Tissue engineering in burn scar reconstruction

The Role of Microsurgery in Burn Surgery

Acute burn reconstruction involves intricate strategies such as skin grafting and innovative technologies, addressing challenges in coverage and minimizing donor site morbidity. Despite being rarely used, flap reconstruction becomes necessary when critical structures are exposed, offering robust coverage and reducing complications. However, free flaps in acute burns face challenges, including a higher failure rate attributed to hyperinflammatory states and hypercoagulability. Surgical optimization strategies involve careful timing, patient preparation, and meticulous postoperative care. In delayed burn reconstruction, free flaps proved effective in functional and aesthetic restoration, with low flap loss rates and minimal contracture recurrence. Prefabricated and prelaminated flaps emerged as a solution for complex cases, ensuring the best functional and aesthetic possible outcomes in challenging facial burn reconstructions.

Challenges in the Management of Large Burns

Large burns provoke profound pathophysiological changes. Survival rates of patients with large burns have improved significantly with the advancement of critical care and adaptation of early excision protocols. Nevertheless, care of large burn wounds remains challenging secondary to limited donor sites, prolonged time to wound closure, and immunosuppression. The development of skin substitutes and new grafting techniques decreased time to wound closure. Individually, these methods have limited success, but a combination of them may yield more successful outcomes. Early identification of patients with likely poor prognosis should prompt goals of care discussion and involvement of a palliative care team when possible.

Scar formation from the perspective of complexity science: a new look at the biological system as a whole

A burn wound is a complex systemic disease at multiple levels. Current knowledge of scar formation after burn injury has come from traditional biological and clinical studies. These are normally focused on just a small part of the entire process, which has limited our ability to sufficiently understand the underlying mechanisms and to predict systems behaviour. Scar formation after burn injury is a result of a complex biological system-wound healing. It is a part of a larger whole. In this self-organising system, many components form networks of interactions with each other. These networks of interactions are typically non-linear and change their states dynamically, responding to the environment and showing emergent long-term behaviour. How molecular and cellular data relate to clinical phenomena, especially regarding effective therapies of burn wounds to achieve minimal scarring, is difficult to unravel and comprehend. Complexity science can help bridge this gap by integrating small parts into a larger whole, such that relevant biological mechanisms and data are combined in a computational model to better understand the complexity of the entire biological system. A better understanding of the complex biological system of post-burn scar formation could bring research and treatment regimens to the next level. The aim of this review/position paper is to create more awareness of complexity in scar formation after burn injury by describing the basic principles of complexity science and its potential for burn care professionals.

Clinical applications of acellular dermal matrices: A review

INTRODUCTION

The extracellular matrix (ECM) plays an integral role in wound healing. It provides both structure and growth factors that allow for the organised cell proliferation. Large or complex tissue defects may compromise host ECM, creating an environment that is unfavourable for the recovery of anatomical function and appearance. Acellular dermal matrices (ADMs) have been developed from a variety of sources, including human (HADM), porcine (PADM) and bovine (BADM), with multiple different processing protocols. The objective of this report is to provide an overview of current literature assessing the clinical utility of ADMs across a broad spectrum of applications.

METHODS

PubMed, MEDLINE, EMBASE, Scopus, Cochrane and Web of Science were searched using keywords 'acellular dermal matrix', 'acellular dermal matrices' and brand names for commercially available ADMs. Our search was limited to English language articles published from 1999 to 2020 and focused on clinical data.

RESULTS

A total of 2443 records underwent screening. After removing non-clinical studies and correspondence, 222 were assessed for eligibility. Of these, 170 were included in our synthesis of the literature. While the earliest ADMs were used in severe burn injuries, usage has expanded to a number of surgical subspecialties and procedures, including orthopaedic surgery (e.g. tendon and ligament reconstructions), otolaryngology, oral surgery (e.g. treating gingival recession), abdominal wall surgery (e.g. hernia repair), plastic surgery (e.g. breast reconstruction and penile augmentation), and chronic wounds (e.g. diabetic ulcers).

CONCLUSION

Our understanding of ADM's clinical utility continues to evolve. More research is needed to determine which ADM has the best outcomes for each clinical scenario.

LAY SUMMARY

Large or complex wounds present unique reconstructive and healing challenges. In normal healing, the extracellular matrix (ECM) provides both structural and growth factors that allow tissue to regenerate in an organised fashion to close the wound. In difficult or large soft-tissue defects, however, the ECM is often compromised. Acellular dermal matrix (ADM) products have been developed to mimic the benefits of host ECM, allowing for improved outcomes in a variety of clinical scenarios. This review summarises the current clinical evidence regarding commercially available ADMs in a wide variety of clinical contexts.

Silver sulfadiazine loaded core-shell airbrushed nanofibers for burn wound healing application

Ideal dressing materials for complex and large asymmetric burns should have the dual properties of anti-bacterial and regenerative with advanced applicability of direct deposit on the wound at the patient bedside. In this study, core-shell nanofibers (polycaprolactone; PCL and polyethylene oxide; PEO) with different percent of silver sulfadiazine (SSD) loading (2-10%) were prepared by the airbrushing method using a custom build device. Results indicate a sustained release profile of silver sulfadiazine (SSD) up to 28 days and concentration-dependent anti-bacterial activity. The morphology and proliferation of human dermal fibroblast (HDF) cells and human dental follicle stem cells (HDFSC) on the silver sulfadiazine loaded nanofibers confirm the biocompatibility of airbrushed nanofibers. Moreover, upregulation of extracellular matrix (ECM) proteins (Col I, Col III, and elastin) support the differentiation and regenerative properties of silver sulfadiazine nanofiber mats. This was further confirmed by the complete recovery of rabbit burn wound models within 7 days of silver sulfadiazine loaded nanofiber dressing. Histopathology data show silver sulfadiazine loaded core-shell nanofibers' anti-inflammatory and proliferative activity without any adverse response on the tissue. Overall data display that the airbrushed silver sulfadiazine-loaded core-shell nanofibers are effective dressing material with the possibility of direct fiber deposition on the wound to cover, heal, and regenerate large asymmetric burn wounds.

Functional facial reconstruction in a patient with severe burn sequelae with a prelaminated parascapular free flap based on a three-dimensional model: A case report

Significant evolution has been made concerning resuscitation and emergency management of severely burned patients, and nowadays most patients will survive and deal with burns sequelae. They constitute a reconstructive challenge, mainly because options and donor areas are frequently compromised, results are often limited, and other options should then be considered. A 27-year-old male patient with 55% total burn surface area, presented with severe facial disfigurement including ectropion, upper/lower lip retraction, and partial loss of the nose. In order to improve the patient's condition, autologous reconstruction was considered. The only unburned area in the body was the left dorsal region, and a three-stage reconstruction was planned using a paraescapular flap. In a first stage, an elective surgery was performed to identify and tag the recipient vessels in the neck. After 3 months, the prelamination process was initiated with the drawing of a facial model, and a nose and lips were opened inside the flap. This was based on a three-dimensional latex model as a print of the patient's face, which allowed us to calculate distances and estimate the length of the vascular pedicles. After 3 months, the flap (18 × 8 cm) was transferred and microvascular anastomoses were performed. No major complications were seen after surgeries, and after 28 months, an extremely important functional gain was obtained. Despite the number of surgeries required and less than optimal aesthetic results, this method may offer a satisfactory solution for complex acquired facial burn sequelae when other local or distant flap options are not available.

Burn injury

Burn injuries are under-appreciated injuries that are associated with substantial morbidity and mortality. Burn injuries, particularly severe burns, are accompanied by an immune and inflammatory response, metabolic changes and distributive shock that can be challenging to manage and can lead to multiple organ failure. Of great importance is that the injury affects not only the physical health, but also the mental health and quality of life of the patient. Accordingly, patients with burn injury cannot be considered recovered when the wounds have healed; instead, burn injury leads to long-term profound alterations that must be addressed to optimize quality of life. Burn care providers are, therefore, faced with a plethora of challenges including acute and critical care management, long-term care and rehabilitation. The aim of this Primer is not only to give an overview and update about burn care, but also to raise awareness of the ongoing challenges and stigmata associated with burn injuries.

Preparation and characterization of a gallium-loaded antimicrobial artificial dermal scaffold

Artificial dermal scaffolds, which are made of natural or synthetic materials, can improve new blood vessel formation, cell migration and cell proliferation after being implanted into wounds, and they degrade slowly, playing an important role in dermal reconstruction and scar inhibition, finally achieving the goal of wound healing and functional reconstruction. Although these scaffolds have been widely used in clinical applications, biomaterial-associated infection is a deficiency or even a life-threatening problem that must be addressed, as it greatly affects the survival of the scaffolds. The gallium ion (Ga³⁺) is a novel metallic antimicrobial whose broad-spectrum antimicrobial properties against most bacteria encountered in burn wound infections have been confirmed, and it has been proposed as a promising candidate to prevent implant-associated infections. In this study, a gallium-loaded antimicrobial artificial dermal scaffold was successfully prepared by gallium ions and a collagen solution. The characterization results showed a porous structure with pore sizes ranging from 50 to 150 μm and a large porosity value of 97.4%. The enzymatic degradation rate in vitro was 19 and 28% after 12 and 24 h, respectively. In vitro antimicrobial testing revealed that the 1 h antibacterial rate against Staphylococcus aureus and Pseudomonas aeruginosa was close to 90%, which indicated its great antimicrobial activity. The results of the cytological evaluation showed slight effect on cell proliferation, with a relative growth rate (RGR) value of 80% and great cytocompatibility with cultured cells according to laser scanning confocal microscopy (LSCM) and scanning electron microscope (SEM). Furthermore, the successful prevention of wound infections in SD rats was confirmed with an in vivo antimicrobial evaluation, and the artificial dermal scaffolds also demonstrated great biocompatibility. This gallium-loaded antimicrobial artificial dermal scaffold exerted excellent antimicrobial activity and great biosafety, warranting further research for future clinical applications.

The Use of Integra in Extensive Full-Thickness Scalp Burn Involving the Skull in a Child

Extensive full-thickness burn injury of the scalp involving the skull is a challenge to reconstruct. Here, the authors report a case of a 6-year old girl who suffered extensive flame burn injury involving a scalp defect of 1,5% total body surface area. After necrosectomy, full table damage of the skull was observed with a partially exposed dura mater. Neurosurgical consultation was necessary to accomplish a vital wound bed. Subsequently, in the absence of enough adequate tissue available for flap surgery reconstruction, reconstruction was performed by using a bilayer Integra Dermal Regeneration Template (IDRT) resulting in a lasting and stable coverage of the defect. This is the first case-report describing application of IDRT on a full-thickness scalp and skull defect with exposed dura mater in a child. Our results are encouraging and demonstrate that Integra can be used in a child to successfully cover exposed dura when no viable skull remains.

Endothelial cells enhance adipose mesenchymal stromal cell-mediated matrix contraction via ALK receptors and reduced follistatin: Potential role of endothelial cells in skin fibrosis

Abnormal cutaneous wound healing can lead to formation of fibrotic hypertrophic scars. Although several clinical risk factors have been described, the cross‐talk between different cell types resulting in hypertrophic scar formation is still poorly understood. The aim of this in vitro study was to investigate whether endothelial cells (EC) may play a role in skin fibrosis, for example, hypertrophic scar formation after full‐thickness skin trauma. Using a collagen/elastin matrix, we developed an in vitro fibrosis model to study the interaction between EC and dermal fibroblasts or adipose tissue‐derived mesenchymal stromal cells (ASC). Tissue equivalents containing dermal fibroblasts and EC displayed a normal phenotype. In contrast, tissue equivalents containing ASC and EC displayed a fibrotic phenotype indicated by contraction of the matrix, higher gene expression of ACTA2, COL1A, COL3A, and less secretion of follistatin. The contraction was in part mediated via the TGF‐β pathway, as both inhibition of the ALK4/5/7 receptors and the addition of recombinant follistatin resulted in decreased matrix contraction (75 ± 11% and 24 ± 8%, respectively). In conclusion, our study shows that EC may play a critical role in fibrotic events, as seen in hypertrophic scars, by stimulating ASC‐mediated matrix contraction via regulation of fibrosis‐related proteins.

Burn injury: Challenges and advances in burn wound healing, infection, pain and scarring

Severe burn injuries are the most traumatic and physically debilitating injuries affecting nearly every organ system and leading to significant morbidity and mortality. Early burn wound excision and skin grafting are common clinical practices that have significantly improved the outcomes for severe burn injured patients by reducing mortality rate and days of hospital stay. However, slow wound healing, infection, pain, and hypertrophic scarring continue to remain a major challenge in burn research and management. In the present article, we review and discuss issues in the current treatment of burn injuries; the advances and novel strategies developed in the past decade that have improved burn management; and also, pioneer ideas and studies in burn research which aims to enhance burn wound care with a focus on burn wound infection, pain management, treatments for scarring and skin tissue engineering.

Modulation of scar tissue formation in injured nervous tissue cultivated on surface-engineered coralline scaffolds

Following traumatic brain injury, there is no restoration of the lost nervous tissue, mainly due to the formation of a scar. One promising strategy to overcome this hurdle is grafting scaffolds that can disturb the scar blockade, enabling cell invasion into the wound. The aragonite skeleton of corals is useful scaffolds for testing this strategy, being supportive for neural cells in culture. The purpose of this work was to check if a contact between a coralline scaffold and an injured nervous tissue affects scar formation and if this effect can be regulated by engineering the scaffold's surface topology. To address that, hippocampal slices were cultivated on a coral skeleton having two distinct surface shapes: (1) intact skeleton pieces (ISP): porous, microrough surface; (2) grained skeleton (GS): nonporous, macrorough surface. On ISP, slices deformed by engulfing the scaffold's outer surface without penetrating the pores, yet, they preserved their coherence. By contrast, on GS slices were flat, but broken into interconnected small segments of tissue. In addition, whereas on ISP astrocytes were significantly more active and diffusely distributed, on GS reactive astrocytes tightened into a single <90 μm wide scar-like stripe at the slice's periphery. Hence, by grafting coralline scaffolds of predesigned surface roughness and porosity into brain wounds, control over scar tissue formation can be gained, providing an opportunity for cell migration and damage repair. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 2295-2306, 2018.

Next generation organoids for biomedical research and applications

Organoids are in vitro cultures of miniature fetal or adult organ-like structures. Their potentials for use in tissue and organ replacement, disease modeling, toxicology studies, and drug discovery are tremendous. Currently, major challenges facing human organoid technology include (i) improving the range of cellular heterogeneity for a particular organoid system, (ii) mimicking the native micro- and matrix-environment encountered by cells within organoids, and (iii) developing robust protocols for the in vitro maturation of organoids that remain mostly fetal-like in cultures. To tackle these challenges, we advocate the principle of reverse engineering that replicates the inner workings of in vivo systems with the goal of achieving functionality and maturation of the resulting organoid structures with the input of minimal intrinsic (cellular) and environmental (matrix and niche) constituents. Here, we present an overview of organoid technology development in several systems that employ cell materials derived from fetal and adult tissues and pluripotent stem cell cultures. We focus on key studies that exploit the self-organizing property of embryonic progenitors and the role of designer matrices and cell-free scaffolds in assisting organoid formation. We further explore the relationship between adult stem cells, niche factors, and other current developments that aim to enhance robust organoid maturation. From these works, we propose a standardized pipeline for the development of future protocols that would help generate more physiologically relevant human organoids for various biomedical applications.

Flexible and highly interconnected, multi-scale patterned chitosan porous membrane produced in situ from mussel shell to accelerate wound healing

Mussel shell-derived dressing for full-thickness wound healing. The mussel shell-derived, in situ formed flexible membrane dressing promotes wound healing processes.

Hypertrophic scarring: the greatest unmet challenge after burn injury

Improvements in acute burn care have enabled patients to survive massive burns that would have once been fatal. Now up to 70% of patients develop hypertrophic scars after burns. The functional and psychosocial sequelae remain a major rehabilitative challenge, decreasing quality of life and delaying reintegration into society. Approaches to optimise healing potential of burn wounds use targeted wound care and surgery to minimise the development of hypertrophic scarring. Such approaches often fail, and modulation of the established scar is continued although the optimal indication, timing, and combination of therapies have yet to be established. The need for novel treatments is paramount, and future efforts to improve outcomes and quality of life should include optimisation of wound healing to attenuate or prevent hypertrophic scarring, well-designed trials to confirm treatment efficacy, and further elucidation of molecular mechanisms to allow development of new preventive and therapeutic strategies.