Exploiting PI3K/mTOR signaling to accelerate epithelial wound healing

CD9 promotes TβR2-TβR1 association driving the transition of human dermal fibroblasts to myofibroblast under hypoxia

BACKGROUND

During wound healing, fibroblast to myofibroblast transition is required for wound contraction and remodeling. While hypoxia is an important biophysical factor in wound microenvironment, the exact regulatory mechanism underlying hypoxia and fibroblast-to-myofibroblast transition remains unclear. We previously found that tetraspanin CD9 plays an important role in oxygen sensing and wound healing. Herein, we investigated the effects of physiological hypoxia on fibroblast-to-myofibroblast transition and the biological function and mechanism of CD9 in it.

METHODS

Human skin fibroblasts (HSF) and mouse dermis wounds model were established under physiological hypoxia (2% O2). The cell viability and contractility of HSF under hypoxia were evaluated by CCK8 and collagen gel retraction, respectively. The expression and distribution of fibroblast-to-myofibroblast transition markers and CD9 in HSF were detected by Western blotting and immunofluorescence. CD9 slicing and overexpressing HSFs were constructed to determine the role of CD9 by small interfering RNA and recombinant adenovirus vector. The association of TβR2 and TβR1 was measured by immunoprecipitation to explore the regulatory mechanism. Additionally, further validation was conducted on mouse dermis wounds model through histological analysis.

RESULTS

Enhanced fibroblast-to-myofibroblast transition and upregulated CD9 expression was observed under hypoxia in vitro and in vivo. Besides, reversal of fibroblast-to-myofibroblast transition under hypoxia was observed when silencing CD9, suggesting that CD9 played a key role in this hypoxia-induced transition. Moreover, hypoxia increased fibroblast-to-myofibroblast transition by activating TGF-β1/Smad2/3 signaling, especially increased interaction of TβR2 and TβR1. Ultimately, CD9 was determined to directly affect TβR1-TβR2 association in hypoxic fibroblast.

CONCLUSION

Collectively, these findings suggest that CD9 promotes TβR2-TβR1 association, thus driving the transition of human dermal fibroblasts to myofibroblast under hypoxia.

Tick extracellular vesicles undermine epidermal wound healing during hematophagy

Wound healing has been extensively studied through the lens of inflammatory disorders and cancer, but limited attention has been given to hematophagy and arthropod-borne diseases. Hematophagous ectoparasites, including ticks, subvert the wound healing response to maintain prolonged attachment and facilitate blood-feeding. Here, we unveil a strategy by which extracellular vesicles (EVs) ensure blood-feeding and arthropod survival in three medically relevant tick species. We demonstrate through single cell RNA sequencing and murine genetics that wildtype animals infested with EV-deficient Ixodes scapularis display a unique population of keratinocytes with an overrepresentation of pathways connected to wound healing. Tick feeding affected keratinocyte proliferation in a density-dependent manner, which relied on EVs and dendritic epidermal T cells (DETCs). This occurrence was linked to phosphoinositide 3-kinase activity, keratinocyte growth factor (KGF) and transforming growth factor β (TGF-β) levels. Collectively, we uncovered a strategy employed by a blood-feeding arthropod that impairs the integrity of the epithelial barrier, contributing to ectoparasite fitness.

Deciphering the Dysregulating IGF-1-SP1-CD248 Pathway in Fibroblast Functionality during Diabetic Wound Healing

Reduced fibroblast activity is a critical factor in the progression of diabetic ulcers. CD248, a transmembrane glycoprotein prominently expressed in activated fibroblasts, plays a pivotal role in wound healing. However, the role of CD248 in diabetic wound healing and the CD248 regulatory pathway remains largely unexplored. Our study shows that CD248 expression is significantly reduced in skin wounds from both patients and mice with diabetes. Single-cell transcriptome data analyses reveal a marked reduction of CD248-enriched secretory-reticular fibroblasts in diabetic wounds. We identify IGF-1 as a key regulator of CD248 expression through the protein kinase B/mTOR signaling pathway and the SP1 transcription factor. Overexpression of CD248 enhances fibroblast motility, elucidating the under-representation of CD248-enriched fibroblasts in diabetic wounds. Immunohistochemical staining of diabetic wound samples further confirms low SP1 expression and fewer CD248-positive secretory-reticular fibroblasts. Further investigation reveals that elevated TNFα levels in diabetic environment promotes IGF-1 resistance, and inhibiting IGF-1 induced CD248 expression. In summary, our findings underscore the critical role of the IGF1-SP1-CD248 axis in activating reticular fibroblasts during wound-healing processes. Targeting this axis in fibroblasts could help develop a therapeutic regimen for diabetic ulcers.

Flavonoid compounds and their synergistic effects: Promising approaches for the prevention and treatment of psoriasis with emphasis on keratinocytes - A systematic and mechanistic review

Psoriasis, a chronic autoimmune skin disorder, causes rapid and excessive skin cell growth due to immune system dysfunction. Numerous studies have shown that flavonoids have anti-psoriatic effects by modulating various molecular mechanisms involved in inflammation, cytokine production, keratinocyte proliferation, and more. This study reviewed experimental data reported in scientific literature and used network analysis to identify the potential biological roles of flavonoids' targets in treating psoriasis. 947 records from Web of Sciences, ScienceDirect database, Scopus, PubMed, and Cochrane library were reviewed without limitations until June 26, 2023. 66 articles were included in the systematic review. The ten genes with the highest scores, including interleukin (IL)-10, IL-12A, IL-1β, IL-6, Tumor necrosis factor-α (TNF-α), Janus kinase 2 (JAK 2), Jun N-terminal kinase (JUN), Proto-oncogene tyrosine-protein kinase Src (SRC), Phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit alpha (PIK3CA), and Signal transducer and activator of transcription 3 (STAT3), were identified as the hub genes. KEGG pathway analysis identified connections related to inflammation and autoimmune responses, which are key characteristics of psoriasis. IL-6, STAT3, and JUN's presence in both hub and enrichment genes suggests their important role in flavonoid's effect on psoriasis. This comprehensive study highlights how flavonoids can target biological processes in psoriasis, especially when combined for enhanced effectiveness.

Inhibition of Let-7b-5p maturation by LIN28A promotes thermal skin damage repair after burn injury

Burn injuries, especially severe ones, result in direct and indirect thermal damage to skin tissues, with a complex and slow wound healing process. Improper treatment can induce sustained inflammatory responses, causing systemic damage. Lin28A, a highly conserved RNA binding protein, was found to exert a significant effect on cell proliferation and wound repair. Lin28A exerts the functions through inhibiting the maturation of the let-7 family miRNAs. Herein, the roles of Lin28A and let-7b in thermal injury repair were investigated using a mouse thermal injury model and a human skin fibroblast (HSF) model for thermal injuries. Lin28A could inhibit the maturation of let-7b, thus participating in skin repair after burns. In the animal model, Lin28A was highly expressed after thermal injury. In the HSF model for thermal injuries, downregulation of Lin28A inhibited the proliferation, migration, and extracellular matrix (ECM) generation of fibroblasts. When let-7b was knocked down in HSFs, the impacts on fibroblast functions caused by downregulation of Lin28A were partially reversed. Moreover, let-7b overexpression might significantly attenuate the promotive effects of Lin28A upon thermal injury repair. Finally, AKT2 and IGF1R were the let-7b target genes within cells. These findings reveal that Lin28A might promote thermal injury repair in burn-injured skin by inhibiting the maturation of let-7b and improving HSF viability and functions, thus illustrating the critical effect of let-7b on burn wound healing and providing new therapeutic targets and strategies for burn treatment.

Foam dressing and micropower vacuum dressing promote diabetic foot ulcer wound healing by activating the PI3K/AKT/mTOR pathway in rats

Foam dressing (FD) and micropower vacuum dressing (MVD) have been applied in the treatment of diabetic foot ulcer (DFU). However, research about the mode of action on the efficacy of the two dressings is extremely rare. This study proposed to explore the mechanism involved in diabetic wound healing under FD or MVD treatment. Macroscopical study was performed to evaluate the effectiveness of FD and MVD on wound healing in a rat model of DFU. Morphological analysis in the wound skin tissue was conducted by hematoxylin and eosin staining. Meanwhile, inflammatory cytokines in serum were measured by enzyme linked immunosorbent assay. The protein expression of phosphatidylinositol 3 kinase, protein kinase B and mammalian target of rapamycin (PI3K/AKT/mTOR) and their phosphorylation levels were determined by western blotting. We found that wound healing in rats with DFU was enhanced with the application of FD and MVD. The therapeutic efficacy of FD was superior to MVD. Compared with diabetic foot group, the concentrations of inflammatory cytokines, tumor necrosis factor alpha, interleukin-1β and interleukin-6, were significantly down-regulated. Besides, the phosphorylation levels of PI3K, AKT and mTOR were up-regulated under FD or MVD treatment. We demonstrated that the treatment of FD and MVD effectively promoted the wound skin healing through activating the PI3K/AKT/mTOR pathway. Our research may provide a new idea for exploring the mode of action of dressing application in healing of DFU.

Temporal and differential proteomic profile of molecular mediators associated with chronic and acute wound healing

The underlying pathophysiology of nonhealing chronic wounds is poorly understood due to the changes occurring at the gene level and the complexity arising in their proteomic profile. Here, we elucidated the temporal and differential profile of the normal and diabetic wound-healing mediators along with their interactions and associated pathways. Skin tissues corresponding to normal and diabetic wounds were isolated at Days 0, 3, 6, and 9 representing different healing phases. Temporal gene expression was analyzed by quantitative real-time PCR. Concurrently, differential protein patterns in the wound tissues were identified by Nano LC-ESI-TOF mass spectrometry and later confirmed by Western blot analysis. Gene ontology annotation, protein-protein interaction, and protein pathway analysis were performed using DAVID, PANTHER, and STRING bioinformatics resources. Uniquely identified proteins (complement C3, amyloid beta precursor protein, and cytoplasmic linker associated protein 2) in the diabetic wound tissue implied that these proteins are involved in the pathogenesis of diabetic wound. They exhibit enhanced catalytic activity, trigger pathways linked with inflammation, and negatively regulate wound healing. However, in the normal wound tissue, axin 1, chondroitin sulfate proteoglycan 4, and sphingosine-1-phosphate receptor were identified, which are involved in proliferation, angiogenesis, and remodeling. Our findings demonstrate the correlation between elevated gene expression of tumor necrosis factor-α, interleukin (IL)-1β, and identified mediators: aryl hydrocarbon receptor nuclear translocator, 5'-aminolevulinate synthase 2, and CXC-family, that inflicted an inflammatory response by activating downstream MAPK, JAK-STAT, and NF-κB pathways. Similarly, in normal wound tissue, the upregulated IL-4 and hepatocyte growth factor levels in conjunction with the identified proteins, serine/threonine-protein kinase mTOR and peroxisome proliferator-activated receptor gamma, played a significant role in the cellular response to platelet-derived growth factor stimulus, dermal epithelialization, and cell proliferation, processes associated with the repair mechanism. Furthermore, Western blot analysis indicated elevated levels of inflammatory markers and reduced levels of proliferative and angiogenic factors in the diabetic wound.

Extracellular vesicles modulate key signalling pathways in refractory wound healing

Chronic wounds are wounds that cannot heal properly due to various factors, such as underlying diseases, infection or reinjury, and improper healing of skin wounds and ulcers can cause a serious economic burden. Numerous studies have shown that extracellular vesicles (EVs) derived from stem/progenitor cells promote wound healing, reduce scar formation and have significant advantages over traditional treatment methods. EVs are membranous particles that carry various bioactive molecules from their cellular origins, such as cytokines, nucleic acids, enzymes, lipids and proteins. EVs can mediate cell-to-cell communication and modulate various physiological processes, such as cell differentiation, angiogenesis, immune response and tissue remodelling. In this review, we summarize the recent advances in EV-based wound healing, focusing on the signalling pathways that are regulated by EVs and their cargos. We discuss how EVs derived from different types of stem/progenitor cells can promote wound healing and reduce scar formation by modulating the Wnt/β-catenin, phosphoinositide 3-kinase/protein kinase B/mammalian target of rapamycin, vascular endothelial growth factor, transforming growth factor β and JAK-STAT pathways. Moreover, we also highlight the challenges and opportunities for engineering or modifying EVs to enhance their efficacy and specificity for wound healing.

Regulatory T cells in skin regeneration and wound healing

As the body's integumentary system, the skin is vulnerable to injuries. The subsequent wound healing processes aim to restore dermal and epidermal integrity and functionality. To this end, multiple tissue-resident cells and recruited immune cells cooperate to efficiently repair the injured tissue. Such temporally- and spatially-coordinated interplay necessitates tight regulation to prevent collateral damage such as overshooting immune responses and excessive inflammation. In this context, regulatory T cells (Tregs) hold a key role in balancing immune homeostasis and mediating cutaneous wound healing. A comprehensive understanding of Tregs' multifaceted field of activity may help decipher wound pathologies and, ultimately, establish new treatment modalities. Herein, we review the role of Tregs in orchestrating the regeneration of skin adnexa and catalyzing healthy wound repair. Further, we discuss how Tregs operate during fibrosis, keloidosis, and scarring.

Proteomic Analysis of Mesenchymal Stromal Cells Secretome in Comparison to Leukocyte- and Platelet-Rich Fibrin

Secretomes of mesenchymal stromal cells (MSCs) are emerging as a novel growth factor (GF)-based strategy for periodontal and bone regeneration. The objective of this study was to compare the secretome of human bone marrow MSC (BMSC) to that of leukocyte- and platelet-rich fibrin (L-PRF), an established GF-based therapy, in the context of wound healing and regeneration. Conditioned media from human BMSCs (BMSC-CM) and L-PRF (LPRF-CM) were subjected to quantitative proteomic analysis using liquid chromatography with tandem mass spectrometry. Global profiles, gene ontology (GO) categories, differentially expressed proteins (DEPs), and gene set enrichment (GSEA) were identified using bioinformatic methods. Concentrations of selected proteins were determined using a multiplex immunoassay. Among the proteins identified in BMSC-CM (2157 proteins) and LPRF-CM (1420 proteins), 1283 proteins were common. GO analysis revealed similarities between the groups in terms of biological processes (cellular organization, protein metabolism) and molecular functions (cellular/protein-binding). Notably, more DEPs were identified in BMSC-CM (n = 550) compared to LPRF-CM (n = 118); these included several key GF, cytokines, and extracellular matrix (ECM) proteins involved in wound healing. GSEA revealed enrichment of ECM (especially bone ECM)-related processes in BMSC-CM and immune-related processes in LPRF-CM. Similar trends for intergroup differences in protein detection were observed in the multiplex analysis. Thus, the secretome of BMSC is enriched for proteins/processes relevant for periodontal and bone regeneration. The in vivo efficacy of this therapy should be evaluated in future studies.

Natural exosome-like nanoparticles derived from ancient medicinal insect Periplaneta americana L. as a novel diabetic wound healing accelerator

Along with the recognized therapeutic outcomes of regenerative medicine, extracellular vesicles and their exosome subsets have become an alternative option for wound healing. Periplaneta americana L. (PA), an ancient and traditional medicinal insect, has been around for 300 million years, and displays magic formidable vitality and environmental adaptive ability. The linkage between intrinsic amputation regeneration feature and the acknowledged wound healing medicinal benefit of PA has never been revealed. Herein, inspired by the ability of exosomes to participate in the interkingdom communication, we explored whether this effect was ascribed to PA derived exosome-like nanoparticles (PA-ELNs). PA-ELNs were extracted by differential velocity centrifugation approach and characterized by DLS, NTA and TEM. Their cargoes were analyzed by LC-MS/MS proteomics and small RNA-seq analysis. The wound healing activity was verified in vivo and in vitro. PA-ELNs with a concentration of 2.33x10⁹±6.35x10⁷ particles/mL exhibited a lipid bilayer-bound membrane structure with an average size of 104.7 nm. Furthermore, the miRNA cargoes in PA-ELNs participate in some wound healing related signal pathways such as TGF-beta, mTOR, and autophagy. As expected, the in vitro tests indicated that PA-ELNs were apt to be internalized in HUVECs, L929 and RAW 264.7 cells and contributed to cell proliferation and migration. Most importantly, we demonstrated that the topical administration of PA-ELNs could remarkably accelerate wound healing in a diabetic mouse model, and was involved in anti-inflammatory, re-epithelialization and autophagy regulation. This study provides clear evidence for the first time that PA-ELNs, as diabetic wound healing accelerators, are the "bioactive code" of this ancient medicinal insect.

Activation of Sestrin2 accelerates deep second-degree burn wound healing through PI3K/AKT pathway

Deep second-degree burns heal slowly, and promoting the healing process is a focus of clinical research. Sestrin2 is a stress-inducible protein with antioxidant and metabolic regulatory effects. However, its role during acute dermal and epidermal re-epithelialization in deep second-degree burns is unknown. In this study, we aimed to explore the role and molecular mechanism of sestrin2 in deep second-degree burns as a potential treatment target for burn wounds. To explore the effects of sestrin2 on burn wound healing, we established a deep second-degree burn mouse model. Then we detected the expression of sestrin2 by western blot and immunohistochemistry after obtaining the wound margin of full-thickness burned skin. The effects of sestrin2 on burn wound healing were explored in vivo and in vitro through interfering sestrin2 expression using siRNAs or the small molecule agonist of sestrin2, eupatilin. We also investigated the molecular mechanism of sestrin2 in promoting burn wound healing by western blot and CCK-8 assay. Our in vivo and in vitro deep second-degree burn wound healing model demonstrated that sestrin2 was promptly induced at murine skin wound edges. The small molecule agonist of sestrin2 accelerated the proliferation and migration of keratinocytes, as well as burn wound healing. Conversely, the healing of burn wounds was delayed in sestrin2-deficient mice and was accompanied by the secretion of inflammatory cytokines as well as the suppression of keratinocyte proliferation and migration. Mechanistically, sestrin2 promoted the phosphorylation of the PI3K/AKT pathway, and inhibition of PI3K/AKT pathway abrogated the promoting role of sestrin2 in keratinocyte proliferation and migration. Therefore, sestrin2 plays a critical role in activation of the PI3K/AKT pathway to promote keratinocyte proliferation and migration, as well as re-epithelialization in the process of deep second-degree burn wound repair.

Corylin accelerated wound healing through SIRT1 and PI3K/AKT signaling: a candidate remedy for chronic non-healing wounds

Introduction: Chronic non-healing wound is a considerable clinical challenge and research into the discovery of novel pro-healing agents is underway as existing therapeutic approaches cannot sufficiently meet current needs. Method: We studied the effects of corylin in cell line fibroblasts and macrophages by Western blots, PCR, Flow cytometry assay, Immunofluorescence. Results: We showed that corylin, a main flavonoid extracted from Psoralea corylifolia L, reduced inflammatory responses, promoted collagen deposition, and accelerated the healing of full-thickness skin wounds in mice. Exploration of the underlying mechanisms showed that corylin activated the PI3K/AKT signaling, leading to fibroblasts' migration, proliferation, and scratch healing. Corylin also activated sirtuin 1 (SIRT1) signaling, enhanced the deacetylation and cytoplasmic translocation of NF-κB p65, and therefore reduced lipopolysaccharide (LPS)-induced inflammatory responses in macrophages. Furthermore, inhibition of PI3K/AKT and sirtuin 1 pathway with LY294002 and EX527 prevent the therapeutic potency of corylin against chronic wounds. Conclusion: In summary, our results suggested that corylin may be a candidate for the development of novel pro-healing agents.

Metformin coordinates with mesenchymal cells to promote VEGF-mediated angiogenesis in diabetic wound healing through Akt/mTOR activation

INTRODUCTION

Cell therapy with mesenchymal stem cells (MSCs) and biomaterials holds great potential for the treatment of diabetic ulceration; however, the underlying mechanism as well as its compatibility with the first-line anti-diabetic drug, metformin (MTF), has not been well elucidated.

METHODS

MSCs derived from the umbilical cord were labeled with fluorescent proteins, followed by transplantation in a fibrin scaffold (MSCs/FG) onto the STZ-induced diabetic wound in a C57BL6/J mouse model. MTF was administered by oral gavage at a dose of 250 mg/kg/day. The wound healing rate, epithelization, angiogenesis, and underlying mechanism were evaluated in MSCs/FG- and MTF-treated diabetic wounds. Moreover, the dose-dependent effects of MTF and involvement of the Akt/mTOR pathway were analyzed in keratinocyte and fibroblast cultures.

RESULTS

MSCs/FG significantly promoted angiogenesis in diabetic wound healing without signs of differentiation or integration. The recruitment of fibroblasts and keratinocytes by MSCs/FG promotes migration and vascular endothelial growth factor (VEGF) expression in an Akt/mTOR-dependent manner. MTF, which is generally considered a mTOR inhibitor, displayed dose-dependent effects on MSC-unregulated Akt/mTOR and VEGF expression. Oral administration of MTF at an anti-diabetic dosage synergistically acted with MSCs/FG to promote Akt/mTOR activation, VEGF expression, and subsequent angiogenesis in diabetic wounds; however, it reduced the survival of MSCs.

CONCLUSIONS

Our study identifies that MTF coordinates with mesenchymal cells to promote Akt/mTOR activation and VEGF-mediated angiogenesis during diabetic wound healing. These findings offer new insights into MSCs engraftment in FG scaffolds for diabetic wound healing and provide support for the promotion of MSCs therapy in patients prescribed with MTF.

Bioactive Nonthermal Biocompatible Plasma Enhances Migration on Human Gingival Fibroblasts

This study hypothesizes that the application of low-dose nonthermal biocompatible dielectric barrier discharge plasma (DBD-NBP) to human gingival fibroblasts (HGFs) will inhibit colony formation but not cell death and induce matrix metalloproteinase (MMP) expression, extracellular matrix (ECM) degradation, and subsequent cell migration, which can result in enhanced wound healing. HGFs treated with plasma for 3 min migrate to each other across the gap faster than those in the control and 5-min treatment groups on days 1 and 3. The plasma-treated HGFs show significantly high expression levels of the cell cycle arrest-related p21 gene and enhanced MMP activity. Focal adhesion kinase (FAK) mediated attenuation of wound healing or actin cytoskeleton rearrangement, and plasma-mediated reversal of this attenuation support the migratory effect of DBD-NBP. Further, this work performs computer simulations to investigate the effect of oxidation on the stability and conformation of the catalytic kinase domain (KD) of FAK. It is found that the oxidation of highly reactive amino acids (AAs) Cys427, Met442, Cys559, Met571, Met617, and Met643 changes the conformation and increases the structural flexibility of the FAK protein and thus modulates its function and activity. Low-dose DBD-NBP-induces host cell cycle arrest, ECM breakdown, and subsequent migration, thus contributing to the enhanced wound healing process.

Statins block mammalian target of rapamycin pathway: a possible novel therapeutic strategy for inflammatory, malignant and neurodegenerative diseases

Inflammation plays a critical role in several diseases such as cancer, gastric, heart and nervous system diseases. Data suggest that the activation of mammalian target of rapamycin (mTOR) pathway in epithelial cells leads to inflammation. Statins, the inhibitors of the 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA), seem to be able to inhibit the mTOR. Statins are considered to have favorable effects on inflammatory diseases by reducing the complications caused by inflammation and by regulating the inflammatory process and cytokines secretion. This critical review collected data on this topic from clinical, in vivo and in vitro studies published between 1998 and June 2022 in English from databases including PubMed, Google Scholar, Scopus, and Cochrane libraries.

Porcine Acellular Dermal Matrix Promotes Migration and Suppresses Inflammation of Keratinocytes by Mediating the AKT Signaling Pathway

Porcine acellular dermal matrix (pADM) is known to accelerate wound healing. However, the underlying molecular mechanism remains unclear. This study aimed to investigate the effects of pADM on wound healing and its underlying mechanisms. HaCaT cells were treated with hydrogen peroxide (H2O2) or pADM, and the appropriate treatment concentration was determined using the cell counting kit-8 and flow cytometry. Cell migration was assessed using a Transwell assay and scratch test. Inflammation was evaluated using enzyme-linked immunosorbent assay. Western blotting was performed to measure the levels of protein kinase B (AKT) pathway-related proteins. The results showed that H2O2 inhibited cell viability and induced apoptosis in a dose-dependent manner. pADM promoted cell migration and decreased the levels of interleukin (IL)-6, IL-8, and tumor necrosis factor-α (TNF-α) in H2O2-treated HaCaT cells. Moreover, pADM rescued the downregulation of phosphorylated (p)-AKT and p-mechanistic target of rapamycin (mTOR) induced by H2O2. LY294002, a phosphatidylinositol 3-kinase (PI3K) inhibitor, abrogated migration and anti-inflammatory response caused by pADM. In conclusion, pADM promotes cell migration and inhibits inflammation by activating the AKT pathway under oxidative stress. These findings support the use of pADM for post-traumatic therapy and reveal a novel underlying mechanism of action.

Mesenchymal Stem Cells in Burn Wound Management

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

Neuronal-epithelial cross-talk drives acinar specification via NRG1-ERBB3-mTORC2 signaling

Acinar cells are the principal secretory units of multiple exocrine organs. A single-cell, layered, lumenized acinus forms from a large cohort of epithelial progenitors that must initiate and coordinate three cellular programs of acinar specification, namely, lineage progression, secretion, and polarization. Despite this well-known outcome, the mechanism(s) that regulate these complex programs are unknown. Here, we demonstrate that neuronal-epithelial cross-talk drives acinar specification through neuregulin (NRG1)-ERBB3-mTORC2 signaling. Using single-cell and global RNA sequencing of developing murine salivary glands, we identified NRG1-ERBB3 to precisely overlap with acinar specification during gland development. Genetic deletion of Erbb3 prevented cell lineage progression and the establishment of lumenized, secretory acini. Conversely, NRG1 treatment of isolated epithelia was sufficient to recapitulate the development of secretory acini. Mechanistically, we found that NRG1-ERBB3 regulates each developmental program through an mTORC2 signaling pathway. Thus, we reveal that a neuronal-epithelial (NRG1/ERBB3/mTORC2) mechanism orchestrates the creation of functional acini.

Mechanotransduction in skin wound healing and scar formation: Potential therapeutic targets for controlling hypertrophic scarring

Hypertrophic scarring (HTS) is a major source of morbidity after cutaneous injury. Recent studies indicate that mechanical force significantly impacts wound healing and skin regeneration which opens up a new direction to combat scarring. Hence, a thorough understanding of the underlying mechanisms is essential in the development of efficacious scar therapeutics. This review provides an overview of the current understanding of the mechanotransduction signaling pathways in scar formation and some strategies that offload mechanical forces in the wounded region for scar prevention and treatment.

P311 promotes type II transforming growth factor-β receptor mediated fibroblast activation and granulation tissue formation in wound healing

Background

P311, a highly conserved 8 kDa intracellular protein, has recently been reported to play an important role in aggravating hypertrophic scaring by promoting the differentiation and secretion of fibroblasts. Nevertheless, how P311 regulates the differentiation and function of fibroblasts to affect granulation tissue formation remains unclear. In this work, we studied the underlying mechanisms via which P311 affects fibroblasts and promotes acute skin wound repair.

Methods

To explore the role of P311, both in vitro and in vivo wound-healing models were used. Full-thickness skin excisional wounds were made in wild-type and P311^-/- C57 adult mice. Wound healing rate, re-epithelialization, granulation tissue formation and collagen deposition were measured at days 3, 6 and 9 after skin injury. The biological phenotypes of fibroblasts, the expression of target proteins and relevant signaling pathways were examined both in vitro and in vivo.

Results

P311 could promote the proliferation and differentiation of fibroblasts, enhance the ability of myofibroblasts to secrete extracellular matrix and promote cell contraction, and then facilitate the formation of granulation tissue and eventually accelerate skin wound closure. Importantly, we discovered that P311 acts via up-regulating the expression of type II transforming growth factor-β receptor (TGF-βRII) in fibroblasts and promoting the activation of the TGF-βRII-Smad signaling pathway. Mechanistically, the mammalian target of rapamycin signaling pathway is closely implicated in the regulation of the TGF-βRII-Smad pathway in fibroblasts mediated by P311.

Conclusions

P311 plays a critical role in activation of the TGF-βRII-Smad pathway to promote fibroblast proliferation and differentiation as well as granulation tissue formation in the process of skin wound repair.

Longevity-Promoting Pathways and Transcription Factors Respond to and Control Extracellular Matrix Dynamics During Aging and Disease

Aging is one of the largest risk factors for cancer, type 2 diabetes, osteoarthritis, cardiovascular diseases, and other age-related pathologies. Here, we give a detailed description of the interplay of chronic age-related pathologies with the remodeling of the extracellular matrix during disease development and progression. Longevity-promoting signaling pathways slow or prevent age-related diseases. In particular, we focus on the mTOR signaling pathway, sirtuins, and canonical longevity-promoting transcription factors, such as FOXO, NF-κB, and Nrf2. We extend our analysis using chromatin immunoprecipitation (ChIP) sequencing and transcriptomic data and report that many established and emerging longevity-promoting transcription factors, such as CREB1, FOXO1,3, GATA1,2,3,4, HIF1A, JUN, KLF4, MYC, NFE2L2/Nrf2, RELA/NF-κB, REST, STAT3,5A, and TP53/p53, directly regulate many extracellular matrix genes and remodelers. We propose that modulation of these pathways increases lifespan and protects from age-related diseases in part due to their effects on extracellular matrix remodeling. Therefore, to successfully treat age-related diseases, it is necessary to better understand the connection between extracellular matrix components and longevity pathways.

Ropivacaine inhibits wound healing by suppressing the proliferation and migration of keratinocytes via the PI3K/AKT/mTOR Pathway

Background

After surgery, millions of people suffer from delayed healing or wound dehiscence with subsequent severe complications, even death. Previous studies have reported that ropivacaine exhibits anti-proliferative and anti-migratory activities on numerous cells. Whether ropivacaine is able to influence the proliferation and migration of keratinocytes is still unclear. This study aimed to investigate the effect of ropivacaine on keratinocytes and its underlying molecular mechanism.

Methods

Adult male Sprague–Dawley rats were allocated to establish wound healing models with or without 0.75% ropivacaine treatment and assessed the epidermal thickness by HE staining. HaCaT cells were cultured to evaluate the effect of ropivacaine on wound healing. The cell proliferation, apoptosis status and migration were detected in vitro. Moreover, western blotting was used to examine expression to with PI3K/AKT/mTOR signaling pathways for molecular studies and the changes in inflammatory factors (IL-6, IL-10, TNF-α) were detected by ELISA.

Results

In the present study, we found that ropivacaine delayed wound closure in vivo. In vitro experiments, it was demonstrated that ropivacaine significantly inhibited the proliferation and migration of HaCaT cells via the suppression of PI3K/AKT/mTOR signaling pathway. Activation of PI3K/AKT/mTOR signaling pathway reversed the effects of ropivacaine on the proliferation and migration of HaCaT cells. Furthermore, ropivacaine contributed to the release of pro-inflammatory cytokines (IL-6 and TNF-α) and inhibited the secretion of anti-inflammatory cytokines of keratinocytes (IL-10).

Conclusions

Our research demonstrated that ropivacaine treatment showed a more decreased wound closure rate. Mechanistically, we found that ropivacaine suppressed the proliferation and migration of keratinocytes and altered the expression of cytokines by inhibiting PI3K/AKT/mTOR pathway.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12871-022-01646-0.

Engineering microparticles based on solidified stem cell secretome with an augmented pro-angiogenic factor portfolio for therapeutic angiogenesis

Tissue (re)vascularization strategies face various challenges, as therapeutic cells do not survive long enough in situ, while the administration of pro-angiogenic factors is hampered by fast clearance and insufficient ability to emulate complex spatiotemporal signaling. Here, we propose to address these limitations by engineering a functional biomaterial capable of capturing and concentrating the pro-angiogenic activities of mesenchymal stem cells (MSCs).

In particular, dextran sulfate, a high molecular weight sulfated glucose polymer, supplemented to MSC cultures, interacts with MSC-derived extracellular matrix (ECM) components and facilitates their co-assembly and accumulation in the pericellular space. Upon decellularization, the resulting dextran sulfate-ECM hybrid material can be processed into MIcroparticles of SOlidified Secretome (MIPSOS). The insoluble format of MIPSOS protects protein components from degradation, while facilitating their sustained release. Proteomic analysis demonstrates that MIPSOS are highly enriched in pro-angiogenic factors, resulting in an enhanced pro-angiogenic bioactivity when compared to naïve MSC-derived ECM (cECM). Consequently, intravital microscopy of full-thickness skin wounds treated with MIPSOS demonstrates accelerated revascularization and healing, far superior to the therapeutic potential of cECM. Hence, the microparticle-based solidified stem cell secretome provides a promising platform to address major limitations of current therapeutic angiogenesis approaches.

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Dextran sulfate assembles with mesenchymal stem cell secretome.

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As a result, microparticles of solidified stem cell secretome (MIPSOS) are formed.

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The insoluble MIPSOS format protects proteins from premature degradation.

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MIPSOS are enriched in pro-angiogenic factors and exhibit gradual release kinetics.

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MIPSOS demonstrate superior pro-angiogenic properties and thus therapeutic potential.

Urolithin A Promotes Angiogenesis and Tissue Regeneration in a Full-Thickness Cutaneous Wound Model

The treatment of chronic wound is an important topic of current clinical issue. Neovascularization plays a crucial role in skin wound healing by delivering fresh nutrients and oxygen to the wound area. The aim of this study was to investigate the mechanisms of urolithin A (UA) in angiogenesis during wound healing. The results of in vitro experiments showed that treatment with UA (5–20 μM) promoted the proliferation, migration, and angiogenic capacity of HUVECs. Furthermore, we investigated the effect of UA in vivo using a full-thickness skin wound model. Subsequently, we found that UA promoted the regeneration of new blood vessels, which is consistent with the results of accelerated angiogenesis in vitro experiments. After UA treatment, the blood vessels in the wound are rapidly formed, and the deposition and remodeling process of the collagen matrix is also accelerated, which ultimately promotes the effective wound healing. Mechanistic studies have shown that UA promotes angiogenesis by inhibiting the PI3K/AKT pathway. Our study provides evidence that UA can promote angiogenesis and skin regeneration in chronic wounds, especially ischemic wounds.

Accelerated Wound Healing and Keratinocyte Proliferation through PI3K/Akt/pS6 and VEGFR2 Signaling by Topical Use of Pleural Fluid

Impaired wound healing is an ongoing issue that cancer patients undergoing chemotherapy or radiotherapy face. Our previous study regarding lung-cancer-associated pleural fluid (LCPF) demonstrated its propensity to promote endothelial proliferation, migration, and angiogenesis, which are crucial features during cutaneous wound healing. Therefore, the current study aimed to investigate the effect of pleural fluid on cutaneous wound closure in vitro and in vivo using HaCaT keratinocytes and a full-thickness skin wound model, respectively. Both heart-failure-associated pleural fluid (HFPF) and LCPF were sequentially centrifuged and filtered to obtain a cell-free status. Treatment with HFPF and LCPF homogeneously induced HaCaT proliferation with cell cycle progression, migration, and MMP2 upregulation. Western blotting revealed increased PI3K/Akt phosphorylation and VEGFR2/VEGFA expression in HaCaT cells. When treated with the PI3K inhibitor, LCPF-induced keratinocyte proliferation was attenuated with decreased pS6 levels. By applying the VEGFR2 inhibitor, LCPF-induced keratinocyte proliferation was ameliorated by pS6 and MMP2 downregulation. The effect of LCPF-induced cell junction rearrangement was disrupted by co-treatment with a VEGFR2 inhibitor. Compared with a 0.9% saline dressing, LCPF significantly accelerated wound closure and re-epithelization when used as a dressing material in a full-thickness wound model. Histological analysis revealed increased neo-epidermis thickness and dermis collagen synthesis in the LCPF-treated group. Furthermore, LCPF treatment activated basal keratinocytes at the wound edge with the upregulation of Ki-67, VEGFA, and MMP2. Our preliminaries provided the benefit of wet dressing with pleural fluid to improve cutaneous wound closure through enhanced re-epithelization and disclosed future autologous application in cancer wound treatment.

Logical and experimental modeling of cytokine and eicosanoid signaling in psoriatic keratinocytes

Psoriasis is a chronic skin disease, in which immune cells and keratinocytes keep each other in a state of inflammation. It is believed that phospholipase A2 (PLA2)-dependent eicosanoid release plays a key role in this. T-helper (Th) 1-derived cytokines are established activators of phospholipases in keratinocytes, whereas Th17-derived cytokines have largely unknown effects. Logical model simulations describing the function of cytokine and eicosanoid signaling networks combined with experimental data suggest that Th17 cytokines stimulate proinflammatory cytokine expression in psoriatic keratinocytes via activation of cPLA2α-Prostaglandin E2-EP4 signaling, which could be suppressed using the anti-psoriatic calcipotriol. cPLA2α inhibition and calcipotriol distinctly regulate expression of key psoriatic genes, possibly offering therapeutic advantage when applied together. Model simulations additionally suggest EP4 and protein kinase cAMP-activated catalytic subunit alpha as drug targets that may restore a normal phenotype. Our work illustrates how the study of complex diseases can benefit from an integrated systems approach.

Comparative study of royal jelly, propolis, and photobiomodulation therapies in 5-fluorouracil-related oral mucositis in rats

PURPOSE

This study aimed to evaluate the effects and mechanisms of action of royal jelly (RJ) and propolis compared to photobiomodulation therapy (PBMT) in an animal model of 5-fluorouracil-related oral mucositis (OM).

METHODS

Seventy-two male Wistar rats were randomly allocated to four groups (n = 18 each): control (no treatment), PBMT (intraoral laser, 6 J/cm²), RJ, and propolis. On days 0 and 2, the animals received an injection of 5-fluorouracil (5-FU). The buccal mucosa was scratched (days 3 and 4) and the treatments were initiated on day 5. Six animals of each group were euthanized on days 8, 10, and 14. Phytochemical analysis (thin-layer chromatography, TLC) and clinical, histopathological, and immunohistochemical analysis of pS6, pAKT, and NF-κB were performed, and oxidative stress markers were also investigated.

RESULTS

TLC revealed the presence of large amounts of sucrose (Rf 0.34) in RJ and of flavonoids in propolis. Lower clinical OM scores were observed on day 8, and improved morphological data were observed on day 10 in the PBMT, RJ, and propolis groups (p < 0.05). On day 8, immunoexpression of pS6, pAKT, and NF-κB was increased compared to control. On day 14, reduced glutathione (GSH) antioxidant levels were increased in the propolis group compared to control (p < 0.05).

CONCLUSIONS

Our results showed that RJ and propolis, as well as PBMT, are effective in the treatment of OM. Considering that some patients who develop OM do not have access to PBMT, the present study demonstrated that topical application of RJ and propolis may be an important alternative for the treatment of OM.

Curcuma longa L. Effects on Akt/mTOR Pathway and NF-κB Expression During Skin Wound Healing: An Immunohistochemical Study

Skin ulcers, wounds, or burns represent a burden for health care worldwide. Our aim was to explore the effects of mucoadhesive formulation with Curcuma longa L. extract mucoadhesive formulation containing curcumin (MFC) on skin healing in Wistar rats. Fifty-four rats were randomly allocated into 3 groups: control, vehicle, and MFC. A full-thickness circular wound was induced on the back of each animal. Two daily applications of the products were performed according to the experimental group. On days 3, 10, and 21, 6 animals in each group were euthanized. Clinical analysis was based on wound area. Histologic analysis was performed in hematoxylin and eosin-stained sections, with re-epithelization and inflammation being assessed by means of semiquantitative scores. To analyze the Akt/mTOR pathway, immunohistochemistry for phospho Akt (pAkt) and phospho ribosomal protein S6 were investigated. In addition, nuclear factor kappa-light-chain-enhancer of activated B cells immunolabeling was performed. Clinical analysis revealed wounds with a smaller area on days 3 and 10 in curcumin-treated animals. Histologically, MFC had a significant impact on inflammatory events on days 3 and 10 and promoted faster re-epithelization, which was evidenced on day 10. MFC-treated wounds exhibited pAkt upregulation on day 10 and both pAkt and phospho ribosomal protein S6 downregulation on day 21. Nuclear factor kappa-light-chain-enhancer of activated B cells expression varied through the evaluation periods; however, no significant difference was observed between groups. Collectively, our results indicate that MFC is efficient in accelerating cutaneous wound repair through modulation of the inflammatory process and stimulus of re-epithelization by an Akt/mTOR-dependent mechanism.

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.

SETD2 epidermal deficiency promotes cutaneous wound healing via activation of AKT/mTOR Signalling

Objectives

Cutaneous wound healing is one of the major medical problems worldwide. Epigenetic modifiers have been identified as important players in skin development, homeostasis and wound repair. SET domain–containing 2 (SETD2) is the only known histone H3K36 tri‐methylase; however, its role in skin wound healing remains unclear.

Materials and Methods

To elucidate the biological role of SETD2 in wound healing, conditional gene targeting was used to generate epidermis‐specific Setd2‐deficient mice. Wound‐healing experiments were performed on the backs of mice, and injured skin tissues were collected and analysed by haematoxylin and eosin (H&E) and immunohistochemical staining. In vitro, CCK8 and scratch wound‐healing assays were performed on Setd2‐knockdown and Setd2‐overexpression human immortalized keratinocyte cell line (HaCaT). In addition, RNA‐seq and H3K36me3 ChIP‐seq analyses were performed to identify the dysregulated genes modulated by SETD2. Finally, the results were validated in functional rescue experiments using AKT and mTOR inhibitors (MK2206 and rapamycin).

Results

Epidermis‐specific Setd2‐deficient mice were successfully established, and SETD2 deficiency resulted in accelerated re‐epithelialization during cutaneous wound healing by promoting keratinocyte proliferation and migration. Furthermore, the loss of SETD2 enhanced the scratch closure and proliferation of keratinocytes in vitro. Mechanistically, the deletion of Setd2 resulted in the activation of AKT/mTOR signalling pathway, while the pharmacological inhibition of AKT and mTOR with MK2206 and rapamycin, respectively, delayed wound closure.

Conclusions

Our results showed that SETD2 loss promoted cutaneous wound healing via the activation of AKT/mTOR signalling.

mTOR Signaling as a Regulator of Hematopoietic Stem Cell Fate

Blood is generated throughout life by continued proliferation and differentiation of hematopoietic progenitors, while at the top of the hierarchy, hematopoietic stem cells (HSCs) remain largely quiescent. This way HSCs avoid senescence and preserve their capacity to repopulate the hematopoietic system. But HSCs are not always quiescent, proliferating extensively in conditions such as those found in the fetal liver. Understanding the elusive mechanisms that regulate HSC fate would enable us to comprehend a crucial piece of HSC biology and pave the way for ex-vivo HSC expansion with clear clinical benefit. Here we review how metabolism, endoplasmic reticulum stress and oxidative stress condition impact HSCs decision to self-renew or differentiate and how these signals integrate into the mammalian target of rapamycin (mTOR) pathway. We argue that the bone marrow microenvironment continuously favors differentiation through the activation of the mTOR complex (mTORC)1 signaling, while the fetal liver microenvironment favors self-renewal through the inverse mechanism. In addition, we also postulate that strategies that have successfully achieved HSC expansion, directly or indirectly, lead to the inactivation of mTORC1. Finally, we propose a mechanism by which mTOR signaling, during cell division, conditions HSC fate. This mechanism has already been demonstrated in mature hematopoietic cells (T-cells), that face a similar decision after activation, either undergoing clonal expansion or differentiation.

Human amniotic mesenchymal stem cells to promote/suppress cancer: two sides of the same coin

Cancer is a leading cause of death in both developed and developing countries, and because of population growth and aging, it is a growing medical burden worldwide. With robust development in medicine, the use of stem cells has opened new treatment modalities in cancer therapy. In adult stem cells, mesenchymal stem cells (MSCs) are showing rising promise in cancer treatment due to their unique properties. Among different sources of MSCs, human amniotic fluid/membrane is an attractive and suitable reservoir. There are conflicting opinions about the role of human amniotic membrane/fluid mesenchymal stem cells (hAMSCS/hAFMSCs) in cancer, as some studies demonstrating the anticancer effects of these cells and others suggesting their progressive effects on cancer. This review focuses on recent findings about the role of hAMSCs/hAFMSCs in cancer treatment and summarizes the suppressing as well as promoting effects of these cells on cancer progression and underling mechanisms.

Photobiomodulation therapy drives massive epigenetic histone modifications, stem cells mobilization and accelerated epithelial healing

Emerging evidence indicates the clinical benefits of photobiomodulation therapy (PBMT) in the management of skin and mucosal wounds. Here, we decided to explore the effects of different regiments of PBMT on epithelial cells and stem cells, and the potential implications over the epigenetic circuitry during healing. Scratch-wound migration, immunofluorescence (anti-acetyl-Histone H3, anti-acetyl-CBP/p300 and anti-BMI1), nuclear morphometry and western blotting (anti-Phospho-S6, anti-methyl-CpG binding domain protein 2 [MBD2]) were performed. Epithelial stem cells were identified by the aldehyde dehydrogenase enzymatic levels and sphere-forming assay. We observed that PBMT-induced accelerated epithelial migration and chromatin relaxation along with increased levels of histones acetylation, the transcription cofactors CBP/p300 and mammalian target of rapamycin. We further observed a reduction of the transcription repression-associated protein MBD2 and a reduced number of epithelial stem cells and spheres. In this study, we showed that PBMT could induce epigenetic modifications of epithelial cells and control stem cell fate, leading to an accelerated healing phenotype.

Platelet-Rich Plasma Promotes the Proliferation of Human Keratinocytes via a Progression of the Cell Cycle. A Role of Prolidase

Although the role of platelet-rich plasma (PRP) in tissue regeneration has been confirmed in many studies, the mechanism of this process is still not fully understood. Human keratinocytes (HaCaT) cells were used as an experimental model for studies on the effects of PRP on cell proliferation, migration, collagen biosynthesis, prolidase activity, and its expression and anabolic signaling. The activation of epidermal growth factor receptor (EGFR), β₁-integrin, and insulin-like growth factor-1 receptor (IGF-1R) by PRP were investigated by western blot and immunocytochemistry. It has been found that PRP induced keratinocytes migration and proliferation through activation of cell cycle progression and EGFR downstream signaling. Similar biological effects were achieved by an addition to the culture medium of prolidase (PEPD), a ligand of EGFR (PRP is a rich source of PEPD–2 ng/mL). PRP-dependent stimulation of collagen biosynthesis was accompanied by an increase in the expression of NF-κβ, IGF-1R-downstream signaling proteins, and PEPD activity. The data suggest that PRP activates a complex of growth factors and adhesion receptors that stimulate cell proliferation, migration, and collagen biosynthesis. PRP induces PEPD-dependent human keratinocyte proliferation through activation of the EGFR receptor. Our study provides a novel mechanism of PRP-dependent wound healing.

Boesenbergia rotunda extract accelerates human keratinocyte proliferation through activating ERK1/2 and PI3K/Akt kinases

Boesenbergia rotunda (BR) has long been used as tradition medicine. For its pharmacological effects on wound healing, previous studies in an animal model provided convincing results that the ethanolic extract from the rhizome of this plant can stimulate wound healing. However, the mechanism about how this plant promotes wound healing at the molecular level has not been elucidated. As a step towards the development of wound healing agents, our current study utilized a human keratinocyte cell line (HaCaT) as an in vitro model to define the potential molecular mechanisms of BR extract in enhancing wound-healing. Our HPLC results showed that BR extract contained kaempferol as one of its potential compounds. The extract strongly promoted wound healing of HaCaT cell monolayer. This effect was eventually defined to be regulated through the ability of BR extract to induce cell proliferation. At the signaling level, we discovered that BR extract rapidly activated ERK1/2 and Akt phosphorylation upon the addition of the extract. Additionally, our experiments where specific inhibitors of MEK (U0126) and PI3K (LY294002) were utilized verified that BR enhanced cell proliferation and wound healing through stimulating the MAPK and PI3K/Akt signal transduction pathways. Moreover, direct inhibition of keratinocyte DNA synthesis by mitomycin C (MMC) could completely block the proliferative effects of BR extract. Nevertheless, data from Transwell migration assay revealed that BR extract did not promote keratinocyte migration. Altogether, we provided more evidence that BR possesses its wound healing-promoting action through the activation of proliferation and survival pathways, and our study suggests that BR is an interesting candidate to be developed as a wound healing-promoting agent.

Prolidase Stimulates Proliferation and Migration through Activation of the PI3K/Akt/mTOR Signaling Pathway in Human Keratinocytes

Recent reports have indicated prolidase (PEPD) as a ligand of the epidermal growth factor receptor (EGFR). Since this receptor is involved in the promotion of cell proliferation, growth, and migration, we aimed to investigate whether prolidase may participate in wound healing in vitro. All experiments were performed in prolidase-treated human keratinocytes assessing cell vitality, proliferation, and migration. The expression of downstream signaling proteins induced by EGFR, insulin-like growth factor 1 (IGF-1), transforming growth factor β₁ (TGF-β₁), and β₁-integrin receptors were evaluated by Western immunoblotting and immunocytochemical staining. To determine collagen biosynthesis and prolidase activity radiometric and colorimetric methods were used, respectively. Proline content was determined by applying the liquid chromatography coupled with mass spectrometry. We found that prolidase promoted the proliferation and migration of keratinocytes through stimulation of EGFR-downstream signaling pathways in which the PI3K/Akt/mTOR axis was involved. Moreover, PEPD upregulated the expression of β₁-integrin and IGF-1 receptors and their downstream proteins. Proline concentration and collagen biosynthesis were increased in HaCaT cells under prolidase treatment. Since extracellular prolidase as a ligand of EGFR induced cell growth, migration, and collagen biosynthesis in keratinocytes, it may represent a potential therapeutic approach for the treatment of skin wounds.

Magnetic targeting enhances the cutaneous wound healing effects of human mesenchymal stem cell-derived iron oxide exosomes

Human mesenchymal stem cell (MSC)-derived exosomes (Exos) are a promising therapeutic agent for cell-free regenerative medicine. However, their poor organ-targeting ability and therapeutic efficacy have been found to critically limit their clinical applications. In the present study, we fabricated iron oxide nanoparticle (NP)-labeled exosomes (Exo + NPs) from NP-treated MSCs and evaluated their therapeutic efficacy in a clinically relevant model of skin injury. We found that the Exos could be readily internalized by human umbilical vein endothelial cells (HUVECs), and could significantly promote their proliferation, migration, and angiogenesis both in vitro and in vivo. Moreover, the protein expression of proliferative markers (Cyclin D1 and Cyclin A2), growth factors (VEGFA), and migration-related chemokines (CXCL12) was significantly upregulated after Exo treatment. Unlike the Exos prepared from untreated MSCs, the Exo + NPs contained NPs that acted as a magnet-guided navigation tool. The in vivo systemic injection of Exo + NPs with magnetic guidance significantly increased the number of Exo + NPs that accumulated at the injury site. Furthermore, these accumulated Exo + NPs significantly enhanced endothelial cell proliferation, migration, and angiogenic tubule formation in vivo; moreover, they reduced scar formation and increased CK19, PCNA, and collagen expression in vivo. Collectively, these findings confirm the development of therapeutically efficacious extracellular nanovesicles and demonstrate their feasibility in cutaneous wound repair.

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.

Alda-1, an Aldehyde Dehydrogenase 2 Agonist, Improves Cutaneous Wound Healing by Activating Epidermal Keratinocytes via Akt/GSK-3β/β-Catenin Pathway

BACKGROUND

The cutaneous wound healing process mainly comprises re-epithelialization, fibrosis, and neovascularization. Impaired wound healing is common but tricky in plastic surgery. Aldehyde dehydrogenase 2 (ALDH2), the most effective subset of the ALDH enzyme family, is known to exert a major role in detoxification of aldehydes. Activation of ALDH2 by Alda-1 (a specific agonist) has been found to protect against cardiovascular diseases. However, no research has paid attention to the potential of ALDH2 activation in regulating wound healing. The previous studies suggested a high expression of ALDH2 in normal skin tissue. The aim of this study was to investigate if Alda-1 may ameliorate wound healing.

METHODS

A full-thickness excisional wound model was established in vivo. Adult male C57BL/6 mice were randomly divided into DMSO and Alda-1 groups. Mice received an intraperitoneal injection of DMSO or 10 mg/mL Alda-1 (10 mg/kg body weight, dissolved in DMSO) for 7 days. The wound healing rate was measured at 0, 3, 5, and 7 days. Distribution of ALDH2 in wound tissue was showed. ALDH2 enzymatic activity was examined at 3, 5, and 7 days. The elongation of epithelial tongue was detected by hematoxylin-eosin staining, and collagen deposition was analyzed by Masson's trichrome staining at 7 days. Expressions of alpha-smooth muscle actin (alpha-SMA), transforming growth factor beta (TGF-beta), CD31, collagen 1, collagen 3, and elastin were stained by immunohistochemistry at 5 and 7 days. The HaCaT cell line was applied in vitro. Proliferation and migration were tested using CCK8 and wound healing assay separately. The level of TGF-β was examined by ELISA. Protein levels of the Akt/glycogen synthase kinase-3 beta (GSK-3 beta)/beta-catenin pathway were determined by western blotting.

RESULTS

Alda-1 accelerated wound healing rates. ALDH2 activity in wound sites was restored. Alda-1 promoted the length of the epithelial tongue, collagen deposition, as well as expressions of alpha-SMA, TGF-beta, collagen 1/3, elastin, but did not affect CD31. Proliferation, migration, and TGF-β secretion were promoted by Alda-1 and deregulated by CVT-10216 (an ALDH2 inhibitor). Protein variations of the Akt/GSK-3β/β-catenin pathway were found to accord with ALDH2 changes.

CONCLUSIONS

Alda-1, an ALDH2 agonist, improves cutaneous wound healing in a full-thickness excisional wound model. Alda-1 activates proliferation, migration, and TGF-β secretion of HaCaT (epidermal keratinocytes) by regulating the Akt/GSK-3β/β-catenin pathway.

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mTOR Signaling at the Crossroad between Metazoan Regeneration and Human Diseases

A major challenge in medical research resides in controlling the molecular processes of tissue regeneration, as organ and structure damage are central to several human diseases. A survey of the literature reveals that mTOR (mechanistic/mammalian target of rapamycin) is involved in a wide range of regeneration mechanisms in the animal kingdom. More particularly, cellular processes such as growth, proliferation, and differentiation are controlled by mTOR. In addition, autophagy, stem cell maintenance or the newly described intermediate quiescence state, Galert, imply upstream monitoring by the mTOR pathway. In this review, we report the role of mTOR signaling in reparative regenerations in different tissues and body parts (e.g., axon, skeletal muscle, liver, epithelia, appendages, kidney, and whole-body), and highlight how the mTOR kinase can be viewed as a therapeutic target to boost organ repair. Studies in this area have focused on modulating the mTOR pathway in various animal models to elucidate its contribution to regeneration. The diversity of metazoan species used to identify the implication of this pathway might then serve applied medicine (in better understanding what is required for efficient treatments in human diseases) but also evolutionary biology. Indeed, species-specific differences in mTOR modulation can contain the keys to appreciate why certain regeneration processes have been lost or conserved in the animal kingdom.

Pharmacological PTEN inhibition: potential clinical applications and effects in tissue regeneration

Although the human body can heal, it takes time, and slow healing and chronic wounds often occur. Thus, identifying novel therapies to aid regeneration is needed. Here, we conducted a systematic review following the Preferred Reporting Items for Systematic Reviews guidelines and assessed preclinical studies on phosphatase and tensin homolog (PTEN) inhibitors and their effects on tissue repair and regeneration. In conditions associated with neurodegeneration, tissue injury and ischemia, the PTEN-regulated PI3K/AKT signaling pathway is activated. The use of PTEN inhibitors resulted in better tissue response by reducing the healing time and lesion sizes or inducing neuronal regeneration. Notably, all studies included in this systematic review indicated that pharmacological inhibition of PTEN enhanced the repair process of the eye, lung, muscle and nervous system.

Glycofullerenes Inhibit Particulate Matter Induced Inflammation and Loss of Barrier Proteins in HaCaT Human Keratinocytes

Exposure to particulate matter (PM) has been linked to pulmonary and cardiovascular dysfunctions, as well as skin diseases, etc. PM impairs the skin barrier functions and is also involved in the initiation or exacerbation of skin inflammation, which is linked to the activation of reactive oxygen species (ROS) pathways. Fullerene is a single C₆₀ molecule which has been reported to act as a good radical scavenger. However, its poor water solubility limits its biological applications. The glyco-modification of fullerenes increases their water solubility and anti-bacterial and anti-virus functions. However, it is still unclear whether it affects their anti-inflammatory function against PM-induced skin diseases. Hence, glycofullerenes were synthesized to investigate their effects on PM-exposed HaCaT human keratinocytes. Our results showed that glycofullerenes could reduce the rate of PM-induced apoptosis and ROS production, as well as decrease the expression of downstream mitogen-activated protein kinase and Akt pathways. Moreover, PM-induced increases in inflammatory-related signals, such as cyclooxygenase-2, heme oxygenase-1, and prostaglandin E2, were also suppressed by glycofullerenes. Notably, our results suggested that PM-induced impairment of skin barrier proteins, such as filaggrin, involucrin, repetin, and loricrin, could be reduced by pre-treatment with glycofullerenes. The results of this study indicate that glycofullerenes could be potential candidates for treatments against PM-induced skin diseases and that they exert their protective effects via ROS scavenging, anti-inflammation, and maintenance of the expression of barrier proteins.

Integrin β1 in Adipose-Derived Stem Cells Accelerates Wound Healing via Activating PI3K/AKT Pathway

BACKGROUND

This study aims to investigate the effect of integrin β1 on wound healing induced by adipose-derived stem cells (ADSCs), as well as the corresponding mechanism.

METHODS

Integrin β1 was overexpressed in ADSCs. Thereafter, flow cytometry and transwell chambers technology were used to measure the endothelial-like differentiation (CD31 as a biomarker of endothelial cell) and cell migration, respectively. Western blot was used to detect the activation of PI3K/AKT, NF-κB and ERK signaling pathways. The effects of integrin β1 overexpression on healing time, healing rate and fibroblast number were further evaluated in the rat models of chronic refractory wound.

RESULTS

The overexpression of integrin β1 increased CD31⁺ endothelial-like cells (about 3.6-fold), promoted cell migration (about 1.9-fold) and enhanced the activation of PI3K (p-PI3K; about 2.1-fold) and AKT (p-AKT; about 2.2-fold). These effects were all weakened when PI3K/AKT pathway was inhibited by LY294002 treatment. In addition, the experiments in rat wound models showed that integrin β1 overexpression obviously shortened healing time (approximately 0.41-fold), increased healing rate (about 2.7-fold, 2.8-fold and 1.6-fold at day 7, 14 and 21) and increased the number of fibroblasts (approximately 3.1-fold at day 21). All of the above differences were statistically significant (p < 0.05).

CONCLUSION

Integrin β1 can promote the migration and endothelial-like differentiation of ADSCs by activating PI3K/AKT pathway and then enhance the function of ADSCs in promoting wound healing.

CD9 regulates keratinocyte differentiation and motility by recruiting E-cadherin to the plasma membrane and activating the PI3K/Akt pathway

During keratinocyte stratification and wound healing, keratinocytes undergo a switch between differentiation and motility. However, limited knowledge exists on the mechanisms of the switch. We have previously demonstrated that the expression of CD9 was changed in different wound stages and involved in the regulation of keratinocyte migration. In this study, we showed that CD9 expression was increased in both human and mouse keratinocytes undergoing differentiation. CD9 overexpression in keratinocytes stimulated terminal differentiation and reduced cell motility. CD9 silencing inhibited calcium-induced keratinocyte differentiation and increased cell motility. Furthermore, CD9 overexpression recruited E-cadherin to the plasma membrane and subsequently activated PI3K/Akt signaling, while CD9 knockdown inhibited the recruitment of E-cadherin to the plasma membrane and PI3K/Akt activation. Importantly, silencing E-cadherin expression or inhibiting PI3K/Akt signaling reversed CD9 overexpression-induced differentiation and -reduced motility. These results demonstrate that CD9 acts as an important node that regulates keratinocyte differentiation and motility. The recruitment of E-cadherin to the plasma membrane and activation of the PI3K/Akt signaling pathway mediated by CD9 play an important role in these processes.

Water-Soluble Fullerenol C60(OH)36 toward Effective Anti-Air Pollution Induced by Urban Particulate Matter in HaCaT Cell

Particulate matter (PM), a widespread air pollutant, consists of a complex mixture of solid and liquid particles suspended in air. Many diseases have been linked to PM exposure, which induces an imbalance in reactive oxygen species (ROS) generated in cells, and might result in skin diseases (such as aging and atopic dermatitis). New techniques involving nanomedicine and nano-delivery systems are being rapidly developed in the medicinal field. Fullerene, a kind of nanomaterial, acts as a super radical scavenger. Lower water solubility levels limit the bio-applications of fullerene. Hence, to improve the water solubility of fullerene, while retaining its radical scavenger functions, a fullerene derivative, fullerenol C₆₀(OH)₃₆, was synthesized, to examine its biofunctions in PM-exposed human keratinocyte (HaCaT) cells. The PM-induced increase in ROS levels and expression of phosphorylated mitogen-activated protein kinase and Akt could be inhibited via fullerenol pre-treatment. Furthermore, the expression of inflammation-related proteins, cyclooxygenase-2, heme oxygenase-1, and prostaglandin E2 was also suppressed. Fullerenol could preserve the impaired state of skin barrier proteins (filaggrin, involucrin, repetin, and loricrin), which was attributable to PM exposure. These results suggest that fullerenol could act against PM-induced cytotoxicity via ROS scavenging and anti-inflammatory mechanisms, and the maintenance of expression of barrier proteins, and is a potential candidate compound for the treatment of skin diseases.

Human amniotic mesenchymal stem cells and their paracrine factors promote wound healing by inhibiting heat stress-induced skin cell apoptosis and enhancing their proliferation through activating PI3K/AKT signaling pathway

Background

Increasing evidence has shown that mesenchymal stem cells (MSCs) yield a favorable therapeutic benefit for thermal burn skin wounds. Human amniotic MSCs (hAMSCs) derived from amniotic membrane have multilineage differentiation, immunosuppressive, and anti-inflammatory potential which makes them suitable for treating skin wounds. However, the exact effects of hAMSCs on the healing of thermal burn skin wounds and their potential mechanisms are not explored.

Methods

hAMSCs were isolated from amniotic membrane and characterized by RT-PCR, flow cytometry, immunofluorescence, and tumorigenicity test. We assessed the effects of hAMSCs and hAMSC conditional medium (CM) on wound healing in a deep second-degree burn injury model of mice. We then investigated the biological effects of hAMSCs and hAMSC-CM on the apoptosis and proliferation of heat stress-injured human keratinocytes HaCAT and dermal fibroblasts (DFL) both in vivo and in vitro. Next, we explored the underlying mechanisms by assessing PI3K/AKT and GSK3β/β-catenin signaling pathways in heat injured HaCAT and DFL cells after hAMSCs and hAMSC-CM treatments using PI3K inhibitor LY294002 and β-catenin inhibitor ICG001. Antibody array assay was used to identify the cytokines secreted by hAMSCs that may activate PI3K/AKT signaling pathway.

Results

Our results showed that hAMSCs expressed various markers of embryonic stem cells and mesenchymal stem cells and have low immunogenicity and no tumorigenicity. hAMSC and hAMSC-CM transplantation significantly promoted thermal burn wound healing by accelerating re-epithelialization with increased expression of CK19 and PCNA in vivo. hAMSCs and hAMSC-CM markedly inhibited heat stress-induced apoptosis in HaCAT and DFL cells in vitro through activation of PI3K/AKT signaling and promoted their proliferation by activating GSK3β/β-catenin signaling. Furthermore, we demonstrated that hAMSC-mediated activation of GSK3β/β-catenin signaling was dependent on PI3K/AKT signaling pathway. Antibody array assay showed that a panel of cytokines including PAI-1, C-GSF, periostin, and TIMP-1 delivered from hAMSCs may contribute to the improvement of the wound healing through activating PI3K/AKT signaling pathway.

Conclusion

Our results demonstrated that hAMSCs and hAMSC-CM efficiently cure heat stress-induced skin injury by inhibiting apoptosis of skin cells and promoting their proliferation through activating PI3K/AKT signaling pathway, suggesting that hAMSCs and hAMSC-CM may provide an alternative therapeutic approach for the treatment of skin injury.

Electronic supplementary material

The online version of this article (10.1186/s13287-019-1366-y) contains supplementary material, which is available to authorized users.