Loss of Smad3 modulates wound healing

Antiviral drugs prolong survival in murine recessive dystrophic epidermolysis bullosa

Recessive dystrophic epidermolysis bullosa (RDEB) is a rare inherited skin disease characterized by defects in type VII collagen leading to a range of fibrotic pathologies resulting from skin fragility, aberrant wound healing, and altered dermal fibroblast physiology. Using a novel in vitro model of fibrosis based on endogenously produced extracellular matrix, we screened an FDA-approved compound library and identified antivirals as a class of drug not previously associated with anti-fibrotic action. Preclinical validation of our lead hit, daclatasvir, in a mouse model of RDEB demonstrated significant improvement in fibrosis as well as overall quality of life with increased survival, weight gain and activity, and a decrease in pruritus-induced hair loss. Immunohistochemical assessment of daclatasvir-treated RDEB mouse skin showed a reduction in fibrotic markers, which was supported by in vitro data demonstrating TGFβ pathway targeting and a reduction of total collagen retained in the extracellular matrix. Our data support the clinical development of antivirals for the treatment of patients with RDEB and potentially other fibrotic diseases.

Optogenetic engineered umbilical cord MSC-derived exosomes for remodeling of the immune microenvironment in diabetic wounds and the promotion of tissue repair

BACKGROUND

Angiogenesis and tissue repair in chronic non-healing diabetic wounds remain critical clinical problems. Engineered MSC-derived exosomes have significant potential for the promotion of wound healing. Here, we discuss the effects and mechanisms of eNOS-rich umbilical cord MSC exosomes (UCMSC-exo/eNOS) modified by genetic engineering and optogenetic techniques on diabetic chronic wound repair.

METHODS

Umbilical cord mesenchymal stem cells were engineered to express two recombinant proteins. Large amounts of eNOS were loaded into UCMSC-exo using the EXPLOR system under blue light irradiation. The effects of UCMSC-exo/eNOS on the biological functions of fibroblasts and vascular endothelial cells in vitro were evaluated. Full-thickness skin wounds were constructed on the backs of diabetic mice to assess the role of UCMSC-exo/eNOS in vascular neogenesis and the immune microenvironment, and to explore the related molecular mechanisms.

RESULTS

eNOS was substantially enriched in UCMSCs-exo by endogenous cellular activities under blue light irradiation. UCMSC-exo/eNOS significantly improved the biological functions of cells after high-glucose treatment and reduced the expression of inflammatory factors and apoptosis induced by oxidative stress. In vivo, UCMSC-exo/eNOS significantly improved the rate of wound closure and enhanced vascular neogenesis and matrix remodeling in diabetic mice. UCMSC-exo/eNOS also improved the inflammatory profile at the wound site and modulated the associated immune microenvironment, thus significantly promoting tissue repair.

CONCLUSION

This study provides a novel therapeutic strategy based on engineered stem cell-derived exosomes for the promotion of angiogenesis and tissue repair in chronic diabetic wounds.

Efficacy and safety of Resina Draconis for wound repair in the treatment of diabetic foot ulcer: A systematic review and meta-analysis of randomized controlled trials

BACKGROUND AND PURPOSE

Resina Draconis (RD) is widely used to treat topical skin ulcers. However, its effect on diabetic foot ulcer (DFU) remains unknown. The present meta-analysis aims to evaluate the efficacy and safety of RD for wound healing in DFU treatment.

METHODS

Literature searches were conducted with databases including PubMed, Embase, Cochrane Library, the China National Knowledge Infrastructure, the Wanfang Database, the Database for Chinese Technical Periodicals, and the China Biology Medicine Disc. Relevant studies were selected based on specified inclusion and exclusion criteria. Software RevMan 5.4 was used for study selection, quality assessment, and data analysis, while the Cochrane Risk of Bias (RoB) 2.0 tool was used to assess RoB.

RESULTS

Nine eligible randomized controlled trials (RCTs), involving 679 patients, were included in this review. The results showed that the healing time of the RD group was shorter than that of the control group (P < 0.00001), while the RD group also presented a higher healing rate (P < 0.0001), a higher rate of ulcer area reduction (P = 0.0005), and a higher rate in the patients with a reduced Wagner grade (P = 0.002). Simultaneously, a lower frequency of dressing changes (P < 0.00001) and a shorter length of hospital stays (P < 0.00001) are the characteristics of the RD group as well.

CONCLUSION

The treatment with RD is a safe and effective solution for DFU, and its combination with conventional treatment can improve the healing rate of DFU, reduce healing time, and inhibit further development. However, owing to the limited quality and quantity of included studies, further high-quality research is necessary to support these conclusions.

Bifunctional Peptide that Anneals to Damaged Collagen and Clusters TGF-β Receptors Enhances Wound Healing

Transforming growth factor-β (TGF-β) plays important roles in wound healing. The activity of TGF-β is initiated upon the binding of the growth factor to the extracellular domains of its receptors. We sought to facilitate the activation by clustering these extracellular domains. To do so, we used a known peptide that binds to TGF-β receptors without diminishing their affinity for TGF-β. We conjugated this peptide to a collagen-mimetic peptide that can anneal to the damaged collagen in a wound bed. We find that the conjugate enhances collagen deposition and wound closure in mice in a manner consistent with the clustering of TGF-β receptors. This strategy provides a means to upregulate the TGF-β signaling pathway without adding exogenous TGF-β and could inspire means to treat severe wounds.

Wound healing properties of flavonoids: A systematic review highlighting the mechanisms of action

BACKGROUND

Flavonoids are a class of compounds with a wide variety of biological functions, being an important source of new products with pharmaceutical potential, including treatment of skin wounds.

PURPOSE

This review aimed to summarize and evaluate the evidence in the literature in respect of the healing properties of flavonoids on skin wounds in animal models.

STUDY DESIGN

This is a systematic review following the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement.

METHODS

This was carried out through a specialized search of four databases: PubMed, Scopus, Web of Science and Embase. The following keyword combinations were used: "flavonoidal" OR "flavonoid" OR "flavonoidic" OR "flavonoids" AND "wound healing" as well as MeSH terms, Emtree terms and free-text words.

RESULTS

Fifty-five (55) articles met the established inclusion and exclusion criteria. Flavonoids presented effects in respect of the inflammatory process, angiogenesis, re-epithelialization and oxidative stress. They were shown to be able to act on macrophages, fibroblasts and endothelial cells by mediating the release and expression of TGF-β1, VEGF, Ang, Tie, Smad 2 and 3, and IL-10. Moreover, they were able to reduce the release of inflammatory cytokines, NFκB, ROS and the M1 phenotype. Flavonoids acted by positively regulating MMPs 2, 8, 9 and 13, and the Ras/Raf/MEK/ERK, PI3K/Akt and NO pathways.

CONCLUSION

Flavonoids are useful tools in the development of therapies to treat skin lesions, and our review provides a scientific basis for future basic and translational research.

Chronic Wound Healing by Amniotic Membrane: TGF-β and EGF Signaling Modulation in Re-epithelialization

The application of amniotic membrane (AM) on chronic wounds has proven very effective at resetting wound healing, particularly in re-epithelialization. Historically, several aspects of AM effect on wound healing have been evaluated using cell models. In keratinocytes, the presence of AM induces the activation of mitogen-activated protein (MAP) kinase and c-Jun N-terminal kinase (JNK) pathways, together with the high expression of c-Jun, an important transcription factor for the progression of the re-epithelialization tongue. In general, the levels of transforming growth factor (TGF)-β present in a wound are critical for the process of wound healing; they are elevated during the inflammation phase and remain high in some chronic wounds. Interestingly, the presence of AM, through epidermal growth factor (EGF) signaling, produces a fine-tuning of the TGF-β signaling pathway that re-conducts the stalled process of wound healing. However, the complete suppression of TGF-β signaling has proven negative for the AM stimulation of migration, suggesting that a minimal amount of TGF-β signaling is required for proper wound healing. Regarding migration machinery, AM contributes to the dynamics of focal adhesions, producing a high turnover and thus speeding up remodeling. This is clear because proteins, such as Paxillin, are activated upon treatment with AM. On top of this, AM also produces changes in the expression of Paxillin. Although we have made great progress in understanding the effects of AM on chronic wound healing, a long way is still ahead of us to fully comprehend its effects.

Tgf-β superfamily and limb regeneration: Tgf-β to start and Bmp to end

Axolotls represent a popular model to study how nature solved the problem of regenerating lost appendages in tetrapods. Our work over many years focused on trying to understand how these animals can achieve such a feat and not end up with a scarred up stump. The Tgf-β superfamily represents an interesting family to target since they are involved in wound healing in adults and pattern formation during development. This family is large and comprises Tgf-β, Bmps, activins and GDFs. In this review, we present work from us and others on Tgf-β & Bmps and highlight interesting observations between these two sub-families. Tgf-β is important for the preparation phase of regeneration and Bmps for the redevelopment phase and they do not overlap with one another. We present novel data showing that the Tgf-β non-canonical pathway is also not active during redevelopment. Finally, we propose a molecular model to explain how Tgf-β and Bmps maintain distinct windows of expression during regeneration in axolotls.

Umbilical cord-derived mesenchymal stem cells exert anti-fibrotic action on hypertrophic scar-derived fibroblasts in co-culture by inhibiting the activation of the TGF β1/Smad3 pathway

A hypertrophic scar (HS) is a severe fibrotic skin disease that causes disfigurement and deformity. It occurs after deep cutaneous injury and presents a major clinical challenge. The present study aimed to evaluate the effects of umbilical cord-derived mesenchymal stem cells (UCMSCs) on hypertrophic scar fibroblasts (HSFs), one of the main effector cells for HS formation, in a co-culture system and to investigate the potential underlying molecular mechanism. Cultured HSFs were divided into control and co-culture groups. The proliferation ability of HSFs was evaluated using cell counting kit-8 and the percentage of Ki67-positive fibroblasts was assessed by immunofluorescence. The apoptosis of HSFs was determined using a TUNEL assay and by assessing the expression of capase-3 via western blotting. A scratch wound healing assay was employed to examine the migration of HSFs. The expression levels of HS-associated genes (collagen type Iα 2 chain, collagen type IIIα 1 chain and actin α 2 smooth muscle) and proteins (collagen I, collagen III and α-smooth muscle actin) were measured by reverse transcription-quantitative PCR (RT-qPCR) and western blotting, respectively, to assess the pro-fibrotic phenotype of HSFs. The modulation of the transforming growth factor β1 (TGF β1)/Smad3 pathway in HSFs was evaluated by measuring the protein levels of TGF β1, Smad3 and phosphorylated Smad3 using western blotting, and the mRNA levels of TGFβ1 and several other target genes (cellular communication network factor 2, metalloproteinase inhibitor 1 and periostin) were measured by RT-qPCR. The proliferative and migratory ability of co-cultured HSFs was suppressed compared with controls, and no significant difference in apoptosis was observed between the two groups. The pro-fibrotic phenotype of co-cultured HSFs was inhibited due to a decline in expression levels of HS-associated genes and proteins. Furthermore, co-culture with UCMSCs inhibited the activation of the TGF β1/Smad3 pathway. In conclusion, the present study indicated that UCMSCs may exert an anti-fibrotic action on HSFs in co-culture through inhibition of the TGF β1/Smad3 pathway, which suggests a potential use for UCMSCs in HS therapy.

Direct and Indirect Roles of Macrophages in Hypertrophic Scar Formation

Hypertrophic scars are pathological scars that result from abnormal responses to trauma, and could cause serious functional and cosmetic disability. To date, no optimal treatment method has been established. A variety of cell types are involved in hypertrophic scar formation after wound healing, but the underlying molecular mechanisms and cellular origins of hypertrophic scars are not fully understood. Macrophages are major effector cells in the immune response after tissue injury that orchestrates the process of wound healing. Depending on the local microenvironment, macrophages undergo marked phenotypic and functional changes at different stages during scar pathogenesis. This review intends to summarize the direct and indirect roles of macrophages during hypertrophic scar formation. The in vivo depletion of macrophages or blocking their signaling reduces scar formation in experimental models, thereby establishing macrophages as positive regulatory cells in the skin scar formation. In the future, a significant amount of attention should be given to molecular and cellular mechanisms that cause the phenotypic switch of wound macrophages, which may provide novel therapeutic targets for hypertrophic scars.

The role of TGFβ in wound healing pathologies

Wound healing is one of the most complex processes in multicellular organisms, involving numerous intra- and intercellular signalling pathways in various cell types. It involves extensive communication between the cellular constituents of diverse skin compartments and its extracellular matrix. Miscommunication during healing may have two distinct damaging consequences: the development of a chronic wound or the formation of a hypertrophic scar/keloid. Chronic wounds are defined as barrier defects that have not proceeded through orderly and timely reparation to regain structural and functional integrity. Several growth factors are involved in wound healing, of which transforming growth factor beta (TGFβ) is of particular importance for all phases of this procedure. It exerts pleiotropic effects on wound healing by regulating cell proliferation, differentiation, extracellular matrix production, and modulating the immune response. In this review we are presenting the role of TGFβ in physiological and pathological wound healing. We show that the context-dependent nature of the TGFβ signaling pathways on wound healing is the biggest challenge in order to gain a therapeutically applicable comprehensive knowledge of their specific involvement in chronic wounds.

Amniotic membrane stimulates cell migration by modulating transforming growth factor-β signalling

Keratinocyte migration is a mandatory aspect of wound healing. We have previously shown that amniotic membrane (AM) applied to chronic wounds assists healing through a process resulting in the overexpression of c-Jun at the wound's leading edge. We have also demonstrated that AM modifies the genetic programme induced by transforming growth factor-ß (TGF-ß) in chronic wounds. Here we used a scratch assay of mink lung epithelial cells (Mv1Lu) and a spontaneously immortalized human keratinocyte cell line (HaCaT) cells to examine the influence of AM application on the underlying signalling during scratch closure. AM application induced c-Jun phosphorylation at the leading edge of scratch wounds in a process dependent on MAPK and JNK signalling. Strikingly, when the TGF-ß-dependent Smad-activation inhibitor SB431542 was used together with AM, migration improvement was partially restrained, whereas the addition of TGF-ß had a synergistic effect on the AM-induced cell migration. Moreover, antagonizing TGF-ß with specific antibodies in both cell lines or knocking out TGF-ß receptors in Mv1Lu cells had similar effects on cell migration as using SB431542. Furthermore, we found that AM was able to attenuate TGF-ß-Smad signalling specifically at the migrating edge; AM treatment abated Smad2 and Smad3 nuclear localization in response to TGF-ß in a process dependent on mitogen-activated protein kinase kinase 1 (MEK1) activation but independent of EGF receptor or JNK activation. The involvement of Smad signalling on AM effects on HaCaT keratinocytes was further corroborated by overexpression of either Smad2 or Smad3 and the use of Smad phosphorylation-specific inhibitors, revealing a differential influence on AM-induced migration for each Smad. Thus, AM TGF-ß-Smad signalling abating is essential for optimal cell migration and wound closure.

Amniotic membrane application for the healing of chronic wounds and ulcers

Wound healing usually follows a predictable sequence and prognosis of events. Its evolutionary process is the result of a complicated interaction between patient-related factors, the wound, the treatment used and the skills and knowledge of the professionals who treat them. Only through a meticulous initial assessment of the wound is it possible to identify the factors that contribute to its complexity. The challenge for professionals will be to implement efficient therapies at the right time and in the most cost-efficient way in order to reduce associated problems, treat the symptoms and expectations of the patients and achieve adequate wound healing whenever possible. This is particularly evident in big chronic wounds with considerable tissue loss, which become senescent in the process of inflammation or proliferation losing the ability to epithelialize. Generally, chronic wounds do not respond to current treatments, therefore they need special interventions. AM is a tissue of particular interest as a biological dressing and it has well-documented reepithelialization effects which are in part related to its capacity to synthesize and release biological active factors. Our studies have demonstrated that amniotic membrane (AM) is able to induce epithelialization in chronic wounds that were unable to epithelialize. AM induces several signaling pathways that are involved in cell migration and/or proliferation. Additionally, AM is able to selectively antagonize the anti-proliferative effect of transforming growth factor-ß (TGF-β) by modifying the genetic program that TGF-β induces on keratinocytes. The combined effect of AM on keratinocytes, promoting cell proliferation/migration and antagonizing the effect of TGF-β is the perfect combination, allowing chronic wounds to move out of their non-healing state and progress into epithelialization.

Activation of Smad2 but not Smad3 is required for mediating TGF-beta signaling during limb regeneration in axolotls

Axolotls are unique amongst vertebrates in their ability to regenerate their tissues (e.g. limbs, tail, skin etc.). The axolotl limb is the most studied regenerating structure. The process is well characterized morphologically; however, it is not well understood at the molecular level. We demonstrate that TGF-β1 is highly regulated during regeneration and that its signaling is necessary. The present study clearly shows that the basement membrane is not prematurely formed in animals treated with the TGF-β antagonist SB-431542. More importantly, it shows that Smad2 and Smad3 are differentially regulated post-translationally during the preparation phase of limb regeneration. Using specific antagonists for Smad2 and Smad3, results indicate that Smad2 is responsible for the action of TGF-β during regeneration and that Smad3 is not required. We also show that Smad2 target genes (MMP2 & 9) are inhibited in SB-431542 treated limbs and non-canonical TGF-β targets are not affected (e.g. MMP13). This is the first study to show that Smad2 and Smad3 are differentially regulated during regeneration and places Smad2 at the heart of TGF-β signaling supporting the regenerative process.

Amniotic Membrane Modifies the Genetic Program Induced by TGFß, Stimulating Keratinocyte Proliferation and Migration in Chronic Wounds

BACKGROUND

Post-traumatic large-surface or deep wounds often cannot progress to reepithelialisation because they become irresponsive in the inflammatory stage, so intervention is necessary to provide the final sealing epidermis. Previously we have shown that Amniotic Membrane (AM) induced a robust epithelialisation in deep traumatic wounds.

METHODS AND FINDINGS

To better understand this phenomenon, we used keratinocytes to investigate the effect of AM on chronic wounds. Using keratinocytes, we saw that AM treatment is able to exert an attenuating effect upon Smad2 and Smad3 TGFß-induced phosphorylation while triggering the activation of several MAPK signalling pathways, including ERK and JNK1, 2. This also has a consequence for TGFß-induced regulation on cell cycle control key players CDK1A (p21) and CDK2B (p15). The study of a wider set of TGFß regulated genes showed that the effect of AM was not wide but very concrete for some genes. TGFß exerted a powerful cell cycle arrest; the presence of AM however prevented TGFß-induced cell cycle arrest. Moreover, AM induced a powerful cell migration response that correlates well with the expression of c-Jun protein at the border of the healing assay. Consistently, the treatment with AM of human chronic wounds induced a robust expression of c-Jun at the wound border.

CONCLUSIONS

The effect of AM on the modulation of TGFß responses in keratinocytes that favours proliferation together with AM-induced keratinocyte migration is the perfect match that allows chronic wounds to move on from their non-healing state and progress into epithelialization. Our results may explain why the application of AM on chronic wounds is able to promote epithelialisation.

Myb via TGFβ is required for collagen type 1 production and skin integrity

Skin integrity requires an ongoing replacement and repair orchestrated by several cell types. We previously investigated the architecture of the skin of avian myeloblastosis viral oncogene homolog (Myb) knock-out (KO) embryos and wound repair in Myb(+/)(-) mice revealing a need for Myb in the skin, attributed to fibroblast-dependent production of collagen type 1. Here, using targeted Myb deletion in keratin-14 (K14) positive cells we reveal further Myb-specific defects in epidermal cell proliferation, thickness and ultrastructural morphology. This was associated with a severe deficit in collagen type 1 production, reminiscent of that observed in patients with ichthyosis vulgaris and Ehlers-Danlos syndrome. Since collagen type 1 is a product of fibroblasts, the collagen defect observed was unexpected and appears to be directed by the loss of Myb with significantly reduced tumor growth factor beta 1 (Tgfβ-1) expression by primary keratinocytes. Our findings support a specific role for Myb in K14+ epithelial cells in the preservation of adult skin integrity and function.

High concentrations of mast cell chymase facilitate the transduction of the transforming growth factor-β1/Smads signaling pathway in skin fibroblasts

The aim of the present study was to investigate the effect of different concentrations of mast cell chymase on the transforming growth factor (TGF)-β1/Smad signaling pathway in skin fibroblasts. Cultured skin fibroblasts were treated with various concentrations of chymase for different time periods. A 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay was used to assess the rate of cell proliferation. In addition, protein expression in the fibroblasts was measured using western blot analysis. Chymase was shown to enhance the proliferation of skin fibroblasts following incubation for 48, 72 and 96 h (P<0.01). Furthermore, high concentrations of mast cell chymase were shown to enhance the mRNA and protein expression levels of TGF-β1 after long-term (≥6 h) incubation. In addition, high concentrations of mast cell chymase increased P-Smad2/3 and Smad2/3 protein expression. By contrast, low concentrations of mast cell chymase increased Smad7 protein expression. Therefore, the results demonstrated that high concentrations of mast cell chymase facilitated the transduction of the TGF-β1/Smad signaling pathway in skin fibroblasts.

Efficacy of Dragon's blood cream on wound healing: A randomized, double-blind, placebo-controlled clinical trial

The blood-red sap of Dragon's blood has been used in folk medicine for fractures, wounds, inflammation, gastrointestinal disorders, rheumatism, blood circulation dysfunctions, and cancer. Existing in vitro and in vivo bioactivity of this herb on different mechanisms of healing shows strong potential of this sap in wound healing. This clinical trial study was designated to evaluate the wound healing effect of Dragon's blood on human wounds. Sixty patients, between the ages of 14-65 years, who were referred to remove their skin tag, were assigned to this double-blind, placebo-controlled, randomized clinical trial and received either Dragon's blood or a placebo cream. They were visited on the 3rd, 5th, 7th, 10th, 14th, and 20th day of the trial to check the process of healing and to measure the wound's surface. At the end of trial, there was a significant difference in the mean duration of wound healing between the two groups (p = 0.0001). The phenolic compounds and the alkaloid taspine, which exist in Dragon's-blood resin, are probably the main reasons for the wound healing property of this plant. Being natural accessible, safe, and affordable makes Dragon's blood cream, a good choice for addition to the wound healing armamentarium. Further studies on wounds with different causes and among larger populations are suggested to ensure the effectiveness and safety of Dragon's blood.

MicroRNA-7 inhibition rescues age-associated loss of epidermal growth factor receptor and hyaluronan-dependent differentiation in fibroblasts

Age-related defects in fibroblast differentiation were previously shown to be associated with impaired hyaluronan synthase 2 (HAS2) and epidermal growth factor receptor (EGFR) function, with both required for normal fibroblast functionality. In fibroblasts, transforming growth factor-beta 1 (TGF-β1)-dependent phenotypic activation uses two distinct but co-operating pathways that involve TGF-β receptor (TGF-βR)/Smad2 activation and HA-mediated CD44-EGFR co-localization and signalling through extracellular signal-regulated kinase 1/2 (ERK1/2). The HA-mediated CD44-EGFR pathway was found to be compromised with in vitro aging, through loss of EGFR expression and a reduced movement of CD44 throughout the cellular membrane. Here, we also investigate the involvement of microRNAs (miRNAs) in age-related loss of differentiation, through investigation of miRNA-7 (miR-7) regulation of the HA-mediated EGFR-signalling pathway. The transcription of miR-7 was found to be upregulated in aged cells. In young cells, age-related loss of differentiation could be mimicked through transfection of pre-miR-7, and in aged cells, could be reversed through transfection of locked nucleic acids (LNA) targeting miR-7. Additionally, miR-7 was found to be involved in the regulation of CD44 membrane motility, which was downregulated in instances of miR-7 upregulation, and partially restorable through either miR-7 inhibition or HAS2 overexpression. The altered dynamics of CD44 in the cell membrane demonstrated a further action of miR-7 in regulating the HA-dependent CD44/EGFR pathway. We explain this novel mechanism of age-associated functional consequence due to miR-7 upregulation and demonstrate that it is reversible; highlighting miR-7 as a potential target for restoring the healing capabilities in chronic wounds in the elderly.

Preventive and therapeutic effects of Smad7 on radiation-induced oral mucositis

We report that K5.Smad7 mice, which express Smad7 transgene by a keratin-5 promoter, were resistant to radiation-induced oral mucositis, a painful oral ulceration. In addition to NF-κB activation known to contribute to oral mucositis, we found activated TGF-β signaling in oral mucositis. Smad7 dampened both pathways to attenuate inflammation, growth inhibition and apoptosis. Additionally, Smad7 promoted oral epithelial migration to close the wound. Further analyses revealed that TGF-β signaling Smads and their co-repressor CtBP1 transcriptionally repressed Rac1, and Smad7 abrogated this repression. Knocking down Rac1 in mouse keratinocytes abrogated Smad7-induced migration. Topically applying Smad7 protein with a cell permeable Tat-tag (Tat-Smad7) to oral mucosa showed preventive and therapeutic effects on radiation-induced oral mucositis in mice. Thus, we have identified novel molecular mechanisms involved in oral mucositis pathogenesis and our data suggest an alternative therapeutic strategy to block multiple pathological processes of oral mucositis.

A comparison of epithelial-to-mesenchymal transition and re-epithelialization

Wound healing and cancer metastasis share a common starting point, namely, a change in the phenotype of some cells from stationary to motile. The term, epithelial-to-mesenchymal transition (EMT) describes the changes in molecular biology and cellular physiology that allow a cell to transition from a sedentary cell to a motile cell, a process that is relevant not only for cancer and regeneration, but also for normal development of multicellular organisms. The present review compares the similarities and differences in cellular response at the molecular level as tumor cells enter EMT or as keratinocytes begin the process of re-epithelialization of a wound. Looking toward clinical interventions that might modulate these processes, the mechanisms and outcomes of current and potential therapies are reviewed for both anti-cancer and pro-wound healing treatments related to the pathways that are central to EMT. Taken together, the comparison of re-epithelialization and tumor EMT serves as a starting point for the development of therapies that can selectively modulate different forms of EMT.

Erythropoietin improves skin wound healing and activates the TGF-β signaling pathway

We could recently report that erythropoietin (EPO) accelerates skin wound healing in mice. Now, we provide insight into the molecular mechanisms of this non-hematopoietic property of EPO analyzing the transforming growth factor (TGF)-β signaling pathway. EPO receptor was found expressed in both non-wounded and wounded skin tissue as well as in fibroblasts and keratinocytes. In saline-treated control animals, wounds exhibited a significant upregulation of TGF-β1 and of α-smooth muscle actin (α-SMA) compared with non-wounded skin. EPO treatment accelerated wound epithelialization and induced mRNA expression of TGF-β1 and α-SMA. In addition, EPO significantly enhanced phosphorylation of Smad2 and Smad3 in fibroblasts and also elevated phosphorylation of Smad3 in wound tissue. Blockade of TGF-β using a neutralizing anti-TGF-β antibody attenuated EPO-induced acceleration of wound epithelialization in vivo and markedly reversed EPO effects on mRNA expression of TGF-β1 and α-SMA. In conclusion, EPO caused activation of the Smad-dependent TGF-β signaling pathway, enhanced differentiation of myofibroblasts, and accelerated skin wound closure.

The impact of Smad3 loss of function on TGF-β signaling and radiation-induced capsular contracture

BACKGROUND

Capsular contracture remains a major problem following prosthetic breast implantation, especially in patients undergoing irradiation. Recent studies suggest that such radiation injuries are a cascading process of cytokine activation, with transforming growth factor (TGF)-β acting as the "master switch." Because TGF-β signals through phosphorylation of Smad3, a plausible approach to abate TGF-β-induced capsular contracture would be to interrupt Smad3 signaling. To test this hypothesis, capsular contracture formation in wild-type and Smad3 knockout mice was compared using micro-computed tomographic and histologic examination.

METHODS

On day 0, 48 mice were implanted with bilateral silicone gel implants. Postoperatively, animals were imaged using live-scan micro-computed tomographic scanning. Animals in the radiation arm then received a 10-Gy directed radiation dose. On postoperative days 21, 28, 35, and 42, animals were imaged again. Histologic evaluation was performed at necropsy.

RESULTS

Irradiated implants in the wild-type mice demonstrated shape and contour deformation on micro-computed tomographic scanning beginning on postoperative day 21 and progressing through day 42. Conversely, micro-computed tomographic scanning of irradiated implants in knockout mice demonstrated few changes from day 0 through day 42. Corresponding histologic specimens from wild-type mice demonstrated irregular capsules composed of disorganized collagen that became thicker from day 21 to day 42. Irradiated knockout specimen maintained thin capsules from day 21 through day 42.

CONCLUSIONS

In this work, inhibiting TGF-β signaling led to a reduction in radiation-induced capsular contracture as measured by micro-computed tomographic and histologic evaluation. The results of this study suggest a promising target for the prevention of capsular contracture through the development of anti-Smad3/TGF-β-based therapies.

SMAD3 is essential for transforming growth factor-β1-induced urokinase type plasminogen activator expression and migration in transformed keratinocytes

Transforming growth factor-β1 (TGF-β1) stimulates the extracellular matrix degrading proteases expression and cell migration in order to enhance cancer cells malignancy. In the present study, we analysed the role of TGF-β1-induced Smad3 activation in the urokinase type plasminogen activator (uPA) production, as well as in cell migration and E-cadherin downregulation in transformed PDV keratinocyte cell line. TGF-β1 signalling was interfered by the chemical inhibitor of the TGF-β1-receptor 1 (ALK5), SB505124, and the specific Smad3 inhibitor, SiS3. Our results showed that TGF-β1 stimulates uPA expression directly through ALK5 activation. The inhibition of Smad3 strongly reduced the capacity of TGF-β1 to stimulate uPA expression, in parallel decreasing the uPA inhibitor plasminogen activator inhibitor type 1 (PAI-1) expression. In addition, the transient expression of dominant negative Smad3 mutant inhibited the TGF-β1-induced uPA promoter transactivation. Moreover, Smad3-/- mouse embryonic fibroblasts were refractory to the induction of uPA by TGF-β1. The inhibition of both ALK5 and Smad3 dramatically blocked the TGF-β1-stimulated E-cadherin downregulation, F-actin reorganisation and migration of PDV cells. Taken together, our results suggest that the TGF-β1-induced activation of Smad3 is the critical step for the uPA upregulation and E-cadherin downregulation, which are the key events preceding the induction of cell migration by TGF-β1 in transformed cells.

Wound macrophages as key regulators of repair: origin, phenotype, and function

Recent results call for the reexamination of the phenotype of wound macrophages and their role in tissue repair. These results include the characterization of distinct circulating monocyte populations with temporally restricted capacities to migrate into wounds and the observation that the phenotype of macrophages isolated from murine wounds partially reflects those of their precursor monocytes, changes with time, and does not conform to current macrophage classifications. Moreover, findings in genetically modified mice lacking macrophages have confirmed that these cells are essential to normal wound healing because their depletion results in retarded and abnormal repair. This mini-review focuses on current knowledge of the phenotype of wound macrophages, their origin and fate, and the specific macrophage functions that underlie their reparative role in injured tissues, including the regulation of the cellular infiltration of the wound and the production of transforming growth factor-β and vascular endothelial growth factor.

MiRNA in innate immune responses: novel players in wound inflammation

Chronic wounds represent a major and rising socioeconomic threat affecting over 6.5 million people in the United States costing in excess of US $25 billion annually. Wound healing is a physiological response to injury that is conserved across tissue systems. In humans, wounding is followed by instant response aimed at hemostasis, which in turn provides the foundation for inflammatory processes that closely follow. Inflammation is helpful and a prerequisite for healing as long as it is mounted and resolved in a timely manner. Chronic inflammation derails the healing cascade resulting in impaired wound closure. Disruption of Dicer, the RNase III enzyme that generates functional miRNAs, has a major impact on the overall immune system. Emerging studies indicate that miRNAs, especially miR-21, miR-146a/b, and miR-155, play a key role in regulating several hubs that orchestrate the inflammatory process. Direct evidence from studies addressing wound inflammation being limited, the current work represents a digest of the relevant literature that is aimed at unveiling the potential significance of miRNAs in the regulation of wound inflammation. Such treatment would help establish new paradigms highlighting a central role of miRs in the understanding and management of dysregulated inflammation as noted in conjunction with chronic wounds.

Lung tissue regeneration after induced injury in Runx3 KO mice

Runx3 is essential for normal murine lung development, and Runx3 knockout (KO) mice, which die soon after birth, exhibit alveolar hyperplasia. Wound healing, tissue repair, and regeneration mechanisms are necessary in humans for proper early lung development. Previous studies have reported that various signaling molecules, such as pErk, Tgf-beta1, CCSP, pJnk, Smad3, and HSP70 are closely related to wound healing. In order to confirm the relationship between lung defects caused by the loss of function of Runx3 and wound healing, we have localized various wound-healing markers after laser irradiation in wild-type and in Runx3 KO mouse lungs at post-natal day 1. Our results indicate that pERK, Tgf-beta1, CCSP, pJnk, and HSP70 are dramatically down-regulated by loss of Runx3 during lung wound healing. However, Smad3 is up-regulated in the Runx3 KO laser-irradiated lung region. Therefore, the lung wound-healing mechanism is inhibited in the Runx3 KO mouse, which shows abnormal lung architecture, by reduced pErk, Tgf-beta1, CCSP, pJnk, and HSP70 and by induced Smad3.

Aging fibroblasts resist phenotypic maturation because of impaired hyaluronan-dependent CD44/epidermal growth factor receptor signaling

Fibroblast differentiation into myofibroblasts is a key event during normal wound repair. We have previously demonstrated an age-related defect in this process associated with impaired synthesis of hyaluronan (HA) synthase (HAS) 2 but failed to prescribe its role in a mechanistic sense. Here we demonstrate that in addition to HAS2, there is loss of EGF receptor (EGF-R) in aged cells, and both are required for normal fibroblast functionality. Analysis of molecular events revealed that in young cells, transforming growth factor (TGF)-beta1-dependent phenotypic activation uses two distinct but cooperating pathways that involve TGF-beta receptor/Smad2 activation and EGF-mediated EGF-R/extracellular signal-regulated kinase (ERK) 1/2 signaling, and the latter is compromised with in vitro aging. Pharmacological inhibition of any of the five intermediates (TGF-beta receptor, Smad2, EGF, EGF-R, and ERK1/2) attenuated TGF-beta1 induction of alpha-smooth muscle actin. We present evidence that the HA receptor CD44 co-immunoprecipitates with EGF-R after activation by TGF-beta1. This interaction is HA-dependent because disruption of HA synthesis abrogates this association and inhibits subsequent ERK1/2 signaling. In aged fibroblasts, this association is lost with resultant suppression of ERK1/2 activation. Forced overexpression of EGF-R and HAS2 in aged cells restored TGF-beta1-mediated HA-CD44/EGF-R association and alpha-smooth muscle actin induction. Taken together, these results demonstrate that HA can serve as a signal integrator by facilitating TGF-beta1-mediated CD44-EGF-R-ERK interactions and ultimately fibroblast phenotype. We propose a model to explain this novel mechanism and the functional consequence of age-dependent dysregulation.

Age-related changes in pericellular hyaluronan organization leads to impaired dermal fibroblast to myofibroblast differentiation

We have previously demonstrated that transforming growth factor-beta1 (TGF-beta1)-mediated fibroblast-myofibroblast differentiation is associated with accumulation of a hyaluronan (HA) pericellular coat. The current study demonstrates failure of fibroblast-myofibroblast differentiation associated with in vitro aging. This is associated with attenuation of numerous TGF-beta1-dependent responses, including HA synthesis and induction of the HA synthase enzyme HAS2 and the hyaladherin tumor necrosis factor-alpha-stimulated gene 6 (TSG-6), which led to an age-related defect in pericellular HA coat assembly. Inhibition of HAS2-dependent HA synthesis by gene silencing, removal of the HA coat by hyaluronidase digestion, or gene silencing of TSG-6 or cell surface receptor CD44 led to abrogation of TGF-beta1-dependent induction of alpha-smooth muscle actin in "young" cells. This result supports the importance of HAS2-dependent HA synthesis and the HA coat during phenotypic activation. Interleukin-1beta stimulation, however, failed to promote phenotypic conversion despite coat formation. A return to basal levels of HA synthesis in aged cells by HAS2 overexpression restored TGF-beta1-dependent induction of TSG-6 and pericellular HA coat assembly. However, this did not lead to the acquisition of a myofibroblast phenotype. Coordinated induction of HAS2 and TSG-6 facilitation of pericellular HA coat assembly is necessary for TGF-beta1-dependent activation of fibroblasts, and both components of this response are impaired with in vitro aging. In conclusion, the HA pericellular coat is integral but not sufficient to correct for the age-dependent defect in phenotypic conversion.

Identification of novel Smad2 and Smad3 associated proteins in response to TGF-beta1

Transforming growth factor-beta 1 (TGF-beta1) is an important growth inhibitor of epithelial cells and insensitivity to this cytokine results in uncontrolled cell proliferation and can contribute to tumorigenesis. TGF-beta1 signals through the TGF-beta type I and type II receptors, and activates the Smad pathway via phosphorylation of Smad2 and Smad3. Since little is known about the selective activation of Smad2 versus Smad3, we set out to identify novel Smad2 and Smad3 interacting proteins in epithelial cells. A non-transformed human cell line was transduced with Myc-His(6)-Smad2 or Myc-His(6)-Smad3-expressing retrovirus and was treated with TGF-beta1. Myc-His(6)-Smad2 or Myc-His(6)-Smad3 was purified by tandem affinity purification, eluates were subject to SDS-PAGE and Colloidal Blue staining, and select protein bands were digested with trypsin. The resulting tryptic peptides were analyzed by liquid chromatography (LC) and tandem mass spectrometry (MS/MS) and the SEQUEST algorithm was employed to identify proteins in the bands. A number of proteins that are known to interact with Smad2 or Smad3 were detected in the eluates. In addition, a number of putative novel Smad2 and Smad3 associated proteins were identified that have functions in cell proliferation, apoptosis, actin cytoskeleton regulation, cell motility, transcription, and Ras or insulin signaling. Specifically, the interaction between Smad2/3 and the Cdc42 guanine nucleotide exchange factor, Zizimin1, was validated by co-immunoprecipitation. The discovery of these novel Smad2 and/or Smad3 associated proteins may reveal how Smad2 and Smad3 are regulated and/or uncover new functions of Smad2 and Smad3 in TGF-beta1 signaling.

Accelerated wound healing by smad3 antisense oligonucleotides-impregnated chitosan/alginate polyelectrolyte complex

Smad3 mediates the intracellular signaling of TGF-beta1 superfamily and plays a critical role in the cellular proliferation, differentiation and elaboration of matrix pivotal to cutaneous wound healing. Smad3 antisense oligonucleotides (ASOs) impregnated polyelectrolyte complex (PEC) containing chitosan and sodium alginate was prepared for accelerated wound healing. Physicochemical properties of PEC were characterized by zeta potential, scanning electron microscopy and bioadhesive test. Full-thickness, excisional wounds were made on the dorsum of C57BL6 mice. Then, smad3 ASOs-PEC, PEC alone, smad3 ASOs and gauze dressing were applied to determine concentration of TGF-beta1 and collagen in tissues and observe the wound contraction and histology of tissues. Zeta potentials and bioadhesive strengths of ASOs-PEC were increased as the chitosan ratio in PEC. In smad3 ASOs-PEC, the healing process suggested by wound closure and histological observation was faster than other groups because collagen contents increased and level of TGF-beta1 decreased. These results demonstrate that the smad3 ASOs-PEC composed of chitosan and sodium alginate could be applied for accelerated wound healing.

Divergent transforming growth factor-beta signaling in hepatic stellate cells after liver injury: functional effects on ECE-1 regulation

In liver wound healing, transforming growth factor-beta (TGF-beta) plays a critical role in stellate cell activation as well as signaling cascades in the fibrogenic response to injury. We postulate that the TGF-beta-dependent downstream signaling pathway may vary according to the mechanism of stellate cell activation; this study was undertaken to ascertain whether the downstream signaling pathways mediated by TGF-beta vary in different liver injury models. We measured Smad3 and MAP kinase activation after isolating stellate cells from rat livers injured by either bile duct ligation (BDL) or repeated carbon tetrachloride (CCl(4)) administration. Phospho-Smad3 was dramatically up-regulated in stellate cells after CCl(4) injury, but not after BDL-induced injury. TGF-beta signaling in stellate cells activated after BDL was mediated prominently through ERK activation, whereas activation induced by CCl(4) injury or culture led to a cross-signaling mechanism involving both Smad3 and p38. The divergent Smad signaling pathways observed appeared to be attributable to the differential regulation of the early growth response gene-1 (Egr-1), an apparent negative transcriptional factor for Smad3 in our system. In addition, inhibition of ERK activation in stellate cells from BDL-injured liver led to a decrease in expression of endothelin-converting enzyme-1, a critical regulator of endothelin-1. We speculate that TGF-beta signaling proceeds through differential signaling pathways depending on the mechanism of liver injury that leads to stellate cell activation.

Role of transforming growth factor-beta signaling pathway in pathogenesis of benign biliary stricture

AIM: To characterize the expression of members of the transforming growth factor-beta (TGF-β)/Smad/connective tissue growth factor (CTGF) signaling pathway in the tissue of benign biliary stricture, and to investigate the effect of TGF-β signaling pathway in the pathogenesis of benign biliary stricture.

METHODS: Paraffin embedded materials from 23 cases of benign biliary stricture were analyzed for members of the TGF-β/Smad/CTGF signaling pathway. TGF-β₁, TβRI, TβRII, Smad4, Smad7 and CTGF protein were detected by immunohistochemical strepto-advidinbiotin complex method, and CTGF mRNA was evaluated by hybridization in situ, while 6 cases of normal bile duct served as controls. The percentages of positive cells were counted. The correlation between TGF-β₁, Smad4 and CTGF was analyzed.

RESULTS: The positive expression ratios of TGF-β₁, TβRI, TβRII, Smad4, CTGF and CTGF mRNA in 23 cases with benign biliary stricture were 91.3%, 82.6%, 87.0%, 78.3%, 82.6% and 65.2%, respectively, significantly higher than that in 6 cases of normal bile duct respectively (vs 33.3%, 16.7%, 50.0%, 33.3%, 50.0%, 16.7%, respectively, P < 0.05). The positive expression ratio of Smad7 in cases with benign biliary stricture was 70.0%, higher than that in normal bile duct, but this difference is not statistically significant 70.0% vs 50%, P > 0.05). There was a positive correlation between positive expression of TGF-β₁, Smad4 and CTGF in cases with benign biliary stricture.

CONCLUSION: The high expression of TGF-β/Smad/CTGF signaling pathway plays an important role in the pathogenesis of benign biliary stricture.

Cellular and molecular pathology of HTS: basis for treatment

Hypertrophic scar and keloids are fibroproliferative disorders of the skin which occur often unpredictably, following trauma and inflammation that compromise cosmesis and function and commonly recur following surgical attempts for improvement. Despite decades of research in these fibrotic conditions, current non-surgical methods of treatment are slow, inconvenient and often only partially effective. Fibroblasts from these conditions are activated to produce extracellular matrix proteins such as collagen I and III, proteoglycans such as versican and biglycan and growth factors, including transforming growth factor-beta and insulin like growth factor I. However, more consistently these cells produce less remodeling enzymes including collagenase and other matrix metalloproteinases, as well as the small proteoglycan decorin which is important for normal collagen fibrillogenesis. Recently, the systemic response to injury appears to influence the local healing process whereby increases in Th2 and possibly Th3 cytokines such as IL-2, IL-4 and IL-10 and TGF-beta are present in the circulating lymphocytes in these fibrotic conditions. Finally, unique bone marrow derived cells including mesenchymal and endothelial stem cells as well as fibrocytes appear to traffic into healing wounds and influence the healing tissue. On this background, clinicians are faced with patients who require treatment and the pathophysiologic basis as currently understood is reviewed for a number of emerging modalities.

Transforming growth factor (TGF)-beta1 stimulates pulmonary fibrosis and inflammation via a Bax-dependent, bid-activated pathway that involves matrix metalloproteinase-12

Fibrosis, apoptosis, and the exaggerated production of transforming growth factor (TGF)-beta(1) are juxtaposed in a variety of pulmonary diseases including the interstitial lung diseases and asthma. In these disorders, the relationships between these responses are not well defined. In addition, the apoptosis pathways that contribute to these responses and the mechanism(s) of their contribution have not been described. We hypothesized that BH3 domain-only protein-induced apoptosis plays an important role in the pathogenesis of TGF-beta(1)-induced pulmonary responses. To test this hypothesis, we characterized the effects of transgenic TGF-beta(1) in mice with wild type (WT) and null Bax loci. To investigate the mechanisms of Bax activation and its effector functions, we also compared the effects of TGF-beta(1) in mice with WT and null Bid and matrix metalloproteinase (MMP)-12 loci, respectively. These studies demonstrate that TGF-beta(1) is a potent stimulator of Bax, Bid, and MMP-12. The studies also demonstrate that Bax and Bid play key roles in the pathogenesis of TGF-beta(1)-induced inflammation, fibrosis, and apoptosis; that TGF-beta(1) stimulates MMP-12, TIMP-1, and cathepsins and inhibits MMP-9 and p21 via Bax- and Bid-dependent mechanisms; and that TGF-beta(1)-stimulated pulmonary fibrosis is ameliorated in MMP-12-deficient animals. Finally, they demonstrate that Bax, Bid, and MMP-12 play similar roles in bleomycin-induced fibrosis, thereby highlighting the importance of this Bid-activated, Bax-mediated pathway and downstream MMP-12 in a variety of fibrogenic settings.

Expression and possible mechanism of c-ski, a novel tissue repair-related gene during normal and radiation-impaired wound healing

C-ski is a complicated regulating factor for fibroblast proliferation and an important co-repressor of Smad3. Although inhibiting Smad3 activity can markedly promote wound healing because Smad3 mediates the role of transforming growth factor-beta in inhibiting cell proliferation and inducing cell apoptosis; there has been no report on whether c-ski is expressed during wound healing and the relationship between its expression and wound healing. By establishing animal models of normal and radiation-impaired wound healing and using immunohistochemistry, in situ hybridization, and reverse transcription-polymerase chain reaction, we found that c-ski was expressed after wounding and reached its peak on day 9 and then significantly decreased. C-ski was present in all repair cells, and was especially prominent in fibroblasts. Compared with the control side, the irradiated side showed a lower expression of c-ski on postwound days 3-9, but higher on day 15, and not significantly different after the wound was healed. The expression of Smad3 was in contrast to the c-ski and cellular proliferation was similar to that of c-ski expression. The apoptosis index was significantly higher on the irradiated side on days 3-9 compared with the control side. In vitro, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide results showed that c-ski could reverse the inhibitory role of Smad3 on fibroblast proliferation. Flow cytometry analysis found that c-ski also diminished fibroblast apoptosis induced by Smad3 transfection. These results suggest that there is not only obvious expression of this regulatory protein but there is also a significant change in the levels of c-ski during wound healing. Its in vivo expression pattern and experiments in vitro suggest that c-ski may be involved in tissue repair by repressing Smad3 activity. Radiation can reduce c-ski and increase Smad3 expression, resulting in elevated Smad3 activity, resulting in diminished cell proliferation, cell apoptosis, and wound-healing delays.

Smad3 knock-out mice as a useful model to study intestinal fibrogenesis

AIM: To evaluate the possible differences in morphology and immunohistochemical expression of CD3, transforming growth factor β1(TGF-β1), Smad7, α-smooth muscle actin (α-Sma), and collagen types I-VII of small and large intestine in Smad3 null and wild-type mice.

METHODS: Ten null and ten wild-type adult mice were sacrificed at 4 mo of age and the organs (esophagus, small and large bowel, ureters) were collected for histology(hematoxylin and eosin, Masson thrichrome, silver staining), morphometry and immunohistochemistry analysis. TGF-β1 levels of intestinal tissue homogenates were assessed by ELISA.

RESULTS: No macroscopic intestinal lesions were detected both in null and wild-type mice. Histological and morphometric evaluation revealed a significant reduction in muscle layer thickness of small and large intestine in null mice as compared to wild-type mice. Immunohistochemistry evaluation showed a significant increase of CD3+T cell, TGF-β1 and Smad7 staining in the small and large intestine mucosa of Smad3 null mice as compared to wild-type mice. α-Sma and collagen I-VII staining of small and large intestine did not differ between the two groups of mice. TGF-β1 levels of colonic tissue homogenates were significantly higher in null mice than in wild-type mice. In preliminary experiments a significant reduction of TNBS-induced intestinal fibrosis was observed in null mice as compared to wild-type mice.

CONCLUSION: Smad3 null mice are a useful model to investigate the in vivo role of the TGF-β/Smad signalling pathway in intestinal inflammation and fibrosis.

17-Beta-estradiol inhibits transforming-growth-factor-beta-induced MCF-7 cell migration by Smad3-repression

Motility of malignant cells plays a crucial role for the metastasis of tumours. Both, 17-beta-estradiol and transforming growth factor-beta (TGF-beta), induce migration of MCF-7 breast cancer cells and simultaneous treatment resulted in an additive effect of the migratory response. But most interestingly, when cells were preincubated with 17-beta-estradiol, the ability of TGF-beta to evoke chemotaxis was drastically diminished. Abrogation of Smad signalling indicated that this pathway is essential for TGF-beta-mediated MCF-7 cell migration. In agreement, pretreatment of MCF-7 cells with 17-beta-estradiol resulted in a reduced phosphorylation of Smad2 and Smad3 as well as a diminished Smad2 and Smad3 gene reporter activity in response to TGF-beta. Thus, these results indicate a controversial role of 17-beta-estradiol on MCF-7 cell migration. 17-Beta-estradiol potently increases the migratory potency of MCF-7 cells, but inhibits TGF-beta-induced migration by an interaction between estrogen receptors and Smad proteins.

Smad3-null mice lack interstitial cells of Cajal in the colonic wall

BACKGROUND

Transforming growth factor-beta (TGF-beta)/Smad's signalling pathway plays a pivotal role in organogenesis, oncogenesis, inflammation, repair and fibrosis. The aim of this study was to evaluate the morphology of muscle layers and the density and distribution of interstitial cells of Cajal (ICC) in the colon of Smad3 knockout mice.

MATERIALS AND METHODS

Eighteen Smad3 wild-type mice and 12 null mice were sacrificed at age 4 months and the colons were collected for histology (Haematoxilin-Eosin, Masson thrichrome and Gomori silver staining), morphometry and immunohistochemistry (IHC) analysis. For IHC we used the c-Kit, alpha-smooth muscle actine (alpha-SMA), vimentin, desmin and neuronal cocktail (S-100, NSE, neurofilament 200) antibodies.

RESULTS

When sacrificed, 40% of the null mice showed different degrees of colon dilatation when compared with the wild-type. Histological and morphometric evaluation revealed a significant reduction in muscle layer thickness of the colon in all the null mice when compared with the wild-type. Immunohistochemistry evaluation showed a marked reduction, or even absence, of c-Kit immunoreactivity, which identifies ICC, in the colon of all the null mice, compared with the wild-type.

CONCLUSIONS

Smad3 null mice showed a marked reduction, or even absence, of ICC in the colon together with a concomitant reduction of intestinal smooth muscle layer thickness. This data could account for the colonic dilation observed in approximately 40% of the Smad3 null mice. Alteration of intestinal smooth muscle layers and ICC could also be involved in the resistance of the Smad3 null mice to develop colonic fibrosis.

TGF-beta signaling in T cells: roles in lymphoid and epithelial neoplasia

Transforming growth factor-beta (TGF-beta) plays an essential role in regulating the homeostasis of cells in the lymphoid lineage. TGF-beta signaling is not required for normal thymopoiesis, but is essential for regulating the expansion, activation, and effector function of the mature CD4+ and CD8+ T cells in the peripheral lymphoid organs and target tissues. Recent studies in both mice and humans have elucidated an important and complex role for TGF-beta in regulatory T-cell biology. Disruption of TGF-beta signaling in T cells impairs the maintenance of regulatory T cells, results in the expansion of activated effector T cells, and is associated with the production of cytokines that have major effects on cells in their environment. While autoimmunity and inflammation are the principal phenotypes associated with the abrogation of TGF-beta signaling in T cells in mice, emerging evidence now also directly links Smad-dependent TGF-beta signaling in T cells to the suppression of epithelial neoplasia. The TGF-beta receptor-activated Smad3 plays a critical role in mediating many of the inhibitory effects of TGF-beta signaling in T cells, and has now been established as an important suppressor of leukemogenesis. These studies are increasing our awareness of the many complex mechanisms through which TGF-beta signaling controls the pathogenesis of cancer.

Wound-healing studies in transgenic and knockout mice

Injury to the skin initiates a cascade of events including inflammation, new tissue formation, and tissue remodeling, that finally lead to at least partial reconstruction of the original tissue. Historically, animal models of repair have taught us much about how this repair process is orchestrated and, over recent years, the use of genetically modified mice has helped define the roles of many key molecules. Aside from conventional knockout technology, many ingenious approaches have been adopted, allowing researchers to circumvent such problems as embryonic lethality, or to affect gene function in a tissue- or temporal-specific manner. Together, these studies provide us with a growing source of information describing, to date, the in vivo function of nearly 100 proteins in the context of wound repair. This article focuses on the studies in which genetically modified mouse models have helped elucidate the roles that many soluble mediators play during wound repair, encompassing the fibroblast growth factor (FGF) and transforming growth factor-beta (TGF-beta) families and also data on cytokines and chemokines. Finally, we include a table summarizing all of the currently published data in this rapidly growing field. For a regularly updated web archive of studies, we have constructed a Compendium of Published Wound Healing Studies on Genetically Modified Mice which is avaialble at http://icbxs.ethz.ch/members/grose/woundtransgenic/home.html.

Abrogation of transforming growth factor-beta signaling by SMAD7 inhibits collagen gel contraction of human dermal fibroblasts

Human fibroproliferative disorders like hypertrophic scarring of the skin are characterized by increased contractility and excess extracellular matrix synthesis. A beneficial role of transforming growth factor (TGF)-beta in wound healing was proposed; however, chronic stimulation by this cytokine leads to fibrosis. In the present report, the intracellular TGF-beta signaling in fibroblasts derived from hypertrophic scars and normal skin was examined. In an attempt to intervene in profibrogenic TGF-beta functions, ectopic expression of Smad7 or dominant negative Smads3/4 completely inhibited contractility of scar-derived and normal fibroblasts after suspension in collagen gels. Both cell types displayed constitutive Smad2/3 phosphorylation and (CAGA)9-MLP-Luc activity with expression and phosphorylation of Smad3 being predominant in hypertrophic scar-derived fibroblasts. Down-regulation of intrinsic signaling with various TGF-beta antagonists, e.g. soluble TGF-beta receptor, latency-associated peptide, and anti-TGF-beta1 antibodies, confirms autocrine TGF-beta stimulation of both cell populations. Further, Smad7 expression inhibited alpha1 (I) collagen and alpha-smooth muscle actin expression. In summary, our data indicate that autocrine TGF-beta/Smad signaling is involved in contractility and matrix gene expression of fibroblasts from normal and hypertrophic scars. Smad7 inhibits these processes and may exert beneficial effects on excessive scar formation.

Lysophosphatidic Acid Interacts with Transforming Growth Factor-β Signaling to Mediate Keratinocyte Growth Arrest and Chemotaxis

Lysophosphatidic acid (LPA, 1-acyl-glycerol-3-phosphate) plays an important role in diverse biological responses including cell proliferation, differentiation, survival, migration, and tumor cell invasion. The most prominent source of LPA is platelets from which it is released after thrombin activation and is assumed to be an essential function of this lysophospholipid in cutaneous wound closure. Therefore, we examined the role of LPA on biological responses of keratinocytes. Although LPA potently enhances keratinocyte migration, it strongly induces growth arrest of proliferating epidermal cells. Thus, LPA possesses analogous actions to transforming growth factor-beta (TGF-beta), which is also released from degranulating platelets at wounded sites. In contrast to LPA, the intracellular signaling events of TGF-beta have been clearly identified and indicate that Smad3 is involved in chemotaxis and cell growth arrest of keratinocytes induced by this cytokine. Here we show that LPA, although it does not alter TGF-beta release is capable to activate Smad3 and results in a heteromerization with Smad4 and binding of the complex to its specific DNA-promoter elements. LPA completely fails to induce chemotaxis in Smad3-deficient cells, whereas growth inhibition is at least in part reduced. These findings indicate an essential role of Smad3 in diverse biological properties of LPA-stimulated keratinocytes.