Avian coronary endothelium is a mosaic of sinus venosus- and ventricle-derived endothelial cells in a region-specific manner.

The origin of coronary endothelial cells (ECs) has been investigated in avian species, and the results showed that the coronary ECs originate from the proepicardial organ (PEO) and developing epicardium. Genetic approaches in mouse models showed that the major source of coronary ECs is the sinus venosus endothelium or ventricular endocardium. To clarify and reconcile the differences between avian and mouse species, we examined the source of coronary ECs in avian embryonic hearts. Using an enhanced green fluorescent protein-Tol2 system and fluorescent dye labeling, four types of quail-chick chimeras were made and quail-specific endothelial marker (QH1) immunohistochemistry was performed. The developing PEO consisted of at least two cellular populations in origin, one was sinus venosus endothelium-derived inner cells and the other was surface mesothelium-derived cells. The majority of ECs in the coronary stems, ventricular free wall, and dorsal ventricular septum originated from the sinus venosus endothelium. The ventricular endocardium contributed mainly to the septal artery and a few cells to the coronary stems. Surface mesothelial cells of the PEO differentiated mainly into a smooth muscle phenotype, but a few differentiated into ECs. In avian species, the coronary endothelium had a heterogeneous origin in a region-specific manner, and the sources of ECs were basically the same as those observed in mice.

Ectopic retinoic acid signaling affects outflow tract cushion development through suppression of the myocardial Tbx2-Tgfß2 pathway.

The progress of molecular genetics has enabled us to identify the genes responsible for congenital heart malformations. However, recent studies suggest that congenital heart diseases are induced not only by mutations in certain genes, but also by abnormal maternal factors. A high concentration of maternal retinoic acid (RA), the active derivative of vitamin A, is well known as a teratogenic agent that can cause developmental defects. Our previous studies have shown that the maternal administration of RA to mice within a narrow developmental window induces outflow tract (OFT) septum defects, a condition that closely resembles human transposition of the great arteries (TGA), although the responsible factors and pathogenic mechanisms of the TGA induced by RA remain unknown. We herein demonstrate that the expression of Tbx2 in the OFT myocardium is responsive to RA, and its downregulation is associated with abnormal OFT development. We found that RA could directly downregulate the Tbx2 expression through a functional retinoic acid response element (RARE) in the Tbx2 promoter region, which is also required for the initiation of Tbx2 transcription during OFT development. Tgfb2 expression was also downregulated in the RA-treated OFT region and was upregulated by Tbx2 in a culture system. Moreover, defective epithelial-mesenchymal transition caused by the excess RA was rescued by the addition of Tgfß2 in an organ culture system. These data suggest that RA signaling participates in the Tbx2 transcriptional mechanism during OFT development and that the Tbx2-Tgfß2 cascade is one of the key pathways involved in inducing the TGA phenotype.

Expression of the Tgfß2 gene during chick embryogenesis.

We performed a comprehensive analysis of the expression of transforming growth factor (TGF) ß2 during chick embryogenesis from stage 6 to 30 (Hamburger and Hamilton, J Morphol 1951;88:49-92) using in situ hybridization. During cardiogenesis, Tgfß2 was expressed in the endothelial/mesenchymal cells of the valvulo-septal endocardial cushion tissue and in the epicardium until the end of embryogenesis. During the formation of major arteries, Tgfß2 was localized in smooth muscle progenitors but not in the vascular endothelium. During limb development, Tgfß2 was expressed in the mesenchymal cells in the presumptive limb regions at stage 16, and thereafter it was localized in the skeletal muscle progenitors. In addition, strong Tgfß2 expression was seen in the mesenchymal cells in the pharyngeal arches. Tgfß2 mRNA was also detected in other mesoderm-derived tissues, such as the developing bone and pleura. During ectoderm development, Tgfß2 was expressed in the floor plate of the neural tube, lens, optic nerve, and otic vesicle. In addition, Tgfß2 was expressed in the developing gut epithelium. Our results suggest that TGFß2 plays an important role not only in epithelial-mesenchymal interactions but also in cell differentiation and migration and cell death during chick embryogenesis. We also found that chick and mouse Tgfß2 RNA show very similar patterns of expression during embryogenesis. Chick embryos can serve as a useful model to increase our understanding in the roles of TGFß2 in cell-cell interactions, cell differentiation, and proliferation during organogenesis.

Suppression of injury-induced conjunctiva scarring by peroxisome proliferator-activated receptor gamma gene transfer in mice.

PURPOSE: To examine the effects of introduction of the adenoviral peroxisome proliferator-activated receptor (PPAR)-gamma gene on postinjury conjunctival scarring in mice. Its effects on fibrogenic reaction of cultured human subconjunctival fibroblasts (hSCFs) were also evaluated. METHODS: The effects of PPARgamma gene introduction on expression of type I collagen, fibronectin, and connective tissue growth factor (CTGF) in hSCFs were examined. A circumferential incision was made in the equatorial conjunctiva of the right eye of generally anesthetized adult C57BL/6 mice (n = 72). PPARgamma cDNA-expressing adenoviral vector was topically applied; the control eye received nonfunctioning adenoviral vector. At 2, 5, 7, and 14 days (each, n = 18), the eyes were processed for histologic or immunohistochemical examination to evaluate tissue scarring. Expression of type I collagen and growth factors was evaluated by real-time reverse transcription-polymerase chain reaction in 32 eyes from control and treatment groups. RESULTS: PPARgamma overexpression suppressed type I collagen, fibronectin, and CTGF in cultured hSCFs at the mRNA or protein level. In vivo experiments showed that PPARgamma gene introduction suppressed monocyte/macrophage invasion, generation of myofibroblasts, and mRNA upregulation of cytokines/growth factors and collagen Ialpha2 chain (Col 1A2) in healing conjunctiva. CONCLUSIONS: PPARgamma gene transfer suppresses the fibrogenic reaction in hSCFs as well as the injury-induced scarring of conjunctival tissue in mice, suggesting the effectiveness of this strategy in preventing excess scarring after filtration surgery. The mechanism may include suppression of activation of fibroblasts and reduction of macrophage invasion.

Attenuation of acute and chronic liver injury in rats by iron-deficient diet.

Oxidative stress due to iron deposition in hepatocytes or Kupffer cells contributes to the initiation and perpetuation of liver injury. The aim of this study was to clarify the association between dietary iron and liver injuries in rats. Liver injury was initiated by the administration of thioacetamide or ligation of the common bile duct in rats fed a control diet (CD) or iron-deficient diet (ID). In the acute liver injury model induced by thioacetamide, serum levels of aspartate aminotransferase and alanine aminotransferase, as well as hepatic levels of lipid peroxide and 4-hydroxynonenal, were significantly decreased in the ID group. The expression of 8-hydroxydeoxyguanosine and terminal deoxynucleotidyl transferase biotin-dUTP nick-end labeling positivity showed a similar tendency. The expression of interleukin-1beta and monocyte chemotactic protein-1 mRNA was suppressed in the ID group. In liver fibrosis induced by an 8-wk thioacetamide administration, ID suppressed collagen deposition and smooth muscle alpha-actin expression. The expressions of collagen 1A2, transforming growth factor beta, and platelet-derived growth factor receptor beta mRNA were all significantly decreased in the ID group. Liver fibrosis was additionally suppressed in the bile-duct ligation model by ID. In culture experiments, deferoxamine attenuated the activation process of rat hepatic stellate cells, a dominant producer of collagen in the liver. In conclusion, reduced dietary iron is considered to be beneficial in improving acute and chronic liver injuries by reducing oxidative stress. The results obtained in this study support the clinical usefulness of an iron-reduced diet for the improvement of liver disorders induced by chronic hepatitis C and alcoholic/nonalcoholic steatohepatitis.

Effect of overexpression of PPARgamma on the healing process of corneal alkali burn in mice.

Wound healing involves both local cells and inflammatory cells. Alkali burn of ocular surface tissue is a serious clinical problem often leading to permanent visual impairment resulting from ulceration, scarring and neovascularization during healing. Behaviors of corneal cells and inflammatory cells are orchestrated by growth factor signaling networks that have not been fully uncovered. Here we showed that adenoviral gene introduction of peroxisome proliferator-activated receptor-gamma (PPARgamma) inhibits activation of ocular fibroblasts and macrophages in vitro and also induced anti-inflammatory and anti-fibrogenic responses in an alkali-burned mouse cornea. PPARgamma overexpression suppressed upregulation of inflammation/scarring-related growth factors and matrix metalloproteinases (MMPs) in macrophages. It also suppressed expression of such growth factors and collagen Ialpha2 and myofibroblast generation upon exposure to TGFbeta1. Exogenous PPARgamma did not alter phosphorylation of Smad2, but inhibited its nuclear translocation. PPARgamma overexpression enhanced proliferation of corneal epithelial cells, but not of fibroblasts in vitro. Epithelial cell expression of MMP-2/-9 and TGFbeta1 and its migration were suppressed by PPARgamma overexpression. In vivo experiments showed that PPARgamma gene introduction suppressed monocytes/macrophages invasion and suppressed the generation of myofibroblasts, as well as upregulation of cytokines/growth factors and MMPs in a healing cornea. In vivo re-epitheliazation with basement membrane reconstruction in the healing, burned, cornea was accelerated by PPARgamma-Ad expression, although PPARgamma overexpression was considered to be unfavorable for cell migration. Together, these data suggest that overexpression of PPARgamma may represent an effective new strategy for treatment of ocular surface burns.

Endogenous TNFalpha suppression of neovascularization in corneal stroma in mice.

PURPOSE: To examine the role of tumor necrosis factor alpha (TNFalpha) in stromal neovascularization in injured cornea in vivo and in cytokine-enhanced vessel-like endothelial cell tube formation in vitro. METHODS: An in vitro model of angiogenesis was used to examine the roles of TNFalpha on tube formation by human umbilical vein endothelial cells (HUVECs) cocultured with fibroblasts on induction by transforming growth factor beta1 (TGFbeta1) and vascular endothelial growth factor (VEGF). Central cauterization was used to induce stromal neovascularization in corneas of wild-type (WT) and TNFalpha-null (Tnfalpha(-/-)) mice. At 7, 14, or 21 days of injury, experimental mice were killed, and the eyes were enucleated and subjected to histologic and immunohistochemical examination and real-time reverse transcription-polymerase chain reaction. RESULTS: HUVECs formed a vessel-like tube structure on the fibroblast feeder layer. Adding TGFbeta1, VEGF, or both augmented vessel-like tube formation by HUVECs cocultured with fibroblasts. Adding TNFalpha (5 ng/mL) completely abolished the formation of tube-like structures despite the presence or absence of TGFbeta1 or VEGF in coculture. In vivo, cauterization of the central cornea induced the formation of CD31(+) new vessels surrounding the limbus in WT mice. More prominent central stromal neovascularization accompanied by increased expression of TGFbeta1 and VEGF was found in Tnfalpha(-/-) mice compared with WT mice. CONCLUSIONS: In addition to inhibiting TGFbeta1 and VEGF expression by fibroblasts, endogenous TNFalpha may counter the induction effects of TGFbeta1 and VEGF on vascular endothelial cells and may block neovascularization.

Effect of Smad7 gene overexpression on transforming growth factor beta-induced retinal pigment fibrosis in a proliferative vitreoretinopathy mouse model.

OBJECTIVE: To determine the effects of Smad7 gene transfer in the prevention of fibrogenic responses by the retinal pigment epithelium, a major cause of proliferative vitreoretinopathy after retinal detachment, in mice. METHODS: Retinal detachment-induced proliferative vitreoretinopathy in a mouse model. Forty-eight eyes received either an adenoviral gene transfer of Smad7 or Cre recombinase gene only. The eyes were histologically analyzed. A retinal pigment epithelial cell line, ARPE-19, was used to determine whether Smad7 gene transfection suppresses the fibrogenic response to transforming growth factor (TGF) beta2 exposure. RESULTS: The Smad7 gene transfer inhibited TGF-beta2/Smad signaling in ARPE-19 cells and expression of collagen type I and TGF-beta1 but had no effect on their basal levels. In vivo Smad7 overexpression resulted in suppression of Smad2/3 signals and of the fibrogenic response to epithelial-mesenchymal transition by the retinal pigment epithelium. CONCLUSION: Smad7 gene transfer suppresses fibrogenic responses to TGF-beta2 by retinal pigment epithelial cells in vitro and in vivo. Clinical Relevance Smad7 gene transfer might be a new strategy to prevent and treat proliferative vitreoretinopathy.

Targeted and regulable expression of transgenes in hepatic stellate cells and myofibroblasts in culture and in vivo using an adenoviral Cre/loxP system to antagonise hepatic fibrosis.

BACKGROUND: Activated hepatic stellate cells (HSCs) are an attractive target for antifibrotic therapy based on their key role in extracellular matrix accumulation during liver injury. AIM: : To develop a system for regulable and cell-specific gene expression in HSCs to enable targeted delivery of therapeutic genes. METHOD: Two types of recombinant adenoviral vectors were constructed, one expressing the Cre gene under the surveillance of specific promoters and the other containing a potent expression unit that was activated by Cre recombinase-mediated recombination to remove an upstream lox-flanked "stuffer" sequence, thereby amplifying the expression of downstream transgene of interest while maintaining specificity. RESULTS: When the promoter of the collagen 1A2 gene drove Cre recombinase expression in primary quiescent rat HSC, modest green fluorescence protein (GFP) expression was observed. However, in activated HSC, the collagen promoter effectively drove Cre recombinase activity, as assessed by the increased expression of GFP. In contrast, GFP expression was barely observed when the collagen promoter was expressed in hepatocytes. HSC-specific expression of Smad7 considerably reduced the expression of type I collagen in culture and decreased fibrosis in two liver fibrosis models. Finally, to achieve targeted clearance of activated HSC in culture and in vivo, thymidine kinase was selectively expressed under the control of the collagen promoter, which conferred cell-specific killing by ganciclovir leading to reduced fibrosis. CONCLUSION: Our results show the potential utility of transcriptionally controlled gene therapy using a Cre/loxP system to ameliorate hepatic fibrosis in vivo.

Adenovirus-mediated expression of BMP-7 suppresses the development of liver fibrosis in rats.

BACKGROUND: Liver cirrhosis, which is caused by the accumulation of extracellular matrix materials, is a serious clinical problem that can progress to hepatic failure. Transforming growth factor-beta (TGFbeta) plays a pivotal role in extracellular matrix production, but bone morphogenetic protein (BMP)-7, a member of the TGFbeta superfamily, can antagonise the fibrogenic activity of TGFbeta. AIM: In this study, we examined whether adenovirus-mediated overexpression of BMP-7 (Ad-BMP-7) antagonised the effect of TGFbeta in vitro and in vivo. METHODS AND RESULTS: In primary cultured rat stellate cells and the LX-2 human stellate cell line, induction of BMP-7 by Ad-BMP-7 infection decreased the expression of collagen 1A2 mRNA and smooth muscle alpha-actin in the presence or absence of TGFbeta, via Smad 1/5/8 phosphorylation. BMP-7 triggered the mRNA expression of inhibitors of differentiation 2 (Id2) in LX-2. Although endogenous expression of BMP-7 was hardly detectable, Smad1 and Id2 overexpression increased BMP-7 expression in LX-2. A liver fibrosis model was induced by the repetitive intraperitoneal injection of thioacetamide (200 mg/kg body weight) twice per week for up to 7 weeks. In rats administered Ad-BMP-7 via the tail vein, hydroxyproline content and the areas stained by Sirius red dye in the liver were significantly reduced compared to controls. Ad-Id2 also reduced fibrosis. CONCLUSION: These data demonstrate that BMP-7, Smad 1/5/8 and Ids interact to antagonise hepatic fibrogenesis.

Loss of tumor necrosis factor alpha potentiates transforming growth factor beta-mediated pathogenic tissue response during wound healing.

Animal cornea is an avascular transparent tissue that is suitable for research on wound healing-related scarring and neovascularization. Here we show that loss of tumor necrosis factor alpha (TNFalpha) potentiates the undesirable, pathogenic response of wound healing in an alkali-burned cornea in mice. Excessive invasion of macrophages and subsequent formation of a vascularized scar tissue were much more marked in TNFalpha-null knockout (KO) mice than in wild-type mice. Such an unfavorable outcome in KO mice was abolished by Smad7 gene introduction, indicating the involvement of transforming growth factor beta or activin/Smad signaling. Bone marrow transplantation from wild-type mice normalized healing of the KO mice, suggesting the involvement of bone marrow-derived inflammatory cells in this phenomenon. Co-culture experiments showed that loss of TNFalpha in macrophages, but not in fibroblasts, augmented the fibroblast activation as determined by detection of alpha-smooth muscle actin, the hallmark of myofibroblast generation, mRNA expression of collagen Ialpha2 and connective tissue growth factor, and detection of collagen protein. TNFalpha in macrophages may be required to suppress undesirable excessive inflammation and scarring, both of which are promoted by transforming growth factor beta, and for restoration of tissue architecture in a healing alkali-burned cornea in mice.

Adenoviral gene transfer of BMP-7, Id2, or Id3 suppresses injury-induced epithelial-to-mesenchymal transition of lens epithelium in mice.

We have examined the effect of adenovirus-mediated expression of bone morphogenic protein-7 (BMP-7) and inhibitors of differentiation 2 and 3 (Id2 and Id3) on injury-induced epithelial-to-mesenchymal transition (EMT) of lens epithelium in mice. Id2 and Id3 are known to be upregulated by BMP-7 and to antagonize Smad2/3 signaling. The Cre-LoxP system adenoviral gene transfer was used. Three microliters of adenoviral solution (2 x 10(7) PFU/mul) were injected into the right lens of adult male C57BL/6 mice (n = 144) at the time of capsular injury induced using a hypodermic needle under both general and topical anesthesia. A mixture of Cre-adenovirus (Cre-Ad) and vector encoding mBMP-7, mId2, or mId3 was administered in a test group. Control lenses were treated with Cre-Ad alone. After healing intervals of 5 or 10 days, the animals were killed and then we performed histological processes or RNA extraction from the lens. RT-PCR, real-time RT-PCR, and immunohistochemistry showed expression of each introduced gene in the lens. Exogenous BMP-7 upregulated expression of Id2 and Id3 in injured lenses, and gene introduction of Id2 or Id3 also upregulated BMP-7 expression. Gene transfer of BMP-7, Id2, or Id3 delayed injury-induced EMT of the lens epithelial cells as evaluated by histology and expression patterns of alpha-smooth muscle actin and collagens in association with reduction of Smad2 COOH-terminal phosphorylation. Gene transfer of BMP-7, Id2, or Id3 delayed injury-induced EMT of lens epithelial cells and subsequent sealing of the capsular break with fibrous tissue in mice.

BMP-7 opposes TGF-beta1-mediated collagen induction in mouse pulmonary myofibroblasts through Id2.

Mesenchymal cells, primarily fibroblasts and myofibroblasts, are the principal matrix-producing cells during pulmonary fibrogenesis. Transforming growth factor (TGF)-beta signaling plays an important role in stimulating the expression of type I collagen of these cells. Bone morphogenetic protein (BMP)-7, a member of the TGF-beta superfamily, has been reported to oppose the fibrogenic activity of TGF-beta1. Here, we have addressed the effects of BMP-7 on the fibrogenic activity of pulmonary myofibroblasts. We first established cell lines from the lungs of transgenic mice harboring the COL1A2 upstream sequence fused to luciferase. They displayed a spindle shape and expressed vimentin and alpha-smooth muscle actin, but not E-cadherin. COL1A2 promoter activity was dose dependently induced by TGF-beta1, which was further augmented by adenoviral overexpression of Smad3, but was downregulated by Smad7. Under the identical condition, adenoviral overexpression of BMP-7 attenuated the TGF-beta1-dependent COL1A2 promoter activity. By immunocytochemistry, the ectopic expression of BMP-7 led to the nuclear localization of phospho-Smad1/5/8 and suppressed that of Smad3. BMP-7 suppressed the expression of mRNAs for COL1A2 and tissue inhibitor of metalloproteinase-2 while increasing those of inhibitors of differentiation (Id) 2 and 3. Ectopic expression of Id2 and Id3 was found to decrease the COL1A2 promoter activity. Finally, BMP-7 and Id2 decreased TGF-beta1-dependent collagen protein secretion. In conclusion, these data demonstrate that BMP-7 antagonizes the TGF-beta1-dependent fibrogenic activity of mouse pulmonary myofibroblastic cells by inducing Id2 and Id3.

Understanding heart development and congenital heart defects through developmental biology: a segmental approach.

ABSTRACT The heart is the first organ to form and function during development. In the pregastrula chick embryo, cells contributing to the heart are found in the postero-lateral epiblast. During the pregastrula stages, interaction between the posterior epiblast and hypoblast is required for the anterior lateral plate mesoderm (ALM) to form, from which the heart will later develop. This tissue interaction is replaced by an Activin-like signal in culture. During gastrulation, the ALM is committed to the heart lineage by endoderm-secreted BMP and subsequently differentiates into cardiomyocyte. The right and left precardiac mesoderms migrate toward the ventral midline to form the beating primitive heart tube. Then, the heart tube generates a right-side bend, and the d-loop and presumptive heart segments begin to appear segmentally: outflow tract (OT), right ventricle, left ventricle, atrioventricular (AV) canal, atrium and sinus venosus. T-box transcription factors are involved in the formation of the heart segments: Tbx5 identifies the left ventricle and Tbx20 the right ventricle. After the formation of the heart segments, endothelial cells in the OT and AV regions transform into mesenchyme and generate valvuloseptal endocardial cushion tissue. This phenomenon is called endocardial EMT (epithelial-mesenchymal transformation) and is regulated mainly by BMP and TGFbeta. Finally, heart septa that have developed in the OT, ventricle, AV canal and atrium come into alignment and fuse, resulting in the completion of the four-chambered heart. Altered development seen in the cardiogenetic process is involved in the pathogenesis of congenital heart defects. Therefore, understanding the molecular nature regulating the 'nodal point' during heart development is important in order to understand the etiology of congenital heart defects, as well as normal heart development.

A murine model of NKT cell-mediated liver injury induced by alpha-galactosylceramide/d-galactosamine.

Natural killer-T (NKT) cells are rich in the liver. However, their involvement in liver injury is not fully understood. We developed here a new murine model of NKT-cell-activation-associated liver injury, and investigated a role of tumor necrosis factor alpha (TNF-alpha) and Fas in pathogenesis. We injected intraperitoneally alpha-galactosylceramide (alpha-GalCer), an NKT-cell stimulant, into D-galactosamine (GalN)-sensitized mice. Survival rate, pathological changes of the liver, and plasma concentrations of cytokines were studied. Alpha-GalCer/GalN administration gave a lethal effect within 7 h, making pathological changes such as massive parenchymal hemorrhage, hepatocyte apoptosis, sinusoidal endothelial cell injury, and close apposition of lymphocytes to apoptotic hepatocytes. Anti-NK1.1 mAb-pretreated mice and Valpha14NKT knock out (KO) mice did not develop liver injury. Tumor necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma) were elevated at 4 h in the plasma. These cytokines were produced by hepatic lymphocytes as demonstrated by in vitro stimulation with alpha-GalCer. The lethal effect was suppressed in TNF-alpha KO mice, TNF receptor-1 KO mice, and lpr/lpr (Fas deficient) mice, whereas it was not in IFN-gamma KO mice. These results indicate that the present liver injury is characterized by parenchymal hemorrhage and hepatocyte apoptosis, and mediated by TNF-alpha secretion and direct cytotoxicity of alpha-GalCer-activated NKT cells.

Therapeutic effect of topical administration of SN50, an inhibitor of nuclear factor-kappaB, in treatment of corneal alkali burns in mice.

We evaluated the therapeutic efficacy of topical administration of SN50, an inhibitor of nuclear factor-kappaB, in a corneal alkali burn model in mice. An alkali burn was produced with 1 N NaOH in the cornea of C57BL/6 mice under general anesthesia. SN50 (10 microg/microl) or vehicle was topically administered daily for up to 12 days. The eyes were processed for histological or immunohistochemical examination after bromodeoxyuridine labeling or for semi-quantification of cytokine mRNA. Topical SN50 suppressed nuclear factor-kappaB activation in local cells and reduced the incidence of epithelial defects/ulceration in healing corneas. Myofibroblast generation, macrophage invasion, activity of matrix metalloproteinases, basement membrane destruction, and expression of cytokines were all decreased in treated corneas compared with controls. To elucidate the role of tumor necrosis factor (TNF)-alpha in epithelial cell proliferation, we performed organ culture of mouse eyes with TNF-alpha, SN50, or an inhibitor of c-Jun N-terminal kinase (JNK) and examined cell proliferation in healing corneal epithelium in TNF-alpha-/- mice treated with SN50. An acceleration of epithelial cell proliferation by SN50 treatment was found to depend on TNF-alpha/JNK signaling. In conclusion, topical application of SN50 is effective in treating corneal alkali burns in mice.

Expression of Smad7 in mouse eyes accelerates healing of corneal tissue after exposure to alkali.

Damage to the cornea from chemical burns is a serious clinical problem that often leads to permanent visual impairment. Because transforming growth factor (TGF)-beta has been implicated in the response to corneal injury, we evaluated the effects of altered TGF-beta signaling in a corneal alkali burn model using mice treated topically with an adenovirus (Ad) expressing inhibitory Smad7 and mice with a targeted deletion of the TGF-beta/activin signaling mediator Smad3. Expression of exogenous Smad7 in burned corneal tissue resulted in reduced activation of Smad signaling and nuclear factor-kappaB signaling via RelA/p65. Resurfacing of the burned cornea by conjunctival epithelium and its differentiation to cornea-like epithelium were both accelerated in Smad7-Ad-treated corneas with suppressed stromal ulceration, opacification, and neovascularization 20 days after injury. Introduction of the Smad7 gene suppressed invasion of monocytes/macrophages and expression of monocyte/macrophage chemotactic protein-1, TGF-beta1, TGF-beta2, vascular endothelial growth factor, matrix metalloproteinase-9, and tissue inhibitors of metalloproteinase-2 and abolished the generation of myofibroblasts. Although acceleration of healing of the burned cornea was also observed in mice lacking Smad3, the effects on epithelial and stromal healing were less pronounced than those in corneas treated with Smad7. Together these data suggest that overexpression of Smad7 may have effects beyond those of simply blocking Smad3/TGF-beta signaling and may represent an effective new strategy for treatment of ocular burns.

Therapeutic effects of adenoviral gene transfer of bone morphogenic protein-7 on a corneal alkali injury model in mice.

An alkali burn in the cornea is a common serious clinical problem often leading to permanent visual impairment. Since transforming growth factor-beta (TGF-beta) is involved in the response to corneal injury, we evaluated the therapeutic effects of adenoviral gene transfer of mouse bone morphogenic protein-7 (BMP-7), which has antagonistic effects on TGF-beta in tissue fibrosis. Burned cornea did not express endogenous BMP-7 mRNA and protein. Resurfacing of the burned cornea by invading conjunctival epithelium was accelerated by adenoviral introduction of BMP-7. Exogenous BMP-7 expression also suppressed myofibroblast generation, appearance of monocytes/macrophages and expression of MCP-1, TGF-betas, and collagen I alpha2 chain in the affected stroma. Ectopic BMP-7 did not suppress stromal neovascularization throughout the interval studied and also did not reduce VEGF mRNA expression at Day 10. Ectopic BMP-7 in burned corneal tissue resulted in activation of Smad1/5/8 signaling and partial suppression of the phospho-Smad2 signal. These data suggest that overexpression of BMP-7 is an effective strategy for treatment of ocular alkali burns.

Transient adenoviral gene transfer of Smad7 prevents injury-induced epithelial-mesenchymal transition of lens epithelium in mice.

We examined the effect of adenovirus-mediated transient expression of Smad7, an inhibitory Smad in TGFbeta/activin signaling, on injury-induced epithelial-mesenchymal transition (EMT) of lens epithelium in mice. A volume of 3 microl of adenoviral solution was injected into the right lens of adult male C57BL/6 mice (n=56) at the time of capsular injury made using a hypodermic needle under general anesthesia. A mixture of recombinant adenovirus carrying CAG promoter-driven Cre (Cre adv) and mouse Smad7 complementary DNA (Smad7 adv) was administered to induce Smad7 expression, while control lenses were treated with Cre adv alone. After healing intervals of 2, 3, 5, and 10 days, animals were killed 2 h after labeling with bromodeoxyuridine (BrdU) and eyes were processed for histology. During healing, marked expression of Smad7 was observed in lens epithelial cells in the Smad7 adv group with loss of nuclear translocation of Smads2/3, while little Smad7 and abundant nuclear Smads2/3 were seen in cells in the Cre adv group. Lens epithelial cells in the Cre adv control group exhibited a fibroblastic appearance at days 5 and 10 and the capsular break was sealed with fibrous tissue, while Smad7 adv-treated cells around the capsular break retained their epithelial morphology and the break was not sealed. Expression of snail mRNA, and alpha-smooth muscle actin, lumican, and collagen VI proteins, markers of EMT, was observed in control-treated eyes, but not in cells of the Smad7 adv group at day 5 with minimal expression at day 10. Additionally, cell proliferation increased in epithelium infected with Smad7 adv consistent with suppression of injury-induced upregulation of TGFbeta1 in epithelium. We conclude that gene transfer of Smad7 in mice prevents injury-induced EMT of lens epithelial cells and sealing of the capsular break with fibrous tissue.