Granulation tissue formation and remodeling

Elastic Nanofibrous Dressings with Mesenchymal Stem Cell-Recruiting and Protecting Characteristics for Promoting Diabetic Wound Healing

Diabetic wounds that do not heal for a long time challenge global healthcare. Mesenchymal stem cell (MSC) therapy has positive significance in promoting diabetic wound healing. However, traditional MSC therapy involves exogenous MSCs, which brings many limitations and unsatisfactory treatment. Moreover, the maintenance of MSC viability and function is difficult because of the high level of reactive oxygen species (ROS) in diabetic wounds. Therefore, we developed a nanofibrous dressing to recruit and protect endogenous MSCs while avoiding the inherent disadvantages of exogenous MSCs. Ceria nanoparticles capable of ROS scavenging are integrated into the nanofibrous dressings, together with Apt19S, a DNA aptamer with affinity and selectivity for MSCs. In addition, the homogenization and freeze-drying technology give the nanofibrous dressings good elasticity, which protects the wound from external pressure. Further experiments in diabetic mice show that the dressing has excellent endogenous MSC recruitment and anti-inflammatory properties, thereby synergistically promoting diabetic wound healing. This study is expected to explore an efficient method of stem cell therapy, providing a new way to construct high-performance wound dressings.

Degradable biomedical elastomers: paving the future of tissue repair and regenerative medicine

Degradable biomedical elastomers (DBE), characterized by controlled biodegradability, excellent biocompatibility, tailored elasticity, and favorable network design and processability, have become indispensable in tissue repair. This review critically examines the recent advances of biodegradable elastomers for tissue repair, focusing mainly on degradation mechanisms and evaluation, synthesis and crosslinking methods, microstructure design, processing techniques, and tissue repair applications. The review explores the material composition and cross-linking methods of elastomers used in tissue repair, addressing chemistry-related challenges and structural design considerations. In addition, this review focuses on the processing methods of two- and three-dimensional structures of elastomers, and systematically discusses the contribution of processing methods such as solvent casting, electrostatic spinning, and three-/four-dimensional printing of DBE. Furthermore, we describe recent advances in tissue repair using DBE, and include advances achieved in regenerating different tissues, including nerves, tendons, muscle, cardiac, and bone, highlighting their efficacy and versatility. The review concludes by discussing the current challenges in material selection, biodegradation, bioactivation, and manufacturing in tissue repair, and suggests future research directions. This concise yet comprehensive analysis aims to provide valuable insights and technical guidance for advances in DBE for tissue engineering.

Cassia Angustifolia Primed ASCs Accelerate Burn Wound Healing by Modulation of Inflammatory Response

BACKGROUND

Thermal traumas impose a huge burden on healthcare systems. This merits the need for advanced but cost-effective remedies with clinical prospects. In this context, we prepared a regenerative 3D-construct comprising of Cassia angustifolia extract (SM) primed adipose-derived stem cells (ASCs) laden amniotic membrane for faster burn wound repair.

METHODS

ASCs were preconditioned with SM (30 µg/ml for 24 h), and subsequently exposed to in-vitro thermal injury (51 °C,10 min). In-vivo thermal injury was induced by placing pre-heated copper-disc (2 cm diameter) on dorsum of the Wistar rats. ASCs (2.0 × 105) pre-treated with SM (SM-ASCs), cultured on stromal side of amniotic membrane (AM) were transplanted in rat heat-injury model. Non-transplanted heat-injured rats and non-heat-injured rats were kept as controls.

RESULTS

The significantly upregulated expression of IGF1, SDF1A, TGFβ1, VEGF, GSS, GSR, IL4, BCL2 genes and downregulation of BAX, IL6, TNFα, and NFkB1 in SM-ASCs in in-vitro and in-vivo settings confirmed its potential in promoting cell-proliferation, migration, angiogenesis, antioxidant, cell-survival, anti-inflammatory, and wound healing activity. Moreover, SM-ASCs induced early wound closure, better architecture, normal epidermal thickness, orderly-arranged collagen fibers, and well-developed skin appendages in healed rat-skin transplanted with AM+SM-ASCs, additionally confirmed by increased expression of structural genes (Krt1, Krt8, Krt19, Desmin, Vimentin, α-Sma) in comparison to untreated-ASCs laden-AM transplanted in heat injured rats.

CONCLUSION

SM priming effectively enabled ASCs to counter thermal injury by significantly enhancing cell survival and reducing inflammation upon transplantation. This study provides bases for development of effective combinational therapies (natural scaffold, medicine, and stem cells) with clinical prospects for treating burn wounds.

Research on evolution process of full-layer incision of skin tissue under different laser incidences

Considering difficulties of achieving vertical incidence of beam in different positions of skin, it is significant to study potential effects of incidence angles of laser on incisions. Surgical platform with a 1064 nm continuous fiber laser was established. Incident angle was adopted and real-time temperature fluctuations in laser operating area could be monitored. The rats were treated with laser at day 0 and day 3 after incision modeling, and H&E, Masson, Sirius Red, and Immuno-histochemical staining and enzyme-linked immunosorbent assay were adopted at day 3, 7, 14 to analyze the performance of healing. Laser with energy density of 67.54 J/mm2 can effectively accelerate wound healing in vivo, in which a laser with incident angle around 60° can effectively avoid scar hyperplasia. Therefore, the use of low energy laser with a small deflection angle has a good clinical application prospect in promoting wound healing.

Mutable Collagenous Tissue Isolated from Echinoderms Leads to the Production of a Dermal Template That Is Biocompatible and Effective for Wound Healing in Rats

The mutable collagenous tissue (MCT) of echinoderms possesses biological peculiarities that facilitate native collagen extraction and employment for biomedical applications such as regenerative purposes for the treatment of skin wounds. Strategies for skin regeneration have been developed and dermal substitutes have been used to cover the lesion to facilitate cell proliferation, although very little is known about the application of novel matrix obtained from marine collagen. From food waste we isolated eco-friendly collagen, naturally enriched with glycosaminoglycans, to produce an innovative marine-derived biomaterial assembled as a novel bi-layered skin substitute (Marine Collagen Dermal Template or MCDT). The present work carried out a preliminary experimental in vivo comparative analysis between the MCDT and Integra, one of the most widely used dermal templates for wound management, in a rat model of full-thickness skin wounds. Clinical, histological, and molecular evaluations showed that the MCDT might be a valuable tool in promoting and supporting skin wound healing: it is biocompatible, as no adverse reactions were observed, along with stimulating angiogenesis and the deposition of mature collagen. Therefore, the two dermal templates used in this study displayed similar biocompatibility and outcome with focus on full-thickness skin wounds, although a peculiar cellular behavior involving the angiogenesis process was observed for the MCDT.

Assessment of the quality of the healing process in experimentally induced skin lesions treated with autologous platelet concentrate associated or unassociated with allogeneic mesenchymal stem cells: preliminary results in a large animal model

Regenerative medicine for the treatment of skin lesions is an innovative and rapidly developing field that aims to promote wound healing and restore the skin to its original condition before injury. Over the years, different topical treatments have been evaluated to improve skin wound healing and, among them, mesenchymal stem cells (MSCs) and platelet-rich plasma (PRP) have shown promising results for this purpose. This study sought to evaluate the quality of the healing process in experimentally induced full-thickness skin lesions treated with PRP associated or unassociated with MSCs in a sheep second intention wound healing model. After having surgically created full-thickness wounds on the back of three sheep, the wound healing process was assessed by performing clinical evaluations, histopathological examinations, and molecular analysis. Treated wounds showed a reduction of inflammation and contraction along with an increased re-epithelialization rate and better maturation of the granulation tissue compared to untreated lesions. In particular, the combined treatment regulated the expression of collagen types I and III resulting in a proper resolution of the granulation tissue contrary to what was observed in untreated wounds; moreover, it led to a better maturation and organization of skin adnexa and collagen fibers in the repaired skin compared to untreated and PRP-treated wounds. Overall, both treatments improved the wound healing process compared to untreated wounds. Wounds treated with PRP and MSCs showed a healing progression that qualitatively resembles a restitutio ad integrum of the repaired skin, showing features typical of a mature healthy dermis.

Effectiveness of collagen and gatifloxacin in improving the healing and antibacterial activities of gellan gum hydrogel films as dressing materials

The demand for advanced wound care products is rapidly increasing nowadays. In this study, gellan gum/collagen (GG/C) hydrogel films containing gatifloxacin (GAT) were developed to investigate their properties as wound dressing materials. ATR-FTIR, swelling, water content, water vapor transmission rate (WVTR), and thermal properties were investigated. The mechanical properties of the materials were tested in dry and wet conditions to understand the performance of the materials after exposure to wound exudate. Drug release by Franz diffusion was measured with all samples showing 100 % cumulative drug release after 40 min. Strong antibacterial activities against Staphylococcus aureus and Staphylococcus epidermis were observed for Gram-positive bacteria, while Escherichia coli and Pseudomonas aeruginosa were observed for Gram-negative bacteria. The in-vivo cytotoxicity of GG/C-GAT was assessed by wound contraction in rats, which was 95 % for GG/C-GAT01. Hematoxylin and eosin and Masson's trichrome staining revealed the appearance of fresh full epidermis and granulation tissue, indicating that all wounds had passed through the proliferation phase. The results demonstrate the promising properties of the materials to be used as dressing materials.

An Updated Review of Hypertrophic Scarring

Hypertrophic scarring (HTS) is an aberrant form of wound healing that is associated with excessive deposition of extracellular matrix and connective tissue at the site of injury. In this review article, we provide an overview of normal (acute) wound healing phases (hemostasis, inflammation, proliferation, and remodeling). We next discuss the dysregulated and/or impaired mechanisms in wound healing phases that are associated with HTS development. We next discuss the animal models of HTS and their limitations, and review the current and emerging treatments of HTS.

Microenvironment-Based Diabetic Foot Ulcer Nanomedicine

Diabetic foot ulcers (DFU), one of the most serious complications of diabetes, are essentially chronic, nonhealing wounds caused by diabetic neuropathy, vascular disease, and bacterial infection. Given its pathogenesis, the DFU microenvironment is rather complicated and characterized by hyperglycemia, ischemia, hypoxia, hyperinflammation, and persistent infection. However, the current clinical therapies for DFU are dissatisfactory, which drives researchers to turn attention to advanced nanotechnology to address DFU therapeutic bottlenecks. In the last decade, a large number of multifunctional nanosystems based on the microenvironment of DFU have been developed with positive effects in DFU therapy, forming a novel concept of "DFU nanomedicine". However, a systematic overview of DFU nanomedicine is still unavailable in the literature. This review summarizes the microenvironmental characteristics of DFU, presents the main progress of wound healing, and summaries the state-of-the-art therapeutic strategies for DFU. Furthermore, the main challenges and future perspectives in this field are discussed and prospected, aiming to fuel and foster the development of DFU nanomedicines successfully.

The Role of the Extracellular Matrix (ECM) in Wound Healing: A Review

The extracellular matrix (ECM) is a 3-dimensional structure and an essential component in all human tissues. It is comprised of varying proteins, including collagens, elastin, and smaller quantities of structural proteins. Studies have demonstrated the ECM aids in cellular adherence, tissue anchoring, cellular signaling, and recruitment of cells. During times of integumentary injury or damage, either acute or chronic, the ECM is damaged. Through a series of overlapping events called the wound healing phases—hemostasis, inflammation, proliferation, and remodeling—the ECM is synthesized and ideally returned to its native state. This article synthesizes current and historical literature to demonstrate the involvement of the ECM in the varying phases of the wound healing cascade.

Beyond the Code: Noncoding RNAs in Skin Wound Healing

An increasing number of noncoding RNAs (ncRNAs) have been found to regulate gene expression and protein functions, playing important roles in diverse biological processes and diseases. Their crucial functions have been reported in almost every cell type and all stages of skin wound healing. Evidence of their pathogenetic roles in common wound complications, such as chronic nonhealing wounds and excessive scarring, is also accumulating. Given their unique expression and functional properties, ncRNAs are promising therapeutic and diagnostic entities. In this review, we discuss current knowledge about the functional roles of noncoding elements, such as microRNAs, long ncRNAs, and circular RNAs, in skin wound healing, focusing on in vivo evidence from studies of human wound samples and animal wound models. Finally, we provide a perspective on the outlook of ncRNA-based therapeutics in wound care.

Defining Wound Healing Progression in Cetacean Skin: Characteristics of Full-Thickness Wound Healing in Fraser's Dolphins (Lagenodelphis hosei)

Simple Summary

Cutaneous wound healing is a complex and tightly regulated biological process to restore physiological and anatomic function. Current knowledge of cutaneous wound healing is mostly based on studies in laboratory animals and humans. The histological and immunological features of skin, for example, cutaneous thickness, cellular components, and immune response, are not identical among animal species, and these differences may lead to substantial effects in cutaneous wound healing. In field observation, large cutaneous wounds in cetaceans could heal without medical treatments. However, little is known about the underlying mechanisms, and there is no histological study on full-thickness wound healing in cetaceans. The current study characterizes the macroscopic and histological features of large full-thickness wound healing in Fraser’s dolphins (Lagenodelphis hosei). The differences of wound healing between cetaceans and terrestrial mammals were shown from the histological aspect, including rete and dermal ridge appearance, repigmentation, and adipose tissue regeneration. Better understanding of the mechanism of full-thickness wound healing in cetaceans will shed light on veterinary and human regenerative medicine, leading to novel therapies.

Abstract

Cetaceans are tight-skinned mammals that exhibit an extraordinary capacity to heal deep soft tissue injuries. However, essential information of large full-thickness wound healing in cetaceans is still lacking. Here, the stages of full-thickness wound healing were characterized in Fraser’s dolphins (Lagenodelphis hosei). The skin samples were collected from normal skin and full-thickness cookiecutter shark (Isistius brasiliensis)-bite wounds of stranded carcasses. We defined five stages of wound healing according to macroscopic and histopathological examinations. Wounds in Stage 1 and 2 were characterized by intercellular and intracellular edema in the epidermal cells near the wound edge, mixed inflammatory cell infiltration, and degradation of collagen fibers. In Stage 3 wounds, melanocytes, melanin granules, rete and dermal ridges were noticed in the neo-epidermis, and the adipose tissue in adjacent blubber was replaced by cells and fibers. Wounds in Stage 4 and 5 were characterized by gradual restoration of the normal skin architecture including rete and dermal ridges, collagen bundles, and adipose tissue. These phenomena were quite different from previous studies in terrestrial tight-skinned mammals, and therefore, further in-depth research into the mechanisms of dolphin wound healing would be needed to gain new insights into veterinary and human regenerative medicine.

Human amniotic epithelial cell transplantation improves scar remodeling in a rabbit model of acute vocal fold injury: a pilot study

Objective

To gain insight into the molecular mechanisms underlying the early stages of vocal fold extracellular matrix (ECM) remodeling after a mid-membranous injury resulting from the use of human amniotic epithelial cells (hAEC), as a novel regenerative medicine cell-based therapy.

Methods

Vocal folds of six female, New Zealand White rabbits were bilaterally injured. Three rabbits had immediate bilateral direct injection of 1 × 10⁶ hAEC in 100 µl of saline solution (hAEC) and three with 100 µl of saline solution (controls, CTR). Rabbits were euthanized 6 weeks after injury. Proteomic analyses (in-gel trypsin protein digestion, LC–MS/MS, protein identification using Proteome Discoverer and the Uniprot Oryctolagus cuniculus (Rabbit) proteome) and histological analyses were performed.

Results

hAEC treatment significantly increased the expression of ECM proteins, elastin microfibril interface-located protein 1 (EMILIN-1) and myocilin that are primarily involved in elastogenesis of blood vessels and granulation tissue. A reactome pathway analysis showed increased activity of the anchoring fibril formation by collagen I and laminin, providing mechanical stability and activation of cell signaling pathways regulating cell function. hAEC increased the abundance of keratin 1 indicating accelerated induction of the differentiation programming of the basal epithelial cells and, thereby, improved barrier function. Lastly, upregulation of Rab GDP dissociation inhibitor indicates that hAEC activate the vesicle endocytic and exocytic pathways, supporting the exosome-mediated activation of cell–matrix and cell-to-cell interactions.

Conclusions

This pilot study suggests that injection of hAEC into an injured rabbit vocal fold favorably alters ECM composition creating a microenvironment that accelerates differentiation of regenerated epithelium and promotes stabilization of new blood vessels indicative of accelerated and improved repair.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-02701-w.

Effects of the Washing Time and Washing Solution on the Biocompatibility and Mechanical Properties of 3D Printed Dental Resin Materials

Three-dimensional (3D) printing technology is highly regarded in the field of dentistry. Three-dimensional printed resin restorations must undergo a washing process to remove residual resin on the surface after they have been manufactured. However, the effect of the use of different washing solutions and washing times on the biocompatibility of the resulting resin restorations is unclear. Therefore, we prepared 3D-printed denture teeth and crown and bridge resin, and then washed them with two washing solutions (isopropyl alcohol and tripropylene glycol monomethyl ether) using different time points (3, 5, 10, 15, 30, 60, and 90 min). After this, the cell viability, cytotoxicity, and status of human gingival fibroblasts were evaluated using confocal laser scanning. We also analyzed the flexural strength, flexural modulus, and surface SEM imaging. Increasing the washing time increased the cell viability and decreased the cytotoxicity (p < 0.001). Confocal laser scanning showed distinct differences in the morphology and number of fibroblasts. Increasing the washing time did not significantly affect the flexural strength and surface, but the flexural modulus of the 90 min washing group was 1.01 ± 0.21 GPa (mean ± standard deviation), which was lower than that of all the other groups and decreased as the washing time increased. This study confirmed that the washing time affected the biocompatibility and mechanical properties of 3D printed dental resins.

The current and advanced therapeutic modalities for wound healing management

Ever-increasing demands on improving efficiencies of wound healing procedures are a strong driving force for the development of replacement approaches. This review focuses on wound healing management from the point of formation to the point of healing procedures. The most important usual healing modality with key characteristic is explained and their limitations are discussed. Novel interesting approaches are presented with a concentration of the unique features and action mechanisms. Special attention is paid to gas plasma and nanotechnology impact on wound healing management from fundamental processes to beneficial outcomes. Challenges and opportunities for the future trend that combined common protocols and emerging technologies are discussed.

Histological Evidence of Wound Healing Improvement in Rats Treated with Oral Administration of Hydroalcoholic Extract of Vitis labrusca

Plant extracts rich in phenolic compounds have been demonstrated to accelerate wound healing, but their use by oral route has been poorly studied. The leaves of Vitis labrusca are rich in phenolic acids and flavonoids. The goal of this study was to assess the healing properties of the oral administration of hydroalcoholic extract of V. labrusca leaves (HEVL) in a murine model. HEVL was obtained by Soxhlet and dynamic maceration, and their yield and phenolic acids and flavonoid contents were determined. For the wound healing assay, 8 mm wounds were performed on the back of 48 Wistar rats, assigned into four groups (n = 12): CTR (distilled water), HEVL100, HEVL200, and HEVL300 (HEVL at 100, 200, and 300 mg/kg, respectively). On days 7 and 14, wound closure rates were assessed, and the healing wounds were subjected to histological analysis. Soxhlet-obtained extract was selected for the wound healing assay because it provided a higher yield and phenolic acid and flavonoid contents. HEVL significantly reduced leukocytosis in the peripheral blood (p < 0.05), accelerated wound closure (p < 0.05), and improved collagenization (p < 0.05) on day 7, as well as enhanced the epidermal tissue thickness (p < 0.001) and elastic fiber deposition on day 14 (p < 0.01). Furthermore, HEVL promoted an increase in the histological grading of wound healing on both days 7 and 14 (p < 0.01). The doses of 200 and 300 mg/kg provided better results than 100 mg/Kg. Our data provide histological evidence that the oral administration of HEVL improves wound healing in rodents. Therefore, the extract can be a potential oral medicine for healing purposes.

A Prototype Skin Substitute, Made of Recycled Marine Collagen, Improves the Skin Regeneration of Sheep

Simple Summary

Marine ecosystems are a huge source of unexplored “blue” materials for different applications. The edible part of sea urchin is limited, and the vast majority of the product ends up as waste. Our studies intend to fully recycle wastes from the food industry and reconvert them in high added-value products, as innovative biocompatible skin substitutes for tissue regeneration. The aim of the present work is to apply the pioneering skin substitute in in vivo experimental wounds to test its regenerative potential and compare it, in a future study, to the available commercial membranes produced with collagen of bovine, porcine, and equine origin. Results are encouraging since the skin substitute made with marine collagen reduced inflammation, promoted the deposition of granulation tissue, and enhanced a proper re-epithelialization with the adequate development of skin appendages. In summary, our findings might be of great interest for processing industries and biotech companies which transform waste materials in high-valuable and innovative products for Veterinary advanced applications.

Abstract

Skin wound healing is a complex and dynamic process that aims to restore lesioned tissues. Collagen-based skin substitutes are a promising treatment to promote wound healing by mimicking the native skin structure. Recently, collagen from marine organisms has gained interest as a source for producing biomaterials for skin regenerative strategies. This preliminary study aimed to describe the application of a collagen-based skin-like scaffold (CBSS), manufactured with collagen extracted from sea urchin food waste, to treat experimental skin wounds in a large animal. The wound-healing process was assessed over different time points by the means of clinical, histopathological, and molecular analysis. The CBSS treatment improved wound re-epithelialization along with cell proliferation, gene expression of growth factors (VEGF-A), and development of skin adnexa throughout the healing process. Furthermore, it regulated the gene expression of collagen type I and III, thus enhancing the maturation of the granulation tissue into a mature dermis without any signs of scarring as observed in untreated wounds. The observed results (reduced inflammation, better re-epithelialization, proper development of mature dermis and skin adnexa) suggest that sea urchin-derived CBSS is a promising biomaterial for skin wound healing in a “blue biotechnologies” perspective for animals of Veterinary interest.

Could cold plasma act synergistically with allogeneic mesenchymal stem cells to improve wound skin regeneration in a large size animal model?

Skin wound healing may sometimes lead to open sores that persist for long periods and expensive hospitalization is needed. Among different kinds of therapeutic innovative approaches, mesenchymal stem cells (MSCs) and low-temperature atmospheric pressure cold plasma (ionized gas) have been recently tested to improve this regenerative process. To optimize wound healing the present study intended to combine, for the first time, these two novel approaches in a large size animal wound healing model with the aim of assessing the putative dual beneficial effects. Based on clinical, histopathological, and molecular results a synergistic action in a second intention healing wound in sheep has been observed. Experimental wounds treated with cold plasma and MSCs showed a slower but more effective healing compared to the single treatment, as observed in previous studies. The combined treatment improved the correct development of skin appendages and structural proteins of the dermis showing the potential of the dual combination as a safe and effective tool for skin regeneration in the veterinary clinical field.

Third-degree burn mouse treatment using recombinant human fibroblast growth factor 2

Fibroblast growth factor 2 (FGF-2) is a multifunctional protein that has major roles in wound healing, tissue repair, and regeneration. This therapeutic protein is widely used for burn treatment because it can stimulate cell proliferation and differentiation, angiogenesis, and extracellular matrix remodeling. In this study, we developed a simple method using a controlled heated brass rod to create a homogenous third-degree burn murine model and evaluated the treatment using recombinant human FGF-2 (rhFGF-2). The results indicated that the wound area was 0.83 ± 0.05 cm² and wound depth was 573.42 ± 147.82 μm. Mice treated with rhFGF-2 showed higher rates of wound closure, granulation tissue formation, angiogenesis, and re-epithelialization than that of phosphate-buffered saline (PBS)-treated group. In conclusion, our lab-made rhFGF-2 could be a potentially therapeutic protein for burn treatment as well as a bioequivalent drug for other commercial applications using FGF-2.

Cellulose/Collagen Dressings for Diabetic Foot Ulcer: A Review

Diabetic foot ulcer (DFU) is currently a global concern and it requires urgent attention, as the cost allocation by the government for DFU increases every year. This review was performed to provide scientific evidence on the advanced biomaterials that can be utilised as a first-line treatment for DFU patients. Cellulose/collagen dressings have a biological property on non-healing wounds, such as DFU. This review aims to analyse scientific-based evidence of cellulose/collagen dressing for DFU. It has been proven that the healing rate of cellulose/collagen dressing for DFU patients demonstrated a significant improvement in wound closure as compared to current standard or conventional dressings. It has been scientifically proven that cellulose/collagen dressing provides a positive effect on non-healing DFU. There is a high tendency for cellulose/collagen dressing to be used, as it highly promotes angiogenesis with a rapid re-epithelisation rate that has been proven effective in clinical trials.

Distinct differences in hypoxic responses between human oral mucosa and skin fibroblasts in a 3D collagen matrix

The differences between oral mucosa and skin wound healing involving hypoxic responses of fibroblasts are poorly elucidated. In this study, we aimed to study the different hypoxic responses between oral and skin fibroblasts embedded in a three-dimensional (3D) collagen matrix to address the early stage of wound healing. Primary oral mucosa fibroblasts (OMFs) obtained from the retromolar area and skin fibroblasts (SFs) obtained from the abdomen were cultured in the 3D 'floating model' under either 21%, 5% or 1% O₂ for 2 days. Cell viability under hypoxia was higher in the OMFs than in the SFs. Collagen gel contraction was suppressed under hypoxic conditions in both fibroblasts, consistent with the reduction of alpha smooth muscle actin expression, except for SFs under 1% O₂. Subsequently, their gene expression profiles between 21 and 1% O₂ concentrations were compared via microarray technology, and the expression profiles of the extracellular matrix (ECM)-associated proteins, including matrix metalloproteinases and collagens, were evaluated. The OMFs were more susceptible to 1% O₂, and more of their genes were downregulated than the SFs'. Although the production and expression levels of ECM-associated proteins in both fibroblasts diminished under hypoxia, those levels in OMFs were significantly higher than those in SFs. In the case of single origin OMFs and SFs, our findings suggest that OMFs possess a higher baseline production capacity of several ECM-associated proteins than SFs, except type III collagen. The intrinsic hypoxic responses of OMFs may be attributed to a more favourable wound healing in oral mucosa.

Depletion of langerin+ cells enhances cutaneous wound healing

Langerin is a C-type lectin receptor that is expressed on Langerhans cells and langerin-positive dermal dendritic cells in the skin. Little is known about the function of langerin⁺ cells in wound healing. In this study, the effects of ablation of langerin⁺ cells on healing of a full-thickness excision wound were investigated using the langerin-DTR depletable mouse. Strikingly, depletion of langerin⁺ cells resulted in more rapid reduction in wound area. Accelerated wound healing in the langerin⁺ -cell-depleted group was characterized by enhanced neo-epidermis and granulation tissue formation, and increased cellular proliferation within the newly formed tissues. Accelerated healing in the absence of langerin⁺ cells was associated with increased levels of granulocyte-macrophage colony-stimulating factor, F4/80⁺ cells and blood vessels within the granulation tissue. These data support an inhibitory role for langerin⁺ cells during wound healing. Therapies that suppress langerin⁺ cells or their function may therefore have utility in progressing the healing of wounds in humans.

The link between advanced glycation end products and apoptosis in delayed wound healing

Advanced glycation end products (AGEs) are naturally occurring molecules that start to accumulate from embryonic developmental stages and form as part of normal ageing. When reducing sugars interact with and modify proteins or lipids, AGE production occurs. AGE formation accelerates in chronic hyperglycemic conditions, and high AGE levels have been associated with the pathogenesis of various diseases. In addition, enhanced levels of AGEs have been linked to delayed wound healing as seen in patients with diabetes mellitus. Research has provided numerous ways in which a high AGE concentration results in impaired wound healing, including oxidative stress, structural and functional changes to proteins important in wound repair, an enhanced inflammatory response by activation of transcription factors, and possible exaggerated apoptosis of cells necessary to the wound repair process. Apoptosis is a naturally occurring cell death process that is significant for normal tissue functioning and plays an important role in wound repair by preventing a prolonged inflammatory response and excessive scar formation. Abnormal apoptosis affects wound healing, resulting in slow healing wounds. This review will summarize the role of AGEs in wound healing, focusing on the mechanisms by which AGEs lead to apoptosis in various cell types. The review provides the way forward for medical research and molecular studies as it focuses on the mechanisms by which AGEs induce apoptosis in various cell types, including fibroblasts, osteoblasts, neuronal cells, and endothelial cells. Reviewing the mechanisms of AGE-linked apoptosis is important in understanding the impact of high AGE levels in delayed wound healing in diabetic patients due to abnormal apoptosis of cells necessary to the wound healing process.

Effects of Myeloperoxidase on Methicillin-Resistant Staphylococcus aureus-Colonized Burn Wounds in Rats

Objective: To achieve better therapeutic results in burn wound infections and to examine alternatives to antibiotics, we designed this study to elaborate the role of myeloperoxidase (MPO) on infected burn wounds in rats. Approach: We compared chemical properties as well as bacteriostatic ability of MPO in different concentrations with NeutroPhase. Subsequently, we applied MPO (MPO group), NeutroPhase (NeutroPhase group), NaCl+H₂O₂ (NaCl+H₂O₂ group), or NaCl (control group) on rat dorsal burn wounds inoculated with methicillin-resistant Staphylococcus aureus (MRSA). Their effects on MRSA-colonized wounds were evaluated by microscopy, histologic section, and Western blot. Results: MPO produced more H⁺ and HClO^-, leading to a more acidic environment. Moreover, MPO inhibited the growth of MRSA more intensely after 6 h of inoculation ex vivo. In vivo the open wound rate in the MPO group was significantly lower, while the contraction rate and epithelialization rate of MPO group were higher than that of the control group, NaCl+H₂O₂ group, and NeutroPhase group on day 20. The hematoxylin and eosin staining of MPO group showed better wound healing than other groups. More vascular endothelial growth factor (VEGF) was expressed in wound tissue of MPO group by Western blot. Innovation: This is the first study to use MPO for MRSA-colonized burn wound therapy. Conclusion: MPO displayed more effective bacteriostatic ability, possibly beneficial for MRSA-colonized wound healing.

A roadmap for promoting endogenous in situ tissue restoration using inductive bioscaffolds after acute brain injury

The regeneration of brain tissue remains one of the greatest unsolved challenges in medicine and by many is considered unfeasible. Indeed, the adult mammalian brain does not regenerate tissue, but there is ongoing endogenous neurogenesis, which is upregulated after injury and contributes to tissue repair. This endogenous repair response is a conditio sine que non for tissue regeneration. However, scarring around the lesion core and cavitation provide unfavorable conditions for tissue regeneration in the brain. Based on the success of using extracellular matrix (ECM)-based bioscaffolds in peripheral soft tissue regeneration, it is plausible that the provision of an inductive ECM-based hydrogel inside the volumetric tissue loss can attract neural cells and create a de novo viable tissue. Following perturbation theory of these successes in peripheral tissues, we here propose 9 perturbation parts (i.e. requirements) that can be solved independently to create an integrated series to build a functional and integrated de novo neural tissue. Necessities for tissue formation, anatomical and functional connectivity are further discussed to provide a new substrate to support the improvement of behavioral impairments after acute brain injury. We also consider potential parallel developments of this tissue engineering effort that can support therapeutic benefits in the absence of de novo tissue formation (e.g. structural support to veterate brain tissue). It is envisaged that eventually top-down inductive "natural" bioscaffolds composed of decellularized tissues (i.e. ECM) will be replaced by bottom-up synthetic designer hydrogels that will provide very defined structural and signaling properties, potentially even opening up opportunities we currently do not envisage using natural materials.

Improvement of diabetic wound healing by topical application of Vicenin-2 hydrocolloid film on Sprague Dawley rats

Background

Impaired wound healing is a debilitating complication of diabetes that leads to significant morbidity, particularly foot ulcers. The risk of developing diabetic foot ulcers for diabetic patients is 15% over their lifetime and approximately 85% of limb amputations is caused by non–healing ulcers. Unhealed, gangrenous wounds destroy the structural integrity of the skin, which acts as a protective barrier that prevents the invasion of external noxious agents into the body. Vicenin-2 (VCN-2) has been reported to contain prospective anti-oxidant and anti-inflammatory properties that enhance cell proliferation and migration. Sodium Alginate (SA) is a natural polysaccharide that possesses gel forming properties and has biodegradable and biocompatible characteristics. Therefore, the objective of this study is to evaluate the effect of SA wound dressings containing VCN-2 on diabetic wounds.

Methods

Wounds were inflicted in type-1 diabetic-streptozotocin (STZ) induced male Sprague Dawley rats. Subsequently, relevant groups were topically treated with the indicated concentrations (12.5, 25 and 50 μM) of VCN-2 hydrocolloid film over the study duration (14 days). The control group was treated with vehicle dressing (blank or allantoin). Wounded tissues and blood serum were collected on 0, 7 and 14 days prior to sacrifice. Appropriate wound assessments such as histological tests, nitric oxide assays, enzyme-linked immunosorbent assays (ELISA) and immunoblotting assays were conducted to confirm wound healing efficacy in the in vivo model. One-way Analysis of Variance (ANOVA) was used for statistical analysis.

Results

Results showed that hydrocolloid film was recapitulated with VCN-2 enhanced diabetic wound healing in a dose-dependent manner. VCN-2 reduced pro-inflammatory cytokines (IL-1β, IL-6 and TNF-α), mediators (iNOS and COX-2), and nitric oxide (NO) via the NF-κB pathway. Data suggests that the VCN-2 film facilitated healing in hyperglycemic conditions by releasing growth factors such as (VEGF and TGF-β) to enhance cell proliferation, migration, and wound contraction via the VEGF and TGF-β mechanism pathways.

Conclusions

This study’s findings suggest that VCN-2 may possess wound healing potential since topical treatment with VCN-2 hydrocolloid films effectively enhanced wound healing in hyperglycemic conditions.

In Vivo Cell Tracking, Reactive Oxygen Species Scavenging, and Antioxidative Gene Down Regulation by Long-Term Exposure of Biomass-Derived Carbon Dots

Biomass derived carbon dots (CD) have been observed to be excellent bioimaging probes due to their nontoxic, stable fluorescence, lesser bleachability, and excellent bioconjugation properties. In the current study, green chili extract derived CD synthesis via microwave irradiation is reported. The time dependent top down degradation of carbonaceous materials to CD are monitored via electron microscopy and correlated with fluorescence intensity. Further, the CD were explored for long-term cell tracking and cell therapy monitoring in a rodent model to study wound healing kinetics. The cells were monitorable up to 21 days (until the entire wound healed). CD were observed to scavenge reactive oxygen species (ROS) in vitro and in vivo and provided control over ROS scavenging enzyme gene expressions via down regulation. Further, it was observed to remodel the wound healing kinetics via altering granulation tissue distribution and formation of microvessels to establish the capability of CD to enhance wound healing.

Alveolar blood clots and platelet-rich fibrin induce in vitro fibroblast proliferation and migration

Wound healing process comprises a complex network of cells and molecules that are regulated in order to pursue tissue regeneration. Our study focused on the capacity of alveolar blood clots (ABCs), platelet-rich fibrin (PRF) and plasma rich in growth factors (PRGF) to induce in vitro fibroblasts proliferation and migration as a measure of alveolar regeneration. Using cellular impedance with xCELLigence technology we quantified the proliferation and the migration capacity of L929 fibroblast standard cell line in the presence of 4 different ABCs and 3 different PRFs harvested from healthy individuals during standard tooth extraction. We obtained a clear cellular proliferation induced by the compounds mainly after 24 h of cultivation, in a dose-dependent manner. After 48 h of cultivation we registered activated proliferation, but slightly decreased compared to the 24 h profile. Our data confirm that the presence of the blood clot is involved in the regenerative processes. The migratory capacity of fibroblasts was statistically activated by the PL compounds while not affected by the tested PRFs. The chemical mediators present within the blood clot, either produced by inflammatory cells captive within, or by endothelial or mesenchymal cells induced fibroblastic proliferation and subsequent collagen deposition.

Biodegradation of ECM hydrogel promotes endogenous brain tissue restoration in a rat model of stroke

The brain is considered to have a limited capacity to repair damaged tissue and no regenerative capacity following injury. Tissue lost after a stroke is therefore not spontaneously replaced. Extracellular matrix (ECM)-based hydrogels implanted into the stroke cavity can attract endogenous cells. These hydrogels can be formulated at different protein concentrations that govern their rheological and inductive properties. We evaluated histologically 0, 3, 4 and 8 mg/mL of porcine-derived urinary bladder matrix (UBM)-ECM hydrogel concentrations implanted in a 14-day old stroke cavity. Less concentrated hydrogels (3 and 4 mg/mL) were efficiently degraded with a 95% decrease in volume by 90 days, whereas only 32% of the more concentrated and stiffer hydrogel (8 mg/mL) was resorbed. Macrophage infiltration and density within the bioscaffold progressively increased in the less concentrated hydrogels and decreased in the 8 mg/mL hydrogels. The less concentrated hydrogels showed a robust invasion of endothelial cells with neovascularization. No neovascularization occurred with the stiffer hydrogel. Invasion of neural cells increased with time in all hydrogel concentrations. Differentiation of neural progenitors into mature neurons with axonal projections was evident, as well as a robust invasion of oligodendrocytes. However, relatively few astrocytes were present in the ECM hydrogel, although some were present in the newly forming tissue between degrading scaffold patches. Implantation of an ECM hydrogel partially induced neural tissue restoration, but a more complete understanding is required to evaluate its potential therapeutic application. STATEMENT OF SIGNIFICANCE: Extracellular matrix hydrogel promotes tissue regeneration in many peripheral soft tissues. However, the brain has generally been considered to lack the potential for tissue regeneration. We here demonstrate that tissue regeneration in the brain can be achieved using implantation of ECM hydrogel into a tissue cavity. A structure-function relationship is key to promote tissue regeneration in the brain. Specifically, weaker hydrogels that were retained in the cavity underwent an efficient biodegradation within 14 days post-implantation to promote a tissue restoration within the lesion cavity. In contrast, stiffer ECM hydrogel only underwent minor biodegradation and did not lead to a tissue restoration. Inductive hydrogels weaker than brain tissue provide the appropriate condition to promote an endogenous regenerative response that restores tissue in a cavity. This approach offers new avenues for the future treatment of chronic tissue damage caused by stroke and other acute brain injuries.

Elevated CD26 Expression by Skin Fibroblasts Distinguishes a Profibrotic Phenotype Involved in Scar Formation Compared to Gingival Fibroblasts

Compared to skin, wound healing in oral mucosa is faster and produces less scarring, but the mechanisms involved are incompletely understood. Studies in mice have linked high expression of CD26 to a profibrotic fibroblast phenotype, but this has not been tested in models more relevant for humans. We hypothesized that CD26 is highly expressed by human skin fibroblasts (SFBLs), and this associates with a profibrotic phenotype distinct from gingival fibroblasts (GFBLs). We compared CD26 expression in human gingiva and skin and in gingival and hypertrophic-like scar-forming skin wound healing in a pig model, and used three-dimensional cultures of human GFBLs and SFBLs. In both humans and pigs, nonwounded skin contained abundantly CD26-positive fibroblasts, whereas in gingiva they were rare. During skin wound healing, CD26-positive cells accumulated over time and persisted in forming hypertrophic-like scars, whereas few CD26-positive cells were present in the regenerated gingival wounds. Cultured human SFBLs displayed significantly higher levels of CD26 than GFBLs. This was associated with an increased expression of profibrotic genes and transforming growth factor-β signaling in SFBLs. The profibrotic phenotype of SFBLs partially depended on expression of CD26, but was independent of its catalytic activity. Thus, a CD26-positive fibroblast population that is abundant in human skin but not in gingiva may drive the profibrotic response leading to excessive scarring.

TGF-β1 Pretreatment Improves the Function of Mesenchymal Stem Cells in the Wound Bed

The wound healing process initiates after injury to a tissue and involves a series of orchestrated events to minimize the invasion of foreign matters such as bacteria and efficiently regenerate the damaged tissue. A variety of cells must be recruited to the tissue during wound healing. However, this process is severely disrupted in patients suffering from chronic illness, including diabetes, leading to impaired healing or non-healing wounds. Current avenues of treatment include negative-pressure therapy, wound debridement, growth factor replacement, and cell-based therapies. Among these therapies, mesenchymal stem cells (MSCs) delivery to the wound holds a very high promise due to the innate abilities of MSCs that include immunogenicity, plasticity, and self-renewal. Bone marrow derived MSCs have been shown to promote more rapid wound healing by increased cytokine production in diabetic mice. However, the lack of understanding of the mechanical and chemical interaction of the transplanted MSCs with the factors present in the regenerative niches limits their efficacy in the wound bed. In this study, we sought to understand how the changes in MSC biochemical and biophysical properties can affect their function in vitro and in vivo. We demonstrate that pretreatment of MSCs with the mechano-stimulatory soluble factor transforming growth factor (TGF-β1), which is highly expressed in injury sites, improves wound closure in a syngeneic murine wound model. This improved wound closure correlated with increased invasion into the wound bed. In vitro studies demonstrated that TGF-β1 pretreatment expedited wound closure by increasing adhesion, traction force, and migration even after removal of the stimulus. Furthermore, this response was mediated by the cytoskeletal protein focal adhesion kinase. Taken together, this study suggests that defined chemical stimuli can benefit site specific adaptability of MSCs to improve their function and therapeutic usefulness.

Nontraditional Methods to Evaluate Wound Healing

BACKGROUND

Traditional evaluation of wound healing is sometimes subjective. It is necessary to develop qualitative and quantitative methods to enable more efficient and accurate evaluation of wounds. Recently, new techniques have been introduced and the correspondence between these techniques and clinician judgment is critical.

OBJECTIVE

Some nontraditional techniques that analyze wound healing were reviewed, which include measurements of the wound area, tissue color, skin barrier function, skin humidity, and keratinocyte morphology.

METHODS

This review article is based on medical research that focuses on the evaluation of wound healing.

RESULTS

Software-based and advanced device-based techniques generally provide more accurate and precise results than traditional ones, such as the ruler-based technique. Measurement of tissue color can also help to identify the type of tissue. Evaluation of skin barrier function can assist clinicians to analyze functional restoration of skin, whereas skin humidity demonstrates the exudate production status of the wound. In addition, keratinocyte morphology in the wound bed indicates quality of wound healing and side effects of treatment.

CONCLUSION

There is no gold standard method for qualitative and quantitative evaluation of wound healing. It is important to understand the type of wound, sample size, results obtained, advantages, and limitations of each technique.

Bioinspired Materials and Biocompatibility

Material science and engineering are the sources of divergent emerging technologies, since all the modifications and developments are being made to reach a novel biomaterial to fulfill the requirements of biomedical applications, the first important feature is the biocompatibility of the new advanced material. In this chapter, the general biocompatibility concept, test systems to determine biocompatibility, examples of bioinspired materials and their altered biocompatibility and future expectations from these novel bioinspired materials will be discussed.

Integrins in Wound Healing

Significance: Regulation of cell adhesions during tissue repair is fundamentally important for cell migration, proliferation, and protein production. All cells interact with extracellular matrix proteins with cell surface integrin receptors that convey signals from the environment into the nucleus, regulating gene expression and cell behavior. Integrins also interact with a variety of other proteins, such as growth factors, their receptors, and proteolytic enzymes. Re-epithelialization and granulation tissue formation are crucially dependent on the temporospatial function of multiple integrins. This review explains how integrins function in wound repair. Recent Advances: Certain integrins can activate latent transforming growth factor beta-1 (TGF-β1) that modulates wound inflammation and granulation tissue formation. Dysregulation of TGF-β1 function is associated with scarring and fibrotic disorders. Therefore, these integrins represent targets for therapeutic intervention in fibrosis. Critical Issues: Integrins have multifaceted functions and extensive crosstalk with other cell surface receptors and molecules. Moreover, in aberrant healing, integrins may assume different functions, further increasing the complexity of their functionality. Discovering and understanding the role that integrins play in wound healing provides an opportunity to identify the mechanisms for medical conditions, such as excessive scarring, chronic wounds, and even cancer. Future Directions: Integrin functions in acute and chronic wounds should be further addressed in models better mimicking human wounds. Application of any products in acute or chronic wounds will potentially alter integrin functions that need to be carefully considered in the design.

Distinct phenotype and therapeutic potential of gingival fibroblasts

Gingiva of the oral mucosa provides a practical source to isolate fibroblasts for therapeutic purposes because the tissue is easily accessible, tissue discards are common during routine clinical procedures and wound healing after biopsy is fast and results in complete wound regeneration with very little morbidity or scarring. In addition, gingival fibroblasts have unique traits, including neural crest origin, distinct gene expression and synthetic properties and potent immunomodulatory functions. These characteristics may provide advantages for certain therapeutic approaches over other more commonly used cells, including skin fibroblasts, both in intraoral and extra-oral sites. However, identity and phenotype of gingival fibroblasts, like other fibroblasts, are still not completely understood. Gingival fibroblasts are phenotypically heterogeneous, and these…fibroblast subpopulations may play different roles in tissue maintenance, regeneration and pathologies. The purpose of this review is to summarize what is currently known about gingival fibroblasts, their distinct potential for tissue regeneration and their potential therapeutic uses in the future.

Integrins in periodontal disease

Cell surface integrin receptors mediate cell adhesion, migration and cellular signaling in all nucleated cells. They are activated by binding to extracellular ligands or by intracellular proteins, such as kindlins that engage with their cytoplasmic tails. Cells in the periodontal tissues express several integrins with overlapping ligand-binding capabilities. A distinct phenotype in the periodontium has only been described for knockouts or mutations of three integrin subunits, α11, β6 and β2. Integrin α11β1 appears to have some regulatory function in the periodontal ligament of continuously erupting incisors in mice. Integrin αvβ6 is expressed in the junctional epithelium (JE) of the gingiva. Animals deficient in this receptor develop classical signs of periodontal disease, including inflammation, apical migration of the JE and bone loss, suggesting that it plays a role in the regulation of periodontal inflmmation, likely through activation of transforming growth factor-β1. Lack of integrin activation in the JE is also associated with periodontitis. Patients with kindlin-1 mutations have severe early-onset periodontal disease. Finally, patients with mutations in the leukocyte-specific β2 integrin subunit have severe periodontal problems due to lack of transiting neutrophils in the periodontal tissues.

Human gingival fibroblasts display a non-fibrotic phenotype distinct from skin fibroblasts in three-dimensional cultures

Scar formation following skin injury can be a major psychosocial and physiological problem. However, the mechanisms of scar formation are still not completely understood. Previous studies have shown that wound healing in oral mucosa is faster, associates with a reduced inflammatory response and results to significantly reduced scar formation compared with skin wounds. In the present study, we hypothesized that oral mucosal fibroblasts from human gingiva are inherently distinct from fibroblasts from breast and abdominal skin, two areas prone to excessive scar formation, which may contribute to the preferential wound healing outcome in gingiva. To this end, we compared the phenotype of human gingival and skin fibroblasts cultured in in vivo-like three-dimensional (3D) cultures that mimic the cells' natural extracellular matrix (ECM) niche. To establish 3D cultures, five parallel fibroblast lines from human gingiva (GFBLs) and breast skin (SFBLs) were seeded in high density, and cultured for up to 21 days in serum and ascorbic acid containing medium to induce expression of wound-healing transcriptome and ECM deposition. Cell proliferation, morphology, phenotype and expression of wound healing and scar related genes were analyzed by real-time RT-PCR, Western blotting and immunocytochemical methods. The expression of a set of genes was also studied in three parallel lines of human abdominal SFBLs. Findings showed that GFBLs displayed morphologically distinct organization of the 3D cultures and proliferated faster than SFBLs. GFBLs expressed elevated levels of molecules involved in regulation of inflammation and ECM remodeling (MMPs) while SFBLs showed significantly higher expression of TGF-β signaling, ECM and myofibroblast and cell contractility-related genes. Thus, GFBLs display an inherent phenotype conducive for fast resolution of inflammation and ECM remodeling, characteristic for scar-free wound healing, while SFBLs have a profibrotic, scar-prone phenotype.