PTEN: a promising pharmacological target to enhance epithelial wound healing

The Role of Ubiquitination and the E3 Ligase Nedd4 in Regulating Corneal Epithelial Wound Healing

Purpose

Ubiquitination serves as a fundamental post-translational modification in numerous cellular events. Yet, its role in regulating corneal epithelial wound healing (CEWH) remains elusive. This study endeavored to determine the function and mechanism of ubiquitination in CEWH.

Methods

Western blot and immunoprecipitation were used to discern ubiquitination alterations during CEWH in mice. Interventions, including neuronally expressed developmentally downregulated 4 (Nedd4) siRNA and proteasome/lysosome inhibitor, assessed their impact on CEWH. In vitro analyses, such as the scratch wound assay, MTS assay, and EdU staining, were conducted to gauge cell migration and proliferation in human corneal epithelial cells (HCECs). Moreover, transfection of miR-30/200 coupled with a luciferase activity assay ascertained their regulatory mechanism on Nedd4.

Results

Global ubiquitination levels were markedly increased during the mouse CEWH. Importantly, the application of either proteasomal or lysosomal inhibitors notably impeded the healing process both in vivo and in vitro. Furthermore, Nedd4 was identified as an essential E3 ligase for CEWH. Nedd4 expression was significantly upregulated during CEWH. In vivo studies revealed that downregulation of Nedd4 substantially delayed CEWH, whereas further investigations underscored its role in regulating cell proliferation and migration, through the Stat3 pathway by targeting phosphatase and tensin homolog (PTEN). Notably, our findings pinpointed miR-30/200 family members as direct regulators of Nedd4.

Conclusions

Ubiquitination holds pivotal significance in orchestrating CEWH. The critical E3 ligase Nedd4, under the regulatory purview of miR-30 and miR-200, facilitates CEWH through PTEN-mediated Stat3 signaling. This revelation sheds light on a prospective therapeutic target within the realm of CEWH.

A multifunctional silk-hyaluronic acid self-healing hydrogel laden with alternatively activated macrophage-derived exosomes reshape microenvironment of diabetic wound and accelerate healing

The impairment of phenotype switching of pro-inflammatory M1 to pro-healing M2 macrophage induced by hyperglycemic microenvironment often elevates oxidative stress, impairs angiogenesis, and leads to chronic non-healing wounds in diabetic patients. Administration of M2 macrophage-derived exosomes (M2Exo) at wound site is known to polarize M1 to M2 macrophage and can accelerate wound healing by enhancing collagen deposition, angiogenesis, and re-epithelialization. In the present study, M2Exo were conjugated with oxidized hyaluronic acid and mixed with PEGylated silk fibroin to develop self-healing Exo-gel to achieve an efficient therapy for diabetic wounds. Exo-gel depicted porous networked morphology with self-healing and excellent water retention behaviour. Fibroblast cells treated with Exo-gel showed significant uptake of M2Exo that increased their proliferation and migration in vitro. Interestingly, in a diabetic wound model of wistar rats, Exo-gel treatment induced 75 % wound closure within 7 days with complete epithelial layer regeneration by modulating cytokine levels, stimulating fibroblast-keratinocyte interaction and migration, angiogenesis, and organized collagen deposition. Taken together, this study suggests that Exo-gel depict properties of an excellent wound healing matrix and can be used as a therapeutic alternative to treat chronic non-healing diabetic wounds.

[Experimental Study of Using Aloe Vera Gel to Treat Diabetic Chronic Cutaneous Ulcers in Bama Miniature Pigs]

Objective

To investigate the efficacy, safety, and mechanism of topical application of aloe vera gel (AVG) to treat diabetic chronic cutaneous ulcers in Bama miniature pigs.

Methods

The Bama miniature pig model of diabetic chronic skin wounds was constructed and the model pigs were randomly assigned to AVG daily administration group (AVG QD), aloe vera gel every-other-day administration group (AVG QOD), and diabetic control group (DC). A non-diabetic chronic skin wounds model pig was set as the non-diabetic control group (NDC). Treatment efficacy was evaluated based on the amount of time needed for complete healing of the wounds, healing rates, granulation growth rates, and skin histopathological changes. Safety was evaluated according to whether adverse reactions were observed. In addition, the dynamic changes of the relative expression levels of miR21, miR29a, miR126, miR146a, miR155, and miR210 in wound granulation tissues were examined.

Results

1) Efficacy and safety: The amount of time needed for complete healing of the wounds was shorter in the NDC group than those of the three other groups, DC group, AVG QD group, and AVG QOD group (all P<0.05). The amount of time needed for complete healing of the wounds was shorter in the AVG QD group and AVG QOD group than that of DC group (all P<0.05). The amount of time needed for complete healing of the wounds was shorter in the AVG QOD group than that of AVG QD group (all P<0.05). No adverse reactions were detected in the whole process of AVG topical treatment. The granulation growth rate of NDC group was higher than those of DC group, AVG QD group, and AVG QOD group (all P<0.05). The wound healing rate of NDC group was higher than those of DC group, AVG QD group, and AVG QOD group (all P<0.05); the wound healing rate of AVG QOD group was higher than those of DC group and AVG QD group (all P<0.05). 2) Histopathology: The results of HE staining light microscopy showed that collagen fiber production increased, and that microvascular formation with slight inflammatory cell infiltration was observed in the dermal interstitium at the initial stage of wound healing after AVG treatment. One year of after complete healing, pathological examination results of wound healing skin showed that the epidermal keratinization was complete, that collagen was arranged neatly and orderly, and that many microvessels were found in the interstitium. The results of picric acid celestite scarlet staining showed that, after AVG treatment, type Ⅰ collagen mainly increased in the initial stage of wound healing, type Ⅲ collagen gradually increased when the wound healed completely, and the collagen was arranged neatly during the whole process. 3) The relative expression of microRNAs: The relative expression of miR21, miR126, and miR210 in NDC group, AVG QD group, and AVG QOD group were higher than that in DC group (all P<0.05). The relative expression of miR29a and miR155 in NDC group, AVG QD group, and AVG QOD group was lower than that in DC group (all P<0.05). The relative expression of miR146a in NDC group was higher than that in DC group ( P<0.05).

Conclusion

AVG topical application can shorten the time needed for complete healing of diabetic chronic wounds in Bama minipigs. The wound healing speed of the alternate-day treatment group was faster than that of the daily treatment group. No adverse reactions were observed over the course of the treatment. The mechanism may be related to the up-regulation of the expressions of miR21, miR126, and miR210 and the down-regulation of miR29a and miR155 in wound granulation tissue.

Cytokeratin profile and keratinocyte gene expression in keratinized lid margins of patients with chronic Stevens-Johnson syndrome

PURPOSE

To study the cytokeratin profile and keratinization-related gene expression in keratinized lid margins of chronic Stevens-Johnson syndrome (SJS) patients.

METHODS

Posterior eyelid margins from 24 chronic SJS patients undergoing mucous membrane grafting and six healthy margins (orbital exenteration, fresh body donors) were studied using immunofluorescence staining (CK10, CK1, filaggrin, transglutaminase 1 (TGM1), (CK19, MUC5AC)) and quantitative PCR (keratinization-related genes-HBEGF, KGF, EGF, TGFα, TGFβ, and TNFα). The staining and gene expression were studied separately in the lid margin epidermis (LME) and lid margin conjunctiva (LMC).

RESULTS

The expression of CK 1/10, filaggrin, and TGM1 in the LMC was similar to the LME in SJS patients. CK19 was expressed only in the basal epithelial layer of the LMC with loss of MUC5AC expression. Increased expression of KGF (p ≤ 0.056), TNFα (p ≤ 0.02), and TGFα (p ≤ 0.01) was observed in the LME of SJS patients compared to normal LME. LMC of SJS patients showed an increased expression of HBEGF (p ≤ 0.002), EGF (p ≤ 0.0002), KGF (p ≤ 0.02), TNFα (p ≤ 0.04), TGFα (p ≤ 0.003), and TGFβ (p ≤ 0.001) compared to normal LMC. Significant differences were observed in the expression of these genes between LME and LMC of SJS patients. These genes were validated using String analysis, which revealed the positive regulation of keratinization.

CONCLUSION

In lid margins of SJS, there is an increased expression of keratinization-related genes compared to the normal lid margin. Keratinized LMC shares similar cytokeratin profile and keratinization gene expression as seen in cutaneous epithelium of SJS patients, indicating the possibility of the cutaneous epithelium as a source for keratinized LMC.

Single Dose of N-Acetylcysteine in Local Anesthesia Increases Expression of HIF1α, MAPK1, TGFβ1 and Growth Factors in Rat Wound Healing

In this study, we aimed to investigate the influence of N-acetylcysteine (NAC) on the gene expression profile, neoangiogenesis, neutrophils and macrophages in a rat model of incisional wounds. Before creating wounds on the backs of 24 Sprague-Dawley rats, intradermal injections were made. Lidocaine-epinephrin solutions were supplemented with 0.015%, 0.03% or 0.045% solutions of NAC, or nothing (control group). Scars were harvested on the 3rd, 7th, 14th and 60th day post-surgery. We performed immunohistochemical staining in order to visualize macrophages (anti-CD68), neutrophils (anti-MPO) and newly formed blood vessels (anti-CD31). Additionally, RT-qPCR was used to measure the relative expression of 88 genes involved in the wound healing process. On the 14th day, the number of cells stained with anti-CD68 and anti-CD31 antibodies was significantly larger in the tissues treated with 0.03% NAC compared with the control. Among the selected genes, 52 were upregulated and six were downregulated at different time points. Interestingly, NAC exerted a significant effect on the expression of 45 genes 60 days after its administration. In summation, a 0.03% NAC addition to the pre-incisional anesthetic solution improves neovasculature and increases the macrophages' concentration at the wound site on the 14th day, as well as altering the expression of numerous genes that are responsible for the regenerative processes.

Therapeutic effects of histone deacetylase inhibitors on heart disease

A wide range of histone deacetylase (HDAC) inhibitors have been studied for their therapeutic potential because the excessive activity and expression of HDACs have been implicated in the pathogenesis of cardiac diseases. An increasing number of preclinical studies have demonstrated the cardioprotective effects of numerous HDAC inhibitors, suggesting a wide variety of mechanisms by which the inhibitors protect against cardiac stress, such as the suppression of cardiac fibrosis and fetal gene expression, enhancement of angiogenesis and mitochondrial biogenesis, prevention of electrical remodeling, and regulation of apoptosis, autophagy, and cell cycle arrest. For the development of isoform-selective HDAC inhibitors with high efficacy and low toxicity, it is important to identify and understand the mechanisms responsible for the effects of the inhibitors. This review highlights the preclinical effects of HDAC inhibitors that act against Zn²⁺-dependent HDACs and the underlying mechanisms of their protective effects against cardiac hypertrophy, hypertension, myocardial infarction, heart failure, and atrial fibrillation.

Impact of Cytokines and Phosphoproteins in Response to Chronic Joint Infection

The early cellular response to infection has been investigated extensively, generating valuable information regarding the mediators of acute infection response. Various cytokines have been highlighted for their critical roles, and the actions of these cytokines are related to intracellular phosphorylation changes to promote infection resolution. However, the development of chronic infections has not been thoroughly investigated. While it is known that wound healing processes are disrupted, the interactions of cytokines and phosphoproteins that contribute to this dysregulation are not well understood. To investigate these relationships, this study used a network centrality approach to assess the impact of individual cytokines and phosphoproteins during chronic inflammation and infection. Tissues were taken from patients undergoing total knee arthroplasty (TKA) and total knee revision (TKR) procedures across two tissue depths to understand which proteins are contributing most to the dysregulation observed at the joint. Notably, p-c-Jun, p-CREB, p-BAD, IL-10, IL-12p70, IL-13, and IFN-γ contributed highly to the network of proteins involved in aseptic inflammation caused by implants. Similarly, p-PTEN, IL-4, IL-10, IL-13, IFN-γ, and TNF-α appear to be central to signaling disruptions observed in septic joints. Ultimately, the network centrality approach provided insight into the altered tissue responses observed in chronic inflammation and infection.

PTEN Inhibition Facilitates Diabetic Corneal Epithelial Regeneration by Reactivating Akt Signaling Pathway

Purpose

To investigate the contribution of phosphatase and tensin homologue (PTEN) on the delayed epithelial regeneration and impaired Akt activation in diabetic mice.

Methods

The expression of PTEN on cornea was compared between normal and diabetic mice. The corneal epithelial and nerve regeneration rate was evaluated in diabetic mice after the treatment with PTEN small interfering RNA (siRNA), PTEN inhibitors, or Akt inhibitor. The reactivation of epithelial regeneration-related signaling, including phosphorylated (p)-Akt, p-Stat3, Sirt1, and Parkin, were assessed with Western blot and immunofluorescence staining. The effects of PTEN inhibition on cellular proliferation and migration were further evaluated in cultured mouse corneal epithelial cells.

Results

PTEN messenger RNA and protein levels exhibited up-regulation in diabetic cornea. Upon central epithelial debridement, the epithelial regeneration rate was significantly promoted in diabetic mice with the treatment of PTEN inhibition than that of vehicle control (P < 0.05), which accompanied with the recovered levels of p-Akt, p-Stat3, Sirt1, and Parkin. However, the promotion of diabetic corneal epithelial regeneration rate and Akt reactivation was completed reversed by Akt inhibitor. In vitro, PTEN inhibition promoted their migration, but not the proliferation capacity. In addition, PTEN inhibitor treatment also improved the recovery of corneal nerve fiber density and sensitivity that was impaired in diabetic mice.

Conclusions

Elevated PTEN expression contributes to the impaired corneal epithelial regeneration and Akt activation in diabetic mice, which can be improved with PTEN inhibition.

Translational Relevance

Our study suggests that PTEN inhibition may serve as a new strategy for restoring the impaired corneal epithelial regeneration ability in patients with diabetes.

BMP2-mediated PTEN enhancement promotes differentiation of hair follicle stem cells by inducing autophagy

The proliferation and differentiation of hair follicle stem cells (HFSCs) is regulated by several signaling pathways, including BMP and PTEN. Therefore, this study intended to clarify the potential effects of two such regulators, BMP2 and PTEN, on HFSC differentiation. HFSCs were subjected to BMP2, noggin (BMP2 ligand inhibitor), rapamycin (Rapa, autophagy inducer), 3-methyladenine (3-MA, autophagy inhibitor), or shRNA against PTEN. The differentiation of HFSCs was evaluated using oil red O staining and autophagy was assessed using the transmission electron microscope. Then expression of epidermal differentiation marker (K10 and involucrin), adipogenic markers (PPAR-γ2, aP2, perilipin2, and Adipoq), keratinocyte-specific marker (K15), proliferation-related markers (PCNA and Ki67) and autophagy-related factors (Atg5, Atg7, Atg12, Beclin-1 and LC3-II/LC3-I) was examined by RT-qPCR and Western blot analysis. Next, HFSCs were treated with 3-MA, or shRNA against Atg5 or Atg7 to verify the effect of autophagy on differentiation of BMP2-treated HFSCs. Finally, the effect of BMP2 on HFSC differentiation was verified by a mouse wound model. HFSCs overexpressing BMP2 exhibited elevated expression of epidermal differentiation marker, adipogenic markers and autophagy-related factors but inhibited expression of keratinocyte-specific marker and proliferation-related markers. Furthermore, we found that PTEN promoted the differentiation of BMP2-treated HFSCs by inducing autophagy. In vivo experiments further confirmed the roles of BMP2/PTEN on differentiation of HFSCs. Taken together, BMP2 up-regulated PTEN and consequently induced autophagy to facilitate HFSC differentiation.

LncRNAs-directed PTEN enzymatic switch governs epithelial-mesenchymal transition

Despite the structural conservation of PTEN with dual-specificity phosphatases, there have been no reports regarding the regulatory mechanisms that underlie this potential dual-phosphatase activity. Here, we report that K27-linked polyubiquitination of PTEN at lysines 66 and 80 switches its phosphoinositide/protein tyrosine phosphatase activity to protein serine/threonine phosphatase activity. Mechanistically, high glucose, TGF-β, CTGF, SHH, and IL-6 induce the expression of a long non-coding RNA, GAEA (Glucose Aroused for EMT Activation), which associates with an RNA-binding E3 ligase, MEX3C, and enhances its enzymatic activity, leading to the K27-linked polyubiquitination of PTEN. The MEX3C-catalyzed PTENK27-polyUb activates its protein serine/threonine phosphatase activity and inhibits its phosphatidylinositol/protein tyrosine phosphatase activity. With this altered enzymatic activity, PTENK27-polyUb dephosphorylates the phosphoserine/threonine residues of TWIST1, SNAI1, and YAP1, leading to accumulation of these master regulators of EMT. Animals with genetic inhibition of PTENK27-polyUb, by a single nucleotide mutation generated using CRISPR/Cas9 (PtenK80R/K80R), exhibit inhibition of EMT markers during mammary gland morphogenesis in pregnancy/lactation and during cutaneous wound healing processes. Our findings illustrate an unexpected paradigm in which the lncRNA-dependent switch in PTEN protein serine/threonine phosphatase activity is important for physiological homeostasis and disease development.

Nature's Electric Potential: A Systematic Review of the Role of Bioelectricity in Wound Healing and Regenerative Processes in Animals, Humans, and Plants

Natural endogenous voltage gradients not only predict and correlate with growth and development but also drive wound healing and regeneration processes. This review summarizes the existing literature for the nature, sources, and transmission of information-bearing bioelectric signals involved in controlling wound healing and regeneration in animals, humans, and plants. It emerges that some bioelectric characteristics occur ubiquitously in a range of animal and plant species. However, the limits of similarities are probed to give a realistic assessment of future areas to be explored. Major gaps remain in our knowledge of the mechanistic basis for these processes, on which regenerative therapies ultimately depend. In relation to this, it is concluded that the mapping of voltage patterns and the processes generating them is a promising future research focus, to probe three aspects: the role of wound/regeneration currents in relation to morphology; the role of endogenous flux changes in driving wound healing and regeneration; and the mapping of patterns in organisms of extreme longevity, in contrast with the aberrant voltage patterns underlying impaired healing, to inform interventions aimed at restoring them.

Correlations of PTEN genetic polymorphisms with the risk of depression and depressive symptoms in a Chinese population

OBJECTIVE

This study aimed to investigate the correlations of three common single nucleotide polymorphisms (SNPs) in the PTEN gene (rs701848 T>C, rs2735343 G>C and rs112025902 A>T) with the risk of depression and depressive symptoms in a Chinese population.

METHODS

From July 2011 to June 2013, a total of 384 patients with depression and 400 healthy individuals were included in this study. These SNPs in the PTEN gene were detected by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and direct sequencing. The Hamilton Depression Rating Scale (HAMD) was used to evaluate the severity of depression.

RESULTS

The C allele of rs701848, the C allele of rs2735343 and the T allele of rs112025902 were associated with an increased risk of depression (odds ratio [OR]=3.814, 95% CI: 3.093-4.703, P<0.001; OR=2.642, 95% CI: 2.152-3.242, P<0.001; OR=2.882, 95% CI: 2.347-3.539, P<0.001; respectively). Depression patients carrying C allele (TC+CC) of rs701848 and carrying T allele (AT+TT) of rs112025902 had higher HAMD total scores and HAMD anxiety factor scores than those carrying TT genotype of rs701848 and carrying AA genotype of rs112025902 (all P<0.05). Furthermore, depression patients carrying C allele (GC+CC) of rs2735343 had lower HAMD total scores and HAMD factors associated with depression scores than those carrying GG genotype (both P<0.05). Logistic regression analysis revealed that rs701848, rs2735343 and rs112025902 polymorphisms in the PTEN gene may be independent risk factors of depression (relative risk [RR]=1.807, 95% CI=1.023-3.193, P=0.042; RR=1.759, 95% CI=1.033-2.995, P=0.038; RR=1.646, 95% CI=1.018-2.663, P=0.042; respectively).

CONCLUSION

Our findings provide evidence that rs701848, rs2735343 and rs112025902 polymorphisms in the PTEN gene may be correlated with the risk of depression and depressive symptoms in the Chinese population.

IL-6 as a corneal wound healing mediator in an in vitro scratch assay

Corneal healing process under inflammatory conditions is not fully understood. We aimed at determining the effect of an inflammatory (presence of IL-6) or anti-inflammatory (presence of IL-10) environment and a mixture of both in the expression of IL-6 signaling pathway mediators, and on corneal wound healing in an in vitro scratch assay. For that purpose, human corneal epithelial cells were cultured until confluence. The effect of IL-6 (10 ng/ml), IL-10 (20 ng/ml) or IL-6 + IL-10 exposure on the expression of IL-6R, gp130, and STAT3 was determined by Western blotting and quantitative PCR, at different time points. The monolayer was mechanically wounded using a sterile 10 μl pipette tip. Wound healing rate in the presence or absence of these cytokines was measured immediately after cytokine exposure and after 4, 8, and 24 h. The effect of mitomycin C on wound healing rate, in control and IL-6-stimulated cells, was also evaluated. Detection of proliferative cells was performed with an EdU imaging kit. For the visualization of migrating cells, cold methanol-fixed cells were incubated with an α-actinin antibody. For the statistical analysis a two-factor design of experiment method was applied. Levene test was used to contrast equality of variances. If variances were equal, ANOVA was performed to test the equality of means. If variances were not equal, a Mood's median test was performed. We observed that IL-6 and IL-10 stimulation, and their combination, increased gp130 production at different time points. STAT3 production was increased in IL-6-stimulated cells, at 72 h. An increase in pSTAT3 production was found in IL-6- and IL-10-stimulated cells, that was sustained in time in IL-6 + IL-10 co-stimulated cultures. Scraped areas had an initial width of 570.57 ± 75.82 μm. In IL-6-exposed cells wound healing closure was faster than in control cells or IL-10-exposed cells. After 8 h, wound width in IL-10-exposed cells, was also significantly smaller than that of control cells. Cells exposed to IL-6 + IL-10 had the slowest wound healing rate, similar to control cells. Wounds were closed after 24 h regardless the experimental condition. Mitomycin C exposure increased the wound closure rate in every experimental condition. No significant differences in the percentage of proliferative cells at the edge of the scratch and in distant areas of the monolayer were found. At the edge of the scratch, some actin filaments of non-proliferative cells were directed through the cell-free area, independently of the stimulating condition. In conclusion, the presence of IL-10 and, most importantly, of IL-6, increased the wound healing rate in an in vitro corneal wound healing model. The combination of both cytokines did not have a synergistic action in wound healing. In our model, wound closure was the result of the combination of cell proliferation and cell migration.

Dual-specificity phosphatases as molecular targets for inhibition in human disease

SIGNIFICANCE

The dual-specificity phosphatases (DUSPs) constitute a heterogeneous group of cysteine-based protein tyrosine phosphatases, whose members exert a pivotal role in cell physiology by dephosphorylation of phosphoserine, phosphothreonine, and phosphotyrosine residues from proteins, as well as other non-proteinaceous substrates.

RECENT ADVANCES

A picture is emerging in which a selected group of DUSP enzymes display overexpression or hyperactivity that is associated with human disease, especially human cancer, making feasible targeted therapy approaches based on their inhibition. A panoply of molecular and functional studies on DUSPs have been performed in the previous years, and drug-discovery efforts are ongoing to develop specific and efficient DUSP enzyme inhibitors. This review summarizes the current status on inhibitory compounds targeting DUSPs that belong to the MAP kinase phosphatases-, small-sized atypical-, and phosphatases of regenerating liver subfamilies, whose inhibition could be beneficial for the prevention or mitigation of human disease.

CRITICAL ISSUES

Achieving specificity, potency, and bioavailability are the major challenges in the discovery of DUSP inhibitors for the clinics. Clinical validation of compounds or alternative inhibitory strategies of DUSP inhibition has yet to come.

FUTURE DIRECTIONS

Further work is required to understand the dual role of many DUSPs in human cancer, their function-structure properties, and to identify their physiologic substrates. This will help in the implementation of therapies based on DUSPs inhibition.

The biomolecular basis of adipogenic differentiation of adipose-derived stem cells

There is considerable attention regarding the role of receptor signaling and downstream-regulated mediators in the homeostasis of adipocytes, but less information is available concerning adipose-derived stem cell (ASC) biology. Recent studies revealed that the pathways regulating ASC differentiation involve the activity of receptor tyrosine kinases (RTKs), including fibroblast growth factor, vascular endothelial growth factor, ErbB receptors and the downstream-regulated serine/threonine protein kinase B (Akt) and phosphatase and tensin homolog (PTEN) activity. RTKs are cell surface receptors that represent key regulators of cellular homeostasis but also play a critical role in the progression of cancer. Many of the metabolic effects and other consequences of activated RTKs are mediated by the modulation of Akt and extracellular signal-regulated protein kinases 1 (Erk-1) signaling. Akt activity sustains survival and the adipogenic differentiation of ASCs, whereas Erk-1 appears downregulated. The inhibition of FGFR-1, EGFR and ErbB2 reduced proliferation, but only FGFR-1 inihibition reduced Akt activity and adipogenesis. Adipogenesis and neovascularization are also chronologically and spatially coupled processes and RTK activation and downstream targets are also involved in ASC-mediated angiogenesis. The potentiality of ASCs and the possibility to modulate specific molecular pathways underlying ASC biological processes and, in particular, those shared with cancer cells, offer new exciting strategies in the field of regenerative medicine.

Harnessing the Electric Spark of Life to Cure Skin Wounds

Significance: Skin wounds cause great distress and are a huge economic burden, particularly with an increasingly aging population that heals poorly. There is an urgent need for better therapies that improve repair. Intracellular signaling pathways that regulate wound repair are activated by growth factors, hormones, and cytokines released at the wound. In addition, endogenous electric fields (EFs) are generated by epithelia in response to injury and are an important cue that coordinates cell behavior at wounds. Electrical stimulation (ES), therefore, holds the potential to be effective therapeutically in treating wounds. Recent Advances: ES of wounds is an old idea based on observations of the natural occurrence of EF at wound sites. However, it is now receiving increasing attention, because (1) the underpinning mechanisms are being clarified; (2) devices that measure skin wound currents are in place; and (3) medical devices that apply EF to poorly healing wounds are in clinical use with promising results. Critical Issues: Several signaling proteins transduce the EF influence to cells. However, a bigger picture of the EF-proteome is needed in order to understand this complex process and target it in a controlled manner. Future Directions: Dissecting the signaling pathways driving electrical wound healing will allow further identification of key molecular switches that control the cellular response to EFs. These findings herald the development of a new concept, the use of hydrogel electrodes impregnated with small molecules that target signaling pathways to explore the potential of dual electric-pharmacological therapies to repair wounds.

Gene expression profile of cytokines and receptors of inflammation from cultured keratinocytes of burned patients

INTRODUCTION

At all stages of wound healing, growth factors and cytokines play a particularly important role in the interaction with keratinocytes cellular receptors. Keratinocytes have received little attention about their potential to act as a source and target of cytokines. Changes in the cytokine levels after the burning occur prior to the metabolic abnormalities. Thus, it may be possible to develop therapeutic interventions that can mitigate the acute inflammatory response and modulating expression of these cytokines. The objective was to evaluate the expression of 84 genes mediators of the inflammatory response by using PCR array in a primary human epidermal cultured keratinocytes from patients with burns.

METHODS

Keratinocytes cultured from normal skin around injury from small and large burn patient were treated for DNA synthesis. The samples were analyzed by the PCR Superarray(®) assay and curve analyses were performed for 84 relevant human genes and their involvement in the inflammatory cytokines pathway and receptors. These genes were checked for the up or down regulation. And it was used MetaCore™ for the analysis of networks and Gene Ontology (GO) processes.

RESULTS

Chemokines of the CXC family were more expressed in the large burn group, except CXCL12. The C, CC and CX3C chemokine family were downregulated, especially in the small burn group. The interleukins IL8 and IL1B were more expressed in large burn than in small burn; except IL13RA1, IL13 and IL5RA that were downregulated, mainly in the small burn group.

CONCLUSIONS

The cytokine profile showed some important differences between the large and small burn patients, and from this original database, we can create new interventional trials in acute inflammation in burns.

Role of inhibitors of mammalian target of rapamycin in the treatment of luminal breast cancer

Approximately 75% of patients with breast cancer present hormone receptor-positive tumors. This subtype of breast cancer initially shows a high overall response rate to hormonal treatments. However, resistance eventually develops, resulting in tumor progression. The PI3K/Akt/mTOR pathway regulates several cellular functions in cancer such as cell growth, survival, and proliferation. In addition, a high activation level of the PI3K/Akt/mTOR pathway is related to resistance to conventional chemotherapy and hormone therapy. The mTOR inhibitor everolimus, in combination with hormonal treatments, has led to excellent results in progression-free survival in patients with metastatic breast cancer resistant to hormone therapies. Therefore, everolimus has entered the National Comprehensive Cancer Network (NCCN) guidelines 2012 and its combination with exemestane was approved recently by the US Food and Drug Administration and the European Medicines Agency. This is the first time that a drug will have been approved for the restoration of hormone sensitivity in breast cancer.

Microfluidic device for studying cell migration in single or co-existing chemical gradients and electric fields

Cell migration is involved in physiological processes such as wound healing, host defense, and cancer metastasis. The movement of various cell types can be directed by chemical gradients (i.e., chemotaxis). In addition to chemotaxis, many cell types can respond to direct current electric fields (dcEF) by migrating to either the cathode or the anode of the field (i.e., electrotaxis). In tissues, physiological chemical gradients and dcEF can potentially co-exist and the two guiding mechanisms may direct cell migration in a coordinated manner. Recently, microfluidic devices that can precisely configure chemical gradients or dcEF have been increasingly developed and used for chemotaxis and electrotaxis studies. However, a microfluidic device that can configure controlled co-existing chemical gradients and dcEF that would allow quantitative cell migration analysis in complex electrochemical guiding environments is not available. In this study, we developed a polydimethylsiloxane-based microfluidic device that can generate better controlled single or co-existing chemical gradients and dcEF. Using this device, we showed chemotactic migration of T cells toward a chemokine CCL19 gradient or electrotactic migration toward the cathode of an applied dcEF. Furthermore, T cells migrated more strongly toward the cathode of a dcEF in the presence of a competing CCL19 gradient, suggesting the higher electrotactic attraction. Taken together, the developed microfluidic device offers a new experimental tool for studying chemical and electrical guidance for cell migration, and our current results with T cells provide interesting new insights of immune cell migration in complex guiding environments.

MicroRNA signature in diabetic wound healing: promotive role of miR-21 in fibroblast migration

A major complication of diabetes mellitus is the disruption of normal wound repair process, characterised by insufficient production of growth factors. A molecular genetic approach wherein resident cells synthesise and deliver the growth factors to the wound site would be a powerful therapeutic strategy to treat diabetic wounds. One such molecular approach could be the application of microRNAs (miRNAs). This study reports differential expression of miRNAs related to cell development and differentiation, during wound healing in diabetic mice. Comparison of skin tissue from normal and diabetic mice showed that 14 miRNAs were differentially expressed in diabetic skin; miR-146b and miR-21 were the most noteworthy. Expression pattern of these miRNAs was also altered during healing of diabetic wounds. A subset of miRNAs (miR-20b, miR-10a, miR-10b, miR-96, miR-128, miR-452 and miR-541) exhibited similar basal levels in normal and diabetic skins, but displayed dysregulation during healing of diabetic wounds. Amongst the miRNAs studied, miR-21 showed a distinct signature with increased expression in diabetic skin but decreased expression during diabetic wound healing. We analysed the role of miR-21 in fibroblast migration, because migration of fibroblasts into the wound area is an important landmark facilitating secretion of growth factors and migration of other cell types into the wound, thus enhancing the healing process. Using gain-of and loss-of function approaches, we show that miR-21 is involved in fibroblast migration. Our preliminary studies implicate an important role for miRNAs in the pathogenesis of diabetic wounds.

Downregulation of PTEN at corneal wound sites accelerates wound healing through increased cell migration

PURPOSE

The PI3K/Akt pathway is required for cell polarization and migration, whereas the phosphatase and tensin homologue deleted on chromosome 10 (PTEN) has inhibitory effects on the PI3K/Akt pathway. The authors therefore hypothesized that wounding would downregulate PTEN and that this downregulation would enhance wound healing.

METHODS

In human corneal epithelial (HCE) cell monolayer and rat cornea scratch wound models, the authors investigated PTEN and Akt expression using Western blot and immunofluorescence analyses. The effects of PTEN and PI3K inhibitors dipotassium bisperoxo (picolinato) oxovanadate (bpv(pic)) and LY294002 on cell migration and wound closure were investigated using time-lapse imaging. Finally, the authors investigated the effect of PTEN inhibition on wound healing in whole rat eyes.

RESULTS

In HCE cell monolayer and rat cornea, PTEN was downregulated at the wound edges within 30 minutes of wounding. The downregulation of PTEN was causal in a simultaneous increase in Akt activation, which was responsible for a significant increase in individual cell migration rate from 8.8 μm/h to 17.3 μm/h. An increased migration rate was maintained for 20 hours. PTEN inhibition significantly enhanced the wound healing rate in the HCE cell monolayer from 10 minutes onward after treatment and reduced the healing time in eye organ culture from 30 to 20 hours.

CONCLUSIONS

Injury to the corneal epithelium downregulates the expression of PTEN at wound edges, allowing increased PI3K/Akt signaling, thereby contributing to a significant enhancement of cell migration and wound healing. These results suggest that PTEN inhibition may be an effective treatment for corneal injury.

Characterisation of the PTEN inhibitor VO-OHpic

PTEN (phosphatase and tensin homologue deleted on chromosome 10) is a phosphatidylinositol triphosphate 3-phosphatase that counteracts phosphoinositide 3-kinases and has subsequently been implied as a valuable drug target for diabetes and cancer. Recently, we demonstrated that VO-OHpic is an extremely potent inhibitor of PTEN with nanomolar affinity in vitro and in vivo. Given the importance of this inhibitor for future drug design and development, its mode of action needed to be elucidated. It was discovered that inhibition of recombinant PTEN by VO-OHpic is fully reversible. Both K(m) and V(max) are affected by VO-OHpic, demonstrating a noncompetitive inhibition of PTEN. The inhibition constants K(ic) and K(iu) were determined to be 27 ± 6 and 45 ± 11 nM, respectively. Using the artificial phosphatase substrate 3-O-methylfluorescein phosphate (OMFP) or the physiological substrate phosphatidylinositol 3,4,5-triphosphate (PIP(3)) comparable parameters were obtained suggesting that OMFP is a suitable substrate for PTEN inhibition studies and PTEN drug screening.

Accelerated wound healing by mTOR activation in genetically defined mouse models

Background

The management of slow or non-healing ulcerations constitutes an increasing clinical challenge in the developed world because of the ageing of the population and the pandemic rise in type II diabetes. Recent studies suggest that molecular circuitries deployed by tumor cells to promote cancerous growth may also contribute to tissue regeneration. Here, we exploited this emerging information to search for novel molecular targets to accelerate wound healing.

Methodology/Principal Findings

We found that the activation of the PI3K-Akt-mTOR pathway, whose aberrant function is a frequent event in human neoplasia, represents an integral component of the normal wound healing process. By the use of genetically defined approaches, including the epithelial-specific ablation of Pten and Tsc1, we show that mTOR activation can dramatically increase epithelial cell proliferation, migration, and cutaneous wound healing, while pharmacological inhibition of mTOR with rapamycin delays wound closure.

Conclusions/Significance

Overall, our findings indicate that the transient pharmacologic activation of the PI3K-Akt-mTOR signaling axis may represent a novel clinical intervention strategy to accelerate the healing of debilitating and life-threatening wounds.

Akt inhibition up-regulates MMP1 through a CCN2-dependent pathway in human dermal fibroblasts

Akt is a key signalling molecule that was found to be down-regulated in chronic wounds. Akt blockade has dual antifibrotic effects in human dermal fibroblasts, by up-regulating matrix metalloproteinase 1 (MMP1) and down-regulating collagen gene expression (J Invest Dermatol 2008: 128: 1906). The aim of this study was to gain additional insights into the mechanism of MMP1 up-regulation following Akt blockade. As previous studies showed that CCN2 can be a positive regulator of MMP1, we examined the effects of Akt inhibition on CCN2 expression. Akt blockade using a specific pharmacological inhibitor and Akt siRNA resulted in a significant up-regulation of CCN2, which correlated with the increase in MMP1. The MMP1 up-regulation following Akt blockade was partially suppressed by CCN2 siRNA, suggesting that CCN2 is contributing to this effect. Additional experiments showed that CCN2 induces phosphorylation of ERK1/2, Ets1 and c-Jun. Consistent with the stimulatory role of ERK1/2/Ets1 in the expression of MMP1, the ERK1/2 inhibitor UO126 prevented the phosphorylation of ERK1/2 and Ets1 and completely abrogated the induction of MMP1 after CCN2 overexpression, while having no effect on c-Jun activation. Taken together these results establish CCN2 as a key regulator of MMP1 induction via activation of the ERK1/2/Ets1 pathway. Down-regulation of Akt signalling leads to inappropriate activation of the CCN2/MMP1 pathway that may contribute to the pathogenesis of chronic wounds. Coordinate expression of CCN2, Akt and MMP1 could be important for normal wound healing to occur. Thus, targeting these specific proteins may represent a promising approach to the therapy of dysregulated wound healing.

Function and dysfunction of the PI system in membrane trafficking

The phosphoinositides (PIs) function as efficient and finely tuned switches that control the assembly–disassembly cycles of complex molecular machineries with key roles in membrane trafficking. This important role of the PIs is mainly due to their versatile nature, which is in turn determined by their fast metabolic interconversions. PIs can be tightly regulated both spatially and temporally through the many PI kinases (PIKs) and phosphatases that are distributed throughout the different intracellular compartments. In spite of the enormous progress made in the past 20 years towards the definition of the molecular details of PI–protein interactions and of the regulatory mechanisms of the individual PIKs and phosphatases, important issues concerning the general principles of the organisation of the PI system and the coordination of the different PI-metabolising enzymes remain to be addressed. The answers should come from applying a systems biology approach to the study of the PI system, through the integration of analyses of the protein interaction data of the PI enzymes and the PI targets with those of the ‘phenomes' of the genetic diseases that involve these PI-metabolising enzymes.

Platelet lysate stimulates wound repair of HaCaT keratinocytes

BACKGROUND

Platelets play a pivotal role in wound healing. Their beneficial effect is attributed to the release of bioactive substances, although the involved mechanisms are mostly unknown.

OBJECTIVES

To investigate mechanisms underlying platelet-induced wound healing using HaCaT keratinocytes, representing an in vitro model of proliferating and migrating keratinocytes.

METHODS

Cells were exposed to platelet lysate (PL) purified from whole blood samples. Cell metabolism and proliferation were assessed using MTS and crystal violet assays, respectively, wound healing was assessed by scratch wound assay and cell migration by transwell assay. Extracellular signal-regulated kinase (ERK) 1/2 and p38 activations were studied using Western immunoblotting and intracellular Ca(2+) dynamics by confocal imaging.

RESULTS

Wound closure rates showed a significant increase at 6 and 24 h in cells exposed to nontoxic 20% PL. The cell migration assay showed a strong chemotactic effect toward PL. The intracellular Ca(2+) chelator BAPTA-AM induced 100% inhibition of the PL effect on wound closure rate, while among the kinase inhibitors, SB203580 exerted about 50% inhibition, and PD98059, wortmannin and LY294002 about 30% inhibition. SB203580 and BAPTA-AM induced 100% inhibition of the PL effect on cell migration, PD98059 about 50% inhibition, and wortmannin and LY294002 no significant inhibition. Confocal imaging allowed detection of a sustained Ca(2+) transient in PL-treated cells, while Western blot showed a more rapid activation of p38 than of ERK1/2.

CONCLUSIONS

Data indicate that PL increases wound healing rate by stimulating keratinocyte migration through a calcium- and p38-dependent mechanism. ERK1/2 and phosphoinositide-3 kinase seem to play minor roles.