Transforming growth factor-β1/Smad3-independent epithelial-mesenchymal transition in type I collagen glomerulopathy

Identification and Expression Characterization of the Smad3 Gene and SNPs Associated with Growth Traits in the Hard Clam (Meretrix meretrix)

It has been demonstrated that the sekelsky mothers against decapentaplegic homolog 3 (Smad3) plays an important role in the growth and development of vertebrates. However, little is known about the association between the Smad3 gene and the growth traits of mollusks. In this study, Smad3 from the hard clam Meretrix meretrix (Mm-Smad3) was cloned, characterized, and screened for growth-related single nucleotide polymorphisms (SNPs) in its exons. The full-length cDNA of Mm-Smad3 was 1938 bp, encoding a protein with 428 amino acid residues. The protein sequence included an MH1 (27–135 aa) and MH2 domain (233–404 aa). Promoter analysis showed that the promoter sequence of Mm-Smad3 was 2548 bp, and the binding sites of Pit-1a, Antp, Hb, and other transcription factors are related to the growth and development of hard clams. The phylogenetic tree was divided into two major clusters, including mollusks and vertebrate. The expression level of Mm-Smad3 was predominantly detected in the mantle and foot, while extremely less expression was observed in the digestive gland. The low expression level of Mm-Smad3 was detected at the stages of unfertilized mature eggs, fertilized eggs, four-cell embryos, blastula, gastrulae, trochophore, and D-shaped larvae, whereas an opposite trend was observed regarding the highest expression at the umbo larvae stage (p < 0.05). In the mantle repair experiment, the time-course expression profiles showed that compared to the expression level at 0 h, Mm-Smad3 significantly decreased at 6 h (p < 0.05) but increased at 12 and 48 h. Further, the association analysis identified 11 SNPs in the exons of Mm-Smad3, of which three loci (c.597 C > T, c.660 C > T, c.792 A > T) were significantly related to the growth traits of clam (p < 0.05). Overall, our findings indicated that Mm-Smad3 is a growth-related gene and the detected SNP sites provide growth-related markers for molecular marker-assisted breeding of this species.

The Influence of a Nanopatterned Scaffold that Mimics Abnormal Renal Mesangial Matrix on Mesangial Cell Behavior

The alteration of mesangial matrix (MM) components in mesangium, such as type IV collagen (COL4) and type I collagen (COL1), is commonly found in progressive glomerular disease. Mesangial cells (MCs) responding to altered MM, show critical changes in cell function. This suggests that the diseased MM structure could play an important role in MC behavior. To investigate how MC behavior is influenced by the diseased MM 3D nanostructure, we fabricated the titanium dioxide (TiO2)-based nanopatterns that mimic diseased MM nanostructures. Immortalized mouse MCs were used to assess the influence of disease-mimic nanopatterns on cell functions, and were compared with a normal-mimic nanopattern. The results showed that the disease-mimic nanopattern induced disease-like behavior, including increased proliferation, excessive production of abnormal MM components (COL1 and fibronectin) and decreased normal MM components (COL4 and laminin α1). In contrast, the normal-mimic nanopattern actually resulted in cells displaying normal proliferation and the production of normal MM components. In addition, increased expressions of α-smooth muscle actin (α-SMA), transforming growth factor β1 (TGF-β1) and integrin α5β1 were detected in cells grown on the disease-mimic nanopattern. These results indicated that the disease-mimic nanopattern induced disease-like cell behavior. These findings will help further establish a disease model that mimics abnormal MM nanostructures and also to elucidate the molecular mechanisms underlying glomerular disease.

UA promotes epithelial‑mesenchymal transition in peritoneal mesothelial cells

Long‑term peritoneal dialysis is often limited or interrupted due to the development and progression of peritoneal fibrosis. Accumulating evidence suggests that epithelial‑mesenchymal transition (EMT) is a major component of peritoneal injury associated with peritoneal fibrosis in the end stage of renal disease; however, at present, the underlying mechanisms remain unclear. Thus, in the present study, uric acid (UA)‑induced EMT of peritoneal mesothelial cells was investigated by western‑blot and immunofluorescence staining. The results revealed that peritoneal mesothelial cells stimulated with UA underwent EMT, as demonstrated by the decreased expression of epithelial markers (E‑cadherin) and an increased expression of mesenchymal markers (α‑smooth muscle actin and vimentin). Additionally, it was reported that UA could facilitate the progression of EMT of peritoneal mesothelial cells via EMT transcription pathways, including transforming growth factor‑β1/mothers against decapentaplegic homolog 3 and P38/mitogen‑activated protein kinase by western‑blot and reverse transcription semi‑quantitative polymerase chain reaction. The results of the present study suggest that UA could promote EMT and may contribute to peritoneal chronic disease. Furthermore, the data obtained suggest that the levels of blood UA may account for the development of EMT; thus, lowering the levels of blood UA may be beneficial to inhibit the occurrence and development of peritoneal fibrosis.

Roles of the procollagen C-propeptides in health and disease

The procollagen C-propeptides of the fibrillar collagens play key roles in the intracellular assembly of procollagen molecules from their constituent polypeptides chains, and in the extracellular assembly of collagen molecules into fibrils. Here we review recent advances in understanding the molecular mechanisms controlling C-propeptide trimerization which have revealed the importance of inter-chain disulphide bonding and a small number of charged amino acids in the stability and specificity of different types of chain association. We also show how the crystal structure of the complex between the C-propeptide trimer of procollagen III and the active fragment of procollagen C-proteinase enhancer-1 leads to a detailed model for accelerating release of the C-propeptides from procollagen by bone morphogenetic protein-1 and related proteinases. We then discuss the effects of disease-related missense mutations in the C-propeptides in relation to the sites of these mutations in the three-dimensional structure. While in general there is a good correlation between disease severity and structure-based predictions, there are notable exceptions, suggesting new interactions involving the C-propeptides yet to be characterized. Mutations affecting proteolytic release of the C-propeptides from procollagen are discussed in detail. Finally, the roles of recently discovered interaction partners for the C-propeptides are considered during fibril assembly and cross-linking.

GREB1 is an estrogen receptor-regulated tumour promoter that is frequently expressed in ovarian cancer

Estrogenic hormone replacement therapy increases the risk of developing ovarian cancer, and estrogen promotes tumour initiation and growth in mouse models of this disease. GREB1 (Growth regulation by estrogen in breast cancer 1) is an ESR1 (estrogen receptor 1)-upregulated protein which may mediate estrogen action. GREB1 knockdown prevents hormone-driven proliferation of several breast and prostate cancer cell lines and prolongs survival of mice engrafted with ovarian cancer cells, but its mechanism of action remains unclear. In this study, we explored GREB1 function in ovarian cancer. GREB1 overexpression in ovarian cancer cell lines increased cell proliferation and migration and promoted a mesenchymal morphology associated with increased Col1a2, which encodes a collagen I subunit. GREB1 knockdown inhibited proliferation and promoted an epithelial morphology associated with decreased Col1a2. In human tissues, GREB1 was expressed in all ESR1-expressing tissues throughout the normal female reproductive tract, in addition to several tissues that did not show ESR1 expression. In a TMA of ovarian cancer cases, GREB1 was expressed in 75–85% of serous, endometrioid, mucinous, and clear cell carcinomas. Serous, endometrioid, and mucinous ovarian cancers were almost always positive for either ESR1 or GREB1, suggesting a possible reliance on signalling through ESR1 and/or GREB1. Targeting GREB1 may inhibit tumour-promoting pathways both downstream and independent of ESR1 and is therefore a possible treatment strategy worthy of further investigation.

Role of Smad3 signaling in the epithelial‑mesenchymal transition of the lens epithelium following injury

Transforming growth factor-β (TGF-β) is important in the development of posterior capsule opacification (PCO), and inhibition of the TGF-β pathway may represent a novel method of treating PCO. Drosophila protein, mothers against decapentaplegic homolog 3 (Smad3) is a phosphorylated receptor-activated Smad required for the transmission of TGF-β signals. Smad3 knockout (KO) disturbs the activation of TGF-β signaling, thus inhibiting the onset of PCO. In the present study, lens epithelial cell (LEC) damage induced by extracapsular cataract extraction was simulated by puncture of the anterior capsule using a 26-gauge hypodermic needle. The effect of Smad3 in the trauma-induced epithelial-mesenchymal transition (EMT) of the lens epithelium in Smad3-KO and wild-type (WT) mice was then observed. The expression levels of EMT markers and extracellular matrix components were measured in the two groups by reverse transcription-quantitative polymerase chain reaction analysis, western blot analysis and immunofluorescence staining. Apoptosis was also detected in the punctured anterior capsule. The Smad3-KO mice exhibited lower expression levels of α-smooth muscle actin, lumican, osteopontin, fibronectin and collagen, compared with the WT mice. Additionally, the Smad3-KO mice exhibited a higher percentage of apoptotic cells than the WT mice. Smad3 signaling was associated with the induction of trauma-induced EMT, and Smad3 KO interfered with TGF-β signaling pathway activation, but did not completely inhibit the trauma-induced EMT in LECs. Therefore, Smad3 may be a target in the treatment of PCO and other fibrosis-related diseases.