Involvement of notch signaling in wound healing

Mesenchymal stem cells and their exosomes: a novel approach to skin regeneration via signaling pathways activation

Accelerating wound healing is a crucial objective in surgical and regenerative medicine. The wound healing process involves three key stages: inflammation, cell proliferation, and tissue repair. Mesenchymal stem cells (MSCs) have demonstrated significant therapeutic potential in promoting tissue regeneration, particularly by enhancing epidermal cell migration and proliferation. However, the precise molecular mechanisms underlying MSC-mediated wound healing remain unclear. This review highlights the pivotal role of MSCs and their exosomes in wound repair, with a specific focus on critical signaling pathways, including PI3K/Akt, WNT/β-catenin, Notch, and MAPK. These pathways regulate essential cellular processes such as proliferation, differentiation, and angiogenesis. Moreover, in vitro and in vivo studies reveal that MSCs accelerate wound closure, enhance collagen deposition, and modulate immune responses, contributing to improved tissue regeneration. Understanding these mechanisms provides valuable insights into MSC-based therapeutic strategies for enhancing wound healing.

Investigation on the effects and mechanisms of novel peptide nanofiber gel to promote wound healing of deep second-degree burns in mice

The self-assembled peptide RADA16-I (RADARADARADARADA) has been widely used in biomaterials. However, studies on the practical application of self-assembled peptide hydrogels loaded with bioactive peptides are still insufficient. In this study, we successfully prepared the peptide nanofiber gel RGJ by incorporating the bioactive peptides A8SGLP-1 (G) and Jagged-1 (J) into RADA16-I (R) in specific ratios. The mechanical properties, secondary structure, and microstructure of RGJ were thoroughly characterized using a rheometer, circular dichroism (CD), and transmission electron microscopy (TEM). The results showed that R and RGJ adopted stable β-folded structures at room temperature, and RGJ exhibited a nanofiber mesh structure, confirming its excellent physical properties. Cellular experiments demonstrated that RGJ significantly enhanced the proliferation and migration of HaCaT, L929, and HUVEC cells, with the most pronounced effect observed in HUVEC cells. In the 100 μg/mL RGJ-treated group, cell viability (OD value) reached 1.369, which was significantly higher than that of the control group (0.673) and the R-only group (0.848). The strongest pro-migratory effect was observed in HaCaT cells, with a scratch closure rate of 22.83 %. In vivo experiments showed that the deep second-degree burn wounds of mice in the RGJ gel-treated group healed rapidly by day 17, exhibiting 99.5 % wound closure, compared to 84.02 % in the R gel group, and 73.02 % and 70.97 % in the control and burn cream groups, respectively. Immunohistochemistry and ELISA results further confirmed that RGJ significantly reduced wound and systemic inflammatory responses while promoting the secretion of pro-angiogenic factors VEGF and CD31, revealing its potential mechanism for enhancing burn wound healing. Additionally, RGJ significantly reduced wound scar formation and increased skin collagen deposition, demonstrating a favorable biosafety profile compared to the control group, commercial burn ointment, and the R-only treatment group. In conclusion, the development of the peptide nanofiber gel RGJ holds great potential for wound management applications and lays a foundation for future related research.

A novel combination therapy using Dapagliflozin and Cycas media extract in experimentally induced diabetic wounds by targeting novel pathways in wound healing

Diabetes mellitus, a globally prevalent condition, often complicates wound healing, leading to chronic, non-healing wounds. This study explores a novel combination therapy using Dapagliflozin and Cycas media extract for treating experimentally induced diabetic wounds in rats. By targeting the Notch signaling pathway, a critical pathway in wound healing, this research investigates the efficacy of this combination therapy in accelerating wound repair. Forty-two male Wistar albino rats were divided into control and treatment groups, receiving various Dapagliflozin and Cycas media gel combinations. The study evaluated wound healing, biochemical markers, gene expression, and histopathological changes. The findings suggest that the combination therapy significantly enhances wound healing, modulates oxidative stress, alters inflammatory responses, and influences key genes in the Notch pathway. This research provides a new perspective on diabetic wound management and underlines the potential of combining Dapagliflozin and Cycas media as a therapeutic approach.

Liver Fluke-Derived Molecules Accelerate Skin Repair Processes in a Mouse Model of Type 2 Diabetes Mellitus

Chronic nonhealing wounds, such as diabetic ulcers, are among the most serious complications of diabetes mellitus. Consequently, the search for new therapeutic strategies remains highly relevant. Based on our previous data on acute wounds, bioactive molecules derived from the liver fluke Opisthorchis felineus hold promise as a novel approach to wound healing. The aim of this study was to investigate the wound-healing properties of excretory-secretory products (ESP) and inactivated eggs of O. felineus in a model of type 2 diabetes mellitus. Two-month-old mice of the BKS.Cg + Leprdb/+Leprdb/OlaHsd (db/db) strain were inflicted with superficial wounds of 5 mm in diameter. Mouse groups included several controls (methylcellulose as the vehicle and human recombinant PDGF as the positive control) and specific-treatment groups (ESP and inactivated O. felineus eggs). Histopathological, immunohistochemical, and RT-PCR studies using markers for M1/M2 polarization, angiogenesis, and extracellular matrix remodeling were carried out. Additionally, an image analysis of Masson's trichrome-stained skin sections was performed. The proliferation of HaCaT cells under ESP and egg treatment was also assessed. The present study reveals a significant increase in the percentage of wound healing in ESP- and egg-treated groups, which significantly exceeded the control values after 14 days. Wound treatment with either ESP or worm eggs resulted in (i) a reduction in inflammation with a canonical M1-to-M2 polarization shift, (ii) the modulation of the vascular response, and (iii) dermal extracellular matrix remodeling. All results are comparable to those of the positive control group treated with PDGF. This study also reveals that ESP, but not O. felineus eggs, stimulated keratinocyte proliferation in vitro. The results indicate the high wound-healing potential of liver fluke bioactive molecules and open prospects for further research on these new promising therapeutic approaches.

Jagged-1+ skin Tregs modulate cutaneous wound healing

Skin-resident regulatory T cells (Tregs) play an irreplaceable role in orchestrating cutaneous immune homeostasis and repair, including the promotion of hair regeneration via the Notch signaling ligand Jagged-1 (Jag1). While skin Tregs are indispensable for facilitating tissue repair post-wounding, it remains unknown if Jag1-expressing skin Tregs impact wound healing. Using a tamoxifen inducible Foxp3creERT2Jag1fl/fl model, we show that loss of functional Jag1 in Tregs significantly delays the rate of full-thickness wound closure. Unlike in hair regeneration, skin Tregs do not utilize Jag1 to impact epithelial stem cells during wound healing. Instead, mice with Treg-specific Jag1 ablation exhibit a significant reduction in Ly6G + neutrophil accumulation at the wound site. However, during both homeostasis and wound healing, the loss of Jag1 in Tregs does not impact the overall abundance or activation profile of immune cell targets in the skin, such as CD4+ and CD8+ T cells, or pro-inflammatory macrophages. This collectively suggests that skin Tregs may utilize Jag1-Notch signalling to co-ordinate innate cell recruitment under conditions of injury but not homeostasis. Overall, our study demonstrates the importance of Jag1 expression in Tregs to facilitate adequate wound repair in the skin.

Alpha-boswellic acid accelerates acute wound healing via NF-κB signaling pathway

BACKGROUND

Boswellic acids (BAs) showed promising effects in cancer treatment, immune response regulation, and anti-inflammatory therapy. We aimed to assess the roles of alpha-BA (α-BA) in treating acute wound healing.

METHODS

In vivo wound-healing models were established to evaluate the therapeutic effects of α-BA. Cell assays were conducted to assess the impact of α-BA on cellular biological functions. Western blot analysis was employed to validate the potential mechanisms of action of α-BA.

RESULTS

Animal models indicated that wound healing was notably accelerated in the α-BA group compared to the control group (P < 0.01). Hematoxylin and eosin (HE) staining and enzyme-linked immunosorbent assay (ELISA) assay preliminarily suggested that α-BA may accelerate wound healing by inhibiting excessive inflammatory reactions and increasing the protein levels of growth factors. Cell function experiments demonstrated that α-BA suppressed the proliferation and migration ability of human hypertrophic scar fibroblasts (HSFBs), thereby favoring wound healing. Additionally, α-BA exerted a significant impact on cell cycle progression. Mechanistically, the protein levels of key genes in nuclear factor kappa beta (NF-κB) signaling pathway, including cyclin D1, p65, IκBα, and p-IκBα, were downregulated by α-BA.

CONCLUSIONS

α-BA demonstrated the ability to counteract the abnormal proliferation of skin scar tissues, consequently expediting wound healing. These findings suggest its potential for development as a new agent for treating acute wound healing.

Notch Signaling Hydrogels Enable Rapid Vascularization and Promote Dental Pulp Tissue Regeneration

Successful dental pulp regeneration is closely associated with rapid revascularization and angiogenesis, processes driven by the Jagged1(JAG1)/Notch signaling pathway. However, soluble Notch ligands have proven ineffective in activating this pathway. To overcome this limitation, a Notch signaling hydrogel is developed by indirectly immobilizing JAG1, aimed at precisely directing the regeneration of vascularized pulp tissue. This hydrogel displays favorable mechanical properties and biocompatibility. Cultivating dental pulp stem cells (DPSCs) and endothelial cells (ECs) on this hydrogel significantly upregulate Notch target genes and key proangiogenic markers expression. Three-dimensional (3D) culture assays demonstrate Notch signaling hydrogels improve effectiveness by facilitating encapsulated cell differentiation, enhancing their paracrine functions, and promoting capillary lumen formation. Furthermore, it effectively communicates with the Wnt signaling pathway, creating an odontoinductive microenvironment for pulp-dentin complex formation. In vivo studies show that short-term transplantation of the Notch signaling hydrogel accelerates angiogenesis, stabilizes capillary-like structures, and improves cell survival. Long-term transplantation further confirms its capability to promote the formation of pulp-like tissues rich in blood vessels and peripheral nerve-like structures. In conclusion, this study introduces a feasible and effective hydrogel tailored to specifically regulate the JAG1/Notch signaling pathway, showing potential in advancing regenerative strategies for dental pulp tissue.

Gamma-Secretase Inhibitors Downregulate the Profibrotic NOTCH Signaling Pathway in Recessive Dystrophic Epidermolysis Bullosa

Recessive dystrophic epidermolysis bullosa (RDEB) is a rare skin fragility disorder caused by mutations in COL7A1. RDEB is hallmarked by trauma-induced unremitting blistering, chronic wounds with inflammation, and progressive fibrosis, leading to severe disease complications. There is currently no cure for RDEB-associated fibrosis. Our previous studies and increasing evidence highlighted the profibrotic role of NOTCH pathway in different skin disorders, including RDEB. In this study, we further investigated the role of NOTCH signaling in RDEB pathogenesis and explored the effects of its inhibition by γ-secretase inhibitors DAPT and PF-03084014 (nirogacestat). Our analyses demonstrated that JAG1 and cleaved NOTCH1 are upregulated in primary RDEB fibroblasts (ie, RDEB-derived fibroblasts) compared with controls, and their protein levels are further increased by TGF-β1 stimulation. Functional assays unveiled the involvement of JAG1/NOTCH1 axis in RDEB fibrosis and demonstrated that its blockade counteracts a variety of fibrotic traits. In particular, RDEB-derived fibroblasts treated with PF-03084014 showed (i) a significant reduction of contractility, (ii) a diminished secretion of TGF-β1 and collagens, and (iii) the downregulation of several fibrotic proteins. Although less marked than PF-03084014-treated cells, RDEB-derived fibroblasts exhibited a reduction of fibrotic traits also upon DAPT treatment. This study provides potential therapeutic strategies to antagonize RDEB fibrosis onset and progression.

Notch signalling: multifaceted role in development and disease

Notch pathway is an evolutionarily conserved signalling system that operates to influence an astonishing array of cell fate decisions in different developmental contexts. Notch signalling plays important roles in many developmental processes, making it difficult to name a tissue or a developing organ that does not depend on Notch function at one stage or another. Thus, dysregulation of Notch signalling is associated with many developmental defects and various pathological conditions, including cancer. Although many recent advances have been made to reveal different aspects of the Notch signalling mechanism and its intricate regulation, there are still many unanswered questions related to how the Notch signalling pathway functions in so many developmental events. The same pathway can be deployed in numerous cellular contexts to play varied and critical roles in an organism's development and this is only possible because of the complex regulatory mechanisms of the pathway. In this review, we provide an overview of the mechanism and regulation of the Notch signalling pathway along with its multifaceted functions in different aspects of development and disease.

Endothelial to mesenchymal Notch signaling regulates skeletal repair

We present a transcriptomic analysis that provides a better understanding of regulatory mechanisms within the healthy and injured periosteum. The focus of this work is on characterizing early events controlling bone healing during formation of periosteal callus on day 3 after fracture. Building on our previous findings showing that induced Notch1 signaling in osteoprogenitors leads to better healing, we compared samples in which the Notch 1 intracellular domain is overexpressed by periosteal stem/progenitor cells, with control intact and fractured periosteum. Molecular mechanisms and changes in skeletal stem/progenitor cells (SSPCs) and other cell populations within the callus, including hematopoietic lineages, were determined. Notably, Notch ligands were differentially expressed in endothelial and mesenchymal populations, with Dll4 restricted to endothelial cells, whereas Jag1 was expressed by mesenchymal populations. Targeted deletion of Dll4 in endothelial cells using Cdh5CreER resulted in negative effects on early fracture healing, while deletion in SSPCs using α-smooth muscle actin-CreER did not impact bone healing. Translating these observations into a clinically relevant model of bone healing revealed the beneficial effects of delivering Notch ligands alongside the osteogenic inducer, BMP2. These findings provide insights into the regulatory mechanisms within the healthy and injured periosteum, paving the way for novel translational approaches to bone healing.

Targeting Wnt/β-catenin signaling and its interplay with TGF-β and Notch signaling pathways for the treatment of chronic wounds

Wound healing is a tightly regulated process that ensures tissue repair and normal function following injury. It is modulated by activation of pathways such as the transforming growth factor-beta (TGF-β), Notch, and Wnt/β-catenin signaling pathways. Dysregulation of this process causes poor wound healing, which leads to tissue fibrosis and ulcerative wounds. The Wnt/β-catenin pathway is involved in all phases of wound healing, primarily in the proliferative phase for formation of granulation tissue. This review focuses on the role of the Wnt/β-catenin signaling pathway in wound healing, and its transcriptional regulation of target genes. The crosstalk between Wnt/β-catenin, Notch, and the TGF-β signaling pathways, as well as the deregulation of Wnt/β-catenin signaling in chronic wounds are also considered, with a special focus on diabetic ulcers. Lastly, we discuss current and prospective therapies for chronic wounds, with a primary focus on strategies that target the Wnt/β-catenin signaling pathway such as photobiomodulation for healing diabetic ulcers.

Genome-wide association and functional genomic analyses for various hoof health traits in North American Holstein cattle

Hoof diseases are a major welfare and economic issue in the global dairy cattle production industry, which can be minimized through improved management and breeding practices. Optimal genetic improvement of hoof health could benefit from a deep understanding of the genetic background and biological underpinning of indicators of hoof health. Therefore, the primary objectives of this study were to perform genome-wide association studies, using imputed high-density genetic markers data from North American Holstein cattle, for 8 hoof-related traits: digital dermatitis, sole ulcer, sole hemorrhage, white line lesion, heel horn erosion, interdigital dermatitis, interdigital hyperplasia, and toe ulcer, and a hoof health index. De-regressed estimated breeding values from 25,580 Holstein animals were used as pseudo-phenotypes for the association analyses. The genomic quality control, genotype phasing, and genotype imputation were performed using the PLINK (version 1.9), Eagle (version 2.4.1), and Minimac4 software, respectively. The functional genomic analyses were performed using the GALLO R package and the DAVID platform. We identified 22, 34, 14, 22, 28, 33, 24, 43, and 15 significant markers for digital dermatitis, heel horn erosion, interdigital dermatitis, interdigital hyperplasia, sole hemorrhage, sole ulcer, toe ulcer, white line lesion disease, and the hoof health index, respectively. The significant markers were located across all autosomes, except BTA10, BTA12, BTA20, BTA26, BTA27, and BTA28. Moreover, the genomic regions identified overlap with various previously reported quantitative trait loci for exterior, health, meat and carcass, milk, production, and reproduction traits. The enrichment analyses identified 44 significant gene ontology terms. These enriched genomic regions harbor various candidate genes previously associated with bone development, metabolism, and infectious and immunological diseases. These findings indicate that hoof health traits are highly polygenic and influenced by a wide range of biological processes.

Dang-Gui-Bu-Xue decoction improves wound healing in diabetic rats by the activation of Notch signaling

Diabetes serves as a severe chronic disease that severely affects the normal life of human beings. Diabetes causes the complication of diabetic wound dysfunction, which is characterized by sustained inflammation, altered angiogenesis, delayed epithelialization and abnormal secretion of protease. Dang-Gui-Bu-Xue decoction (DBD) is a Chinese traditional medicine that comprises Radix Astragali and Radix Angelicae sinensis and is widely applied in treatment of multiple diseases owing to its functions against inflammation, lipid peroxidation and oxidative stress. Nevertheless, the impact of DBD on diabetic wound healing remains elusive. In this study, we aimed to explore the function of DBD in the regulation of wound healing. We observed that the gavage administration of DBD reduced the wound area, inflammatory infiltration, inflammatory factor levesl, and enhanced granulation tissue formation, wound extracellular matrix (ECM) production, and CD31 accumulation in the diabetic rat wound model, and the co-treatment of gavage administration and the external administration of gauze containing DBD further improved the wound healing effect, while the combination of Notch signaling inhibitor DAPT ((N- [N- (3, 5-difluorophenacetyl)-l-alanyl]-s-phenylglycinet-butyl ester)) could attenuate the improvement. Regarding to the mechanism, the expression levels of Notch1, Delta-like canonical Notch ligand 4 (Dll4), Jagged1, and Hairy Enhancer of Split-1 (Hes1) were increased by DBD, while the treatment of DAPT impaired the effect in the rats. Furthermore, we found that the high glucose (HG)-inhibited viability and tube formation were induced by DBD in human umbilical vein endothelial cells (HUVECs), in which DAPT could reverse this effect. Therefore, we concluded that DBD contributed to wound healing by the activation of Notch signaling. Our finding provides new insight into the potential role of DBD in promoting diabetic wound healing.

Targeting Signalling Pathways in Chronic Wound Healing

Chronic wounds fail to achieve complete closure and are an economic burden to healthcare systems due to the limited treatment options and constant medical attention. Chronic wounds are characterised by dysregulated signalling pathways. Research has focused on naturally derived compounds, stem-cell-based therapy, small molecule drugs, oligonucleotide delivery nanoparticles, exosomes and peptide-based platforms. The phosphoinositide-3-kinase (PI3K)/protein kinase B (AKT), Wingless-related integration (Wnt)/β-catenin, transforming growth factor-β (TGF-β), nuclear factor erythroid 2-related factor 2 (Nrf2), Notch and hypoxia-inducible factor 1 (HIF-1) signalling pathways have critical roles in wound healing by modulating the inflammatory, proliferative and remodelling phases. Moreover, several regulators of the signalling pathways were demonstrated to be potential treatment targets. In this review, the current research on targeting signalling pathways under chronic wound conditions will be discussed together with implications for future studies.

The alternate ligand Jagged enhances the robustness of Notch signaling patterns

The Notch pathway, an example of juxtacrine signaling, is an evolutionary conserved cell-cell communication mechanism. It governs emergent spatiotemporal patterning in tissues during development, wound healing and tumorigenesis. Communication occurs when Notch receptors of one cell bind to either of its ligands, Delta/Jagged of the neighboring cell. In general, Delta-mediated signaling drives neighboring cells to have an opposite fate (lateral inhibition) whereas Jagged-mediated signaling drives cells to maintain similar fates (lateral induction). Here, by deriving and solving a reduced set of 12 coupled ordinary differential equations for the Notch-Delta-Jagged system on a hexagonal grid of cells, we determine the allowed states across different parameter sets. We also show that Jagged (at low dose) acts synergistically with Delta to enable more robust pattern formation by making the neighboring cell states more distinct from each other, despite its lateral induction property. Our findings extend our understanding of the possible synergistic role of Jagged with Delta which had been previously proposed through experiments and models in the context of chick inner ear development. Finally, we show how Jagged can help to expand the bistable (both uniform and hexagon phases are stable) region, where a local perturbation can spread over time in an ordered manner to create a biologically relevant, perfectly ordered lateral inhibition pattern.

Variation in histone configurations correlates with gene expression across nine inbred strains of mice

The Diversity Outbred (DO) mice and their inbred founders are widely used models of human disease. However, although the genetic diversity of these mice has been well documented, their epigenetic diversity has not. Epigenetic modifications, such as histone modifications and DNA methylation, are important regulators of gene expression and, as such, are a critical mechanistic link between genotype and phenotype. Therefore, creating a map of epigenetic modifications in the DO mice and their founders is an important step toward understanding mechanisms of gene regulation and the link to disease in this widely used resource. To this end, we performed a strain survey of epigenetic modifications in hepatocytes of the DO founders. We surveyed four histone modifications (H3K4me1, H3K4me3, H3K27me3, and H3K27ac), as well as DNA methylation. We used ChromHMM to identify 14 chromatin states, each of which represents a distinct combination of the four histone modifications. We found that the epigenetic landscape is highly variable across the DO founders and is associated with variation in gene expression across strains. We found that epigenetic state imputed into a population of DO mice recapitulated the association with gene expression seen in the founders, suggesting that both histone modifications and DNA methylation are highly heritable mechanisms of gene expression regulation. We illustrate how DO gene expression can be aligned with inbred epigenetic states to identify putative cis-regulatory regions. Finally, we provide a data resource that documents strain-specific variation in the chromatin state and DNA methylation in hepatocytes across nine widely used strains of laboratory mice.

Germline protein, Cup, non-cell autonomously limits migratory cell fate in Drosophila oogenesis

Specification of migratory cell fate from a stationary population is complex and indispensable both for metazoan development as well for the progression of the pathological condition like tumor metastasis. Though this cell fate transformation is widely prevalent, the molecular understanding of this phenomenon remains largely elusive. We have employed the model of border cells (BC) in Drosophila oogenesis and identified germline activity of an RNA binding protein, Cup that limits acquisition of migratory cell fate from the neighbouring follicle epithelial cells. As activation of JAK-STAT in the follicle cells is critical for BC specification, our data suggest that Cup, non-cell autonomously restricts the domain of JAK-STAT by activating Notch in the follicle cells. Employing genetics and Delta endocytosis assay, we demonstrate that Cup regulates Delta recycling in the nurse cells through Rab11GTPase thus facilitating Notch activation in the adjacent follicle cells. Since Notch and JAK-STAT are antagonistic, we propose that germline Cup functions through Notch and JAK-STAT to modulate BC fate specification from their static epithelial progenitors.

Bacterial cellulose membrane combined with BMSCs promotes wound healing by activating the notch signaling pathway

Objective

The bacterial cellulose membrane (BCM) has been widely studied and applied as a new biomaterial for wound healing, but causes pain with frequent dressing changes. Local application of bone marrow mesenchymal stem cells (BMSCs) requires a niche. Furthermore, the effect and mechanism of the BCM combined with BMSCs have not been reported.

Methods

Morphological and chemical identifications of BCMs were investigated by porosity analyses, scanning electron microscopy, and Fourier-transform infrared spectroscopy. Biological wound dressings (BWDs) were prepared by the BCM in combination with BMSCs. The biological effects of BWDs on human dermal fibroblast (HDF) and VEGF-A in human vascular endothelial cells (HuVECs) were detected in vitro, and the effect of BWDs on acute wounds in mice was detected in vivo. Collagen and angiogenesis were evaluated through hematoxylin-eosin staining and Masson staining. The expressions of COL-1 and VEGF-A and the activation of the Notch signaling pathway in vivo and in vitro were detected by quantitative reverse-transcriptase polymerase chain reaction.

Results

The BCM had a nanoscale structure and provided a partial niche for the survival and proliferation of BMSCs. BWDs were successfully prepared and regulated the biological behaviors of wound healing-related cells in vitro and upregulated the expressions of COL-1 in HDF and VEGF-A in HuVECs. BWDs promoted wound healing by increasing collagen type I synthesis and angiogenesis in acute wounds in mice.

Conclusions

BWDs prepared by the combination of nanomaterial BCMs and BMSCs facilitated acute wound healing, which may be regulated by activating the Notch signaling pathway.

Implications of notch signaling in duchenne muscular dystrophy

This review focuses upon the implications of the Notch signaling pathway in muscular dystrophies, particularly Duchenne muscular dystrophy (DMD): a pervasive and catastrophic condition concerned with skeletal muscle degeneration. Prior work has defined the pathogenesis of DMD, and several therapeutic approaches have been undertaken in order to regenerate skeletal muscle tissue and ameliorate the phenotype. There is presently no cure for DMD, but a promising avenue for novel therapies is inducing muscle regeneration via satellite cells (muscle stem cells). One specific target using this approach is the Notch signaling pathway. The canonical Notch signaling pathway has been well-characterized and it ultimately governs cell fate decision, cell proliferation, and induction of differentiation. Additionally, inhibition of the Notch signaling pathway has been directly implicated in the deficits seen with muscular dystrophies. Here, we explore the connection between the Notch signaling pathway and DMD, as well as how Notch signaling may be targeted to improve the muscle degeneration seen in muscular dystrophies.

Identification and characterization of four immune-related signatures in keloid

A keloid is a fibroproliferative disorder of unknown etiopathogenesis that requires ill-defined treatment. Existing evidence indicates that the immune system plays an important role in the occurrence and development of keloid. However, there is still a lack of research on the immune-related signatures of keloid. Here we identified immune-related signatures in keloid and explored their pathological mechanisms. Transcriptomic datasets (GSE7890, GSE92566, and GSE44270) of keloid and normal skin tissues were obtained from the Gene Expression Omnibus database. The overlap of differentially expressed genes and immune-related genes was considered as differentially expressed immune-related genes (DEIGs). Functional analysis, expression, and distribution were applied to explore the function and characteristics of DEIGs, and the expression of these DEIGs in keloid and normal skin tissues was verified by immunohistochemistry. Finally, we conducted interactive network analysis and immune infiltration analysis to determine the therapeutic potential and immune correlation. We identified four DEIGs (LGR5, PTN, JAG1, and DKK1). In these datasets, only GSE7890 met the screening criteria. In the GSE7890 dataset, DKK1 and PTN were downregulated in keloid, whereas JAG1 and LGR5 were upregulated in keloid. In addition, we obtained the same conclusion through immunohistochemistry. Functional analysis indicated that these four DEIGs were mainly involved in stem cell, cell cycle, UV response, and therapy resistance. Through interactive network analysis, we found that these DEIGs were associated with drugs currently used to treat keloid, such as hydrocortisone, androstanolone, irinotecan, oxaliplatin, BHQ-880, and lecoleucovorin. Finally, many immune cells, including CD8⁺ T cells, resting memory CD4⁺ T cells, and M1 macrophages, were obtained by immune infiltration analysis. In conclusion, we identified four immune signaling molecules associated with keloid (LGR5, PTN, JAG1, and DKK1). These immune-related signaling molecules may be important modules in the pathogenesis of keloid. Additionally, we developed novel therapeutic targets for the treatment of this challenging disease.

Notch signaling: A possible therapeutic target and its role in diabetic foot ulcers

BACKGROUND & AIM

Diabetic foot ulcers are major cause of lower limb amputations in the diabetic population. The major factors that play a role in causing the delay of the process of healing in diabetic foot ulcers broadly are decreased angiogenesis, reduced proliferation and migration of keratinocytes/fibroblasts. The typical wound healing process has four phases which are overlapping with each other thus making the healing even more complex. Hence it is essential to identify a therapeutic target that involves the regulation of the cellular factors involved in healing and helps to increase angiogenesis and can regulate all four phases accordingly.

METHOD

Literature review involved a search of the databases namely, PubMed, Cochrane, EMBASE, and Web of Science database. Articles were identified and retrieved that specifically dealt with Notch as a target in healing of wounds and its mechanism of action on various cells and phases of healing.

RESULTS

Notch is a cell surface receptor which interacts with transmembrane ligands of the nearby cells and is involved in cell proliferation, differentiation, cell fate and death. It is also involved in cell-to-cell communication, cell signaling, and various phases of development. There exist four known notch genes and five ligands which interact with notch proteins. Hyperglycemia plays a role in the activation of the notch receptor thus causing the release of inflammatory mediators via macrophages. As notch can regulate macrophage-mediated inflammation it can serve as a therapeutic target for diabetic foot ulcers.

CONCLUSION

This review focuses on the effect of notch on various cell mediators and phases of diabetic wound healing and deals with how notch activation or inhibition can serve as a potential therapeutic target for healing diabetic foot ulcers.

The balance between protective and pathogenic immune responses to pneumonia in the neonatal lung is enforced by gut microbiota

Although modern clinical practices such as cesarean sections and perinatal antibiotics have improved infant survival, treatment with broad-spectrum antibiotics alters intestinal microbiota and causes dysbiosis. Infants exposed to perinatal antibiotics have an increased likelihood of life-threatening infections, including pneumonia. Here, we investigated how the gut microbiota sculpt pulmonary immune responses, promoting recovery and resolution of infection in newborn rhesus macaques. Early-life antibiotic exposure interrupted the maturation of intestinal commensal bacteria and disrupted the developmental trajectory of the pulmonary immune system, as assessed by single-cell proteomic and transcriptomic analyses. Early-life antibiotic exposure rendered newborn macaques more susceptible to bacterial pneumonia, concurrent with increases in neutrophil senescence and hyperinflammation, broad inflammatory cytokine signaling, and macrophage dysfunction. This pathogenic reprogramming of pulmonary immunity was further reflected by a hyperinflammatory signature in all pulmonary immune cell subsets coupled with a global loss of tissue-protective, homeostatic pathways in the lungs of dysbiotic newborns. Fecal microbiota transfer was associated with partial correction of the broad immune maladaptations and protection against severe pneumonia. These data demonstrate the importance of intestinal microbiota in programming pulmonary immunity and support the idea that gut microbiota promote the balance between pathways driving tissue repair and inflammatory responses associated with clinical recovery from infection in infants. Our results highlight a potential role for microbial transfer for immune support in these at-risk infants.

Regulatory Processes of the Canonical Wnt/β-Catenin Pathway and Photobiomodulation in Diabetic Wound Repair

Skin is a biological system composed of different types of cells within a firmly structured extracellular matrix and is exposed to various external and internal insults that can break its configuration. The restoration of skin's anatomic continuity and function following injury is a multifaceted, dynamic, well-coordinated process that is highly dependent on signalling pathways, including the canonical Wnt/β catenin pathway, all aimed at restoring the skin's protective barrier. Compromised and inappropriate tissue restoration processes are often the source of wound chronicity. Diabetic patients have a high risk of developing major impediments including wound contamination and limb amputation due to chronic, non-healing wounds. Photobiomodulation (PBM) involves the application of low-powered light at specific wavelengths to influence different biological activities that incite and quicken tissue restoration. PBM has been shown to modulate cellular behaviour through a variety of signal transduction pathways, including the Wnt/β catenin pathway; however, the role of Wnt/β catenin in chronic wound healing in response to PBM has not been fully defined. This review largely focuses on the role of key signalling pathways in human skin wound repair, specifically, the canonical Wnt/β-catenin pathway, and the effects of PBM on chronic wound healing.

AGEs-induced MMP-9 activation mediated by Notch1 signaling is involved in impaired wound healing in diabetic rats

AIMS

To elucidate the relationship between advanced glycation end products (AGEs), Notch1 signaling, nuclear factor-kappa B (NF-κB), and matrix metalloproteinase-9 (MMP-9) in diabetic wound healing in vitro and in vivo.

METHODS

We incubated primary keratinocytes with AGEs alone or AGEs along with γ-secretase inhibitor DAPT, and established diabetic rat wound model by intraperitoneal streptozotocin treatment. The Notch1 signaling components and MMP-9 expression were detected by qPCR, western blotting and gelatin zymography.

RESULTS

The exposure of primary keratinocytes to AGEs led to a significant increase in Notch intracellular domain (NICD), Delta-like 4 (Dll4), and Hes1; however, Notch1 expression was inhibited by the RAGE siRNA. Furthermore, MMP-9 activation was up-regulated, secondary to AGEs treatment. In contrast, increased MMP-9 expression by AGEs-stimulation was eliminated after treatment with DAPT. NF-κB activation participated in the Notch1-modulated MMP-9 expression. Notably, in the diabetic animal model, inhibition of the Notch signaling pathway with DAPT attenuated NICD and MMP-9 overexpression, improved collagen accumulation, and ultimately accelerated diabetic wound healing.

CONCLUSIONS

These findings identified that activation of the Notch1/NF-κB/MMP-9 pathway, in part, mediates the repressive effects of AGEs on diabetic wound healing and that targeting this pathway may be a potential strategy to improve impaired diabetic wound healing.

Three-Dimensional Culture Systems for Dissecting Notch Signalling in Health and Disease

Three-dimensional (3D) culture systems opened up new horizons in studying the biology of tissues and organs, modelling various diseases, and screening drugs. Producing accurate in vitro models increases the possibilities for studying molecular control of cell–cell and cell–microenvironment interactions in detail. The Notch signalling is linked to cell fate determination, tissue definition, and maintenance in both physiological and pathological conditions. Hence, 3D cultures provide new accessible platforms for studying activation and modulation of the Notch pathway. In this review, we provide an overview of the recent advances in different 3D culture systems, including spheroids, organoids, and “organ-on-a-chip” models, and their use in analysing the crucial role of Notch signalling in the maintenance of tissue homeostasis, pathology, and regeneration.

Comprehensive analysis of lncRNA and miRNA expression profiles and ceRNA network construction in negative pressure wound therapy

Background

This study aims to explore the molecular mechanism of negative pressure wound therapy (NPWT) at the transcriptome level through whole transcriptome sequencing and biometric analysis.

Methods

A rat skin defect model was constructed and randomly divided into a NPWT group and a gauze group. The tissue in the center of the wound was used for whole transcriptome sequencing, and differentially expressed messenger RNAs (DEmRNAs), long noncoding RNAs (DElncRNAs), and microRNAs (DEmiRNAs) were identified between the two groups. Quantitative real time-polymerase chain reaction (qRT-PCR) analysis was used to verify the sequencing results. Functional enrichment analysis, pathway analysis, and protein-protein interaction (PPI) network analysis of DEmRNAs were conducted. Through bioinformatics analysis, a lncRNA-associated competing endogenous RNA (ceRNA) network was identified and constructed.

Results

We detected 896 DEmRNAs, 1,471 DElncRNAs, and 20 DEmiRNAs between the two groups. qRT-PCR verified the sequencing results. Functional analysis showed that DEmRNAs were mainly enriched in immune system processes and the Notch signaling pathway. Protein tyrosine phosphatase receptor type C (PTPRC) and signal transducer and activator of transcription 1 (STAT1) were the central hub nodes in the PPI analysis. The ceRNA network contained 11 mRNAs, 15 lncRNAs, and 4 miRNAs.

Conclusions

We identified several DEmRNAs, DElncRNAs, and DEmiRNAs between the NPWT treatment group and the control group. These findings may provide new insights into the pathophysiological mechanism of NPWT and wound healing.

Cellular Signalling and Photobiomodulation in Chronic Wound Repair

Photobiomodulation (PBM) imparts therapeutically significant benefits in the healing of chronic wounds. Chronic wounds develop when the stages of wound healing fail to progress in a timely and orderly frame, and without an established functional and structural outcome. Therapeutic benefits associated with PBM include augmenting tissue regeneration and repair, mitigating inflammation, relieving pain, and reducing oxidative stress. PBM stimulates the mitochondria, resulting in an increase in adenosine triphosphate (ATP) production and the downstream release of growth factors. The binding of growth factors to cell surface receptors induces signalling pathways that transmit signals to the nucleus for the transcription of genes for increased cellular proliferation, viability, and migration in numerous cell types, including stem cells and fibroblasts. Over the past few years, significant advances have been made in understanding how PBM regulates numerous signalling pathways implicated in chronic wound repair. This review highlights the significant role of PBM in the activation of several cell signalling pathways involved in wound healing.

Stem Cell Therapy for Burns: Story so Far

Burn injuries affect approximately 11 million people annually, with fatalities amounting up to 180,000. Burn injuries constitute a global health issue associated with high morbidity and mortality. Recent years have seen advancements in regenerative medicine for burn wound healing encompassing stem cells and stem cell-derived products such as exosomes and conditioned media with promising results compared to current treatment approaches. Sources of stem cells used for treatment vary ranging from hair follicle stem cells, embryonic stem cells, umbilical cord stem cells, to mesenchymal stem cells, such as adipose-derived mesenchymal stem cells, bone marrow-derived mesenchymal stem cells, and even stem cells harvested from discarded burn tissue. Stem cells utilize various pathways for wound healing, such as PI3/AKT pathway, WNT-β catenin pathway, TGF-β pathway, Notch and Hedgehog signaling pathway. Due to the paracrine signaling mechanism of stem cells, exosomes and conditioned media derived from stem cells have also been utilized in burn wound therapy. As exosomes and conditioned media are cell-free therapy and contain various biomolecules that facilitate wound healing, they are gaining popularity as an alternative treatment strategy with significant improvement in outcomes. The treatment is provided either as direct injections or embedded in a natural/artificial scaffold. This paper reviews in detail the different sources of stem cells, stem cell-derived products, their efficacy in burn wound repair, associated signaling pathways and modes of delivery for wound healing.

The multi-functional roles of forkhead box protein O in skin aging and diseases

Forkhead box, class O (FoxO) family members are multifunctional transcription factors that are involved in several metabolic processes, including energy metabolism, apoptosis, DNA repair, and oxidative stress. However, their roles in skin health have not been well-documented. Recent studies have indicated that FoxOs are important factors to control skin homeostasis and health. The activation or deactivation of some FoxO family members is closely related to melanogenesis, wound healing, acne, and melanoma. In this review, we have discussed the recent findings that demonstrate the relationship between FoxOs and skin health as well as the underlying mechanisms associated with their functions.

Effects of a gamma-secretase inhibitor of notch signalling on transforming growth factor β1-induced urethral fibrosis

Urethral stricture (US) is a common disorder of the lower urinary tract in men caused by fibrosis. The recurrence rate of US is high; however, there are no effective therapies to prevent or treat urethral fibrosis. The pathogenesis of urethral fibrosis involves myofibroblast activation and excessive extracellular matrix (ECM) deposition. The molecular mechanisms underlying this pathological activation are not completely understood. It has been demonstrated that Notch signalling contributes to the development of fibrosis and inflammation. However, whether this contributes to urethral fibrosis remains unclear. In this study, activation of Notch signalling was observed in patients with US. Additionally, it was noted that activation of Notch signalling promoted ECM production and myofibroblast activation in human urethral scar fibroblasts (HUSFs) treated with transforming growth factor (TGF) β1. However, the Notch inhibitor N‐[N‐(3,5‐difluorophenacetyl)‐L‐alanyl]‐S‐phenylglycine t‐butyl ester (DAPT) suppressed activation of Notch signalling as well as proliferation and migration of the TGFβ1‐treated HUSFs. Additionally, DAPT ameliorated TGFβ1‐induced urethral fibrosis in Sprague Dawley rats by suppressing ECM production, myofibroblast activation and the TGFβ signalling pathway. These findings demonstrate that Notch signalling may be a promising and potential target in the prevention or treatment of urethral fibrosis.

Chronic pesticide exposure induced aberrant Notch signalling along the visual pathway in a murine model

Pesticides aid in crop-protection against pests and increase yield. However, the xenobiotic stress exerted by pesticides leads to the deterioration of human and animal health. There is a lacuna in our knowledge about their impact on the ocular surface The present work sheds light on this gap by analysing the deterioration of visual acuity as a consequence of pesticide induced xenobiotic stress and Notch pathway dysregulation. Alteration in the expression of vital components of the notch signalling was analyzed along the visual pathway with special focus on its two terminals-the cornea and the visual cortex, by mimicking the on-field scenario regarding chronic pesticide exposure in experimental murine model (Swiss albino mice; Mus musculus). Various aspects were taken into consideration through visual acuity tests, histological evaluations, culture analyses, wound healing assays, flowcytometric evaluation, fluorescence microscopic studies etc. Complete dysregulation of key players of the Notch signalling pathway was observed in both: cells of the ocular surface as well as those in the murine visual cortex post pesticide exposure, indicating activities relating to cell proliferation, differentiation and wound healing in the pesticide exposed samples. Ultra-microscopic analyses corroborated our findings by revealing the loss of fine neural processes in the visual cortex of the pesticide exposed murine samples, thereby hinting at delayed perception to visual stimuli. In vivo evaluations of the functional capacity of the neuroanatomical structures along the visual pathway also confirmed that pesticide exposure leads to severe damage along the various parts of the visual pathway, right from the ocular surface to the visual cortex.

Adipose mesenchymal stem cells combined with platelet-rich plasma accelerate diabetic wound healing by modulating the Notch pathway

Background

Diabetic foot ulceration is a serious chronic complication of diabetes mellitus characterized by high disability, mortality, and morbidity. Platelet-rich plasma (PRP) has been widely used for diabetic wound healing due to its high content of growth factors. However, its application is limited due to the rapid degradation of growth factors. The present study aimed to evaluate the efficacy of combined adipose-derived mesenchymal stem cells (ADSCs) and PRP therapy in promoting diabetic wound healing in relation to the Notch signaling pathway.

Methods

Albino rats were allocated into 6 groups [control (unwounded), sham (wounded but non-diabetic), diabetic, PRP-treated, ADSC-treated, and PRP+ADSCs-treated groups]. The effect of individual and combined therapy was evaluated by assessing wound closure rate, epidermal thickness, dermal collagen, and angiogenesis. Moreover, gene and protein expression of key elements of the Notch signaling pathway (Notch1, Delta-like canonical Notch ligand 4 (DLL4), Hairy Enhancer of Split-1 (Hes1), Hey1, Jagged-1), gene expression of angiogenic marker (vascular endothelial growth factor and stromal cell-derived factor 1) and epidermal stem cells (EPSCs) related gene (ß1 Integrin) were assessed.

Results

Our data showed better wound healing of PRP+ADSCs compared to their individual use after 7 and 14 days as the combined therapy caused reepithelialization and granulation tissue formation with a marked increase in area percentage of collagen, epidermal thickness, and angiogenesis. Moreover, Notch signaling was significantly downregulated, and EPSC proliferation and recruitment were enhanced compared to other treated groups and diabetic groups.

Conclusions

These data demonstrated that PRP and ADSCs combined therapy significantly accelerated healing of diabetic wounds induced experimentally in rats via modulating the Notch pathway, promoting angiogenesis and EPSC proliferation.

Age-associated expression of p21and p53 during human wound healing

In mice, cellular senescence and senescence-associated secretory phenotype (SASP) positively contribute to cutaneous wound healing. In this proof-of-concept study, we investigated the expressions of p16, p21, and other senescence-associated biomarkers during human wound healing in 24 healthy subjects using a double-biopsy experimental design. The first punch biopsy created the wound and established the baseline. The second biopsy, concentric to the first and taken several days after wounding, was used to probe for expression of biomarkers by immunohistochemistry and RNA FISH. To assess the effects of age, we recruited 12 sex-matched younger (30.2 ± 1.3 years) and 12 sex-matched older (75.6 ± 1.8 years) subjects. We found that p21 and p53, but not p16, were induced during healing in younger, but not older subjects. A role for Notch signaling in p21 expression was inferred from the inducible activation of HES1. Further, other SASP biomarkers such as dipeptidyl peptidase-4 (DPP4) were significantly induced upon wounding in both younger and older groups, whereas matrix metallopeptidase 9 (MMP9) was induced only in the younger group. Senescence-associated β-galactosidase (SA-β-gal) was not detectable before or after wounding. This pilot study suggests the possibility that human cutaneous wound healing is characterized by differential expression of p21 and p53 between younger and older subjects.

The interaction of Notch and Wnt signaling pathways in vertebrate regeneration

Regeneration is an evolutionarily conserved process in animal kingdoms, however, the regenerative capacities differ from species and organ/tissues. Mammals possess very limited regenerative potential to replace damaged organs, whereas non-mammalian species usually have impressive abilities to regenerate organs. The regeneration process requires proper spatiotemporal regulation from key signaling pathways. The canonical Notch and Wnt signaling pathways, two fundamental signals guiding animal development, have been demonstrated to play significant roles in the regeneration of vertebrates. In recent years, increasing evidence has implicated the cross-talking between Notch and Wnt signals during organ regeneration. In this review, we summarize the roles of Notch signaling and Wnt signaling during several representative organ regenerative events, emphasizing the functions and molecular bases of their interplay in these processes, shedding light on utilizing these two signaling pathways to enhance regeneration in mammals and design legitimate therapeutic strategies.

Redox treatment ameliorates diabetes mellitus-induced skin flap necrosis via inhibiting apoptosis and promoting neoangiogenesis

Intractable wound healing is the habitual problem of diabetes mellitus. High blood glucose limits wound healing by interrupting inflammatory responses and inhibiting neoangiogenesis. Oxidative stress is commonly thought to be a major pathogenic cause of diabetic complications. Edaravone (3-methyl-1-phenyl-2-pyrazolin-5-one, EDV) is a free radical scavenger which suppress oxidative stress. This study investigates whether EDV can reduce oxidative stress in wound healing HaCaT/human dermal fibroblasts cells (HDFs) in vitro and in vivo animal model. Cell viability and wound healing assays, FACS flow cytometry, and Hoechst 33342 staining were performed to confirm apoptosis and cytotoxicity in H2O2 and EDV-treated HaCaT and HDFs. A streptozotocin-induced hyperglycemic animal model was made in adult C57BL6 mice. Full-thickness skin flap was made on dorsomedial back and re-sutured to evaluate the wound healing process. EDV was delivered slowly in the skin flap with degradable fibrin glue. The flap was monitored and analyzed on postoperative days 1, 3, and 5. CD31/DAPI staining was done to detect newly formed blood vessels. The expression levels of NF-κB, bcl-2, NOX3, and STAT3 proteins in C57BL6 mouse tissues were also examined. The wound healing process in hyper- and normoglycemic mice showed a difference in protein expression, especially in oxidative stress management and angiogenesis. Exogenous H2O2 reduced cell viability in a proportion to the concentration via apoptosis. EDV protected HaCaT cells and HDFs from H2O2 induced reactive oxygen species cell damage and apoptosis. In the mouse model, EDV with fibrin resulted in less necrotic areas and increased angiogenesis on postoperative day 5, compared to sham-treated mice. Our results indicate that EDV could protect H2O2-induced cellular injury via inhibiting early apoptosis and inflammation and also increasing angiogenesis. EDV might be valuable in the treatment of diabetic wounds that oxidative stress has been implicated.

Role of cell polarity dynamics and motility in pattern formation due to contact-dependent signalling

A key challenge in biology is to understand how spatio-temporal patterns and structures arise during the development of an organism. An initial aggregate of spatially uniform cells develops and forms the differentiated structures of a fully developed organism. On the one hand, contact-dependent cell-cell signalling is responsible for generating a large number of complex, self-organized, spatial patterns in the distribution of the signalling molecules. On the other hand, the motility of cells coupled with their polarity can independently lead to collective motion patterns that depend on mechanical parameters influencing tissue deformation, such as cellular elasticity, cell-cell adhesion and active forces generated by actin and myosin dynamics. Although modelling efforts have, thus far, treated cell motility and cell-cell signalling separately, experiments in recent years suggest that these processes could be tightly coupled. Hence, in this paper, we study how the dynamics of cell polarity and migration influence the spatiotemporal patterning of signalling molecules. Such signalling interactions can occur only between cells that are in physical contact, either directly at the junctions of adjacent cells or through cellular protrusional contacts. We present a vertex model which accounts for contact-dependent signalling between adjacent cells and between non-adjacent neighbours through long protrusional contacts that occur along the orientation of cell polarization. We observe a rich variety of spatiotemporal patterns of signalling molecules that is influenced by polarity dynamics of the cells, relative strengths of adjacent and non-adjacent signalling interactions, range of polarized interaction, signalling activation threshold, relative time scales of signalling and polarity orientation, and cell motility. Though our results are developed in the context of Delta-Notch signalling, they are sufficiently general and can be extended to other contact dependent morpho-mechanical dynamics.

Primary Ciliary Signaling in the Skin-Contribution to Wound Healing and Scarring

Primary cilia (PC) are solitary, post-mitotic, microtubule-based, and membrane-covered protrusions that are found on almost every mammalian cell. PC are specialized cellular sensory organelles that transmit environmental information to the cell. Signaling through PC is involved in the regulation of a variety of cellular processes, including proliferation, differentiation, and migration. Conversely, defective, or abnormal PC signaling can contribute to the development of various pathological conditions. Our knowledge of the role of PC in organ development and function is largely based on ciliopathies, a family of genetic disorders with mutations affecting the structure and function of PC. In this review, we focus on the role of PC in their major signaling pathways active in skin cells, and their contribution to wound healing and scarring. To provide comprehensive insights into the current understanding of PC functions, we have collected data available in the literature, including evidence across cell types, tissues, and animal species. We conclude that PC are underappreciated subcellular organelles that significantly contribute to both physiological and pathological processes of the skin development and wound healing. Thus, PC assembly and disassembly and PC signaling may serve as attractive targets for antifibrotic and antiscarring therapies.

Dll4 Blockade Promotes Angiogenesis in Nonhealing Wounds of Sox7-Deficient Mice

Objective: This study aimed to elucidate the role of the proangiogenic transcription factors Sox7 and Sox17 in the wound healing process and investigate the therapeutic potential of Dll4 blockade, which is an upstream regulator of Sox17, for the treatment of nonhealing wounds.

Approach: After generating a full-thickness skin defect wound model of endothelial Sox7- and/or Sox17-deficient mice, we measured the wound healing rates and performed histological analysis. The effects of an anti-Dll4 antibody on wound angiogenesis in Sox7-deficient mice and db/db diabetic mice were assessed.

Results: Sox7 and/or Sox17 deletion delayed wound healing. Moreover, the loss of Sox7 and Sox17 inhibited wound angiogenesis, without affecting the expression of the other. Of interest, after anti-Dll4 antibody treatment, Sox17 levels were increased and the suppression of angiogenesis was alleviated in Sox7-deficient mice and db/db diabetic mice. Consequently, Dll4 blockade effectively recovered the observed delay in wound healing.

Innovation: The proangiogenic role of Sox7 and Sox17 in wound angiogenesis was addressed and effective treatment of nonhealing wounds by Dll4 blockade was suggested.

Conclusion: This study revealed the proangiogenic role of the transcription factors Sox7 and Sox17 in wound angiogenesis. Furthermore, we suggest a novel method for treating nonhealing wounds by particularly targeting the Dll4–Sox17 axis.

Designing Biomaterials to Modulate Notch Signaling in Tissue Engineering and Regenerative Medicine

The design of cell-instructive biomaterials for tissue engineering and regenerative medicine is at a crossroads. Although the conventional tissue engineering approach is top-down (cells seeded to macroporous scaffolds and mature to form tissues), bottom-up tissue engineering strategies are becoming appealing. With such developments, we can study cell signaling events, thus enabling functional tissue assembly in physiologic and diseased models. Among many important signaling pathways, the Notch signaling pathway is the most diverse in its influence during tissue morphogenesis and repair following injury. Although Notch signaling is extensively studied in developmental biology and cancer biology, our knowledge of designing biomaterial-based Notch signaling platforms and incorporating Notch signaling components into engineered tissue systems is limited. By incorporating Notch signaling to tissue engineering scaffolds, we can direct cell-specific responses and improve engineered tissue maturation. This review will discuss recent progress in the development of Notch signaling biomaterials as a promising target to control cellular fate decisions, including the influences of ligand identity, biophysical material cues, ligand presentation strategies, and mechanotransduction. Notch signaling is consequently of interest to direct, control, and reprogram cellular behavior on a biomaterial surface. We anticipate that discussions in this article will allow for enhanced knowledge and insight into designing Notch targeted biomaterials for various tissue engineering and cell fate determinations. Impact statement Notch signaling is recognized as an important pathway in tissue engineering and regenerative medicine; however, there is no systematic review on this topic. The comprehensive review and perspectives presented here provide an in-depth discussion on ligand presentation strategies both in 2D and in 3D cell culture environments involving biomaterials/scaffolds. In addition, this review article provides insight into the challenges in designing cell surrogate biomaterials capable of providing Notch signals. To the best of the authors' knowledge, this is the first review relevant to the fields of tissue engineering.

Gene expression changes associated with malignant transformation of oral potentially malignant disorders

BACKGROUND

A large number of oral squamous cell carcinomas (OSCCs) are believed to be preceded by oral potentially malignant disorders (OPMD) that have an increased likelihood of malignant transformation compared to clinically normal mucosa. This study was performed to identify differentially expressed genes between OPMDs that underwent malignant transformation (MT) and those that did not, termed "non-transforming" (NT) cases.

METHODS

Total RNA was extracted from formalin-fixed paraffin-embedded tissue biopsies of 20 OPMD cases with known clinical outcomes (10 MT vs. 10 NT). Samples were assessed for quantity, quality and integrity of RNA prior to sequencing. Analysis for differential gene expression between MT and NT was performed using statistical packages in R. Genes were considered to be significantly differentially expressed if the False Discovery Rate corrected P-value was < 0.05.

RESULTS

RNA yield was variable but RNA purity was good (A260/A280 > 1.90). Analysis of RNA-Sequencing outputs revealed 41 genes (34 protein-coding; 7 non-coding) that were significantly differentially expressed between MT and NT cases. The log2 fold change for the statistically significant differentially expressed genes ranged from -2.63 to 2.48, with 23 protein-coding genes being downregulated and 11 protein-coding genes being upregulated in MT cases compared to NT cases.

CONCLUSION

Several candidate genes that may play a role in malignant transformation of OPMD have been identified. Experiments to validate these candidates are underway. It is anticipated that this work will contribute to better understanding of the etiopathogenesis of OPMD and development of novel biomarkers.

Small Extracellular Vesicles from Human Fetal Dermal Cells and Their MicroRNA Cargo: KEGG Signaling Pathways Associated with Angiogenesis and Wound Healing

The use of cell secreted factors in clinical settings could be an alternative to conventional cell therapy, with the advantage of limiting concerns generally associated with traditional cell transplantation, such as tumorigenicity, immunoreactivity, and carrying of infections. Based on our published data, we predict a potential role for extracellular vesicles (EVs) in contributing to the proangiogenic activity of human fetal dermal cell secretome. Depletion of nanosized EVs from secretome significantly impaired its ability to induce formation of mesh-like structures in vitro. The isolated EVs were characterized for size and concentration by nanoparticle tracking analysis, and for protein markers (Rab5⁺, Alix⁺, CD63⁺, and calnexin⁻). The microRNA profile of EVs revealed 87 microRNAs significantly upregulated (≥15-fold increase) in fetal compared to adult dermal cell-derived EVs. Interestingly, these upregulated microRNAs included microRNAs with a validated role in angiogenesis according to literature. Moreover, the DIANA-TarBase v7.0 analysis confirmed enrichment in the KEGG signaling pathways associated with angiogenesis and wound healing, with the identification of putative target genes including thrombospondin 1. To validate the in silico data, EVs were also characterized for total protein contents. When tested in in vitro angiogenesis, fetal dermal cell-derived EVs were more effective than their adult counterpart in inducing formation of complete mesh-like structures. Furthermore, treatment of fibroblasts with fetal dermal-derived EVs determined a 4-fold increase of thrombospondin 1 protein amounts compared with the untreated fibroblasts. Finally, visualization of CSFE-labeled EVs in the cytosol of target cells suggested a successful uptake of these particles at 4-8 hours of incubation. We conclude that EVs are important contributors of the proangiogenic effect of fetal dermal cell secretome. Hence, EVs could also serve as vehicle for a successful delivery of microRNAs or other molecules of therapeutic interest to target cells.

Production and characterization of poly lactic-co-glycolic acid particles containing anti-inflammatory substances for skin lesion recovery

Poly lactic-co-glycolic acid particles are biodegradable and biocompatible drug delivery systems that provide a controlled release of drugs in specific sites. These characteristics minimize the occurrence of side effects related to overdosing. To overcome the issues associated with the conservative treatment for wound healing, the objective of this work was to develop a poly lactic-co-glycolic acid particles system to deliver anti-inflammatory compounds (epigallocatechin gallate and asiaticoside) to fibroblasts. Nanoscale (~200 nm) and microscale (~10 µm) poly lactic-co-glycolic acid particles were produced using two different protocols. Nanoscale particles reduced cell proliferation by 46% compared with untreated human skin fibroblasts, whereas microscale particles did not affect fibroblast viability significantly. The toxicity of nanoparticles and the nontoxic nature of microparticles were confirmed in live and dead cell staining experiments. In vitro drug release assays showed that particles containing epigallocatechin gallate and asiaticoside were able to release most of their payload during the first 8 h of incubation. The treatment of lipopolysaccharide-stimulated fibroblasts with epigallocatechin gallate- and asiaticoside-loaded microparticles effectively suppressed the expression of inflammatory factors: tumor necrosis factor-α, interleukin-1β, and interleukin-6. In this study, we found that the optimal size of biodegradable poly lactic-co-glycolic acid particles for the delivery of physiologically active substances to fibroblasts is about 10 μm. Moreover, our findings indicate that poly lactic-co-glycolic acid particles of this size can be effectively applied to ameliorate tissue regeneration by delivering physiologically active substances to improve skin lesion recovery.

Pleiotropic Role of Notch Signaling in Human Skin Diseases

Notch signaling orchestrates the regulation of cell proliferation, differentiation, migration and apoptosis of epidermal cells by strictly interacting with other cellular pathways. Any disruption of Notch signaling, either due to direct mutations or to an aberrant regulation of genes involved in the signaling route, might lead to both hyper- or hypo-activation of Notch signaling molecules and of target genes, ultimately inducing the onset of skin diseases. The mechanisms through which Notch contributes to the pathogenesis of skin diseases are multiple and still not fully understood. So far, Notch signaling alterations have been reported for five human skin diseases, suggesting the involvement of Notch in their pathogenesis: Hidradenitis Suppurativa, Dowling Degos Disease, Adams-Oliver Syndrome, Psoriasis and Atopic Dermatitis. In this review, we aim at describing the role of Notch signaling in the skin, particularly focusing on the principal consequences associated with its alterations in these five human skin diseases, in order to reorganize the current knowledge and to identify potential cellular mechanisms in common between these pathologies.

Extracellular Vesicles Derived From Mesenchymal Stem Cells (MSC) in Regenerative Medicine: Applications in Skin Wound Healing

The cells secrete extracellular vesicles (EV) that may have an endosomal origin, or from evaginations of the plasma membrane. The former are usually called exosomes, with sizes ranging from 50 to 100 nm. These EV contain a lipid bilayer associated to membrane proteins. Molecules such as nucleic acids (DNA, mRNA, miRNA, lncRNA, etc.) and proteins may be stored inside. The EV composition depends on the producer cell type and its physiological conditions. Through them, the cells modify their microenvironment and the behavior of neighboring cells. That is accomplished by transferring factors that modulate different metabolic and signaling pathways. Due to their properties, EV can be applied as a diagnostic and therapeutic tool in medicine. The mesenchymal stromal cells (MSC) have immunomodulatory properties and a high regenerative capacity. These features are linked to their paracrine activity and EV secretion. Therefore, research on exosomes produced by MSC has been intensified for use in cell-free regenerative medicine. In this area, the use of EV for the treatment of chronic skin ulcers (CSU) has been proposed. Such sores occur when normal healing does not resolve properly. That is usually due to excessive prolongation of the inflammatory phase. These ulcers are associated with aging and diseases, such as diabetes, so their prevalence is increasing with the one of such latter disease, mainly in developed countries. This has very important socio-economic repercussions. In this review, we show that the application of MSC-derived EV for the treatment of CSU has positive effects, including accelerating healing and decreasing scar formation. This is because the EV have immunosuppressive and immunomodulatory properties. Likewise, they have the ability to activate the angiogenesis, proliferation, migration, and differentiation of the main cell types involved in skin regeneration. They include endothelial cells, fibroblasts, and keratinocytes. Most of the studies carried out so far are preclinical. Therefore, there is a need to advance more in the knowledge about the conditions of production, isolation, and action mechanisms of EV. Interestingly, their potential application in the treatment of CSU opens the door for the design of new highly effective therapeutic strategies.

Platelet-Rich Plasma with Endothelial Progenitor Cells Accelerates Diabetic Wound Healing in Rats by Upregulating the Notch1 Signaling Pathway

Diabetic wounds, as a kind of refractory wound, are very difficult to heal. Both endothelial progenitor cell (EPC) transplantation and platelet-rich plasma (PRP) can improve diabetic wound healing to some extent. However, PRP application cannot provide reparative cells, while EPC transplantation cannot replenish the required growth factors for wound healing. Thus, when applied alone, neither of these factors is sufficient for effective wound healing. Furthermore, the proliferation, differentiation, and fate of the transplanted EPCs are not well known. Therefore, in this study, we examined the efficacy of combined PRP application with EPC transplantation in diabetic wound healing. Our results indicated that PRP application improved EPC proliferation and migration. The Notch signaling pathway plays a key role in the regulation of the proliferation and differentiation of stem cells and angiogenesis in wound healing. The application of PRP upregulated the Notch pathway-related gene and protein expression in EPCs. Furthermore, experiments with shNotch1-transfected EPCs indicated that PRP enhanced the function of EPCs by upregulating the Notch1 signaling pathway. In vivo studies further indicated that the combination of PRP and EPC transplantation increased neovascularization, reduced wound size, and improved healing in rat wound models. Thus, PRP application can provide the necessary growth factors for wound healing, while EPC transplantation offers the required cells, indicating that the combination of both is a potent novel approach for treating diabetic wounds.

Role of the Notch Signaling Pathway in Fibrosis of Denervated Skeletal Muscle

In order to investigate the role of the Notch signaling pathway in skeletal muscle fibrosis after nerve injury, 60 Sprague-Dawley rats were selected and divided randomly into a control and two experimental groups. Group A served as controls without any treatment. Rats in groups B were injected intraperitoneally with 0.2 mL PBS and those in group C were injected intraperitoneally with 0.2 mL PBS+100 μmol/L, 0.2 mL N-[N-(3,5-difluorophenacetyl)-l-alanyl]- S-phenylglycine t-butyl ester (DAPT, a gamma-secretase inhibitor that suppresses Notch signaling) respectively, on postoperative days 1, 3, 7, 10, and 14 in a model of denervation-induced skeletal muscle fibrosis by right sciatic nerve transection. Five rats from each group were euthanized on postoperative days 1, 7, 14, and 28 to collect the right gastrocnemii, and hematoxylin and eosin (HE) staining, immunohistochemistry test, real-time PCR, and Western blotting were performed to assess connective tissue hyperplasia and fibroblast density as well as expression of Notch 1, Jagged 1, and Notch downstream molecules Hes 1 and collagen I (COL I) on day 28. There was no significant difference in HE-stained fibroblast density between group B and C on postoperative day 1. However, fibroblast density was significantly higher in group B than in group C on postoperative days 7, 14, and 28. Notch 1, Jagged 1, Hes 1, and COL I proteins in the gastrocnemius were expressed at very low levels in group A but at high levels in group B. Expression levels of these proteins were significantly lower in group C than in group B (P<0.05), but they were higher in group C than in group A (P<0.05) on postoperative day 28. We are led to conclude that locking the Notch signaling pathway inhibits fibrosis progression of denervated skeletal muscle. Thus, it may be a new approach for treatment of fibrosis of denervated skeletal muscle.

Fetal Dermal Mesenchymal Stem Cell-Derived Exosomes Accelerate Cutaneous Wound Healing by Activating Notch Signaling

Fetal dermal mesenchymal stem cells (FDMSCs), isolated from fetal skin, are serving as a novel MSC candidate with great potential in regenerative medicine. More recently, the paracrine actions, especially MSC-derived exosomes, are being focused on the vital role in MSC-based cellular therapy. This study was to evaluate the therapeutic potential of exosomes secreted by FDMSCs in normal wound healing. First, the in vivo study indicated that FDMSC exosomes could accelerate wound closure in a mouse full-thickness skin wound model. Then, we investigated the role of FDMSC-derived exosomes on adult dermal fibroblast (ADFs). The results demonstrated that FDMSC exosomes could induce the proliferation, migration, and secretion of ADFs. We discovered that after treatment of exosomes, the Notch signaling pathway was activated. Then, we found that in FDMSC exosomes, the ligands of the Notch pathway were undetectable expect for Jagged 1, and the results of Jagged 1 mimic by peptide and knockdown by siRNA suggested that Jagged 1 may lead the activation of the Notch signal in ADFs. Collectively, our findings indicated that the FDMSC exosomes may promote wound healing by activating the ADF cell motility and secretion ability via the Notch signaling pathway, providing new aspects for the therapeutic strategy of FDMSC-derived exosomes for the treatment of skin wounds.

Triggering of a Dll4-Notch1 loop impairs wound healing in diabetes

Diabetic foot ulcerations (DFUs) represent a major medical, social, and economic problem. Therapeutic options are restricted due to a poor understanding of the pathogenic mechanisms. The Notch pathway plays a pivotal role in cell differentiation, proliferation, and angiogenesis, processes that are profoundly disturbed in diabetic wounds. Notch signaling is activated upon interactions between membrane-bound Notch receptors (Notch 1-4) and ligands (Jagged 1-2 and Delta-like 1, 3, 4), resulting in cell-context-dependent outputs. Here, we report that Notch1 signaling is activated by hyperglycemia in diabetic skin and specifically impairs wound healing in diabetes. Local inhibition of Notch1 signaling in experimental wounds markedly improves healing exclusively in diabetic, but not in nondiabetic, animals. Mechanistically, high glucose levels activate a specific positive Delta-like 4 (Dll4)-Notch1 feedback loop. Using loss-of-function genetic approaches, we demonstrate that Notch1 inactivation in keratinocytes is sufficient to cancel the repressive effects of the Dll4-Notch1 loop on wound healing in diabetes, thus making Notch1 signaling an attractive locally therapeutic target for the treatment of DFUs.

Notch signaling pathway is a potential therapeutic target for extracranial vascular malformations

Notch expression has been shown to be aberrant in brain arteriovenous malformations (AVM), and targeting Notch has been suggested as an approach to their treatment. It is unclear whether extracranial vascular malformations follow the same patterning and Notch pathway defects. In this study, we examined human extracranial venous (VM) (n = 3), lymphatic (LM) (n = 10), and AV (n = 6) malformations, as well as sporadic brain AVMs (n = 3). In addition to showing that extracranial AVMs demonstrate interrupted elastin and that AVMs and LMs demonstrate abnormal α-smooth muscle actin just as brain AVMS do, our results demonstrate that NOTCH1, 2, 3 and 4 proteins are overexpressed to varying degrees in both the endothelial and mural lining of the malformed vessels in all types of malformations. We further show that two gamma secretase inhibitors (GSIs), DAPT (GSI-IX) and RO4929097, cause dose-dependent inhibition of Notch target gene expression (Hey1) and rate of migration of monolayer cultures of lymphatic endothelial cells (hLECs) and blood endothelial cells (HUVEC). GSIs also inhibit HUVEC network formation. hLECs are more sensitive to GSIs compared to HUVEC. GSIs have been found to be safe in clinical trials in patients with Alzheimer’s disease or cancer. Our results provide further rationale to support testing of Notch inhibitors in patients with extracranial vascular malformations.