anti‐microbial capability and restoration of multi‐tactile sensing for the reparation of severe wound., An ultra‐conformable, adhesive multi‐functional ionic skin (MiS) with multi‐modal sensing capability is devised for smart and expedited wound care. MiS is composed of a polyacrylamide/starch double‐network hydrogel and a self‐powered, flexible, triboelectric sensor. MiS demonstrates a comprehensive paradigm of combining wound diagnosis and healing, broad‐spectrum anti‐microbial capability and restoration of multi‐tactile sensing for advanced wound management.

Recently, we reported that some wound dressings caused complement activation at the interface of wound dressing and blood. Since complement activation is associated with impaired wound healing, we investigated whether this activation of the complement cascade at the interface of wound dressings and blood does impair reepithelialization in a scratch wound healing assay. Although some samples showed higher levels of the complement activation marker SC5b-9 in our study, reepithelialization of the samples did not significantly differ from the control group. Further studies have to clarify if complement activation at the interface of wound dressings and blood plays a relevant role in the healing process especially in long-time experiments.

The use of split-thickness skin autografts (STSA) with dermal substitutes is the gold standard treatment for third-degree burn patients. In this article, we tested whether cryopreserved amniotic membranes could be beneficial to the current treatments for full-thickness burns. Swines were subjected to standardised full-thickness burn injuries, and then were randomly assigned to treatments: (a) STSA alone; (b) STSA associated with the dermal substitute, Matriderm; (c) STSA plus human amniotic membrane (HAM); and (d) STSA associated with Matriderm plus HAM. Clinical and histological assessments were performed over time. We also reported the clinical use of HAM in one patient. The addition of HAM to classic treatments reduced scar contraction. In the presence of HAM, skin wound healing displayed high elasticity and histological examination showed a dense network of long elastic fibres. The presence of HAM increased dermal neovascularization, but no effect was observed on the recruitment of inflammatory cells to the wound. Moreover, the use of HAM with classical treatments in one human patient revealed a clear benefit in terms of elasticity. These results give initial evidence to consider the clinical application of HAM to avoid post-burn contractures and therefore facilitate functional recovery after deep burn injury.

Composition and architecture of scaffolds are the most important factors determining the performance of skin substitutes. In this work, morphology induced unique physical and biological characteristics of compatibilized TPU-PDMS blend scaffolds at 90:10, 80:20, and 70:30 blend ratios of TPU and PDMS was studied. The fiber morphology, porosity, surface wettability, and mechanical properties of electrospun scaffolds were distinctly influenced by the presence of PDMS. Interestingly, the scaffold architecture varied from electrospun fibers to porous fibers and finally occurrence of unique porous beads noticed at 30% PDMS in the microstructure which was confirmed using FESEM. Micro-CT analysis revealed that the porosity of electrospun scaffolds was enhanced from 61% to 79% with 30 parts of PDMS addition. Moreover, MTT assay and cell proliferation were studied using human skin fibroblast cells and found to be significantly enhanced with the PDMS percentage. TPU-PDMS blends offer better overall performance at 70:30 blend ratio of TPU and PDMS (T70P30). Only 4% of hemolysis was observed for T70P30 blends, which establishes the hemocompatibility of the material. In comparison, the results reveal the potential of the cytocompatible T70P30 scaffold for the fabrication of skin substitutes for tissue engineering applications. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 1634-1644, 2019.

Continuous contraction of 3D skin equivalents in construction and use restricts their applications in clinical and pharmaceutical practices. So far, no effective method has been developed to inhibit such contraction. Hence, low cytotoxic cross-linkers, 1-ethyl-3-3-dimethylaminopropylcarbodiimide hydrochloride (EDC) and genipin, are investigated to reduce the contraction in this study. As found, both genipin and EDC at 0.2 and 0.4 mmol/L are nontoxic to collagen-entrapped fibroblasts and upregulate the extracellular matrix expression of fibroblasts in cross-linked collagen. Particularly, collagen cross-linking by intermediate concentrations of genipin, specifically 0.4 mmol/L, greatly reduces the contraction of 3D skin equivalents from 87% to 28% (n = 9, P

Double layer dermal substitute (DS) consist of a 3‐dimensional collagen structures and a superficial silicon layer that are positioned within the defect provide to promote tissue regeneration in skin wounds. DS often have unique physical characteristics due to differences in manufacturing techniques. The aim of this study is the clinical and histological comparison of Nevelia and Integra double layer DSs in patients with post‐traumatic injury wounds. Thirty patients with post‐traumatic wounds localised on the inferior limbs were randomised in 2 groups Nevelia or Integra, followed by autologous dermal epidermal graft (DEG). Clinical results were evaluated through the healing time; Manchester Scar Scale (MSS) and Visual Analog Scale (VAS) at 1, 2, and 3 weeks and after 1 and 3 years. Histological and immunohistochemical evaluation were performed at 0, 2, and 3 weeks. The difference in healing time between groups (P = .467, log‐rank test), pain and self‐estimation was not statistically significant after 35, 42, and 49 days and at 1‐year follow up. Histological data showed evident healing of wound after 2 weeks compared with preoperative with both DSs. At 3 weeks reepithelialisation and dermal regeneration were evident with both substitutes; however Nevelia showed early regenerative properties in terms of epidermal proliferation and dermal renewal compared with Integra. Nevelia showed also a more evident angiogenesis vs Integra evaluated as α‐SMA immunohistochemistry. Differences in the MSS score were statistically significant at 3 years follow up in favour of Nevelia group (P = .001). At long‐term follow up, Nevelia showed a better clinical outcome measured as MSS score vs Integra measured as MSS. Histological and immunohistochemistry data showed that Nevelia allows faster neoangiogenesis and tissue regeneration with neoformed tissue architecture closer to the physiology of the skin.

Dermal substitutes are frequently used for the initial coverage of extensive skin defects. The seeding of these implants with adipose tissue-derived microvascular fragments (ad-MVF) has recently been shown to accelerate their vascularization and incorporation. In the present study we analyzed whether these processes are affected by a thromboprophylactic therapy with the low molecular weight heparin (LMWH) enoxaparin (enox). Green fluorescent protein (GFP)+ ad-MVF were isolated from enox- (8 mg/kg s.c.) and vehicle-treated (0.9% NaCl s.c.) (C57BL/6-Tg(CAG-EGFP)1Osb/J mice and seeded onto Integra matrices. Subsequently, these were implanted into full-thickness skin defects within dorsal skinfold chambers of enox- and vehicle-treated C57BL/6 wild-type mice. Repetitive stereomicroscopy and intravital fluorescence microscopy over 2 weeks as well as histological and immunohistochemical analyses on day 14 revealed that enox does not inhibit the reassembly of ad-MVF into new microvascular networks. In addition, treatment with the anticoagulative compound did not promote implant-induced hemorrhage formation. Accordingly, Integra matrices in enox- and vehicle-treated animals exhibited a comparable final microvessel density, fraction of GFP+ blood vessels originating from seeded ad-MVF, collagen fiber content, and epithelialization. These novel findings demonstrate that the seeding of dermal substitutes with ad-MVF may be applied also during thromboprophylactic therapy without affecting implant vascularization and bleeding risk.

BACKGROUND/PURPOSE During the injection of a fluid in a tissue model, the fluid might be affected by the needle tip configuration and the number of channels. Thus, the objective of the present work is to observe the influence of different needle tips and number of channels on the spread of a fluid. METHODS Fluid distribution data were obtained after injecting 0.3 mL of fluid into a foamed polymer model with a velocity of 2 mm/s. The spread area and the depth were determined for 3 different types of hypodermic needles: Single channel needles with bevel tip and blunt tip and a needle with conical tip and 3 internal channels. RESULTS The bevel tip provides a higher spread in the direction where the bevel points and reaches larger depths than the other two needles. The spread for the blunt tip and the polymer needle is equally distributed on both sides of the needle. The largest horizontal area around the tip is achieved by the 3-channel needle. CONCLUSION The tip configuration and number of channels have an influence on the distribution of fluid. The bevelled needle directs the fluid and reaches larger depths compared with the 3-channel needle that gets more horizontal spread.

Large skin wounds pose a major clinical challenge. Scarcity of donor site and postsurgical scarring contribute to the incomplete or partial loss of function and aesthetic concerns in skin wound patients. Currently, a wide variety of skin grafts are being applied in clinical settings. Scaffolds are used to overcome the issues related to the misaligned architecture of the repaired skin tissues. The current review summarizes the contribution of biomaterials to wound healing and skin regeneration and addresses the existing limitations in skin grafting. Then, the clinically approved biologic and synthetic skin substitutes are extensively reviewed. Next, the techniques for modification of skin grafts aiming for enhanced tissue regeneration are outlined, and a summary of different growth factor delivery systems using biomaterials is presented. Considering the significant progress in biomaterial science and manufacturing technologies, the idea of biomaterial-based skin grafts with the ability for scarless wound healing and reconstructing full skin organ is more achievable than ever.

Autologous engineered skin substitutes (ESS) containing melanocytes (hM) may restore pigmentation and photoprotection after grafting to full-thickness skin wounds. In this study, normal hM were isolated from discard skin, propagated with or without tyrosinase inhibitors, cryopreserved, recovered into culture, and added to ESS (ESS-P) before transplantation. ESS-P were incubated in either UCMC160/161 or UCDM1 medium, scored for hM densities, and grafted to mice. The results showed that sufficient hM can be propagated to expand donor tissue by 100-fold; incubation of hM in tyrosinase inhibitors reduced pigment levels but did not change hM recovery after cryopreservation; hM densities in ESS-P were greater after incubation in UCDM1 than UCMC160 medium; hM were localized to the dermal-epidermal junction of ESS-P; and UCDM1 medium promoted earlier pigment distribution and density. These results indicate that hM can be incorporated into ESS-P efficiently to restore cutaneous pigmentation and UV photoprotection after full-thickness skin loss conditions.

The skin is the largest organ in the human body, and skin defects are very common. Skin flap transplantation is the best treatment for serious wound defects, and donor site tissues are always sacrificed during this process. Decellularized biomaterials, derived mainly from various nonautologous organs and tissues, have promising applications in tissue engineering and repair of wound defects. To date, decellularized mesothelium, intestine, amniotic membrane, dermis, and skin flaps have been developed and applied for skin coverage in animal models and clinical practice. In this review, we discuss recent advances in decellularized biomaterials for skin substitutes and future perspectives. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 1849-1859, 2019.

Human artificial skin models are increasingly employed as non-animal test platforms for research and medical purposes. However, the overall histopathological quality of such models may vary significantly. Therefore, the effects of manufacturing protocols and donor sources on the quality of skin models built-up from fibroblasts and keratinocytes derived from juvenile foreskins is studied. Histo-morphological parameters such as epidermal thickness, number of epidermal cell layers, dermal thickness, dermo-epidermal adhesion and absence of cellular nuclei in the corneal layer are obtained and scored accordingly. In total, 144 full-thickness skin models derived from 16 different donors, built-up in triplicates using three different culture conditions were successfully generated. In univariate analysis both media and donor age affected the quality of skin models significantly. Both parameters remained statistically significant in multivariate analyses. Performing general linear model analyses we could show that individual medium-donor-interactions influence the quality. These observations suggest that the optimal choice of media may differ from donor to donor and coincides with findings where significant inter-individual variations of growth rates in keratinocytes and fibroblasts have been described. Thus, the consideration of individual medium-donor-interactions may improve the overall quality of human organ models thereby forming a reproducible test platform for sophisticated clinical research.

Skin is the largest organ with the functionalities of protection, regulation and sensation. The emulation of human skin via flexible and stretchable electronics gives rise to electronic skin (e-skin), which has realized artificial sensations and other functions that cannot be achieved by conventional electronics, such as stretchability and self-healing. To date, tremendous progress has been made in data acquisition and transmission for e-skin systems, while the implementation of perception within systems, i.e. sensory data processing, is still in its infancy. Integrating the perception functionality into a flexible and stretchable sensing system, namely artificial skin perception, is critical to endow current e-skin systems with higher intelligence. Here, recent progresses in the design and fabrication of artificial skin perception devices and systems are summarized, as well as challenges and prospects are discussed. The strategies for implementing artificial skin perception utilize either conventional silicon-based circuits or novel flexible computing devices such as memristive devices and synaptic transistors, which enable artificial skin to surpass the human skin with a distributed, low-latency and energy-efficient information processing ability. In future, artificial skin perception would be a new enabling technology to construct next-generation intelligent electronic devices and systems, paving the way for advanced soft robotic applications, such as surgical assistance, rehabilitation, and prosthetics. Agency for Science, Technology and Research (A*STAR) Ministry of Education (MOE) National Research Foundation (NRF) Accepted version We thank the financial support from the Agency for Science, Technology and Research (A*STAR) under its AME Programmatic Funding Scheme for the Project of Cyber- Physiochemical Interfaces (Project #A18A1b0045), Singapore Ministry of Education (MOE2017-T2-2-107 and MOE2019-T2-2-022), and the National Research Foundation (NRF), Prime Minister’s office, Singapore, under its NRF Investigatorship (NRF-NRFI2017- 07).

Flexible and lightweight pressure sensors have attracted tremendous attention as a promising component of wearable biological motion sensors and artificial electronic skins. Here, the electromechanical response of as-electrospun fiber mats composed of a commodity polymer, atactic polystyrene, which can be applied in low-cost/large-area, flexible, and lightweight pressure sensors is demonstrated. The fiber mat demonstrates a significantly high apparent converse piezoelectric constant of >30 000 pm V-1 under static measurement and ≈13 000 pm V-1 even at a high frequency of 1 kHz. The first theoretical model to explain the unique electromechanical response is constructed, which reveals that the softness and moderate charge of the fiber mat are the reasons for the significantly high electromechanical response. Further, apparent piezoelectric constants obtained by direct measurement are lower than those obtained by the converse measurement, which is attributed to the densification and hardening of the fiber mat due to prepressure applied in direct measurement. These findings are likely to serve as a milestone for the development of large-area, flexible, and lightweight pressure sensors at low cost, as well as highly movable actuators like optical modulators without a substantial mechanical load.

A randomised, controlled multicentre clinical trial was conducted at 14 wound care centres in the United States to confirm the efficacy of dehydrated human amnion/chorion membrane allograft (dHACM) for the treatment of chronic lower extremity ulcers in persons with diabetes. Patients with a lower extremity ulcer of at least 4 weeks duration were entered into a 2-week study run-in phase and treated with alginate wound dressings and appropriate offloading. Those with less than or equal to 25% wound closure after run-in were randomly assigned to receive weekly dHACM application in addition to offloading or standard of care with alginate wound dressings, for 12 weeks. A total of 110 patients were included in the intent-to-treat (ITT) analysis, with n = 54 in the dHACM group and n = 56 in the no-dHACM group. Of the participants, 98 completed the study per protocol, with 47 receiving dHACM and 51 not receiving dHACM. The primary study outcome was percentage of study ulcers completely healed in 12 weeks, with both ITT and per-protocol participants receiving weekly dHACM significantly more likely to completely heal than those not receiving dHACM (ITT-70% versus 50%, P = 0.0338, per-protocol-81% versus 55%, P = 0.0093). A Kaplan-Meier analysis was performed to compare the time-to-healing performance with/without dHACM, showing a significantly improved time to healing with the use of allograft, log-rank P0.0187. Cox regression analysis showed that dHACM-treated subjects were more than twice as likely to heal completely within 12 weeks than no-dHACM subjects (HR: 2.15, 95% confidence interval 1.30-3.57, P = 0.003). At the final follow up at 16 weeks, 95% of dHACM-healed ulcers and 86% of healed ulcers in the no-dHACM group remained closed. These results confirm that dHACM is an efficacious treatment for lower extremity ulcers in a heterogeneous patient population.

Use of naturally derived materials for biomedical applications is steadily increasing. Soy protein has advantages over various types of natural proteins employed for biomedical applications due to its low price, nonanimal origin, and relatively long storage time and stability. In the current study, blends of soy protein with other polymers (gelatin, alginate, pectin, polyvinyl alcohol, and polyethylene glycol) were developed and studied. The mechanical tensile properties of dense films were studied in order to select the best secondary polymer for porous three-dimensional structures. The porous soy-gelatin and soy-alginate structures were then studied for physical properties, degradation behavior, and microstructure. The results show that these blends can be assembled into porous three-dimensional structures by combining chemical crosslinking with freeze-drying. The soy-alginate blends are advantageous over soy-gelatin blends, demonstrated better stability, and degradation time along with controlled swelling behavior due to more effective crosslinking and higher water uptake than soy-gelatin blends. Water vapor transmission rate experiments showed that all porous blend structures were in the desired range for burn treatment [2000-2500 g/(m(2) d)] and can be controlled by the crosslinking process. We conclude that these novel porous three-dimensional structures have a high potential for use as scaffolds for tissue engineering, especially for skin regeneration applications. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 1109-1120, 2016.

Cross talk between fibroblasts and keratinocytes, which maintains skin homeostasis, is disrupted in chronic wounds. For venous leg ulcers and diabetic foot ulcers, a bilayered living cellular construct (BLCC), containing both fibroblasts and keratinocytes that participate in cross talk, is a safe and effective product in healing chronic wounds. To show the importance of both cell types in BLCC, constructs were generated containing only fibroblasts or only keratinocytes and compared directly to BLCC via histology, mechanical testing, gene/protein analysis, and angiogenesis assays. BLCC contained a fully differentiated epithelium and showed greater tensile strength compared with one-cell-type constructs, most likely due to formation of intact basement membrane and well-established stratum corneum in BLCC. Furthermore, expression of important wound healing genes, cytokines, and growth factors was modulated by the cells in BLCC compared with constructs containing only one cell type. Finally, conditioned medium from BLCC promoted greater endothelial network formation compared with media from one-cell-type constructs. Overall, this study characterized a commercially available wound healing product and showed that the presence of both fibroblasts and keratinocytes in BLCC contributed to epithelial stratification, greater tensile strength, modulation of cytokine and growth factor expression, and increased angiogenic properties compared with constructs containing fibroblasts or keratinocytes alone.

The aim of this study is to determine if weekly application of dehydrated human amnion/chorion membrane allograft reduce time to heal more effectively than biweekly application for treatment of diabetic foot ulcers. This was an institutional review board-approved, registered, prospective, randomised, comparative, non-blinded, single-centre clinical trial. Patients with non-infected ulcers of ≥ 4 weeks duration were included for the study. They were randomised to receive weekly or biweekly application of allograft in addition to a non-adherent, moist dressing with compressive wrapping. All wounds were offloaded. The primary study outcome was mean time to healing. Overall, during the 12-week study period, 92·5% (37/40) ulcers completely healed. Mean time to complete healing was 4·1 ± 2·9 versus 2·4 ± 1·8 weeks (P = 0·039) in the biweekly versus weekly groups, respectively. Complete healing occurred in 50% versus 90% by 4 weeks in the biweekly and weekly groups, respectively (P = 0·014). Number of grafts applied to healed wounds was similar at 2·4 ± 1·5 and 2·3 ± 1·8 for biweekly versus weekly groups, respectively (P = 0·841). These results validate previous studies showing that the allograft is an effective treatment for diabetic ulcers and show that wounds treated with weekly application heal more rapidly than with biweekly application. More rapid healing may decrease clinical operational costs and prevent long-term medical complications.

Background/purpose Repeated mechanical stresses applied to the same region of the skin are thought to induce morphological changes known as wrinkle. However, the underlying mechanisms are not fully understood. To study the mechanisms, we examined effects of repeated mechanical stress on the dermal equivalent. Methods We developed a novel device to apply repeated folding stress to the dermal equivalent. After applying the mechanical stress, morphological changes of the dermal equivalent and expression of several genes related to extracellular matrix turn over and cell contraction were examined. Results The repeated folding stress induced a noticeable decrease in the width of the dermal equivalent. The mechanical stress altered orientations of collagen fibrils. Hydroxyproline contents, dry weights and cell viability of the dermal equivalents were not affected by the mechanical stress. On the other hand, Rho-associated coiled-coil-containing kinase (ROCK) specific inhibitor Y27632 completely suppressed the decrease in the width of the dermal equivalent. Conclusion The present results revealed that either degradation of collagen or changes in the number of cells were not responsible for the decrease in the width of the dermal equivalent and indicate that the repeated mechanical stress induces unidirectional contraction in the dermal equivalent through the RhoA-ROCK signaling pathway.

The skin is responsible for several important physiological functions and has enormous clinical significance in wound healing. Tissue engineered substitutes may be used in patients suffering from skin injuries to support regeneration of the epidermis, dermis, or both. Skin substitutes are also gaining traction in the cosmetics and pharmaceutical industries as alternatives to animal models for product testing. Recent biomedical advances, ranging from cellular-level therapies such as mesenchymal stem cell or growth factor delivery, to large-scale biofabrication techniques including 3D printing, have enabled the implementation of unique strategies and novel biomaterials to recapitulate the biological, architectural, and functional complexity of native skin. This progress report highlights some of the latest approaches to skin regeneration and biofabrication using tissue engineering techniques. Current challenges in fabricating multilayered skin are addressed, and perspectives on efforts and strategies to meet those limitations are provided. Commercially available skin substitute technologies are also examined, and strategies to recapitulate native physiology, the role of regulatory agencies in supporting translation, as well as current clinical needs, are reviewed. By considering each of these perspectives while moving from bench to bedside, tissue engineering may be leveraged to create improved skin substitutes for both in vitro testing and clinical applications.

Non healing wounds present a significant social and economic burden. Chronic non healing wounds are estimated to affect as many as 1–2% of individuals during their lifetime, and account for billions of dollars of expense annually on both a national and global basis. Our purpose is to describe the use of a novel dehydrated amniotic membrane allograft (EpiFix ®; MiMedx Group, Inc., Kennesaw, GA) for the treatment of chronic non healing wounds. We describe the results of EpiFix treatment in four patients who had not achieved wound closure with both conservative and advanced measures, and had been referred for a definitive plastic surgery procedure. Healing was observed in a variety of wounds with one to three applications of the dehydrated amniotic membrane material. The material was well tolerated by patients. Healed wounds did not recur in long‐term follow‐up. Further investigation of the use of dehydrated amniotic membrane in broader application to various types of dermal wounds should be considered.

Significant progress has been made in the development of in vitro-engineered skin substitutes that mimic human skin, either to be used for the replacement of lost skin or for the establishment of in vitro skin research models. However, at the present time, there are no models of bioengineered skin that completely replicate the nature of uninjured skin. Obviously, there is still much room for improvement of the components of bioengineered skin and their interplay. This review summarises the important new discoveries in key elements of engineering of tissue-engineered skin including cell sources, biomaterials and growth factors, etc. Furthermore, basic and clinical applications for engineered skin substitutes in cell therapy, tissue engineering, and biomedical research continue to drive design improvements premised on these structure and function-based engineering paradigms.

International audience; The skin is a multifunctional organ and a first line of defense actively protecting from environmental stress caused by injury, microbial treat, UV irradiation and environmental toxins. Diverse cutaneous cell types together with extracellular matrix elements and factors create a dynamic scene for cellular communication crucial in vital processes such as wound healing, inflammation, angiogenesis, immune response. Direct functional success of skin equilibrium depends on its microenvironment settings and particularly the local oxygen tension. Indeed, skin entire milieu is characterized by and highly dependent on its low oxygen tension called physioxia as emphasized in this review. In the context of skin physioxia, we review and propose here new approaches to minimize age-related changes in skin state and function. We particularly emphasize carbohydrate-mediated interactions and new 3D models of engineered skin substitutes. We highlight newly emerged tools and targets including stem cells, miRNAs, matrix metalloproteinases, mitochondria and natural antioxidants that are promising in prevention of skin ageing and disease restraint. In the era of advanced dermatology, new attempts are bringing us closer to 'well being' perception.

Background: We evaluated the use of human amniotic membrane (HAM) as a graft material for the treatment of iatrogenic full-thickness (FT) skin wounds in a porcine model with a view to reducing donor site morbidity in free flap transfer. Methods: Forty experimental FT-wounds were covered with an autologous split-thickness skin graft (STSG) alone or in combination with a mono- or multilayer HAM or Integra®. Untreated wounds served as controls. Clinical evaluation and biopsy-sampling for histological and immunohistochemical staining with von-Willebrand-factor (vWF) antibody, laminin antibody, Ki-67 antibody, and smooth muscle actin (αSMA) antibody were performed on days 5, 7, 10, 20, 40, and 60 after surgical intervention. Results: Considerable disparities in the estimated criteria were observed between the various treatment groups of the FT-wounds. The use of HAM was found to have an accelerating impact on re-epithelialization. The multilayered amnion membrane showed better results than the Integra® and monolayer technique in terms of contraction rate, inflammation, and scarring and seemed useful as a dermal substitute in FT-wounds giving comparable results to STSG coverage alone. Conclusions: This study demonstrates the successful application of HAM as part of a skin substitute in FT-wounds in minipigs. The results offer promise as a simple and effective technique for the application of multilayer HAM in iatrogenic human skin defects and the acceleration of wound healing. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2012.

Widely used polymethylmethacrylate substrates for in vitro sun protection factor (SPF) testing of sunscreens do not mimic the rough surface structure of skin, and in addition, sample loading is less than that used in in vivo SPF testing (2.00 mg cm(-2)). We have developed a skin-mimicking substrate (SMS), which has furrows and ridges on its surface, like human skin. A comparison of the photodegradation profiles of sunscreens on commercially available substrates (including SMS) at the recommended application amounts, and on SMS at various application amounts showed that the photodegradation rate of photounstable sunscreen was dependent on the application amount being higher at lower application amounts. SMS at the recommended application amount of 2.00 mg cm(-2) provided in vitro SPF values that were comparable with in vivo SPF values. Our results confirm that, in order to develop a reliable in vitro SPF method, which is consistent with in vivo SPF determination, it is important to use the same application amount of sample as in the in vivo method, in order to take proper account of sunscreen photostability.

Osteomyelitis of the calcaneus is a difficult problem to manage. Patients affected by osteomyelitis of the calcaneus often have a below-the-knee amputation because of their comorbidity. In this article, we present seven cases of heel ulcerations with chronic osteomyelitis treated with Integra(®) Dermal Regeneration Template, skin graft and negative pressure wound therapy after partial tangential calcanectomy, discussing the surgical and functional results. In this casuistic of patients, all wounds healed after skin grating of the neodermis generated by Integra(®), with no patient requiring a below-knee amputation.

The aim of our case report was to analyse the results obtained with the Matriderm® system and autologous skin grafting for the surgical treatment of skin necrosis of scrotum as a result of endovascular embolisation. We recruited one patient with scrotum skin necrosis as a result of endovascular embolisation admitted at the department of Plastic and Reconstructive Surgery, University of Rome 'Tor Vergata'. The patient underwent Matriderm® system and autologous skin grafting for skin necrosis treatment. After a single treatment, reduction of the skin necrosis was obtained, after 30 days from the surgical treatment. Patient experienced a reduction in pain and a complete restoration of the loss in volume and quality of skin was noticed. Matriderm® system and autologous skin grafting is a simple, safe and feasible technique. When comparing this treatment with others, Matriderm® is a simpler, more economic and less time-consuming method, and does not require sophisticated laboratory facilities.

In this study, nanofibrous matrices of polycaprolactone (PCL) and PCL/collagen with immobilized epidermal growth factor (EGF) were successfully fabricated by electrospinning for the purpose of damaged skin regeneration. Nanofiber diameters were found to be 284 ± 48 nm for PCL and 330 ± 104 nm for PCL/collagen matrices. The porosities were calculated as 85% for PCL and 90% for PCL/collagen matrices. The covalent immobilization of EGF onto the nanofibrous matrices was verified by the increase of surface atomic nitrogen ratio from 1.0 to 2.4% for PCL and from 3.7 to 4.7% for PCL/collagen. Moreover, EGF immobilization efficiencies of PCL and PCL/collagen matrices were determined as 98.5 and 99.2%, respectively. Human dermal keratinocytes (HS2) were cultivated on both neat and EGF immobilized PCL and PCL/collagen matrices to investigate the effects of matrix chemical composition and presence of EGF on cell proliferation and differentiation. EGF immobilized PCL/collagen matrices exerted early cell spreading and rapid proliferation. Statistically high expression levels of loricrin in HS2 cells cultivated on EGF immobilized PCL/collagen matrices were (p < 0.001) regarding superior differentiation ability of these cells compared to HS2 cells cultured on neat PCL and PCL/collagen matrices. In conclusion, this novel EGF immobilized PCL/collagen nanofibrous matrix could potentially be considered as an alternative dermal substitutes and wound healing material for skin tissue engineering applications.

The aim of this study was to prove the effectiveness of MatriDerm(®) combined with skin grafting versus skin grafting alone in post-traumatic wounds treatment. At the Department of Plastic and Reconstructive Surgery of the University of Rome Tor Vergata, we treated 60 patients: 30 patients with dermal substitutes (MatriDerm(®)) combined with autologous skin graft and 30 with skin graft alone. Two weeks after the first treatment, 95% of wounds treated with MatriDerm(®) and skin graft showed a re-epithelisation, whereas it was 75-80% in the control group. We used the Manchester Scar Scale (MSS) and patient's self-estimation scale to assess the outcomes. Mann-Whitney U test was performed for the five items of the MSS and the results were combined to those of patient's self-estimation scale and the re-epithelialisation percentage to test the significance between the two groups. These data confirm the evidence of the clinical use of MatriDerm(®) technology in the healing of soft tissue wounds and prove the effectiveness of combining MatriDerm(®) and skin grafting for the first time. Furthermore, we observed a percentage reduction of wound contraction and in the same time an improvement of elasticity, quality of scars tissue and dermal architecture.

As deep soft tissue defects with exposed bone, cartilage or tendons are not suitable for wound closure with skin mesh grafts, other techniques are needed. We report on six patients, one female and five males, aged between 32 and 89 years, and deep soft tissue defects with exposed tendons, cartilage or bone. The aetiology of these defects was vascular (n = 3), tumour surgery (2), and post-traumatic (1). Wounds were treated with a collagen-elastin matrix applied above the exposed structures. In five patients, the procedure was combined with mesh graft transplantation in the same setting. Follow-up varied between 12 and 40 weeks. Wound healing was uncomplicated in all transplanted patients until first dressing change after 7 days. All but one transplant showed a 100% take rate and the transplant was stable within 10-14 days. A complete wound closure was also achieved without transplantation, but this took 8 weeks. No adverse effects were noted. There was no skin contracture of the skin grafts. Collagen-elastin matrix with split-thickness skin grafts is a useful tool in deep soft tissue. The time to heal can be reduced.

Patients with extensive burns rely on the use of tissue engineered skin due to a lack of sufficient donor tissue, but it is a challenge to identify reliable and economical scaffold materials and donor cell sources for the generation of a functional skin substitute. The current review attempts to evaluate the performance of the wide range of biomaterials available for generating skin substitutes, including both natural biopolymers and synthetic polymers, in terms of tissue response and potential for use in the operating room. Natural biopolymers display an improved cell response, while synthetic polymers provide better control over chemical composition and mechanical properties. It is suggested that not one material meets all the requirements for a skin substitute. Rather, a composite scaffold fabricated from both natural and synthetic biomaterials may allow for the generation of skin substitutes that meet all clinical requirements including a tailored wound size and type, the degree of burn, the patient age, and the available preparation technique. This review aims to be a valuable directory for researchers in the field to find the optimal material or combination of materials based on their specific application.

Objectives: The purpose of this study was to evaluate the effectiveness of the acellular dermal matrix (ADM) as a membrane for guided bone regeneration (GBR), in comparison with a bioabsorbable membrane. Material and methods: In seven dogs, the mandibular pre-molars were extracted. After 8 weeks, one bone defect was surgically created bilaterally and the GBR was performed. Each side was randomly assigned to the control group (CG: bioabsorbable membrane made of glycolide and lactide copolymer) or the test group (TG: ADM as a membrane). Immediately following GBR, standardized digital X-ray radiographs were taken, and were repeated at 8 and 16 weeks post-operatively. Before the GBR and euthanasia, clinical measurements of the width and thickness of the keratinized tissue (WKT and TKT, respectively) were performed. One animal was excluded from the study due to complications in the TG during wound healing; therefore, six dogs remained in the sample. The dogs were sacrificed 16 weeks following GBR, and a histomorphometric analysis was performed. Area measurements of new tissue and new bone, and linear measurements of bone height were performed. Results: Post-operative healing of the CG was uneventful. In the TG membrane was exposed in two animals, and one of them was excluded from the sample. There were no statistically significant differences between the groups for any histomorphometric measurement. Clinically, both groups showed an increase in the TKT and a reduction in the WKT. Radiographically, an image suggestive of new bone formation could be observed in both groups at 8 and 16 weeks following GBR. Conclusion: ADM acted as a barrier in GBR, with clinical, radiographic and histomorphometric results similar to those obtained with the bioabsorbable membrane.

Aim: The aim of the present review was to systematically assess the dental literature in terms of soft tissue grafting techniques. The focused question was: is there superiority of one method over others for augmentation and stability of the augmented soft tissue in terms of increasing the width of keratinized tissue (part 1), and gain in soft tissue volume (part 2). Methods: A Medline search was performed for human studies focusing on augmentation of keratinized tissue and/or soft tissue volume, and complimented by additional hand searching. Relevant studies were identified and statistical results reported for meta-analyses including the test minus control weighted mean differences (WMD) with 95% confidence intervals (CI), the I-squared statistic for tests of heterogeneity, and the number of significant studies. Results: Twenty-five (part 1) and three (part 2) studies met the inclusion criteria; 14 studies (part 1) were eligible for comparison using meta-analyses. An apically positioned flap/vestibuloplasty (APF/V) procedure resulted in a statistically significantly greater gain in keratinized tissue than untreated controls. APF/V plus autogenous tissue revealed statistically significant more attached gingiva compared to untreated controls and a borderline statistical significance compared to APF/V plus allogenic tissue. Statistically significantly more shrinkage was observed for APF/V plus allogenic graft compared to APF/V plus autogenous tissue. Patient-centered outcomes did not reveal a superiority of any of the treatment methods regarding post-operative complications. The 3 studies reporting on soft tissue volume augmentation could not be compared due to lack of homogeneity. The use of subepithelial connective tissue grafts (SCTGs) resulted in statistically significantly more soft tissue volume gain compared to free gingival grafts (FGGs). Conclusions: APF/V is a successful treatment concept to increase the width of keratinized tissue or attached gingiva around teeth. The addition of autogenous tissue statistically significantly increases the width of attached gingiva. For soft tissue volume augmentation only limited data are available favoring SCTGs over FGG.

The purpose of this study was to validate supercritical carbon dioxide (SC-CO2) as a terminal sterilization method for biological materials, specifically acellular dermal matrix. In this study, bacterial spores, Bacillus atrophaeus, were inoculated onto porcine acellular dermal matrix to serve as a “worst case” challenge device. The inactivation of the spores by SC-CO2 with peracetic acid (PAA) sterilant was analyzed as a function of exposure times ranging from 1 to 30 min. A linear inactivation profile for the Bacillus atrophaeus spores was observed, and a SC-CO2 exposure time of 27 min was determined to achieve a sterility assurance level of 10−6. The inactivation of viruses was also studied using Encephalomyocarditis (EMC) viruses. After 15 min of exposure to SC-CO2 with PAA sterilant, more than a 6 log10 reduction was observed for EMC viruses. Biochemical and biomechanical evaluations showed that the SC-CO2 treatment with PAA sterilant did not cause significant changes in porcine acellular matrix's susceptibility to collagenase digestion, tensile or tear strength, indicating limited alteration of the tissue structure following SC-CO2 sterilization. © 2009 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 2009

Studies of skin graft behaviour in rodent excisional wound models are limited by the dominance of wound contracture and graft sloughing as primary healing responses. To slow skin contraction, polytetrafluoroethylene (Teflon) rings were inserted into dorso-lateral full-thickness wounds in SCID mice. Cultured skin substitutes (OrCel), composed of cultured human keratinocytes and fibroblasts in a bovine collagen sponge, were implanted within the rings. Examination and histology of grafts 14 days later showed graft take in four of six recipients, with 90% epithelialization and wound contraction of 31-47%. Immunohistochemical studies, using human-specific antisera to distinguish graft from host tissues, showed that regenerated tissue was predominantly human. Staining with anticytokeratin, revealed a multilayered, stratified neoepidermis. HBG were identified in keratinocytes in all epidermal layers. Langerhans cells were absent. Antihuman vimentin, used as a fibroblast marker, confirmed that cells of the neodermis were primarily of human origin. Neoepidermal keratinocytes, primarily in the basal and suprabasal layers, were also stained. Results suggest that the poly(tetrafluoroethylene) ring inhibited graft sloughing and provided a more favourable environment for the skin substitute to regenerate a substantially normal human skin.