A Comparative Study of Engineered Dermal Templates for Skin Wound Repair in a Mouse Model

Long-Term Histological Evaluation of a Novel Dermal Template in the Treatment of Pediatric Burns

For pediatric patients with full-thickness burns, achieving adequate dermal regeneration is essential to prevent inelastic scars that may hinder growth. Traditional autologous split-thickness skin grafts alone often fail to restore the dermal layer adequately. This study evaluates the long-term effect of using a NovoSorb® Biodegradable Temporizing Matrix (BTM) as a dermal scaffold in four pediatric patients, promoting dermal formation before autografting. Pediatric burn patients treated at the University Children's Hospital Zurich between 2020 and 2022 underwent a two-step treatment involving NovoSorb® BTM application, followed by autografting. Histological analysis, conducted through 22 punch biopsies taken up to 2.6 years post-application, demonstrated robust dermal reorganization, with mature epidermal regeneration and stable dermo-epidermal connections. Immunofluorescence staining showed rapid capillary ingrowth, while extracellular matrix components, including collagen and elastic fibers, gradually aligned over time, mimicking normal skin structure. By 2.6 years, the dermal layer displayed characteristics close to uninjured skin, with remnants of NovoSorb® BTM degrading within five months post-application. This study suggests that NovoSorb® BTM facilitates elastic scar formation, offering significant benefits for pediatric patients by reducing functional limitations associated with inelastic scarring.

Enhanced Wound Healing and Autogenesis Through Lentiviral Transfection of Adipose-Derived Stem Cells Combined with Dermal Substitute

BACKGROUND

Burns and chronic ulcers may cause severe skin loss, leading to critical health issues like shock, infection, sepsis, and multiple organ failure. Effective healing of full-thickness wounds may be challenging, with traditional methods facing limitations due to tissue shortage, infection, and lack of structural support.

METHODS

This study explored the combined use of gene transfection and dermal substitutes to improve wound healing. We used the DGTM (genes: DNP63A, GRHL2, TFAP2A, and MYC) factors to transfect adipose-derived stem cells (ADSCs), inducing their differentiation into keratinocytes. These transfected ADSCs were then incorporated into Pelnac® dermal substitutes to enhance vascularization and cellular proliferation for better healing outcomes.

RESULTS

Gene transfer using DGTM factors successfully induced keratinocyte differentiation in ADSCs. The application of these differentiated cells with Pelnac® dermal substitute to dermal wounds in mice resulted in the formation of skin tissue with a normal epidermal layer and proper collagen organization. This method alleviates the tediousness of the multiple transfection steps in previous protocols and the safety issues caused by using viral transfection reagents directly on the wound. Additionally, the inclusion of dermal substitutes addressed the lack of collagen and elastic fibers, promoting the formation of tissue resembling healthy skin rather than scar tissue.

CONCLUSION

Integrating DGTM factor-transfected ADSCs with dermal substitutes represents a novel strategy for enhancing the healing of full-thickness wounds. Further research and clinical trials are warranted to optimize and validate this innovative approach for broader clinical applications.

Advancements in skin grafting: Development and application of a novel two-blade dermatome for concurrent split-thickness and dermal graft harvesting

This investigation delineates the evolution and prospective utilisation of an innovative two-blade dermatome, designed for the concurrent harvesting of a conventional split-thickness skin graft (STSG) and an additional dermal graft within the same surgical harvest. Historically, the extraction of dermal grafts has encountered substantial technical impediments, contributing to its limited acceptance and utilisation in clinical practice. The prototype dermatome, introduced in this technical note, offers a solution that could facilitate the more extensive adoption of dermal grafting techniques. The dermal segment of an STSG, obtained as a second graft, confers four notable advancements: First, employing solely the dermal component for grafting and repositioning the uppermost skin flap to the donor site, markedly diminishes donor site morbidity. Second, owing to its elasticity, the dermal graft reduces the need for meshing, thereby enhancing cosmetic outcomes. Third, utilising both the uppermost skin layer and a deeper dermal layer for the recipient site can reduce donor site areas. Fourth, the dermal segment of the graft can serve as a dermal matrix in reconstructive procedures, potentially reducing the need for an allogenic dermal matrix and obviating the subsequent STSG; the dermal graft may heal independently, eliminating the need for an additional conventional STSG. The findings of this study, predicated on the application of a first-generation two-blade dermatome on four cadavers, demonstrate the feasibility of extracting at least two distinct grafts with pre-determined thicknesses in a single, technically less challenging, surgical harvest procedure. In conclusion, this proof-of-concept research elucidates the feasibility of a two-blade dermatome, capable of simultaneously yielding at least one conventional STSG and one dermal graft, thereby simplifying skin graft harvesting. Although these preliminary investigations were conducted on human cadavers, the results hold promise for the development of two-blade dermatomes and represent a significant advancement in skin graft harvesting. Further research is imperative to refine the prototype and to broaden our comprehension of the potential applications of dermal grafting in various clinical scenarios.

Novosorb® BTM- history, production and application in challenging wounds

Novosorb® Biodegradable Temporising Matrix (BTM) is an entirely synthetic dermal matrix that is gaining popularity in the management of challenging wounds. Not only does it provide a framework in which to grow an organised neodermis, it is also especially resistant to infection. Today, the matrix is available as a 2 mm thick open cell polyurethane foam with a non-degrading sealing membrane. Its current form is the result of numerous in vitro and in vivo experiments that examined its shape, biodegradation, inflammatory response, and cytotoxicity. Clinical data on the use of BTM in a variety of cases is novel and presents early insights into its ability to foster wound healing where otherwise improbable. This review presents the history and development of Novosorb® BTM as well as all the currently available clinical data on its efficacy in difficult wounds such as: major burns, necrotising soft tissue infection, chronic wounds and in non graftable wound beds.

Biodegradable Temporising matrix in the reconstruction of complex wounds: A systematic review and meta-analysis

OBJECTIVE

To assess the efficacy of biodegradable temporising matrix (BTM) in complex wound reconstruction.

METHODS

The authors conducted a systematic review and meta-analysis as per the preferred reporting items for systematic review and meta-analysis (PRISMA) guidelines following a literature search assessing BTM in complex wound reconstruction. The primary outcome measures included the proportion of BTM integration as well as integration time. Secondary outcomes included graft take over BTM, infection rate and other complications as well as scar outcome.

RESULTS

Twenty six studies met the inclusion criteria with a total of 1153 complex wounds. The mean proportional integration was 92.7% at (95% confidence intervals [CI] 88.57, 96.87, p < 0.001) with a mean integration time of 34.05 days (95% CI 33.33, 34.79, p < 0.001). The infection rate was low at 12.6% with an untransformed proportion metric assessment (0.126, 0.08-0.168, p < 0.001) at the site of BTM application. Favourable scar outcomes were reported using the matching assessment using photographs with scars (MAPS) and patient and observer scar assessment scales (POSAS).

CONCLUSION

BTM offers a robust dermal template in reconstruction of complex wounds. The authors recommend for randomised controlled trials to enhance the current evidence base.

Strategic Use of Biodegradable Temporizing Matrix (BTM) in Wound Healing: A Case Series in Asian Patients

Skin and soft tissue reconstruction has long been based on the reconstructive ladder. However, a skin substitute has become popular due to its predictable outcomes, without donor-site morbidity. The biodegradable temporizing matrix (BTM; NovoSorb, PolyNovo Ltd., Port Melbourne, Australia) is a synthetic skin substitute that has recently gained its clinical application. Compared with those of other dermal templates, the clinical efficacy and performance of the BTM are not well established, especially among the Asian population. This study aims to share our experience and strategy of using BTM in various wound conditions. The data of patients who underwent skin and soft tissue reconstruction with BTM at a single institution between January 2022 and December 2023 were reviewed. The patient demographics, wound characteristics, surgical details, secondary procedures, and complications were recorded and analyzed. Postoperative 6-month photographs were collected and independently evaluated by two plastic surgeons and two wound care center nurses using the Manchester Scar Scale (MSS). This study included 37 patients, consisting of 22 males and 15 females with a mean age of 51.8 years (range, 18-86 years old). The wound etiologies included trauma (67.6%), necrotizing soft tissue infection (16.2%), burns (10.8%), toe gangrene (2.7%), and scar excision (2.7%). The average wound area covered by BTM was 50.6 ± 47.6 cm2. Among the patients, eight received concomitant flap surgery and BTM implantation, 20 (54.1%) underwent subsequent split-thickness skin grafts (STSG), and 17 had small wounds (mean: 21.6 cm2) healed by secondary intention. Infection was the most common complication, affecting six patients (n = 6 [16.2%]), five of whom were treated conservatively, and only one required debridement. Thirty-three patients (89.2%) had good BTM take, and only four had BTM failure, requiring further reconstruction. At the last follow-up, 35 out of the 37 patients (94.6%) achieved successful wound closure, and the total MSS score was 10.44 ± 2.94, indicating a satisfactory scar condition. The patients who underwent BTM grafting without STSG had better scar scores than those who received STSG (8.71 ± 2.60 vs. 11.18 ± 2.84, p = 0.039). In conclusion, the BTM is effective and feasible in treating various wounds, with relatively low complication rates, and it can thus be considered as an alternative for skin and soft tissue reconstruction. When combined with adipofasical flap reconstruction, it achieves a more comprehensive anatomical restoration.

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.

Graft-Host Interaction and Its Effect on Wound Repair Using Mouse Models

Autologous skin grafting has been commonly used in clinics for decades to close large wounds, yet the cellular and molecular interactions between the wound bed and the graft that mediates the wound repair are not fully understood. The aim of this study was to better understand the molecular changes in the wound triggered by autologous and synthetic grafting. Defining the wound changes at the molecular level during grafting sets the basis to test other engineered skin grafts by design. In this study, a full-thickness skin graft (SKH-1 hairless) mouse model was established. An autologous full-thickness skin graft (FTSG) or an acellular fully synthetic Biodegradable Temporising Matrix (BTM) was grafted. The wound bed/grafts were analysed at histological, RNA, and protein levels during the inflammation (day 1), proliferation (day 5), and remodelling (day 21) phases of wound repair. The results showed that in this mouse model, similar to others, inflammatory marker levels, including Il-6, Cxcl-1, and Cxcl-5/6, were raised within a day post-wounding. Autologous grafting reduced the expression of these inflammatory markers. This was different from the wounds grafted with synthetic dermal grafts, in which Cxcl-1 and Cxcl-5/6 remained significantly high up to 21 days post-grafting. Autologous skin grafting reduced wound contraction compared to wounds that were left to spontaneously repair. Synthetic grafts contracted significantly more than FTSG by day 21. The observed wound contraction in synthetic grafts was most likely mediated at least partly by myofibroblasts. It is possible that high TGF-β1 levels in days 1-21 were the driving force behind myofibroblast abundance in synthetic grafts, although no evidence of TGF-β1-mediated Connective Tissue Growth Factor (CTGF) upregulation was observed.

Design matters: A comparison of natural versus synthetic skin substitutes across benchtop and porcine wound healing metrics: An experimental study

Background and Aims

Skin substitutes, essential tools for helping close full thickness wounds with minimal scarring, are available in both collagen-based and synthetic polyurethane constructions. Here we explore fundamental differences between two frequently used skin substitutes and discuss how these differences may impact in vivo performance.

Methods

Polyurethane- and collagen-based matrices were characterized in vitro for pore size via scanning electron microscopy, hydrophobicity via liquid contact angle, conformability via bending angle, and biocompatibility via fibroblast and keratinocyte adhesion and proliferation. These matrices were then evaluated in a full-thickness excisional pig wound study followed by histological analysis. Statistical analysis was performed using t-tests or one-way analysis of variances with Tukey's multiple post hoc comparisons, where appropriate.

Results

Average pore diameter in the tested polyurethane matrix was over four times larger than that of the collagen matrix (589 ± 297 µm vs. 132 ± 91 µm). Through liquid contact angle measurement, the collagen matrix (not measurable) was found to be hydrophilic compared to the hydrophobic polyurethane matrix (>90°). The collagen matrix was significantly more conformable than the polyurethane matrix (9 ± 2° vs. 84 ± 5° bending angle, respectively). Fibroblast and keratinocyte adhesion and proliferation assays elucidated a significantly greater ability of both cell types to attach and proliferate on collagen versus polyurethane. While the porcine study showed minimal contraction of either matrix material, histological findings between the two treatments were markedly different. Collagen matrices were associated with early fibroblast infiltration and fibroplasia, whereas polyurethane matrices elicited a strong multinucleated giant cell response and produced a network of comparatively aligned collagen fibrils.

Conclusions

The more favorable in vitro properties of the collagen matrix led to less inflammation and better overall tissue response in vivo. Overall, our findings demonstrate how the choice of biomaterial and its design directly translate to differing in vivo mechanisms of action and overall tissue quality.

Molecular Mechanisms Related to Burns, Burn Wound Healing and Scarring

The process of burn injury is multifaceted and involves a whole spectrum of inflammatory responses that can have significant implications for burn patients, including local, regional, and systemic effects [...].

Engineered multi-functional, pro-angiogenic collagen-based scaffolds loaded with endothelial cells promote large deep burn wound healing

The lack of vascularization associated with deep burns delays the construction of wound beds, increases the risks of infection, and leads to the formation of hypertrophic scars or disfigurement. To address this challenge, we have fabricated a multi-functional pro-angiogenic molecule by grafting integrin αvβ3 ligand LXW7 and collagen-binding peptide (SILY) to a dermatan sulfate (DS) glycosaminoglycan backbone, named LXW7-DS-SILY (LDS), and further employed this to functionalize collagen-based Integra scaffolds. Using a large deep burn wound model in C57/BLK6 mice (8-10 weeks old, 26-32g, n = 39), we demonstrated that LDS-modified collagen-based Integra scaffolds loaded with endothelial cells (ECs) accelerate wound healing rate, re-epithelialization, vascularization, and collagen deposition. Specifically, a 2 cm × 3 cm full-thickness skin burn wound was created 48 h after the burn, and then wounds were treated with four groups of different dressing scaffolds, including Integra + ECs, Integra + LDS, and Integra + LDS + ECs with Integra-only as the control. Digital photos were taken for wound healing measurement on post-treatment days 1, 7, 14, 21, 28, and 35. Post-treatment photos revealed that treatment with the Intgera + LDS + ECs scaffold exhibited a higher wound healing rate in the proliferation phase. Histology results showed significantly increased re-epithelialization, increased collagen deposition, increased thin and mixed collagen fiber content, increased angiogenesis, and shorter wound length within the Integra + LDS + ECs group at Day 35. On Day 14, the Integra + LDS + ECs group showed the same trend. The relative proportions of collagen changed from Day 14 to Day 35 in the Integra + LDS + ECs and Integra + ECs groups demonstrated decreased thick collagen fiber deposition and greater thin and mixed collagen fiber deposition. LDS-modified Integra scaffolds represent a promising novel treatment to accelerate deep burn wound healing, thereby potentially reducing the morbidity associated with open burn wounds. These scaffolds can also potentially reduce the need for autografting and morbidity in patients with already limited areas of harvestable skin.

LEP and LEPR are possibly a double-edged sword for wound healing

Wound healing is a complex and error-prone process. Wound healing in adults often leads to the formation of scars, a type of fibrotic tissue that lacks skin appendages. Hypertrophic scars and keloids can also form when the wound-healing process goes wrong. Leptin (Lep) and leptin receptors (LepRs) have recently been shown to affect multiple stages of wound healing. This effect, however, is paradoxical for scarless wound healing. On the one hand, Lep exerts pro-inflammatory and profibrotic effects; on the other hand, Lep can regulate hair follicle growth. This paper summarises the role of Lep and LepRs on cells in different stages of wound healing, briefly introduces the process of wound healing and Lep and LepRs, and examines the possibility of promoting scarless wound healing through spatiotemporal, systemic, and local regulation of Lep levels and the binding of Lep and LepRs.

Understanding the mechanisms of spontaneous and skin-grafted wound repair: the path to engineered skin grafts

Spontaneous wound repair is a complex process that involves overlapping phases of inflammation, proliferation and remodelling, co-ordinated by growth factors and proteases. In extensive wounds such as burns, the repair process would not be achieved in a timely fashion unless grafted. Although spontaneous wound repair has been extensively described, the processes by which wound repair mechanisms mediate graft take are yet to be fully explored. This review describes engraftment stages and summarises current understanding of molecular mechanisms which regulate autologous skin graft healing, with the goal of directing innovation in permanent wound closure with skin substitutes. Graftability and vascularisation of various skin substitutes that are either in the market or in development phase are discussed. In doing so, we cast a spotlight on the paucity of scientific information available as to how skin grafts (both autologous and engineered) heal a wound bed. Better understanding of these processes may assist in developing novel methods of wound management and treatments.

Comparison of biopolymer scaffolds for the fabrication of skin substitutes in a porcine wound model

This study compared three acellular scaffolds as templates for the fabrication of skin substitutes. A collagen-glycosaminoglycan (C-GAG), a biodegradable polyurethane foam (PUR) and a hybrid combination (PUR/C-GAG) were investigated. Scaffolds were prepared for cell inoculation. Fibroblasts and keratinocytes were serially inoculated onto the scaffolds and co-cultured for 14 days before transplantation. Three pigs each received four full-thickness 8 cm × 8 cm surgical wounds, into which a biodegradable temporising matrix (BTM) was implanted. Surface seals were removed after integration (28 days), and three laboratory-generated skin analogues and a control split-thickness skin graft (STSG) were applied for 16 weeks. Punch biopsies confirmed engraftment and re-epithelialisation. Biophysical wound parameters were also measured and analysed. All wounds showed greater than 80% epithelialisation by day 14 post-transplantation. The control STSG displayed 44% contraction over the 16 weeks, and the test scaffolds, C-GAG 64%, Hybrid 66.7% and PUR 67.8%. Immunohistochemistry confirmed positive epidermal keratins and basement membrane components (Integrin alpha-6, collagens IV and VII). Collagen deposition and fibre organisation indicated the degree of fibrosis and scar produced for each graft. All scaffold substitutes re-epithelialised by 4 weeks. The percentage of original wound area for the Hybrid and PUR was significantly different than the STSG and C-GAG, indicating the importance of scaffold retainment within the first 3 months post-transplant. The PUR/C-GAG scaffolds reduced the polymer pore size, assisting cell retention and reducing the contraction of in vitro collagen. Further investigation is required to ensure reproducibility and scale-up feasibility.

Insight into the role of DPP-4 in fibrotic wound healing

Wound healing is a complex and long-term process consisting of hemostasis, inflammation, proliferation, and maturation/remodeling. These four stages overlap and influence each other; they affect wound healing in different ways, and if they do not function perfectly, they may cause scarring, proliferative scarring and keloid formation. A therapeutic target affecting wound healing in multiple ways will help the healing process proceed more effectively. DPP-4/CD26 is a multifunctional dimorphic glycoprotein widely distributed on the surface of a variety of cells, including fibroblasts and keratin-forming cells. It has been found to affect periwound inflammation, re-epithelialization, extracellular matrix secretion and skin fibrosis and is a potential target for promoting wound healing and inhibiting scar formation. After presenting a brief introduction of the wound healing process and DPP-4/CD26, this paper summarizes the effects of DPP-4/CD26 on cells involved in different stages of wound healing and discusses the feasibility of DPP-4/CD26 as a multifunctional target for the treatment of wound healing and inhibition of scar formation.

A platelet-derived hydrogel improves neovascularisation in full thickness wounds

Platelets are a reservoir of growth factors, cytokines and chemokines involved in spontaneous wound repair. In this study, a platelet-rich and fibrin-rich hydrogel was generated from expired platelet components that would have otherwise been transfused. The material contained physiological concentrations of transforming growth factor β1 (TGF-β1, platelet-derived growth factor AB (PDGF-AB), PDGF-BB, insulin-like growth factor-1 (IGF-1), fibroblast growth factor 2 (FGF-2), and epidermal growth factor (EGF). The effect of the hydrogel on wound repair was investigated in SKH-1 mice. Full thickness dorsal wounds were created on the mice and treated with the hydrogel at various concentrations. Immunohistochemical staining with CD31 (endothelial cell marker) revealed that wounds treated with the hydrogel showed significantly enhanced vascularisation in the wound bed. Moreover, high levels of interleukin-6 (IL-6) and KC (IL-8 functional homologue) in treated wounds were sustained over a longer period of time, compared to untreated wounds. We postulate that sustained IL-6 is a driver, at least partly, of enhanced vascularisation in full thickness wounds treated with the hydrogel. Future work is needed to explore whether this hydrogel can be utilised as a treatment option when vascularisation is a critical limitation. STATEMENT OF SIGNIFICANCE: The economic cost of wound repair is estimated in billions of dollars each year. In many cases time required to vascularise wounds is a major contributor to slow wound repair. In this study, we developed a blood-derived platelet- and fibrin-rich hydrogel. It contains a number of growth factors actively involved in spontaneous wound healing. This hydrogel significantly improved dermal repair and vascularisation in a full-thickness wound mouse model. This study provides an action mechanism for modulation of localised inflammation.