Clinical practice of glycerol preserved allograft skin coverage

Historical Evolution of Skin Grafting-A Journey through Time

Autologous skin grafting was developed more than 3500 years ago. Several approaches and techniques have been discovered and established in burn care since then. Great achievements were made during the 19th and 20th century. Many of these techniques are still part of the surgical burn care. Today, autologous skin grafting is still considered to be the gold standard for burn wound coverage. The present paper gives an overview about the evolution of skin grafting and its usage in burn care nowadays.

How to improve donor skin availability: Pragmatic procedures to minimize the discard rate of cryopreserved allografts in skin banking

BACKGROUND

Microbial contamination of human skin allografts is a frequent cause of allograft discard. Our purpose was to evaluate the discard rate of skin bank contaminated allografts and specific procedures used to reduce allograft contamination without affecting safety.

METHODS

We conducted at the Lille Tissue Bank a retrospective study of all deceased donors (n = 104) harvested from January 2018 to December 2018. Skin procurement was split into 3 zones: the back of the body and the two legs that were processed separately. It represented 433 cryopreserved skin allograft pouches of approximatively 500 cm² each. Donors were almost equally split between brain-dead (53%, 55/104) and cadaveric (47%, 49/104) donors.

RESULTS

Out of all donors, 42 (40.5%) had at least one sampling zone with a positive microbiological test resulting in 106 (24%) contaminated skin pouches. The contamination rate did not vary according to the harvested zone or type of donor. Traumatic deaths showed significantly less contamination rates than other death types (p < 0.05). Contamination rate decreased with time spent in the antibiotic solution. The risk of having contaminated allografts was five-fold higher when the skin spent less than 96 h in the antibiotic cocktail (p < 0.05). According to our validation protocol, most donors (32/42, 76%) had skin allografts contaminated with bacteria (mainly Staphylococcus spp) compatible with clinical use. No recipient infection was recorded as a result of skin graft contaminated with saprophytic or non-pathogenic germs. By harvesting 3 separate zones per donor, the total surface area for clinical use increased by 53% for contaminated donors. Overall, the proportion of contamination-related discarded allografts was 3.2% (14/433 of pouches).

CONCLUSION

Few simple pragmatic measures (including skin incubation in the antibiotic bath for at least 96 h at 4 °C, splitting the skin harvesting areas to minimize the risk of cross-infection and clinical use of allografts contaminated with saprophytic and non-pathogenic germs) can reduce the discard rate of contaminated allografts without affecting clinical safety.

Lessons Learned From Implementation and Management of Skin Allograft Banking Programs in Low- and Middle-Income Countries: A Systematic Review

Wound excision and temporary coverage with a biologic dressing can improve survival for patients with large burns. Healthcare systems in low- and middle-income countries (LMICs) rarely have access to allografts, which may contribute to the limited survival of patients with large burns in these settings. Therefore, we aimed to describe the lessons learned from the implementation and maintenance of tissue banks in LMICs to guide system planning and organization. PubMed, MEDLINE, CINAHL, and World Health Organization Catalog were systematically searched with database-specific language to represent a priori terms (eg, skin, allograft, and tissue bank) and all LMICs as defined by the World Bank. Data regarding tissue banking programs were extracted and described in a narrative synthesis. The search returned 3346 records, and 33 reports from 17 countries were analyzed. Commonly reported barriers to ideal or planned implementation included high capital costs and operational costs per graft, insufficient training opportunities, opt-in donation schemes, and sociocultural stigma around donation and transplantation. Many lessons were learned from the implementation and management of tissue banks around the world. The availability of skin allografts can be improved through strategic investments in governance and regulatory structures, international cooperation initiatives, training programs, standardized protocols, and inclusive public awareness campaigns. Furthermore, capacity-building efforts that involve key stakeholders may increase rates of pledges, donations, and transplantations. Some issues were ubiquitously reported and could be addressed by current and future tissue banking programs to ensure allograft availability for patients living in countries of all income levels.

Is allograft skin, the gold-standard for burn skin substitute? A systematic literature review and meta-analysis

BACKGROUND

Allograft skin (AS) transplantation has been considered to be the gold standard for replacing tissue damage, following burns. However, increasingly new biosynthetic skin substitutes are being developed as alternatives. The objective of this systematic review is to compare AS with other skin substitutes, which have been used in the treatment of burns.

METHODS

Randomized clinical trial (RCT) and nonrandomized clinical trial (NRCT) studies comparing AS to any other skin substitute in the treatment of burns were extracted from PubMed/Medline, Scopus, EMBASE, and Web of Science. For the risk of bias analysis, the Cochrane bias risk handbook was used for RCT studies and ROBINS-1 was used for NRCT studies. Outcomes such as healing, self-grafting, scar appearance, and mortality were evaluated.

RESULTS

Twelve RCT and six NRCT were selected, with most of the methodologies presenting a high risk of bias. Based on the outcomes of the studies, it was not possible to detect any advantages for using AS, as opposed to other skin substitutes. In the meta-analysis, only two outcomes could be evaluated: healing and graft take percentage; however, no significant differences were observed between the groups.

CONCLUSION

Because of the poor quality of the primary studies, it was not possible to identify differences in the results that compared the use of AS with other substitutes in the treatment of patients with burns. These results support the fact that surgeons primarily base the choice of skin substitute on clinical experience and cost, at least when treating burns.

Comparison of different skin preservation methods with gamma irradiation

Allografts are in constant demand, not only for burn victims, but also for all open wounds as "biological dressings". Tissue quality and security are two of the major concerns of Tissue Banks. There are limited studies published. There has been extensive discussion on the subject of preservation methods for cadaver skin. Most literature available comes from clinical reports. In this research, the authors compared 85% glycerolized non irradiated skin allografts with three glycerolized irradiated skin allografts (using different glycerol concentrations 50%, 70% and 85%). The evaluation of allograft quality was done by measuring physical and biological properties of such prepared human tissue grafts. In the histological structure evaluation changes were minimal and did not alter the skin structure. The clinical function of their behavior as temporal dressings was tested. They proved to have similar capabilities for improving granulating tissue and contributing to wound beds closure (Hickerson et al. (1994) [1]).

Chronological histological findings of cultured epidermal autograft over bilayer artificial dermis

The application of cultured epidermal autograft (CEA) over bilayer artificial dermis theoretically should minimize surgical stress and donor site morbidity in severe burn patients. However, CEA over regenerated dermis is very fragile and easily detaches soon after application, because the very weak attachment. We performed chronological histological studies of the wounds of a 29 year-old patient, which was reconstructed using CEA (JACE(®)) and bilayer artificial dermis (Integra™). These studies included immunohistochemistry of anti-collagen (types III, IV, and VII) and anti-laminin, in addition to H&E and EVG staining. Reconstructed epidermis and dermis showed almost normal histological appearance with time, but formation of basement membrane proteins was delayed. Absent or immature basement membrane protein in the early phase after the CEA application was considered to be an important problem. In the late phase after the CEA application over the bilayer artificial dermis, the reconstructed skin was very durable and demonstrated no sign of skin stripping (although there was still a lack of basement membrane proteins).

Functional characterization of cultured keratinocytes after acute cutaneous burn injury

Background

In addition to forming the epithelial barrier against the outside environment keratinocytes are immunologically active cells. In the treatment of severely burned skin, cryoconserved keratinocyte allografts gain in importance. It has been proposed that these allografts accelerate wound healing also due to the expression of a favourable - keratinocyte-derived - cytokine and growth factor milieu.

Methods

In this study the morphology and cytokine expression profile of keratinocytes from skin after acute burn injury was compared to non-burned skin. Skin samples were obtained from patients after severe burn injury and healthy controls. Cells were cultured and secretion of selected inflammatory mediators was quantified using Bioplex Immunoassays. Immunohistochemistry was performed to analyse further functional and morphologic parameters.

Results

Histology revealed increased terminal differentiation of keratinocytes (CK10, CK11) in allografts from non-burned skin compared to a higher portion of proliferative cells (CK5, vimentin) in acute burn injury. Increased levels of IL-1α, IL-2, IL-4, IL-10, IFN-γ and TNFα could be detected in culture media of burn injury skin cultures. Both culture groups contained large amounts of IL-1RA. IL-6 and GM-CSF were increased during the first 15 days of culture of burned skin compared to control skin. Levels of VEGF, FGF-basic, TGF-ß und G-CSF were high in both but not significantly different. Cryoconservation led to a diminished mediator synthesis except for higher levels of intracellular IL-1α and IL-1ß.

Conclusion

Skin allografts from non-burned skin show a different secretion pattern of keratinocyte-derived cytokines and inflammatory mediators compared to keratinocytes after burn injury. As these secreted molecules exert auto- and paracrine effects and subsequently contribute to healing and barrier restoration after acute burn injury therapies affecting this specific cytokine/growth factor micromilieu could be beneficial in burned patients.

Deceased donor skin allograft banking: Response and utilization

Background:

In the absence of xenograft and biosynthetic skin substitutes, deceased donor skin allografts is a feasible option for saving life of patient with extensive burn injury in our country.

Aims:

The first deceased donor skin allograft bank in India became functional at Lokmanya Tilak Municipal (LTM) medical college and hospital on 24^th April 2000. The response of Indian society to this new concept of skin donation after death and the pattern of utilization of banked allografts from 2000 to 2010 has been presented in this study.

Settings and Design:

This allograft skin bank was established by the department of surgery. The departments of surgery and microbiology share the responsibility of smooth functioning of the bank. Materials and Methods: The response in terms of number of donations and the profile of donors was analyzed from records. Pattern and outcome of allograft utilization was studied from specially designed forms.

Results:

During these ten years, 262 deceased donor skin allograft donations were received. The response showed significant improvement after counselling was extended to the community. Majority of the donors were above 70 years of age and procurement was done at home for most. Skin allografts from 249 donors were used for 165 patients in ten years. The outcome was encouraging with seven deaths in 151 recipients with burn injuries.

Conclusions:

Our experience shows that the Indian society is ready to accept the concept of skin donation after death. Use of skin allografts is life saving for large burns. We need to prepare guidelines for the establishment of more skin banks in the country.

Combined gene and stem cell therapy for cutaneous wound healing

In current medical practice, wound therapy remains a clinical challenge and much effort has been focused on the development of novel therapeutic approaches for wound treatment. Gene therapy, initially developed for treatment of congenital defects, represents a promising option for enhancing wound repair. In order to accelerate wound closure, genes encoding for growth factors or cytokines have shown the most potential. The majority of gene delivery systems are based on viral transfection, naked DNA application, high pressure injection, and liposomal vectors. Besides advances stemming from breakthroughs in recombinant growth factors and bioengineered skin, there has been a significant increase in the understanding of stem cell biology in the field of cutaneous wound healing. A variety of sources, such as bone marrow, umbilical cord blood, adipose tissue and skin/hair follicles, have been utilized to isolate stem cells and to modulate the healing response of acute and chronic wounds. Recent data have demonstrated the feasibility of autologous adult stem cell therapy in cutaneous repair and regeneration. Very recently, stem cell based skin engineering in conjunction with gene recombination, in which the stem cells act as both the seed cells and the vehicle for gene delivery to the wound site, represents the most attractive field for generating a regenerative strategy for wound therapy. The aim of this article is to discuss the use and the potential of these novel technologies in order to improve wound healing capacities.

The use of human deceased donor skin allograft in burn care

Burns are tissue wounds caused by thermal, electrical, chemical cold or radiation injuries. Deep injuries lead to dermal damage that impairs the ability of the skin to heal and regenerate on its own. Skin autografting following burn excision is considered the current gold standard of care, but lack of patient's own donor skin or unsuitability of the wound for autografting may require the temporary use of dressings or skin substitutes to promote wound healing, reduce pain, and prevent infection and abnormal scarring. These alternatives include deceased donor skin allograft, xenograft, cultured epithelial cells and biosynthetic skin substitutes. Allotransplantation is the transplantation of cells, tissues, or organs, sourced from a genetically non-identical member of the same species as the recipient. Human deceased donor skin allografts represent a suitable and much used temporizing option for skin cover following burn injury. The main advantages for its use include dermoprotection and promotion of reepithelialisation of the wound and their ability to act as skin cover until autografting is possible or re-harvesting of donor sites becomes available. Disadvantages of its use include the limited abundance and availability of donors, possible transmission of disease, the eventual rejection by the host and its handling storing, transporting and associated costs of provision. This paper will explore the role of allograft skin in burn care, defining the indications for its use in burn management and the future potential for allograft tissue banking.

Human embryonic stem-cell derivatives for full reconstruction of the pluristratified epidermis: a preclinical study

BACKGROUND

Cell therapy for large burns is dependent upon autologous epidermis reconstructed in vitro. However, the effectiveness of current procedures is limited by the delay needed to culture the patient's own keratinocytes. To assess whether the keratinocyte progeny of human embryonic stem cells (hESCs) could be used to form a temporary skin substitute for use in patients awaiting autologous grafts, we investigated the cells' capability of constructing a pluristratified epidermis.

METHODS

hESCs from lines H9 and SA01 were seeded at least in triplicate on fibroblast feeder cells for 40 days in a medium supplemented with bone morphogenetic protein 4 and ascorbic acid. Molecular characterisation of cell differentiation was done throughout the process by quantitative PCR, fluorescence-activated cell sorting, and immunocytochemical techniques. Keratinocyte molecular differentiation and functional capacity to construct a human epidermis were assessed in vitro and in vivo.

FINDINGS

From hESCs, we generated a homogeneous population of cells that showed phenotypic characteristics of basal keratinocytes. Expression levels of genes encoding keratin 14, keratin 5, integrin alpha6, integrin beta4, collagen VII, and laminin 5 in these cells were similar to those in basal keratinocytes. After seeding on an artificial matrix, keratinocytes derived from hESCs (K-hESCs) formed a pluristratified epidermis. Keratin-14 immunostaining was seen in the basal compartment, with keratin 10 present in layers overlying the basal layer. Involucrin and filaggrin, late markers of epidermal differentiation, were detected in the uppermost layers only. 12 weeks after grafting onto five immunodeficient mice, epidermis derived from K-hESCs had a structure consistent with that of mature human skin. Human involucrin was appropriately located in spinous and granular layers and few Ki67-positive cells were detected in the basal layer.

INTERPRETATION

hESCs can be differentiated into basal keratinocytes that are fully functional--ie, able to construct a pluristratified epidermis. This resource could be developed to provide temporary skin substitutes for patients awaiting autologous grafts.

FUNDING

Institut National de la Santé et de la Recherche Médicale, University Evry Val d'Essonne, Association Française contre les Myopathies, Fondation René Touraine, and Genopole.

The versatility of a glycerol-preserved skin allograft as an adjunctive treatment to free flap reconstruction

Skin allografts have been used in medical practice for over a century owing to their unique composition as a biological dressing. Skin allografts can be obtained in several preparations such as cryopreserved, glycerol-preserved, and fresh allograft. A glycerol-preserved allograft (GPA) was introduced in the early 1980s. It has several advantages compared with other dressings such as ease of processing, storage and transport, lower cost, less antigenicity, antimicrobial properties, and neo-vascularisation promoting properties. Skin allografts are mainly used in the management of severe burn injuries, chronic ulcers, and complex, traumatic wounds. Published reports of the use of skin allografts in association with free flap surgery are few or non existent. We would like to share our experience of several cases of free tissue transfer that utilised GPA as a temporary wound dressing in multiple scenarios. On the basis of this case series, we would like to recommend that a GPA be used as a temporary dressing in conjunction with free flap surgery when required to protect the flap pedicle, allowing time for the edema to subside and the wound can then be closed for a better aesthetic outcome.

Emergency treatment of severely burned pediatric patients: current therapeutic strategies

Burn trauma represents a devastating injury and remains as one of the leading causes of mortality and morbidity in children. Effective prevention strategies, advances in therapeutic techniques, based on an improved understanding of fluid resuscitation, appropriate infection control and improved treatment of inhalation injury, enhanced wound coverage, better nutritional regimens, advanced support of the hypermetabolic response to injury and improved glucose control, have significantly improved the clinical outcome of this unique patient population over the past years. This article aims to outline the current and emerging therapeutic strategies for the treatment of severely burned pediatric patients in the emergency department or initial phase of the intensive care unit.

Longitudinal assessment of Integra in primary burn management: A randomized pediatric clinical trial*

BACKGROUND

Early excision with autograft-allograft closure is standard in severe burn management. Cadaver skin is associated with risks such as antigenicity, infection, and limited availability and shelf life. Previous studies have shown that Integra is safe to use in burns of <20% total body surface area. However, the suitability of its use in large burns (>50% total body surface area), its effects on postburn hypermetabolism, and the long-term cosmetic and functional results have not yet been evaluated.

MATERIALS AND METHODS

Twenty children with an average burn size of 73 +/- 15% total body surface area (71 +/- 15% full-thickness burn) were randomized to be treated with either Integra or with autograft-allograft technique. Outcome measures such as length of hospital stay, mortality, incidence of infection and sepsis, acute phase protein levels, and muscle fractional synthetic rate were compared between and within groups during the acute stay (admission to discharge). Outcome measures such as resting energy expenditure, body composition data (measured by dual-energy radiograph absorptiometry), cardiac function indexes, and number of reconstructive procedures were compared during acute hospital stay and at long-term follow-up (up to 2 yrs postinjury). Scar evaluation was performed at long-term follow-up.

RESULTS

There were no significant differences between Integra and controls in burn size (70 +/- 5% vs. 74 +/- 4% total body surface area), mortality (40% vs. 30%), and length of stay (41 +/- 4 vs. 39 +/- 4 days). In the short term, resting energy expenditure significantly decreased (p < .01), and serum levels of constitutive proteins significantly increased (p < .03) in the Integra group compared with controls. Long-term follow-up revealed a significant increase in bone mineral content and density (24 months postburn, p < .05), as well as improved scarring in terms of height, thickness, vascularity, and pigmentation (12 months and 18-24 months, p < .01) in the Integra group.

CONCLUSION

Integra can be used for immediate wound coverage in children with severe burns without the associated risks of cadaver skin.

[Early surgical management of severe burns]

The success of modern burn therapy is based on an understanding of the pathophysiology and application of burn intensive care implying fluid resuscitation and management of pulmonary or other organ failure. With the development of early eschar excision and wound closure by immediate grafting, survival and cosmetic outcome were further improved. Especially in post-acute therapy, early physical rehabilitation, early reintegration, and early plastic surgical correction of the sequelae are indispensable for the outcome.

New technologies for burn wound closure and healing--review of the literature

Methods for handling burn wounds have changed in recent decades. Increasingly, aggressive surgical approach with early tangential excision and wound closure is being applied leading to improvement in mortality rates of burn victims. Autografts from uninjured skin remain the mainstay of treatment. Autologous skin graft, however, has limited availability and is associated with additional morbidity and scarring. Severe burn patients invariably lack sufficient adequate skin donor sites requiring alternative methods of skin replacement. The present review summarizes available replacement technologies.

Close Relative Intermingled Skin Allograft and Autograft Use in the Treatment of Major Burns in Adults and Children

Major burns still continue to pose problems of inadequate auto skin closure. Patients suffering severe burns lack adequate skin graft donor site. We present the results of 17 major adult and pediatric burns that we applied close relative intermingled skin allograft and autograft in the course of treatment. The extent of burn injury ranged from 40%-70% total body surface are (TBSA). Seven patients survived and 10 patients died. Mean percent TBSA of the dead and surviving patients were 55.5 +/- 11.16 (range, 40-70) and 55.0 +/- 4.08 (range, 50-60) respectively. Mean age of the dead and surviving patients were 16.1 +/- 13.77 (range, 2-42) and 11.1 +/- 6.74 (range, 2-21), respectively. We present a safe and satisfactory means of effective alternative treatment to resurface major burns in case of limited auto skin graft donor site without exposure to bacteria, human immunodeficiency virus, and hepatitis virus when keratinocyte culture facilities and skin banks are not available.