Localization of TGF-beta signaling intermediates Smad2, 3, 4, and 7 in developing and mature human and mouse kidney

Ghrelin is involved in regulating the progression of Echinococcus Granulosus-infected liver lesions through suppression of immunoinflammation and fibrosis

BACKGROUND

Cystic Echinococcosis (CE) is a zoonotic disease causing fibrosis and necrosis of diseased livers caused by infection with Echinococcus granulosus (E.g). There is evidence that E.g is susceptible to immune escape and tolerance when host expression of immunoinflammation and fibrosis is suppressed, accelerating the progression of CE. Ghrelin has the effect of suppressing immunoinflammation and fibrosis, and whether it is involved in regulating the progression of E.g-infected liver lesions is not clear.

METHODS

Serum and hepatic Ghrelin levels were observed in E.g-infected mice (4, 12 and 36 weeks) and compared with healthy control groups. Co-localization analysis is performed between protein expression of Ghrelin in and around the hepatic lesions of E.g-infected 12-week mice and protein expression of different hepatic histiocytes by mIHC. HepG2 cells and protoscoleces (PSCs) protein were co-cultured in vitro, as well as PSCs were alone in vitro, followed by exogenously administered of Ghrelin and its receptor blocker, [D-Lys3]-GHRP-6, to assess their regulatory effects on immunoinflammation, fibrosis and survival rate of PSCs.

RESULTS

Serum Ghrelin levels were increased in E.g-infected 4- and 12-week mice, and reduced in 36-week mice. E.g-infected mice consistently recruited Ghrelin in and around the hepatic lesions, which was extremely strongly co-localized with the protein expression of hepatic stellate cells (HSCs), T cells and the TGF-β1/Smad3 pathway. The secretion of Ghrelin was increased with increasing concentrations of PSCs protein in HepG2 cells culture medium. Moreover, Ghrelin could significantly inhibit the secretion of IL-2, INF-γ and TNF-α, as well as the expression of Myd88/NF-κB and TGF-β1/Smad3 pathway protein, and promoted the secretion of IL-4 and IL-10. Blocking Ghrelin receptor could significantly inhibit PSCs growth in in vitro experiment.

CONCLUSION

Ghrelin is highly expressed in the early stages of hepatic E.g infection and may be involved in regulating the progression of liver lesions by suppression immunoinflammation and fibrosis.

Ghrelin regulating liver activity and its potential effects on liver fibrosis and Echinococcosis

Ghrelin widely exists in the central nervous system and peripheral organs, and has biological activities such as maintaining energy homeostasis, regulating lipid metabolism, cell proliferation, immune response, gastrointestinal physiological activities, cognition, memory, circadian rhythm and reward effects. In many benign liver diseases, it may play a hepatoprotective role against steatosis, chronic inflammation, oxidative stress, mitochondrial dysfunction, endoplasmic reticulum stress and apoptosis, and improve liver cell autophagy and immune response to improve disease progression. However, the role of Ghrelin in liver Echinococcosis is currently unclear. This review systematically summarizes the molecular mechanisms by which Ghrelin regulates liver growth metabolism, immune-inflammation, fibrogenesis, proliferation and apoptosis, as well as its protective effects in liver fibrosis diseases, and further proposes the role of Ghrelin in liver Echinococcosis infection. During the infectious process, it may promote the parasitism and survival of parasites on the host by improving the immune-inflammatory microenvironment and fibrosis state, thereby accelerating disease progression. However, there is currently a lack of targeted in vitro and in vivo experimental evidence for this viewpoint.

The origin and role of the renal stroma

The postnatal kidney is predominantly composed of nephron epithelia with the interstitial components representing a small proportion of the final organ, except in the diseased state. This is in stark contrast to the developing organ, which arises from the mesoderm and comprises an expansive stromal population with distinct regional gene expression. In many organs, the identity and ultimate function of an epithelium is tightly regulated by the surrounding stroma during development. However, although the presence of a renal stromal stem cell population has been demonstrated, the focus has been on understanding the process of nephrogenesis whereas the role of distinct stromal components during kidney morphogenesis is less clear. In this Review, we consider what is known about the role of the stroma of the developing kidney in nephrogenesis, where these cells come from as well as their heterogeneity, and reflect on how this information may improve human kidney organoid models.

Transforming Growth Factor-β1/Smad Signaling in Glomerulonephritis and Its Association with Progression to Chronic Kidney Disease

INTRODUCTION

Transforming growth factor-β1 (TGF-β1) is a multifunctional cytokine, with diverse roles in fibrosis and inflammation, which acts through Smad signaling in renal pathology. We intended to investigate the expression of TGF-β/Smad signaling in glomerulonephritis (GN) and to assess its role as risk factor for progression to chronic kidney disease (CKD).

METHODS

We evaluated the immunohistochemical expression of TGF-β1, phosphorylated Smad3 (pSmad3), and Smad7 semiquantitatively and quantitatively using computerized image analysis program in different compartments of 50 renal biopsies with GN, and the results were statistically analyzed with clinicopathological parameters. We also examined the associations among their expressions, the impact of their co-expression, and their role in progression to CKD.

RESULTS

TGF-β1 expression correlated positively with segmental glomerulosclerosis (p= 0.025) and creatinine level at diagnosis (p = 0.002), while pSmad3 expression with interstitial inflammation (p = 0.024). In glomerulus, concomitant expressions of high Smad7 and medium pSmad3 were observed to be correlated with renal inflammation, such as cellular crescent (p = 0.011), intense interstitial inflammation (p = 0.029), and lower serum complement (C) 3 (p = 0.028) and C4 (p = 0.029). We also reported a significant association between pSmad3 expression in glomerular endothelial cells of proliferative GN (p = 0.045) and in podocytes of nonproliferative GN (p = 0.005). Finally, on multivariate Cox-regression analysis, TGF-β1 expression (hazard ratio = 6.078; 95% confidence interval: 1.168-31.627; p = 0.032) was emerged as independent predictor for CKD.

DISCUSSION/CONCLUSION

TGF-β1/Smad signaling is upregulated with specific characteristics in different forms of GN. TGF-β1 expression is indicated as independent risk factor for progression to CKD, while specific co-expression pattern of pSmad3 and Smad7 in glomerulus is correlated with renal inflammation.

Transforming growth factor beta signaling functions during mammalian kidney development

Aberrant transforming growth factor beta (TGFβ) signaling during embryogenesis is implicated in severe congenital abnormalities, including kidney malformations. However, the molecular mechanisms that underlie congenital kidney malformations related to TGFβ signaling remain poorly understood. Here, we review current understanding of the lineage-specific roles of TGFβ signaling during kidney development and how dysregulation of TGFβ signaling contributes to the pathogenesis of kidney malformation.

The effect of Echinococcus granulosus on spleen cells and TGF-β expression in the peripheral blood of BALB/c mice

Cystic echinococcosis (CE) caused by the cestode Echinococcus granulosus (E. granulosus) is a zoonotic parasitic disease. The effective immune evasion mechanisms of E. granulosus allow it to parasitize its hosts. However, the status of the innate and adaptive immune cells and their contributions to E. granulosus progression remain poorly understood. In this study, we aimed to determine the impact of E. granulosus infection on T cells, NK cell responses and TGF-β expression during the early infection phase in BALB/c mice. In E. granulosus infections, there was an increasing tendency in the percentage of CD4⁺ CD25⁺ T cells and CD4⁺ Foxp3⁺ T cells and peripheral blood TGF-β levels and relative expression of the Foxp3 gene. Moreover, there were a decreasing tendency in the percentage of NK cells and NK cell cytotoxicity and the expression of NKG2D on NK cells. The TGF-β1/Smad pathway was activated by E. granulosus in mice. Above results can be reversed by the inhibitor SB-525334 (potent activin receptor-like kinase 5 inhibitor). These results suggest that the TGF-β/Smad pathway plays an important role in changes of T-cell or NK cell responses. These results may contribute to revealing the preliminary molecular mechanisms in establishing hydatid infection.

Utility of Lymphoblastoid Cell Lines for Induced Pluripotent Stem Cell Generation

A large number of EBV immortalized LCLs have been generated and maintained in genetic/epidemiological studies as a perpetual source of DNA and as a surrogate in vitro cell model. Recent successes in reprograming LCLs into iPSCs have paved the way for generating more relevant in vitro disease models using this existing bioresource. However, the overall reprogramming efficiency and success rate remain poor and very little is known about the mechanistic changes that take place at the transcriptome and cellular functional level during LCL-to-iPSC reprogramming. Here, we report a new optimized LCL-to-iPSC reprogramming protocol using episomal plasmids encoding pluripotency transcription factors and mouse p53DD (p53 carboxy-terminal dominant-negative fragment) and commercially available reprogramming media. We achieved a consistently high reprogramming efficiency and 100% success rate using this optimized protocol. Further, we investigated the transcriptional changes in mRNA and miRNA levels, using FC-abs ≥ 2.0 and FDR ≤ 0.05 cutoffs; 5,228 mRNAs and 77 miRNAs were differentially expressed during LCL-to-iPSC reprogramming. The functional enrichment analysis of the upregulated genes and activation of human pluripotency pathways in the reprogrammed iPSCs showed that the generated iPSCs possess transcriptional and functional profiles very similar to those of human ESCs.

Susceptibility versus resistance in alveolar echinococcosis (larval infection with Echinococcus multilocularis)

Epidemiological studies have demonstrated that the majority of human individuals exposed to infection with Echinococcus spp. eggs exhibit resistance to disease as shown by either seroconversion to parasite--specific antigens, and/or the presence of 'dying out' or 'aborted' metacestodes, not including hereby those individuals who putatively got infected but did not seroconvert and who subsequently allowed no development of the pathogen. For those individuals where infection leads to disease, the developing parasite is partially controlled by host immunity. In infected humans, the type of immune response developed by the host accounts for the subsequent trichotomy concerning the parasite development: (i) seroconversion proving infection, but lack of any hepatic lesion indicating the failure of the parasite to establish and further develop within the liver; or resistance as shown by the presence of fully calcified lesions; (ii) controlled susceptibility as found in the "conventional" alveolar echinococcosis (AE) patients who experience clinical signs and symptoms approximately 5-15 years after infection, and (iii) uncontrolled hyperproliferation of the metacestode due to an impaired immune response (AIDS or other immunodeficiencies). Immunomodulation of host immunity toward anergy seems to be triggered by parasite metabolites. Beside immunomodulating IL-10, TGFβ-driven regulatory T cells have been shown to play a crucial role in the parasite-modulated progressive course of AE. A novel CD4+CD25+ Treg effector molecule FGL2 recently yielded new insight into the tolerance process in Echinococcus multilocularis infection.

Amlodipine prevents adriamycin-induced toxicity in cultured rat mesangial cells by up-regulation of Smad6, Smad7 expression

Extensive studies have demonstrated that transforming growth factor-beta (TGF-β) plays an important role in the progression of renal diseases. A central component of TGF-β is the TGF-β family-specific Smad signal transduction pathway. TGF-β signals through Smad2, 4 to mediate renal fibrosis, whereas induction of Smad6, 7 inhibits renal fibrosis and inflammation. Amlodipine is the most frequently used antihypertensive drug among dihydropyridines. It is beneficial to the kidney and is widely used in treating kidney diseases. The aim of this study was to investigate effects of amlodipine on adriamycin-induced changes of lactate dehydrogenase (LDH) and expression of Smad6, 7 in rat mesangial cells. Results showed that amlodipine (10(-8) to 10(-5)mol/l) significantly decreased LDH activity in rat mesangial cells when given in combination with TGF-β₁ (P<0.01); amlodipine (10(-7), 10(-6)mol/l) significantly increased Smad6, 7 mRNA and protein expression in cells treated with adriamycin and TGF-β₁ (P<0.01). In conclusion, amlodipine protects against adriamycin-induced toxicity in rat mesangial cells by up-regulation of Smad6, 7 expressions.

The role of transforming growth factor β1 in the regulation of blood pressure

Although human association studies suggest a link between polymorphisms in the gene encoding transforming growth factor (TGF) β1 and differing blood pressure levels, a causative mechanism for this correlation remains elusive. Recently we have generated a series of mice with graded expression of TGFβ1, ranging from approximately 10% to 300% compared to normal. We have found that blood pressure and plasma volume are negatively regulated by TGFβ1. Of note, the 10% hypomorph exhibits primary aldosteronism and markedly impaired urinary excretion of water and electrolytes. We here review previous literature highlighting the importance of TGFβ signaling as a natriuretic system, which we postulate is a causative mechanism explaining how polymorphisms in TGFβ1 could influence blood pressure levels.

Nuclear expression of Smad proteins and its prognostic significance in clear cell renal cell carcinoma

Smad2, Smad3, and Smad4 are components of the transforming growth factor β signaling pathway associated with tumorigenesis. The expression of these proteins is associated with tumor progression and prognosis of many cancers. This study aimed to evaluate the nuclear expression of Smad2, Smad3, and Smad4 in clear cell renal cell carcinoma and to assess the clinical significance and prognostic value of their expression patterns. The nuclear expression levels of Smads were evaluated in 637 cases of clear cell renal cell carcinomas using immunohistochemistry. To determine the statistical significance of Smad expression in clear cell renal cell carcinoma, each of the cases were divided into 2 groups (low and high expression groups) according to the extent of nuclear staining. Nuclear expressions of Smad3 and Smad4 were inversely correlated with the patient's age, the nuclear grade, the tumor size, and the pTNM stage. The Smad3-low and Smad4-low groups showed significantly shorter cancer-specific and progression-free survival times. Furthermore, multivariate analysis showed that both Smad3 and Smad4 were independent predictors for progression-free survival (P = .008 and P = .022, respectively). However, Smad2 expression was not related to clinicopathologic parameters and patients' survival. These results suggest that nuclear expressions of Smad3 and Smad4 were related to prognosis of clear cell renal cell carcinoma patients and may serve as novel prognostic markers in clear cell renal cell carcinoma patients.

TGF-β and TGF-β/Smad signaling in the interactions between Echinococcus multilocularis and its hosts

Alveolar echinococcosis (AE) is characterized by the development of irreversible fibrosis and of immune tolerance towards Echinococcus multilocularis (E. multilocularis). Very little is known on the presence of transforming growth factor-β (TGF-β) and other components of TGF-β/Smad pathway in the liver, and on their possible influence on fibrosis, over the various stages of infection. Using Western Blot, qRT-PCR and immunohistochemistry, we measured the levels of TGF-β1, TGF-β receptors, and down-stream Smads activation, as well as fibrosis marker expression in both a murine AE model from day 2 to 360 post-infection (p.i.) and in AE patients. TGF-β1, its receptors, and down-stream Smads were markedly expressed in the periparasitic infiltrate and also in the hepatocytes, close to and distant from AE lesions. Fibrosis was significant at 180 days p.i. in the periparasitic infiltrate and was also present in the liver parenchyma, even distant from the lesions. Over the time course after infection TGF-β1 expression was correlated with CD4/CD8 T-cell ratio long described as a hallmark of AE severity. The time course of the various actors of the TGF-β/Smad system in the in vivo mouse model as well as down-regulation of Smad7 in liver areas close to the lesions in human cases highly suggest that TGF-β plays an important role in AE both in immune tolerance against the parasite and in liver fibrosis.

[Effects of Shenqi Jiedu Decoction on expressions of transforming growth factor-beta1, smad2 and smad3 in renal tissues of rats with chronic renal failure induced by adenine]

OBJECTIVE

To investigate the effects of Shenqi Jiedu Decoction (SQJDD), a compound traditional Chinese herbal medicine, on expressions of transforming growth factor beta1 (TGF-beta1), smad2 and smad3 proteins in renal tissues of rats with chronic renal failure (CRF) induced by adenine, and to explore the mechanisms of SQJDD in treating CRF.

METHODS

Ninety healthy Wistar male rats were randomly divided into six groups: normal group, untreated group, losartan group, low-dose SQJDD group, medium-dose SQJDD group, and high-dose SQJDD group. Rat model of CRF was established by feeding 2.5% adenine. Levels of plasma creatinine (Cr) and blood urea nitrogen (BUN) in different groups after model establishment were detected to estimate the renal function of rats with CRF. After eight-week treatment, levels of Cr, BUN, triacylglycerol (TAG), cholesterol (Chol) and albumin (ALB) in plasma were detected. Pathological changes of renal tissue were observed by HE staining. Protein expressions of TGF-beta1, Smad2 and Smad3 in renal tissues were detected by Western blotting.

RESULTS

Compared with pretreatment, levels of Cr and BUN in the losartan group and the SQJDD groups were markedly decreased (P<0.01). After treatment, levels of Cr, BUN and Chol in all treated groups were lower than those in the untreated group (P<0.01, P<0.05). Levels of ALB in all treated groups were higher than that in the untreated group (P<0.01). Pathological lesions of renal tissues in all treated groups were lessened as compared with the untreated group (P<0.01). The Western blotting results showed that the protein expressions of TGF-beta1, Smad2 and Smad3 in renal tissues in all treated groups were lower than those in the untreated group (P<0.01).

CONCLUSION

SQJDD can delay the progress of CRF by inhibiting TGF-beta1/Smads signal transduction pathway.

Smad3-dependent signaling underlies the TGF-β1-mediated enhancement in astrocytic iNOS expression

We previously demonstrated that transforming growth factor-beta1 (TGF-beta1), while having no effect alone, enhances nitric oxide (NO) production in primary, purified mouse astrocytes induced by lipopolysaccharide (LPS) plus interferon-gamma (IFN-gamma), by recruiting a latent population of astrocytes to respond, thereby enhancing the total number of cells that express Nos2. In this investigation, we evaluated the molecular signaling pathway by which this occurs. We found that purified murine primary astrocytes express mRNA for TGFbetaRII as well as the TGFbetaRI subunit activin-like kinase 5 (ALK5), but not ALK1. Immunofluorescence microscopy confirmed the expression of TGFbetaRII and ALK5 protein in astrocytes. Consistent with ALK5 signaling, Smad3 accumulated in the nucleus of astrocytes as early as 30 min after TGF-beta1 (3 ng/mL) treatment and persisted upto 32 hr after TGF-beta1 administration. Addition of ALK5 inhibitors prevented TGF-beta1-mediated Smad3 nuclear accumulation and NO production when given prior to the Nos2 induction stimuli, but not after. Finally, astrocyte cultures derived from Smad3 null mutant mice did not exhibit a TGF-beta1-mediated increase in iNOS expression. Overall, this data suggests that ALK5 signaling and Smad3 nuclear accumulation is required for optimal enhancement of LPS plus IFNgamma-induced NO production in astrocytes by TGF-beta1.

Dynamic smad-mediated BMP signaling revealed through transgenic zebrafish

Bone morphogenic protein (BMP) signaling is fundamental to development, injury response, and homeostasis. We have developed transgenic zebrafish that report Smad-mediated BMP signaling in embryos and adults. These lines express either enhanced green fluorescent protein (eGFP), destabilized eGFP, or destabilized Kusabira Orange 2 (KO2) under the well-characterized BMP Response Element (BRE). These fluorescent proteins were found to be expressed dynamically in regions of known BMP signaling including the developing tail bud, hematopoietic lineage, dorsal eye, brain structures, heart, jaw, fins, and somites, as well as other tissues. Responsiveness to changes in BMP signaling was confirmed by observing fluorescence after activation in an hsp70:bmp2b transgenic background or by inhibition in an hsp70:nog3 background. We further demonstrated faithful reportage by the BRE transgenic lines following chemical repression of BMP signaling using an inhibitor of BMP receptor activity, dorsomorphin. Overall, these lines will serve as valuable tools to explore the mechanisms and regulation of BMP signal during embryogenesis, in tissue maintenance, and during disease.

Post-transcriptional up-regulation of Tsc-22 by Ybx1, a target of miR-216a, mediates TGF-{beta}-induced collagen expression in kidney cells

Increased accumulation of extracellular matrix proteins and hypertrophy induced by transforming growth factor-β1 (TGF-β) in renal mesangial cells (MC) are hallmark features of diabetic nephropathy. Although the post-transcriptional regulation of key genes has been implicated in these events, details are not fully understood. Here we show that TGF-β increased microRNA-216a (miR-216a) levels in mouse MC, with parallel down-regulation of Ybx1, a miR-216a target and RNA-binding protein. TGF-β also enhanced protein levels of Tsc-22 (TGF-β-stimulated clone 22) and collagen type I α-2 (Col1a2) expression in MC through far upstream enhancer E-boxes by interaction of Tsc-22 with an E-box regulator, Tfe3. Ybx1 colocalized with processing bodies in MC and formed a ribonucleoprotein complex with Tsc-22 mRNA, and this complex formation was reduced by TGF-β, miR-216a mimics, or Ybx1 shRNA to increase Tsc-22 protein levels but enhanced by miR-216a inhibitor oligonucleotides. Chromatin immunoprecipitation (ChIP) assays revealed that TGF-β could increase the occupancies of Tsc-22 and Tfe3 on enhancer E-boxes of Col1a2. Co-immunoprecipitation assays revealed that TGF-β promoted the interaction of Tsc-22 with Tfe3. These results demonstrate that post-transcriptional regulation of Tsc-22 mediated through Ybx1, a miR-216a target, plays a key role in TGF-β-induced Col1a2 in MC related to the pathogenesis of diabetic nephropathy.

Expression patterns of connective tissue growth factor and of TGF-beta isoforms during glomerular injury recapitulate glomerulogenesis

Transforming growth factor (TGF)-beta(1), -beta(2), and -beta(3) are involved in control of wound repair and development of fibrosis. Connective tissue growth factor (CTGF) expression is stimulated by all TGF-beta isoforms and is abundant in glomerulosclerosis and other fibrotic disorders. CTGF is hypothesized to mediate profibrotic effects of TGF-beta(1) or to facilitate interaction of TGF-beta(1) with its receptor, but its interactions with TGF-beta isoforms in nonpathological conditions are unexplored so far. Tissue repair and remodeling may recapitulate gene transcription at play in organogenesis. To further delineate the relationship between CTGF and TGF-beta, we compared expression patterns of CTGF and TGF-beta isoforms in rat and human glomerulogenesis and in various human glomerulopathies. CTGF mRNA was present in the immediate precursors of glomerular visceral and parietal epithelial cells in the comma- and S-shaped stages, but not in earlier stages of nephron development. During the capillary loop and maturing glomerular stages and simultaneous with the presence of TGF-beta(1), -beta(2), and -beta(3) protein, CTGF mRNA expression was maximal and present only in differentiating glomerular epithelial cells. CTGF protein was also present on precursors of mesangium and glomerular endothelium, suggesting possible paracrine interaction. Concomitant with the presence of TGF-beta(2) and -beta(3) protein, and in the absence of TGF-beta(1), CTGF mRNA and protein expression was restricted to podocytes in normal adult glomeruli. However, TGF-beta(1) and CTGF were again coexpressed, often with TGF-beta(2) and -beta(3), in particular in podocytes in proliferative glomerulonephritis and also in mesangial cells in diabetic nephropathy and IgA nephropathy (IgA NP). Coordinated expression of TGF-beta isoforms and of CTGF may be involved in normal glomerulogenesis and possibly in maintenance of glomerular structure and function at adult age. Prolonged overexpression of TGF-beta(1) and CTGF is associated with development of severe glomerulonephritis and glomerulosclerosis.

Transforming growth factor beta1 enhances tumor promotion in mouse skin carcinogenesis

Transforming growth factor beta1 (TGFbeta1) expression is elevated by tumor promoters in the mouse skin, but its role in tumor promotion has not been well defined. To investigate this, we have compared TGFbeta1+/+ and +/- mice in a two-stage skin chemical carcinogenesis protocol. Surprisingly, TGFbeta1+/- mice had fewer number and incidence of benign papillomas, reduced epidermal and tumor cell proliferation and reduced epidermal TGFbeta1 and nuclear p-Smad2 localization in response to the tumor promoter 12-O-tetradecanoylphorbol 13-acetate (TPA) compared with TGFbeta1+/+ mice. Maximal TPA activation of protein kinase C (PKCalpha) as measured by activity assays and activation of target genes and induction of cornified envelopes correlated with TGFbeta1 gene dosage in keratinocytes and addition of exogenous TGFbeta1 restored the cornification defect in TGFbeta1+/- keratinocytes. Similarly, inhibition of ALK5-suppressed TPA-mediated PKCalpha activation suggesting that physiological levels of TGFbeta1 are required for maximal activation of PKC-dependent mitogenic responses. Paradoxically, the TPA-induced inflammatory response was greater in TGFbeta1+/- skin, but TGFbeta1+/+ papillomas had more tumor infiltrating myeloperoxidase-positive cells and pro-inflammatory gene expression was elevated in v-ras(Ha)-transduced TGFbeta1+/+ but not TGFbeta1+/- keratinocytes. Thus, ras activation switches TGFbeta1 to a pro-inflammatory cytokine. Despite this differential proliferative and inflammatory response to TPA and enhanced papilloma formation in the TGFbeta1+/+ mice, the frequency of malignant conversion was reduced compared with TGFbeta1+/- mice. Therefore, TGFbeta1 promotes benign tumors by modifying tumor promoter-induced cell proliferation and inflammation but retains a suppressive function for malignant conversion.

Expression and significance of TGF-beta1/Smad signaling pathway in children with IgA nephropathy

BACKGROUND

IgA nephropathy (IgAN) exhibits an indolent but slowly progressive course, and about 30% of children with IgAN are found to deteriorate to end-stage renal failure characterized by overaccumulation of extracellular matrix, diffuse glomerular sclerosis, and tubulointerstitial fibrosis. The TGF-beta/Smad signaling pathway plays an important role in glomerulosclerosis and tubulointerstitial fibrosis. The present study aimed to elucidate the significance of expressions of TGF-beta1, phosphorylated Smad3 (p-Smad3), Smad7 and fibronectin (FN) in the renal tissue of children with IgAN.

METHODS

Forty-six children with IgAN were divided into 3 groups according to their clinical features: isolated hematuria group (IH group, 8 patients), hematuria and proteinuria group (HP group, 24), and nephritic syndrome group (NS group, 14). Patients were also divided into three groups according to their pathologic grade: grade I+II (22 patients), grade III (12) and grade IV (12) groups. Five normal renal specimens were used as the control group. The expression of TGF-beta1, p-Smad3, Smad7 and FN in renal biopsy specimens was detected by two-step PowerVision. The degrees of renal tubular injury and interstitial fibrosis were scored according to the Katafuchi semi-quantitative criteria.

RESULTS

The expression of TGF-beta1, p-Smad3, Smad7 and FN in children with IgAN was significantly higher than that in the control group (in glomeruli: P<0.05, P<0.01, P<0.05 and P<0.01, respectively; in tubulointerstitium: P<0.05, P<0.05, P<0.01 and P<0.05, respectively) and the highest expression levels were found in the NS and grade IV groups (P<0.05, P<0.01). The expression levels of the four proteins were not only positvely correlated with each other, but also with the grade of renal tubular injury and renal interstitial fibrosis (P<0.05).

CONCLUSION

The TGF-beta1/Smad signaling pathway plays an important role in the progress of glomerular sclerosis, renal tubular injury and interstitial fibrosis in children with IgAN.

An in vivo reporter of BMP signaling in organogenesis reveals targets in the developing kidney

Background

Bone morphogenetic proteins (BMPs) regulate essential processes during organogenesis, and a functional understanding of these secreted proteins depends on identification of their target cells. In this study, we generate a transgenic reporter for organogenesis studies that we use to define BMP pathway activation in the developing kidney.

Results

Mouse strains reporting on BMP pathway activation were generated by transgenically expressing β-galactosidase under the control of BMP responsive elements from Id1. Reporter expression corresponds well with immunoassays for pathway activation in all organs studied, validating the model. Using these reporters we have generated a detailed map of cellular targets of BMP signaling in the developing kidney. We find that SMAD dependent BMP signaling is active in collecting duct trunks, but not tips. Furthermore, glomerular endothelial cells, and proximal nephron tubules from the renal vesicle stage onward show pathway activation. Surprisingly, little activation is detected in the nephrogenic zone of the kidney, and in organ culture BMP treatment fails to activate SMAD dependent BMP signaling in nephron progenitor cells. In contrast, signaling is efficiently induced in collecting duct tips.

Conclusion

Transgenic reporters driven by control elements from BMP responsive genes such as Id1 offer significant advantages in sensitivity and consistency over immunostaining for studies of BMP pathway activation. They also provide opportunities for analysis of BMP signaling in organ and primary cell cultures subjected to experimental manipulation. Using such a reporter, we made the surprising finding that SMAD dependent BMP signaling is inactive in nephron progenitors, and that these cells are refractory to activation by applied growth factors. Furthermore, we find that the BMP pathway is not normally active in collecting duct tips, but that it can be ectopically activated by BMP treatment, offering a possible explanation for the inhibitory effects of BMP treatment on collecting duct growth and branching.

TLR4 links podocytes with the innate immune system to mediate glomerular injury

Toll-like receptors (TLR) classically recognize pathogen-associated danger signals but are also activated via endogenous ligands. For evaluation of their role in inflammatory kidney disease, the function of TLR was analyzed in two mouse models of cryoglobulinemic membranoproliferative glomerulonephritis (MPGN; mice transgenic for thymic stromal lymphopoietin [TSLP], with or without deletion of the Fcgamma receptor IIb). Expression of TLR1 through 9 and TLR11 mRNA was detectable in whole kidneys and in isolated glomeruli of wild-type mice, with TLR3 and TLR4 having the highest absolute levels of expression. TLR1, 2, and 4 were increased in TSLP transgenic mice and even higher in TSLP transgenic FcgammaRIIb-deficient mice. TLR5 through 9 and 11 were upregulated to similar degrees in TSLP transgenic and TSLP transgenic FcgammaRIIb-deficient mice. Immunohistochemical studies of nephritic glomeruli localized TLR4 protein to podocytes. Cultured podocytes also expressed TLR4, and stimulation with TLR4-specific ligands resulted in a marked induction of chemokines; this was reduced by specific knockdown of TLR4 with siRNA. Fibrinogen, a potential endogenous TLR4 ligand, was shown to induce a similar profile of chemokines. In conclusion, it was demonstrated that TLR4 is constitutively expressed by podocytes and is upregulated in MPGN, where it may mediate glomerular injury by modulating expression of chemokines; therefore, TLR4 may link podocytes with the innate immune system to mediate MPGN triggered by the deposition of immune complexes.