Perspectives in the use of allograft

Current Approaches to Wound Repair in Burns: How far Have we Come From Cover to Close? A Narrative Review

Burn injuries are a significant global health concern, with more than 11 million people requiring medical intervention each year and approximately 180,000 deaths annually. Despite progress in health and social care, burn injuries continue to result in socioeconomic burdens for victims and their families. The management of severe burn injuries involves preventing and treating burn shock and promoting skin repair through a two-step procedure of covering and closing the wound. Currently, split-thickness/full-thickness skin autografts are the gold standard for permanent skin substitution. However, deep burns treated with split-thickness skin autografts may contract, leading to functional and appearance issues. Conversely, defects treated with full-thickness skin autografts often result in more satisfactory function and appearance. The development of tissue-engineered dermal templates has further expanded the scope of wound repair, providing scar reductive and regenerative properties that have extended their use to reconstructive surgical interventions. Although their interactions with the wound microenvironment are not fully understood, these templates have shown potential in local infection control. This narrative review discusses the current state of wound repair in burn injuries, focusing on the progress made from wound cover to wound closure and local infection control. Advancements in technology and therapies hold promise for improving the outcomes for burn injury patients. Understanding the underlying mechanisms of wound repair and tissue regeneration may provide new insights for developing more effective treatments in the future.

Introduction: The Multidisciplinary Team Approach to Burn Care

Since the first burn units were established following World War II, great advances in understanding and treating burn shock, smoke inhalation injury, pneumonia, and invasive burn wound infections, and in achieving early burn-wound closure, have greatly decreased postburn morbidity and mortality. These advances were the result of closely integrated multidisciplinary teams of clinicians and researchers. The team approach to burns is a model for success in the care of any challenging clinical problem.

The Role of Skin Substitutes in Acute Burn and Reconstructive Burn Surgery: An Updated Comprehensive Review

Burns disrupt the protective skin barrier with consequent loss of cutaneous temperature regulation, infection prevention, evaporative losses, and other vital functions. Chronically, burns lead to scarring, contractures, pain, and impaired psychosocial well-being. Several skin substitutes are available and replace the skin and partially restore functional outcomes and improve cosmesis. We performed a literature review to update readers on biologic and synthetic skin substitutes to date applied in acute and reconstructive burn surgery. Improvement has been rapid in the development of skin substitutes in the last decade; however, no available skin substitute fulfills criteria as a perfect replacement for damaged skin.

Evaluation of a cross-linked versus non-cross-linked collagen matrix in full-thickness skin defects

Autologous skin transplantation is the gold standard for treatment of full-thickness skin defects such as deep burn injuries, but has the disadvantages of limited donor sites and donor site morbidities. Alternative skin replacement products, such as xenografts and allografts, are not a permanent solution. Numerous manufactured skin substitutes already show promising approaches, but have limited efficacy. Therefore, wound dressings adaptable to the physiology of wound healing are still needed. In a randomized controlled in vivo study, a newly designed biocompatible collagen nonwoven matrix was compared to the Integra® bilayer dermal substitute and untreated controls in 48 full-thickness skin defects in a swine model. The take of all templates was complete, and all the tissue-engineered products accelerated dermal wound healing compared to the untreated controls, as identified by planimetric measurements. The higher collagen dose treatments and Integra®-covered wounds developed the thickest, cell-rich neoepidermal tissue in histological examination. The innovative biocompatible collagen matrix is flexibly applicable and modifiable, and offers potential as a carrier membrane for therapeutic supplemental products such as growth factors to further develop effective wound dressings.

A paradigm shift in practice-the benefits of early active wound temporisation rather than early skin grafting after burn eschar excision

After major burn injury, once survival is achieved by the immediate excision of all deep burn eschar, we are faced with a patient who is often physiologically well but with very extensive wounds. While very early grafting yields excellent results after the excision of small burns, it is not possible to achieve the same results once the wound size exceeds the available donor site. In patients where 50%-100% of the total body surface area is wound, we rely on serial skin graft harvest, from finite donor site resources, and the massive expansion of those harvested grafts to effect healing. The result is frequently disabling and dysaesthetic. Temporisation of the wounds both passively, with cadaver allograft, and actively, with dermal scaffolds, has been successfully employed to ameliorate some of the problems caused by our inability to definitively close wounds early. Recent advances in technology have demonstrated that superior functional and cosmetic outcomes can be achieved in actively temporised areas even when compared with definitive early closure with skin graft. This has several beneficial implications for both patient and surgeon, affecting the timing of definitive wound closure and creating a paradigm shift in the care of the burned patient.

Observation of viable alloskin vs xenoskin grafted onto subcutaneous tissue wounds after tangential excision in massive burns

Background

Staged excision and grafting with viable cryopreserved alloskin or fresh pigskin at an early stage is a main strategy for wound management in massive burns. Alloskin is the gold standard of a biological temporary skin substitute, and the main drawback to its wider use is the limited number of donors. In this paper, we compare the use of fresh pigskins to cryopreserved alloskins as temporary skin substitutes on subcutaneous tissue wounds after tangential excision by observing the clinical performances of these grafts in cases of a massive burn.

Methods

We selected six adult massive burn patients undergoing tangential excision and skin grafting on subcutaneous tissue wounds (TESGSTW) at our burn center from January 1, 2003 to December 31, 2013. The general clinical data and survival percentage of skins at postoperative weeks (POWs) 1, 2, and 3 were analyzed. In our clinical practice, we also observed the phenomenon that several viable cryopreserved alloskin or fresh pigskin grafts used as temporary coverage on subcutaneous tissue wounds had long-term survival after repeated desquamation. The macroscopic and histological results of one typical case were also analyzed.

Results

In this study, the first three TESGSTW operations were performed at 2–3, 5–8, and 11–16 days post-injury. The operation areas were 30.3 ± 7.9 % total body surface area (TBSA), 19.0 ± 6.0 % TBSA, and 12.0 ± 1.7 % TBSA, respectively. The survival percentage of the cryopreserved alloskins or fresh pigskins at POWs 1, 2, and 3 were 80.0 ± 10.0 % vs 75.7 ± 5.3 % (t = 1.01, P = 0.16), 71.2 ± 10.6 % vs 66.4 ± 6.2 % (t = 1.09, P = 0.30), and 48.7 ± 2.5 % vs 35.0 ± 7.0 % (t = 3.83, P = 0.03), respectively. The microscopic observation of the survival of alloskins or pigskins in one typical case showed rete ridges and a basilar membrane at the joint of the epidermis and dermis at an early stage; these structures disappeared with extended time post-operation.

Conclusions

From the clinical observations, fresh pigskin and cryopreserved alloskins could be used with equal effectiveness at an early stage (within 2 weeks post-operation) as temporary coverage on massive burns after TESGSTW. After engraftment, several cryopreserved alloskins or fresh pigskins could co-survive in a massive burn patient for an extended amount of time. The co-survival of alloskin and pigskin will provide clues for further research into skin transplantation.

Electronic supplementary material

The online version of this article (doi:10.1186/s41038-016-0045-9) contains supplementary material, which is available to authorized users.

Unexpected hematologic effects of biotherapeutics in nonclinical species and in humans

Biotherapeutics are expanding the arsenal of therapeutics available for treating and preventing disease. Although initially thought to have limited side effects due to the specificity of their binding, these drugs have now been shown to have potential for adverse drug reactions including effects on peripheral blood cell counts or function. Hematotoxicity caused by a biotherapeutic can be directly related to the activity of the biotherapeutic or can be indirect and due to autoimmunity, biological cascades, antidrug antibodies, or other immune system responses. Biotherapeutics can cause hematotoxicity primarily as a result of cellular activation, cytotoxicity, drug-dependent and independent immune responses, and sequelae from initiating cytokine and complement cascades.  The underlying pathogenesis of biotherapeutic-induced hematotoxicity often is poorly understood. Nonclinical studies have generally predicted clinical hematotoxicity for recombinant cytokines and growth factors.  However, most hematologic liabilities of biotherapeutics are not based on drug class but are species specific, immune-mediated, and of low incidence. Despite the potential for unexpected hematologic toxicity, the risk-benefit profile of most biotherapeutics is favorable; hematologic effects are readily monitorable and managed by dose modification, drug withdrawal, and/or therapeutic intervention.  This article reviews examples of biotherapeutics that have unexpected hematotoxicity in nonclinical or clinical studies. 

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.

Allogenic skin in the treatment of burns

Allogenic skin has had a major role in acute burns care for over 100 years. The principle source of allogenic skin is from cadavers. Allogenic skin provides the gold standard for temporary skin substitutes. The main drawbacks to its wider use are availability and disease transmission. The major obstacle to prolonged use is its immunogenicity. As more effective means are developed to ensure the supply and safety of allogenic skin and novel ways of circumventing the immunologic problems are developed, it is possible that allogenic skin may find a new role as a permanent skin replacement in future burns care.

The use of homograft compared to topical antimicrobial therapy in the treatment of second-degree burns of more than 40% total body surface area

The traditional approach for the treatment of partial-thickness burns has been the application of topical antimicrobial therapy to control bacterial colonization, avoid progression to invasive infection, and allow healing of the underlying burn wound. Infection is associated with apparent conversion of a second-degree burn to full-thickness injury that requires autografting, to say nothing of a source of sepsis, which has been associated with multiorgan failure and death. We postulated that early debridement and coverage of large partial-thickness burns (>40% total body surface area) with homograft would preserve underlying tissue, improves healing, and decreases morbidity. We present data obtained in 16 patients treated with the application of homograft compared to 13 patients treated with the traditional approach consisting of twice daily applications of silver sulfadiazine. The treatment of massive second-degree burns with homograft reduced hospital length of stay (P < 0.01). We thus conclude that in patients with >40% total body surface area burns, early debridement and wound coverage with homograft is an alternative method to the conservative non-operative approach with topical antimicrobial therapy.

Overexpression of vascular endothelial growth factor accelerates early vascularization and improves healing of genetically modified cultured skin substitutes

Cultured skin substitutes (CSS) lack a vascular plexus, leading to slower vascularization after grafting than split-thickness skin autograft. CSS containing keratinocytes genetically modified to overexpress vascular endothelial growth factor (VEGF) were previously shown to exhibit enhanced vascularization up to 2 weeks after grafting to athymic mice. The present study examines whether enhanced vascularization compared with controls persists after stable engraftment is achieved and analyzes VEGF expression, wound contraction, and engraftment. Control and VEGF-modified (VEGF+) CSS were grafted onto full-thickness wounds in athymic mice. VEGF expression was detected in VEGF+ CSS 14 weeks after grafting. Graft contraction was significantly lower in VEGF+ CSS compared with controls, suggesting more stable engraftment and better tissue development. Positive HLA-ABC staining, indicating persistence of human cells, was seen in 86.7% (13/15) of grafted VEGF+ CSS, compared with 58.3% (7/12) of controls. Differences in dermal vascularization between control and VEGF+ grafts were significant 1 week after surgery, but not at later times. However, the distribution of vessels was different, with more vessels in the upper dermis of VEGF+ grafts. These results suggest that VEGF overexpression in genetically modified CSS acts to accelerate early graft vascularization and can contribute to improved healing of full-thickness skin wounds.

[Integra, a new surgical alternative for the treatment of massive burns. Clinical evaluation of acute and reconstructive surgery: 39 cases]

Early excision and prompt coverage in severely burned patients are the best way to lessen morbidity and improve survival. Repair of full-thickness burns requires replacement of both dermal and epidermal components of skin and treatment with split thickness autografts replaces both of them. But healthy skin is not sufficient in extensive burns. Alternative to split thickness skin grafts have been studied by several groups including epidermis, dermis or a complete replacement comprising epidermis and dermis. Because of the difficulties in homografts supplying, a new way was use to replace the dermis. In 1981, Yannas and Burke were the first to develop such a matrix. Intégra is available in France since 1997 and was used in our service for the treatment of both acute and reconstructive surgery for burned patients. Twenty patients were treated for acute surgery. Nineteen patients were treated for reconstructive surgery of burn scar contractures. Fifty-one grafts of Intégra were performed. Long-term final results seem to show that Intégra improve cosmetical and functional results and is a new surgical alternative for the treatment of burns in the acute phase as well as in late surgery of deformities.

Cadaver donor discards secondary to serology

The use of cadaveric skin has made a major impact in the survival of patients experiencing major thermal injury. However, the availability of cadaveric skin is often limited by potentially pathogenic organisms. Very little data exists as to why cadaveric skin from donors who have been previously screened was discarded. From March 1994 to March 1996, 813 donors were referred to our tissue bank. All donors were reviewed for the cause of death, history and physical, and social history. One hundred fifty-three donors screened were discarded. Sixty-one donors of this group were discarded because of positive serologies. The following are the percentages of the specific positive serologies: hepatitis B core antibody, 52.3%; hepatitis B surface antigen, 18.1%; hepatitis C virus antibody, 14.3%; human immunodeficiency virus antibody, 4.9%; human T lymphocyte virus antibody, 4.9% and syphilis, 5.5%. Retrospectively, all donor screening questionnaires were reviewed for possible indicators in relation to positive serologic testing. Current screening methods, although excellent in social screening, still fail to identify a significant number of donors who may have positive serologies because of hepatitis, human immunodeficiency virus, human T lymphocyte virus, or syphilis. As the field of tissue banking continues to evolve, the focus will need to be directed toward better screening mechanisms in order to decrease our current discard rates after donors have been approved through the screening process.