Interference with transforming growth factor-beta/ Smad3 signaling results in accelerated healing of wounds in previously irradiated skin

Lupus-prone NZM2328 mice exhibit enhanced UV-induced myeloid cell recruitment and activation in a type I interferon dependent manner

Though the exact causes of systemic lupus erythematosus (SLE) remain unknown, exposure to ultraviolet (UV) light is one of the few well-known triggers of cutaneous inflammation in SLE. However, the precise cell types which contribute to the early cutaneous inflammatory response in lupus, and the ways that UV dosing and interferons modulate these findings, have not been thoroughly dissected. Here, we explore these questions using the NZM2328 spontaneous murine model of lupus. In addition, we use iNZM mice, which share the NZM2328 background but harbor a whole-body knockout of the type I interferon (IFN) receptor, and wild-type BALB/c mice. 10-13-week-old female mice of each strain were treated with acute (300 mJ/cm2 x1), chronic (100 mJ/cm2 daily x5 days), or no UVB, and skin was harvested and processed for bulk RNA sequencing and flow cytometry. We identify that inflammatory pathways and gene signatures related to myeloid cells - namely neutrophils and monocyte-derived dendritic cells - are a shared feature of the acute and chronic UVB response in NZM skin greater than iNZM and wild-type skin. We also verify recruitment and activation of these cells by flow cytometry in both acutely and chronically irradiated NZM and WT mice and demonstrate that these processes are dependent on type I IFN signaling. Taken together, these data indicate a skewed IFN-driven inflammatory response to both acute and chronic UVB exposure in lupus-prone skin dominated by myeloid cells, suggesting both the importance of type I IFNs and myeloid cells as therapeutic targets for photosensitive patients and highlighting the risks of even moderate UV exposure in this patient population.

An Experimental Model of Proton-Beam-Induced Radiation Dermatitis In Vivo

Radiation dermatitis (RD) is one of the most common side effects of radiation therapy. However, to date, there is a lack of both specific treatments for RD and validated experimental animal models with the use of various sources of ionizing radiation (IR) applied in clinical practice. The aim of this study was to develop and validate a model of acute RD induced using proton radiation in mice. Acute RD (Grade 2-4) was obtained with doses of 30, 40, and 50 Gy, either with or without depilation. The developed model of RD was characterized by typical histological changes in the skin after irradiation. Moreover, the depilation contributed to a skin histology alteration of the irradiated mice. The assessment of animal vital signs indicated that there was no effect of proton irradiation on the well-being or general condition of the animals. This model can be used to develop effective therapeutic agents and study the pathogenesis of radiation-induced skin toxicity, including that caused by proton irradiation.

Identification of potential molecular mechanisms and candidate drugs for radiotherapy- and chemotherapy-induced mucositis

BACKGROUND

Radiotherapy-induced oral mucositis (RIOM) and chemotherapy-induced oral mucositis (CIOM) are common complications in cancer patients, leading to negative clinical manifestations, reduced quality of life, and unsatisfactory treatment outcomes.

OBJECTIVE

The present study aimed to identify potential molecular mechanisms and candidate drugs by data mining.

METHODS

We obtained a preliminary list of genes associated with RIOM and CIOM. In-depth information on these genes was explored by functional and enrichment analyses. Then, the drug-gene interaction database was used to determine the interaction of the final enriched gene list with known drugs and analyze the drug candidates.

RESULTS AND CONCLUSION

This study identified 21 hub genes that may play an important role in RIOM and CIOM, respectively. Through our data mining, bioinformatics survey, and candidate drug selection, TNF, IL-6, and TLR9 could play an important role in disease progression and treatment. In addition, eight candidate drugs (olokizumab, chloroquine, hydroxychloroquine, adalimumab, etanercept, golimumab, infliximab, and thalidomide) were selected by the drug-gene interaction literature search additionally, as candidates for treating RIOM and CIOM.

In Vitro, Ex Vivo, and In Vivo Approaches for Investigation of Skin Scarring: Human and Animal Models

Significance: The cutaneous repair process naturally results in different types of scarring that are classified as normal or pathological. Affected individuals are often affected from an esthetic, physical (functional), and psychosocial perspective. The distinct nature of scarring in humans, particularly the formation of pathological scars, makes the study of skin scarring a challenge for researchers in this area. Several established experimental models exist for studying scar formation. However, the increasing development and validation of newly emerging models have made it possible to carry out studies focused on different variables that influence this unique process. Recent Advances: Experimental models such as in vitro, ex vivo, and in vivo models have obtained different degrees of success in the reproduction of the scar formation in its native milieu and true environment. These models also differ in their ability to elucidate the molecular, cellular, and structural mechanisms involved in scarring, as well as for testing new agents and approaches for therapies. The models reviewed here, including cells derived from human skin and in vivo animal models, have contributed to the advancement of skin scarring research. Critical Issues and Future Directions: The absence of experimental models that faithfully reproduce the typical characteristics of the different types of human skin scars makes the improvement of validated models and the establishment of new ones a critical unmet need. The fields of wound healing research combined with tissue engineering have offered newer alternatives for experimental studies with the potential to provide clinically useful knowledge about scar formation.

Intraoperative Intradermal Application of Stromal Vascular Fraction into the Abdominal Suture Line: Histological Analysis of Abdominal Scar Tissue

BACKGROUND

Stem cell therapy is a promising new approach to wound healing. Stromal vascular fraction is a heterogeneous collection of cells, including adipose-derived stem cells, which are traditionally isolated using a manual collagenase-based technique. To our knowledge, this is the first human study that histologically assesses the potential of intraoperative intradermal injection of stromal vascular fraction on skin regeneration.

METHODS

In this controlled study, 20 patients undergoing deep inferior epigastric perforator flap breast reconstruction and bilateral flank liposuction were included. Stromal vascular fraction was injected intradermally into one side of the abdominal suture line, while the other side served as a control. Outcome measures included analysis of stromal vascular fraction by flow cytometry, histological analysis of scar tissue, and scar photography.

RESULTS

Cell yield for application and cell viability were 55.9 ± 28.5 × 10⁶ and 75.1% ± 14.5%, respectively. Age and body mass index were positively correlated with the number of cells for application and adipose-derived stem cells. Mean vascular density, elastic fiber content, collagen maturity (scar index), epidermal thickness, and number of rete ridges all showed higher values on the treated side. Furthermore, the injected number of adipose-derived stem cells and pericytes positively correlated with vascular density.

CONCLUSIONS

It is safe to speculate that intradermal stromal vascular fraction injection at the beginning of the healing process increases vascular density, collagen maturity and organization, elastic fiber content, epidermal thickness, epidermal-dermal anchoring of the scarring skin and is therefore responsible for improved skin regeneration. It is a viable and safe method that can be used as an adjunctive treatment in plastic surgery procedures where suboptimal wound healing is anticipated.

LEVEL OF EVIDENCE IV

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

TGF-β1 mediates pathologic changes of secondary lymphedema by promoting fibrosis and inflammation

Background

Secondary lymphedema is a common complication of cancer treatment, and previous studies have shown that the expression of transforming growth factor‐beta 1 (TGF‐β1), a pro‐fibrotic and anti‐lymphangiogenic growth factor, is increased in this disease. Inhibition of TGF‐β1 decreases the severity of the disease in mouse models; however, the mechanisms that regulate this improvement remain unknown.

Methods

Expression of TGF‐β1 and extracellular matrix molecules (ECM) was assessed in biopsy specimens from patients with unilateral breast cancer‐related lymphedema (BCRL). The effects of TGF‐β1 inhibition using neutralizing antibodies or a topical formulation of pirfenidone (PFD) were analyzed in mouse models of lymphedema. We also assessed the direct effects of TGF‐β1 on lymphatic endothelial cells (LECs) using transgenic mice that expressed a dominant‐negative TGF‐β receptor selectively on LECs (LEC^DN‐RII).

Results

The expression of TGF‐β1 and ECM molecules is significantly increased in BCRL skin biopsies. Inhibition of TGF‐β1 in mouse models of lymphedema using neutralizing antibodies or with topical PFD decreased ECM deposition, increased the formation of collateral lymphatics, and inhibited infiltration of T cells. In vitro studies showed that TGF‐β1 in lymphedematous tissues increases fibroblast, lymphatic endothelial cell (LEC), and lymphatic smooth muscle cell stiffness. Knockdown of TGF‐β1 responsiveness in LEC^DN‐RII resulted in increased lymphangiogenesis and collateral lymphatic formation; however, ECM deposition and fibrosis persisted, and the severity of lymphedema was indistinguishable from controls.

Conclusions

Our results show that TGF‐β1 is an essential regulator of ECM deposition in secondary lymphedema and that inhibition of this response is a promising means of treating lymphedema.

Urinary Bladder Matrix Improves Irradiated Wound Healing in a Murine Model

ABSTRACT

Radiation skin damage is associated with chronic wounds and poor healing. Existing localized treatment modalities have limited benefit. Therefore, there has been increased interest in biologically based solutions. In this study, we aimed to determine the effect of topical urinary bladder matrix (UBM) on chronic irradiated skin wounds using an established murine model. Our findings demonstrated that topical urinary bladder matrix significantly accelerated the healing of irradiated wounds on day 7 (P = 0.0216), day 14 (P = 0.0140), and day 21 (P = 0.0393). Histologically, urinary bladder matrix treatment was associated with higher-quality reorganization and reepithelialization of wounds, an increased density of myofibroblasts (P = 0.0004), and increased collagen deposition (P < 0.0001). In addition, quantitative real-time polymerase chain reaction data demonstrated decreased expression of profibrotic mediators (P = 0.0049). We conclude that urinary bladder matrix may be a useful, noninvasive, adjunctive therapy for the treatment of chronic irradiated skin wounds.

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.

FLASH Proton Pencil Beam Scanning Irradiation Minimizes Radiation-Induced Leg Contracture and Skin Toxicity in Mice

Simple Summary

Dose and efficacy of radiation therapy are limited by the toxicity to normal tissue adjacent to the treated tumor region. Recently, ultra-high dose rate radiotherapy (FLASH radiotherapy) has shown beneficial reduction of normal tissue damage while preserving similar tumor efficacy with electron, photon and scattered proton beam irradiation in preclinical models. Proton therapy is increasingly delivered by pencil beam scanning (PBS) technology, and we therefore set out to test PBS FLASH radiotherapy on normal tissue toxicity and tumor control in vivo in mouse using a clinical proton delivery system. This validation of the FLASH normal tissue-sparing hypothesis with a clinical delivery system provides supporting data for PBS FLASH radiotherapy and its potential role in improving radiotherapy outcomes.

Abstract

Ultra-high dose rate radiation has been reported to produce a more favorable toxicity and tumor control profile compared to conventional dose rates that are used for patient treatment. So far, the so-called FLASH effect has been validated for electron, photon and scattered proton beam, but not yet for proton pencil beam scanning (PBS). Because PBS is the state-of-the-art delivery modality for proton therapy and constitutes a wide and growing installation base, we determined the benefit of FLASH PBS on skin and soft tissue toxicity. Using a pencil beam scanning nozzle and the plateau region of a 250 MeV proton beam, a uniform physical dose of 35 Gy (toxicity study) or 15 Gy (tumor control study) was delivered to the right hind leg of mice at various dose rates: Sham, Conventional (Conv, 1 Gy/s), Flash60 (57 Gy/s) and Flash115 (115 Gy/s). Acute radiation effects were quantified by measurements of plasma and skin levels of TGF-β1 and skin toxicity scoring. Delayed irradiation response was defined by hind leg contracture as a surrogate of irradiation-induced skin and soft tissue toxicity and by plasma levels of 13 different cytokines (CXCL1, CXCL10, Eotaxin, IL1-beta, IL-6, MCP-1, Mip1alpha, TNF-alpha, TNF-beta, VEGF, G-CSF, GM-CSF and TGF- β1). Plasma and skin levels of TGF-β1, skin toxicity and leg contracture were all significantly decreased in FLASH compared to Conv groups of mice. FLASH and Conv PBS had similar efficacy with regards to growth control of MOC1 and MOC2 head and neck cancer cells transplanted into syngeneic, immunocompetent mice. These results demonstrate consistent delivery of FLASH PBS radiation from 1 to 115 Gy/s in a clinical gantry. Radiation response following delivery of 35 Gy indicates potential benefits of FLASH versus conventional PBS that are related to skin and soft tissue toxicity.

Adipose-Derived Stem Cells Promote Intussusceptive Lymphangiogenesis by Restricting Dermal Fibrosis in Irradiated Tissue of Mice

Currently, there is no definitive treatment for lymphatic disorders. Adipose-derived stem cells (ADSCs) have been reported to promote lymphatic regeneration in lymphedema models, but the mechanisms underlying the therapeutic effects remain unclear. Here, we tested the therapeutic effects of ADSC transplantation on lymphedema using a secondary lymphedema mouse model. The model was established in C57BL/6J mice by x-irradiation and surgical removal of the lymphatic system in situ. The number of lymphatic vessels with anti-lymphatic vessel endothelial hyaluronan receptor 1 (LYVE-1) immunoreactivity increased significantly in mice subjected to transplantation of 7.5 × 10⁵ ADSCs. X-irradiation suppressed lymphatic vessel dilation, which ADSC transplantation could mitigate. Proliferative cell nuclear antigen staining showed increased lymphatic endothelial cell (LEC) and extracellular matrix proliferation. Picrosirius red staining revealed normal collagen fiber orientation in the dermal tissue after ADSC transplantation. These therapeutic effects were not related to vascular endothelial growth factor (VEGF)-C expression. Scanning electron microscopy revealed structures similar to the intraluminal pillar during intussusceptive angiogenesis on the inside of dilated lymphatic vessels. We predicted that intussusceptive lymphangiogenesis occurred in lymphedema. Our findings indicate that ADSC transplantation contributes to lymphedema reduction by promoting LEC proliferation, improving fibrosis and dilation capacity of lymphatic vessels, and increasing the number of lymphatic vessels via intussusceptive lymphangiogenesis.

KLF15 is a protective regulatory factor of heart failure induced by pressure overload

The aim of the present study was to investigate the protective effect of Kruppel‑like factor 15 (KLF15) overexpression on heart failure (HF) induced by left ventricular (LV) pressure overload in mice. Wild‑type (WT) mice and cardiac‑specific KLF15‑overexpressed transgenic (TG) mice were selected as research subjects, and an LV pressure overload model was constructed by ascending aortic constriction surgery. Changes in cardiac morphology and function, and ultrastructure and molecular expression were observed via M‑mode echocardiography, histological and immunohistochemical staining, ELISA and western blotting at 2 and 6 weeks of LV overload. WT and TG mice subjected to 2 weeks of overload displayed adaptive LV hypertrophy characterized by ventricular thickness, cardiomyocyte size, ejection fraction and fractional shortening of heart‑lung weight ratio and KLF15, and increases in vascular endothelial growth factor (VEGF) expression without other pathological changes. WT mice subjected to 6 weeks of overload displayed enlargement of the LV chamber, severe interstitial remodeling, and HW/LW, cardiac capillary and heart function decline, accompanied by downregulated expression of KLF15 and VEGF, and upregulated expression of connective tissue growth factor, phosphorylated p38 (p‑p38) and phosphorylated Smad3 (p‑Smad3). In contrast, TG mice exhibited improved resistance to 6 weeks of overload and a slighter molecular expression response compared with WT mice. KLF15 was revealed to be a critical factor regulating the expression of CTGF, VEGF, p‑p38 and p‑Smad3, and could alleviate the progression from adaptive LV hypertrophy to decompensatory cardiac insufficiency.

Fat Chance: The Rejuvenation of Irradiated Skin

Radiotherapy (RT) helps cure and palliate thousands of patients with a range of malignant diseases. A major drawback, however, is the collateral damage done to tissues surrounding the tumor in the radiation field. The skin and subcutaneous tissue are among the most severely affected regions. Immediately following RT, the skin may be inflamed, hyperemic, and can form ulcers. With time, the dermis becomes progressively indurated. These acute and chronic changes cause substantial patient morbidity, yet there are few effective treatment modalities able to reduce radiodermatitis. Fat grafting is increasingly recognized as a tool able to reverse the fibrotic skin changes and rejuvenate the irradiated skin. This review outlines the current progress toward describing and understanding the cellular and molecular effects of fat grafting in irradiated skin. Identification of the key factors involved in the pathophysiology of fibrosis following RT will inform therapeutic interventions to enhance its beneficial effects.

Radiation-induced skin reactions: mechanism and treatment

Radiotherapy (RT) is a major treatment for malignant tumors. The latest data show that >70% of patients with malignant tumors need RT at different periods. Skin changes can be experienced by up to 95% of patients who underwent RT. Inflammation and oxidative stress (OS) have been shown to be generally associated with radiation-induced skin reactions (RISRs). Inflammatory response and OS interact and promote each other during RISRs. Severe skin reactions often have a great impact on the progress of RT. The treatment of RISRs is particularly critical because advanced RT technology can also lead to skin reactions. RISRs are classified into acute and chronic reactions. The treatment methods for acute RISRs include steroid treatment, creams, ointments, and hydrocolloid dressings, depending on the reaction grading. Chronic RISRs includes chronic ulcerations, telangiectasias, and fibrosis of the skin, and advanced treatments such as mesenchymal stem cells, hyperbaric oxygen therapy, superoxide dismutase, and low-intensity laser therapy can be considered. Here, we review and summarize the important mechanisms that cause RISRs as well as the standard and advanced treatments for RISRs.

Dynamic expression of SMAD3 is critical in osteoblast differentiation of PDMCs

Human pluripotent stem cells have the potential assist in the identification of genes involved in mammalian development. The human placenta is considered a repository of stem cells, termed placenta‑derived multipotent cells (PDMCs), which are able to differentiate into cells with an osteoblastic phenotype. This plasticity of PDMCs maybe applied clinically to the understanding of osteogenesis and osteoporosis. In the presentstudy, osteoblasts were generated by culturing PDMCs in osteogenic medium. Reverse transcription quantitative polymerase chain reactionand the degree of osteoblast calcification were used to evaluate the efficacy of osteogenesis. The results suggestedthat the expression of mothers against decapentaplegic homolog 3 (SMAD3) increased in the initial stages of osteogenic differentiation but decreased in the later stages. However, osteogenesis was inhibitedwhen the PDMCs overexpressed SMAD3 throughout the differentiation period. In addition, the rate of osteogenic differentiation was decreased when SMAD3 signaling was impaired. In conclusion, SMAD3 serves an important role in osteoblast differentiation and bone formation in a time‑dependent manner. The data from the present study indicate that arapid increase in SMAD3 expression is crucial for osteogenesis and suggest a role for PDMCs in the treatment of patients with osteoporosis.

A Novel Small-Animal Model of Irradiated, Implant-Based Breast Reconstruction

BACKGROUND

There is currently a need for a clinically relevant small-animal model for irradiated, implant-based breast reconstruction. Present models are inadequate in terms of suboptimal location of expander placement and mode of radiation delivery, correlating poorly with the human clinical scenario. The authors hypothesized that by delivering fractionated radiation and placing an expander under the scalp of the animal, they would achieve soft-tissue changes histologically analogous to those seen in human irradiated, implant-based breast reconstruction.

METHODS

This study consisted of 11 immunocompetent, hairless rats divided into three groups as follows: untreated control (n = 3), tissue-expanded scalps (n = 4), and fractionated irradiation plus tissue expansion of the scalp (n = 4). At the completion of the experiment for each group, skin tissue samples were analyzed histologically for vascularity, epidermal and dermal thickness, and collagen fiber alignment or scar formation.

RESULTS

Expanded rat epidermis was significantly thicker and dermis was more vascular than nonexpanded skin. The authors observed a greater degree of collagen fiber alignment in the expanded group compared with nonexpanded skin. The combination of irradiation and expansion resulted in significant dermal thinning, vascular depletion, and increased scar formation compared with expanded skin alone.

CONCLUSIONS

The authors describe a novel small-animal model for irradiated, implant-based breast reconstruction where histologic analysis shows structural changes in the skin consistent with known effects of radiation therapy and expansion in human skin. This model represents a significant improvement from previous ones and, as such, holds the potential to be used to test new therapeutic agents to improve clinical outcomes.

TGF-β signaling promotes tumor vasculature by enhancing the pericyte-endothelium association

Background

The breast cancer microenvironment promotes tumor vascularization through the complex interactions involving tumor-associated fibroblasts (TAFs). Emerging data indicate that TAFs increase production and signaling by TGF-β cytokines, while the role of TGF-β signaling in the regulation of tumor blood vessels is not fully understood. The current study presents evidence that TAFs enhance the organization of tumor blood capillaries, and TGF-β signaling plays an important role in this response.

Methods

Tumor vascularization was studied in xenograft models of breast carcinoma cells, alone and in combination with fibroblasts. TGF-β signaling in breast cancer cells was modulated by expression of kinase-inactive TGFBR1-K232R (dnTGFBR1) or constitutive-active TGFBR1-T204D (caTGFBR1) receptor mutants. The architecture of tumor blood capillaries was assessed by immune-histochemical analysis of endothelium and pericytes. The role of TGF-β-Smad signaling in fibronectin expression was examined using adenoviral transduction of signaling components.

Results

Our studies revealed that TAFs significantly increase the lumen size of blood microvessels. Inactivation of TGF-β signaling in tumor cells by dnTGFBR1 reduced the microvessel density and lumen sizes, decreasing tumor growth. In contrast, caTGFBR1-tumors exhibited greater vessel density and lumen sizes. Tumors with inactive dnTGFBR1 showed lower amounts of TAFs, while caTGFBR1 increased amounts of TAFs compared to the control. Inspection of pericytes and endothelial cells in tumor vasculature revealed that TAFs enhanced vessel coverage by pericytes, vascular cells supporting capillaries. This effect was impaired in dnTGFBR1-tumors, whereas active caTGFBR1 enhanced the association of pericytes with endothelium. Accordingly, dnTGFBR1-tumors exhibited the presence of hemorrhages, a sign of fragile blood vessels. Biochemical analysis showed that TGFBR1-SMAD signaling up-regulates fibronectin, a prominent regulator of endothelium-pericyte interactions.

Conclusions

The current study indicates that tumor-fibroblast crosstalk enhances tumor vascularization by increasing the pericyte-endothelium association via a mechanism involving the TGFβ-fibronectin axis. The tumor-fibroblast model represents a useful system for dissecting the complex interactions governing tumor angiogenesis and developing new approaches to therapeutic targeting tumor vasculature.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-4587-z) contains supplementary material, which is available to authorized users.

Amelioration of Head and Neck Radiation-Induced Mucositis and Distant Marrow Suppression in Fanca-/- and Fancg-/- Mice by Intraoral Administration of GS-Nitroxide (JP4-039)

Squamous cell carcinomas of the head and neck are appearing with increased frequency in both marrow transplanted and non-transplanted Fanconi anemia (FA) patients. FA patients commonly display radiosensitivity of epithelial tissues, complicating effective radiotherapy. Fancd2^-/- mice (C57BL/6J and 129/Sv background) demonstrate epithelial tissue sensitivity to single-fraction or fractionated irradiation to the head and neck and distant marrow suppression (abscopal effect), both ameliorated by intraoral administration of the mitochondrial-targeted antioxidant, GS-nitroxide, JP4-039. We now report that mice of two other FA genotypes, Fancg^-/- (B6) and the most prevalent human genotype Fanca^-/- (129/Sv), also demonstrate: 1. reduced longevity of hematopoiesis in long-term bone marrow cultures; 2. radiosensitivity of bone marrow stromal cell lines; and 3. head and neck radiation-induced severe mucositis and abscopal suppression of distant marrow hematopoiesis. Intraoral administration of JP4-039/F15, but not non-mitochondrial-targeted 4-amino-Tempo/F15 or F15 alone, prior to each radiation treatment ameliorated both local and abscopal radiation effects. Head and neck irradiated TGF-β-resistant SMAD3^-/- (129/Sv) mice and double-knockout SMAD3^-/- Fancd2^-/- (129/Sv) mice treated daily with TGF-β receptor antagonist, LY364947, still displayed abscopal bone marrow suppression, implicating a non-TGF-β mechanism. Thus, amelioration of both local normal tissue radiosensitivity and distant marrow suppression by intraoral administration of JP4-039 in Fancg^-/- and Fanca^-/- mice supports a clinical trial of this locally administered normal tissue radioprotector and mitigator during head and neck irradiation in FA patients.

Topical Fibronectin Improves Wound Healing of Irradiated Skin

Wound healing is significantly delayed in irradiated skin. To better understand global changes in protein expression after radiation, we utilized a reverse phase protein array (RPPA) to identify significant changes in paired samples of normal and irradiated human skin. Of the 210 proteins studied, fibronectin was the most significantly and consistently downregulated in radiation-damaged skin. Using a murine model, we confirmed that radiation leads to decreased fibronectin expression in the skin as well as delayed wound healing. Topically applied fibronectin was found to significantly improve wound healing in irradiated skin and was associated with decreased inflammatory infiltrate and increased angiogenesis. Fibronectin treatment may be a useful adjunctive modality in the treatment of non-healing radiation wounds.

Radiotherapy-Induced Skin Reactions Induce Fibrosis Mediated by TGF-β1 Cytokine

Purpose:

This study aimed to investigate radiation-induced lesions on the skin in an experimental animal model. Methods and Materials: Cutaneous wounds were induced in Wistar rats by 4 MeV energy electron beam irradiation, using a dose rate of 240 cGy/min, for 3 different doses (10 Gy, 40 Gy, and 60 Gy). The skin was observed 5, 10, and 25 days (D) after ionizing radiation exposition.

Results:

Infiltrate inflammatory process was observed in D5 and D10, for the 40 Gy and 60 Gy groups, and a progressive increase of transforming growth factor β1 is associated with this process. It could also be noted a mischaracterization of collagen fibers at the high-dose groups.

Conclusion:

It was observed that the lesions caused by ionizing radiation in rats were very similar to radiodermatitis in patients under radiotherapy treatment.

Advances in Knowledge:

This study is important to develop strategies to prevent radiation-induced skin reactions.

Unraveling biophysical interactions of radiation pneumonitis in non-small-cell lung cancer via Bayesian network analysis

BACKGROUND

In non-small-cell lung cancer radiotherapy, radiation pneumonitis≥grade 2 (RP2) depends on patients' dosimetric, clinical, biological and genomic characteristics.

METHODS

We developed a Bayesian network (BN) approach to explore its potential for interpreting biophysical signaling pathways influencing RP2 from a heterogeneous dataset including single nucleotide polymorphisms, micro RNAs, cytokines, clinical data, and radiation treatment plans before and during the course of radiotherapy. Model building utilized 79 patients (21 with RP2) with complete data, and model testing used 50 additional patients with incomplete data. A developed large-scale Markov blanket approach selected relevant predictors. Resampling by k-fold cross-validation determined the optimal BN structure. Area under the receiver-operating characteristics curve (AUC) measured performance.

RESULTS

Pre- and during-treatment BNs identified biophysical signaling pathways from the patients' relevant variables to RP2 risk. Internal cross-validation for the pre-BN yielded an AUC=0.82 which improved to 0.87 by incorporating during treatment changes. In the testing dataset, the pre- and during AUCs were 0.78 and 0.82, respectively.

CONCLUSIONS

Our developed BN approach successfully handled a high number of heterogeneous variables in a small dataset, demonstrating potential for unraveling relevant biophysical features that could enhance prediction of RP2, although the current observations would require further independent validation.

Topical tacrolimus for the treatment of secondary lymphedema

Secondary lymphedema, a life-long complication of cancer treatment, currently has no cure. Lymphedema patients have decreased quality of life and recurrent infections with treatments limited to palliative measures. Accumulating evidence indicates that T cells play a key role in the pathology of lymphedema by promoting tissue fibrosis and inhibiting lymphangiogenesis. Here using mouse models, we show that topical therapy with tacrolimus, an anti-T-cell immunosuppressive drug, is highly effective in preventing lymphedema development and treating established lymphedema. This intervention markedly decreases swelling, T-cell infiltration and tissue fibrosis while significantly increasing formation of lymphatic collaterals with minimal systemic absorption. Animals treated with tacrolimus have markedly improved lymphatic function with increased collecting vessel contraction frequency and decreased dermal backflow. These results have profound implications for lymphedema treatment as topical tacrolimus is FDA-approved for other chronic skin conditions and has an established record of safety and tolerability.

Secondary lymphedema is a debilitating disease with no cure. Here the authors show that topical application of an FDA-approved anti-T cell drug tacrolimus potently prevents development and alleviates pathologic changes of established lymphedema in mice, suggesting a new treatment for human patients.

Characterization of Smad3 knockout mouse derived skin cells

TGF-β plays an important role in skin wound healing process, in which Smad3 acts as a signaling molecule. Smad3 knockout mice exhibit enhanced wound healing and less inflammatory process, but the intrinsic properties of the mouse derived skin cells are generally unexplored. The purpose of this study is to characterize the biological behavior of skin cells derived from Smad3 knockout mice and thus to define the mechanism of this particular wound healing process. Keratinocytes and dermal fibroblasts were harvested from the skin of Smad3 knockout (Smad3 KO) and wild-type (WT) mice and in vitro cultured for one and two passages for various experiments. The results showed that KO mouse serum contained significantly higher levels of TGF-β1 and lower level of IL-6 and IL-10 than WT mouse serum (p < 0.05), which were also supported by the same findings of more TGF-β1 and less IL-6 and IL-10 in the supernatant of cultured KO dermal fibroblasts than those of WT cells (p < 0.05). At gene levels, IL-6, IL-10, and TGF-β1 were significantly less expressed in KO fibroblasts than in WT fibroblasts (p < 0.05). In addition, KO dermal fibroblasts also exhibited stronger migration and proliferation potentials than WT fibroblasts (p < 0.05). Moreover, both KO fibroblasts and keratinocytes showed higher colony-forming efficiency than WT counterparts with significant difference (p < 0.05). These findings indicate that both systemic factors and intrinsic properties of skin cells contribute to enhanced wound healing and less inflammatory reaction observed in Smad3 knock-out mice.

NORMAL TISSUE REACTIONS TO CHRONIC RADIATION EXPOSURE IN MAN

This paper presents an overview of radiobiological dependences governing the occurrence of tissue (organ) reactions that determine the outcomes of chronic exposure to low-LET ionizing radiation (IR) in humans. The mechanisms involved in the development of tissue reactions (TRs) to long-term exposures to IR and radioadaptation are considered. The overview describes the reactions of the haematopoietic, immune, nervous, reproductive and endocrine systems, lungs, skin and crystalline lens to chronic radiation exposure, which are of fundamental importance in view of radiation protection. It is shown that the individual's physiological tissue (organ) reserve, and also that induced by radiation exposure at low-dose rates are of great significance in the context of TR development.

Transition from inflammation to proliferation: a critical step during wound healing

The ability to rapidly restore the integrity of a broken skin barrier is critical and is the ultimate goal of therapies for hard-to-heal-ulcers. Unfortunately effective treatments to enhance healing and reduce scarring are still lacking. A deeper understanding of the physiology of normal repair and of the pathology of delayed healing is a prerequisite for the development of more effective therapeutic interventions. Transition from the inflammatory to the proliferative phase is a key step during healing and accumulating evidence associates a compromised transition with wound healing disorders. Thus, targeting factors that impact this phase transition may offer a rationale for therapeutic development. This review summarizes mechanisms regulating the inflammation-proliferation transition at cellular and molecular levels. We propose that identification of such mechanisms will reveal promising targets for development of more effective therapies.

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.

Endothelial perturbations and therapeutic strategies in normal tissue radiation damage

Most cancer patients are treated with radiotherapy, but the treatment can also damage the surrounding normal tissue. Radiotherapy side-effects diminish patients’ quality of life, yet effective biological interventions for normal tissue damage are lacking. Protecting microvascular endothelial cells from the effects of irradiation is emerging as a targeted damage-reduction strategy. We illustrate the concept of the microvasculature as a mediator of overall normal tissue radiation toxicity through cell death, vascular inflammation (hemodynamic and molecular changes) and a change in functional capacity. Endothelial cell targeted therapies that protect against such endothelial cell perturbations and the development of acute normal tissue damage are mostly under preclinical development. Since acute radiation toxicity is a common clinical problem in cutaneous, gastrointestinal and mucosal tissues, we also focus on damage in these tissues.

SMAD3 gene variant is a risk factor for recurrent surgery in patients with Crohn's disease

BACKGROUND AND AIMS

More than 80% of Crohn's disease (CD) patients will require surgery. Surgery is not curative and rates of re-operation are high. Identification of genetic variants associated with repeat surgery would allow risk stratification of patients who may benefit from early aggressive therapy and/or post-operative prophylactic treatment.

METHODS

CD patients who had at least one CD-related bowel resection were identified from the Prospective Registry in IBD Study at Massachusetts General Hospital (PRISM). The primary outcome was surgical recurrence. Covariates and potential interactions were assessed using the Cox proportional hazard model. Kaplan-Meier curves for time to surgical recurrence were developed for each genetic variant and analyzed with the log-rank test.

RESULTS

194 patients were identified who had at least 1 resection. Of these, 69 had two or more resections. Clinical predictors for repeat surgery were stricturing (HR 4.18, p=0.022) and penetrating behavior (HR 3.97, p=0.024). Smoking cessation was protective for repeat surgery (HR 0.45, p=0.018). SMAD3 homozygosity for the risk allele was also independently associated with increased risk of repeat surgery (HR 4.04, p=0.001). NOD2 was not associated with increased risk of surgical recurrence.

CONCLUSION

Stricturing and penetrating behavior were associated with increased risk of surgical recurrence, while smoking cessation was associated with a decreased risk. A novel association between SMAD3 and increased risk of repeat operation and shorter time to repeat surgery was observed. This finding is of particular interest as SMAD3 may represent a new therapeutic target specifically for prevention of post-surgical disease recurrence.

Mesenchymal stem cells inhibit cutaneous radiation-induced fibrosis by suppressing chronic inflammation

Exposure to ionizing radiation (IR) can result in the development of cutaneous fibrosis, for which few therapeutic options exist. We tested the hypothesis that bone marrow-derived mesenchymal stem cells (BMSC) would favorably alter the progression of IR-induced fibrosis. We found that a systemic infusion of BMSC from syngeneic or allogeneic donors reduced skin contracture, thickening, and collagen deposition in a murine model. Transcriptional profiling with a fibrosis-targeted assay demonstrated increased expression of interleukin-10 (IL-10) and decreased expression of IL-1β in the irradiated skin of mice 14 days after receiving BMSC. Similarly, immunoassay studies demonstrated durable alteration of these and several additional inflammatory mediators. Immunohistochemical studies revealed a reduction in infiltration of proinflammatory classically activated CD80(+) macrophages and increased numbers of anti-inflammatory regulatory CD163(+) macrophages in irradiated skin of BMSC-treated mice. In vitro coculture experiments confirmed that BMSC induce expression of IL-10 by activated macrophages, suggesting polarization toward a regulatory phenotype. Furthermore, we demonstrated that tumor necrosis factor-receptor 2 (TNF-R2) mediates IL-10 production and transition toward a regulatory phenotype during coculture with BMSC. Taken together, these data demonstrate that systemic infusion of BMSC can durably alter the progression of radiation-induced fibrosis by altering macrophage phenotype and suppressing local inflammation in a TNF-R2-dependent fashion.

Mechanisms of cellular fibrosis associated with cancer regimen-related toxicities

Fibrosis is a common, persistent and potentially debilitating complication of chemotherapy and radiation regimens used for the treatment of cancer. The molecular mechanisms underlying fibrosis have been well studied and reveal overall processes that are largely ubiquitous. However, it is important to note that although the processes are similar, they result in cellular phenotypes that are highly tissue specific. These tissue specific differences may present opportunities for therapeutic interventions to prevent or treat this often irreversible condition. Data generated from animal models of cancer therapy-related tissue toxicities have revealed that the signaling pathways involved in fibrosis are the same as those involved in the normal injury response and include the transforming growth factor β superfamily and a range of pro-inflammatory cytokines. The critical difference between normal wound healing and fibrosis development appears to be, that in fibrosis, these signaling pathways escape normal cellular regulation. As a result, an injury state is maintained and processes involved in normal healing are usurped. There are a few, if any, therapeutics that effectively prevent or treat fibrosis in patients. Consequently, cancer survivors may be chronically plagued with a variety of life-altering fibrosis-related symptoms. Uncovering the signaling pathways that drive cellular fibrosis is paramount to the development of specific therapeutics that will mitigate this potentially devastating condition.

Smad3 deficiency ameliorates hepatic fibrogenesis through the expression of senescence marker protein-30, an antioxidant-related protein

Smad3 is a key mediator of the transforming growth factor (TGF)-β1 signaling pathway that plays central role in inflammation and fibrosis. In present study, we evaluated the effect of Smad3 deficiency in Smad3-/- mice with carbon tetrachloride (CCl4)-induced liver fibrosis. The animals were received CCl4 or olive oil three times a week for 4 weeks. Histopathological analyses were performed to evaluate the fibrosis development in the mice. Alteration of protein expression controlled by Smad3 was examined using a proteomic analysis. CCl4-induced liver fibrosis was rarely detected in Smad3-/- mice compared to Smad3+/+. Proteomic analysis revealed that proteins related to antioxidant activities such as senescence marker protein-30 (SMP30), selenium-binding proteins (SP56) and glutathione S-transferases (GSTs) were up-regulated in Smad3-/- mice. Western blot analysis confirmed that SMP30 protein expression was increased in Smad3-/- mice. And SMP30 levels were decreased in CCl4-treated Smad3+/+ and Smad3-/- mice. These results indicate that Smad3 deficiency influences the proteins level related to antioxidant activities during early liver fibrosis. Thus, we suggest that Smad3 deteriorate hepatic injury by inhibitor of antioxidant proteins as well as mediator of TGF-β1 signaling.

Antimicrobial effects of coprisin on wounds infected with Staphylococcus aureus in rats

Antimicrobial peptides (AMPs) are naturally produced antibiotics that play important roles in host defense mechanisms. These proteins are found in variety of animal and plant species. The antibiotic effects of AMPs are gaining attention for use in human medicine. In this study, the antimicrobial effects of coprisin, a novel AMP isolated from the dung beetle (Copris tripartitus), were evaluated. The peptide was used to treat rats with wounds infected with Staphylococcus aureus. Coprisin accelerated wound closure both grossly and microscopically compared with the untreated group. Additionally, treatment with this peptide decreased phosphorylated-Smad2/3 (p-Smad2/3) levels, a downstream factor of the transforming growth factor-β signaling pathway which is believed to inhibit reepithelization, in the nucleus and cytoplasm of regenerating cells. Moreover, increased cell populations and angiogenesis were observed in lesions treated with coprisin, suggesting that this peptide promotes wound healing via its antimicrobial activity against S. aureus. Our results demonstrated that coprisin is a potential therapeutic agent that can possibly replace traditional antibiotics and overcome microbial resistance.

Bone morphogenetic protein signaling suppresses wound-induced skin repair by inhibiting keratinocyte proliferation and migration

Bone morphogenetic protein (BMP) signalling plays a key role in the control of skin development and postnatal remodelling by regulating keratinocyte proliferation, differentiation and apoptosis. To study the role of BMPs in wound-induced epidermal repair, we used transgenic mice overexpressing the BMP downstream component Smad1 under the control of a K14 promoter as an in vivo model, as well as ex vivo and in vitro assays. K14-caSmad1 mice exhibited retarded wound healing associated with significant inhibition of proliferation and increased apoptosis in healing wound epithelium. Furthermore, microarray and qRT-PCR analyses revealed decreased expression of a number of cytoskeletal/cell motility-associated genes including wound-associated keratins (Krt16, Krt17) and Myo5a, in the epidermis of K14-caSmad1 mice versus wild-type controls during wound healing. BMP treatment significantly inhibited keratinocyte migration ex vivo, and primary keratinocytes of K14-caSmad1 mice showed retarded migration compared to wild-type controls. Finally, siRNA-mediated silencing of Bmpr-1B in primary mouse keratinocytes accelerated cell migration and was associated with increased expression of Krt16, Krt17 and Myo5a compared to controls. Thus, this study demonstrates that BMPs inhibit keratinocyte proliferation, cytoskeletal organization and migration in regenerating skin epithelium during wound healing, and raises a possibility for using BMP antagonists for the management of chronic wounds.

Smad7 inhibits TGF-β1-induced MCP-1 upregulation through a MAPK/p38 pathway in rat peritoneal mesothelial cells

PURPOSE

The TGF-β1/Smad signaling pathway is subject to inhibition by Smad7. High expression of Smad7 in the peritoneum of rats can delay and attenuate not only peritoneal fibrosis, but also monocyte infiltration into the peritoneum. The aim of this study was to investigate the anti-inflammatory mechanism of Smad7 in peritoneal fibrosis.

METHODS

Rat peritoneal mesothelial cells were stimulated with TGF-β1, and the expression of MCP-1 protein and mRNA was measured. Furthermore, the expression of MCP-1 was determined following inhibition of TGF-β/Smad or p38 signaling using Smad7 transfection or SB203580 (10 μmol/L), respectively. The effect of exogenous Smad7 and SB203580 on activation of the TGF-β/Smad and p38 signaling pathways was also studied.

RESULTS

TGF-β1 significantly upregulated the expression of MCP-1 at both the protein and mRNA level in a time-dependent manner. Exogenous Smad7 and SB203580 markedly inhibited TGF-β1-induced MCP-1 expression. Moreover, high expression of exogenous Smad7 not only inhibited phosphorylation of Smad2 and Smad3, but also diminished the level of phosphorylated p38. However, SB203580 had no effect on the phosphorylation of Smad2 and Smad3.

CONCLUSIONS

TGF-β1 exhibits pro-inflammatory effects through the upregulation of MCP-1 in peritoneal fibrosis. Smad7 inhibits TGF-β1 induced MCP-1 upregulation through a MAPK/p38-dependent pathway.

Inhibition of radiation-induced skin fibrosis with imatinib

PURPOSE

Dermal fibrosis is a disabling late toxicity of radiotherapy. Several lines of evidence suggest that overactive signaling via the Platelet-derived growth factor receptor-beta (PDGFR-β) and V-abl Abelson murine leukemia viral oncogene homolog 1 (cAbl) may be etiologic factors in the development of radiation-induced fibrosis. We tested the hypothesis that imatinib, a clinically available inhibitor of PDGFR-β, Mast/stem cell growth factor receptor (c-kit) and cAbl, would reduce the severity of dermal fibrosis in a murine model.

MATERIALS AND METHODS

The right hind legs of female C3H/HeN mice were exposed to 35 Gy of X-rays. Cohorts of mice were maintained on chow formulated with imatinib 0.5 mg/g or control chow for the duration of the experiment. Bilateral hind limb extension was measured serially to assess fibrotic contracture. Immunohistochemistry and biochemical assays were used to evaluate the levels of collagen and cytokines implicated in radiation-induced fibrosis.

RESULTS

Imatinib treatment significantly reduced hind limb contracture and dermal thickness after irradiation. Immunohistochemical studies demonstrated a substantial reduction in PDGFR-β phosphorylation. We also observed reduced Transforming Growth factor-β (TGF-β) and collagen expression in irradiated skin of imatinib-treated mice, suggesting that imatinib may suppress the fibrotic process by interrupting cross-talk between these pathways.

CONCLUSIONS

Taken together, these results support that imatinib may be a useful agent in the prevention and treatment of radiation-induced dermal fibrosis.

IL-1 generated subsequent to radiation-induced tissue injury contributes to the pathogenesis of radiodermatitis

Radiation injury in the skin causes radiodermatitis, a condition in which the skin becomes inflamed and the epidermis can break down. This condition causes significant morbidity and if severe it can be an independent factor that contributes to radiation mortality. Radiodermatitis is seen in some settings of radiotherapy for cancer and is also of concern as a complication post-radiation exposure from accidents or weapons, such as a "dirty bomb". The pathogenesis of this condition is incompletely understood. Here we have developed a murine model of radiodermatitis wherein the skin is selectively injured by irradiation with high-energy electrons. Using this model we showed that the interleukin-1 (IL-1) pathway plays a significant role in the development of radiodermatitis. Mice that lack either IL-1 or the IL-1 receptor developed less inflammation and less severe pathological changes in their skin, especially at later time-points. These findings suggest that IL-1 pathway may be a potential therapeutic target for reducing the severity of radiodermatitis.

The TGF-β/Smad repressor TG-interacting factor 1 (TGIF1) plays a role in radiation-induced intestinal injury independently of a Smad signaling pathway

Despite advances in radiation delivery protocols, exposure of normal tissues during the course of radiation therapy remains a limiting factor of cancer treatment. If the canonical TGF-β/Smad pathway has been extensively studied and implicated in the development of radiation damage in various organs, the precise modalities of its activation following radiation exposure remain elusive. In the present study, we hypothesized that TGF-β1 signaling and target genes expression may depend on radiation-induced modifications in Smad transcriptional co-repressors/inhibitors expressions (TGIF1, SnoN, Ski and Smad7). In endothelial cells (HUVECs) and in a model of experimental radiation enteropathy in mice, radiation exposure increases expression of TGF-β/Smad pathway and of its target gene PAI-1, together with the overexpression of Smad co-repressor TGIF1. In mice, TGIF1 deficiency is not associated with changes in the expression of radiation-induced TGF-β pathway-related transcripts following localized small intestinal irradiation. In HUVECs, TGIF1 overexpression or silencing has no influence either on the radiation-induced Smad activation or the Smad3-dependent PAI-1 overexpression. However, TGIF1 genetic deficiency sensitizes mice to radiation-induced intestinal damage after total body or localized small intestinal radiation exposure, demonstrating that TGIF1 plays a role in radiation-induced intestinal injury. In conclusion, the TGF-β/Smad co-repressor TGIF1 plays a role in radiation-induced normal tissue damage by a Smad-independent mechanism.

Genetic deficiency of Smad3 protects the kidneys from atrophy and interstitial fibrosis in 2K1C hypertension

Although the two-kidney, one-clip (2K1C) model is widely used as a model of human renovascular hypertension, mechanisms leading to the development of fibrosis and atrophy in the cuffed kidney and compensatory hyperplasia in the contralateral kidney have not been defined. Based on the well-established role of the transforming growth factor (TGF)-β signaling pathway in renal fibrosis, we tested the hypothesis that abrogation of TGF-β/Smad3 signaling would prevent fibrosis in the cuffed kidney. Renal artery stenosis (RAS) was established in mice with a targeted disruption of exon 2 of the Smad3 gene (Smad3 KO) and wild-type (WT) controls by placement of a polytetrafluoroethylene cuff on the right renal artery. Serial pulse-wave Doppler ultrasound assessments verified that blood flow through the cuffed renal artery was decreased to a similar extent in Smad3 KO and WT mice. Two weeks after surgery, systolic blood pressure and plasma renin activity were significantly elevated in both the Smad3 KO and WT mice. The cuffed kidney of WT mice developed renal atrophy (50% reduction in weight after 6 wk, P < 0.0001), which was associated with the development of interstitial fibrosis, tubular atrophy, and interstitial inflammation. Remarkably, despite a similar reduction of renal blood flow, the cuffed kidney of the Smad3 KO mice showed minimal atrophy (9% reduction in weight, P = not significant), with no significant histopathological alterations (interstitial fibrosis, tubular atrophy, and interstitial inflammation). We conclude that abrogation of TGF-β/Smad3 signaling confers protection against the development of fibrosis and atrophy in RAS.

Halofuginone down-regulates Smad3 expression and inhibits the TGFbeta-induced expression of fibrotic markers in human corneal fibroblasts

PURPOSE

Due to its ability to disrupt transforming growth factor beta (TGF-β) signaling, halofuginone has been successfully used to treat various fibrotic disorders. Here we investigated the antifibrotic potential of halofuginone in human corneal fibroblasts.

METHODS

Human corneal fibroblasts were isolated from human donor corneas for in vitro experiments. TGF-β was used to stimulate pro-fibrotic responses from corneal fibroblasts under halofuginone treatment. The expression of alpha smooth muscle actin (α-SMA) and fibronectin was analyzed by western blots. Phalloidin toxin was used to stain cultures for stress fiber assemblies. Quantitative reverse transcription PCR (qRT-PCR) and immunostaining were used to analyze the expression of type I collagen mRNA and protein, respectively. The expression of Smad2, Smad3, phospho-Smad2, and phospho-Smad3 was determined by western blots.

RESULTS

Halofuginone was well tolerated by human corneal fibroblasts up to 10 ng/ml as demonstrated by a cell viability assay. At this concentration, TGF-β-induced expression of the fibrotic markers α-SMA, fibronectin, and type I collagen was significantly reduced. Interestingly, under our experimental conditions, halofuginone treatment led to reduced protein expression of Smad3, which was both dose- and time-dependent.

CONCLUSIONS

Our results suggest that halofuginone may exert its antifibrotic effects in the cornea via a novel molecular mechanism and may be used as an antifibrotic agent for corneal fibrosis treatment.

Myostatin-null mice exhibit delayed skin wound healing through the blockade of transforming growth factor-β signaling by decorin

Myostatin (Mstn) is a secreted growth and differentiation factor that belongs to the transforming growth factor-β (TGF-β) superfamily. Mstn has been well characterized as a regulator of myogenesis and has been shown to play a critical role in postnatal muscle regeneration. Herein, we report for the first time that Mstn is expressed in both epidermis and dermis of murine and human skin and that Mstn-null mice exhibited delayed skin wound healing attributable to a combination of effects resulting from delayed epidermal reepithelialization and dermal contraction. In epidermis, reduced keratinocyte migration and protracted keratinocyte proliferation were observed, which subsequently led to delayed recovery of epidermal thickness and slower reepithelialization. Furthermore, primary keratinocytes derived from Mstn-null mice displayed reduced migration capacity and increased proliferation rate as assessed through in vitro migration and adhesion assays, as well as bromodeoxyuridine incorporation and Western blot analysis. Moreover, in dermis, both fibroblast-to-myofibroblast transformation and collagen deposition were concomitantly reduced, resulting in a delayed dermal wound contraction. These decreases are due to the inhibition of TGF-β signaling. In agreement, the expression of decorin, a naturally occurring TGF-β suppressor, was elevated in Mstn-null mice; moreover, topical treatment with TGF-β1 protein rescued the impaired skin wound healing observed in Mstn-null mice. These observations highlight the interplay between TGF-β and Mstn signaling pathways, specifically through Mstn regulation of decorin levels during the skin wound healing process. Thus we propose that Mstn agonists might be beneficial for skin wound repair.

Interactions between β-catenin and transforming growth factor-β signaling pathways mediate epithelial-mesenchymal transition and are dependent on the transcriptional co-activator cAMP-response element-binding protein (CREB)-binding protein (CBP)

Interactions between transforming growth factor-β (TGF-β) and Wnt are crucial to many biological processes, although specific targets, rationale for divergent outcomes (differentiation versus block of epithelial proliferation versus epithelial-mesenchymal transition (EMT)) and precise mechanisms in many cases remain unknown. We investigated β-catenin-dependent and transforming growth factor-β1 (TGF-β1) interactions in pulmonary alveolar epithelial cells (AEC) in the context of EMT and pulmonary fibrosis. We previously demonstrated that ICG-001, a small molecule specific inhibitor of the β-catenin/CBP (but not β-catenin/p300) interaction, ameliorates and reverses pulmonary fibrosis and inhibits TGF-β1-mediated α-smooth muscle actin (α-SMA) and collagen induction in AEC. We now demonstrate that TGF-β1 induces LEF/TCF TOPFLASH reporter activation and nuclear β-catenin accumulation, while LiCl augments TGF-β-induced α-SMA expression, further confirming co-operation between β-catenin- and TGF-β-dependent signaling pathways. Inhibition and knockdown of Smad3, knockdown of β-catenin and overexpression of ICAT abrogated effects of TGF-β1 on α-SMA transcription/expression, indicating a requirement for β-catenin in these Smad3-dependent effects. Following TGF-β treatment, co-immunoprecipitation demonstrated direct interaction between endogenous Smad3 and β-catenin, while chromatin immunoprecipitation (ChIP)-re-ChIP identified spatial and temporal regulation of α-SMA via complex formation among Smad3, β-catenin, and CBP. ICG-001 inhibited α-SMA expression/transcription in response to TGF-β as well as α-SMA promoter occupancy by β-catenin and CBP, demonstrating a previously unknown requisite TGF-β1/β-catenin/CBP-mediated pro-EMT signaling pathway. Clinical relevance was shown by β-catenin/Smad3 co-localization and CBP expression in AEC of IPF patients. These findings suggest a new therapeutic approach to pulmonary fibrosis by specifically uncoupling CBP/catenin-dependent signaling downstream of TGF-β.

Ionizing radiation: the good, the bad, and the ugly

Skin changes caused by ionizing radiation have been scientifically documented since 1902. Ionizing radiation is a widely accepted form of treatment for various types of cancer. Despite the technological advances, radiation skin injury remains a significant problem. This injury, often referred to as radiation dermatitis, occurs in about 95% of patients receiving radiation therapy for cancer, and ranges in severity from mild erythema to moist desquamation and ulceration. Ionizing radiation is not only a concern for cancer patients, but also a public health concern because of the potential for and reality of a nuclear and/or radiological event. Recently, the United States has increased efforts to develop medical countermeasures to protect against radiation toxicities from acts of bioterrorism, as well as cancer treatment. Management of radiation dermatitis would improve the therapeutic benefit of radiation therapy for cancer and potentially the mortality expected in any "dirty bomb" attack. Currently, there is no effective treatment to prevent or mitigate radiation skin injury. This review summarizes "the good, the bad, and the ugly" of current and evolving knowledge regarding mechanisms of and treatments for radiation skin injury.

BMP-7/TGF-β1 signalling in myoblasts: components involved in signalling and BMP-7-dependent blockage of TGF-β-mediated CTGF expression

We and others have recently described the antagonistic role of Bone morphogenetic protein-7 (BMP-7) in TGF-β signalling and myogenic differentiation. To specify the underlying mechanism(s), we here analysed the expression and function of the individual components mediating TGF-β1 and BMP-7 responses. We found that BMP-7 at a concentration of 25 ng/ml induces signalling exclusively via ALK2 and ALK3 leading to the activation of Smad1 and Smad5 and subsequent expression of Id proteins. In contrast, low doses of TGF-β1 (0.1 ng/ml) lead to an exclusive activation of ALK5 and phosphorylation of Smad2 and Smad3 that regulate specific target genes including connective tissue growth factor (CTGF). CTGF is rapidly induced by TGF-β1 already 1h after stimulation and reduced by BMP-7 application. Smad1/Smad5 or Id1/2 overexpression reduced the TGF-β1-mediated expression of CTGF. However, although siRNA-mediated knock down of Alk2/3 or Smad1/5 counteracts the BMP-7 effect on basal CTGF expression there was no consistent reversion of the observed BMP-7 effect on TGF-β1-mediated CTGF expression. Moreover, ALK5 inhibition using the SB431542 inhibitor significantly affected CTGF expression only at later time points whereas ERK1/2 inhibition completely abrogated CTGF expression. These findings point towards a regulatory role of BMP-7 that relies on modulation of Mitogen-activated protein kinases rather than mechanisms that are exclusively driven by differential Smad activation.