Clinical evaluation of a new bilayer "artificial skin" composed of collagen sponge and silicone layer

Commercialization of skin substitutes for third-degree burn wounds

Technological advances have increasingly provided more and better treatment options for patients with severe burns. Here, we provide a bird's-eye view of the product development process for third-degree burn wounds with considerations of the critical interaction with regulatory bodies, existing technological gaps, and future directions for skin substitutes.

Biomimetic Electronic Skin through Hierarchical Polymer Structural Design

Human skin comprises multiple hierarchical layers that perform various functions such as protection, sensing, and structural support. Developing electronic skin (E-skin) with similar properties has broad implications in health monitoring, prosthetics, and soft robotics. While previous efforts have predominantly concentrated on sensory capabilities, this study introduces a hierarchical polymer system that not only structurally resembles the epidermis-dermis bilayer structure of skin but also encompasses sensing functions. The system comprises a polymeric hydrogel, representing the "dermis", and a superimposed nanoporous polymer film, forming the "epidermis". Within the film, interconnected nanoparticles mimic the arrangement of interlocked corneocytes within the epidermis. The fabrication process employs a robust in situ interfacial precipitation polymerization of specific water-soluble monomers that become insoluble during polymerization. This process yields a hybrid layer establishing a durable interface between the film and hydrogel. Beyond the structural mimicry, this hierarchical structure offers functionalities resembling human skin, which includes (1) water loss protection of hydrogel by tailoring the hydrophobicity of the upper polymer film; (2) tactile sensing capability via self-powered triboelectric nanogenerators; (3) built-in gold nanowire-based resistive sensor toward temperature and pressure sensing. This hierarchical polymeric approach represents a potent strategy to replicate both the structure and functions of human skin in synthetic designs.

A potential bilayer skin substitute based on electrospun silk-elastin-like protein nanofiber membrane covered with bacterial cellulose

Skin substitutes are designed to promote wound healing by replacing extracellular matrix. Silk-elastin-like protein is a renewable extracellular matrix-like material that integrated the advantages of silk and elastin-like protein. In this study, electrospun silk-elastin-like protein (SELP) nanofiber membrane covered with bacterial cellulose (BC) was created as a potential skin substitute to mimic gradient structure of epidermis and dermis of skin. The two layers were glued together using adhesive SELP containing 3,4-dihydroxyphenylalanine (DOPA) converted from tyrosine by tyrosinase. Skin topical drugs commonly used in clinical practice can penetrate through the SELP/BC barrier, and the rate of penetration is proportional to drug concentration. BC with dense fibrous structure can act as a barrier to preserve the inner SELP layer and prevent bacterial invasion, with a blocking permeation efficiency over 99% against four species of bacteria. Cell experiments demonstrated that the reticular fibers of SELP could provide an appropriate growth environment for skin cells proliferation and adhesion, which is considered to promote tissue repair and regeneration. The promising results support this strategy to fabricate a silk-elastin-like protein-based biomaterial for skin substitutes in the clinical treatment of full skin injuries and ulcers.

Oxygen transmission rates of skin substitutes and graft survival

AIM

Oxygen is required for cell migration into the scaffold and for the survival of the overlying graft in the use of a single-layer scaffold. In the absence of diffusion from the avascular wound base, such as in areas above the bone/tendon, oxygen delivery from the lateral edges of the scaffold is important. This study compared the oxygen permeability of skin scaffolds, currently commercially available in Turkey (Nevelia®, MatriDerm®, and Pelnac®), in the lateral plane.

MATERIALS AND METHODS

To measure oxygen permeability, an interconnected closed system was created. Oxygen permeability was evaluated based on the color change that occurred as a result of the reaction of iron with oxygen. After the dermal matrices placed in the closed system were exposed to oxygen, the color change on the surface of the dermal matrices was measured, and electron microscopic images were recorded to compare deformation before and after the procedure.

RESULTS

Two scaffolds did not show deformation after the procedure while Pelnac® had minimal deformation. The oxygen rates on the nitrogen side of the test apparatus were found to be 29%, 34%, and 27% for Nevelia®, MatriDerm®, and Pelnac®, respectively; and the oxygen transmission lengths (length of color change) of these scaffolds in the lateral plane were 1, 2, and 0.5 cm, respectively.

CONCLUSION

Although none of the scaffolds showed significant deformation, and all continued to exhibit their scaffold properties after the procedure, MatriDerm® was determined to be the most suitable scaffold for use in avascular areas, with a 2-cm oxygen transmission length in terms of lateral oxygenation.

The Bridging Effect of Artificial Dermis on Reconstruction of Skin Avulsion Injury

Skin avulsion wounds are expected to be swollen and tense after trauma, and skin perfusion can be compromised after primary closure, resulting in wound dehiscence and poor healing. The artificial dermis (AD) serves as a dermal regeneration template that is used to heal skin defects with secondary intention. Therefore, the aim of this study is to evaluate the effect of AD application on traumatic skin avulsion injuries compared to conventional primary closure. A retrospective cohort of 20 patients with skin avulsion injuries were included the study: ten patients were treated with AD and ten patients were managed with primary closure. When compared to the primary closure group, AD group had a shorter average healing time (58.40 ± 26.94 days V 65.50 ± 46.45 days) and significantly higher flap viability (92.00 ± 13.17% V 78.00 ± 13.98%; p = .03). In conclusion, AD is a promising material for the treatment of skin avulsion injury and produces better clinical results.

Skin grafting treatment of adolescent lower limb avulsion injury

Background

Under the influence of various factors, the number of lower extremity avulsion injuries in adolescents is increasing year by year. The main modality of treatment is skin grafting. There are many types of skin grafting. Although many studies on skin grafting after avulsion injuries have been published in the past few decades, there are differences in the treatment options for adolescents with post avulsion injuries.

Main body

Thorough debridement and appropriate skin grafts are essential for the surgical management of avulsion injuries for optimal prognosis. In the acquisition of grafts, progress has been made in equipment for how to obtain different depths of skin. The severity of the avulsion injury varies among patients on admission, and therefore the manner and type of skin grafting will vary. Especially in adolescents, graft survival and functional recovery are of great concern to both patients and physicians. Therefore, many efforts have been made to improve survival rate and activity.

Conclusion

This review summarizes the principles of treatment of avulsion injuries, the historical development of skin grafts, and the selection of skin grafts, hoping to be helpful for future research.

Novel application of absorbable gelatine sponge combined with polyurethane film for dermal reconstruction of wounds with bone or tendon exposure

Trauma, burns, and diabetes result in nonhealing wounds that can cause bone or tendon exposure, a significant health threat. The use of an artificial regeneration template combined with skin grafting as an alternative method to highly invasive flap surgery has been shown to be an effective way to cover full-thickness skin defects with bone or tendon exposure for both functional and aesthetic recovery. However, artificial regeneration templates, such as Pelnac, are overwhelmingly expensive, limiting their clinical use. Here, we demonstrate for the first time that polyurethane film combined with absorbable gelatine sponge, affordable materials widely used for haemostasis, are effective for dermal reconstruction in wounds with bone or tendon exposure. The absorbable gelatine sponge combined with polyurethane film was applied to eight patients, all resulting in adequate granulation that fully covered the exposed bone or tendon. The outcome of absorbable gelatine sponge combined with polyurethane film application indicates that this approach is a potential novel and cost-effective dermal reconstruction strategy for the treatment of severe wounds with bone or tendon exposure.

Use of Porcine-Derived Dermal Substitutes for Treatment of Nonhealing Vascular Leg Ulcers: A Case Series

Nonhealing leg ulcers are a major health problem worldwide with a high economic burden since they require human and material resources. Moreover, nonhealing ulcers are a major nontraumatic cause of lower limb amputations. Dermal substitutes have emerged as an effective therapeutic option for treatment of skin lesions, but data on leg ulcers are scarce. We evaluated safety and efficacy of a porcine-derived dermal substitute in the treatment of chronic vascular leg ulcers. Records of patients with nonhealing ulcers seen at our unit from 2018 to 2019 were retrospectively reviewed. Wound etiology, wound area, and complications were evaluated. Each patient received one application of porcine-derived dermal substitute and was followed-up. Six patients (5 females and 1 male) with a mean age of 61.3 (52-81) years presented with nonhealing leg ulcers. After surgical debridement and wound bed preparation, porcine-derived dermal substitute was applied onto the ulcer. Granulation was satisfactory within 10 days. All wounds healed after an average time of 14 weeks. Graft take was good, and no graft loss, rejection, or associated infection were observed. In conclusion, the data presented indicate that dermal substitutes are safe and effective for treatment of chronic nonhealing vascular leg ulcers.

Pelnac® Artificial Dermis Assisted by VSD for Treatment of Complex Wound with Bone/Tendon Exposed at the Foot and Ankle, A Prospective Study

Purpose: This study aims to assess the efficacy and safety of Pelnac dermal regeneration template assisted by vacuum sealing drainage (VSD) and a split-thickness skin graft to cover the large skin and soft-tissue defects at foot and ankle. Methods: This study began from March 2013, up to February 2017. A total of 16 patients met the inclusion and exclusion criteria and were included. For every patient, 2 separate operations were performed, the first being thorough debridement of necrotic tissues immediate coverage of VSD at continuous negative pressure suction, and the second being the autologous split-thickness skin graft. At each follow-up, relevant data were documented. Results: The average follow-up was 16.5 months (range, 12 to 42 months). No infections, hematoma, or seroma were observed. 13 out of 16 patients had a complete skin graft "take" (100%). Patients' satisfaction of esthetic appearance was 76.5 ± 5.2/100. The VSS value was 2.2 ± 2.1, representing a good result. Regarding the sensory recovery, the response "normal or near normal" could be obtained in 14/16 patients. Mean AROM for extension/flexion of the ankle was 48.5 ± 4.8° (range 35-62°), and 93.7% (15/16) of patient could obtain a satisfying functional result. Conclusions: Our report indicated Pelnac provided an effective method for management of complex wounds with underlying bone or tendons exposed.

The surgical strategy of Purpura fulminans triggered by pyothorax associated with lung cancer

Purpura fulminans is a rare disease that usually causes sepsis and is accompanied by disseminated intravascular coagulation and symmetric gangrene of distal extremities. We had to consider the most appropriate surgery approach. The most important point was attempting to rescue the patient’s ability to walk under his own power.

The use of dermal regeneration template for treatment of complex wound with bone/tendon exposed at the forearm and hand, a prospective cohort study

The purpose of this study was to assess the efficacy and safety of Pelnac and split-thickness skin graft for management of complex wound with underlying bone/tendon exposure at forearm and hand.This is a prospective study, beginning from March 2013 up to May 2017. There were 13 patients, with age of 31.2 years. All of them underwent the staged Pelnac and split-thickness skin graft to manage the complex wound with bone/tendon. Postoperatively, scheduled follow-up was conducted.The average follow-up was 15 months. There were no infections, wound necrosis, hematoma, or seroma during the phase when Pelnac was applied. There was 100% "take" of the Pelnac in 12/13 patients. In 11 patients, there was complete skin graft "take". Patients' satisfaction for the esthetic appearance of the grafted area was 75.0 ± 8.5/100. The VSS value was 2.9 ± 2.5. Regarding the sensory recovery, the response of "normal or near normal" could be obtained in 7/13 patients, "slight loss" in 5 patients and "significant loss" in 1 case. The average DASH score was 27.2 ± 18.5, and most patients (12/13) could obtain an acceptable ability to perform the daily activities.Pelnac dermal template is a favorable alternative to flap reconstruction in the treatment of complex wound with underlying tissues exposure.

Biomimetic In Vitro Model of Cell Infiltration into Skin Scaffolds for Pre-Screening and Testing of Biomaterial-Based Therapies

Due to great clinical need, research where different biomaterials are tested as 3D scaffolds for skin tissue engineering has increased. In vitro studies use a cell suspension that is simply pipetted onto the material and cultured until the cells migrate and proliferate within the 3D scaffold, which does not mimic the in vivo reality. Our aim was to engineer a novel biomimetic in vitro model that mimics the natural cell infiltration process occurring in wound healing, thus offering a realistic approach when pre-screening and testing new skin substitutes. Our model consists of porous membrane cell culture inserts coated with gelatin and seeded with human dermal fibroblasts, inside which two different commercially available dermal substitutes were placed. Several features relevant to the wound healing process (matrix contraction, cell infiltration and proliferation, integration of the biomaterial with the surrounding tissue, and secretion of exogenous cytokines and growth factors) were evaluated. Our results showed that cells spontaneously infiltrate the materials and that our engineered model is able to induce and detect subtle differences between different biomaterials. The model allows for room for improvements or "adds-on" and miniaturization and can contribute to the development of functional and efficient skin substitutes for burns and chronic wounds.

Revision surgery with dermal regeneration template and vacuum sealing drainage for reconstruction of complex wounds following necrosis of reattached avulsed skins in a degloving injury: A case report

RATIONALE

Degloving injury of the upper limb often extends to underlying tendons and bone, which is at high risk of treatment failure if only simple reattachment of defatted avulsed skins was performed. Pelnac dermal regeneration template could be used as a treatment choice for necrosis of the reattached avulsed skins in a degloving injury.

PATIENT CONCERNS

A 48-year-old woman with a degloving injury of the right forearm, wrist, and hand received initial treatment by reattachment of the defatted avulsed skins over the wound bed. However, 17 days postoperatively, the reattached skins developed complete necrosis, leaving large size of tissue defects and tendon/bone exposure.

DIAGNOSIS

Failure to reconstruct the skin and soft-tissue envelop by reattachment of the defatted avulsed skins in a severe degloving injury of the upper limb.

INTERVENTIONS

We decided to use a 2-stage procedure of Pelnac dermal regeneration template and secondary skin graft to solve this issue, in consideration of these conditions and the patient' demanding of limb function and aesthetic appearance.

OUTCOMES

At the final follow-up, this patient obtained an excellent result, in term of scar quality, aesthetic appearance, and the ability to perform the daily activities.

LESSONS

We believe this could become an interesting option in patients who needed revision procedure for management of complex wounds with tendon/bone exposure following the necrosis of reattached skins in degloving injuries.

Preparation of gelatin hydrogel sponges incorporating bioactive glasses capable for the controlled release of fibroblast growth factor-2

Gelatin hydrogel sponges incorporating bioactive glasses (Gel-BG) were fabricated. We evaluated the characteristics of Gel-BG as scaffolds from the perspective of their mechanical properties and the formation of hydroxyapatite by the incorporation of bioactive glasses (BG). In addition, the Gel-BG degradation and the profile of fibroblast growth factor-2 (FGF-2) release from the Gel-BG were examined. Every Gel-BG showed an interconnected pore structure with the pore size range of 180-200 µm. The compression modulus of sponges incorporating BG increased. The time profiles of degradation for the 72-h crosslinked gelatin hydrogel sponges incorporating 10 wt% BG (Gel-BG(10)) and 50 wt% BG (Gel-BG(50)) were analogous to that of the 24-h crosslinked gelatin hydrogel sponge without BG (Gel-BG(0)). In measuring the release of FGF-2 from Gel-BG, the Gel-BG(10) and Gel-BG(50) showed almost analogous 100% cumulative release within 28 days in vivo. Additionally, a bioactivity evaluation showed that the presence of gelatin does not affect the in vitro bioactivity of Gel-BG. These sponges showed mechanical and chemical functionality as scaffolds, featuring both the controlled release of FGF-2 and the induction of hydroxyapatite crystallization.

Soft and Flexible Bilayer Thermoplastic Polyurethane Foam for Development of Bioinspired Artificial Skin

Inspired by the epidermis-dermis composition of human skin, here we have simply developed a lightweight, robust, flexible, and biocompatible single-electrode triboelectric nanogenerator (S-TENG)-based prototype of bilayer artificial skin, by attaching one induction electrode with unfoamed skin layer of microcellular thermoplastic polyurethane (TPU) foam, which shows high-performance object manipulation [by responding differently toward different objects, viz., aluminum foil, balloon, cotton glove, human finger, glass, rubber glove, artificial leather, polyimide, poly(tetrafluoroethylene) (PTFE), paper, and wood], due to electrification and electrostatic induction during contact with the objects having different chemical functionalities. Comparative foaming behavior of ecofriendly supercritical fluids, viz., CO₂ over N₂ under variable temperatures (e.g., 130 and 150 °C) and constant pressure (15 MPa), have been examined here to pursue the soft and flexible triboelectric TPU foam. The foam derived by CO₂ foaming at 150 °C has been prioritized for development of S-TENG. Foam derived by CO₂ foaming at 130 °C did not respond as well due to the smaller cell size, higher hardness, and thicker skin. Inflexible N₂-derived foam was not considered for S-TENG fabrication. Object manipulation performance has been visualized by principal component analysis (PCA), which shows good discrimination among responses to different objects.

The use of artificial dermis for corrective surgery on burn scars

Background

Hypertrophic scarring from burn injuries on large skin areas is of great concern for both patients and attending physicians because of significant functional and cosmetic impairment. Surgery for scar corrections is challenging because of limitations on the availability of normal tissue. An alternative method for scar correction using artificial dermis is now possible. Artificial dermis can be used in the reconstruction of scars, burn injuries on large skin areas and in patients who do not have sufficient donor sites for skin grafts after scar excisions.

Objective

To report the efficacy of artificial dermis on a 20 years old Thai man with severe scar contracture from burn injuries.

Method

An open-label case study, the severe contracture case underwent scar excision and was applied with artificial dermis.

Result

A 20-year-old man had severe scar contractures on his left arm, forearm, and elbow, and a shearing wound with a scar at his left elbow. Total scar excision was done on his left arm, forearm, elbow, and hand, and then followed by application of artificial dermis on to the wounds. After 2 weeks, neodermis formation was observed, after which an ultrathin split thickness skin graft was applied to the wounds. One month after sugery, the patient could extend his left elbow fully and the cosmetic result is satisfactory.

Conclusion

Use of artificial dermis should be a new alternative modality in improving our strategy in correcting scar issues from burn injuries, especially on large burn scar areas with limited donor sites for skin grafts.

Experimental Wound Dressing by Heterologous Collagen: A Morphological-Quantitative Approach

The use of heterologous collagen in skin repair processes has proved to be an efficacious approach for the reconstitution of injured tissue. A morphological and quantitative evaluation of the reactive and reparative ca pacity of injured tissue treated either with conventional medications or with heterologous collagen (Condress) in the form of sponges was carried out. We have analyzed experimental surgical lesions on an animal model and evalu ated the repair processes of the lesions, including the excision of the cutaneous and subcutaneous tissue. The heterologous collagen sponges provided biologi cal support to obtain healed skin of better quality. Tissue lesions healed more rapidly, thus reducing the risk of recurrence. This experimental study provides morphological and structural data for further investigation.

Allogeneic Transplantation of an Adipose-Derived Stem Cell Sheet Combined With Artificial Skin Accelerates Wound Healing in a Rat Wound Model of Type 2 Diabetes and Obesity

One of the most common complications of diabetes is diabetic foot ulcer. Diabetic ulcers do not heal easily due to diabetic neuropathy and reduced blood flow, and nonhealing ulcers may progress to gangrene, which necessitates amputation of the patient's foot. This study attempted to develop a new cell-based therapy for nonhealing diabetic ulcers using a full-thickness skin defect in a rat model of type 2 diabetes and obesity. Allogeneic adipose-derived stem cells (ASCs) were harvested from the inguinal fat of normal rats, and ASC sheets were created using cell sheet technology and transplanted into full-thickness skin defects in Zucker diabetic fatty rats. The results indicate that the transplantation of ASC sheets combined with artificial skin accelerated wound healing and vascularization, with significant differences observed 2 weeks after treatment. The ASC sheets secreted large amounts of several angiogenic growth factors in vitro, and transplanted ASCs were observed in perivascular regions and incorporated into the newly constructed vessel structures in vivo. These results suggest that ASC sheets accelerate wound healing both directly and indirectly in this diabetic wound-healing model. In conclusion, allogeneic ASC sheets exhibit potential as a new therapeutic strategy for the treatment of diabetic ulcers.

Effects of mature adipocyte-derived dedifferentiated fat (DFAT) cells on generation and vascularisation of dermis-like tissue after artificial dermis grafting

Although artificial dermis (AD) is effective for skin reconstruction, it requires two separate procedures, because the AD must be vascularised before skin grafts. To shorten the period of the dermis-like tissue generation before the secondary skin grafting must be beneficial. Dedifferentiated fat (DFAT) cells are isolated from mature adipose cell suspensions and have potential to differentiate into multiple cell types including endothelial cells. This study aimed to investigate effects of DFAT cells on dermal regeneration after AD grafts in rats. The effects of combination use of DFAT cells and basic fibroblast growth factor (bFGF) were also tested to mimic clinical situations. DFAT cells were isolated from SD rats. Full-thickness wounds were created on the back of rats followed by AD grafting. Five groups were established; Group I: control, Group II: treated with DFAT cells, Group III: treated with bFGF, Group IV: treated with both of DFAT cells and bFGF, and Group V: treated with Green fluorescent protein (GFP)-labelled DFAT cells and bFGF. Histological evaluation was serially performed. Group IV showed markedly promoted vascularisation of dermis-like tissue. In particular, capillary infiltration into the dermis was obtained within 2 days. Immunohistochemical examination revealed that the transplanted DFAT cells had differentiated into endothelial cells and participated in angiogenesis. Group IV also showed a marked increase in the thickness of the dermis like tissue. The present results suggest that the use of DFAT cells under bFGF treatment could be beneficial to shorten the period required for dermal regeneration and vascularisation and contribute to use AD more effectively and safely.

The treatment of bone exposure in burns by using artificial dermis

BACKGROUND

The treatment of bone-exposed wounds with artificial dermis is not widely accepted in burn patients because of uncertain clinical results. This article aimed to review our clinical experience with this technique.

METHODS

We implanted artificial dermis in 11 bone-exposed burns. Implantation was directly performed on bones with periosteum, whereas bones without periosteum were trephinated or burred before implantation. All wounds were closed by secondary skin grafting.

RESULTS

The mean patient age was 49 years. Lower extremity is the most common site of bone exposure. The mean bone exposed area was 55.6 cm, whereas the mean Integra-implanted area was 86.7 cm. The overall implant take rate was 91%, and the skin grafting success rate was 80%. No secondary breakdown was noted after a 2-year follow-up.

CONCLUSIONS

This study confirms that artificial dermis can be an alternative treatment tool for burns with exposed bones, especially in patients with limited donor sites.

Treating a collagen scaffold with a low concentration of nicotine promoted angiogenesis and wound healing

BACKGROUND

Nicotine, one of the major pharmacologically active agents of cigarette smoke, has various effects on cell proliferation, and it has recently been reported to have angiogenic effects. In our previous study, we showed that the topical administration of nicotine at a low concentration accelerated wound healing. This study aimed to evaluate the efficacy of nicotine and synergistic effects of combination treatment with nicotine and basic fibroblast growth factor (bFGF) in a murine excisional wound model treated with artificial dermis.

METHODS

Full-thickness defects (8 mm in diameter) were created on the backs of mice, and artificial dermis was sutured to the defects. Phosphate-buffered saline (10 μL), nicotine (10(-3), 10(-4), or 10(-5) M), bFGF (0.5 μg), and both bFGF and 10(-4) M nicotine were topically administered to the artificial dermal tissue for 7 d. The mice were killed on day 14, and the wound area, neoepithelium length, and area of newly formed capillaries in the artificial dermis were evaluated.

RESULTS

The wound areas treated with 10(-4) M nicotine, bFGF, or bFGF plus 10(-4) M nicotine were significantly smaller than those in the control group. In these three groups, the neoepithelium in the bFGF plus 10(-4) M nicotine group was significantly longer than that in the other groups. There was no significant difference between the neoepithelium lengths of the control and 10(-5) M nicotine groups. The 10(-3) M nicotine group displayed the least re-epithelization among the groups.

CONCLUSIONS

In this study, 10(-4) M nicotine induced angiogenesis in, and accelerated the healing of, wounds treated with artificial dermis. bFGF and nicotine had synergistic effects, and the combined use of nicotine and bFGF is an effective wound healing method.

Secreted frizzled related protein 4 reduces fibrosis scar size and ameliorates cardiac function after ischemic injury

Expression of the Wnt modulator secreted frizzled related protein 4 (Sfrp4) is upregulated after heart ischemic injury. We show that intramuscular administration of recombinant Sfrp4 to rat heart ischemic injury and recanalization models prevents further deterioration of cardiac function after the ischemic injury. The effect of Sfrp4 persisted for at least 20 weeks when Sfrp4 was administered in a slow release system (Sfrp4-polyhedra) to both acute and subacute ischemic models. The histology of the dissected heart showed that the cardiac wall was thicker and the area of acellular scarring was smaller in Sfrp4-treated hearts than in controls. Increased amounts of both the inactive serine 9-phosphorylated form of glycogen synthase kinase (GSK)-3β and the active form of β-catenin were observed by immunohistology 3 days after lateral anterior descendant ligation in control, but not in Sfrp4-treated hearts. All together, we show that administration of Sfrp4 interferes with canonical Wnt signaling that could mediate the formation of acellular scar and consequently contributes to the prevention of aggravation of cardiac function.

Management of wounds with exposed bone structures using an artificial dermis and skin grafting technique

The task of managing an open wound complicated by exposed bony structures underneath is difficult, if not challenging. We have instituted a method of managing the problems in stages using an artificial dermis and skin grafting technique in 17 wounds in 15 individuals from Sept. 2006 to Feb. 2009. While all wounds were noted to assume aberrant healing processes, the majority of involved bony structures were devoid of periosteal covering compounded by various degrees of infection. Of 15 incidents, mechanical trauma was responsible for 10, chemical burns for two and electrical burns for two patients. A chronic non-healing ulcer with exposed bone formed in an old burn scar accounted for the remaining one. The regimen of surgical management consisted of initial debridement, the coverage of the resultant wound with an artificial dermis and a partial-thickness skin grafted over this dermis-like structure grown with granulation tissues. Complete wound healing was attained in 15 out of 17 with outstanding cosmetic and minimal donor-site morbidity. Despite initial failure encountered in two, the morbidities noted were low. It is especially useful in large defects that usually require flaps for coverage.

Preparation of collagen/gelatin sponge scaffold for sustained release of bFGF

Artificial dermis (AD) has been used to regenerate dermis-like tissues in the treatment of full-thickness skin defects, but it takes 2 or 3 weeks to complete dermal regeneration. Our previous study demonstrated that injection of basic fibroblast growth factor (bFGF)-impregnated gelatin microspheres (MS) into the AD accelerates the regeneration of dermis-like tissue. However, injection of gelatin MS before clinical use is complicated and time consuming. This study investigated a new scaffold, in which collagen and gelatin are integrated, and which is capable of sustained bFGF release. We produced collagen/gelatin sponges with a gelatin concentration of 0wt%, 10wt%, 30wt%, and 50wt%. The mean pore size in each sponge decreased with the gelatin concentration. In an in vitro study, proliferation of fibroblasts in each sponge was not significantly different over 7 days of culture. As for in vivo sustained release of bFGF, a radioisotope study demonstrated that retention of bFGF in gelatin 10wt% and 30wt% sponges was significantly larger than that in gelatin 0wt% sponge. The collagen/gelatin sponges were grafted on full-thickness skin defects created on a rabbit ear, and we evaluated regeneration of dermis-like tissue by measuring the amount of hemoglobin and size of dermis-like tissue on histological sections. Seven days after implantation, the amount of hemoglobin in dermis-like tissue in gelatin 10wt% sponge was significantly larger than those in control and gelatin 50wt% sponge. Twenty-eight days after implantation, the area of dermis-like tissue in gelatin 10wt% sponge was significantly larger than those in the other specimens. We conclude that the collagen sponge integrated with 10wt% gelatin has the most potential for sustained release of bFGF and that the combination of collagen/gelatin 10wt% sponge and bFGF is a promising therapeutic modality for the treatment of full-thickness skin defects.

Recovery Course of Full-Thickness Skin Defects With Exposed Bone: An Evaluation by a Quantitative Examination of New Blood Vessels

BACKGROUND

Full-thickness skin defects with exposed bone are often hard to heal. The lack or delayed re-vascularization is considered one of the major causes, and the periosteum is also suggested to have an important role in tissue regeneration.

MATERIALS AND METHODS

Full-thickness skin defect wounds with exposed bone were made in the parietal region of Wister rats. The periosteum of the exposed parietal bone was removed in the periosteum-lacking group, but maintained in the control group (periosteum-intact group). The wound was covered by an artificial dermis made of collagen. The wound healing process was histologically compared. Double immunostaining of alpha-smooth muscle actin (SMA) and von Willebrand factor (vWF) was used for re-vascularization examination, and the blood vessel density in the artificial dermis was quantified.

RESULTS

The density of the blood vessels in the uninjured parietal tissue was approximately 80 vessels/mm(2). To reach this density, 7 and 21 days were required for the control (periosteum-intact) and the periosteum-lacking groups, respectively. This coincided with complete revascularization, fibroblast migration and the reentry of blood vessels to the upper layer of the wound were observed.

CONCLUSION

The described results support the importance of the periosteum in the full-thickness skin defect healing process.

Novel application method of artificial dermis: One-step grafting procedure of artificial dermis and skin, rat experimental study

BACKGROUND

Currently, to treat skin defects with artificial dermis (AD), two surgical procedures where the artificial dermis grafting and another secondary skin grafting are required. The purpose of this study was to achieve simultaneous grafting of the artificial dermis and the split-skin. To enhance the wound angiogenesis, cultured endothelial cells, fibroblasts and PDWHF (platelet derived wound healing factor) were employed.

METHODS

The experiment consists of following two parts: (1) Investigation to obtain faster angiogenesis into the bilayer artificial dermis: full-thickness wounds created on the back of the rats were treated with the artificial dermis (Terudermis, with silicone sheet, TERUMO Co., Japan). Prior to the artificial dermis grafting, following four groups were established; control group (AD alone, n=6), PDWHF group (AD treated with PDWHF, n=6), cultured cells group (AD treated with cultured endothelial cells and fibroblasts, n=6), combination group (AD treated with PDWHF and cultured cells, n=6). (2) Trial of one-stage grafting of the AD and the skin: simultaneous grafting of the artificial dermis and skin was performed using the same rat model. Before making skin defects, split thickness skin were harvested. Then the skin grafting was carried out immediately after the AD grafting. To allow grafting of the skin onto the artificial dermis, the AD without silicone sheet (Terudermis without silicone sheet, TERUMO Co., Japan) were used. Two groups, control group (AD alone, n=3) and treatment group (AD with PDWF and cultures, n=3) were established.

RESULTS

(1) When the artificial dermis were treated with PDWHF, cultured endothelial cells and fibroblasts, vascular invasion into the artificial dermis was observed 5 days after the surgery. (2) In the treatment group, the skin grafted immediately after the artificial dermis grafting was completely taken.

CONCLUSIONS

The present study revealed that treatment with PDWHF, combined with cultured endothelial cells and fibroblasts, accelerated wound angiogenesis. By this method, one-step grafting procedure of the artificial dermis and the skin is possible.

Lower extremity reconstruction after necrotising fasciitis and necrotic skin lesions using a porcine-derived skin substitute

Seven consecutive clinical cases of necrotising fasciitis or necrotic skin lesions (42-78 years old; average 65.0 years of age, three females and four males) due to group A Streptococcus, group B Streptococcus, methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa in the lower extremities, who demonstrated rapid systemic symptoms, were investigated for the usefulness of a bilayer artificial dermis, derived from porcine tendons, over 4 +/- 2.4 years (1-7 years). All surgical debridement was confirmed as sufficiently deep and wide for clinically infected lesions and artificial dermis was applied to all wounds. The average interval to secondary split-thickness skin grafting was about 17.5 days (17.5 +/- 2.44 days, 21 days max., 14 days min.) and the average thickness was 0.009 +/- 0.0022 in. (range: 0.006 - 0.012 in.). No clinical problems were noted during the application of the artificial dermis and the subsequent skin grafting. Since, the donated skin graft was thin, the morbidity was minimised. The use of artificial dermis after extensive surgical debridement in necrotising fasciitis was easy and effective. Local or systemic infection was negligible.

Regulation of cellular infiltration into tissue engineering scaffolds composed of submicron diameter fibrils produced by electrospinning

We characterize the infiltration of interstitial cells into tissue engineering scaffolds prepared with electrospun collagen, electrospun gelatin, electrospun poly(glycolic) acid (PGA), electrospun poly(lactic) acid (PLA), and an electrospun PGA/PLA co-polymer. Electrospinning conditions were optimized to produce non-woven tissue engineering scaffolds composed of individual fibrils less than 1000 nm in diameter. Each of these materials was then electrospun into a cylindrical construct with a 2 mm inside diameter with a wall thickness of 200-250 microm. Electrospun scaffolds of collagen were rapidly, and densely, infiltrated by interstitial and endothelial cells when implanted into the interstitial space of the rat vastus lateralis muscle. Functional blood vessels were evident within 7 days. In contrast, implants composed of electrospun gelatin or the bio-resorbable synthetic polymers were not infiltrated to any great extent and induced fibrosis. Our data suggests that topographical features, unique to the electrospun collagen fibril, promote cell migration and capillary formation.

Osteogenic differentiation of mesenchymal stem cells in biodegradable sponges composed of gelatin and β-tricalcium phosphate

Biodegradable gelatin sponges incorporating various amounts of beta-tricalcium phosphate (betaTCP) (gelatin-betaTCP) were fabricated and the in vitro osteogenic differentiation of mesenchymal stem cells (MSC) isolated from the rat bone marrow in the sponges was investigated. The gelatin sponges incorporating betaTCP have an interconnected pore structure with the average size of 180-200 microm, irrespective of the betaTCP amount. The stiffness of the sponges became higher with an increase in the amount of betaTCP. When seeded into the sponges by an agitated method, MSC were homogeneously distributed throughout the sponge. The morphology of cells attached got more spreaded with the increased betaTCP amount. The rate of MSC proliferation depended on the betaTCP amount and culture method: the higher the betaTCP amount in the stirring culture, the higher the proliferation rate. The deformed extent of gelatin-betaTCP sponges was suppressed with the increased amount of betaTCP. When measured to evaluate the osteogenic differentiation of MSC, the alkaline phosphatase activity and osteocalcin content became maximum for the sponge with a betaTCP amount of 50 wt%, although both the values were significantly high in the stirring culture compared with those in the static culture. We concluded that the attachment, proliferation, and osteogenic differentiation of MSC were influenced by sponge composition of gelatin and betaTCP as the cell scaffold.

Viability and Function of Autologous and Allogeneic Fibroblasts Seeded in Dermal Substitutes after Implantation

BACKGROUND

Fibroblast-seeded collagen sponges have been used for the treatment of skin defects and skin ulcers. However, the viability of the fibroblasts after implantation is still unknown. The objective of this study was to investigate the viability and distribution of autologous and allogeneic fibroblasts after implantation and to clarify which type is more effective for wound healing.

MATERIALS AND METHODS

Skin samples of Hartley guinea pigs were retrieved and autologous fibroblasts were isolated and cultured. Fibroblasts isolated from the skin of a Strain2 guinea pig were used as allogeneic fibroblasts. Three full-thickness wounds were created on the backs of guinea pigs and an acellular collagen sponge, a collagen sponge seeded with autologous fibroblasts, and a collagen sponge seeded with allogeneic fibroblasts were transplanted. Before implantation, fibroblasts were labeled with PKH26. The guinea pigs were sacrificed 1, 2, and 3 weeks after implantation. The epithelization and contraction of the wounds were assessed, and the viability and distribution of the seeded fibroblasts were observed in cross sections.

RESULTS

Three weeks after implantation, the PKH26-labeled autologous and allogeneic fibroblasts remained viable. In the wounds covered with the autologous fibroblast-seeded collagen sponge, the epithelization was fastest, and the percent wound contraction was smallest. In contrast, in the wounds covered with allogeneic fibroblasts, the epithelization was slowest and the percent contraction was largest.

CONCLUSION

The allogeneic fibroblasts seeded in the collagen sponge survived and remained viable on the grafted area, but did not accelerate wound healing.

Leukemia inhibitory factor-transfected embryonic fibroblasts and vascular endothelial growth factor successfully improve the skin substitute wound healing by increasing angiogenesis and matrix production

BACKGROUND AND OBJECTIVE

The combined application of cytokines on embryonic fibroblasts and dermal substitute were studied for optimal skin defect coverage. The mechanism of combined treatment of leukemia inhibitory factor (LIF)-transfected embryonic fibroblasts and vascular endothelial growth factor (VEGF) were elucidated and subsequently the in vivo applications of both were tested in an artificial dermal substitute.

METHODS

Mouse embryonic fibroblast cells, BALB-3T3, were stably transfected with mouse full-length LIF cDNA and added to various doses of VEGF for detection of signaling interaction. LIF-transfected cells and VEGF treatment were tested with pig-tendon derived collagen dermal substitute in the backs of BALB/c male mice up to for 14 days.

RESULTS

LIF-transfected cells as well as vector-transfected fibroblasts significantly proliferated by 1, 10, or 100 ng VEGF on days 3 and 5. Erk mitogen-activated protein (MAP) kinase phosphorylation was observed from 1 to 30 min in LIF-transfected and 10 ng of VEFG, and 1 to 60 min in LIF-transfected and 100 ng VEFG treatments. The cellular fibronectin levels also increased in LIF-transfected cells with 10 and 100 ng VEGF additions. In in vivo analyses, LIF-transfected embryonic fibroblasts with 50 microg of VEGF markedly enhanced collagen I expression and CD34 angiogenic marker on days 7 and 14.

CONCLUSION

LIF transfection and VEGF treatment enhanced phosphorylated-Erk-MAP kinase in vitro. In vivo study revealed that the combined application of LIF transfection of embryonic fibroblasts with an angiogenic factor such as VEGF in the template of a dermal substitute induced greater skin collagen production and angiogenesis in the dermal substitute.

Biological evaluation of ChuangYuLing dressing-a multifunctional medicine carrying biomaterial

The safety of Chuangyuling (CYL) dressing-a multifunctional medicine carrying biomaterial was evaluated in order to provide foundation for the application of CYL as material used in the wound healing. The traditional Chinese medicine (TCM) extract solution was compounded with scaffolds (gelatin and Bletilla hyacinthine gum), and then frozen and dried to form spongy and porous material CYL. According to the standard of biological evaluation of medical devices that was instituted by the ministry of health of China, the biological evaluation of CYL dressing was conducted. The results showed that all the contents of biological evaluation test consisting of acute toxicity, skin irritation, sensitization and cytotoxicity met the requirement of standards. It was concluded that the biomaterial carrying TCM (CYL dressing) is safe for application of wound healing.

Clinical evaluation of a new bilayer artificial dermis for repair of oral mucosal defects: report of two cases

Free mucosal grafts or split-thickness skin grafts have been used in patients undergoing repair procedures for oral mucosal defects. Conventional methods require the creation of second surgical wounds for use as donor sites. We applied two bilayers of artificial dermis to repair a buccal mucosal defect in one case and vestibular extension in another case. After removal of the sutures, no infection, pain, or hemorrhage developed in these patients. The results of granulation and epithelialization were good. Satisfactory appearance and function were achieved in both cases. Therefore, bilayer artificial dermis may be recommended for the repair of oral mucosal defects.

Tissue engineering skin flaps: which vascular carrier, arteriovenous shunt loop or arteriovenous bundle, has more potential for angiogenesis and tissue generation?

This study was designed to clarify which vascular carrier, the arteriovenous shunt loop or the arteriovenous bundle, has more potential as a vascular carrier for an artificial skin flap in rats. An arteriovenous shunt loop was constructed between the femoral artery and vein using an interpositional artery (group I) or vein (group II) graft. For arteriovenous bundle groups, the femoral artery and vein were used and subdivided into two groups: distal ligation type (group III) and flow-through type (group IV). The vascular pedicle was wrapped with an artificial dermis and implanted beneath the inguinal skin for 4 weeks. For the control group, a folded sheet of artificial dermis without any vascular carrier was embedded. In experiment 1, the volumes of generated tissue within the artificial dermis were measured in the experimental and control groups (n = 5 in each group). In experiment 2, the origin of new blood vessels sprouting from the arteriovenous shunt loop and arteriovenous bundle were evaluated histologically. The volume of generated tissue in the shunt groups was significantly greater than that in the bundle groups (p < 0.01). However, the bundle groups also showed a great potential for producing new tissue. Serial histological studies showed that new capillaries were derived not only from the vasa vasorum of the femoral vessels but directly from the femoral vein in both the shunt and the bundle groups. This "sprouting" was extensively exhibited in the group III. Although the arteriovenous shunt loop showed a greater potential for producing new tissue and capillaries, the distal ligation type of bundle was thought to be an effective and practical vascular carrier for producing a tissue-engineered skin flap.