A Surgical Device to Study the Efficacy of Bioengineered Skin Substitutes in Mice Wound Healing Models

UV-spectrophotometric and spectroscopic observed Vachellia nilotica and Nigella sativa formulations regularized the histopathological and biochemical parameters during wound contraction

Diabetes mellitus causes impaired diabetic wounds which is linked to a number of pathological alterations that impede the healing of wounds. In the current research, Swiss albino mice were given alloxan monohydrate to induce diabetes and excision wounds of approximately 6 mm using biopsy punch. The diabetic wounds were treated with various biomaterials including Vachellia nilotica extract (VN), Nigella sativa extract (NS), V. nilotica nanoparticles (VNNPs) and N. sativa nanoparticles (NSNPs). Their effects were determined by evaluating the percent wound contraction, healing time, and histopathological analysis. The serum level of various biochemical parameters that is, pro-inflammatory cytokines,  Matrix metalloproteinases (MMPs) and tissue inhibitor matrix metalloproteinases (TIMPs) were also determined. VNNPs group provided the best outcomes, with wound contraction 100% on 12th day. According to histopathological examination, VNNPs group reduced inflammation and encouraged the formation of blood vessels, fibroblasts, and keratinocytes. VNNPs group significantly alleviated the serum level of pro-inflammatory cytokines that are, TNF-α (19.4 ± 1.5 pg/mL), IL-6 (13.8 ± 0.6 pg/mL), and IL-8 (24.8 ± 1.2 pg/mL) as compared with the diabetic mice. The serum level of MMP2 (248.2 ± 7.9 pg/mL), MMP7 (316 ± 5.2 pg/mL), and MMP9 (167.8 ± 12.1 pg/mL) in the same group VNNPs were also observed much less than the diabetic mice. The serum level of TIMPs (176.8 ± 2.9 pg/mL) in the VNNPs group was increased maximally with respect to diabetic mice. It is concluded that nanoparticles and biomaterials possess healing properties and have the ability to repair the chronic/diabetic wound. RESEARCH HIGHLIGHTS: UV-spectrophotometric and Fourier transform infrared spectroscopy observation for functional group analysis and possible linkage between conjugates Optimization of the histopathological and biochemical markers after application of the formulations Microscopic analysis of epithelial tissues for evaluation of healing mechanisms Speedy contraction of wounds as the alleviation of the inflammatory and necrotic factors.

Therapeutic Applications of Garlic and Turmeric for the Diabetic Wound Healing in Mice

Diabetes is involved in delayed wound healing that can be cured by natural products such as garlic, turmeric, and fibroin extracts. Alloxan monohydrate is used for inducing diabetes in mice. The percent wound contraction of garlic (150 mg/ml), turmeric (100 mg/ml), and fibroin (50 mg/ml), individually and in combinations garlic (150 mg/ml) + fibroin (50 mg/ml), turmeric (100 mg/ml) + fibroin (50 mg/ml), garlic (150 mg/ml) + turmeric (100 mg/ml), and garlic (150 mg/ml) + turmeric (100 mg/ml) + fibroin (50 mg/ml) was checked by evaluating the healing time, % wound contraction and histological analysis. The serum level of MMPs (MMP 2, MMP7, MMP 9), pro-inflammatory cytokines (TNF-α, IL-6, IL-8), and TIMPs were evaluated. With the combination of three extracts (Ga+Tu+Fi) garlic (150 mg/ml), turmeric (100 mg/ml) and fibroin (50 mg/ml), wounds healed in 12 days and had 97.3 ± 2.2% wound contraction. While the positive control (polyfax) and diabetic control (saline) wounds healed in 17- and 19-days with wound contraction of 96.7 ± 1.4% and 96.3 ± 1.1%, respectively. Histological analysis showed that the combination of Ga+Tu+Fi exhibited an increase in the growth of collagen fibers, fibroblasts number, and keratinocytes, and lessened inflammation of blood vessels. The combination of Ga+Tu+Fi significantly alleviated the serum concentration of TNF-α (14.2 ± 0.7 pg/ml), IL-6 (10.0 ± 1.0 pg/ml), IL-8 (16.0 ± 1.5 pg/ml), MMP2 (228.0 ± 18.1 pg/ml), MMP7 (271.0 ± 9.9 pg/ml), and MMP9 (141.0 ± 5.3 pg/ml) to diabetic control. The level of TIMPs (193.0 ± 9.1 pg/ml) was increased significantly with respect to diabetic control. We conclude that the combination of these biomaterials possessed high regenerative and healing capabilities and can be an effective remedy in the healing of chronic wounds in diabetic patients.

Tie-Over Bolster Pressure Dressing Improves Outcomes of Skin Substitutes Xenografts on Athymic Mice

The efficacy of skin substitutes is established for the treatment of burn injuries, but its use is not limited to this condition. This technology has the potential to improve the treatment of various conditions by offering highly advanced and personalized treatments. In vivo studies are challenging but essential to move to clinical use in humans. Mice are the most widely used species in preclinical studies, but the main drawback of this model is the limited surface area of the graft in long-term transplantation studies caused by the displacement and the contraction of the graft. We improved the conventional surgical procedures by stabilizing the chamber covering the graft with intramuscular sutures and by adding a tie-over bolster dressing. The current study was therefore performed to compare outcomes of skin grafts between the conventional and optimized skin graft model. Human self-assembled skin substitutes (SASSs) were prepared and grafted to athymic mice either by the conventional method or by the new grafting method. Graft healing and complications were assessed using digital photographs on postoperative days 7, 14, and 21. Similar structure and organization were observed by histological staining. The new grafting method reduced medium and large displacement events by 1.26-fold and medium and large contraction events by 1.8-fold, leading to a 1.6-fold increase in graft surface area compared to skin substitutes grafted with the usual method. This innovation ensures better reproducibility and consistency of skin substitute transplants on mice.

Development and evaluation of drug delivery patch for topical wound healing application

Wound treatment remains a challenge to many clinicians because of the complexities of the wound healing process. With the astonishing progress of biomedical engineering during the past few decades, conventional drug delivery systems have been evolved into smart drug delivery systems with stimuli-responsive characteristics. The objective of this study was to develop and evaluate an electromechanically actuated drug dispensation device which can release active pharmaceutical compound in a controlled fashion. Additive manufacturing was employed to design and fabricate the device. Haptic technology was used to provide stimulation for drug release, and Cicatrin was used to evaluate the drug release patterns of device. Drug release study was comprised of in vitro drug release, static study, and the purpose of this study was to develop a compliance chart for different wound conditions. The effectiveness of shortlisted drug regimen from compliance chart was validated through microbial study and animal studies. The results of animal studies were compared with commercially available drug release systems. The results of drug release studies gave different dose regimens for different wound conditions. The effective dose regimen was able to create 1-cm-wide microbial zone of inhibitions. The wound healing rate of mice for commercially available release system for five consecutive days was 10%, 10%, 20%, 40% and 50% and for test device was 10%, 30%, 60%, 90% and 100%. Hence, the device proved its effectiveness and efficacy of dosage regimen for wound healing applications through in vitro, microbial and in vivo studies. In conclusion, this device proved to be an accurate and specific drug delivery system with improved medication and therapeutic outcomes for personalized medication.

Skin regeneration is accelerated by a lower dose of multipotent mesenchymal stromal/stem cells-a paradigm change

Background

Multipotent mesenchymal stromal/stem cell (MSC) therapy is under investigation in promising (pre-)clinical trials for wound healing, which is crucial for survival; however, the optimal cell dosage remains unknown. The aim was to investigate the efficacy of different low-to-high MSC dosages incorporated in a biodegradable collagen-based dermal regeneration template (DRT) Integra®.

Methods

We conducted a porcine study (N = 8 Yorkshire pigs) and seeded between 200 and 2,000,000 cells/cm² of umbilical cord mesenchymal stromal/stem cells on the DRT and grafted it onto full-thickness burn excised wounds. On day 28, comparisons were made between the different low-to-high cell dose groups, the acellular control, a burn wound, and healthy skin.

Result

We found that the low dose range between 200 and 40,000 cells/cm² regenerates the full-thickness burn excised wounds most efficaciously, followed by the middle dose range of 200,000–400,000 cells/cm² and a high dose of 2,000,000 cells/cm². The low dose of 40,000 cells/cm² accelerated reepithelialization, reduced scarring, regenerated epidermal thickness superiorly, enhanced neovascularization, reduced fibrosis, and reduced type 1 and type 2 macrophages compared to other cell dosages and the acellular control.

Conclusion

This regenerative cell therapy study using MSCs shows efficacy toward a low dose, which changes the paradigm that more cells lead to better wound healing outcome.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-020-02131-6.

Promotion of dermal regeneration using pullulan/gelatin porous skin substitute

Tissue-engineered dermal substitutes represent a promising approach to improve wound healing and provide more sufficient regeneration, compared with current clinical standards on care of large wounds, early excision, and grafting of autografts. However, inadequate regenerative capacity, impaired regeneration/degradation profile, and high cost of current commercial tissue-engineered dermal regeneration templates hinder their utilization, and the development of an efficient and cost-effective tissue-engineered dermal substitute remains a challenge. Inspired from our previously reported data on a pullulan/gelatin scaffold, here we present a new generation of a porous pullulan/gelatin scaffold (PG2) served as a dermal substitute with enhanced chemical and structural characteristics. PG2 shows excellent biocompatibility (viability, migration, and proliferation), assessed by in vitro incorporation of human dermal fibroblasts in comparison with the Integra® dermal regeneration template (Control). When applied on a mouse full-thickness excisional wound, PG2 shows rapid scaffold degradation, more granulation tissue, more collagen deposition, and more cellularity in comparison with Control at 20 days post surgery. The faster degradation is likely due to the enhanced recruitment of inflammatory macrophages to the scaffold from the wound bed, and that leads to earlier maturation of granulation tissue with less myofibroblastic cells. Collectively, our data reveal PG2's characteristics as an applicable dermal substitute with excellent dermal regeneration, which may attenuate scar formation.

Keratin scaffolds with human adipose stem cells: Physical and biological effects toward wound healing

Keratin, a natural biomaterial derived from wool or human hair, has the intrinsic ability to interact with different types of cells and the potential to serve as a controllable extracellular matrix that can be used a scaffold for tissue engineering. In this study, we demonstrated a simple and fast technique to construct 3D keratin scaffolds for accelerated wound healing using a lyophilization method based on extraction of keratin from human hair. The physical properties of the keratin scaffolds such as water uptake, pore size, and porosity can be adjusted by changing the protein concentrations during the fabrication process. The keratin scaffolds supported human adipose stem cells (hASCs) adhesion, proliferation, and differentiation. In vivo study performed on ICR mice showed that keratin scaffolds with hASCs shortened skin wound healing time, accelerated epithelialization, and promoted wound remodeling. Therefore, keratin scaffolds alone or together with hASCs may serve as therapeutic agents for repairing wounded tissue.

Immune tolerance of tissue-engineered skin produced with allogeneic or xenogeneic fibroblasts and syngeneic keratinocytes grafted on mice

Organs are needed for the long-term replacement of diseased or wounded tissues. Various technologies based on cells seeded in synthetic or biomaterial scaffolds, or scaffold-free methods have been developed in order to produce substitutes that mimic native organs and tissues. For cell-based approaches, the use of living allogeneic fibroblasts could potentially lead to the production of "off-the-shelf" bioengineered organs/tissues. However, questions remain regarding the outcome of allogeneic grafts in terms of persistence of allogeneic cells, tolerance and the host immune reaction against the tissue after implantation. To evaluate graft tolerance of engineered-tissues containing non-autologous fibroblasts, tissue-engineered skin substitutes (TESs) produced with syngeneic, allogeneic or xenogeneic fibroblasts associated with syngeneic, allogeneic or xenogeneic epithelial cells were grafted in mice as primary and secondary grafts. The immune response was evaluated by histological analysis and immunodetection of M2 macrophages, CD4- and CD8-positive T cells, 15, 19, 35 and 56 days after grafting. Tissue-engineered skin composed of non-autologous epithelial cells were rejected. In contrast, TESs composed of non-autologous fibroblasts underlying syngeneic epithelial cells were still present 56 days after grafting. This work shows that TES composed of non-autologous fibroblasts and autologous epithelial cells are not rejected after grafting. STATEMENT OF SIGNIFICANCE: We found that tissue-engineered skin substitutes produced by a scaffold-free cell-based approach from allogeneic fibroblasts and autologous epithelial cells are not rejected after grafting and allow for the permanent coverage of a full-thickness skin wounds. In the field of tissue engineering, these findings open the possibility of selecting a human fibroblastic or stromal cell population based on its biological properties and adequate biosafety, banking it, in order to produce "ready-to-use" bioengineered organs/tissues that could be grafted to any patient without eliciting immune reaction after grafting. Our results can be generalized to any organs produced from fibroblasts. Thus, it is a great step with multiple applications in tissue engineering and transplantation.

Examining the contribution of surrounding intact skin during cutaneous healing

Severe cutaneous wounds expose the body to the external environment, which may lead to impairments in bodily functions and increased risk of infection. There is a need to develop skin substitutes which could effectively promote complete skin regeneration following an injury. Murine models are used to test such skin substitutes, but their healing involves contraction of the dermis not found in human wounds. We have previously described a device called a dome, which comes in two models, that is used to prevent skin contraction in mice. One model provides a physical barrier to minimize contraction, and the other model has additional perforations in the barrier to allow cellular contribution from the surrounding intact skin. Taking advantage of an enhanced version of these two models, we compared granulation tissue formation, the extent of vascularization, and the transition to myofibroblastic phenotype between the models. We enhanced the dome by developing a twist open cap dome and applied the two models of the dome into the excisional wound biopsy in mice. We demonstrate that the dome can be used to prevent skin contraction in mice. The control model prevented skin contraction while barricading the contribution of surrounding intact skin. When not barricaded, the intact skin enhances wound healing by increasing the number of myofibroblasts and neovascularization. Using a novel model of inhibition of skin contraction in rodents, we examined the contribution from the surrounding intact skin to granulation tissue formation, myofibroblastic differentiation, and neovascularization during the course of skin healing in mice.

Bioglass Activated Albumin Hydrogels for Wound Healing

In this study, a novel Bioglass/albumin composite hydrogel with controllable injectability, good adhesiveness, and bioactivity, is developed by utilizing dual-functional bioactive ions released from Bioglass, which on one side controls the gelling time by creating an alkaline environment to regulate the cross-linking reaction between human serum albumin and succinimidyl succinate modified poly(ethylene glycol), and on the other side stimulates wound healing. The composite hydrogel exhibits adhesive property that is superior to clinically used fibrin and cyanoacrylate glues. The gelation time of the composite hydrogel could be regulated via changing the amounts of Bioglass which endows the hydrogel with good injectability. The in vivo experiment confirms that this composite hydrogel has good bioactivity to stimulate angiogenesis and enhance chronic wound healing. Moreover, for the first time, the concentrations of the bioactive ions released from the composite hydrogel in situ are quantified during wound healing using a microdialysis technique, and a correlation of the in vitro and in vivo concentration of ions released from the hydrogel is determined, which is extremely important for understanding the bioactivity mechanisms of Bioglass/bioceramic-based biomaterials and designing biomaterials for tissue regeneration.

Biomaterials for Skin Substitutes

Patients with extensive burns rely on the use of tissue engineered skin due to a lack of sufficient donor tissue, but it is a challenge to identify reliable and economical scaffold materials and donor cell sources for the generation of a functional skin substitute. The current review attempts to evaluate the performance of the wide range of biomaterials available for generating skin substitutes, including both natural biopolymers and synthetic polymers, in terms of tissue response and potential for use in the operating room. Natural biopolymers display an improved cell response, while synthetic polymers provide better control over chemical composition and mechanical properties. It is suggested that not one material meets all the requirements for a skin substitute. Rather, a composite scaffold fabricated from both natural and synthetic biomaterials may allow for the generation of skin substitutes that meet all clinical requirements including a tailored wound size and type, the degree of burn, the patient age, and the available preparation technique. This review aims to be a valuable directory for researchers in the field to find the optimal material or combination of materials based on their specific application.

Scar management in burn injuries using drug delivery and molecular signaling: Current treatments and future directions

In recent decades, there have been tremendous improvements in burn care that have allowed patients to survive severe burn injuries that were once fatal. However, a major limitation of burn care currently is the development of hypertrophic scars in approximately 70% of patients. This significantly decreases the quality of life for patients due to the physical and psychosocial symptoms associated with scarring. Current approaches to manage scarring include surgical techniques and non-surgical methods such as laser therapy, steroid injections, and compression therapy. These treatments are limited in their effectiveness and regularly fail to manage symptoms. As a result, the development of novel treatments that aim to improve outcomes and quality of life is imperative. Drug delivery that targets the molecular cascades of wound healing to attenuate or prevent hypertrophic scarring is a promising approach that has therapeutic potential. In this review, we discuss current treatments for scar management after burn injury, and how drug delivery targeting molecular signaling can lead to new therapeutic strategies.