The evolutionary development of biologic dressings and skin substitutes

Evaluation of Bacterial Cellulose/Alginate-Based Hydrogel and Frog Skin Dressings in Equine Skin Wound Healing

This study evaluates the wound-healing process in horses following the application of two treatment modalities: bacterial cellulose hydrogel with alginate (BCAW) and frog skin (FSW) dressings on experimentally induced skin wounds. Throughout the experiment, no clinical abnormalities were noted in the horses, although initial wound assessments indicated edema and sensitivity. Local hemorrhage was observed in some cases on Day 0, with granulation tissue formation evident by Day 14. Epithelialization began around Day 14 but did not reach complete healing in any group by Day 28. The analysis showed no significant differences in skin wound area or wound contraction rates among the treatment groups compared to control wounds (CWs) over the evaluation periods. Histopathological evaluations also indicated no significant differences in inflammatory responses or healing markers, such as fibroblast proliferation and neovascularization in skin wounds across groups. Despite expectations based on prior research in other species, the treatments with BCAW and FSW did not demonstrate substantial pro-healing effects in horses with induced skin wounds. These findings underscore the complexity of equine wound healing and suggest further investigation is needed to optimize treatment strategies in this species and enhance the translational potential for human clinical applications.

New strategies for sterilization and preservation of fresh fish skin grafts

The introduction of fish skin as a biological dressing for treating burns and wounds holds great promise, offering an alternative to existing management strategies. However, the risk of disease transmission is a significant concern. Therefore, this study aimed to examine how established sterilization and preservation procedures affected fish skin grafts' microbiological and histological properties for long-term usage. Lyophilization of the fish skin graft followed by rehydration in normal saline for 15 min did not change the collagen content. Furthermore, gamma irradiation of the lyophilized fish skin graft at different lengths 5, 10, and 25 KGy showed a significant reduction in microbial growth (aerobic bacteria, aerobic yeasts, and fungi) at 15- and 30 days after the irradiation. However, exposure to 10 KGy was found to be the most effective intensity among the different gamma irradiation lengths since it preserved the collagen fiber content and intensity in the lyophilized fish skin grafts at 15- and 30 days after the irradiation. These findings provide efficient preservation and sterilization methods for long-term usage of the fresh Tilapia skin grafts used for biological dressings.

Craniofacial Tissue Engineering

There is substantial need for the replacement of tissues in the craniofacial complex due to congenital defects, disease, and injury. The field of tissue engineering, through the application of engineering and biological principles, has the potential to create functional replacements for damaged or pathologic tissues. Three main approaches to tissue engineering have been pursued: conduction, induction by bioactive factors, and cell transplantation. These approaches will be reviewed as they have been applied to key tissues in the craniofacial region. While many obstacles must still be overcome prior to the successful clinical restoration of tissues such as skeletal muscle and the salivary glands, significant progress has been achieved in the development of several tissue equivalents, including skin, bone, and cartilage. The combined technologies of gene therapy and drug delivery with cell transplantation will continue to increase treatment options for craniofacial cosmetic and functional restoration.

Skin and skin substitutes in burn management

Early burn excision has reduced the mortality from major burns. This practice presents the problem of wound coverage after excision, since the availability of autologous donor sites is limited in very large burns. This article reviews the methods available for covering burn wounds. Methods of expanding autologous skin are discussed as well as techniques using allogeneic tissue and xenograft. Newer synthetic skin substitutes have become an important advance and are also described. Cultured skin replacements are also discussed along with their shortfalls. The treatment of a patient with major burns may require the use of many different skin substitutes, as none is entirely satisfactory on its own.

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.

Reflection: evolution of the field over seven decades

Marked expansion of physiologic understanding and the improvement of burn patient outcomes have resulted from multidisciplinary clinical/laboratory research programs at burn centers in the United States and elsewhere.

An historical perspective on advances in burn care over the past 100 years

The accelerated pace of clinical and laboratory research over the past century and application of the research findings to patient care have resulted in unprecedented survival of burned patients in all age groups. Resuscitation based on an understanding of the nature and magnitude of the multisystem response to injury now prevents burn shock; effective topical antimicrobial chemotherapy and early excision prevent wound toxemia and sepsis; biologic and bioengineered dressings compensate for the missing skin; and broad spectrum metabolic support regimens prevent exhaustion and accelerate convalescence. Rehabilitation programs have also been developed to restore physical function and permit the burn patient to reenter society as a productive individual.

Tissue engineering of cultured skin substitutes

Skin replacement has been a challenging task for surgeons ever since the introduction of skin grafts by Reverdin in 1871. Recently, skin grafting has evolved from the initial autograft and allograft preparations to biosynthetic and tissue-engineered living skin replacements. This has been fostered by the dramatically improved survival rates of major burns where the availability of autologous normal skin for grafting has become one of the limiting factors. The ideal properties of a temporary and a permanent skin substitute have been well defined. Tissue-engineered skin replacements: cultured autologous keratinocyte grafts, cultured allogeneic keratinocyte grafts, autologous/allogeneic composites, acellular biological matrices, and cellular matrices including such biological substances as fibrin sealant and various types of collagen, hyaluronic acid etc. have opened new horizons to deal with such massive skin loss. In extensive burns it has been shown that skin substitution with cultured grafts can be a life-saving measure where few alternatives exist. Future research will aim to create skin substitutes with cultured epidermis that under appropriate circumstances may provide a wound cover that could be just as durable and esthetically acceptable as conventional split-thickness skin grafts. Genetic manipulation may in addition enhance the performance of such cultured skin substitutes. If cell science, molecular biology, genetic engineering, material science and clinical expertise join their efforts to develop optimized cell culture techniques and synthetic or biological matrices then further technical advances might well lead to the production of almost skin like new tissue-engineered human skin products resembling natural human skin.

“Xenograft” dressing in the treatment of burns

Biologic dressings (xenografts and allografts) are an integral part of modern burns care. They provide; reduction of pain and adherence without need for additional fixation; antibacterial action that is a function of its adherence; protection against physical trauma; appropriate heat and moisture retention. Allografts are more effective but supply may be severely restricted. Porcine skin is our standard dressing for partial-thickness burns; it also has a role in providing temporary coverage of full-thickness defects and for debriding burns/ulcers.

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.

Burn wound assessment and surgical management

Ideally, in a burn-traumatized patient, nonviable skin and tissues should be excised early in the course of treatment and replaced with a graftable material that mimics the properties of normal skin in function,texture, sensation, and appearance. The difficulty in identifying indeterminate-depth dermal injuries requires further studies to establish the line between extending injury and delaying the progressive excision of nonviable tissue. Recent studies have shown that molecularly the process of wound healing is an interaction among multiple macromolecules and therefore requires in-depth studies of growth factor symptoms, the extra-cellular matrix, and the immunologic response to wounds [8788].The survival of patients with major thermal injuries (Fig. 35) has dramatically increased in recent years. Therefore, greater emphasis must be placed on improving the overall treatment process and the quality of the end result for these patients. Surgically directed and laboratory-based investigations into the cellular components of wound repair and the development of alternative methods of final wound closure are continuing to evolve, and bum specialists are,optimistic that new alternatives will become available for their patients.

Rehabilitation of burn injuries

Burn rehabilitation is a complex and difficult process for the burn survivor, his or her family, and the entire treatment team. This article describes the best approaches in burn care, including the use of a multidisciplinary team that emphasizes functional restoration through aggressive wound care, pain management, mobilization, and psychologic support.

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.

Rapid aggressive soft-tissue necrosis after beetle bite can be treated by radical necrectomy and vacuum suction-assisted closure

BACKGROUND

The substance cantharidin, which is produced by a type of beetle, rapidly penetrates the epidermis and can cause severe toxicities such as skin necrosis. Optimal treatment for necrotic beetle bites has not been well defined. Conservative management has been advocated but the hospital stays are long and long-term morbidity may result, especially in multimorbid patients.

OBJECTIVE

The value of aggressive surgical management of such necrotizing diseases using newly developed surgical tools is compared to the traditional more conservative approach.

RESULTS

We present the case of a multimorbid 60-year-old man with a rapidly progressive necrosis of the medial thigh (measuring 30 X 15 cm), acquired during a stay in Western Africa after being bitten by a beetle of the species Cantharide. The patient was treated with radical surgical debridement and continuous elimination of the wound fluid by permanent computer-controlled negative pressure with a vacuum-assisted wound-closure device. This led to the sudden relief of both local and systemic symptoms and allowed extremely early wound closure.

CONCLUSIONS

Comparing literature data with the course of this combined treatment, we strongly suggest an early aggressive management with complete radical excision of necrotic tissue, conditioning of the wound bed by temporary suction-assisted vacuum closure and subsequent skin grafting with continued vacuum application. This treatment leads to immediate relief of pain and enhanced healing of this lesion even in the condition of immunosuppression in the elderly.

Multistep production of bioengineered skin substitutes: sequential modulation of culture conditions

Many studies are being conducted to define the role of growth factors in cutaneous physiology in order to add cytokines in a timely fashion for optimal tissue engineering of skin. This study is aimed at developing a multistep approach for the production of bioengineered skin substitutes, taking into account the effects of various growth factors according to the culture time. The use of a serum-supplemented medium throughout the whole culture period of skin substitutes was compared to the sequential use of specific additives at defined culture steps. Histological analysis revealed that serum was necessary for keratinocyte proliferation and migration on dermal substitutes during the first 2 d after their seeding. However, the serum-free medium presented some advantages when supplemented with different additives at specific culture steps. Interestingly, ascorbic acid added to the dermal substitutes before and after keratinocyte seeding maintained their cuboidal morphology in the basal epidermal layer. In the absence of serum, collagen matrix degradation slowed down, and a better multilayered epidermal organization was obtained, notably with retinoic acid. Stratum corneum formation was also enhanced by fatty acids. Thus, sequential addition of exogenous factors to the medium used to produce skin substitutes can improve their structural features and functional properties in vitro.

Management of partial thickness facial burns (comparison of topical antibiotics and bio-engineered skin substitutes)

This study compared the effect of standard topical antibiotic management versus a biological skin substitute wound closure for mid-partial thickness burns of the face. Adult patients with mid-dermal facial burns produced by flash flames or flame exposure were studied using a randomized prospective study design. Total daily burn care time, pain (0-10 scale) and healing time were monitored. Immediately after partial thickness debridement, the entire face burn, including ears, was closed with a bioengineered skin substitute coated with fibronectin (TransCyte) or treated by the open technique using bacitracin ointment applied 2-3 times daily. 21 patients were studied, with 10 patients in the skin substitute group. We found a significant decrease in wound care time 0.35 +/- 0.1 versus 1.9 +/- 0.5 h, decrease in pain of 2 +/- 1 versus 4 +/- 2 and re-epithelialization time 7 +/- 2 versus 13 +/- 4 days in the skin substitute group compared to topical antibiotics. We can conclude that a bioengineered skin substitute significantly improves the management and healing rate of partial thickness facial burns, compared to the standard open topical ointment technique.