A proteome study of secreted prostatic factors affecting osteoblastic activity: galectin-1 is involved in differentiation of human bone marrow stromal cells

DNA methylation of promoter region inhibits galectin-1 expression in BMSCs of aged mice

Senile osteoporosis increases fracture risks. Bone marrow stromal cells (BMSCs) are sensitive to aging. Deep insights into BMSCs aging are vital to elucidate the mechanisms underlying age-related bone loss. Recent advances showed that osteoporosis is associated with aberrant DNA methylation of many susceptible genes. Galectin-1 (Gal-1) has been proposed as a mediator of BMSCs functions. In our previous study, we showed that Gal-1 was downregulated in aged BMSCs and global deletion of Gal-1 in mice caused bone loss via impaired osteogenesis potential of BMSCs. Gal-1 promoter is featured by CpG islands. However, there are no reports concerning the DNA methylation status in Gal-1 promoter during osteoporosis. In the current study, we sought to investigate the role of DNA methylation in Gal-1 downregulation in aged BMSCs. The potential for anti-bone loss therapy based on modulating DNA methylation is explored. Our results showed that Dnmt3b-mediated Gal-1 promoter DNA hypermethylation plays an important role in Gal-1 downregulation in aged BMSCs, which inhibited β-catenin binding on Gal-1 promoter. Bone loss of aged mice was alleviated in response to in vivo deletion of Dnmt3b from BMSCs. Finally, when bone marrow of young wild-type (WT) mice or young Dnmt3bPrx1-Cre mice was transplanted into aged WT mice, Gal-1 level in serum and trabecular bone mass were elevated in recipient aged WT mice. Our study will benefit for deeper insights into the regulation mechanisms of Gal-1 expression in BMSCs during osteoporosis development, and for the discovery of new therapeutic targets for osteoporosis via modulating DNA methylation status.NEW & NOTEWORTHY There is Dnmt3b-mediated DNA methylation in Gal-1 promoter in aged bone marrow stromal cell (BMSC). DNA methylation causes Gal-1 downregulation and osteogenesis attenuation of aged BMSC. DNA methylation blocks β-catenin binding on Gal-1 promoter. Bone loss of aged mice is alleviated by in vivo deletion of Dnmt3b from BMSC.

Reduced form of Galectin-1 Suppresses Osteoclastic Differentiation of Human Peripheral Blood Mononuclear Cells and Murine RAW264 Cells In Vitro

Galectin-1 (Gal-1) is an evolutionarily conserved sugar-binding protein found in intra- and extracellular spaces. Extracellularly, it binds to glycoconjugates with β-galactoside(s) and functions in various biological phenomena, including immunity, cancer, and differentiation. Under extracellular oxidative conditions, Gal-1 undergoes oxidative inactivation, losing its sugar-binding ability, although it exhibits sugar-independent functions. An age-related decrease in serum Gal-1 levels correlates with decreasing bone mass, and Gal-1 knockout promotes osteoclastic bone resorption and suppresses bone formation. However, the effect of extracellular Gal-1 on osteoclast differentiation remains unclear. Herein, we investigated the effects of extracellular Gal-1 on osteoclastogenesis in human peripheral blood mononuclear cells (PBMCs) and mouse macrophage RAW264 cells. Recombinant Gal-1 suppressed the macrophage colony-stimulating factor and receptor activator of nuclear factor-κB ligand-dependent osteoclast formation, actin ring formation, and bone-resorption activity of human PBMCs. Similar results were obtained for RAW264 cells. Gal-1 knockdown increased osteoclast-like cell formation, suggesting that it affected differentiation in an autocrine-like manner. Oxidized Gal-1 slightly affected differentiation, and in the presence of lactose, the differentiation inhibitory effect of galectin-1 was not observed. These findings suggest that extracellular Gal-1 inhibits osteoclast differentiation in a β-galactoside-dependent manner, and an age-related decrease in serum Gal-1 levels may contribute to reduced osteoclast activity and decreasing bone mass.

Galectin-1 deletion in mice causes bone loss via impaired osteogenic differentiation potential of BMSCs

Bone formation is dependent on the osteoblasts which are differentiated from bone marrow stromal cells (BMSCs). In addition to potent proliferation, self-renewal, and pluripotent differentiation, BMSCs have been extensively studied due to their low immunogenicity and immunomodulatory effects. Recently, galectin-1 (Gal-1) has been proposed as a potent mediator of immunomodulatory properties of BMSCs. Previous study demonstrated that Gal-1 showed age-related decline in mice serum and serum Gal-1 was positively associated with bone mass in mice. The current study makes attempts to elucidate the functional role of Gal-1 in skeletal system by investigating the regulation of Gal-1 expression during BMSCs osteogenic differentiation and the molecular mechanisms underlying the effects of Gal-1 on BMSCs osteogenic differentiation. In Gal-1 null (-/-) mice, bone loss was observed due to bone formation attenuation. In in vitro experiments, Gal-1 supported the osteogenic differentiation of BMSCs by binding to CD146 to activate Lrp5 expression and Wnt/β-catenin signaling pathway. Meanwhile, there was positive feedback regulation via Wnt/β-catenin signaling to maintain Gal-1 high-level expression during osteogenic differentiation of BMSCs. More importantly, Gal-1 down-regulation in BMSCs and attenuation of osteogenic differentiation potential of BMSCs were observed in aged mice compared with young mice. Gal-1 over-expression could enhance osteogenic differentiation potential of aged BMSCs. Our study will benefit not only for deeper insights into the functional role of Gal-1 but also for finding new targets to modulate BMSCs osteogenic differentiation.

Alginate bone scaffolds coated with a bioactive lactose modified chitosan for human dental pulp stem cells proliferation and differentiation

Bioactive and biodegradable porous scaffolds can hasten the healing of bone defects; moreover, patient stem cells seeded onto scaffolds can enhance the osteoinductive and osteoconductive properties of these biomaterials. In this work, porous alginate/hydroxyapatite scaffolds were functionalized with a bioactive coating of a lactose-modified chitosan (CTL). The highly interconnected porous structure of the scaffold was homogeneously coated with CTL. The scaffolds showed remarkable stability up to 60 days of aging. Human Dental Pulp Stem Cells (hDPSCs) cultured in the presence of CTL diluted in culture medium, showed a slight and negligible increase in terms of proliferation rate; on the contrary, an effect on osteogenic differentiation of the cells was observed as a significant increase in alkaline phosphatase activity. hDPSCs showed higher cell adhesion on CTL-coated scaffolds than on uncoated ones. CTL coating did not affect cell proliferation, but stimulated cell differentiation as shown by alkaline phosphatase activity analysis.

Age-related trabecular bone loss is associated with a decline in serum Galectin-1 level

BACKGROUND

Senile osteoporosis with age-related bone loss is diagnosed depending on radiographic changes of bone and bone mineral density (BMD) measurement. However, radiographic alterations are usually signs of medium-late stage osteoporosis. Therefore, biomarkers have been proposed as indicators of bone loss. In the current study, Galectin-1 (Gal-1) showed age-related decline in mice serum. The role of Gal-1 in osteoporosis has not been investigated so far. Hence, the current study illustrated the relationship of serum Gal-1 level with bone loss.

METHODS

We employed 6- and 18-month-old mice to establish an animal model of age-related trabecular bone loss, whose bone density and microstructure were investigated by micro-CT. ELISA was used to measure the levels of Gal-1 in serum. The correlation analysis was performed to illustrate the relationship between serum Gal-1 levels and trabecular bone loss. In addition, immunohistochemistry was used to investigate the abundance of Gal-1 in bone marrow of mice. ELISA and western blot were performed to measure the secretion ability and protein expression of Gal-1 in bone marrow stromal cells (BMSC), hematopoietic stem cells (HSC) and myeloid progenitor (MP) respectively. Flow cytometry was used to measure BMSC number in bone marrow. Finally, male volunteers with age-related BMD decrease were recruited and the relationship between serum Gal-1 and BMD was analyzed.

RESULTS

Gal-1 showed age-related decline in mice serum. Serum Gal-1 was positively associated with BV/TV of femur, tibia and L1 vertebrae in mice. BMSC secreted more Gal-1 compared with HSC and MP. BMSC number in bone marrow was significantly lower in aged mice compared with young mice. Significant attenuation of Gal-1 protein expression was observed in BMSC and HSC from aged mice compared with young mice. Further, we found a decline in serum Gal-1 levels in men with age-related BMD decrease. There was positive correlation between BMD and serum Gal-1 levels in these men.

CONCLUSIONS

Age-related trabecular bone loss is associated with a decline in serum Gal-1 level in mice and men. Our study suggested Gal-1 had great potential to be a biomarker for discovering BMSC senescence, diagnosing early osteoporosis and monitoring trabecular bone loss.

The Expression and Function of Metastases Associated Lung Adenocarcinoma Transcript-1 Long Non-Coding RNA in Subchondral Bone and Osteoblasts from Patients with Osteoarthritis

Metastasis Associated Lung Adenocarcinoma Transcript-1 (MALAT1) is implicated in regulating the inflammatory response and in the pathology of several chronic inflammatory diseases, including osteoarthritis (OA). The purpose of this study was to examine the relationship between OA subchondral bone expression of MALAT1 with parameters of joint health and biomarkers of joint inflammation, and to determine its functional role in human OA osteoblasts. Subchondral bone and blood were collected from hip and knee OA patients (n = 17) and bone only from neck of femur fracture patients (n = 6) undergoing joint replacement surgery. Cytokines were determined by multiplex assays and ELISA, and gene expression by qPCR. MALAT1 loss of function was performed in OA patient osteoblasts using locked nucleic acids. The osteoblast transcriptome was analysed by RNASeq and pathway analysis. Bone expression of MALAT1 positively correlated to serum DKK1 and galectin-1 concentrations, and in OA patient osteoblasts was induced in response to IL-1β stimulation. Osteoblasts depleted of MALAT1 exhibited differential expression (>1.5 fold change) of 155 genes, including PTGS2. Both basal and IL-1β-mediated PGE2 secretion was greater in MALAT1 depleted osteoblasts. The induction of MALAT1 in human OA osteoblasts upon inflammatory challenge and its modulation of PGE2 production suggests that MALAT1 may play a role in regulating inflammation in OA subchondral bone.

Communications Between Bone Marrow Macrophages and Bone Cells in Bone Remodeling

The mammalian skeleton is a metabolically active organ that continuously undergoes bone remodeling, a process of tightly coupled bone resorption and formation throughout life. Recent studies have expanded our knowledge about the interactions between cells within bone marrow in bone remodeling. Macrophages resident in bone (BMMs) can regulate bone metabolism via secreting numbers of cytokines and exosomes. This review summarizes the current understanding of factors, exosomes, and hormones that involved in the communications between BMMs and other bone cells including mensenchymal stem cells, osteoblasts, osteocytes, and so on. We also discuss the role of BMMs and potential therapeutic approaches targeting BMMs in bone remodeling related diseases such as osteoporosis, osteoarthritis, rheumatoid arthritis, and osteosarcoma.

The Emerging Role of Galectins and O-GlcNAc Homeostasis in Processes of Cellular Differentiation

Galectins are a family of soluble β-galactoside-binding proteins with diverse glycan-dependent and glycan-independent functions outside and inside the cell. Human cells express twelve out of sixteen recognized mammalian galectin genes and their expression profiles are very different between cell types and tissues. In this review, we summarize the current knowledge on the changes in the expression of individual galectins at mRNA and protein levels in different types of differentiating cells and the effects of recombinant galectins on cellular differentiation. A new model of galectin regulation is proposed considering the change in O-GlcNAc homeostasis between progenitor/stem cells and mature differentiated cells. The recognition of galectins as regulatory factors controlling cell differentiation and self-renewal is essential for developmental and cancer biology to develop innovative strategies for prevention and targeted treatment of proliferative diseases, tissue regeneration, and stem-cell therapy.

Galectins in prostate and bladder cancer: tumorigenic roles and clinical opportunities

Advanced prostate and bladder cancer are two outstanding unmet medical needs for urological oncologists. The high prevalence of these tumours, lack of effective biomarkers and limited effective treatment options highlight the importance of basic research in these diseases. Galectins are a family of β-galactoside-binding proteins that are frequently altered (upregulated or downregulated) in a wide range of tumours and have roles in different stages of tumour development and progression, including immune evasion. In particular, altered expression levels of different members of the galectin family have been reported in prostate and bladder cancers, which, together with the aberrant glycosylation patterns found in tumour cells and the constituent cell types of the tumour microenvironment, can result in malignant transformation and tumour progression. Understanding the roles of galectin family proteins in the development and progression of prostate and bladder cancer could yield key insights to inform the clinical management of these diseases.

Trypanosoma cruzi cleaves galectin-3 N-terminal domain to suppress its innate microbicidal activity

Galectin-3 is the best-characterized member of galectins, an evolutionary conserved family of galactoside-binding proteins that play central roles in infection and immunity, regulating inflammation, cell migration and cell apoptosis. Differentially expressed by cells and tissues with immune privilege, they bind not only to host ligands, but also to glycans expressed by pathogens. In this regard, we have previously shown that human galectin-3 recognizes several genetic lineages of the protozoan parasite Trypanosoma cruzi, the causal agent of Chagas' disease or American trypanosomiasis. Herein we describe a molecular mechanism developed by T. cruzi to proteolytically process galectin-3 that generates a truncated form of the protein lacking its N-terminal domain - required for protein oligomerization - but still conserves a functional carbohydrate recognition domain (CRD). Such processing relies on specific T. cruzi proteases, including Zn-metalloproteases and collagenases, and ultimately conveys profound changes in galectin-3-dependent effects, as chemical inhibition of parasite proteases allows galectin-3 to induce parasite death in vitro. Thus, T. cruzi might have established distinct mechanisms to counteract galectin-3-mediated immunity and microbicide properties. Interestingly, non-pathogenic T. rangeli lacked the ability to cleave galectin-3, suggesting that during evolution two genetically similar organisms have developed different molecular mechanisms that, in the case of T. cruzi, favoured its pathogenicity, highlighting the importance of T. cruzi proteases to avoid immune mechanisms triggered by galectin-3 upon infection. This study provides the first evidence of a novel strategy developed by T. cruzi to abrogate signalling mechanisms associated with galectin-3-dependent innate immunity.

Macrophage-Derived Extracellular Vesicles as Carriers of Alarmins and Their Potential Involvement in Bone Homeostasis

Extracellular vesicles are a heterogeneous group of cell-derived membranous structures, which facilitate intercellular communication. Recent studies have highlighted the importance of extracellular vesicles in bone homeostasis, as mediators of crosstalk between different bone-resident cells. Osteoblasts and osteoclasts are capable of releasing various types of extracellular vesicles that promote both osteogenesis, as well as, osteoclastogenesis, maintaining bone homeostasis. However, the contribution of immune cell-derived extracellular vesicles in bone homeostasis remains largely unknown. Recent proteomic studies showed that alarmins are abundantly present in/on macrophage-derived EVs. In this review we will describe these alarmins in the context of bone matrix regulation and discuss the potential contribution macrophage-derived EVs may have in this process.

Inducing hair follicle neogenesis with secreted proteins enriched in embryonic skin

Organ development is a sophisticated process of self-organization. However, despite growing understanding of the developmental mechanisms, little is known about how to reactivate them postnatally for regeneration. We found that treatment of adult non-hair fibroblasts with cell-free extract from embryonic skin conferred upon them the competency to regenerate hair follicles. Proteomics analysis identified three secreted proteins enriched in the embryonic skin, apolipoprotein-A1, galectin-1 and lumican that together were essential and sufficient to induce new hair follicles. These 3 proteins show a stage-specific co-enrichment in the perifolliculogenetic embryonic dermis. Mechanistically, exposure to embryonic skin extract or to the combination of the 3 proteins altered the gene expression to an inductive hair follicle dermal papilla fibroblast-like profile and activated Igf and Wnt signaling, which are crucial for the regeneration process. Therefore, a cocktail of organ-specific extracellular proteins from the embryonic environment can render adult cells competent to re-engage in developmental interactions for organ neogenesis. Identification of factors that recreate the extracellular context of respective developing tissues can become an important strategy to promote regeneration in adult organs.

Galectins as new prognostic markers and potential therapeutic targets for advanced prostate cancers

A better understanding of multimolecular interactions involved in tumor dissemination is required to identify new effective therapies for advanced prostate cancer (PCa). Several groups investigated protein-glycan interactions as critical factors for crosstalk between prostate tumors and their microenvironment. This review both discusses whether the “galectin-signature” might serve as a reliable biomarker for the identification of patients with high risk of metastasis and assesses the galectin-glycan lattices as potential novel targets for anticancer therapies. The ultimate goal of this review is to convey how basic findings related to galectins could be in turn translated into clinical settings for patients with advanced PCa.

The gap junction protein Cx43 is involved in the bone-targeted metastatic behaviour of human prostate cancer cells

For decades, cancer was associated with gap-junction defects. However, more recently it appeared that the gap junction proteins (connexins) could be re-expressed and participate to cancer cell dissemination during the late stages of tumor progression. Since primary tumors of prostate cancer (PCa) are known to be connexin deficient, it was interesting to verify whether their bone-targeted metastatic behaviour could be influenced by the re-expression of the connexin type (connexin43) which is originally present in prostate tissue and highly expressed in bone where it participates to the differentiation of osteoblastic cells. Thus, we investigated the effect of the increased Cx43 expression, by retroviral infection, on the metastatic behaviour of two well-characterized cell lines (PC-3 and LNCaP) representing different stages of PCa progression. It appeared that Cx43 differently behaved in those cell lines and induced different phenotypes. In LNCaP, Cx43 was functional, localized at the plasma membrane and its high expression was correlated with a more aggressive phenotype both in vitro and in vivo. In particular, those Cx43-expressing LNCaP cells exhibited a high incidence of osteolytic metastases generated by bone xenografts in mice. Interestingly, LNCaP cells were also able to decrease the proliferation of cocultured osteoblastic cells. In contrast, the increased expression of Cx43 in PC-3 cells led to an unfunctional, cytoplasmic localization of the protein and was correlated with a reduction of proliferation, adhesion and invasion of the cells. In conclusion, the localization and the functionality of Cx43 may govern the ability of PCa cells to metastasize in bones.

Osteoblasts can stimulate prostate cancer growth and transcriptionally down-regulate PSA expression in cell line models

INTRODUCTION

To investigate the effect of bone environment on cellular proliferation, mature prostate-specific antigen (PSA) production and secretion, and PSA transcriptional regulation of prostate cancer cells.

MATERIALS AND METHODS

Androgen-independent C4-2 prostate cancer cells were co-cultured with various osteoblastic cells in a transwell system. Proliferation was measured via cell counting and MTT assay. Lactate and PSA were determined in the conditioned media (CM). Transcriptional activity of the full-length PSA promoter (6.1 kilobases) and of 3 deletion constructs was determined via luciferase reporter assay upon exposure to CM from various osteoblastic cell lines.

RESULTS

Osteoblastic bone cells and CM, but not control cells (fibroblast) or CM, reproducibly stimulated the proliferation of C4-2 cells. The co-culture system, PSA production by C4-2 cells transiently decreased when in co-culture with osteoblastic, but not with control cells. After abundant prostate cell proliferation, the secreted PSA levels rose exponentially. Addition of CM from osteoblastic cells, but not control cells, consistently decreased (about 3-fold) the transcriptional activity of the PSA promoter in C4-2 cells. Deletion construct analysis of the PSA promoter revealed that the transcriptional down-regulation is dually controlled by elements close to the TATA and upstream androgen responsive (ARE(III)) components.

CONCLUSIONS

The osteoblastic environment stimulates prostate cancer cell proliferation but reduces PSA production initially. The mechanism of PSA down-regulation is transcriptional, most likely in response to soluble factors present in the osteoblastic bone stromal cell CM. Transcriptional down-regulation appears to be mediated by elements near both the TATA box and the ARE(III) component.

Choriocarcinoma cell line Response to Dexamethasone

Choriocarcinoma cell lines JAr and JEG-3 are model systems for the study of transformed trophoblast. Both cell lines were shown to produce galectin-1, expression of which was increased in choriocarcinoma when compared to the normal trophoblast of pregnancy. In this study the effects of synthetic glucocorticoid dexametha-sone were investigated in both JAr and JEG-3 cell lines by the MTT test, cell based ELISA, and the cell adhesion and migration tests. Viable cell number/cell proliferation of JAr cells was significantly increased after treatment with 0.1 and 1 nmol/L of dexamethasone, while proliferation of JEG-3 cells was significantly increased after treatment in the whole concentration range of dexamethasone (0.1-100 nmol/L). Galectin-1 in JAr cells was modulated by dexamethasone, which mildly, but significantly decreased production at low concentrations (0.1 and 1 nmol/L). In JEG-3 cells production of galectin-1 was significantly decreased only after treatment with 100 nmol/L of dexamethasone. Cell adhesion of JEG-3 was significantly increased in the presence of lactose, an inhibitory sugar for gal-1, while dexamethasone induced decrease of JEG-3 cell migration. These findings have shown that dexamet-hasone may affect proliferation, gal-1 production and cell migration, in a cell line specific manner. These data suggest that glucocorticoid treatmentin vivomight have the potential to affect cell functions in choriocarcinoma.

Cross-linking of GM1 ganglioside by galectin-1 mediates regulatory T cell activity involving TRPC5 channel activation: possible role in suppressing experimental autoimmune encephalomyelitis

Several animal autoimmune disorders are suppressed by treatment with the GM1 cross-linking units of certain toxins such as B subunit of cholera toxin (CtxB). Due to the recent observation of GM1 being a binding partner for the endogenous lectin galectin-1 (Gal-1), which is known to ameliorate symptoms in certain animal models of autoimmune disorders, we tested the hypothesis that an operative Gal-1/GM1 interplay induces immunosuppression in a manner evidenced by both in vivo and in vitro systems. Our study of murine experimental autoimmune encephalomyelitis (EAE) indicated suppressive effects by both CtxB and Gal-1 and further highlighted the role of GM1 in demonstrating enhanced susceptibility to EAE in mice lacking this ganglioside. At the in vitro level, polyclonal activation of murine regulatory T (Treg) cells caused up-regulation of Gal-1 that was both cell bound and released to the medium. Similar activation of murine CD4(+) and CD8(+) effector T (Teff) cells resulted in significant elevation of GM1 and GD1a, the neuraminidase-reactive precursor to GM1. Activation of Teff cells also up-regulated TRPC5 channels which mediated Ca(2+) influx upon GM1 cross-linking by Gal-1 or CtxB. This involved co-cross-linking of heterodimeric integrin due to close association of these alpha(4)beta(1) and alpha(5)beta(1) glycoproteins with GM1. Short hairpin RNA (shRNA) knockdown of TRPC5 in Teff cells blocked contact-dependent proliferation inhibition by Treg cells as well as Gal-1/CtxB-triggered Ca(2+) influx. Our results thus indicate GM1 in Teff cells to be the primary target of Gal-1 expressed by Treg cells, the resulting co-cross-linking and TRPC5 channel activation contributing importantly to the mechanism of autoimmune suppression.

Gene expression profile of the bone microenvironment in human fragility fracture bone

Osteoporosis (OP) is a common age-related systemic skeletal disease, with a strong genetic component, characterised by loss of bone mass and strength, which leads to increased bone fragility and susceptibility to fracture. Although some progress has been made in identifying genes that may contribute to OP disease, much of the genetic component of OP has yet to be accounted for. Therefore, to investigate the molecular basis for the changes in bone causally involved in OP and fragility fracture, we have used a microarray approach. We have analysed altered gene expression in human OP fracture bone by comparing mRNA in bone from individuals with fracture of the neck of the proximal femur (OP) with that from age-matched individuals with osteoarthritis (OA), and control (CTL) individuals with no known bone pathology. The OA sample set was included because an inverse association, with respect to bone density, has been reported between OA and the OP individuals. Compugen H19K oligo human microarray slides were used to compare the gene expression profiles of three sets of female samples comprising, 10 OP-CTL, 10 OP-OA, and 10 OA-CTL sample pairs. Using linear models for microarray analysis (Limma), 150 differentially expressed genes in OP bone with t scores >5 were identified. Differential expression of 32 genes in OP bone was confirmed by real time PCR analysis (p<0.01). Many of the genes identified have known or suspected roles in bone metabolism and in some cases have been implicated previously in OP pathogenesis. Three major sets of differentially expressed genes in OP bone were identified with known or suspected roles in either osteoblast maturation (PRRX1, ANXA2, ST14, CTSB, SPARC, FST, LGALS1, SPP1, ADM, and COL4A1), myelomonocytic differentiation and osteoclastogenesis (TREM2, ANXA2, IL10, CD14, CCR1, ADAM9, CCL2, CTGF, and KLF10), or adipogenesis, lipid and/or glucose metabolism (IL10, MARCO, CD14, AEBP1, FST, CCL2, CTGF, SLC14A1, ANGPTL4, ADM, TAZ, PEA15, and DOK4). Altered expression of these genes and others in these groups is consistent with previously suggested underlying molecular mechanisms for OP that include altered osteoblast and osteoclast differentiation and function, and an imbalance between osteoblastogenesis and adipogenesis.

Single nucleotide polymorphisms in bone turnover-related genes in Koreans: ethnic differences in linkage disequilibrium and haplotype

Background

Osteoporosis is defined as the loss of bone mineral density that leads to bone fragility with aging. Population-based case-control studies have identified polymorphisms in many candidate genes that have been associated with bone mass maintenance or osteoporotic fracture. To investigate single nucleotide polymorphisms (SNPs) that are associated with osteoporosis, we examined the genetic variation among Koreans by analyzing 81 genes according to their function in bone formation and resorption during bone remodeling.

Methods

We resequenced all the exons, splice junctions and promoter regions of candidate osteoporosis genes using 24 unrelated Korean individuals. Using the common SNPs from our study and the HapMap database, a statistical analysis of deviation in heterozygosity depicted.

Results

We identified 942 variants, including 888 SNPs, 43 insertion/deletion polymorphisms, and 11 microsatellite markers. Of the SNPs, 557 (63%) had been previously identified and 331 (37%) were newly discovered in the Korean population. When compared SNPs in the Korean population with those in HapMap database, 1% (or less) of SNPs in the Japanese and Chinese subpopulations and 20% of those in Caucasian and African subpopulations were significantly differentiated from the Hardy-Weinberg expectations. In addition, an analysis of the genetic diversity showed that there were no significant differences among Korean, Han Chinese and Japanese populations, but African and Caucasian populations were significantly differentiated in selected genes. Nevertheless, in the detailed analysis of genetic properties, the LD and Haplotype block patterns among the five sub-populations were substantially different from one another.

Conclusion

Through the resequencing of 81 osteoporosis candidate genes, 118 unknown SNPs with a minor allele frequency (MAF) > 0.05 were discovered in the Korean population. In addition, using the common SNPs between our study and HapMap, an analysis of genetic diversity and deviation in heterozygosity was performed and the polymorphisms of the above genes among the five populations were substantially differentiated from one another. Further studies of osteoporosis could utilize the polymorphisms identified in our data since they may have important implications for the selection of highly informative SNPs for future association studies.

O-glycosylation regulates LNCaP prostate cancer cell susceptibility to apoptosis induced by galectin-1

Resistance to apoptosis is a critical feature of neoplastic cells. Galectin-1 is an endogenous carbohydrate-binding protein that induces death of leukemia and lymphoma cells, breast cancer cells, and the LNCaP prostate cancer cell line, but not other prostate cancer cell lines. To understand the mechanism of galectin-1 sensitivity of LNCaP cells compared with other prostate cancer cells, we characterized glycan ligands that are important for conferring galectin-1 sensitivity in these cells, and analyzed expression of glycosyltransferase genes in galectin-1-sensitive, prostate-specific antigen-positive (PSA(+)) LNCaP cells compared with a galectin-1-resistant PSA(-) LNCaP subclone. We identified one glycosyltransferase, core 2 N-acetylglucosaminyltransferase, which is down-regulated in galectin-1-resistant PSA(-) LNCaP cells compared with galectin-1-sensitive PSA(+) LNCaP cells. Intriguingly, this is the same glycosyltransferase required for galectin-1 susceptibility of T lymphoma cells, indicating that similar O-glycan ligands on different polypeptide backbones may be common death trigger receptors recognized by galectin-1 on different types of cancer cells. Blocking O-glycan elongation by expressing alpha2,3-sialyltransferase 1 rendered LNCaP cells resistant to galectin-1, showing that specific O-glycans are critical for galectin-1 susceptibility. Loss of galectin-1 susceptibility and synthesis of endogenous galectin-1 has been proposed to promote tumor evasion of immune attack; we found that galectin-1-expressing prostate cancer cells killed bound T cells, whereas LNCaP cells that do not express galectin-1 did not kill T cells. Resistance to galectin-1-induced apoptosis may directly contribute to the survival of prostate cancer cells as well as promote immune evasion by the tumor.

Proteomic profiling of rat bone marrow mesenchymal stem cells induced by 5-azacytidine

Mesenchymal stem cells (MSCs) can differentiate into different types of cells and thus have tremendous potential for cell therapy and tissue engineering. 5-Azacytidine (5-aza), a DNA demethylation reagent, has been reported to induce MSCs to differentiate into cardiomyocytes in vitro. To determine a global effect of 5-aza on MSCs, we investigated the protein expressions of rat MSCs with two-dimensional gel electrophoresis (2-DE). We have generated a proteome reference map of rat MSCs, and have successfully identified 34 proteins with MALDI-TOF-MS analysis. Nine proteins showed distinct regulation in MSCs after 5-aza treatment. The proteins regulated by 5-aza included cytoskeletal proteins, cadmium-binding proteins, and metabolic proteins, etc. These proteins have been reported to be involved in cell proliferation and differentiation through different signaling pathways, and the molecular mechanism of MSCs differentiation is discussed at the proteome level.

Proteomic analysis of cartilage- and bone-associated samples

The skeleton of the human body is built of cartilage and bone, which are tissues that contain extensive amounts of extracellular matrix (ECM). In bone, inorganic mineral hydroxyapatite forms 50-70% of the whole weight of the tissue. Although the organic matrix of bone consists of numerous proteins, 90% of it is composed of type I collagen. In cartilage, ECM forms a major fraction of the tissue, type II collagen and aggrecans being the most abundant macromolecules. It is obvious that the high content of ECM components causes analytical problems in the proteomic analysis of cartilage and bone, analogous to those in the analysis of low-abundance proteins present in serum. The massive contents of carbohydrates present in cartilage proteoglycans, and hydroxyapatite in bone, further complicate the situation. However, the development of proteomic tools makes them more and more tempting also for research of musculoskeletal tissues. Application of proteomic techniques to the research of chondrocytes, osteoblasts, osteocytes, and osteoclasts in cell cultures can immediately benefit from the present knowledge. Here we make an overview to previous proteomic research of cartilage- and bone-associated samples and evaluate the future prospects of applying proteomic techniques to investigate key events, such as cellular signal transduction, in cartilage- and bone-derived cells.

Galectin-1: a small protein with major functions

Galectins are a family of carbohydrate-binding proteins with an affinity for beta-galactosides. Galectin-1 (Gal-1) is differentially expressed by various normal and pathological tissues and appears to be functionally polyvalent, with a wide range of biological activity. The intracellular and extracellular activity of Gal-1 has been described. Evidence points to Gal-1 and its ligands as one of the master regulators of such immune responses as T-cell homeostasis and survival, T-cell immune disorders, inflammation and allergies as well as host-pathogen interactions. Gal-1 expression or overexpression in tumors and/or the tissue surrounding them must be considered as a sign of the malignant tumor progression that is often related to the long-range dissemination of tumoral cells (metastasis), to their dissemination into the surrounding normal tissue, and to tumor immune-escape. Gal-1 in its oxidized form plays a number of important roles in the regeneration of the central nervous system after injury. The targeted overexpression (or delivery) of Gal-1 should be considered as a method of choice for the treatment of some kinds of inflammation-related diseases, neurodegenerative pathologies and muscular dystrophies. In contrast, the targeted inhibition of Gal-1 expression is what should be developed for therapeutic applications against cancer progression. Gal-1 is thus a promising molecular target for the development of new and original therapeutic tools.

Mass Spectrometrical Analysis of Galectin Proteins in Primary Rat Cerebellar Astrocytes

Galectins are a family of animal lectins with specificity for beta-galactosides and are involved in a host of cellular activities, ranging from development to cancer. The molecules are expressed by neural and non-neural cells intracellularly as well as extracellularly. Using two-dimensional gel electrophoresis coupled to tandem mass spectrometry, the present work aimed to identify and characterize galectins in primary rat cerebellar astrocytes. The protein-chemical method identified nine spots representing two members of the galectin family, namely galectin-1 and galectin-3. These findings suggest that high abundant expression of galectin in astrocytes is limited to the two abundant galectin family members. As these family members are linked to human astrocytic tumors, their reliable detection in astrocytes by proteomic techniques would enable us to further understand their role in neural development, injury, and regeneration in general and astrocytoma in particular.

Biphasic effect of recombinant galectin-1 on the growth and death of early hematopoietic cells

Galectin-1 is a member of the family of beta-galactoside binding animal lectins, galectins. Its presence in the bone marrow has been detected; however, its role in the regulation of hematopoiesis is unknown. In the present study, we have evaluated the effect of recombinant human galectin-1 on the proliferation and survival of murine and human hematopoietic stem and progenitor cells. We show that low amount of galectin-1 (10 ng/ml) increases the formation of granulocyte-macrophage and erythroid colonies and the frequencies of day-7 cobblestone area-forming cells on a lactose-inhibitable fashion. In contrast, high amount of galectin-1 (10 microg/ml) dramatically reduces the growth of the committed blood-forming progenitor cells as well as the much younger, lineage-negative hematopoietic cells (day-28 to -35 cobblestone area-forming cells). This inhibition is not blocked by lactose and, therefore, is largely independent of the beta-galactoside-binding site of the lectin. Furthermore, assays to detect apoptosis render it likely that the high amount of galectin-1 acts as a classical proapoptotic factor for the premature hematopoietic cells.

Application of proteomics in the study of tumor metastasis

Tumor metastasis is the dominant cause of death in cancer patients. However, the molecular and cellular mechanisms underlying tumor metastasis are still elusive. The identification of protein molecules with their expressions correlated to the metastatic process would help to understand the metastatic mechanisms and thus facilitate the development of strategies for the therapeutic interventions and clinical management of cancer. Proteomics is a systematic research approach aiming to provide the global characterization of protein expression and function under given conditions. Proteomic technology has been widely used in biomarker discovery and pathogenetic studies including tumor metastasis. This article provides a brief review of the application of proteomics in identifying molecular factors in tumor metastasis process. The combination of proteomics with other experimental approaches in biochemistry, cell biology, molecular genetics and chemistry, together with the development of new technologies and improvements in existing methodologies will continue to extend its application in studying cancer metastasis.

A combination of protein profiling and isotopomer analysis using matrix-assisted laser desorption/ionization-time of flight mass spectrometry reveals an active metabolism of the extracellular matrix of 3T3-L1 adipocytes

Differential gel electrophoresis followed by matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) mass spectrometry (MS) is a commonly used protein profiling method. However, observed changes can be explained in multiple ways, one of which is by the protein turnover rate. In order to easily and rapidly obtain information on both the identity and turnover of individual proteins, we applied a combination of protein labeling with L-(ring-2,3,4,5,6 2H5) phenylalanine and MALDI-TOF MS. While the spectrum reveals the identity of a protein, mass isotopomer analysis provides information about the rate of protein labeling as a measure of synthesis or turnover. Using this approach on mature 3T3-L1 adipocytes, we were able to discriminate between rapidly and slowly metabolised proteins. In our isolate, proteins of the cytoskeleton appeared to be slowly metabolised, whereas components of the extracellular matrix, in particular collagen type I alpha 1 (COL1A1) and collagen type I alpha 2 (COL1A2) showed rapid accumulation of newly synthesized proteins. Both proteins appeared to be metabolised in the same ratio as they are present in collagen fibers, i.e. 2:1 (COL1A1: COL1A2). In addition, functionally related proteins were also readily labeled. Taken together, we have shown that a combination of stable isotope labeling and protein profiling by gel electrophoresis and MALDI-TOF analysis can simultaneously provide information on the identity and relative metabolic rate of proteins in eukaryotic cells in a simple, nonhazardous and rapid-throughput way.

Galectin-1 supports survival of naive T cells without promoting cell proliferation

Naive T cells do not proliferate but remain alive in vivo. In contrast, naive T cells rapidly die in an in vitro culture, suggesting that some factors that are present at the sites of naive T cell circulation in vivo but missing in the bovine serum-containing culture medium, are necessary for their survival. The present study was designed to search for such factors. By functional screening of the cDNA library from murine lymph node-derived stromal cells (LNS) that effectively support the survival of naive T cells, we found that nascent polypeptide-associated complex (alpha-NAC) promoted T cell survival. A conditioned medium derived from culture supernatant of Cos7 cells transfected with alpha-NAC gene supported T cell survival, indicating that alpha-NAC induced production of soluble factor(s) that were secreted into the medium. By examining the products that were cloned from a functional screening of the cDNA library from alpha-NAC-transfected NIH3T3 cells but were not detected in that from control vector-transfected cells, galectin-1 was found as a soluble factor in the conditioned medium of the LNS. Our study demonstrates the novel role of galectin-1 as a soluble factor that functions to maintain naive T cell survival without inducing cell proliferation.

Influence of IGF-I on adhesion, proliferation, and galectin-1 production in JAr and Jeg-3 choriocarcinoma cell lines

BACKGROUND: JAr and Jeg-3 choriocarcinoma cell lines are model systems for the transformed trophoblast and allow studies of phenotype and regulatory factors for particular cell functions. Both cell lines express the receptor for insulin-like growth factor-I (IGF-I). Effects of IGF-I on adhesion, proliferation and galectin-1 production in JAr and Jeg-3 cells were studied. METHODS: The effects of IGF-I on proliferation and galectin-1 production were examined by thiazolyl blue assay and cell based solid phase assay using polyclonal anti-galectin-1 antibodies. The cell adhesion assay was performed on Matrigel coated wells. Galectin-1 production and localization was examined by immunocytochemistry. RESULTS: IGF-I decreased adhesion of JAr cells to 70% of the control value (p<0.05). Cell treatment with 10 ?g/L of IGF-I significantly increased viable cell number: by 13.5% in JAr and 6% in Jeg-3. Gal-1 was immunolocalized intracellularly and associated with the cell membrane in both cell lines. Production of galectin-1 was significantly increased after treatment with IGF-I compared to control: by 7% in JAr cells and by 16% in Jeg-3 cells (p<0.05). CONCLUSION: The data showed that IGF-I affected adhesion and proliferation of choriocarcinoma cells, depending on the cell line. Both choriocarcinoma cell lines studied here produced galectin-1. The amount of galectin-1 was moderately stimulated by IGF-I.

Galectin-1: a bifunctional regulator of cellular proliferation

Galectin-1 has demonstrated a diverse range of activities in relation to cell survival and proliferation. In different circumstances, it acts as a mitogen, as an inhibitor of cell proliferation, and as a promoter of cellular apoptosis. Many of these activities, particularly the mitogenic and apoptotic responses, follow from the interaction of galectin-1 with cell-surface beta-galactoside ligands, but there is increasing evidence for protein-protein interactions involving galectin-1, and for a beta-galactoside-independent cytostatic mechanism. The bifunctional nature of galectin-1, in conjunction with other experimental variables, makes it difficult to assess the overall outcomes and significance of the growth-regulatory actions in many previous investigations. There is thus a need for well-defined experimental cross-correlation of observations, for which specific loss-of-function galectin-1 mutants will be invaluable. Unsurprisingly, in view of this background, the interpretation of the actions of galectin-1 in developmental situations, both normal and neoplastic, is often very complex.

Modulation of prostate cancer growth in bone microenvironments

Bone remains one of the major sites, and most lethal host organs, for prostate cancer metastasis. Prostate cell spread and establishment in bone depends on multiple reciprocal modifications of bone stromal and epithelial cancer cell behaviors. This review focuses on recent advances in the characterization of cell-cell and cell-matrix interplay, effects on cell growth, adhesion and invasion, and several therapeutic possibilities for co-targeting prostate cancer cells and bone stroma. We address the topic from three main perspectives: (1) the normal and aging bone stromal environment, (2) the "reactive" bone stromal environment, and (3) the cancerous prostate epithelial cells themselves. First, normal, and especially aging, bones provide uniquely rich and "fertile soil" for roaming cancer cells. The interactions between prostate cancer cells and insoluble extracellular matrices, soluble growth factors, and/or sex steroid hormones trigger bone remodeling, through increased osteoclastogenesis and furthur matrix metalloproteinase activity. Second, after cancer cell arrival and establishment in the bone, host stromal cells respond, becoming "reactive" in a process again involving extracellular matrix remodeling, together with growth factor and steroid receptor signaling this process ultimately enhances cancer cell migration, stromal transdifferentiation, and invasion of the cancer tissues by stromal, inflammatory, and immune-responsive cells. Third, prostate cancer cells also respond to supportive bone microenvironments, where soluble and matrix-associated molecules affect cancer cell growth and gene expression, especially altering cancer cell surface receptor and integrin-mediated cell signaling. We discuss both integrin cell-matrix and gap junctional cell-cell communication between cancer cells and their microenvironments during prostate cancer progression.

Galectin-1 interacts with β-1 subunit of integrin

Galectin-1, a beta-galactoside-binding dimeric lectin, is involved in adhesion, migration, and proliferation of vascular smooth muscle cells (SMC), the key steps in the development of atherosclerosis and restenosis. Here we investigated the molecular basis of the interactions between galectin-1 and SMCs. Galectin-1 modulated SMC attachment in a dose- and beta-galactoside-dependent manner. Direct binding of galectin-1 to beta1 integrin was detected by the immune precipitation of beta1 integrin after chemical cross-linking of 125I-labelled galectin-1 to the cell surface proteins. Galectin-1 transiently increased availability of beta1 integrins on the cell surface to antibodies against beta1 integrin. Incubation of SMCs with galectin-1 transiently increased the amount of the active form of beta1 integrin and tyrosine phosphorylation of two cytoskeleton-associated proteins; one of them coincided with focal adhesion kinase (FAK). Galectin-1 is likely to affect SMC adhesion by interacting with beta1 integrin on the cell surface of SMCs and inducing outside-in signalling.