Fetuin: its enigmatic property of growth promotion

Lectin-conjugated nanotags with high SERS stability: selective probes for glycans

Surface-enhanced Raman scattering (SERS) nanotags functionalized with lectins as the biological recognition element can be used to target the carbohydrate portion of carbohydrate-carrying molecules (glycoconjugates). An investigation of the optical stability of such functionalized SERS nanotags is an essential initial step before future application and quantification of surface glycan biomarkers on cells and extracellular vesicles. Herein, we report an innovative approach to evaluate the SERS stability of lectin-conjugated nanotags by investigating any possible interfering lectin-lectin interactions in a mixture of different lectin-conjugated SERS nanotags, as well as an assessment of lectin-glycan interaction by mixing wheat germ agglutinin (WGA)-conjugated SERS nanotags with different glycoproteins. No lectin cross-reactivity was found in the mixture of lectin-conjugated SERS nanotags, evidenced by the constant SERS intensity. Additionally, the results showed that the lectins conjugated to SERS nanotags retain their ability to interact with glycans, as evidenced by the changes in the nanotag color and extinction spectra. Their SERS intensity remained constant as supported by finite-element method (FEM) simulation results, demonstrating a high SERS stability and selectivity of lectin-conjugated nanotags towards multiplex applications.

Enhancement of protein immobilization on polydimethylsiloxane using a synergistic combination of polydopamine and micropattern surface modification

Understanding protein interactions at biointerfaces is critical for the improved design of biomaterials and medical devices. Polydimethylsiloxane (PDMS) is used for numerous device applications, and surface modifications can enhance protein immobilization and the response to cells. A multifunctional approach combining topographical and biochemical modifications was applied to PDMS by fabricating 10-20 µm scale patterns onto PDMS surfaces and by coating with polydopamine (PDA). The modifications were confirmed by surface characterization and bovine serum albumin (BSA), fibrinogen (Fg), and fetuin-A (Fet-A) were radiolabeled with 125I. The amounts of protein attached to the surface before and after elution with sodium dodecyl sulfate (SDS) were quantified from single and complex multi-protein solutions to determine protein stability and competitive binding. The PDA coatings were the most stable and capable of immobilizing the highest levels of all proteins. Furthermore, combinations of PDA coatings with the smallest micropatterns provided an additional improvement, enhancing the amount immobilized and the stability. The adsorption of BSA and Fg from plasma demonstrated competitive binding and possible orientation changes, respectively. It was determined that Fet-A, a less studied protein, adsorbed from plasma at low levels, but the adsorption from fetal bovine serum (FBS) was significantly greater, providing important quantification data from radiolabeling that is relevant to many cell culture studies. Overall, combining topography and PDA modification has a synergistic effect on improving protein immobilization. These findings provide new insight on the quantities of proteins bound to PDMS and PDA coatings with implications for cell interactions in various biotechnology and medical applications.

The structure, biosynthesis, and biological roles of fetuin-A: A review

Fetuin-A is a heterodimeric plasma glycoprotein containing an A-chain of 282 amino acids and a B-chain of 27 amino acid residues linked by a single inter-disulfide bond. It is predominantly expressed in embryonic cells and adult hepatocytes, and to a lesser extent in adipocytes and monocytes. Fetuin-A binds with a plethora of receptors and exhibits multifaceted physiological and pathological functions. It is involved in the regulation of calcium metabolism, osteogenesis, and the insulin signaling pathway. It also acts as an ectopic calcification inhibitor, protease inhibitor, inflammatory mediator, anti-inflammatory partner, atherogenic factor, and adipogenic factor, among other several moonlighting functions. Fetuin-A has also been demonstrated to play a crucial role in the pathogenesis of several disorders. This review mainly focuses on the structure, synthesis, and biological roles of fetuin-A. Information was gathered manually from various journals via electronic searches using PubMed, Google Scholar, HINARI, and Cochrane Library from inception to 2022. Studies written in English and cohort, case-control, cross-sectional, or experimental studies were considered in the review, otherwise excluded.

Serum Protein Adsorption Modulates the Toxicity of Highly Positively Charged Hydrogel Surfaces

Hydrogels formed from peptide self-assembly are a class of materials that are being explored for their utility in tissue engineering, drug and cell delivery, two- and three-dimensional cell culture, and as adjuvants in surgical procedures. Most self-assembled peptide gels can be syringe-injected in vivo to facilitate the local delivery of payloads, including cells, directly to the targeted tissue. Herein, we report that highly positively charged peptide gels are inherently toxic to cells, which would seem to limit their utility. However, adding media containing fetal bovine serum, a common culture supplement, directly transforms these toxic gels into cytocompatible materials capable of sustaining cell viability even in the absence of added nutrients. Multistage mass spectrometry showed that at least 40 serum proteins can absorb to a gel's surface through electrostatic attraction ameliorating its toxicity. Further, cell-based studies employing model gels having only bovine serum albumin, fetuin-A, or vitronectin absorbed to the gel surface showed that single protein additives can also be effective depending on the identity of the cell line. Separate studies employing these model gels showed that the mechanism(s) responsible for mitigating apoptosis involve both the pacification of gel surface charge and adsorbed protein-mediated cell signaling events that activate both the PI3/Akt and MAPK/ERK pathways which are known to facilitate resistance to stress-induced apoptosis and overall cell survival.

Effects of upper airway obstruction or hypoxia on gastroesophageal reflux in newborn lambs

BACKGROUND

Although it is commonly accepted that upper airway obstruction (UAO) increases gastroesophageal reflux (GER), the link is poorly understood and insufficiently documented. In addition, while hypoxia is often encountered in infants with UAO, its consequences on GER are virtually unknown. The two aims of the present study were to characterize the effects of (1) UAO and (2) hypoxia on GER.

METHODS

Seventeen lambs underwent polysomnographic and esophageal impedance/pH-metry monitoring during UAO vs. a control condition (6 h, ten lambs) or 10% hypoxia vs. normoxic condition (3 h, seven other lambs).

RESULTS

Moderate-to-severe UAO was maintained throughout monitoring (inspiratory tracheal pressure of -13 (-15, -12) cm H₂O vs. -1 (-1, -1) cm H₂O in control condition, p = 0.005). While the number of GERs increased with UAO (2 (1, 4) vs. 0 (0, 3) in the control condition, p = 0.03), the increase was less than anticipated and inconsistent among the lambs. Also, sustained 10% hypoxia did not alter the number of GERs (2 (1, 3) vs. 0 (0, 5) in the control condition, p = 0.9).

CONCLUSIONS

The presence of an UAO for 6 h mildly increased the number of GERs, whereas hypoxia for 3 h had no significant effect.

IMPACT

The effect of upper airway obstruction and hypoxia on gastroesophageal reflux is poorly documented in the neonatal period. A moderate-to-severe upper airway obstruction for 6 h results in a mild, inconsistent increase in the number of gastroesophageal refluxes. Overall, a hypoxia of 10% for 3 h had no significant impact on gastroesophageal reflux. The prescription of an antireflux medication in infants with upper airway obstruction must not be systematic but rely on objective signs of a pathologic gastroesophageal reflux.

Effects of fetuin-A with diverse functions and multiple mechanisms on human health

Fetuin-A (Alfa 2-Heremans-Schmid) is a glycoprotein that is mainly synthesized by hepatocytes and then released into the bloodstream. While fetuin-A, a multifunctional protein, has inhibitory effects on health in the processes of calcification, mineralization, coronary artery calcification (CAC), and kidney stone formation by various mechanisms, it has such stimulatory effects as obesity, diabetes, and tumor progression processes. Fetuin-A produces these effects on the organism mainly by playing a role in the secretion levels of some inflammatory cytokines and exosomes, preventing unwanted calcification, inhibiting the autophosphorylation of tyrosine kinase, suppressing the release of adiponectin and peroxisome proliferator-activated receptor-γ (PPARγ), activating the toll-like receptor 4 (TLR-4), triggering the phosphatidylinositol 3 (PI3) kinase/Akt signaling pathway and cell proliferation, and mimicking the transforming growth factor-beta (TGF-β) receptor. In the present review, fetuin-A was examined in a wide perspective from the structure and release of fetuin-A to its effects on health.

A novel serum-free medium for the isolation, expansion and maintenance of stemness and tissue-specific markers of primary human periodontal ligament cells

PURPOSE

Periodontal ligament (PDL) cell cultures are classically maintained in serum-containing media. However, unwanted side-effects of these conditions on cellular and molecular characteristics demand a serum-free alternative. Even though these limitations are well known and efforts for the development of adequate serum-free alternatives have been made, these approaches for replacement remained unsuccessful so far. This study aimed at developing a well-defined, serum-free formulation supporting both isolation from tissue samples and efficient expansion of PDL cells. Here, of particular focus was the perpetuation of tissue-characteristic markers detectable in primary tissues and of stemness features.

BASIC PROCEDURES

Primary PDL cell cultures from generally healthy human donors (n = 3) were maintained in basal media N2B27 and E6 together with different concentrations of growth and attachment factors. Cell proliferation was recorded via microscopy and WST assay. Gene expression of RUNX2, Periostin, ALP, CD73, CD90, CD105, CD45, SOX10 and SOX2 was compared to primary PDL explants via qRT-PCR. Immunocytochemistry was performed for anti-CD105, SSEA-3, CD271, HNK1. Serum-containing sDMEM medium served as control.

MAIN FINDINGS

N2B27 medium substituted with 25 ng/mL EGF, 25 ng/mL IGF1, 0.5 mg/mL Fetuin plus gelatine coating (designated N2B27-PDLsf) emerged as potent serum-free formulation ensuring adequate culture isolation and expansion. Here, PDL primary tissue signature markers RUNX2 and Periostin remained stable in N2B27-PDLsf compared to controls (229.0-fold ±101.0 and 83.2-fold ±9.6 increase). Additionally, stemness markers ALP and CD105 were significantly upregulated on transcriptional, and CD105 and SOX2 on protein level.

PRINCIPAL CONCLUSIONS

This investigation identified a novel serum-free medium for the isolation, and expansion of primary human PDL cells with constantly high proliferation rates. Here, purity and stemness properties are maintained. Thus, N2B27-PDLsf represents a valid replacement for serum-containing media in PDL cultures.

Pathophysiological Implication of Fetuin-A Glycoprotein in the Development of Metabolic Disorders: A Concise Review

Alpha 2-Heremans-Schmid glycoprotein, also known as fetuin-A (Fet-A), is a multifunctional plasma glycoprotein that has been identified in both animal and human beings. The protein is a hepatokine predominantly synthesized in the liver, which is considered as an important component of diverse normal and pathological processes, including bone metabolism regulation, vascular calcification, insulin resistance, and protease activity control. Epidemiological studies have already consistently demonstrated significant elevated circulating Fet-A in the course of obesity and related complications, such as type 2 diabetes mellitus, metabolic syndrome, and nonalcoholic fatty liver disorder (NAFLD). Moreover, Fet-A has been strongly correlated with many parameters related to metabolic homeostasis dysregulation, such as insulin sensitivity, glucose tolerance, circulating lipid levels (non-esterified free fatty acids and triglycerides), and circulating levels of both pro- and anti-inflammatory factors (C-reactive protein, tumor necrosis factor-α (TNF-α), and interleukin (IL)-6). Metabolic-interfering effects of Fet-A have thus been shown to highly exacerbate insulin resistance (IR) through blocking insulin-stimulated glucose transporter 4 (GLUT-4) translocation and protein kinase B (Akt) activation. Furthermore, the protein appeared to interfere with downstream phosphorylation events in insulin receptor and insulin receptor substrate signaling. The emerging importance of Fet-A for both diagnosis and therapeutics has therefore come to the attention of researchers and the pharmaceutical industry, in the prospect of developing new therapeutic strategies and diagnosis methods for metabolic disorders.

Are Fetuin-A levels beneficial for estimating timing of sepsis occurrence?

Objectives:

To evaluated Fetuin-A levels of patients admitted in the intensive care unit with a diagnosis of sepsis.

Methods:

This study was conducted at the Faculty of Medicine, Çanakkale Onsekiz Mart University Hospital, Çanakkal, Turkey, between February 2015 and October 2015. Forty septic patients were included in the study. Subsequent to clinical suspicion of sepsis, serum levels of C-reactive protein (CRP) and procalcitonin; and white blood cell (WBC) counts were evaluated at 3 time-points: 0 (basal), 24, and 72 hours.

Results:

The mean Fetuin-A levels at the 3 time-points were 58.5 ± 29.2 ng/mL, 40.9 ± 23.6 ng/mL, and 47.8 ± 25.7 ng/mL, respectively. Fetuin-A levels at 24 hours were significantly lower than the basal level (p<0.05), where as no significant difference was observed between the basal levels and those at 72 hours (p>0.05). Correlation between the temporal changes in Fetuin-A levels and the changes in other inflammatory markers (CRP, procalcitonin and WBC) was examined. Fetuin A was found to have only a negative correlation with serum procalcitonin level (p<0.05).

Conclusion:

In this study, serum Fetuin-A levels in septic patients decreased significantly in the first 24 hours, followed by an insignificant increase at 72 hours. These findings suggest that monitoring of Fetuin-A levels may help predict the time of occurrence of sepsis and prognosis of sepsis.

Cellular Clearance and Biological Activity of Calciprotein Particles Depend on Their Maturation State and Crystallinity

Background: The liver-derived plasma protein fetuin-A is a systemic inhibitor of ectopic calcification. Fetuin-A stabilizes saturated mineral solutions by forming colloidal protein-mineral complexes called calciprotein particles (CPP). CPP are initially spherical, amorphous and soft, and are referred to as primary CPP. These particles spontaneously convert into secondary CPP, which are larger, oblongate, more crystalline, and less soluble. CPP mediate excess mineral transport and clearance from circulation. Methods: We studied by intravital two-photon microscopy the clearance of primary vs. secondary CPP by injecting i.v. synthetic fluorescent CPP in mice. We analyzed CPP organ distribution and identified CPP endocytosing cells by immunofluorescence. Cellular clearance was studied using bone marrow-derived mouse wildtype and scavenger receptor A (SRA)-deficient macrophages, as well as human umbilical cord endothelial cells (HUVEC), monocyte-derived macrophages (hMDM), and human aortic endothelial cells (haEC). We employed mouse wildtype and mutant immortalized macrophages to analyze CPP-induced inflammasome activation and cytokine secretion. Results: In live mice, only primary CPP were rapidly cleared by liver sinusoidal endothelial cells (LSEC), whereas primary and secondary CPP were cleared by Kupffer cells. Scavenger receptor A (SRA)-deficient bone marrow macrophages endocytosed secondary CPP less well than did wildtype macrophages. In contrast, primary CPP endocytosis did not depend on the presence of SRA, suggesting involvement of an alternative clearance pathway. CPP triggered TLR4 dependent TNFα and IL-1β secretion in cultured macrophages. Calcium content-matched primary CPP caused twice more IL-1β secretion than did secondary CPP, which was associated with increased calcium-dependent inflammasome activation, suggesting that intracellular CPP dissolution and calcium overload may cause this inflammation. Conclusions: Secondary CPP are endocytosed by macrophages in liver and spleen via SRA. In contrast, our results suggest that primary CPP are cleared by LSEC via an alternative pathway. CPP induced TLR4-dependent TNFα and inflammasome-dependent IL-1β secretion in macrophages suggesting that inflammation and calcification may be considered consequences of prolonged CPP presence and clearance.

Impact of Fetuin-A (AHSG) on Tumor Progression and Type 2 Diabetes

Fetuin-A is the protein product of the AHSG gene in humans. It is mainly synthesized by the liver in adult humans and is secreted into the blood where its concentration can vary from a low of ~0.2 mg/mL to a high of ~0.8 mg/mL. Presently, it is considered to be a multifunctional protein that plays important roles in diabetes, kidney disease, and cancer, as well as in inhibition of ectopic calcification. In this review we have focused on work that has been done regarding its potential role(s) in tumor progression and sequelae of diabetes. Recently a number of laboratories have demonstrated that a subset of tumor cells such as pancreatic, prostate and glioblastoma multiform synthesize ectopic fetuin-A, which drives their progression. Fetuin-A that is synthesized, modified, and secreted by tumor cells may be more relevant in understanding the pathophysiological role of this enigmatic protein in tumors, as opposed to the relatively high serum concentrations of the liver derived protein. Lastly, auto-antibodies to fetuin-A frequently appear in the sera of tumor patients that could be useful as biomarkers for early diagnosis. In diabetes, solid experimental evidence shows that fetuin-A binds the β-subunit of the insulin receptor to attenuate insulin signaling, thereby contributing to insulin resistance in type 2 diabetes mellitus (T2DM). Fetuin-A also may, together with free fatty acids, induce apoptotic signals in the beta islets cells of the pancreas, reducing the secretion of insulin and further exacerbating T2DM.

The Growth of Preantral Follicles and the Impact of Different Supplementations and Circumstances: A Review Study with Focus on Bovine and Human Preantral Follicles

One of the most important concerns cancer survivors face is fertility. Current treatment modalities often result in damage to the reproductive system. Different options have been proposed to preserve the fertility of affected women, and many attempts have been made to improve their chance of childbearing after therapy. Cryopreservation of ovarian tissue and follicles before the onset of cancer treatment and then either transplantation of ovarian tissue or culture of ovarian tissue and individual follicles in vitro is a commonly cited approach. Extensive research is being done to design an optimal condition for the culture of ovarian follicles. Improving follicle culture systems by understanding their actual growth needs might be a crucial step toward fertility preservation in cancer patients. This review article will try to provide a summary of the role of different factors and conditions on growth of human and bovine preantral follicles in vitro.

Exosome: emerging biomarker in breast cancer

Exosomes are nano-sized membrane vesicles released by a variety of cell types, and are thought to play important roles in intercellular communications. In breast cancer, through horizontal transfer of various bioactive molecules, such as proteins and mRNAs, exosomes are emerging as local and systemic cell-to-cell mediators of oncogenic information and play an important role on cancer progression. This review outlines the current knowledge and concepts concerning the exosomes involvement in breast cancer pathogenesis (including tumor initiation, invasion and metastasis, angiogenesis, immune system modulation and tumor microenvironment) and cancer therapy resistance. Moreover, the potential use of exosomes as promising diagnostic and therapeutic biomarkers in breast cancer are also discussed.

Gene delivery system of pDNA using the blood glycoprotein fetuin

Fetuin is a biocompatible plasma protein and strongly enhances phagocytosis of bacteria, DNA and apoptotic cells by peripheral blood cells such as monocytes, macrophages and dendritic cells. We developed a novel gene delivery system: ternary complexes constructed with pDNA, polyethylenimine (PEI) and fetuin. Without covalent binding, fetuin was able to coat pDNA-PEI complexes, and stable anionic nanoparticles formed at a weight ratio greater than 30. Optimised pDNA-PEI-fetuin complexes significantly decreased the cytotoxicity of pDNA-PEI complexes in the melanoma cell line B16F10. Furthermore, the pDNA-PEI-fetuin complexes had higher transgene efficiency compared to that of commercial lipofectin previously reported in B16F10 cells despite an anionic surface. The pDNA-PEI-fetuin complexes did not agglutinate with erythrocytes. The pDNA-PEI-fetuin complexes had high gene expression in the spleen after intravenous administration in mice. Thus, the pDNA-PEI-fetuin complexes were a useful in vivo gene delivery system with tropism for the spleen.

Metabolic Adaptation in Obesity and Type II Diabetes: Myokines, Adipokines and Hepatokines

Obesity and type II diabetes are characterized by insulin resistance in peripheral tissues. A high caloric intake combined with a sedentary lifestyle is the leading cause of these conditions. Whole-body insulin resistance and its improvement are the result of the combined actions of each insulin-sensitive organ. Among the fundamental molecular mechanisms by which each organ is able to communicate and engage in cross-talk are cytokines or peptides which stem from secretory organs. Recently, it was reported that several cytokines or peptides are secreted from muscle (myokines), adipose tissue (adipokines) and liver (hepatokines) in response to certain nutrition and/or physical activity conditions. Cytokines exert autocrine, paracrine or endocrine effects for the maintenance of energy homeostasis. The present review is focused on the relationship and cross-talk amongst muscle, adipose tissue and the liver as secretory organs in metabolic diseases.

Intestinal regeneration as an insect resistance mechanism to entomopathogenic bacteria

The intestinal epithelium of insects is exposed to xenobiotics and entomopathogens during the feeding developmental stages. In these conditions, an effective enterocyte turnover mechanism is highly desirable to maintain integrity of the gut epithelial wall. As in other insects, the gut of lepidopteran larvae have stem cells that are capable of proliferation, which occurs during molting and pathogenic episodes. While much is known on the regulation of gut stem cell division during molting, there is a current knowledge gap on the molecular regulation of gut healing processes after entomopathogen exposure. Relevant information on this subject is emerging from studies of the response to exposure to insecticidal proteins from the bacterium Bacillus thuringiensis (Bt) as model intoxicants. In this work we discuss currently available data on the molecular cues involved in gut stem cell proliferation, insect gut healing, and the implications of enhanced healing as a potential mechanism of resistance against Bt toxins.

Fetuin-A associates with histones intracellularly and shuttles them to exosomes to promote focal adhesion assembly resulting in rapid adhesion and spreading in breast carcinoma cells

The present analyses were undertaken to define the mechanisms by which fetuin-A modulates cellular adhesion. FLAG-tagged fetuin-A was expressed in breast carcinoma and HEK-293T cells. We demonstrated by confocal microscopy that fetuin-A co-localizes with histone H2A in the cell nucleus, forms stable complexes with histones such as H2A and H3 in solution, and shuttles histones to exosomes. The rate of cellular adhesion and spreading to either fibronectin or laminin coated wells was accelerated significantly in the presence of either endogenous fetuin-A or serum derived protein. More importantly, the formation of focal adhesion complexes on surfaces coated by laminin or fibronectin was accelerated in the presence of fetuin-A or histone coated exosomes. Cellular adhesion mediated by histone coated exosomes was abrogated by heparin and heparinase III. Heparinase III cleaves heparan sulfate from cell surface heparan sulfate proteoglycans. Lastly, the uptake of histone coated exosomes and subsequent cellular adhesion, was abrogated by heparin. Taken together, the data suggest a mechanism where fetuin-A, either endogenously synthesized or supplied extracellularly can extract histones from the nucleus or elsewhere in the cytosol/membrane and load them on cellular exosomes which then mediate adhesion by interacting with cell surface heparan sulfate proteoglycans via bound histones.

Reprogramming the specificity of sortase enzymes

Staphylococcus aureus sortase A catalyzes the transpeptidation of an LPXTG peptide acceptor and a glycine-linked peptide donor and has proven to be a powerful tool for site-specific protein modification. The substrate specificity of sortase A is stringent, limiting its broader utility. Here we report the laboratory evolution of two orthogonal sortase A variants that recognize each of two altered substrates, LAXTG and LPXSG, with high activity and specificity. Following nine rounds of yeast display screening integrated with negative selection, the evolved sortases exhibit specificity changes of up to 51,000-fold, relative to the starting sortase without substantial loss of catalytic activity, and with up to 24-fold specificity for their target substrates, relative to their next most active peptide substrate. The specificities of these altered sortases are sufficiently orthogonal to enable the simultaneous conjugation of multiple peptide substrates to their respective targets in a single solution. We demonstrated the utility of these evolved sortases by using them to effect the site-specific modification of endogenous fetuin A in human plasma, the synthesis of tandem fluorophore-protein-PEG conjugates for two therapeutically relevant fibroblast growth factor proteins (FGF1 and FGF2), and the orthogonal conjugation of fluorescent peptides onto surfaces.

The role of fetuin-A in physiological and pathological mineralization

Mineralization in higher vertebrates is restricted to bones and teeth. Pathological calcification is mostly known in vasculature but can basically affect all soft tissues. Simply put, tissue mineralization occurs through the interplay of three key determinants: extracellular matrix suitable for mineralization, extracellular levels of inorganic phosphate and calcium, and the levels of mineralization inhibitors that may be expressed systemically or locally. In this article we describe the role of a prototypic systemic inhibitor protein of mineralization, the hepatic plasma protein α2-Heremans-Schmid glycoprotein/fetuin-A. Fetuin-A mediates the formation of stable colloidal mineral-protein complexes called calciprotein particles (CPPs). Thus, fetuin-A is important in the stabilization and clearance of amorphous mineral precursor phases. Efficient clearance of CPPs and, thus, of excess mineral from circulation prevents local buildup of mineral and calcification of soft tissue. Besides calcium phosphate binding, fetuin-A also acts as a carrier for lipids, which may influence calcification, inflammation, and apoptosis. Fetuin-A-deficient (Ahsg(-/-)) mice show impaired growth of their long bones and premature growth plate closure. We posit that the absence of fetuin-A in the growth plate causes simultaneous lack of calcification inhibition and excess lipid hormone signaling, leading to premature growth plate mineralization and shortened long bones. This suggests that fetuin-A regulates endochondral ossification through mineralization inhibition and lipid (hormone) binding.

Fetuin-A (α2HS-glycoprotein) is a serum chemo-attractant that also promotes invasion of tumor cells through Matrigel

The present study was conducted to determine whether fetuin-A, a dominant serum protein plays a role in chemo-attraction and chemo-invasion of carcinoma cells in vitro. Serum is normally used as positive chemotaxis control in Boyden chamber motility assays, prompting the need to identify the factor/s in serum that contributes the bulk of chemo-taxis and invasion. Serum has a plethora of chemotactic factors including stromal derived factor 1 also known as CXCL12. Using highly purified fetuin-A, we compared its chemo-attraction potential to culture medium containing 10% fetal bovine serum. We also investigated its ability to attract tumor cells through a bed of Matrigel (invasion assay). We demonstrated, using similar concentration range of fetuin-A found in blood, that it robustly supports both directed chemo-attraction and invasion of breast tumor cells. More importantly, we showed that at low concentrations (fetuin-A coated wells) itinteracts synergistically with CXCL12 to promote chemotaxis. The presence of plasminogen (PL) blunted the fetuin-A mediated chemotaxis. Taken together, the data suggest an in vivo chemotaxis/invasion role for fetuin-A.

Measuring movement and location of the gastroesophageal junction: research and clinical implications

Understanding the physiology of gastroesophageal junction (GEJ) is important as failure of its function is associated with reflux disease, hiatus hernia, and cancer. In recent years, there have been impressive developments in high resolution technologies allowing measurement of luminal pressure, pH, and impedance. One obvious deficiency is the lack of technique to monitor the movement and location of the GEJ over a prolonged period of time. Proximal movement of the GEJ during peristalsis and transient lower esophageal sphincter relaxations (TLESRs) is due to shortening of the longitudinal muscle of the esophagus. Techniques for measuring shortening include fluoroscopic imaging of mucosal clip, high-frequency intraluminal ultrasound, and high resolution manometry, but these techniques have limitations. Short segment reflux is recently found to be more common than traditional reflux and may account for the high prevalence of intestinal metaplasia and cancer seen at GEJ. While high resolution pHmetry is available, there is no technique that can reliably and continuously measure the position of the squamocolumnar junction. A new technique is recently reported allowing a precise and continuous measurement of the GEJ based on the principle of Hall effect. Reported studies have validated its accuracy both on the bench and against the gold standard, fluoroscopy. It has been used alongside high resolution manometry in studying the behavior of the GEJ during TLESRs and swallows. While there are challenges associated with this new technique, there are promising ongoing developments. There is exciting time ahead in research and clinical applications for this new technique.

Primate follicular development and oocyte maturation in vitro

The factors and processes involved in primate follicular development are complex and not fully understood. An encapsulated three-dimensional (3D) follicle culture system could be a valuable in vitro model to study the dynamics and regulation of folliculogenesis in intact individual follicles in primates. Besides the research relevance, in vitro follicle maturation (IFM) is emerging as a promising approach to offer options for fertility preservation in female patients with cancer. This review summarizes the current published data on in vitro follicular development from the preantral to small antral stage in nonhuman primates, including follicle survival and growth, endocrine (ovarian steroid hormone) and paracrine/autocrine (local factor) function, as well as oocyte maturation and fertilization. Future directions include major challenges and strategies to further improve follicular growth and differentiation with oocytes competent for in vitro fertilization and subsequent embryonic development, as well as opportunities to investigate primate folliculogenesis by utilizing this 3D culture system. The information may be valuable in identifying optimal conditions for human follicle culture, with the ultimate goal of translating the experimental results and products to patients, thereby facilitating diagnostic and therapeutic approaches for female fertility.

Fetuin-A triggers the secretion of a novel set of exosomes in detached tumor cells that mediate their adhesion and spreading

Our goal in this study was to define the mechanisms by which fetuin-A mediates the adhesion of tumor cells. The data show that in the absence of fetuin-A, detached tumor cells secrete exosomes that contain most of the known exosomal associated proteins but lack the capacity to mediate cellular adhesion. In the presence of fetuin-A, the cells secrete exosomes, which contain, in addition to the other exosomal proteins, fetuin-A, plasminogen and histones. These exosomes mediate adhesion and cell spreading. Plasminogen is a participant in this novel adhesion mechanism. The data suggest that these exosomes play a role in tumor progression.

Enhanced vascular permeability is hypothesized to promote inflammation-induced carcinogenesis and tumor development via extravasation of large molecular proteins into the tissue

We propose that the growth of solid tumors is dependent, in part, on the entry of large molecular blood-borne growth regulators into the tissue and is facilitated by the highly permeable nature of tumor blood vessels. There is abundant evidence that the tumor vasculature is hyperpermeable and tumor growth is dependent on mediators that increase vascular permeability (e.g., VEGF and mast cells). Therefore, the extravasation of plasma proteins into the interstitial space could be an important determinant of tumor growth. Angiogenesis promotes cancer by creating a network of blood vessels that supplies oxygen and nutriment. A highly permeable vasculature could complement this by facilitating the entry of plasma proteins into the tumor space, permitting them to exert effects on growth and survival pathways. Plasma proteins could act directly (on the cancer cells) or indirectly (via the stroma), and could conceivably stimulate cell proliferation, enhance cell survival, promote angiogenesis, and/or provide the cells with essential nutrients. Since increased vascular permeability is a hallmark of inflammation and since chronic inflammation is a forerunner to cancer, we also suggest that the prolonged influx of plasma proteins during chronic inflammation could contribute to the carcinogenic process. Perhaps over time and in sufficient quantity, the extruded plasma proteins and the attendant edema set up a feed-forward cycle that exacerbates the inflammation and potentiates the formation of mutagens and growth regulators. It is tempting to speculate that differences in tumor growth/metastasis and patient outcome are at least partly due to the degree of permeability of the tumor vasculature.

Fetuin-A regulation of calcified matrix metabolism

The final step of biomineralization is a chemical precipitation reaction that occurs spontaneously in supersaturated or metastable salt solutions. Genetic programs direct precursor cells into a mineralization-competent state in physiological bone formation (osteogenesis) and in pathological mineralization (ectopic mineralization or calcification). Therefore, all tissues not meant to mineralize must be actively protected against chance precipitation of mineral. Fetuin-A is a liver-derived blood protein that acts as a potent inhibitor of ectopic mineralization. Monomeric fetuin-A protein binds small clusters of calcium and phosphate. This interaction results in the formation of prenucleation cluster-laden fetuin-A monomers, calciprotein monomers, and considerably larger aggregates of protein and mineral calciprotein particles. Both monomeric and aggregate forms of fetuin-A mineral accrue acidic plasma protein including albumin, thus stabilizing supersaturated and metastable mineral ion solutions as colloids. Hence, fetuin-A is a mineral carrier protein and a systemic inhibitor of pathological mineralization complementing local inhibitors that act in a cell-restricted or tissue-restricted fashion. Fetuin-A deficiency is associated with soft tissue calcification in mice and humans.

Secondary follicle growth and oocyte maturation during encapsulated three-dimensional culture in rhesus monkeys: effects of gonadotrophins, oxygen and fetuin

BACKGROUND

An alginate-based matrix supports the three-dimensional (3D) architecture of non-human primate follicles and, in the presence of FSH, permits the in vitro development of pre-antral follicles to the small antral stage, including the production of ovarian steroids and paracrine factors. The current study investigated the ability of gonadotrophins, fetuin and oxygen (O₂) to improve primate follicle growth and oocyte maturation in vitro.

METHODS

Macaque secondary follicles were isolated from the early follicular phase ovaries, encapsulated in a sodium alginate matrix and cultured individually for 40 days in supplemented medium. The effects of recombinant human (rh) FSH (15, 3 and 0.3 ng/ml for high, medium and low FSH, respectively), bovine fetuin (1 or 0 mg/ml) and O₂ (5 or 20% v/v) were examined. Half of the follicles in each culture condition received rhLH on Day 30-40. Follicles that reached antral stage were treated with rh chorionic gonadotrophin for 34 h to initiate oocyte meiotic maturation. Media were analyzed for ovarian steroids and anti-müllerian hormone (AMH).

RESULTS

Improved culture conditions supported non-human primate, secondary follicle growth to the antral stage and, for the first time, promoted oocyte maturation to the MII stage. In the presence of fetuin at 5% O₂, follicles had the highest survival rate if cultured with high or medium FSH, whereas follicles grew to larger diameters at Week 5 in low FSH. Oocyte health and maturation were promoted under 5% O₂. High FSH stimulated steroid production by growing follicles, and steroidogenesis by follicles cultured with low FSH was promoted by LH. AMH biosynthesis was elevated with high compared with low FSH and for longer under 5% O₂ than under 20% O₂.

CONCLUSIONS

This encapsulated 3D culture model permits further studies on the endocrine and local factors that influence primate follicle growth and oocyte maturation, with relevance to enhancing fertility preservation options in women.

Fetuin-A ({alpha}2HS-glycoprotein) is a major serum adhesive protein that mediates growth signaling in breast tumor cells

The identity of the cell adhesive factors in fetal bovine serum, commonly used to supplement growth media, remains a mystery due to the plethora of serum proteins. In the present analyses, we showed that fetuin-A, whose function in cellular attachment in tissue culture has been debated for many years, is indeed a major serum cell attachment factor particularly for tumor cells. We are able to report this because of a new purification strategy that has for the first time given us a homogeneous protein band in colloidal Coomassie-stained gels that retains biological activity. The tumor cells adhered to immobilized fetuin-A and not α(2)-macroglobulin, its major contaminant. The interaction of cells with fetuin-A was driven mainly by Ca(2+) ions, and cells growing in regular medium supplemented with fetal bovine serum were just as sensitive to loss of extracellular Ca(2+) ions as cells growing in fetuin-A. Fractionation of human serum revealed that cell attachment was confined to the fractions that had fetuin-A. Interestingly, the tumor cells also took up fetuin-A and secreted it back to the medium using an unknown mechanism that can be observed in live cells. The attachment of tumor cells to fetuin-A was accompanied by phosphatidylinositol 3-kinase/Akt activation that was down-regulated in cells that lack annexin-A6, one of the cell surface receptors for fetuin-A. Taken together, our data show the significance of fetuin-A in tumor cell growth mechanisms in vitro and open new research vistas for this protein.

Lack of fetuin-A (alpha2-HS-glycoprotein) reduces mammary tumor incidence and prolongs tumor latency via the transforming growth factor-beta signaling pathway in a mouse model of breast cancer

The present analyses were done to define the role of fetuin-A (Fet) in mammary tumorigenesis using the polyoma middle T antigen (PyMT) transgenic mouse model. We crossed Fet-null mice in the C57BL/6 background with PyMT mice in the same background and after a controlled breeding protocol obtained PyMT/Fet+/+, PyMT/Fet+/-, and PyMT/Fet-/- mice that were placed in control and experimental groups. Whereas the control group (PyMT/Fet+/+) formed mammary tumors 90 days after birth, tumor latency was prolonged in the PyMT/Fet-/- and PyMT/Fet+/- mice. The majority of the PyMT/Fet-/- mice were tumor-free at the end of the study, at approximately 40 weeks. The pathology of the mammary tumors in the Fet-null mice showed extensive fibrosis, necrosis, and squamous metaplasia. The preneoplastic mammary tissues of the PyMT/Fet-/- mice showed intense phopho-Smad2/3 staining relative to control tissues, indicating that transforming growth factor-β signaling is enhanced in these tissues in the absence of Fet. Likewise, p19ARF and p53 were highly expressed in tumor tissues of PyMT/Fet-/- mice relative to the controls in the absence of Fet. The phosphatidylinositol 3-kinase/Akt signaling pathway that we previously showed to be activated by Fet, on the other hand, was unaffected by the absence of Fet. The data indicate that Fet is a powerful modulator of breast tumorigenesis in this model system and has the potential to modulate breast cancer progression in humans.

Cystatin superfamily

Cystatins, the classical inhibitors of C1 cysteine proteinases, have been extensively studied and reviewed in the literature. Over the last 20 years, however, proteins containing cystatin domains but lacking protease inhibitory activities have been identified, and most likely more will be described in the near future. These proteins together with family 1, 2, and 3 cystatins constitute the cystatin superfamily. Mounting evidence points to the new roles that some members of the superfamily have acquired over the course of their evolution. This review is focused on the roles of cystatins in: 1) tumorigenesis, 2) stabilization of matrix metalloproteinases, 3) glomerular filtration rate, 4) immunomodulation, and 5) neurodegenerative diseases. It is the goal of this review to get as many investigators as possible to take a second look at the cystatin superfamily regarding their potential involvement in serious human ailments.

The physiologic development of fetuin-a serum concentrations in children

Fetuin-A prevents tissue calcification by forming soluble complexes with calcium and phosphate. A pathological depletion of serum fetuin-A has been observed in children on dialysis or after renal transplantation but knowledge on physiologic age-related changes in serum fetuin-A is limited. We prospectively evaluated serum fetuin-A in 133 infants and children, ranging from very low birth weight infants to adolescents. Highest serum fetuin-A levels were present between 23 and 30 wk of gestation (1 +/- 0.33 mg/mL). Thereafter, the values decreased. This decrease was linked to biological rather than chronological age. At 32 to 36 and 37 to 40 wk of gestation, the serum fetuin-A concentration was 0.63 +/- 0.26 and 0.63 +/- 0.21 mg/mL, respectively. Thereafter, the concentrations remained stable until adolescence at 0.58 +/- 0.12 mg/mL. Intercurrent infections were associated with a transient decrease of serum fetuin-A levels. The high serum fetuin-A concentrations in preterm children suggest that fetuin-A is of high physiologic impact for the fetal and the preterm-born organism, showing extensive tissue formation. This might point to a new mechanism contributing to organ damage in these patients, comparable with children on dialysis.

Roles of gastro-oesophageal afferents in the mechanisms and symptoms of reflux disease

Oesophageal pain is one of the most common reasons for physician consultation and/or seeking medication. It is most often caused by acid reflux from the stomach, but can also result from contractions of the oesophageal muscle. Different forms of pain are evoked by oesophageal acid, including heartburn and non-cardiac chest pain, but the basic mechanisms and pathways by which these are generated remain to be elucidated. Both vagal and spinal afferent pathways are implicated by basic research. The sensitivity of afferent fibres within these pathways may become altered after acid-induced inflammation and damage, but the severity of symptoms in humans does not necessarily correlate with the degree of inflammation. Gastro-oesophageal reflux disease (GORD) is caused by transient relaxations of the lower oesophageal sphincter, which are triggered by activation of gastric vagal mechanoreceptors. Vagal afferents are therefore an emerging therapeutic target for GORD. Pain in the absence of excess acid reflux remains a major challenge for treatment.

Anchorage-independent growth of breast carcinoma cells is mediated by serum exosomes

We hereby report studies that suggest a role for serum exosomes in the anchorage-independent growth (AIG) of tumor cells. In AIG assays, fetal bovine serum is one of the critical ingredients. We therefore purified exosomes from fetal bovine serum and examined their potential to promote growth of breast carcinoma cells in soft agar and Matrigel after reconstituting them into growth medium (EEM). In all the assays, viable colonies were formed only in the presence of exosomes. Some of the exosomal proteins we identified, have been documented by others and could be considered exosomal markers. Labeled purified exosomes were up-taken by the tumor cells, a process that could be competed out with excess unlabeled vesicles. Our data also suggested that once endocytosed by a cell, the exosomes could be recycled back to the conditioned medium from where they can be up-taken by other cells. We also demonstrated that low concentrations of exosomes activate MAP kinases, suggesting a mechanism by which they maintain the growth of the tumor cells in soft agar. Taken together, our data demonstrate that serum exosomes form a growth promoting platform for AIG of tumor cells and may open a new vista into cancer cell growth in vivo.

Role of immunogenic fetuin A on L5178Y-R lymphoma tumorigenesis

In the present study, we report the detection of immunogenic fetuin-A on L5178Y-R (LY-R) lymphoma cells. Fetuin-A was recognized by antibodies present in the serum of LY-R tumor-bearing and immunized mice, but not by sera of mice immunized with the non-tumorigenic variant LY-S or by healthy mouse sera. However, according with Western blot analysis with commercial anti-fetuin antibodies, fetuin-A is present in both cell types which suggests that the fetuin recognized by anti-LY-R antibodies is an immunogenic form associated only with the tumorigenic LY-R cells and might be involved in tumor progression in this lymphoma.

Pathogenesis of gastro-oesophageal reflux disease and novel options for its therapy

Better understanding of the mechanisms that lead to reflux disease is an important area for future research, given the very high prevalence of this problem. During the lifetime of this journal, much has been learnt about the pathophysiology of reflux disease. Abnormally, frequent acid reflux plays a key role in pathogenesis: this reflux occurs predominantly during transient lower oesophageal sphincter relaxations. Analysis of the literature suggests that the importance of transient relaxations as the major permissive event for occurrence of acid reflux is currently substantially underestimated. 'Transient relaxation' is an inexact descriptor, as this motor programme includes inhibition of the diaphragmatic hiatus and distal oesophageal body circular muscle and contraction of the oesophageal longitudinal muscle. Laxity of the diaphragmatic hiatus and hiatus hernia are probably important factors that increase the probability for acid reflux to occur during transient relaxations and in allowing strain-induced reflux episodes. The importance of straining and low basal tone of the lower oesophageal sphincter in causing abnormal reflux has probably been overestimated, but these need more investigation. High resolution manometry is the key method for acquisition of important new insights into the normal and disordered mechanics of the antireflux function of the gastro-oesophageal junction, but as yet, the potential of this technique has been tapped relatively little. In the future, improved understanding of the mechanics of the gastro-oesophageal junction should lead to improved physical antireflux procedures. Much progress has been made in defining the control of transient relaxations and this has been translated into several promising options for a new class of drug that treats reflux disease by inhibition of transient relaxations. Clinical trials on these agents appear imminent.

Concise Review: No Breakthroughs for Human Mesenchymal and Embryonic Stem Cell Culture: Conditioned Medium, Feeder Layer, or Feeder-Free; Medium with Fetal Calf Serum, Human Serum, or Enriched Plasma; Serum-Free, Serum Replacement Nonconditioned Medium, or Ad Hoc Formula? All That Glitters Is Not Gold!

The choice of an optimal strategy of stem cell culture is at the moment an impossible task, and the elaboration of a culture medium adapted to the production of embryonic and adult mesenchymal stem cells for the clinical application of cell therapy remains a crucial matter. To make an informed choice, it is crucial to not underestimate the theoretical health risk of using xenogenic compounds, to limit the immunological reactions once stem cells are transplanted, to not overestimate the controversial results obtained with human serum, plasma, and blood derivatives, as well as to carefully examine the pros and cons of serum-free and ad hoc formulation strategies; besides that, to also maintain multipotentiality, self-renewal, and transplantability. The extent to which we are able to achieve effective cell therapies will depend on assimilating a rapidly developing base of scientific knowledge with the practical considerations of design, delivery, and host response. Although clinical studies have already started, many questions remain unsolved, and concomitantly even more evidence on suitable and safe off-the-shelf products (mainly xeno-free) for embryonic and mesenchymal stem cells is cropping up, even though there should be no rush to enter the clinical stage while the underlying basic research is still not so solid; this solely will lead to high-quality translational research, without making blunders stemming from the assumption that all that glitters is not gold. Disclosure of potential conflicts of interest is found at the end of this article.

Proteolytic processing by matrix metalloproteinases and phosphorylation by protein kinase CK2 of fetuin-A, the major globulin of fetal calf serum

Bovine fetuin-A is a member of a glycoprotein family with a wide spectrum of functions. Until now the bovine protein has been thought to be a single-chain protein. Recently we have shown that native bovine plasma fetuin-A partially exists as a disulfide-bridged two-chain protein with a heavy N-terminal and a lighter C-terminal chain similar to the structure of human fetuin-A homologue (alpha2HS glycoprotein), and also is partially phosphorylated at residues Ser120, Ser302, Ser305 and Ser306 (Wind et al., Anal. Biochem. 317 (2003) 26-33). Both fetuin-A modifications, the phosphorylation at the four sites as well as the proteolysis which causes longer or shorter light chains (termed lc-1 and lc-2, respectively), are probably brought about by targeted enzymatic activities which still need to be defined. In this study we show that authentic bovine fetuin-A disulfide-bridged two-chain forms, which include the original C-terminus, were liberated from the single-chain precursor by metalloproteinases MMP-3 (stromelysin-1) and MMP-7 (matrilysin), but not by elastase, cathepsin E and cathepsin G. Peptide sequencing suggested cleavage sites chiefly at the Pro277-Ser278 or Arg294-His295 peptide bonds. Fetuin-A radioactive phosphorylation in vitro by protein kinase CK2 caused (32)P incorporation into the fetuin-A light chain lc-1 but not lc-2 or the fetuin-A heavy chain, as revealed by MMP assisted proteolysis. Analysis by nanoESI-MS pinpointed phosphorylation at the native phospho-residues Ser302, Ser305 and Ser306 by increased relative abundance following in vitro phosphorylation. Moreover, CK2 phosphorylation of synthetic C-terminal fetuin-A peptides, used as effective controls to the native protein, strongly implies that CK2 is involved in the in vivo phosphorylation of fetuin-A. The phosphorylation of N-terminally truncated peptide homologs seemed highly dependent on the sequence context N-terminal of the phosphorylation sites, thus providing a likely explanation for the non-phosphorylation of the light chain lc-2 in native fetuin-A.

Review article: from 1906 to 2006--a century of major evolution of understanding of gastro-oesophageal reflux disease

BACKGROUND

Our understanding of gastro-oesophageal reflux disease has undergone significant changes over the last century.

AIM

To trace the rise in understanding of gastro-oesophageal reflux disease and highlight remaining areas of uncertainty.

METHODS

Literature review.

RESULTS

In 1906, Tileston published his observations on 'peptic ulcer of the oesophagus'. Winkelstein, in 1934, first correlated symptoms of heartburn with acid regurgitation and reflux oesophagitis. In 1946, Allison described hiatus hernia as a causal factor in the development of gastro-oesophageal reflux disease. In 1958, Bernstein and Baker showed a direct relationship between oesophageal acidification and heartburn in patients with gastro-oesophageal reflux disease, irrespective of endoscopic findings, leading to the recognition of non-erosive gastro-oesophageal reflux disease. In the 1980s, continuous recordings of the lower oesophageal sphincter showed that episodes of reflux were related to transient relaxations of lower oesophageal sphincter tone. There is now increasing recognition that gastro-oesophageal reflux disease arises from the interaction of several anatomical and physiological factors. A turning point in the medical treatment of gastro-oesophageal reflux disease came with the introduction of the first proton pump inhibitor, omeprazole, in 1989.

CONCLUSIONS

Future efforts need to identify the multifactorial interactions of gastro-oesophageal junction anatomy and physiology in patients with gastro-oesophageal reflux disease. Increased understanding of the disease will guide development of new therapies.

Tissue-engineered follicles produce live, fertile offspring

Oocytes grown in vitro are of low quality and yield few live births, thus limiting the ability to store or bank the ova of women wishing to preserve their fertility. We applied tissue engineering principles to the culture of immature mouse follicles by designing an alginate hydrogel matrix to maintain the oocyte's 3- dimensional (3D) architecture and cell-cell interactions in vitro. A 3D culture mimics the in vivo follicle environment, and hydrogel-encapsulated follicles develop mature oocytes within the capacity for fertilization similar to that of oocytes matured in vivo. Embryos derived from cultured oocytes fertilized in vitro and transferred to pseudopregnant female mice were viable, and both male and female offspring were fertile. Our results demonstrate that alginate hydrogel-based 3D in vitro culture of follicles permits normal growth and development of follicles and oocytes. This system creates new opportunities for discovery in follicle biology and establishes a core technology for human egg banks for preservation of fertility.

The Serum Glycoprotein Fetuin-A Promotes Lewis Lung Carcinoma Tumorigenesis via Adhesive-Dependent and Adhesive-Independent Mechanisms

Fetuin-A is a serum glycoprotein in the cystatin family associated with the regulation of soft tissue calcification. We tested the role of systemic fetuin in tumor cell growth and metastasis by injecting Lewis lung carcinoma (LLC) cells into fetuin-A null and their wild-type (WT) littermate control C57BL/6 mice via the tail vein, s.c., and intrasplenic routes. In the experimental metastasis assay, the lungs of the WT mice were filled with metastatic nodules, whereas the lungs of the fetuin-A null mutant mice were virtually free of colonies at the end of 2 weeks. Lung colonization responded to the levels of serum fetuin-A in a dose-dependent manner, as observed by the formation of half as many colonies in mice heterozygous for the fetuin-A locus compared with homozygous WT mice and restoration of lung colonization by the administration of purified fetuin-A to fetuin-A-null mice. Serum fetuin-A also influenced the growth of LLC cells injected s.c.: fetuin-A-null mice developed small s.c. tumors only after a substantial delay. Similarly, intrasplenic injection of LLC cells resulted in rapid colonization of the liver with metastasis to the lungs within 2 weeks in the WT but not fetuin-A null mice. To examine the mechanism by which fetuin-A influences LLC colonization and growth, we showed that LLC tumor cells adhere to fetuin-A in a Ca2+-dependent fashion, resulting in growth of the tumor cells. These studies support the role of fetuin-A as a major growth promoter in serum that can influence tumor establishment and growth.

Annexins expressed on the cell surface serve as receptors for adhesion to immobilized fetuin-A

Fetuin-A is a major constituent of the fetal bovine serum used extensively in cell culture media. We hereby present data demonstrating that breast carcinoma cells can adhere to immobilized fetuin-A in a calcium-dependent fashion. Interestingly, the cells can also divide and attain confluency under these conditions. Using a proteomic approach, we have identified annexin-II and -VI as the putative cell surface receptors for fetuin-A in the presence of Ca2+ ions. Biotinylation of cell surface proteins followed by immunoprecipitation revealed that annexin-VI was expressed on the extracytoplasmic surface of the cell membranes. Finally, to demonstrate that annexin-II and -VI were the adhesive receptors for fetuin-A, siRNA knockdown of expression of the annexins significantly reduced the calcium-mediated adhesion. Interestingly, we demonstrated that the tumor cells could also adhere to immobilized fetuin-A in the presence of magnesium ions, and that this adhesion was most likely mediated by integrins because neutralizing antibodies against beta1 integrins substantially reduced the adhesion. Our studies suggest that the expression of annexin-II and -VI and possibly other members of the family mediate novel adhesion and signaling mechanisms in tumor cells.

The role of hiatus hernia in gastro-oesophageal reflux disease

This article gives an overview of the role of sliding hiatus hernia in gastro-oesophageal reflux disease (GORD). The crural diaphragm acts as an external sphincter of the anti-reflux barrier. Contractions of the crural diaphragm increase lower-oesophageal-sphincter (LOS) pressure during each inspiration and in situations of increased abdominal pressure, whereas these contractions are inhibited when gas and/or a bolus has to pass the gastro-oesophageal junction. A hiatus hernia is associated with GORD symptoms, increased oesophageal acid exposure, and oesophagitis and its severity. In patients with hiatus hernia, the incidence of reflux episodes is increased during periods with low LOS pressure, straining and swallowing. These findings underline the importance of the crural diaphragm, which, when surrounding the LOS, protects against gastro-oesophageal reflux.

Members of the cystatin superfamily interact with MMP-9 and protect it from autolytic degradation without affecting its gelatinolytic activities

Matrix metalloproteinases (MMPs), like other proteinases, can undergo autolytic degradation once activated in vivo. Whereas the activities of these enzymes are tightly regulated by tissue inhibitors of matrix metalloproteinases (TIMPs), it is not clear mechanistically how these enzymes are protected from autolysis in their active state. We previously reported that MMPs particularly MMP-9 and MMP-2 interact with the serum glycoprotein fetuin-A [Arch. Biochem. Biophys. (1995) 322, 250], a member of the cystatin superfamily. In the present analyses, we demonstrate that this interaction protects MMP-9 from autolytic degradation without interfering with its enzymatic activity, allowing it to efficiently digest gelatin. Our data demonstrate that MMP-9 binds to members of the cystatin family with K(diss) ranging from 25 to 58 nM for fetuin-A and 1.5-1.9 microM for cystatin C. The ability of fetuin-A to protect MMP-9 from autolysis requires a molar ratio of at least 8:1 (fetuin-A/MMP-9). More interestingly, our data show that the other members of the cystatin also have the ability to protect MMP-9 from autolysis, provided they are in molar excess relative to MMP-9. Taken together, our data suggest that cystatins, particularly fetuin-A, in any cellular compartment including the circulatory system, efficiently protect MMP-9 and possibly other MMPs from autolysis. This mechanism ensures the digestion of the preferred substrate for MMP-9 without sacrificing the enzyme in the process.