Classification and pathophysiology of skin grafts

The Goettingen minipig as an experimental model in wound-healing studies

Background

Deep dermal wounds in extensive burns and chronic wound-healing disorders represent a significant medical problem and require a high level of therapy to reduce the risk of infection and other long-term consequences, such as amputation. A better understanding of the wound-healing processes is essential, and animal models are indispensable to fundamental research.

Objective

This study aimed to provide a transparent protocol and prove the effectiveness of an in vivo porcine model using Goettingen minipigs for wound-healing studies.

Material and methods

Thirteen female Goettingen minipigs were kept in species-appropriate housing and were treated according to the German law for the protection of animals. The study was performed with permission from the local ethical review committee of animal welfare. The experimental procedure for studying dermal regeneration in 102 full-thickness wounds through clinical observation and histological analysis, focusing on neodermal formation, is described in detail.

Results

The Goettingen minipig model proved to be suitable in wound-healing studies. The dermal regeneration was evident and viewable without wound contamination or any rejection reaction. The histological evaluations were also reliable and clearly presented the optimized wound healing of deep dermal wounds using the different therapeutic approaches.

Conclusion

Given the great clinical need for alternative or complementary therapies, we considered the Goettingen minipig trial a reliable, ethically justifiable, effective, and reproducible in vivo model for wound-healing studies.

Follicular unit grafting in chronic ulcers: A valuable technique for integrated management

Chronic ulcers significantly affect the quality of life of patients and impose a high cost on the healthcare system. The therapeutic management should be comprehensive, taking into consideration the etiological diagnosis of the wound and the characteristics of the wound bed when deciding on a therapeutic proposal appropriate to the healing phase, correcting factors that delay healing. During the epithelialization phase, repair techniques with grafts are recommended to shorten re-epithelialization time, improve the quality of scar tissue, and achieve adequate pain management. Currently, due to the reported benefits of skin appendages, the technique of follicular unit auto-grafting obtained with a scalp punch is among the chosen strategies for wound repair. This is a minimally invasive, outpatient practice, whose technique has advantages over the donor site, patients recovery and well-being.

Bionic artificial skin with a fully implantable wireless tactile sensory system for wound healing and restoring skin tactile function

Tactile function is essential for human life as it enables us to recognize texture and respond to external stimuli, including potential threats with sharp objects that may result in punctures or lacerations. Severe skin damage caused by severe burns, skin cancer, chemical accidents, and industrial accidents damage the structure of the skin tissue as well as the nerve system, resulting in permanent tactile sensory dysfunction, which significantly impacts an individual's daily life. Here, we introduce a fully-implantable wireless powered tactile sensory system embedded artificial skin (WTSA), with stable operation, to restore permanently damaged tactile function and promote wound healing for regenerating severely damaged skin. The fabricated WTSA facilitates (i) replacement of severely damaged tactile sensory with broad biocompatibility, (ii) promoting of skin wound healing and regeneration through collagen and fibrin-based artificial skin (CFAS), and (iii) minimization of foreign body reaction via hydrogel coating on neural interface electrodes. Furthermore, the WTSA shows a stable operation as a sensory system as evidenced by the quantitative analysis of leg movement angle and electromyogram (EMG) signals in response to varying intensities of applied pressures.

Comparison of full-thickness skin graft and punch grafting in the reconstruction of plantar defects

Acral melanoma commonly occurs on weight-bearing areas of the sole. Reconstruction of such areas presents a surgical challenge due to limited availability and mobility of local skin. Thus, we aimed to compare the scar outcome of full-thickness skin graft (FTSG) and punch grafting in the reconstruction of plantar defects after melanoma surgery. We retrospectively reviewed six patients who underwent both FTSG for nonweight-bearing areas and punch grafting for weight-bearing areas. We compared results of FTSG and punch grafting within the same patient. Photos of completely healed scars were graded using the Stony Brook Scar Evaluation Scale (SBSES). The averages of the FTSG scores and the punch graft scores, as measured by the SBSES, were statistically compared. Punch grafting yielded a better outcome than FTSG, according to the SBSES. The average of the punch grafting scars was 4.67, which was significantly greater (p = 0.004) than that of FTSG scar scores at 1.83. For weight-bearing areas, punch grafting should be considered as the first option of reconstruction, with FTSG as a second option for nonweight-bearing areas. Overall, this combined approach provides an effective and safe method for reconstruction of extensive plantar wounds.

Palmar reconstruction using full-thickness skin grafts from the groin and lateral malleolus regions: A comparison of long-term outcomes

Using the skin of the lateral malleolus region for reconstruction of smaller areas of the palm may yield better outcomes than using the skin of the groin region. However, no previous study has provided long-term data comparing the groin and lateral malleolus regions as donor sites for full-thickness skin grafts (FTSGs) in palmar reconstruction. Therefore, this study aimed to compare the groin and lateral malleolus regions as donor sites for FTSGs in palmar reconstruction over a long-term follow-up period. The patients were classified into groin and lateral malleolus region groups (n = 15 each). Measurements were obtained at the graft site, the contralateral site corresponding to the graft site, and the donor site. A chromameter was used to measure skin color, and the Patient and Observer Scar Assessment Scale (POSAS) was used to evaluate the scar at the skin graft site. Compared to the groin region group, the lateral malleolus region group showed skin colors that were closer to the original color of the palm in terms of lightness and red/green values. Additionally, the lateral malleolus region group received better esthetic ratings in the POSAS. Our results revealed that using the lateral malleolus region for FTSGs in palmar reconstruction resulted in better outcomes than using the groin region, even over a long period.

Full-thickness skin columns: A method to reduce healing time and donor site morbidity in deep partial-thickness burns

The current standard of care for the coverage of large wounds often involves split thickness skin grafts (STSGs) which have numerous limitations. One promising technique that has gained traction is fractional autologous skin grafting using full-thickness skin columns (FTSC). Harvesting occurs orthogonally by taking numerous individual skin columns containing the epidermis down through the dermis and transferring them to the wound bed. The purpose of this porcine study was to investigate the efficacy of implanting FTSCs directly into deep partial-thickness burn wounds, as well as examining donor site healing at the maximal harvest density. It was hypothesised that by utilising FTSCs, the rate of healing in deep partial thickness burns can be improved without incurring the donor morbidity seen in other methods of skin grafting. Deep partial-thickness burns were created on the dorsum of female red duroc swine, debrided 3 days later and FTSCs were implanted at varying expansion ratios directly into the burn wounds. At day 14, 1:50 expansion ratio showed significantly faster re-epithelialisation compared to the debrided burn control and 1:200. Donor sites (at 7%-10% harvest density) were 100% re-epithelialised by day 7. Additionally, the maximal harvest density was determined to be 28% in an ex vivo model, which then five donor sites were harvested at 28% density on a red duroc swine and compared to five STSG donor sites. At maximal harvest density, FTSC donor sites were significantly less hypopigmented compared to STSGs, but no significant differences were observed in re-epithelialisation, contraction, blood flow or dermal thickness. In conclusion, implantation directly into deep partial-thickness burns is a viable option for the application of FTSCs, favouring lower expansion ratios like 1:50 or lower. Little difference in donor site morbidity was observed between FTSC at a maximal harvest density of 28% and STSGs, exceeding the optimal harvest density.

Evaluation in a porcine wound model and long-term clinical assessment of an autologous heterogeneous skin construct used to close full-thickness wounds

Acute and chronic wounds involving deeper layers of the skin are often not adequately healed by dressings alone and require therapies such as skin grafting, skin substitutes, or growth factors. Here we report the development of an autologous heterogeneous skin construct (AHSC) that aids wound closure. AHSC is manufactured from a piece of healthy full-thickness skin. The manufacturing process creates multicellular segments, which contain endogenous skin cell populations present within hair follicles. These segments are physically optimized for engraftment within the wound bed. The ability of AHSC to facilitate closure of full thickness wounds of the skin was evaluated in a swine model and clinically in 4 patients with wounds of different etiologies. Transcriptional analysis demonstrated high concordance of gene expression between AHSC and native tissues for extracellular matrix and stem cell gene expression panels. Swine wounds demonstrated complete wound epithelialization and mature stable skin by 4 months, with hair follicle development in AHSC-treated wounds evident by 15 weeks. Biomechanical, histomorphological, and compositional analysis of the resultant swine and human skin wound biopsies demonstrated the presence of epidermal and dermal architecture with follicular and glandular structures that are similar to native skin. These data suggest that treatment with AHSC can facilitate wound closure.

Autologous Skin Grafts, versus Tissue-engineered Skin Constructs: A Systematic Review and Meta-analysis

For over 100 years, autologous skin grafts have remained the gold standard for the reconstruction of wounds but are limited in availability. Acellular tissue-engineered skin constructs (acellular TCs) and cellular tissue-engineered skin constructs (cellular TCs) may address these limitations. This systematic review and meta-analysis compare outcomes between them.

Methods

A systematic review was conducted using PRISMA guidelines, querying MEDLINE, Embase, Web of Science, and Cochrane to assess graft incorporation, failure, and wound healing. Case reports/series, reviews, in vitro/in vivo work, non-English articles or articles without full text were excluded.

Results

Sixty-six articles encompassing 4076 patients were included. No significant differences were found between graft failure rates (P = 0.07) and mean difference of percent reepithelialization (p = 0.92) when split-thickness skin grafts were applied alone versus co-grafted with acellular TCs. Similar mean Vancouver Scar Scale was found for these two groups (p = 0.09). Twenty-one studies used at least one cellular TC. Weighted averages from pooled results did not reveal statistically significant differences in mean reepithelialization or failure rates for epidermal cellular TCs compared with split-thickness skin grafts (p = 0.55).

Conclusions

This systematic review is the first to illustrate comparable functional and wound healing outcomes between split-thickness skin grafts alone and those co-grafted with acellular TCs. The use of cellular TCs seems promising from preliminary findings. However, these results are limited in clinical applicability due to the heterogeneity of study data, and further level 1 evidence is required to determine the safety and efficacy of these constructs.

Vascularization of cutaneous wounds by stem cells

Differentiated skin cells have limited self-renewal capacity; thus, the application of stem/progenitor cells, adult or induced stem cells, has attracted much attention for wound healing applications. Upon skin injury, vascularization, known as a highly dynamic process, occurs with the contribution of cells, the extracellular matrix, and relevant growth factors. Considering the importance of this process in tissue regeneration, several strategies have been proposed to enhance angiogenesis and accelerate wound healing. Previous studies report the effectiveness of stem/progenitor cells in skin wound healing by facilitating the vascularization process. This chapter reviews and highlights some of the key and recent investigations on application of stem/progenitor cells to induce skin revascularization after trauma.

Readability, reliability and credibility of online patient information on skin grafts

BACKGROUND

Skin grafting reflects a common dermatological procedure for closing skin defects. Patient education is important for managing expectation and optimising skin graft take. While health information is increasingly accessed on the internet, there are no existing studies assessing their quality.

METHODS

The first 25 results from Google, Microsoft Bing and Yahoo! search engines using the term 'skin graft' were analysed using a variety of standard instruments. Readability was assessed using the Flesch-Kincaid Grade score (FKG), Gunning Fog Index (GFI), Simple Measure of Gobbledygook (SMOG) and the New Dale-Chall Readability Index (NDC). Reliability was assessed using the DISCERN instrument and credibility with the Journal of the American Medical Association Benchmark Criteria (JAMA). Transparency was identified by presence of the Health On the Net Foundation Code certification (HON-code).

RESULTS

Seventy-five websites were identified. After exclusion, forty-three remaining websites were analysed with average FKG, GFI and SMOG scores of 7.8, 10.1 and 10.7, respectively. The average NDC was 5.9. The average reliability was fair with a DISCERN score based on the first 15 questions of the instrument of 42.6. The mean JAMA score was 2, and 9 websites displayed the HON-code certificate.

CONCLUSIONS

Readability, reliability and credibility of online health information regarding skin grafting can be improved. Health care providers should critically assess existing online patient information or develop alternative material to educate patients undergoing skin graft surgery.

The Role of Cell-Based Therapies in Acute Burn Wound Skin Repair: A Review

Tissue engineering solutions for skin have been developed over the last few decades with a focus initially on a two-layered structure with epithelial and dermal repair. An essential element of skin restoration is a source of cells capable of differentiating into the appropriate phenotype. The need to repair areas of skin when traditional techniques were not adequate addressed led to cell based therapies being developed initially as a laboratory-based tissue expansion opportunity, both as sheets of cultured epithelial autograft and in composite laboratory-based skin substitutes. The time to availability of the cell-based therapies has been solved in a number of ways, from using allograft cell-based solutions to the use of point of care skin cell harvesting for immediate clinical use. More recently pluripotential cells have been explored providing a readily available source of cells and cells which can express the broad range of phenotypes seen in the mature skin construct. The lessons learnt from the use of cell based techniques has driven the exploration of the use of 3D printing technology, with controlled accurate placement of the cells within a specific printed construct to optimise the phenotypic expression and tissue generation.

Circumferential full-thickness skin grafting: An excellent method for the treatment of short penile skin in adult men

Objective

Short penile skin due to excessive circumcision is a complex condition requiring surgical care. The study aims to investigate the effect of full-thickness skin grafting (FTSG) in treating short penile skin.

Methods

A retrospective analysis was performed on 24 patients with insufficient penile skin. The included patients underwent full-thickness skin grafting from the scrotum and the groin region in the Genital Plastic Surgery Center between February 2014 and September 2021. Morphology of the penis, length of the penis, complication, and donor area healing status was observed by the authors. Additionally, the International Index of Erectile Function Questionnaire (IIEF-5) and the patient's evaluation of penile appearance were investigated.

Results

An aesthetically pleasing appearance of the penis was obtained by FTSG in 24 patients. The length of penis was improved after surgery (5.70 cm ± 1.24 cm vs. 6.05 cm ± 1.33 cm, P value < 0.05). All patients had good healing of the penile area without serious complications. Only 2 cases showed minor partial necrosis and recovered soon after proper treatment. A high patient's evaluation of penile appearance was received (4.08 ± 0.71, mean ± SD) and the scores of IIEF-5 increased significantly after surgery (18.38 ± 2.24 vs. 21.08 ± 1.79, P-value < 0.05).

Conclusions

FTSG from the scrotum and inguinal skin provides good aesthetic and functional results for treating short penile skin. FTSG, particularly the scrotum-derived skin graft, offers a great supplement to penile skin. It could be suggested as a promising method of treating insufficient penile skin, which meets both functional and aesthetic needs.

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.

Objective Skin Quality Assessment after Reconstructive Procedures for Facial Skin Defects

Local random skin flaps and skin grafts are everyday surgical techniques used to reconstruct skin defects. Although their clinical advantages and disadvantages are well known, there are still uncertainties with respect to their long-term results. Hence, the aim of this study was to evaluate outcomes more than one-year post operatively using objective measurement devices. The study included 31 facial defects reconstructed with local random flap, 30 facial defects reconstructed with split-thickness skin grafts (STSGs) and 30 facial defects reconstructed with full-thickness skin grafts (FTSGs). Skin quality was objectively evaluated using MP6 noninvasive probes (Courage + Khazaka GmbH, Cologne, Germany), which measure melanin count, erythema, hydration, sebum, friction and transepidermal water loss. The results showed that there were no significant differences in melanin count, erythema, hydration, sebum level, friction value and transepidermal water loss (TEWL) between the site reconstructed with random local flaps and the same site on the healthy contralateral side of the face. However, both FTSGs and STSGs showed significantly higher levels in terms of TEWL and erythema, whereas the levels of hydration, sebum and friction were significantly lower compared to the healthy contralateral side. Moreover, STSGs resulted in a significant difference in melanin count. These findings imply that the complex pathophysiology of the wound-healing process possibly results in better skin-quality outcomes for random local flaps than skin autografts. Consequently, this suggests that random local flaps should be implemented whenever possible for the reconstruction of facial region defects.

[Venous ulcus cruris-Surgical treatment]

Venous ulcus cruris is usually a chronic disease and an extreme burden for patients and their families. An analysis based on a random statutory health insurance sample of the AOK Hessen/KV Hessen estimated the number of affected people to be 400,000 in Germany. A venous ulcus cruris is always caused by an underlying chronic venous insufficiency (CVI). A spontaneous healing of this chronic disease without treatment is not to be expected. The conservative treatment includes an adequate compression treatment and exudate management. Surgical treatment is based on three pillars: an open surgical or endovenous approach to resolve the pathological venous reflux, uIcer surgery and in rare cases the various procedures of fascia surgery as well as defect coverage by a combination of negative pressure wound therapy and skin transplantation.

Assessment of Two Commonly used Dermal Regeneration Templates in a Swine Model without Skin Grafting

In the medical care of partial and full-thickness wounds, autologous skin grafting is still the gold standard of dermal replacement. In contrast to spontaneous reepithelializing of superficial wounds, deep dermal wounds often lead to disturbing scarring, with cosmetically or functionally unsatisfactory results. However, modern wound dressings offer promising approaches to surface reconstruction. Against the background of our future aim to develop an innovative skin substitute, we investigated the behavior of two established dermal substitutes, a crosslinked and a non-crosslinked collagen biomatrix. The products were applied topically on a total of 18 full-thickness skin defects paravertebrally on the back of female Göttingen Minipigs—six control wounds remained untreated. The evaluation was carried out planimetrically (wound closure time) and histologically (neoepidermal cell number and epidermis thickness). Both treatment groups demonstrated significantly faster reepithelialization than the controls. The histologic examination verified the highest epidermal thickness in the crosslinked biomatrix-treated wounds, whereas the non-crosslinked biomatrix-treated wounds showed a higher cell density. Our data presented a positive influence on epidermal regeneration with the chosen dermis substitutes even without additional skin transplantation and, thus, without additional donor site morbidity. Therefore, it can be stated that the single biomatrix application might be used in a clinical routine with small wounds, which needs to be investigated further in a clinical setting to determine the size and depths of a suitable wound bed. Nevertheless, currently available products cannot solely achieve wound healing that is equal to or superior to autologous tissue. Thus, the overarching aim still is the development of an innovative skin substitute to manage surface reconstruction without additional skin grafting.

Smart 3D Printed Hydrogel Skin Wound Bandages: A Review

Wounds are a major health concern affecting the lives of millions of people. Some wounds may pass a threshold diameter to become unrecoverable by themselves. These wounds become chronic and may even lead to mortality. Recently, 3D printing technology, in association with biocompatible hydrogels, has emerged as a promising platform for developing smart wound dressings, overcoming several challenges. 3D printed wound dressings can be loaded with a variety of items, such as antibiotics, antibacterial nanoparticles, and other drugs that can accelerate wound healing rate. 3D printing is computerized, allowing each level of the printed part to be fully controlled in situ to produce the dressings desired. In this review, recent developments in hydrogel-based wound dressings made using 3D printing are covered. The most common biosensors integrated with 3D printed hydrogels for wound dressing applications are comprehensively discussed. Fundamental challenges for 3D printing and future prospects are highlighted. Additionally, some related nanomaterial-based hydrogels are recommended for future consideration.

Automated Assessment of Cell Infiltration and Removal in Decellularized Scaffolds - Experimental Study in Rabbits

Objective  Semiquantitative and automated measurement of nuclear material removal and cell infiltration in decellularized tendon scaffolds (DTSs). Method  16 pure New Zealand rabbits were used, and the gastrocnemius muscle tendon was collected bilaterally from half of these animals (16 tendons collected); 4 were kept as control and 12 were submitted to the decellularization protocol (DTS). Eight of the DTSs were used as an in vivo implant in the experimental rotator cuff tear (RCT) model, and the rest, as well as the controls, were used in the semiquantitative and automated evaluation of nuclear material removal. The eight additional rabbits were used to make the experimental model of RCT and subsequent evaluation of cellular infiltration after 2 or 8 weeks, within the DTS. Results  The semiquantitative and automated analysis used demonstrated a removal of 79% of nuclear material ( p  < 0.001 and power > 99%) and a decrease of 88% (p < 0.001 and power >99%) in the area occupied by nuclear material after the decellularization protocol. On cell infiltration in DTS, an increase of 256% (p < 0.001 and power >99%) in the number of cells within the DTS was observed in the comparison between 2 and 8 weeks postoperatively. Conclusion  The proposed semiquantitative and automated measurement method was able to objectively measure the removal of nuclear material and cell infiltration in DTS.

Edward F. Adolph Distinguished Lecture. It's more than skin deep: thermoregulatory and cardiovascular consequences of severe burn injuries in humans

Each year, within the United States, tens of thousands of individuals are hospitalized for burn-related injuries. The treatment of deep burns often involves skin grafts to accelerate healing and reduce the risk of infection. The grafting procedure results in a physical disruption between the injured and subsequently debrided host site and the skin graft placed on top of that site. Both neural and vascular connections must occur between the host site and the graft for neural modulation of skin blood flow to take place. Furthermore, evaporative cooling from such burn injured areas is effectively absent, leading to greatly impaired thermoregulatory responses in individuals with large portions of their body surface area burned. Hospitalization following a burn injury can last weeks to months, with cardiovascular and metabolic consequences of such injuries having the potential to adversely affect the burn survivor for years postdischarge. With that background, the objectives of this article are to discuss 1) our current understanding of the physiology and associated consequences of skin grafting, 2) the effects of skin grafts on efferent thermoregulatory responses and the associated consequences pertaining to whole body thermoregulation, 3) approaches that may reduce the risk of excessive hyperthermia in burn survivors, 4) the long-term cardiovascular consequences of burn injuries, and 5) the extent to which burn survivors can "normalize" otherwise compromised cardiovascular responses. Our primary objective is to guide the reader toward an understanding that severe burn injuries result in significant physiological consequences that can persist for years after the injury.

Fractal analysis of rat dermal tissue in the different injury states

Scar formation and chronic ulcers can develop following a skin injury. They are the result of the over- or underproduction of collagen. It is very important to evaluate the quality and quantity of the collagen that is produced during wound healing, especially with respect to its structure, as these factors are very important to a complicated outcome. However, there is no standard way to quantitatively analyse dermal collagen. As prior work characterised some potentially fractal properties of collagen, it was hypothesised that collagen structure could be evaluated with fractal dimension analysis. Small-angle X-ray scattering technology (SAXS) was used to evaluate the dermis of rats exposed to graft harvest, burn, and diabetic pathologic states. It was found that almost all collagen structures could be quantitatively measured with fractal dimension analysis. Further, there were significant differences in the three-dimensional (3-D) structure of normal collagen versus that measured in pathologic tissues. There was a significant difference in the 3-D structure of collagen at different stages of healing. The findings of this work suggest that fractal analysis is a good tool for wound healing analysis, and that quantitative collagen analysis is very useful for assessing the structure of dermal collagen.

Self-Assembled Nanofibrous Marine Collagen Matrix Accelerates Healing of Full-Thickness Wounds

There is an urgent clinical need for wound dressings to treat skin injuries, particularly full-thickness wounds caused by acute and chronic wounds. Marine collagen has emerged as an attractive and safer alternative due to its biocompatibility, diversity, and sustainability. It has minimum risk of zoonotic diseases and less religious constraints as compared to mammalian collagen. In this study, we reported the development of a self-assembled nanofibrous barramundi (Lates calcarifer) collagen matrix (Nano-BCM), which showed good biocompatibility for full-thickness wound-healing applications. The collagen was extracted and purified from barramundi scales and skin. Thereafter, the physicochemical properties of collagen were systematically evaluated. The process to extract barramundi skin collagen (BC) gave an excellent 45% yield and superior purity (∼100%). More importantly, BC demonstrated structural integrity, native triple helix structure, and good thermal stability. BC demonstrated its efficacy in promoting human primary dermal fibroblast (HDF) and immortalized human keratinocytes (HaCaT) proliferation and migration. Nano-BCM has been prepared via self-assembly of collagen molecules in physiological conditions, which resembled the native extracellular matrix (ECM). The clinical therapeutic efficacy of the Nano-BCM was further evaluated in a full-thickness splinted skin wound mice model. In comparison to a clinically used wound dressing (DuoDerm), the Nano-BCM demonstrated significantly accelerated wound closure and re-epithelization. Moreover, Nano-BCM nanofibrous architecture and its ability to facilitate early inflammatory response significantly promoted angiogenesis and differentiated myofibroblast, leading to enhanced wound healing. Consequently, Nano-BCM demonstrates great potential as an economical and effective nonmammalian substitute to achieve skin regeneration.

Point-of-Care Ultrasound as a Tool to Assess Wound Size and Tissue Regeneration after Skin Grafting

Chronic wounds can be difficult to heal and are often accompanied by pain and discomfort. Multiple skin substitutes or cellularized/tissue-based skin products have been used in an attempt to facilitate closure of complex wounds. Allografts from cadaveric sources have been a viable option in achieving such closure. However, early assessment of graft incorporation has been difficult clinically, often with delayed evidence of failure. Visual cues to assess graft integrity have been limited and remain largely superficial at the skin surface. Furthermore, currently used optical imaging techniques can penetrate only a few millimeters deep into tissue. Ultrasound (US) imaging offers a potential solution to address this limitation. This work evaluates the use of US to monitor wound healing and allograft integration. We used a commercially available dual-mode (US and photoacoustic) scanner operating only in US mode. We compared the reported wound size from the clinic with the size measured using US in 45 patients. Two patients from this cohort received an allogenic skin graft and underwent multiple US scans over a 110-d period. All data were processed by two independent analysts; one of them was blinded to the study. We measured change in US intensity and wound contraction as a function of time. Our results revealed a strong correlation (R² = 0.81, p < 0.0001) between clinically and US-measured wound sizes. Wound contraction >91% was seen in both patients after skin grafting. An inverse relationship between wound size and US intensity (R² = 0.77, p < 0 .0001) indicated that the echogenicity of the wound bed increases as healthy cells infiltrate the allograft matrix, regenerating and leading to healthy tissue and re-epithelization. This work indicates that US can be used to measure wound size and visualize tissue regeneration during the healing process.

The Reverdin Graft: The Forgotten Skin Transplant

ABSTRACT

This article describes a series of four patients for whom a Reverdin graft was performed. The Reverdin graft, also known as a pinch graft, is a method to promote epithelialization for superficial wounds. The intervention is minimally invasive with a short learning curve. The procedure and its advantages and disadvantages are discussed in this case series. This pinch graft is a widely accepted, minimally invasive intervention to accelerate the epithelialization of wounds.

3D bioprinting of a cell-laden antibacterial polysaccharide hydrogel composite

Bioink with inherent antibacterial activity is of particular interest for tissue engineering application due to the growing number of bacterial infections associated with impaired wound healing or bone implants. However, the development of cell-laden bioink with potent antibacterial activity while supporting tissue regeneration proved to be challenging. Here, we introduced a cell-laden antibacterial bioink based on Methylcellulose/Alginate (MC/Alg) hydrogel for skin tissue engineering via elimination of the risks associated with a bacterial infection. The key feature of the bioink is the use of gallium (Ga⁺³) in the design of bioink formulation with dual functions. First, Ga⁺³ stabilized the hydrogel bioink by the formation of ionic crosslinking with Alg chains. Second, the gallium-crosslinked bioink exhibited potent antibacterial activity toward both Gram-positive (Staphylococcus aureus) and Gram-negative (Pseudomonas aeruginosa) bacteria with a bactericidal rate of 99.99 %. In addition, it was found that the developed bioink supported encapsulated fibroblast cellular functions.

Efficacy and safety of skin grafting in treatment of vasculitic ulcer and pyoderma gangrenosum-A systematic review

Chronic painful ulcers caused by pyoderma gangrenosum (PG) and cutaneous vasculitis remain to be a therapeutic challenge. Skin grafts have been used with success in selected cases but are generally avoided due to the fear of pathergy. The aim of this study was to investigate the safety and efficacy of skin grafting in the treatment of primary vasculitic ulcer (PVU) and PG. MEDLINE, Embase, the Cochrane Library, Clinicaltrial.gov, and WHO International Clinical Trials Registry Platform (ICTRP) were searched from inception to March 2020. A search for grey literature was conducted in May 2020. We included studies assessing the efficacy and safety of skin grafting in the treatment of PG and PVU. Studies were only included if skin grafting was performed after establishment of PG or PVU diagnosis. A total of 721 articles was identified through the database search of which 92 were included in this study. Ten articles were identified by handsearching the reference list of included studies. Finally, 102 articles describing 212 wounds in 153 patients were included. Complete healing was found in 75.5% of the wounds. The average time to complete was 10.8 weeks (95% CI 6.1-15.6). The mean donor site healing time was 1.9 weeks (95% CI 0.52-3.20). Pathergy was reported in 8 (5.2%) patients. One patient had severe infection related to skin grafting. A statistically significant difference in the number of patients receiving preoperative (P = .0079) and postoperative (P = .002) immunosuppressive therapy was found between the groups with complete healing/reduction and no improvement/aggravation. This systematic review finds the current evidence on efficacy and safety of skin grafting in treatment of PG and PVU to be promising but limited to the size and lack of studies superior to case reports and case series. Future placebo-controlled trials are required to draw a stronger conclusion.

Facilitated self-assembly of a prevascularized dermal/epidermal collagen scaffold

Introduction: Resurfacing complex full thickness wounds requires free tissue transfer which creates donor site morbidity. We describe a method to fabricate a skin flap equivalent with a hierarchical microvascular network. Materials & methods: We fabricated a flap of skin-like tissue containing a hierarchical vascular network by sacrificing Pluronic^® F127 macrofibers and interwoven microfibers within collagen encapsulating human pericytes and fibroblasts. Channels were seeded with smooth muscle and endothelial cells. Constructs were topically seeded with keratinocytes. Results: After 28 days in culture, multiphoton microscopy revealed a hierarchical interconnected network of macro- and micro-vessels; larger vessels (>100 μm) were lined with a monolayer endothelial neointima and a subendothelial smooth muscle neomedia. Neoangiogenic sprouts formed in the collagen protodermis and pericytes self-assembled around both fabricated vessels and neoangiogenic sprouts. Conclusion: We fabricated a prevascularized scaffold containing a hierarchical 3D network of interconnected macro- and microchannels within a collagen protodermis subjacent to an overlying protoepidermis with the potential for recipient microvascular anastomosis.

Immune tolerance of allogeneic haematopoietic cell transplantation supports donor epidermal grafting of recessive dystrophic epidermolysis bullosa chronic wounds

BACKGROUND

Chronic wounds, a common morbidity in recessive dystrophic epidermolysis bullosa (RDEB), lack definitive therapies.

OBJECTIVES

To assess allogeneic epidermal skin grafts in terms of wound healing and durability over time.

METHODS

In a prospective, open-label clinical trial for postallogeneic haematopoietic cell transplantation (post-alloHCT) patients with RDEB, up to nine chronic wounds per patient were grafted over 1 year. Epidermal grafts measuring 5 cm² were obtained from related alloHCT donors in the outpatient setting using the CELLUTOME^TM Epidermal Harvesting System. Wounds were photographed and symptom inventories completed at baseline and 6, 12 and 52 weeks after grafting. The trial was registered at ClinicalTrials.gov (NCT02670837).

RESULTS

Between August 2016 and January 2019, eight patients with RDEB received a total of 35 epidermal allografts at a median of 1157 days (range 548-2884) post-alloHCT. The median (interquartile range) percentage reductions in wound surface area were 75% (52-94), 95% (72-100) and 100% (97-100) at 6, 12 and 52 weeks postgraft, respectively, each significantly reduced from baseline (P < 0·001). Donor harvest sites healed quickly without scarring. Biopsy evaluation at 1 year of an epidermal allograft site revealed wildtype type VII collagen (immunofluorescence), anchoring fibrils (electron microscopy), and full-thickness skin whole-DNA donor chimerism of 42% (compared with 16% in concurrently biopsied native skin). This strategy subsequently supported release of RDEB pseudosyndactyly.

CONCLUSIONS

The immune tolerance established by alloHCT supports successful adoptive transfer of donor epidermal grafts. Persistence of donor grafts in a single patient beyond 1 year and observed migration of donor-grafted cells into adjacent wound suggest that epidermal allografts include nonterminally differentiated cells and/or trigger recruitment of donor bone-marrow-derived cells to mediate wound healing.

A new decellularized tendon scaffold for rotator cuff tears - evaluation in rabbits

Background

Scaffolds have considerably advanced in recent years. In orthopaedic surgery, scaffolds have been used as grafts in procedures involving tendon and ligament reconstruction. This paper aimed to produce and evaluate decellularized tendon scaffolds (DTSs) from biomechanical, microscopic, macroscopic and in vivo perspectives.

Methods

Bilateral gastrocnemius muscle tendons from 18 adult New Zealand rabbits were collected. Of these 36 tendons, 11 were used as controls (Group A - control), and 25 were used in the decellularization protocol (Group B - DTS). The groups were subjected to histological, biomechanical and macroscopic analyses, and Group B - DTS was subjected to an additional in vivo evaluation. In the decellularization protocol, we used a combination of aprotinin, ethylenediamine tetraacetic acid (EDTA), sodium dodecyl sulfate (SDS) and t-octyl-phenoxypolyethoxyethanol (Triton X-100) for six days. During this period, the scaffolds were kept at room temperature on an orbital shaker with constant motion.

Results

The DTSs showed an increased cross-sectional area and inter-fascicular distance and no change in parallelism or matrix organization. The nuclear material was not organized in the DTSs as it was in the control. In the biomechanical analysis, no significant differences were found between the groups after analysing the ultimate tensile load, stiffness, and elongation at the ultimate tensile load. During the in vivo evaluation, mononuclear cell infiltration was noted.

Conclusions

The evaluated decellularization protocol generated a tendon scaffold, maintained the most important biomechanical characteristics and permitted cell infiltration.

Evaluation of Patients' Preferences for Skin Grafting in Plastic-Surgical Defect Coverage

BACKGROUND

Grafting split-thickness (STSGs) and full-thickness skin grafts (FTSGs) are common techniques to replace missing skin and to restore the skin barrier in burn, trauma and remaining skin defects after tumor resections. The defect coverage with skin grafts offer many advantages, but also disadvantages such as donor site morbidity like possible sensory disturbances, scarring, risk of infection, contour changes and pigment disorders. We aimed to assess the preferred distribution of donor site for STSGs and FTSGs in patient’s skin grafting for plastic-surgical defect coverage.

METHODS

Patients and their accompany persons referred to the Department of Plastic Surgery were interviewed for defect coverage with STSGs or FTSGs, the preference in donor site was investigated and the detailed advantages and disadvantages were clarified.

RESULTS

We evaluated 85 participants (male=43, female=42) with a median age of 42 years (mean=46 years). The definition of the donor site (n=188 markings) was mainly based on the physicians recommendation (32.98%), mobility (23.40%), aesthetic results (22.34%) and pain (21.28%). Feared complications (n=152) were mainly wound healing disorders (32.24%), circulation disorders (28.29%), scars (20.39%) and bleeding risks (19.08%). Among all participants, 79 split-skin graft preferences were specified, while 32% favored the scalp as a donor site, as well as 29% the frontal part of the left thigh and 10% the frontal part of the right thigh.

CONCLUSION

There were preferred anatomical donor sites for skin grafting. Nevertheless, in conscious patients, the donor site has to be selected in a consent talk and joint approval, preoperatively. The options of taking STSGs from the occipital region with all its advantages should be discussed intensively as it is an attractive graft donor site.

[Surgical treatment for chronic leg ulcer]

Leg ulcers pose a therapeutic challenge due to a chronic healing process. Conservative wound dressings are initially the treatment of choice, but their effectiveness in therapy-refractory wounds is limited. In these cases, multiple mechanical debridement in combination with split-thickness skin grafts (STSG) are a simple and safe treatment option for ulcer coverage. Additional therapy with negative pressure wound therapy (NPWT) improves the surgical outcome by promoting ulcer granulation, continuous elimination of exsudate and blood as well as increased contact pressure on the skin graft. After transplantation, the split skin graft requires daily wound dressings until it has fully healed after approximately 3 weeks.

Comparison of two perioperative antibiotic schedules in patients undergoing surgical reconstruction with dermal matrix after excision of skin cancer

Perioperative antibiotic treatment duration in skin reconstruction with dermal substitutes is not well established. This study compares the incidence of infective complications after two different durations of perioperative antibiotic treatment in patients undergoing surgical reconstruction with skin dermal substitutes (SDS) after excision of skin cancer. Infective complications at the site of SDS were compared in subjects undergoing surgical reconstruction who received either a > 24-hour (extended protocol) or a ≤ 24-hour (short protocol) perioperative antibiotic treatment. Of 116 patients undergoing SDS surgical reconstruction, 62 (53.4%) received an extended schedule, and 54 (46.6%) received a short schedule. The two groups were similar for gender, age, comorbidities, American Society of Anesthesiologists score, and type of skin cancer. Overall incidence rate of infection was 20.7% (24/116). No differences in terms of risk of infection were observed between the two groups (OR: 1.04, 95% CI: 0.42-2.55; P = .937). Patients undergoing SDS reconstruction in the limb/foot had a higher risk of infection in comparison with those undergoing SDS reconstruction in the chest/head (OR: 2.69, 95% CI: 1.06-6.86; P = .038). The short protocol was demonstrated to be beneficial to patients undergoing surgical reconstruction with SDS. A ≤ 24-hour perioperative antibiotic schedule did not increase the infection rate, potentially allowing a reduction of antibiotic exposure.

Split Thickness Grafts Grow From Bottom Up in Large Skin Injuries

Autologous split thickness skin graft is necessary for the survival of patients with large burns and skin defects. It is not clear how a thin split thickness skin graft becomes remarkably thicker within a few weeks following transplantation. Here, we hypothesized that growth of split thickness graft should be from bottom up probably through conversion of immune cells into collagen producing skin cells. We tested this hypothesis in a preclinical porcine model by grafting split thickness meshed skin (0.508 mm thickness, meshed at 3:1 ratio) on full thickness wounds in pigs. New tissue formation was evaluated on days 10 and 20 postoperation through histological analysis and co-staining for immune cell markers (CD45) and type I collagen. The findings revealed that a split thickness graft grew from bottom up and reached to almost the same level as uninjured skin within 60 days postoperation. The result of immune-staining identified a large number of cells, which co-expressed immune cell marker (CD45) and collagen on day 10 postoperation. Interestingly, as the number of these cells reduced on day 20, most of these cells became positive for collagen production. In another set of experiments, we tested whether immune cells can convert to collagen producing cells in vitro. The results showed that mouse adherent immune cells started to express type 1 procollagen and α-smooth muscle actin when cultured in the presence of fibroblast conditioned media. In conclusion, the early thickening of split thickness graft is likely happening through a major contribution of infiltrated immune cells that convert into mainly collagen producing fibroblasts in large skin injuries.

Use of oxidized regenerated cellulose (ORC)/collagen/silver-ORC dressings to help manage skin graft donor site wounds

Harvesting donor site explants for split-thickness skin grafting creates an iatrogenic wound that presents additional challenges to clinicians due to morbidities such as persistent bleeding, pain, infection, and delayed epithelialization. Although there have been several randomized controlled trials to compare wound dressing effectiveness, there is still a lack of standardization for donor site wound dressings.

A retrospective comparison of 59 patients that underwent split-thickness skin graft reconstructions between January 2017 and September 2018 was performed. Donor sites of Group 1 patients (n = 29) were treated with a transparent film dressing and transitioned to petrolatum gauze dressings if exudate management became problematic; Group 2 patients (n = 30) were treated with oxidized regenerated cellulose/collagen/silver-oxidized regenerated cellulose (ORC/C/Ag-ORC) dressings. Evaluations of time to epithelialization, number of dressings required, signs of inflammation, and objective pain were compared between groups.

Group 1 was comprised of 18 female and 11 male patients, whereas Group 2 was comprised of 14 females and 16 males. There were no significant differences between groups when comparing age, sex, comorbidities, or donor site size (area or depth). Patients in Group 2 had a significantly shorter time to complete re-epithelialization (P < .0001), fewer dressing changes (P < .0001), and less objective pain as measured by the need for opioid pain mediation (P < .0001) when compared to Group 1. The percentage of patients with signs of inflammation was also lower for Group 2, although this difference was not statistically significant (P = .0797).

Although prospective, controlled studies are still needed, data from this study suggest that ORC/C/Ag-ORC dressings could become a more effective alternative for the management of donor site wounds, especially in patients with known risk factors for wound healing.

Mid- to Long-term Outcomes After Split-thickness Skin Graft vs. Skin Extension by Multiple Incisions

BACKGROUND/AIM

Skin extension by multiple incisions (SEMI) may be superior to split-thickness skin graft (STSG) for closure of large soft tissue defects.

MATERIALS AND METHODS

Twenty-six patients who had undergone STSG were compared to 29 patients who had undergone SEMI on the extremities. Patient and Observer Scar Assessment Scale (POSAS), Dermatology Life Quality Index, Wound QoL (Quality of Life) and Short Form Health Survey 36 were used. Elasticity, thickness and skin sensation were compared between the treated and contralateral extremity. Range of motion in adjacent joints was measured. Complication rates were compared.

RESULTS

A total of 55 patients with a mean follow-up of 5.5 years (range=2-9 years) were examined. Patients with STSG had significantly worse scores in POSAS. The scar was thinner, less elastic and did not provide intact sensibility. Other scores, ROM and complication rates did not differ significantly.

CONCLUSION

SEMI was superior to STSG regarding patient satisfaction and scar quality.

Full Thickness Skin Expansion ex vivo in a Newly Developed Reactor and Evaluation of Auto-Grafting Efficiency of the Expanded Skin Using Yucatan Pig Model

BACKGROUND

Skin grafts are required in numerous clinical procedures, such as reconstruction after skin removal and correction of contracture or scarring after severe skin loss caused by burns, accidents, and trauma. The current standard for skin defect replacement procedures is the use of autologous skin grafts. However, donor-site tissue availability remains a major obstacle for the successful replacement of skin defects and often limits this option. The aim of this study is to effectively expand full thickness skin to clinically useful size using an automated skin reactor and evaluate auto grafting efficiency of the expanded skin using Yucatan female pigs.

METHODS

We developed an automated bioreactor system with the functions of real-time monitoring and remote-control, optimization of grip, and induction of skin porosity for effective tissue expansion. We evaluated the morphological, ultra-structural, and mechanical properties of the expanded skin before and after expansion using histology, immunohistochemistry, and tensile testing. We further carried out in vivo grafting study using Yucatan pigs to investigate the feasibility of this method in clinical application.

RESULTS

The results showed an average expansion rate of 180%. The histological findings indicated that external expansion stimulated cellular activity in the isolated skin and resulted in successful grafting to the transplanted site. Specifically, hyperplasia did not appear at the auto-grafted site, and grafted skin appeared similar to normal skin. Furthermore, mechanical stimuli resulted in an increase in COL1A2 expression in a suitable environment.

CONCLUSIONS

These findings provided insight on the potential of this expansion system in promoting dermal extracellular matrix synthesis in vitro. Conclusively, this newly developed smart skin bioreactor enabled effective skin expansion ex vivo and successful grafting in vivo in a pig model.

Identifying the factors that influence surgeon's compliance with excisional margins of non-melanoma skin cancer

The rising incidence of Non Melanoma Skin Cancers (NMSC) leads to a high number of surgical procedures worldwide. The strict compliance with international guidelines with regard to excisional margins may help decrease the number of re-excision procedures and reduce the risk of NMSC recurrence. The aim of this study was to investigate the prevalence of excisional margins as recommended by the European Academy of Dermatology and Venereology (EADV) and the European Dermatology Forum (EDF) guidelines, and the factors (demographic or clinical) that influence surgeons' compliance with these guidelines.This was a prevalence study looking at surgical excisions of NMSCs performed over a period of 2 years (2011-2012). A sample size of 1669 patients was considered. Definition of excisional margins recommended by the international guidelines (EADV and EDF) were used as point of reference for the analysis. Tumor and histologic specimen size were calculated ex vivo by 5 different pathologists. The size of skin specimens was measured with a major axis and a minor axis. The same was done for the tumor present on the skin specimens. The differences between the major and minor axes of surgical specimen and tumor were calculated. These differences were subsequently divided by two, hypothesizing that the lesion had the same distance from the margins of the surgical specimen. The differences obtained were named "Delta", the formulas applied being the following:Delta major = (major axis specimen-major axis tumor)/2; Delta minor = (minor axis specimen-minor axis tumor)/2.Results show a significant statistical difference, associated with factors such as: age of the patient, anatomical localization of the tumor, histological diagnosis, and surgeons' experience.The identification of these factors sheds light on clinicians' practice and decision-making regarding excisional margins. Hopefully a higher level of adherence to the guidelines can be achieved in the future.

Split-Skin-Graft Wrapped Conformer to Treat Severe Contracted Sockets

This case series present the surgical management of cases with severe contracted sockets using a split-skin-graft wrapped conformer. Eight patients with severely contracted anophthalmic sockets underwent surgery. The surgical technique is described and a chart review was performed to collect patient data pre- and postoperatively. Preoperatively, all patients had grade 3 or 4 contracted sockets with shallow or obliterated fornices and patients were unable to retain an external prosthesis in place. Donor material was harvested from the supraclavicular area. The split-skin-graft was successfully performed in all cases without fornix-deepening sutures. All patients underwent a significant improvement of socket contracture enabling retention of the prosthesis and were satisfied with the outcomes. The split-skin-graft wrapped conformer is a rapid and less surgically challenging option to correct severe contracted anophthalmic sockets.

3D human skin bioprinting: a view from the bio side

Based on the 3D printing technologies and the concepts developed in tissue engineering during the last decades, 3D bioprinting is emerging as the most innovative and promising technology for the generation of human tissues and organs. In the case of skin bioprinting, thanks to the research process carried out during the last years, interfollicular skin has been printed with a structural and functional quality that paves the way for clinical and industrial applications. This review analyzes the present achievements and the future improvements that this area must bring about if bioprinted skin is to become widely used. We have made an effort to integrate the technological and the biological/biomedical sides of the subject.

Tie-Over Bolster Dressings vs Basting Sutures for the Closure of Full-Thickness Skin Grafts: A Review of the Literature

BACKGROUND

Full-thickness skin grafting is a well-established technique in the reconstruction of various tissue defects and wounds. However, lack of uniformity in the procedure of closing and securing the grafts has led to a wide range of different techniques.

OBJECTIVE

This article reviews the use of tie-over bolster dressings compared to basting sutures for the fixation and postsurgical immobilization of full-thickness skin grafts (FTSGs), discusses details of each method, and proposes a practice guideline for the closure of FTSGs.

METHODS

A traditional review of the literature was performed through a search of PubMed using the following keywords: full-thickness skin graft, FTSG, closure, suture, tie-over bolster, quilting, and bolster.

RESULTS

The current literature regarding tie-over bolster dressings does not demonstrate improved outcomes compared to quilting sutures. The 2 techniques appear equivalent in terms of utility and outcome, both possessing distinct advantages and disadvantages.

CONCLUSION

Despite minimal head-to-head studies between tie-over bolsters and quilting, the best evidence from the literature appears to show comparable results regarding graft take, cosmetic outcomes, and postoperative complications. Ultimately, the choice of using a tie-over bolster technique or quilting sutures relies on surgeon preference and anatomic location.

Adipose-derived stem cells improve full-thickness skin grafts in a rat model

To investigate the effects of heterologous adipose-derived stem cells (ADSCs) on autologous full-thickness skin grafts, we designed a first-intention healing model using Wistar rats. We harvested and sutured two full-thickness skin grafts in the dorsal recipient beds of 15 rats, randomized into three groups. In the treatment group, 1 × 10⁶ ADSCs resuspended in saline solution (200 μL) were administered subcutaneously to the skin graft. The control group received only saline solution subcutaneously, whereas the negative control group did not receive any treatment. Compressive dressings were maintained until postoperative day 5. The grafts were assessed by two observers, who checked for the presence of epidermolysis on day 14. Planimetry showed the relative areas of normal skin, redness, ulceration, and contraction. Graft samples were obtained on day 14 and stained with hematoxylin and eosin and Masson's trichrome. Epidermal analysis evaluated thickening, keratosis, acanthosis, hydropic degeneration, and inflammatory infiltrate. Dermal evaluation investigated the absence of hair follicles, granulation tissue formation, presence of inflammatory infiltrate, and collagen deposition. Immunohistochemistry was performed for dermal anti-VEGF and epidermal anti-Ki-67 staining. The ADSC group presented better macroscopic aspects, lower incidence of epidermolysis, and less loss of hair follicles. In addition, the ADSC group presented the lowest frequency of histopathological changes in the dermis and epidermis, as well as the largest subcutaneous and granulation tissue VEGF averages and the weakest Ki-67 staining of the epidermal basal layer. Subcutaneous administration of ADSCs may improve the integration of skin grafts, reducing the deleterious effects of ischemia and reperfusion injury.

3D Bioprinting Technologies for Tissue Engineering Applications

Three-dimensional (3D) printing (rapid prototyping or additive manufacturing) technologies have received significant attention in various fields over the past several decades. Tissue engineering applications of 3D bioprinting, in particular, have attracted the attention of many researchers. 3D scaffolds produced by the 3D bioprinting of biomaterials (bio-inks) enable the regeneration and restoration of various tissues and organs. These 3D bioprinting techniques are useful for fabricating scaffolds for biomedical and regenerative medicine and tissue engineering applications, permitting rapid manufacture with high-precision and control over size, porosity, and shape. In this review, we introduce a variety of tissue engineering applications to create bones, vascular, skin, cartilage, and neural structures using a variety of 3D bioprinting techniques.

Epidermal Stem Cells in Skin Wound Healing

Significance: Skin serves as a protective barrier for mammals. Epidermal stem cells are responsible for maintaining skin homeostasis. When cutaneous injuries occur, skin homeostasis and integrity are damaged, leading to dire consequences such as acute, chronic, or infected wounds. Skin wound healing is an intrinsic self-saving chain reaction, which is crucial to facilitating the replacement of damaged or lost tissue. Recent Advances: An immense amount of research has uncovered the underlying mechanisms behind the complex and highly regulated wound healing process. In this review, we will dissect the biological process of adult skin wound healing and emphasize the importance of epidermal stem cells during the wound healing. Critical Issues: We will comprehensively discuss the current clinical practices used on patients with cutaneous wounds, including both traditional skin grafting procedures and advanced grafting techniques with cultured skin stem cells. The majority of these leading techniques still retain some deficiencies during clinical use. Moreover, the regeneration of skin appendages after severe injuries remains a challenge in treatment. Future Directions: Understanding epidermal stem cells and their essential functions during skin wound healing are fundamental components behind the development of clinical treatment on patients with cutaneous wounds. It is important to improve the current standard of care and to develop novel techniques improving patient outcomes and long-term rehabilitation, which should be the goals of future endeavors in the field of skin wound healing.

Cross-linked Collagen Hydrogel Matrix Resisting Contraction To Facilitate Full-Thickness Skin Equivalents

Full-thickness skin equivalents are gathering increased interest as skin grafts for the treatment of large skin defects or chronic wounds or as nonanimal test platforms. However, their fibroblast-mediated contraction and poor mechanical stability lead to disadvantages toward their reproducibility and applicability in vitro and in vivo. To overcome these pitfalls, we aimed to chemically cross-link the dermal layer of a full-thickness skin model composed of a collagen type I hydrogel. Using a noncytotoxic four-arm succinimidyl glutarate polyethylene glycol (PEG-SG), cross-linking could be achieved in cell seeded collagen hydrogels. A concentration of 0.5 mg of PEG-SG/mg of collagen led to a viability comparable to non-cross-linked collagen hydrogels and no increased release of intracellular lactate dehydrogenase. Cross-linked collagen hydrogels were more mechanically stable and less prone to enzymatic degradation via collagenase when compared with non-cross-linked collagen hydrogels. Remarkably, during 21 days, cross-linked collagen hydrogels maintain their initial surface area, whereas standard dermal models contracted up to 50%. Finally, full-thickness skin equivalents were generated by seeding human epidermal keratinocytes on the surface of the equivalents and culturing these equivalents at an air-liquid interface. Immunohistochemical stainings of the cross-linked model revealed well-defined epidermal layers including an intact stratum corneum and a dermal part with homogeneously distributed human dermal fibroblasts. These results indicate that cross-linking of collagen with PEG-SG reduces contraction of collagen hydrogels and thus increases the applicability of these models as an additional tool for efficacy and safety assessment or a new generation of skin grafts.

Changes in histopathology and cytokeratin AE1/AE3 expression in skin graft with different time on Indonesian local cats

Aim:

A good skin graft histopathology is followed by formation of hair follicle, sweat gland, sebaceous gland, blood vessel, lightly dense connective tissue, epidermis, and dermis layer. This research aimed to observe histopathology feature and cytokeratin AE1/AE3 expression on cat skin post skin grafting within a different period of time.

Materials and Methods:

Nine male Indonesian local cats aged 1-2 years old weighing 3-4 kg were separated into three groups. First surgery created defect wound of 2 cm × 2 cm in size to whole groups. The wounds were left alone for several days, differing in interval between each group, respectively: Group I (for 2 days), Group II (for 4 days), and Group III (for 6 days). The second surgery was done to each group which harvested skin of thoracic area and applied it on recipient wound bed. On day 24^th post skin graft was an examination of histopathology and cytokeratin AE1/AE3 immunohistochemistry.

Results:

Group I donor skin’s epidermis layer had not formed completely whereas epidermis of donor skin of Groups II and III had completely formed. In all group hair follicle, sweat gland, sebaceous gland, and neovascularization were found. The density of connective tissue in Group I was very solid than other groups. Cytokeratin AE1/AE3 expression was found on donor skin’s epithelial cell in epidermis and dermis layer with very brown intensity for Group II, brown intensity for Group II, and lightly brown for Group I.

Conclusion:

Histopathological structure and cytokeratin AE1/AE3 expression post skin graft are better in Groups II and III compared to Group I.

Epitelização de enxertos cutâneos em feridas recentes de coelhos tratados com membrana amniótica canina e/ou laserterapia

RESUMO A enxertia cutânea é uma técnica cirúrgica simples e bastante útil para o reparo de feridas, principalmente aquelas onde existe dificuldade da aplicação do fechamento primário ou de outras técnicas reconstrutivas. Entretanto, para a sobrevivência do enxerto, é necessário que o leito da ferida esteja saudável e com presença de tecido de granulação exuberante. O objetivo do presente trabalho foi avaliar a aplicação da membrana amniótica e da laserterapia como potenciais estimulantes da cicatrização em enxertos aplicados em feridas sem tecido de granulação. Foram utilizados 42 coelhos, divididos em quatro grupos: grupo controle (GC), grupo membrana (GM), grupo laser (GL) e grupo membrana e laser (GML), submetidos a avaliações macro e microscópicas. Na avaliação macroscópica, foi possível notar que os pacientes dos grupos nos quais a membrana amniótica foi utilizada (GM e GML) apresentaram evidências associadas à acentuada reação inflamatória, à falha de integração do enxerto e à consequente necrose dele. Já os pacientes do GL apresentaram melhor aspecto do enxerto no último dia de avaliação. Na análise microscópica, observou-se intensa integração do enxerto à derme, reepitelização acentuada e escassas células inflamatórias no local do enxerto no GL. O contrário foi observado nos pacientes do GM e GML, nos quais aparentemente houve rejeição da membrana. A formação de colágeno não se correlacionou com outros fatores, como inflamação e necrose, em nenhum dos grupos de tratamento. Dessa forma, é possível afirmar que a laserterapia mostrou ser efetiva, contribuindo para o processo cicatricial e a integração do enxerto. Já a membrana amniótica canina não deve ser utilizada para esse fim, pois provoca intensa reação inflamatória, além de impedir a nutrição do enxerto.