Adipose-Derived Stromal Cells Seeded on Integra® Dermal Regeneration Template Improve Post-Burn Wound Reconstruction

Combination therapy of placenta-derived mesenchymal stem cells and artificial dermal scaffold promotes full-thickness skin defects vascularization in rat animal model

PURPOSE

Recently, placenta-derived mesenchymal stem cells (PMSCs) have garnered considerable attention in tissue repair and regeneration. The present study was conducted to evaluate the effect of PMSCs on artificial dermal scaffold (ADS) angiogenesis and their combination therapy on wound closure.

MATERIAL AND METHODS

Herein, the growth and survival of PMSCs in ADS were explored. CCK8, scratch wound, and tubule formation assays were employed to investigate the effects of ADS conditioned medium (CM) and ADS-PMSCs CM on human umbilical vein endothelial cells (HUVECs). The effect of ADS-PMSCs on full-thickness skin defects healing was evaluated based on a rat model. Wound healing progresses was meticulously investigated through hematoxylin and eosin (HE), Masson's trichrome, and immunohistochemical staining analyses.

RESULTS

In vitro cell culture results demonstrated the proliferation of PMSCs in ADS. The ADS-PMSCs CM notably stimulated the proliferation, migration, and tube formation of HUVECs compared to the ADS CM group. In the rat full-thickness skin defect model, the ADS-PMSCs treatment significantly accelerated the vascularization area of ADS after 2 weeks. Besides, HE and Masson's trichrome staining results indicated that ADS-PMSCs treatment significantly enhanced fibroblast proliferation and collagen fiber 2 weeks after surgical procedure. Compared to the ADS group, collagen fiber arrangement was thicker in the ADS-PMSCs group. Immunohistochemical staining reinforced this finding, illustrating a substantial increase in CD31 expression within the ADS-PMSCs group.

CONCLUSIONS

The results suggest that the combination of ADS with PMSCs accelerates ADS vascularization by fostering granulation tissue development and boosting the formation of new blood vessels.

Unusual cell-cell cooperative mechanical activity elucidates the process of tissue regeneration

We have studied wound contraction in three model wounds in animals: excised skin (guinea pig), transected peripheral nerve (rat) and the excised conjunctiva (rabbit). Wound contraction is driven by myofibroblasts bound together by adherens junctions (AJ) that confer cooperative activity to myofibroblasts during wound contraction and synthesis of scar. Grafting with the dermis regeneration template (DRT) cancels cell cooperativity by abolishing AJ connections in myofibroblasts, while also cancelling wound contraction, preventing synthesis of scar and inducing regeneration of excised tissues. The observed definitive prevention of scar synthesis suggests the exploration of DRT scaffolds to regenerate tissues in several other organs and to prevent fibrosis in humans.

Bioengineering Skin Substitutes for Wound Management-Perspectives and Challenges

Non-healing wounds and skin losses constitute significant challenges for modern medicine and pharmacology. Conventional methods of wound treatment are effective in basic healthcare; however, they are insufficient in managing chronic wound and large skin defects, so novel, alternative methods of therapy are sought. Among the potentially innovative procedures, the use of skin substitutes may be a promising therapeutic method. Skin substitutes are a heterogeneous group of materials that are used to heal and close wounds and temporarily or permanently fulfill the functions of the skin. Classification can be based on the structure or type (biological and synthetic). Simple constructs (class I) have been widely researched over the years, and can be used in burns and ulcers. More complex substitutes (class II and III) are still studied, but these may be utilized in patients with deep skin defects. In addition, 3D bioprinting is a rapidly developing method used to create advanced skin constructs and their appendages. The aforementioned therapies represent an opportunity for treating patients with diabetic foot ulcers or deep skin burns. Despite these significant developments, further clinical trials are needed to allow the use skin substitutes in the personalized treatment of chronic wounds.

Dermal Regeneration Template in the Management and Reconstruction of Burn Injuries and Complex Wounds: A Review

Background

Dermal scaffolds have created a paradigm shift for burn and wound management by providing improved healing and less scarring, while improving cosmesis and functionality. Dermal regeneration template (DRT) is a bilayer membrane for dermal regeneration developed by Yannas and Burke in the 1980s. The aim of this review is to summarize clinical evidence for dermal scaffolds focusing on DRT for the management and reconstruction of burn injuries and complex wounds.

Methods

A comprehensive search of PubMed was performed from the start of indexing through November 2022. Articles reporting on DRT use in patients with burns, limb salvage, and wound reconstruction were included with focus on high-level clinical evidence.

Results

DRT has become an established alternative option for the treatment of full-thickness and deep partial-thickness burns, with improved outcomes in areas where cosmesis and functionality are important. In the management of diabetic foot ulcers, use of DRT is associated with high rates of complete wound healing with a low risk of adverse outcomes. DRT has been successfully used in traumatic and surgical wounds, showing particular benefit in deep wounds and in the reconstruction of numerous anatomical sites.

Conclusions

Considerable clinical experience has accrued with the use of DRT beyond its original application for thermal injury. A growing body of evidence from clinical studies reports the successful use of DRT to improve clinical outcomes and quality of life across clinical indications at a number of anatomical sites.

Human Placenta-Derived Mesenchymal Stem Cells Combined With Artificial Dermal Scaffold Enhance Wound Healing in a Tendon-Exposed Wound of a Rabbit Model

To overcome the difficulty of vascular regeneration in exposed tendon wounds, we combined human placenta-derived mesenchymal stem cells (hPMSCs) with an artificial dermal scaffold and assessed their role in promoting vascular regeneration and wound healing in vivo. hPMSCs were isolated from the human placenta and characterized based on their morphology, phenotypic profiles, and pluripotency. New Zealand rabbits were used to establish an exposed tendon wound model, and hPMSCs and artificial dermal scaffolds were transplanted into the wounds. The results of gross wound observations and pathological sections showed that hPMSCs combined with artificial dermal scaffold transplantation increased the vascularization area of the wound, promoted wound healing, and increased the survival rate of autologous skin transplantation. Following artificial dermal scaffold transplantation, hPMSCs accelerated the vascularization of the dermal scaffold, and the number of fibroblasts, collagen fibers, and neovascularization in the dermal scaffold after 1 week were much higher than those in the control group. Immunohistochemical staining further confirmed that the expression of the vascular endothelial cell marker, CD31, was significantly higher in the combined transplantation group than in the dermal scaffold transplantation group. Our findings demonstrated that hPMSCs seeded onto artificial dermal scaffold could facilitate vascularization of the dermal scaffold and improve tendon-exposed wound healing.

Bioengineered skin constructs based on mesenchymal stromal cells and acellular dermal matrix exposed to inflammatory microenvironment releasing growth factors involved in skin repair

BACKGROUND

Skin tissue engineering is a rapidly evolving field of research that effectively combines stem cells and biological scaffolds to replace damaged tissues. Human Wharton's jelly mesenchymal stromal cells (hWJ-MSCs) are essential to generate tissue constructs, due to their potent immunomodulatory effects and release of paracrine factors for tissue repair. Here, we investigated whether hWJ-MSC grown on human acellular dermal matrix (hADM) scaffolds and exposed to a proinflammatory environment maintain their ability to produce in vitro growth factors involved in skin injury repair and promote in vivo wound healing.

METHODS

We developed a novel method involving physicochemical and enzymatic treatment of cadaveric human skin to obtain hADM scaffold. Subsequently, skin bioengineered constructs were generated by seeding hWJ-MSCs on the hADM scaffold (construct 1) and coating it with human platelet lysate clot (hPL) (construct 2). Either construct 1 or 2 were then incubated with proinflammatory cytokines (IL-1α, IL-1β, IL-6, TNF-α) for 12, 24, 48, 72 and 96 h. Supernatants from treated and untreated constructs and hWJ-MSCs on tissue culture plate (TCP) were collected, and concentration of the following growth factors, bFGF, EGF, HGF, PDGF, VEGF and Angiopoietin-I, was determined by immunoassay. We also asked whether hWJ-MSCs in the construct 1 have potential toward epithelial differentiation after being cultured in an epithelial induction stimulus using an air-liquid system. Immunostaining was used to analyze the synthesis of epithelial markers such as filaggrin, involucrin, plakoglobin and the mesenchymal marker vimentin. Finally, we evaluated the in vivo potential of hADM and construct 1 in a porcine full-thickness excisional wound model.

RESULTS

We obtained and characterized the hADM and confirmed the viability of hWJ-MSCs on the scaffold. In both constructs without proinflammatory treatment, we reported high bFGF production. In contrast, the levels of other growth factors were similar to the control (hWJ-MSC/TCP) with or without proinflammatory treatment. Except for PDGF in the stimulated group. These results indicated that the hADM scaffold maintained or enhanced the production of these bioactive molecules by hWJ-MSCs. On the other hand, increased expression of filaggrin, involucrin, and plakoglobin and decreased expression of vimentin were observed in constructs cultured in an air-liquid system. In vivo experiments demonstrated the potential of both hADM and hADM/hWJ-MSCs constructs to repair skin wounds with the formation of stratified epithelium, basement membrane and dermal papillae, improving the appearance of the repaired tissue.

CONCLUSIONS

hADM is viable to fabricate a tissue construct with hWJ-MSCs able to promote the in vitro synthesis of growth factors and differentiation of these cells toward epithelial lineage, as well as, promote in a full-thickness skin injury the new tissue formation. These results indicate that hADM 3D architecture and its natural composition improved or maintained the cell function supporting the potential therapeutic use of this matrix or the construct for wound repair and providing an effective tissue engineering strategy for skin repair.

Acellular collagen-glycosaminoglycan matrix promotes functional recovery in a rat model of volumetric muscle loss

Aim: Volumetric muscle loss (VML) is a composite loss of skeletal muscle, which heals with fibrosis, minimal muscle regeneration, and incomplete functional recovery. This study investigated whether collagen-glycosaminoglycan scaffolds (CGS) improve functional recovery following VML. Methods: 15 Sprague-Dawley rats underwent either sham injury or bilateral tibialis anterior (TA) VML injury, with or without CGS implantation. Results: In rats with VML injuries treated with CGS, the TA exhibited greater in vivo tetanic forces and in situ twitch and tetanic dorsiflexion forces compared with those in the non-CGS group at 4- and 6-weeks following injury, respectively. Histologically, the VML with CGS group demonstrated reduced fibrosis and increased muscle regeneration. Conclusion: Taken together, CGS implantation has potential augment muscle recovery following VML.

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.

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.

Mesenchymal Stem Cells in Burn Wound Management

Mesenchymal stem cells have a known regenerative potential and are used in many indications. They secrete many growth factors, including for fibroblasts (FGF), endothelium (VEGF), as well as 14 anti-inflammatory cytokines, and they stimulate tissue regeneration, promoting the secretion of proteins and glycosaminoglycans of extracellular matrices, such as collagen I, II, III, and V, elastin, and also metalloproteinases. They secrete exosomes that contain proteins, nucleic acids, lipids, and enzymes. In addition, they show the activity of inactivating free radicals. The aim of this study was an attempt to collect the existing literature on the use of stem cells in the treatment of a burn wound. There were 81 studies included in the analysis. The studies differed in terms of the design, burn wound model, source of stem cells, and methods of cellular therapy application. No major side effects were reported, and cellular therapy reduced the healing time of the burn wound. Few case reports on human models did not report any serious adverse events. However, due to the heterogeneity of the evidence, cellular therapy in burn wound treatment remains an experimental method.

Cutaneous Wound Healing: An Update from Physiopathology to Current Therapies

The skin is the biggest organ of human body which acts as a protective barrier against deleterious agents. When this barrier is damaged, the organism promotes the healing process with several molecular and cellular mechanisms, in order to restore the physiological structure of the skin. The physiological control of wound healing depends on the correct balance among its different mechanisms. Any disruption in the balance of these mechanisms can lead to problems and delay in wound healing. The impairment of wound healing is linked to underlying factors as well as aging, nutrition, hypoxia, stress, infections, drugs, genetics, and chronic diseases. Over the years, numerous studies have been conducted to discover the correct approach and best therapies for wound healing, including surgical procedures and non-surgical treatments such as topical formulations, dressings, or skin substitutes. Thus, this general approach is necessary to facilitate the direction of further studies. This work provides updated concepts of physiological mechanisms, the factors that can interfere, and updated treatments used in skin wound healing.

Local Treatment of Burns with Cell-Based Therapies Tested in Clinical Studies

Effective wound management is an important determinant of the survival and prognosis of patients with severe burns. Thus, novel techniques for timely and full closure of full-thickness burn wounds are urgently needed. The purpose of this review is to present the current state of knowledge on the local treatment of burn wounds (distinguishing radiation injury from other types of burns) with the application of cellular therapies conducted in clinical studies. PubMed search engine and ClinicalTrials.gov were used to analyze the available data. The analysis covered 49 articles, assessing the use of keratinocytes (30), keratinocytes and fibroblasts (6), fibroblasts (2), bone marrow-derived cells (8), and adipose tissue cells (3). Studies on the cell-based products that are commercially available (Epicel^®, Keraheal™, ReCell^®, JACE, Biobrane^®) were also included, with the majority of reports found on autologous and allogeneic keratinocytes. Promising data demonstrate the effectiveness of various cell-based therapies; however, there are still scientific and technical issues that need to be solved before cell therapies become standard of care. Further evidence is required to demonstrate the clinical efficacy and safety of cell-based therapies in burns. In particular, comparative studies with long-term follow-up are critical.