Phospholipases of mineralization competent cells and matrix vesicles: roles in physiological and pathological mineralizations

Lipids and Minerals, Interplay in Biomineralization: Nature's Alchemy

The main focus of this article is the role of lipids in biomineralization. Much of the discussion on biomineralization focuses on proteins in these decades. Indeed, collagen and acidic noncollagenous proteins effectively serve as templates for mineralization. However, other macromolecules such as lipids and polysaccharides have received less attention despite their abundance at mineralization sites. The matrix vesicle (MV) theory is widely accepted as the induction of early mineralization. Although ion concentration within the vesicles has been discussed in the initial mineralization in this theory, the role of phospholipids that constitute the vesicle membrane has not been discussed much. Comprehensive considerations, including pathological mineralization, exist regardless of the localization of MVs, the involvement of bacteria in dental calculus formation, and biomineralization caused by marine organisms such as corals, suggesting that initial mineralization found in these biological conditions might be a common reaction relating to lipids. In contrast, despite the abundance of lipids, mineralization occurs only in the limited tissue within our body. In other words, gathering knowledge and creating a path to understanding about lipid-based mineralization is extremely important in proposing new bone disease treatment methods. This article describes how lipids influence nucleation, mineralization, and expansion during hard tissue formation.

Vascular calcification: from the perspective of crosstalk

Vascular calcification (VC) is highly correlated with cardiovascular disease morbidity and mortality, but anti-VC treatment remains an area to be tackled due to the ill-defined molecular mechanisms. Regardless of the type of VC, it does not depend on a single cell but involves multi-cells/organs to form a complex cellular communication network through the vascular microenvironment to participate in the occurrence and development of VC. Therefore, focusing only on the direct effect of pathological factors on vascular smooth muscle cells (VSMCs) tends to overlook the combined effect of other cells and VSMCs, including VSMCs-VSMCs, ECs-VMSCs, Macrophages-VSMCs, etc. Extracellular vesicles (EVs) are a collective term for tiny vesicles with a membrane structure that are actively secreted by cells, and almost all cells secrete EVs. EVs docked on the surface of receptor cells can directly mediate signal transduction or transfer their contents into the cell to elicit a functional response from the receptor cells. They have been proven to participate in the VC process and have also shown attractive therapeutic prospects. Based on the advantages of EVs and the ability to be detected in body fluids, they may become a novel therapeutic agent, drug delivery vehicle, diagnostic and prognostic biomarker, and potential therapeutic target in the future. This review focuses on the new insight into VC molecular mechanisms from the perspective of crosstalk, summarizes how multi-cells/organs interactions communicate via EVs to regulate VC and the emerging potential of EVs as therapeutic methods in VC. We also summarize preclinical experiments on crosstalk-based and the current state of clinical studies on VC-related measures.

PLCL1 suppresses tumour progression by regulating AMPK/mTOR-mediated autophagy in renal cell carcinoma

Autophagy has been increasingly recognized as a critical regulatory mechanism in the maintenance of cellular homeostasis. A previous study showed that phospholipase C-like protein 1 (PLCL1) is associated with lipid metabolism in renal cell carcinoma (RCC). However, it is unclear whether PLCL1 regulates autophagy, thereby influencing the progression of RCC. Bioinformatics analysis of five microarray datasets revealed that expression of PLCL1 is decreased in tumours and is positively correlated with prognosis in RCC patients. Three independent public datasets, clinical RCC tissues and RCC cell lines, were validated using real-time qPCR, western blotting and immunohistochemistry. Using wound healing and transwell assays, we observed that elevated PLCL1 levels decreased the migratory distance and the invasive number of 786-O and ACHN cells, but PLCL1 knockdown reversed these changes in 769P cell lines compared to those in controls. The results of flow cytometry analysis indicated that PLCL1 promotes apoptosis. Moreover, transcriptional analysis based on stable overexpression of PLCL1 in 786-O cells revealed that PLCL1 is related to autophagy, and western blotting and autophagic experimental results further verified these findings. Mechanistic investigations confirmed that PLCL1 activates the AMPK/mTOR pathway and interacts with decidual protein induced by progesterone (DEPP). Collectively, our data suggest that PLCL1 functions as a suppressor of RCC progression by activating the AMPK/mTOR pathway, interacting with DEPP, initiating autophagy and inducing apoptosis. PLCL1 may be a promising therapeutic target for the diagnosis and treatment of ccRCC patients.

Spatial metabolomics reveals upregulation of several pyrophosphate-producing pathways in cortical bone of Hyp mice

Patients with the renal phosphate-wasting disease X-linked hypophosphatemia (XLH) and Hyp mice, the murine homolog of XLH, are characterized by loss-of-function mutations in phosphate-regulating endopeptidase homolog X-linked (PHEX), leading to excessive secretion of the bone-derived phosphotropic hormone FGF23. The mineralization defect in patients with XLH and Hyp mice is caused by a combination of hypophosphatemia and local accumulation of mineralization-inhibiting molecules in bone. However, the mechanism by which PHEX deficiency regulates bone cell metabolism remains elusive. Here, we used spatial metabolomics by employing matrix-assisted laser desorption/ionization (MALDI) Fourier-transform ion cyclotron resonance mass spectrometry imaging (MSI) of undecalcified bone cryosections to characterize in situ metabolic changes in bones of Hyp mice in a holistic, unbiased manner. We found complex changes in Hyp bone metabolism, including perturbations in pentose phosphate, purine, pyrimidine, and phospholipid metabolism. Importantly, our study identified an upregulation of several biochemical pathways involved in intra- and extracellular production of the mineralization inhibitor pyrophosphate in the bone matrix of Hyp mice. Our data emphasize the utility of MSI-based spatial metabolomics in bone research and provide holistic in situ insights as to how Phex deficiency-induced changes in biochemical pathways in bone cells are linked to impaired bone mineralization.

Antibody-induced pain-like behavior and bone erosion: links to subclinical inflammation, osteoclast activity, and acid-sensing ion channel 3-dependent sensitization

ABSTRACT

Several bone conditions, eg, bone cancer, osteoporosis, and rheumatoid arthritis (RA), are associated with a risk of developing persistent pain. Increased osteoclast activity is often the hallmark of these bony pathologies and not only leads to bone remodeling but is also a source of pronociceptive factors that sensitize the bone-innervating nociceptors. Although historically bone loss in RA has been believed to be a consequence of inflammation, both bone erosion and pain can occur years before the symptom onset. Here, we have addressed the disconnection between inflammation, pain, and bone erosion by using a combination of 2 monoclonal antibodies isolated from B cells of patients with RA. We have found that mice injected with B02/B09 monoclonal antibodies (mAbs) developed a long-lasting mechanical hypersensitivity that was accompanied by bone erosion in the absence of joint edema or synovitis. Intriguingly, we have noted a lack of analgesic effect of naproxen and a moderate elevation of few inflammatory factors in the ankle joints suggesting that B02/B09-induced pain-like behavior does not depend on inflammatory processes. By contrast, we found that inhibiting osteoclast activity and acid-sensing ion channel 3 signaling prevented the development of B02/B09-mediated mechanical hypersensitivity. Moreover, we have identified secretory phospholipase A2 and lysophosphatidylcholine 16:0 as critical components of B02/B09-induced pain-like behavior and shown that treatment with a secretory phospholipase A2 inhibitor reversed B02/B09-induced mechanical hypersensitivity and bone erosion. Taken together, our study suggests a potential link between bone erosion and pain in a state of subclinical inflammation and offers a step forward in understanding the mechanisms of bone pain in diseases such as RA.

Lipid Analysis of Fracture Hematoma With MALDI-MSI: Specific Lipids are Associated to Bone Fracture Healing Over Time

Background: Fracture healing is a complex process, involving cell-cell interactions, various cytokines, and growth factors. Although fracture treatment improved over the last decades, a substantial part of all fractures shows delayed or absent healing. The fracture hematoma (fxh) is known to have a relevant role in this process, while the exact mechanisms by which it influences fracture healing are poorly understood. To improve strategies in fracture treatment, regulatory pathways in fracture healing need to be investigated. Lipids are important molecules in cellular signaling, inflammation, and metabolism, as well as key structural components of the cell. Analysis of the lipid spectrum in fxh may therefore reflect important events during the early healing phase. This study aims to develop a protocol for the determination of lipid signals over time, and the identification of lipids that contribute to these signals, with matrix-assisted laser desorption/ionization mass spectrometry imaging (MALDI-MSI) in fxh in healthy fracture healing.

Methods: Twelve fxh samples (6 porcine; 6 human) were surgically removed, snap frozen, sectioned, washed, and analyzed using MALDI-MSI in positive and negative ion mode at different time points after fracture (porcine: 72 h; human samples: range 1–19 days). A tissue preparation protocol for lipid analysis in fxh has been developed with both porcine and human fxh. Data were analyzed through principal component- and linear discriminant analyses.

Results: A protocol for the preparation of fxh sections was developed and optimized. Although hematoma is a heterogeneous tissue, the intra-variability within fxh was smaller than the inter-variability between fxh. Distinctive m/z values were detected that contributed to the separation of three different fxh age groups: early (1–3 days), middle (6–10 days), and late (12–19 days). Identification of the distinctive m/z values provided a panel of specific lipids that showed a time dependent expression within fxh.

Conclusion: This study shows that MALDI-MSI is a suitable analytical tool for lipid analysis in fxh and that lipid patterns within fxh are time-dependent. These lipid patterns within fxh may serve as a future diagnostic tool. These findings warrant further research into fxh analysis using MALDI-MSI and its possible clinical implications in fracture treatment.

Matrix vesicles from dental follicle cells improve alveolar bone regeneration via activation of the PLC/PKC/MAPK pathway

Background

The regeneration of bone loss that occurs after periodontal diseases is a significant challenge in clinical dentistry. Extracellular vesicles (EVs)-based cell-free regenerative therapies represent a promising alternative for traditional treatments. Developmental biology suggests matrix vesicles (MVs), a subtype of EVs, contain mineralizing-related biomolecules and play an important role in osteogenesis. Thus, we explore the therapeutic benefits and expect to find an optimized strategy for MV application.

Methods

Healthy human dental follicle cells (DFCs) were cultured with the osteogenic medium to generate MVs. Media MVs (MMVs) were isolated from culture supernatant, and collagenase-released MVs (CRMVs) were acquired from collagenase-digested cell suspension. We compared the biological features of the two MVs and investigated their induction of cell proliferation, migration, mineralization, and the modulation of osteogenic genes expression. Furthermore, we investigated the long-term regenerative capacity of MMVs and CRMVs in an alveolar bone defect rat model.

Results

We found that both DFC-derived MMVs and CRMVs effectively improved the proliferation, migration, and osteogenic differentiation of DFCs. Notably, CRMVs showed better bone regeneration capabilities. Compared to MMVs, CRMVs-induced DFCs exhibited increased synthesis of osteogenic marker proteins including ALP, OCN, OPN, and MMP-2. In the treatment of murine alveolar bone defects, CRMV-loaded collagen scaffold brought more significant therapeutic outcomes with less unhealing areas and more mature bone tissues in comparison with MMVs and acquired the effects resembling DFCs-based treatment. Furthermore, the western blotting results demonstrated the activation of the PLC/PKC/MAPK pathway in CRMVs-induced DFCs, while this cascade was inhibited by MMVs.

Conclusions

In summary, our findings revealed a novel cell-free regenerative therapy for repairing alveolar bone defects by specific MV subtypes and suggest that PLC/PKC/MAPK pathways contribute to MVs-mediated alveolar bone regeneration.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-02721-6.

Cancer extracellular vesicles, tumoroid models, and tumor microenvironment

Cancer extracellular vesicles (EVs), or exosomes, promote tumor progression through enhancing tumor growth, initiating epithelial-to-mesenchymal transition, remodeling the tumor microenvironment, and preparing metastatic niches. Three-dimensionally (3D) cultured tumoroids / spheroids aim to reproduce some aspects of tumor behavior in vitro and show increased cancer stem cell properties. These properties are transferred to their EVs that promote tumor growth. Moreover, recent tumoroid models can be furnished with aspects of the tumor microenvironment, such as vasculature, hypoxia, and extracellular matrix. This review summarizes tumor tissue culture and engineering platforms compatible with EV research. For example, the combination experiments of 3D-tumoroids and EVs have revealed multifunctional proteins loaded in EVs, such as metalloproteinases and heat shock proteins. EVs or exosomes are able to transfer their cargo molecules to recipient cells, whose fates are often largely altered. In addition, the review summarizes approaches to EV labeling technology using fluorescence and luciferase, useful for studies on EV-mediated intercellular communication, biodistribution, and metastatic niche formation.

Gut microbiota is associated with bone mineral density : an observational and genome-wide environmental interaction analysis in the UK Biobank cohort

AIMS

Despite the interest in the association of gut microbiota with bone health, limited population-based studies of gut microbiota and bone mineral density (BMD) have been made. Our aim is to explore the possible association between gut microbiota and BMD.

METHODS

A total of 3,321 independent loci of gut microbiota were used to calculate the individual polygenic risk score (PRS) for 114 gut microbiota-related traits. The individual genotype data were obtained from UK Biobank cohort. Linear regressions were then conducted to evaluate the possible association of gut microbiota with L1-L4 BMD (n = 4,070), total BMD (n = 4,056), and femur total BMD (n = 4,054), respectively. PLINK 2.0 was used to detect the single-nucleotide polymorphism (SNP) × gut microbiota interaction effect on the risks of L1-L4 BMD, total BMD, and femur total BMD, respectively.

RESULTS

We detected five, three, and seven candidate gut microbiota-related traits for L1-L4 BMD, total BMD, and femur BMD, respectively, such as genus Dialister (p = 0.004) for L1-L4 BMD, and genus Eisenbergiella (p = 0.046) for total BMD. We also detected two common gut microbiota-related traits shared by L1-L4 BMD, total BMD, and femur total BMD, including genus Escherichia Shigella and genus Lactococcus. Interaction analysis of BMD detected several genes that interacted with gut microbiota, such as phospholipase D1 (PLD1) and endomucin (EMCN) interacting with genus Dialister in total BMD, and COL12A1 and Discs Large MAGUK Scaffold Protein 2 (DLG2) interacting with genus Lactococcus in femur BMD.

CONCLUSION

Our results suggest associations between gut microbiota and BMD, which will be helpful to further explore the regulation mechanism and intervention gut microbiota of BMD. Cite this article: Bone Joint Res 2021;10(11):734-741.

Exosome-Based Molecular Transfer Activity of Macrophage-Like Cells Involves Viability of Oral Carcinoma Cells: Size Exclusion Chromatography and Concentration Filter Method

Extracellular vesicles (EV) heterogeneity is a crucial issue in biology and medicine. In addition, tumor-associated macrophages are key components in cancer microenvironment and immunology. We developed a combination method of size exclusion chromatography and concentration filters (SEC-CF) and aimed to characterize different EV types by their size, cargo types, and functions. A human monocytic leukemia cell line THP-1 was differentiated to CD14-positive macrophage-like cells by stimulation with PMA (phorbol 12-myristate 13-acetate) but not M1 or M2 types. Using the SEC-CF method, the following five EV types were fractionated from the culture supernatant of macrophage-like cells: (i) rare large EVs (500–3000 nm) reminiscent of apoptosomes, (ii) EVs (100–500 nm) reminiscent of microvesicles (or microparticles), (iii) EVs (80–300 nm) containing CD9-positive large exosomes (EXO-L), (iv) EVs (20–200 nm) containing unidentified vesicles/particles, and (v) EVs (10–70 nm) containing CD63/HSP90-positive small exosomes (EXO-S) and particles. For a molecular transfer assay, we developed a THP-1-based stable cell line producing a GFP-fused palmitoylation signal (palmGFP) associated with the membrane. The THP1/palmGFP cells were differentiated into macrophages producing palmGFP-contained EVs. The macrophage/palmGFP-secreted EXO-S and EXO-L efficiently transferred the palmGFP to receiver human oral carcinoma cells (HSC-3/palmTomato), as compared to other EV types. In addition, the macrophage-secreted EXO-S and EXO-L significantly reduced the cell viability (ATP content) in oral carcinoma cells. Taken together, the SEC-CF method is useful for the purification of large and small exosomes with higher molecular transfer activities, enabling efficient molecular delivery to target cells.

Untargeted metabolomics revealed therapeutic mechanisms of icariin on low bone mineral density in older caged laying hens

Osteoporosis is a common chronic disease in the elderly population and in some domestic animals. Caged layer osteoporosis (CLO) is a common bone metabolism disease that was recently recommended as an ideal animal model for osteoporosis. This study aimed to investigate the therapeutic effect and mechanism of dietary icariin (ICA), the main bioactive component of the Chinese herb Epimedium, on low bone mineral density (BMD) in older caged laying hens. A total of 216, 54-week-old Lohmann pink-shell laying hens were allocated to three groups, comprising one control group and two treatment groups that were additionally supplied with 0.5 or 2.0 g kg-1 ICA. The results showed that dietary ICA significantly increased the femur BMD by 49.3% and the tibia BMD by 38.9%, improved the microstructure of bone tissue, decreased levels of the bone metabolism index, enhanced serum antioxidant capacity and regulated messenger RNA expression of bone-related genes. ICA-induced differential metabolites were clarified by using untargeted metabolomics assays. Furthermore, correlation analysis between differential metabolites and BMD indicated that eight differential metabolites correlated highly with both femur and tibia BMD, including uridine, taurine, palmitic acid, adrenic acid, fexofenadine, lysoPC(18 : 1), lysoPE(20 : 3/0 : 0) and 3-acetyl-11-keto-beta-boswellic acid. ICA mainly perturbed pyrimidine metabolism, taurine metabolism and lipid metabolism, which led to increased BMD in older caged laying hens. These findings revealed underlying therapeutic mechanisms of dietary ICA on low BMD, and provided reference metabolites for the early diagnosis of osteoporosis.

From organic and inorganic phosphates to valvular and vascular calcifications

Calcification of the arterial wall and valves is an important part of the pathophysiological process of peripheral and coronary atherosclerosis, aortic stenosis, ageing, diabetes, and chronic kidney disease. This review aims to better understand how extracellular phosphates and their ability to be retained as calcium phosphates on the extracellular matrix initiate the mineralization process of arteries and valves. In this context, the physiological process of bone mineralization remains a human model for pathological soft tissue mineralization. Soluble (ionized) calcium precipitation occurs on extracellular phosphates; either with inorganic or on exposed organic phosphates. Organic phosphates are classified as either structural (phospholipids, nucleic acids) or energetic (corresponding to phosphoryl transfer activities). Extracellular phosphates promote a phenotypic shift in vascular smooth muscle and valvular interstitial cells towards an osteoblast gene expression pattern, which provokes the active phase of mineralization. A line of defense systems protects arterial and valvular tissue calcifications. Given the major roles of phosphate in soft tissue calcification, phosphate mimetics, and/or prevention of phosphate dissipation represent novel potential therapeutic approaches for arterial and valvular calcification.

Ablation of Enpp6 Results in Transient Bone Hypomineralization

Biomineralization is a fundamental process key to the development of the skeleton. The phosphatase orphan phosphatase 1 (PHOSPHO1), which likely functions within extracellular matrix vesicles, has emerged as a critical regulator of biomineralization. However, the biochemical pathways that generate intravesicular PHOSPHO1 substrates are currently unknown. We hypothesized that the enzyme ectonucleotide pyrophosphatase/phosphodiesterase 6 (ENPP6) is an upstream source of the PHOSPHO1 substrate. To test this, we characterized skeletal phenotypes of mice homozygous for a targeted deletion of Enpp6 (Enpp6 ^-/- ). Micro-computed tomography of the trabecular compartment revealed transient hypomineralization in Enpp6 ^-/- tibias (p < 0.05) that normalized by 12 weeks of age. Whole-bone cortical analysis also revealed significantly hypomineralized proximal bone in 4- but not 12-week-old Enpp6 ^-/- mice (p < 0.05) compared with WT animals. Back-scattered SEM revealed a failure in 4-week-old trabecular bone of mineralization foci to propagate. Static histomorphometry revealed increased osteoid volume (p > 0.01) and osteoid surface (p < 0.05), which recovered by 12 weeks but was not accompanied by changes in osteoblast or osteoclast number. This study is the first to characterize the skeletal phenotype of Enpp6 ^-/- mice, revealing transient hypomineralization in young animals compared with WT controls. These data suggest that ENPP6 is important for bone mineralization and may function upstream of PHOSPHO1 as a novel means of generating its substrates inside matrix vesicles. © 2020 The Authors. JBMR Plus published by Wiley Periodicals LLC. on behalf of American Society for Bone and Mineral Research.

Phylogeny and chemistry of biological mineral transport

Three physiologically mineralizing tissues - teeth, cartilage and bone - have critical common elements and important evolutionary relationships. Phylogenetically the most ancient densely mineralized tissue is teeth. In jawless fishes without skeletons, tooth formation included epithelial transport of phosphates, a process echoed later in bone physiology. Cartilage and mineralized cartilage are skeletal elements separate from bone, but with metabolic features common to bone. Cartilage mineralization is coordinated with high expression of tissue nonspecific alkaline phosphatase and PHOSPHO1 to harvest available phosphate esters and support mineralization of collagen secreted locally. Mineralization in true bone results from stochastic nucleation of hydroxyapatite crystals within the cross-linked collagen fibrils. Mineral accumulation in dense collagen is, at least in major part, mediated by amorphous aggregates - often called Posner clusters - of calcium and phosphate that are small enough to diffuse into collagen fibrils. Mineral accumulation in membrane vesicles is widely suggested, but does not correlate with a definitive stage of mineralization. Conversely mineral deposition at non-physiologic sites where calcium and phosphate are adequate has been shown to be regulated in large part by pyrophosphate. All of these elements are present in vertebrate bone metabolism. A key biological element of bone formation is an epithelial-like cellular organization which allows control of phosphate, calcium and pH during mineralization.

Association of Phosphatidylinositol-Specific Phospholipase C with Calcium-Induced Biomineralization in the Coccolithophore Emiliania huxleyi

Biomineralization by calcifying microalgae is a precisely controlled intracellular calcification process that produces delicate calcite scales (or coccoliths) in the coccolithophore Emiliania huxleyi (Haptophycea). Despite its importance in biogeochemical cycles and the marine environment globally, the underlying molecular mechanism of intracellular coccolith formation, which requires calcium, bicarbonate, and coccolith-polysaccharides, remains unclear. In E. huxleyi CCMP 371, we demonstrated that reducing the calcium concentration from 10 (ambient seawater) to 0.1 mM strongly restricted coccolith production, which was then recovered by adding 10 mM calcium, irrespective of inorganic phosphate conditions, indicating that coccolith production could be finely controlled by the calcium supply. Using this strain, we investigated the expression of differentially expressed genes (DEGs) to observe the cellular events induced by changes in calcium concentrations. Intriguingly, DEG analysis revealed that the phosphatidylinositol-specific phospholipase C (PI-PLC) gene was upregulated and coccolith production by cells was blocked by the PI-PLC inhibitor U73122 under conditions closely associated with calcium-induced calcification. These findings imply that PI-PLC plays an important role in the biomineralization process of the coccolithophore E. huxleyi.

Phosphatidylserine controls calcium phosphate nucleation and growth on lipid monolayers: A physicochemical understanding of matrix vesicle-driven biomineralization

Bone biomineralization is an exquisite process by which a hierarchically organized mineral matrix is formed. Growing evidence has uncovered the involvement of one class of extracellular vesicles, named matrix vesicles (MVs), in the formation and delivery of the first mineral nuclei to direct collagen mineralization. MVs are released by mineralization-competent cells equipped with a specific biochemical machinery to initiate mineral formation. However, little is known about the mechanisms by which MVs can trigger this process. Here, we present a combination of in situ investigations and ex vivo analysis of MVs extracted from growing-femurs of chicken embryos to investigate the role played by phosphatidylserine (PS) in the formation of mineral nuclei. By using self-assembled Langmuir monolayers, we reconstructed the nucleation core - a PS-enriched motif thought to trigger mineral formation in the lumen of MVs. In situ infrared spectroscopy of Langmuir monolayers and ex situ analysis by transmission electron microscopy evidenced that mineralization was achieved in supersaturated solutions only when PS was present. PS nucleated amorphous calcium phosphate that converted into biomimetic apatite. By using monolayers containing lipids extracted from native MVs, mineral formation was also evidenced in a manner that resembles the artificial PS-enriched monolayers. PS-enrichment in lipid monolayers creates nanodomains for local increase of supersaturation, leading to the nucleation of ACP at the interface through a multistep process. We posited that PS-mediated nucleation could be a predominant mechanism to produce the very first mineral nuclei during MV-driven bone/cartilage biomineralization.

Increased phospholipase D activity contributes to tumorigenesis in prostate cancer cell models

Prostate cancer (PCa) is the most frequent cancer among men and the first cause of death over 65. Approximately 90% of patients with advanced disease will develop bone metastasis, which dramatically reduces long-term survival. Therefore, effective therapies need to be developed, especially when disease is still well-localized. Phospholipase D (PLD), an enzyme that hydrolyzes phosphatidylcholine to yield phosphatidic acid, regulates several cellular functions as proliferation, survival, migration or vesicular trafficking. PLD is implicated in numerous diseases such as neurodegenerative, cardiovascular, autoimmune disorders or cancer. Indeed, PLD controls different aspects of oncogenesis including tumor progression and resistance to targeted therapies such as radiotherapy. PLD1 and PLD2 are the only isoforms with catalytic activity involved in cancer. Surprisingly, studies deciphering the role of PLD in the pathophysiology of PCa are scarce. Here we describe the correlation between PLD activity and PLD1 and PLD2 expression in PCa bone metastasis-derived cell lines C4-2B and PC-3. Next, by using PLD pharmacological inhibitors and RNA interference strategy, we validate the implication of PLD1 and PLD2 in cell viability, clonogenicity and proliferation of C4-2B and PC-3 cells and in migration capacity of PC-3 cells. Last, we show an increase in PLD activity as well as PLD2 protein expression during controlled starvation of PC-3 cells, concomitant with an augmentation of its migration capacity. Specifically, upregulation of PLD activity appears to be PKC-independent. Taken together, our results indicate that PLD, and in particular PLD2, could be considered as a potential therapeutic target for the treatment of PCa-derived bone metastasis.

Knockout of MMP3 Weakens Solid Tumor Organoids and Cancer Extracellular Vesicles

The tumor organoid (tumoroid) model in three-dimensional (3D) culture systems has been developed to reflect more closely the in vivo tumors than 2D-cultured tumor cells. Notably, extracellular vesicles (EVs) are efficiently collectible from the culture supernatant of gel-free tumoroids. Matrix metalloproteinase (MMP) 3 is a multi-functional factor playing crucial roles in tumor progression. However, roles of MMP3 within tumor growth and EVs have not unveiled. Here, we investigated the protumorigenic roles of MMP3 on integrities of tumoroids and EVs. We generated MMP3-knockout (KO) cells using the CRISPR/Cas9 system from rapidly metastatic LuM1 tumor cells. Moreover, we established fluorescent cell lines with palmitoylation signal-fused fluorescent proteins (tdTomato and enhanced GFP). Then we confirmed the exchange of EVs between cellular populations and tumoroids. LuM1-tumoroids released large EVs (200-1000 nm) and small EVs (50-200 nm) while the knockout of MMP3 resulted in the additional release of broken EVs from tumoroids. The loss of MMP3 led to a significant reduction in tumoroid size and the development of the necrotic area within tumoroids. MMP3 and CD9 (a category-1 EV marker tetraspanin protein) were significantly down-regulated in MMP3-KO cells and their EV fraction. Moreover, CD63, another member of the tetraspanin family, was significantly reduced only in the EVs fractions of the MMP3-KO cells compared to their counterpart. These weakened phenotypes of MMP3-KO were markedly rescued by the addition of MMP3-rich EVs or conditioned medium (CM) collected from LuM1-tumoroids, which caused a dramatic rise in the expression of MMP3, CD9, and Ki-67 (a marker of proliferating cells) in the MMP3-null/CD9-low tumoroids. Notably, MMP3 enriched in tumoroids-derived EVs and CM deeply penetrated recipient MMP3-KO tumoroids, resulting in a remarkable enlargement of solid tumoroids, while MMP3-null EVs did not. These data demonstrate that EVs can mediate molecular transfer of MMP3, resulting in increasing the proliferation and tumorigenesis, indicating crucial roles of MMP3 in tumor progression.

Model of Pathological Collagen Mineralization Based on Spine Ligament Calcification

The aim of the study was to determine the time of mineral growth in human spine ligaments using a mathematical model. The study was based on our previous research in which the physicochemical analysis and computed microtomography measurements of deposits in ligamenta flava were performed. Hydroxyapatite-like mineral (HAP) constituted the mineral phase in ligament samples, in two samples calcium pyrophosphate dehydrate (CPPD) was confirmed. The micro-damage of collagen fibrils in the soft tissue is the crystallization center. The growth of the mineral nucleus is a result of the calcium ions deposition on the nucleus surface. Considering the calcium ions, the main component of HAP, it is possible to describe the grain growth using a diffusion model. The model calculations showed that the growth time of CPPD grains was ca. a month to 6 years, and for HAP grains >4 years for the young and >5.5 years for the elderly patients. The growth time of minerals with a radius >400 μm was relatively short and impossible to identify by medical imaging techniques. The change of growth rate was the largest for HAP deposits. The mineral growth time can provide valuable information for understanding the calcification mechanism, may be helpful in future experiments, as well as useful in estimating the time of calcification appearance.

Cell Stress Induced Stressome Release Including Damaged Membrane Vesicles and Extracellular HSP90 by Prostate Cancer Cells

Tumor cells exhibit therapeutic stress resistance-associated secretory phenotype involving extracellular vesicles (EVs) such as oncosomes and heat shock proteins (HSPs). Such a secretory phenotype occurs in response to cell stress and cancer therapeutics. HSPs are stress-responsive molecular chaperones promoting proper protein folding, while also being released from cells with EVs as well as a soluble form known as alarmins. We have here investigated the secretory phenotype of castration-resistant prostate cancer (CRPC) cells using proteome analysis. We have also examined the roles of the key co-chaperone CDC37 in the release of EV proteins including CD9 and epithelial-to-mesenchymal transition (EMT), a key event in tumor progression. EVs derived from CRPC cells promoted EMT in normal prostate epithelial cells. Some HSP family members and their potential receptor CD91/LRP1 were enriched at high levels in CRPC cell-derived EVs among over 700 other protein types found by mass spectrometry. The small EVs (30-200 nm in size) were released even in a non-heated condition from the prostate cancer cells, whereas the EMT-coupled release of EVs (200-500 nm) and damaged membrane vesicles with associated HSP90α was increased after heat shock stress (HSS). GAPDH and lactate dehydrogenase, a marker of membrane leakage/damage, were also found in conditioned media upon HSS. During this stress response, the intracellular chaperone CDC37 was transcriptionally induced by heat shock factor 1 (HSF1), which activated the CDC37 core promoter, containing an interspecies conserved heat shock element. In contrast, knockdown of CDC37 decreased EMT-coupled release of CD9-containing vesicles. Triple siRNA targeting CDC37, HSP90α, and HSP90β was required for efficient reduction of this chaperone trio and to reduce tumorigenicity of the CRPC cells in vivo. Taken together, we define "stressome" as cellular stress-induced all secretion products, including EVs (200-500 nm), membrane-damaged vesicles and remnants, and extracellular HSP90 and GAPDH. Our data also indicated that CDC37 is crucial for the release of vesicular proteins and tumor progression in prostate cancer.

A Novel Model of Cancer Drug Resistance: Oncosomal Release of Cytotoxic and Antibody-Based Drugs

Extracellular vesicles (EVs), such as exosomes or oncosomes, often carry oncogenic molecules derived from tumor cells. In addition, accumulating evidence indicates that tumor cells can eject anti-cancer drugs such as chemotherapeutics and targeted drugs within EVs, a novel mechanism of drug resistance. The EV-releasing drug resistance phenotype is often coupled with cellular dedifferentiation and transformation in cells undergoing epithelial-mesenchymal transition (EMT), and the adoption of a cancer stem cell phenotype. The release of EVs is also involved in immunosuppression. Herein, we address different aspects by which EVs modulate the tumor microenvironment to become resistant to anticancer and antibody-based drugs, as well as the concept of the resistance-associated secretory phenotype (RASP).

How To Build a Bone: PHOSPHO1, Biomineralization, and Beyond

Since its characterization two decades ago, the phosphatase PHOSPHO1 has been the subject of an increasing focus of research. This work has elucidated PHOSPHO1's central role in the biomineralization of bone and other hard tissues, but has also implicated the enzyme in other biological processes in health and disease. During mineralization PHOSPHO1 liberates inorganic phosphate (P_i) to be incorporated into the mineral phase through hydrolysis of its substrates phosphocholine (PCho) and phosphoethanolamine (PEA). Localization of PHOSPHO1 within matrix vesicles allows accumulation of P_i within a protected environment where mineral crystals may nucleate and subsequently invade the organic collagenous scaffold. Here, we examine the evidence for this process, first discussing the discovery and characterization of PHOSPHO1, before considering experimental evidence for its canonical role in matrix vesicle–mediated biomineralization. We also contemplate roles for PHOSPHO1 in disorders of dysregulated mineralization such as vascular calcification, along with emerging evidence of its activity in other systems including choline synthesis and homeostasis, and energy metabolism. © 2019 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.

Mechanism of Bone Mineralization

Mineralized "hard" tissues of the skeleton possess unique biomechanical properties to support the body weight and movement and act as a source of essential minerals required for critical body functions. For a long time, extracellular matrix (ECM) mineralization in the vertebrate skeleton was considered as a passive process. However, the explosion of genetic studies during the past decades has established that this process is essentially controlled by multiple genetic pathways. These pathways regulate the homeostasis of ionic calcium and inorganic phosphate-two mineral components required for bone mineral formation, the synthesis of mineral scaffolding ECM, and the maintainence of the levels of the inhibitory organic and inorganic molecules controlling the process of mineral crystal formation and its growth. More recently, intracellular enzyme regulators of skeletal tissue mineralization have been identified. The current review will discuss the key determinants of ECM mineralization in bone and propose a unified model explaining this process.

Phospholipase D: A new mediator during high phosphate-induced vascular calcification associated with chronic kidney disease

Vascular calcification (VC) is the pathological accumulation of calcium phosphate crystals in one of the layers of blood vessels, leading to loss of elasticity and causing severe calcification in vessels. Medial calcification is mostly seen in patients with chronic kidney disease (CKD) and diabetes. Identification of key enzymes and their actions during calcification will contribute to understand the onset of pathological calcification. Phospholipase D (PLD1, PLD2) is active at the earlier steps of mineralization in osteoblasts and chondrocytes. In this study, we aimed to determine their effects during high-phosphate treatment in mouse vascular smooth muscle cell line MOVAS, in the ex vivo model of the rat aorta, and in the in vivo model of adenine-induced CKD. We observed an early increase in PLD1 gene and protein expression along with the increase in the PLD activity in vascular muscle cell line, during calcification induced by ascorbic acid and β-glycerophosphate. Inhibition of PLD1 by the selective inhibitor VU0155069, or the pan-PLD inhibitor, halopemide, prevented calcification. The mechanism of PLD activation is likely to be protein kinase C (PKC)-independent since bisindolylmaleimide X hydrochloride, a pan-PKC inhibitor, did not affect the PLD activity. In agreement, we found an increase in Pld1 gene expression and PLD activity in aortic explant cultures treated with high phosphate, whereas PLD inhibition by halopemide decreased calcification. Finally, an increase in both Pld1 and Pld2 expression occurred simultaneously with the appearance of VC in a rat model of CKD. Thus, PLD, especially PLD1, promotes VC in the context of CKD and could be an important target for preventing onset or progression of VC.

PLA2 and ENPP6 may act in concert to generate phosphocholine from the matrix vesicle membrane during skeletal mineralization

Mineralization is a key process in the formation of bone and cartilage in vertebrates, involving the deposition of calcium- and phosphate-containing hydroxyapatite (HA) mineral within a collagenous matrix. Inorganic phosphate (P_i) accumulation within matrix vesicles (MVs) is a fundamental stage in the precipitation of HA, with PHOSPHO1 being identified as the principal enzyme acting to produce P_i PHOSPHO1 is a dual-specific phosphocholine/phosphoethanolamine phosphatase enriched in mineralizing cells and within MVs. However, the source and mechanism by which PHOSPHO1 substrates are formed before mineralization have not been determined. Here, we propose that 2 enzymes-phospholipase A2 (PLA₂) and ectonucleotide pyrophophatase/phosphodiesterase 6 (ENPP6)-act in sequence upon phosphatidylcholine found in MV membranes to produce phosphocholine, which PHOSPHO1 can hydrolyze to liberate P_i This hypothesis is supported by evidence that both enzymes are expressed in mineralizing cells and data showing that phosphatidylcholine is broken down in MVs during mineralization. Therefore, PLA₂ and ENPP6 activities may represent a key step in the mineralization process. Further functional studies are urgently required to examine their specific roles in the initiation of skeletal mineralization.-Stewart, A. J., Leong, D. T. K., Farquharson, C. PLA₂ and ENPP6 may act in concert to generate phosphocholine from the matrix vesicle membrane during skeletal mineralization.

Vibrational spectroscopic techniques to assess bone quality

Although musculoskeletal diseases such as osteoporosis are diagnosed and treatment outcome is evaluated based mainly on routine clinical outcomes of bone mineral density (BMD) by DXA and biochemical markers, it is recognized that these two indicators, as valuable as they have proven to be in the everyday clinical practice, do not fully account for manifested bone strength. Thus, the term bone quality was introduced, to complement considerations based on bone turnover rates and BMD. Bone quality is an "umbrella" term that incorporates the structural and material/compositional characteristics of bone tissue. Vibrational spectroscopic techniques such as Fourier transform infrared microspectroscopy (FTIRM) and imaging (FTIRI), and Raman spectroscopy, are suitable analytical tools for the determination of bone quality as they provide simultaneous, quantitative, and qualitative information on all main bone tissue components (mineral, organic matrix, tissue water), in a spatially resolved manner. Moreover, the results of such analyses may be readily combined with the outcomes of other techniques such as histology/histomorphometry, small angle X-ray scattering, quantitative backscattered electron imaging, and nanoindentation.

Ultrastructural changes during osteogenic differentiation in mesenchymal stromal cells cultured in alginate hydrogel

Background

Osteogenic differentiation of mesenchymal stem cells has been extensively investigated with regards to different aspects, including the analysis of cell intracellular and extracellular proteome, cell gene expression pattern, and morphology. During the osteogenic differentiation, osteoblasts produce and release specific proteins, like osteocalcin and osteopontin. Simultaneously, cells produce the extracellular matrix (ECM) that resembles the bone ECM, with high quantity of calcium and phosphorus. We focused on the ultrastructural changes occurring during the osteogenic differentiation of MSC cultured in alginate hydrogel.

Results

The analysis revealed that during the osteogenic differentiation the most of cells become dead, and these dead cells contain large quantities of calcium and deposition is strictly connected with the cellular death and small membrane vesicles released by cells. Cell organelles were not present within differentiated cells, while in cells from non-osteogenic group the cellular ultrastructure was proper, with single nuclei, endoplasmic reticulum and numerous mitochondria.

Conclusion

The ECM synthesis and deposition during the osteogenic differentiation of MSC involves cellular programmed death. The small membrane vesicles become the mineralization sites of formed bone ECM.

Electronic supplementary material

The online version of this article (doi:10.1186/s13578-016-0128-0) contains supplementary material, which is available to authorized users.

The Expression of PHOSPHO1, nSMase2 and TNAP is Coordinately Regulated by Continuous PTH Exposure in Mineralising Osteoblast Cultures

Sustained exposure to high levels of parathyroid hormone (PTH), as observed in hyperparathyroidism, is catabolic to bone. The increase in the RANKL/OPG ratio in response to continuous PTH, resulting in increased osteoclastogenesis, is well established. However, the effects of prolonged PTH exposure on key regulators of skeletal mineralisation have yet to be investigated. This study sought to examine the temporal expression of PHOSPHO1, TNAP and nSMase2 in mineralising osteoblast-like cell cultures and to investigate the effects of continuous PTH exposure on the expression of these enzymes in vitro. PHOSPHO1, nSMase2 and TNAP expression in cultured MC3T3-C14 cells significantly increased from day 0 to day 10. PTH induced a rapid downregulation of Phospho1 and Smpd3 gene expression in MC3T3-C14 cells and cultured hemi-calvariae. Alpl was differentially regulated by PTH, displaying upregulation in cultured MC3T3-C14 cells and downregulation in hemi-calvariae. PTH was also able to abolish the stimulatory effects of bone morphogenic protein 2 (BMP-2) on Smpd3 and Phospho1 expression. The effects of PTH on Phospho1 expression were mimicked with the cAMP agonist forskolin and blocked by the PKA inhibitor PKI (5-24), highlighting a role for the cAMP/PKA pathway in this regulation. The potent down-regulation of Phospho1 and Smpd3 in osteoblasts in response to continuous PTH may provide a novel explanation for the catabolic effects on the skeleton of such an exposure. Furthermore, our findings support the hypothesis that PHOSPHO1, nSMase2 and TNAP function cooperatively in the initiation of skeletal mineralisation.

Pathophysiology of hypophosphatasia and the potential role of asfotase alfa

Hypophosphatasia (HPP) is an inherited systemic bone disease that is characterized by bone hypomineralization. HPP is classified into six forms according to the age of onset and severity as perinatal (lethal), perinatal benign, infantile, childhood, adult, and odontohypophosphatasia. The causative gene of the disease is the ALPL gene that encodes tissue-nonspecific alkaline phosphatase (TNAP). TNAP is expressed ubiquitously, and its physiological role is apparent in bone mineralization. A defect in bone mineralization can manifest in several ways, including rickets or osteomalacia in HPP patients. Patients with severe forms suffer from respiratory failure because of hypoplastic chest, which is the main cause of death. They sometimes present with seizures due to a defect in vitamin B₆ metabolism resulting from the lack of alkaline phosphatase activity in neuronal cells, which is also lethal. Patients with a mild form of the disease exhibit rickets or osteomalacia and a functional defect of exercise. Odontohypophosphatasia shows only dental manifestations. To date, 302 mutations in the ALPL gene have been reported, mainly single-nucleotide substitutions, and the relationships between phenotype and genotype have been partially elucidated. An established treatment for HPP was not available until the recent development of enzyme replacement therapy. The first successful enzyme replacement therapy in model mice using a modified human TNAP protein (asfotase alfa) was reported in 2008, and subsequently success in patients with severe form of the disease was reported in 2012. In 2015, asfotase alfa was approved in Japan in July, followed by in the EU and Canada in August, and then by the US Food and Drug Administration in the USA in October. It is expected that therapy with asfotase alfa will drastically change treatments and prognosis of HPP.

Zooming in on the genesis of atherosclerotic plaque microcalcifications

Epidemiological evidence conclusively demonstrates that calcium burden is a significant predictor of cardiovascular morbidity and mortality; however, the underlying mechanisms remain largely unknown. These observations have challenged the previously held notion that calcification serves to stabilize the atherosclerotic plaque. Recent studies have shown that microcalcifications that form within the fibrous cap of the plaques lead to the accrual of plaque-destabilizing mechanical stress. Given the association between calcification morphology and cardiovascular outcomes, it is important to understand the mechanisms leading to calcific mineral deposition and growth from the earliest stages. We highlight the open questions in the field of cardiovascular calcification and include a review of the proposed mechanisms involved in extracellular vesicle-mediated mineral deposition.

Metabolite Profiling Reveals the Effect of Dietary Rubus coreanus Vinegar on Ovariectomy-Induced Osteoporosis in a Rat Model

The study was aimed at exploring the curative effects of Rubus coreanus (RC) vinegar against postmenopausal osteoporosis by using ovariectomized rats as a model. The investigations were performed in five groups: sham, ovariectomized (OVX) rats without treatment, low-dose RC vinegar (LRV)-treated OVX rats, high-dose RC vinegar (HRV)-treated OVX rats and alendronate (ALEN)-treated OVX rats. The efficacy of RC vinegar was evaluated using physical, biochemical, histological and metabolomic parameters. Compared to the OVX rats, the LRV and HRV groups showed positive effects on the aforementioned parameters, indicating estrogen regulation. Plasma metabolome analysis of the groups using gas chromatography-time of flight mass spectrometry (GC-TOF-MS) and ultra-performance liquid chromatography quadrupole-TOF-MS (UPLC-Q-TOF-MS) with multivariate analysis revealed 19 and 16 metabolites, respectively. Notably, the levels of butyric acid, phenylalanine, glucose, tryptophan and some lysophosphatidylcholines were marginally increased in RC vinegar-treated groups compared to OVX. However, the pattern of metabolite levels in RC vinegar-treated groups was found similar to ALEN, but differed significantly from that in sham group. The results highlight the prophylactic and curative potential of dietary vinegar against postmenopausal osteoporosis. RC vinegar could be an effective natural alternative for the prevention of postmenopausal osteoporosis.

Effects of Ketamine on Metabolomics of Serum and Urine in Cynomolgus Macaques (Macaca fascicularis)

In this study, a metabolomics approach based on nuclear magnetic resonance spectroscopy and pertinent multivariate data analyses was used to evaluate the effect of ketamine on metabolic markers in cynomolgus macaques. Principal component analysis and orthogonal projection to latent structure with discriminant analysis showed that ketamine (10 mg/kg) induced metabolic perturbations. Compared with the control group, ketamine-treated macaques had lower serum levels of α-glucose, myoinositol, lactate and succinate and lower urine levels of pyruvate and lactate. In contrast, the levels of leucine in serum and arginine in urine were significantly higher in the ketamine group. Our results also demonstrated that a single injection of ketamine influenced the major energy and amino acid metabolic pathways in cynomolgus macaques. Our study suggests that these influences should be considered in the design of experiments and the interpretation related blood and urine data from ketamine-sedated cynomolgus macaques.

Recent advances in targeting the autotaxin-lysophosphatidate-lipid phosphate phosphatase axis in vivo

Extracellular lysophosphatidate (LPA) is a potent bioactive lipid that signals through six G-protein-coupled receptors. This signaling is required for embryogenesis, tissue repair and remodeling processes. LPA is produced from circulating lysophosphatidylcholine by autotaxin (ATX), and is degraded outside cells by a family of three enzymes called the lipid phosphate phosphatases (LPPs). In many pathological conditions, particularly in cancers, LPA concentrations are increased due to high ATX expression and low LPP activity. In cancers, LPA signaling drives tumor growth, angiogenesis, metastasis, resistance to chemotherapy and decreased efficacy of radiotherapy. Hence, targeting the ATX-LPA-LPP axis is an attractive strategy for introducing novel adjuvant therapeutic options. In this review, we will summarize current progress in targeting the ATX-LPA-LPP axis with inhibitors of autotaxin activity, LPA receptor antagonists, LPA monoclonal antibodies, and increasing low LPP expression. Some of these agents are already in clinical trials and have applications beyond cancer, including chronic inflammatory diseases.

Sphingolipid metabolism and its role in the skeletal tissues

The regulators affecting skeletal tissue formation and its maintenance include a wide array of molecules with very diverse functions. More recently, sphingolipids have been added to this growing list of regulatory molecules in the skeletal tissues. Sphingolipids are integral parts of various lipid membranes present in the cells and organelles. For a long time, these macromolecules were considered as inert structural elements. This view, however, has radically changed in recent years as sphingolipids are now recognized as important second messengers for signal-transduction pathways that affect cell growth, differentiation, stress responses and programmed death. In the current review, we discuss the available data showing the roles of various sphingolipids in three different skeletal cell types-chondrocytes in cartilage and osteoblasts and osteoclasts in bone. We provide an overview of the biology of sphingomyelin phosphodiesterase 3 (SMPD3), an important regulator of sphingolipid metabolism in the skeleton. SMPD3 is localized in the plasma membrane and has been shown to cleave sphingomyelin to generate ceramide, a bioactive lipid second messenger, and phosphocholine, an essential nutrient. SMPD3 deficiency in mice impairs the mineralization in both cartilage and bone extracellular matrices leading to severe skeletal deformities. A detailed understanding of SMPD3 function may provide a novel insight on the role of sphingolipids in the skeletal tissues.

Fatty acid composition in matrix vesicles and in microvilli from femurs of chicken embryos revealed selective recruitment of fatty acids

Hypertrophic chondrocytes participate in matrix mineralization by releasing matrix vesicles (MVs). These MVs, by accumulating Ca(2+) and phosphate initiate the formation of hydroxyapatite. To determine the types of lipids essential for mineralization, we analyzed fatty acids (FAs) in MVs, microvilli and in membrane fractions of chondrocytes isolated from femurs of chicken embryos. The FA composition in the MVs was almost identical to that in microvilli, indicating that the MVs originated from microvilli. These fractions contained more monounsaturated FAs especially oleic acid than in membrane homogenates of chondrocytes. They were enriched in 5,8,11-eicosatrienoic acid (20:3n-9), in eicosadienoic acid (20:2n-6), and in arachidonic acid (20:4n-6). In contrast, membrane homogenates from chondrocytes were enriched in 20:1n-9, 18:3n-3, 22:5n-3 and 22:5n-6. Due to their relatively high content in MVs and to their selective recruitment within microvilli from where MV originate, we concluded that 20:2n-6 and 20:3n-9 (pooled values), 18:1n-9 and 20:4n-6 are essential for the biogenesis of MVs and for bone mineralization.

Autotaxin in the crosshairs: taking aim at cancer and other inflammatory conditions

Autotaxin is a secreted enzyme that produces most of the extracellular lysophosphatidate from lysophosphatidylcholine, the most abundant phospholipid in blood plasma. Lysophosphatidate mediates many physiological and pathological processes by signaling through at least six G-protein coupled receptors to promote cell survival, proliferation and migration. The autotaxin/lysophosphatidate signaling axis is involved in wound healing and tissue remodeling, and it drives many chronic inflammatory conditions from fibrosis to colitis, asthma and cancer. In cancer, lysophosphatidate signaling promotes resistance to chemotherapy and radiotherapy, and increases both angiogenesis and metastasis. Research into autotaxin inhibitors is accelerating, both as primary and adjuvant therapy. Historically, autotaxin inhibitors had poor bioavailability profiles and thus had limited efficacy in vivo. This situation is now changing, especially since the recent crystal structure of autotaxin is now enabling rational inhibitor design. In this review, we will summarize current knowledge on autotaxin-mediated disease processes including cancer, and discuss recent advancements in the development of autotaxin-targeting strategies. We will also provide new insights into autotaxin as an inflammatory mediator in the tumor microenvironment that promotes cancer progression and therapy resistance.

Synthesis of fluorescent gold nanodot-liposome hybrids for detection of phospholipase C and its inhibitor

We report the synthesis of fluorescent 11-mercaptoundecanoic acid-gold nanodot-liposome (11-MUA-Au ND/Lip) hybrids by incorporation of gold nanoparticles (∼3 nm) and 11-MUA molecules in hydrophobic phospholipid membranes that self-assemble to form small unilamellar vesicles. A simple and homogeneous fluorescence assay for phospholipase C (PLC) was developed on the basis of the fluorescence quenching of 11-MUA-Au ND/Lip hybrids in aqueous solution. The fluorescence of the 11-MUA-Au ND/Lip hybrids is quenched by oxygen (O2) molecules in solution, and quenching is reduced in the presence of PLC. PLC catalyzes the hydrolysis of phosphatidylcholine units from Lip to yield diacylglycerol (DAG) and phosphocholine (PC) products, leading to the decomposition of Lip. The diacylglycerol further interacts with 11-MUA-Au NDs via hydrophobic interactions, leading to inhibition of O2 quenching. The 11-MUA-Au ND/Lip probe provides a limit of detection (at a signal-to-noise ratio of 3) of 0.21 nM for PLC, with high selectivity over other proteins, enzymes, and phospholipases. We have validated the practicality of using this probe for the determination of PLC concentrations in breast cancer cells (MCF-7 and MDA-MB-231 cell lines) and nontumor cells (MCF-10A cell line), revealing that the PLC activity in the first two is at least 1.5-fold higher than that in the third. An inhibitor assay using 11-MUA-Au ND/Lip hybrids demonstrated that tricyclodecan-9-yl potassium xanthate (D609) inhibits PLC (10 nM) with an IC50 value of 3.81 ± 0.22 μM. This simple, sensitive, and selective approach holds great potential for detection of PLC in cancer cells and for the screening of anti-PLC drugs.

A comparative proteomics study on matrix vesicles of osteoblast-like Saos-2 and U2-OS cells

Matrix vesicles (MVs) play an important role in the initial stage of the process of bone mineralization, and are involved in multiple rare skeletal diseases with pathological mineralization or calcification. The aim of the study was to compare the proteomic profiling of osteoblast-like cells with and without mineralization ability (Saos-2 and U2-OS), and to identify novel mineralization-associated MV proteins. MVs were extracted using ExoQuick solution from mineralization-induced Saos-2 and U2-OS cells, and then were validated by transmission electron microscopy. A label-free quantitative proteomic method was used to compare the protein profiling of MVs from Saos-2 and U2-OS cells. Western-blots were used to confirm the expression of MVs proteins identified in proteomic studies. In our proteomic studies, we identified that 89 mineralization-related proteins were significantly up-regulated in Saos-2 MVs compared with U2-OS MVs. We further validated that two MVs proteins, protein kinase C α and ras-related protein Ral-A, were up-regulated in MVs of Saos-2 cells compared to those of U2-OS cells under mineralization-induction. Our findings suggest that protein kinase C α and ras-related protein Ral-A might be involved in bone mineralization as MVs components.