Epidermal grafting for wound healing: a review on the harvesting systems, the ultrastructure of the graft and the mechanism of wound healing

Hydrogel dressings for donor sites of split-thickness skin grafts

BACKGROUND

Donor site wounds of split-thickness skin grafts can be a major cause of morbidity. Choosing the appropriate dressing for these wounds is crucial to successful healing. Various types of dressing are available, including hydrogel dressings. A review of current evidence is required to guide clinical decision-making on the choice of dressing for the treatment of donor sites of split-thickness skin grafts.

OBJECTIVES

To assess the effects of hydrogel dressings on donor site wounds following split-thickness skin grafts for wound healing.

SEARCH METHODS

In July 2022 we searched the Cochrane Wounds Specialised Register, CENTRAL, MEDLINE, Embase, and CINAHL EBSCO Plus. We also searched clinical trials registries for ongoing and unpublished studies, and scanned reference lists of relevant included studies as well as reviews, meta-analyses, and health technology reports to identify additional studies. There were no restrictions with respect to language, date of publication, or study setting.

SELECTION CRITERIA

Randomised controlled trials (RCTs) comparing hydrogel dressings with other types of dressing, topical treatments or no dressing, or with different types of hydrogel dressings in managing donor site wounds irrespective of language and publication status.

DATA COLLECTION AND ANALYSIS

Two review authors independently carried out data extraction, risk of bias assessment using the Cochrane risk of bias tool, RoB 1, and quality assessment according to GRADE methodology.

MAIN RESULTS

We included two studies (162 participants) in this review. One study with three arms and 101 participants (15 months' duration) was conducted in a children's hospital, and compared hydrogel dressings in the form of Sorbact with Algisite, an alginate dressing and Cuticerin, a smooth acetate gauze impregnated with water-repellent ointment. Another study with two arms and 61 participants (19 months' duration) was conducted in three surgery departments and compared an octenidine-containing hydrogel dressing with an identical non-antimicrobial hydrogel dressing. We identified no studies that compared hydrogel dressings with another therapy such as a topical agent (a topical agent is a cream, an ointment or a solution that is applied directly to the wound), or no dressing, or a combination of hydrogel dressings and another therapy versus another therapy alone. Both studies were at high risk of attrition bias and the second study was also at unclear risk of selection bias. Amorphous hydrogel dressings versus other types of dressings Amorphous hydrogel dressings may increase time to wound healing when compared with alginate (mean difference (MD) 1.67 days, 95% confidence interval (CI) 0.56 to 2.78; 1 study, 69 participants; low-certainty evidence) or Cuticerin dressings (MD 1.67 days, 95% CI 0.55 to 2.79; 1 study, 68 participants; low-certainty evidence). The effect of amorphous hydrogel dressings compared with other types of dressings is uncertain for pain at the donor site and wound complications, including scarring and itching (very low-certainty evidence). No adverse events were reported in any of the groups. The study did not report health-related quality of life or wound infection. Octenidine-based hydrogel dressing versus octenidine-free hydrogel dressing The effect of octenidine-based hydrogel dressings versus octenidine-free hydrogel dressings is uncertain for time to wound healing (MD 0.40, 95% CI 0.28 to 0.52; 1 study, 41 participants) and wound infection, as the certainty of the evidence is very low. The certainty of the evidence is also very low for adverse events, with two participants in the intervention group and one participant in the comparison group reporting adverse events (risk ratio (RR) 0.58, 95% CI 0.06 to 5.89; 1 study, 41 participants). The study did not report donor site pain, health-related quality of life, or wound complications.

AUTHORS' CONCLUSIONS

There is insufficient evidence to determine the effect of hydrogel dressings on donor site wounds of split thickness skin grafts compared with other types of dressings. There is a need for adequately powered and well-designed RCTs, with adequate sample sizes, types of populations and subgroups, types of interventions, and outcomes, that compare hydrogel dressings with other treatment options in the treatment of donor site wounds of split-thickness skin grafts.

Photobiomodulation with Blue Light on Wound Healing: A Scoping Review

BACKGROUND

Photobiomodulation consists of inducing healing by irradiating light. This scoping review investigates the effect of blue light on the healing process.

METHODS

The MEDLINE, Web of Science, Scopus, and CINAHL databases were searched. Two reviewers independently examined the search results and extracted data from the included studies. A descriptive analysis was performed.

RESULTS

Twenty-two articles were included. Studies were categorized as in vitro/mixed, preclinical, and clinical. The power density used was 10-680 mW/cm2 in most of the in vitro/preclinical studies, the irradiation time ranged from 5 s to 10 min, and different wavelengths and energy densities were used. In clinical studies, the wavelength ranged from 405 to 470 nm, and the energy density varied from 1.5 to 30 J/cm2.

CONCLUSIONS

A low energy density (<20 J/cm2) was able to stimulate the different cell types and proteins involved in healing, while a high energy density, 20.6-50 J/cm2, significantly reduced cell proliferation, migration, and metabolism. There is a great variety of device parameters among studies, and this makes it difficult to conclude what the best technical specifications are. Thus, further studies should be performed in order to define the appropriate parameters of light to be used.

Epidermal/Dermal Separation Techniques and Analysis of Cell Populations in Human Skin Sheets

Human skin consists of three compartments, each endowed with a particular structure and the presence of several immune and nonimmune cells that together comprise a protective shield and orchestrate multiple processes in the skin. Appropriate processing of human skin samples acquired from healthy volunteers or patients is essential for successful analysis in basic, translational, and clinical research to obtain accurate and reliable results, despite differences between individuals. From the wide range of available assays and methods, it is necessary to select the suitable method for separation of skin compartments, which will provide preservation or high viability of skin cells or whole structures that will be analyzed or further processed. In this paper, we review and discuss skin separation methods and compare their features such as processing time, cell viability, location of the basement membrane after detachment of the epidermis from the dermis, and their application. Furthermore, we visualize different cell populations and structures in epidermal and dermal sheets using confocal microscopy. It is aimed to provide an overview of the optimal processing of human skin samples and their possible application.

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.

Wound healing: potential therapeutic options

This review highlights the range of therapeutic options available to clinicians treating difficult-to-heal wounds. While certain treatments are established in daily clinical practice, most therapeutic interventions lack robust and rigorous data regarding their efficacy, which would help to determine when, and for whom, they should be used. The purpose of this review is to give a broad overview of the available interventions, with a brief summary of the evidence base for each intervention.

Creation of skin grafts from traumatic avulsed skin

As the proportion of geriatric patients increases, so too does the incidence of geriatric trauma. Trauma centres must develop protocols to reduce the risk of complications from injuries in this specialised patient population. From a soft tissue standpoint, open wounds tend to heal slower in these patients and have a significant impact on their quality of life. In this case report, we describe our protocol for managing traumatic skin tears using a combination of traumatic skin grafts and minced expansion grafts with photographic documentation of the healing from significant wounds in an elderly patient involved in a high-energy blunt traumatic injury.

Collagen/glycosaminoglycan-based matrices for controlling skin cell responses

Wound healing and tissue regeneration are orchestrated by the cellular microenvironment, e.g. the extracellular matrix (ECM). Including ECM components in biomaterials is a promising approach for improving regenerative processes, e.g. wound healing in skin. This review addresses recent findings for enhanced epidermal-dermal regenerative processes on collagen (coll)/glycosaminoglycan (GAG)-based matrices containing sulfated GAG (sGAG) in simple and complex in vitro models. These matrices comprise 2D-coatings, electrospun nanofibrous scaffolds, and photo-crosslinked acrylated hyaluronan (HA-AC)/coll-based hydrogels. They demonstrated to regulate keratinocyte and fibroblast migration and growth, to stimulate melanogenesis in melanocytes from the outer root sheath (ORS) of hair follicles and to enhance the epithelial differentiation of human mesenchymal stem cells (hMSC). The matrices' suitability for delivery of relevant growth factors, like heparin-binding epidermal growth factor like growth factor (HB-EGF), further highlights their potential as bioinspired, functional microenvironments for enhancing skin regeneration.

How I treat anticoagulant-refractory thrombotic antiphospholipid syndrome

The standard treatment of thrombotic antiphospholipid syndrome (APS) is lifelong oral anticoagulation with a vitamin K antagonist (VKA), generally warfarin. A minority of patients with APS rethrombose despite seemingly adequate anticoagulation. These patients are deemed anticoagulant refractory. The management of anticoagulant-refractory APS is largely empirical and extrapolated from other clinically similar situations. Further options include increased VKA anticoagulation intensity or alternative antithrombotic strategies, including low-molecular-weight heparin, fondaparinux, the addition of antiplatelet therapy, and consideration of vascular options. Patients with anticoagulant-refractory thrombotic APS may have APS-associated thrombocytopenia, which necessitates balancing the risk of recurrent thrombosis vs bleeding to achieve adequate anticoagulation. The multiple mechanisms involved in the generation of the thrombotic phenotype in APS suggest that anticoagulation alone may not control thrombosis. Thus, other modalities, including adjunctive treatment (hydroxychloroquine, statins, and vitamin D) for APS-related thrombosis, merit consideration, as do immunomodulatory therapy and complement inhibition. Patients with APS may have coexistent systemic lupus erythematosus, which adds to the complexity of managing their thromboembolic disease. However, with attention to detail and judicious application of the limited data, it is possible to minimize the morbidity resulting from anticoagulant-refractory thrombotic APS. Multicenter studies are required to guide the sequence of interventions and their comparative efficacy in patients with anticoagulant-refractory thrombotic APS.

Epidermal graft encourages wound healing by down-regulation of gap junctional protein and activation of wound bed without graft integration as opposed to split-thickness skin graft

Wound coverage by split-thickness skin graft (SSG) and epidermal graft (EG) shortens healing time, with comparable outcomes. However, the healing mechanism of EG is not as well understood as SSG. The difference in the healing mechanisms of EG and SSG was investigated using gap junctional proteins, proliferative marker, and cytokeratin markers. Paired punch biopsies were taken from the wound edge and wound bed from patients undergoing EG and SSG at weeks 0 and 1 to investigate wound edge keratinocyte migratory activities (connexins 43, 30, and 26), wound bed activation (Ki67), and the presence of graft integration to the wound bed (cytokeratins 14 and 6). Twenty-four paired biopsies were taken at weeks 0 and 1 (EG, n = 12; SSG, n = 12). Wound edge biopsies demonstrated down-regulation of connexins 43 (P = .023) and 30 (P = .027) after EG, indicating accelerated healing from the wound edge. At week 1, increased expression of Ki67 (P < .05) was seen after EG, indicating activation of cells within the wound bed. Keratinocytes expressing cytokeratins 6 and 14 were observed on all wounds treated with SSG but were absent at week 1 after EG, indicating the absence of graft integration following EG. Despite EG and SSG both being autologous skin grafts, they demonstrate different mechanisms of wound healing. EG accelerates wound healing from the wound edges and activates the wound bed despite not integrating into the wound bed at week 1 post-grafting as opposed to SSG, hence demonstrating properties comparable with a bioactive dressing instead of a skin substitute.

Quantitative Outcome Assessment of Color Match and the Extent of Repigmentation after Pixel Array Epidermal Grafting for Head and Neck Stable Vitiligo: A Prospective Cohort Study

BACKGROUND

Epidermal grafting with an automatic harvesting system has been reported as a simple and efficacious procedure for stable vitiligo. However, no prospective cohort study has quantitatively evaluated the color matching and extent of repigmentation in the head and neck area by this method.

OBJECTIVE

To evaluate the color matching and extent of repigmentation after pixel array epidermal grafting by image analysis software and physicians' naked eye.

METHODS

Ten Asian patients with head and neck vitiligo lesions stable for at least 6 months were treated with pixel array epidermal grafting with an automatic harvesting system and post-grafting phototherapy. The patients were evaluated 1, 3, and 6 months post grafting for the percentage of repigmentation by blinded physicians' assessment and image analysis software. The color matching index of repigmentation was evaluated by measuring the melanin index in the grafted area and the juxta non-vitiliginous area.

RESULTS

The average blister harvest time was 46.3 ± 9.7 min. The area percentile of repigmentation by the image analysis software were 32.3 ± 26.8, 64.6 ± 29.4, and 76.5 ± 25.9 at 1, 3, and 6 months post grafting, respectively. There were no significant differences between the physicians' assessments and the results from the image analysis software. The change in the area percentile of repigmentation between 3 and 6 months post grafting was only statistically significant using image analysis software. The grafted area achieved a color match of 83.1 ± 13.4% that of the juxta non-vitiliginous area 6 months after grafting. Three patients had repigmentation of leukotrichia.

CONCLUSION

By quantitative measurement, uniform pixel array micrografts provide a very good extent of repigmentation and color match in the head and neck area. Image analysis software revealed a steady increase in repigmentation after POM3 until POM6, which was not detected by subjective assessment.

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.

Lower donor site morbidity and higher patient satisfaction with epidermal grafting in comparison to split thickness skin grafting: A randomized controlled trial (EPIGRAAFT Trial)

BACKGROUND

Split thickness skin grafting (SSG) is an important modality for wound coverage; however, it leads to donor site morbidity. Epidermal grafting (EG) is a promising option for autologous skin grafting which offers minimal donor site morbidity, though it is not known if EG is an effective clinical alternative for SSG. This study compared the efficacy of EG as an alternative to SSG in terms of wound healing outcomes, donor site morbidity, patient satisfaction and adverse events.

METHODS

EPIGRAAFT is a Phase 2, randomized, open-label trial with two parallel groups: EG and SSG. Patients referred for skin grafting with a healthy granulating wound bed were included. The co-primary endpoints were the proportion of wounds healed and donor site healing time. The secondary endpoints include donor site morbidity measured using Vancouver Scar Scale, mean time for complete wound healing, patient satisfaction assessed using a validated skin grafting questionnaire and incidence of adverse events.

RESULTS

Of the 61 patients screened, 44 patients were randomized. There was no difference in the proportion of wounds healed at 6 weeks (p=0.366) and 3 months(p=0.24) as well as the mean time for wound healing (p=0.12). EG resulted in lower donor site morbidity (p=0.001), faster donor site healing time (EG: 4.86 days vs. SSG: 21.32 days) (p<0.0001), and higher overall satisfaction (p<0.001). There were no adverse events reported.

CONCLUSION

This study demonstrated that EG has superior donor site outcomes with faster donor site healing and lower morbidity compared to SSG, while having comparable wound healing outcomes. Patients receiving EG also experienced higher donor site satisfaction compared to SSG. ClinicalTrials.gov identifier: NCT02535481.

Biomaterials and engineered microenvironments to control YAP/TAZ-dependent cell behaviour

Mechanical signals are increasingly recognized as overarching regulators of cell behaviour, controlling stemness, organoid biology, tissue development and regeneration. Moreover, aberrant mechanotransduction is a driver of disease, including cancer, fibrosis and cardiovascular defects. A central question remains how cells compute a host of biomechanical signals into meaningful biological behaviours. Biomaterials and microfabrication technologies are essential to address this issue. Here we review a large body of evidence that connects diverse biomaterial-based systems to the functions of YAP/TAZ, two highly related mechanosensitive transcriptional regulators. YAP/TAZ orchestrate the response to a suite of engineered microenviroments, emerging as a universal control system for cells in two and three dimensions, in static or dynamic fashions, over a range of elastic and viscoelastic stimuli, from solid to fluid states. This approach may guide the rational design of technological and material-based platforms with dramatically improved functionalities and inform the generation of new biomaterials for regenerative medicine applications.

Comparative study on the donor site aesthetic outcome between epidermal graft and split-thickness skin graft

Donor site aesthetic outcomes of epidermal graft (EG) vs split-thickness skin graft (SSG) have yet to be objectively compared. Here, we evaluate donor site healing using a validated scar assessment tool and digital colorimetric technique, which compares colour in a consistent and objective manner. Ten patients (SSG (n = 5) and EG (n = 5)) were included. Donor site scarring was evaluated using the Vancouver Scar Scale (VSS) at Week 6 and Month 3. Colorimetric measurement was performed at Weeks 3 and 6 and Month 3. The mean donor site healing time for EG was significantly shorter (EG: 4.6 days (95% c.i. 3.8-5.3), SSG: 16.8 days (95% c.i. 13.3-20.1) (P = 0.003)). The VSS scores of the EG donor site were lower at Week 6 and Month 3(P < 0.001). The colour match between the donor site and surrounding skin for EG was better compared with SSG at all time points and was almost identical to their surrounding healthy skin at Month 3. This study is the first to objectively measure the clinical appearance of the EG donor site against SSG. EG donor site has faster healing with excellent scarring and good colour match with its surrounding normal skin at all time points compared with SSG.

Delivery systems of current biologicals for the treatment of chronic cutaneous wounds and severe burns

While wound therapy remains a clinical challenge in current medical practice, much effort has focused on developing biological therapeutic approaches. This paper presents a comprehensive review of delivery systems for current biologicals for the treatment of chronic wounds and severe burns. The biologicals discussed here include proteins such as growth factors and gene modifying molecules, which may be delivered to wounds free, encapsulated, or released from living systems (cells, skin grafts or skin equivalents) or biomaterials. Advances in biomaterial science and technologies have enabled the synthesis of delivery systems such as scaffolds, hydrogels and nanoparticles, designed to not only allow spatially and temporally controlled release of biologicals, but to also emulate the natural extracellular matrix microenvironment. These technologies represent an attractive field for regenerative wound therapy, by offering more personalised and effective treatments.

Stem cells, niches and scaffolds: Applications to burns and wound care

The importance of skin to survival, and the devastating physical and psychological consequences of scarring following reparative healing of extensive or difficult to heal human wounds, cannot be disputed. We discuss the significant challenges faced by patients and healthcare providers alike in treating these wounds. New state of the art technologies have provided remarkable insights into the role of skin stem and progenitor cells and their niches in maintaining skin homeostasis and in reparative wound healing. Based on this knowledge, we examine different approaches to repair extensive burn injury and chronic wounds, including full and split thickness skin grafts, temporising matrices and scaffolds, and composite cultured skin products. Notable developments include next generation skin substitutes to replace split thickness skin autografts and next generation gene editing coupled with cell therapies to treat genodermatoses. Further refinements are predicted with the advent of bioprinting technologies, and newly defined biomaterials and autologous cell sources that can be engineered to more accurately replicate human skin architecture, function and cosmesis. These advances will undoubtedly improve quality of life for patients with extensive burns and difficult to heal wounds.