Concerted regulation of inorganic pyrophosphate and osteopontin by akp2, enpp1, and ank: an integrated model of the pathogenesis of mineralization disorders

Preclinical evaluation of the efficacy and safety of adeno-associated virus 8-tissue-nonspecific alkaline phosphatase-D10 in Alpl-/- and AlplPrx1/Prx1 mouse models for the treatment of early and late-onset hypophosphatasia

We previously documented successful resolution of skeletal and dental disease in the infantile and late-onset murine models of hypophosphatasia (HPP) with a single injection of an adeno-associated serotype 8 vector encoding mineral-targeted TNAP (AAV8-TNAP-D10). Here, we conducted dosing studies in both HPP mouse models. A single escalating dose from 4 × 108 up to 4 × 1010 (vg/b) was intramuscularly injected into 4-day-old Alpl-/- mice (an infantile HPP model) and a single dose from 4 × 106 up to 4 × 109 (vg/b) was administered to 8-wk-old AlplPrx1/Prx1 mice (a late-onset HPP model). Wild-type littermates were used as controls. Serum alkaline phosphatase activity was increased, and PPi levels were decreased in a dose-dependent manner in both the Alpl-/- and AlplPrx1/Prx1 models. Radiographic and μCT analysis of long bones of female and male Alpl-/- mice showed full correction of skeletal phenotype at 4 × 1010 vg/b. We observed full correction of the bone phenotype at 4 × 108 and 4 × 109 in female AlplPrx1/Prx1 mice, but bones remained hypomineralized with the 4 × 106 and 4 × 107 (vg/b) doses after 70 d of treatment. We observed skeletal improvements using the 4 × 109 (vg/b) dose, but the phenotype was not fully corrected in male AlplPrx1/Prx1. Immunohistochemistry using anti-TNAP and anti-D10 antibodies showed high immunolocalization in the femurs of female AlplPrx1/Prx1 mice, while D10 immunolocalization was high in the liver of male AlplPrx1/Prx1 mice at a dose of 4 × 109 (vg/b). This sex-dependent difference was not seen in the infantile HPP model. A serum proteome analysis showed enhanced inflammatory pathways in treated AlplPrx1/Prx1 males compared to treated female mice. We also found a few areas of ectopic calcification in soft organs at the highest tested dose of 4 × 1010 (vg/b) in Alpl-/- or 4 × 109 (vg/b) in the AlplPrx1/Prx1 model. This pre-clinical study will inform the design of clinical trials to develop gene therapy in early-onset and late-onset HPP patients.

Association between albumin-to-alkaline phosphatase ratio and a 3-month unfavorable outcome in patients with acute ischemic stroke

Background

The albumin-to-alkaline phosphatase ratio (AAPR) is a predictor of several disease outcomes. However, there is no study about AAPR and acute ischemic stroke outcomes. This study aims to investigate the relationship between AAPR and a 3-month unfavorable outcome in patients with acute ischemic stroke.

Methods

This prospective cohort study included 2084 patients with acute ischemic stroke in South Korea. After applying strict exclusion criteria, 1,886 patients were included in our analysis and divided into three groups based on AAPR tertiles. An unfavorable outcome was defined as a 3-month modified Rankin scale (mRS) score > 2. Logistic regression analysis and smooth curve fitting analysis were applied to investigate the relationship between AAPR and unfavorable outcomes. Subgroup analysis was also performed to assess whether influencing factors changed the association between AAPR and unfavorable outcomes.

Results

After adjusting for potential confounders, multivariate analysis showed that AAPR was significantly associated with a 3-month unfavorable outcome (OR 0.18, 95% CI 0.09-0.35, p < 0.001). The smooth curve fitting analysis showed a nonlinear relationship between AAPR and a 3-month unfavorable outcome. The infection point was 0.588 according to the recursive method, and the threshold analysis showed when AAPR was ≤0.588, with the per unit increase of AAPR, the 3-month unfavorable outcome risk decreased by 96% (OR 0.04, 95% CI 0.01-0.2, p < 0.001). However, when AAPR was >0.588, there was no negative correlation between AAPR and a 3-month unfavorable outcome (OR 0.33, 95% CI 0.08-1.3, p = 0.112).

Conclusion

This study is the first to suggest a non-linear relationship between AAPR and a 3-month unfavorable outcome of acute ischemic stroke. AAPR was negatively correlated with a 3-month unfavorable outcome when AAPR was <0.588.

Exploring the Causes of Intervertebral Disc Annulus Fibrosus Impairment

Scope

The annulus fibrosus (AF), as an important component of the intervertebral disc (IVD), contributes to the structural integrity and functional normality of IVD. Degenerative disc diseases (DDD), due to AF impairment, are common problems that could lead to low back pain or neck pain, resulting in considerable disability and financial costs globally. The exact causes and underlying mechanisms of AF impairment, however, remain complex and unclear.

Methods

A literature search was conducted to identify relevant articles published between 1952 and 2024. We summarize the current literature on the potential etiologies of AF damage, while also providing a brief overview of the basic characteristics of the AF and current therapeutic strategies for AF impairment.

Results

The findings suggest that several factors could induce or exacerbate AF impairment. We categorize them into distinct groups as physical and chemical stimuli, nutritional or metabolic disorders, immune and inflammatory responses, and genetic abnormalities.

Conclusion

Various factors could lead to AF impairment, such as particular physical and chemical stimuli, nutritional or metabolic disorders, immune and inflammatory responses, and genetic abnormalities. Meanwhile, enhancing our understanding and management of AF impairment could help discover potential preventive or therapeutic interventions for DDD.

Role of ENPP1 in cancer pathogenesis: Mechanisms and clinical implications (Review)

Cancer is a significant societal, public health and economic challenge in the 21st century, and is the primary cause of death from disease globally. Ectonucleotide pyrophosphatase/phosphodiesterase (ENPP) serves a crucial role in several biochemical processes, including adenosine triphosphate hydrolysis, purine metabolism and regulation of signaling pathways. Specifically, ENPP1, a type II transmembrane glycoprotein and key member of the ENPP family, may be upregulated in tumor cells and implicated in the pathogenesis of multiple human cancers. The present review provides an overview of the structural, pathological and physiological roles of ENPP1 and discusses the potential mechanisms of ENPP1 in the development of cancers such as breast, colon, gallbladder, liver and lung cancers, and also summarizes the four major signaling pathways in tumors. Furthermore, the present review demonstrates that ENPP1 serves a crucial role in cell migration, proliferation and invasion, and that corresponding inhibitors have been developed and associated with clinical characterization.

Integrated Applied Clinical Pharmacology in the Advancement of Rare and Ultra-Rare Disease Therapeutics

The introduction of safe and effective rare/ultra-rare disease treatments is a focus of many biotherapeutic enterprises. Despite this increased activity, a significant unmet need remains, and the responsibility to meet this need is augmented by enhanced genomic, biologic, medical, analytical, and informatic tools. It is recognized that the development of an effective and safe rare/ultra-rare disease therapeutic faces a number of challenges with an important role noted for clinical pharmacology. Clinical pharmacology is foundationally an integrative discipline which must be embedded in and is interdependent upon understanding the pathogenic biology, clinical presentation, disease progression, and end-point assessment of the disease under study. This manuscript presents an overview and two case examples of this integrative approach, the development of C5-targeted therapeutics for the treatment of generalized myasthenia gravis and asfotase alpha for the treatment of hypophosphatasia. The two presented case examples show the usefulness of understanding the biological drivers and clinical course of a rare disease, having relevant animal models, procuring informative natural history data, importing assessment tools from relevant alternative areas, and using integrated applied clinical pharmacology to inform target engagement, dose, and the cascade of pharmacodynamic and clinical effects that follow. Learnings from these programs include the importance of assuring cross-validation of assays throughout a development program and continued commitment to understanding the relationship among the array of Pd end points and clinical outcomes. Using an integrative approach, substantive work remains to be done to meet the unmet needs of patients with rare/ultra-rare disease.

Association between Body Mass Index and Serum Uric Acid: mediation analysis involving liver enzymes indicators

BACKGROUND

Numerous studies have indicated a growing prevalence of hyperuricemia. Elevated levels of serum uric acid (SUA) have been established as influential factors in conditions such as obesity, metabolic syndrome, diabetes mellitus, gout, and cardiovascular disease. Overweight and obesity are closely related to an increase in SUA. Our objective is to demonstrate the mediating role of liver enzyme in the correlation between body mass index (BMI) and SUA.

METHODS

A total of 5925 adults aged 18 to 65 were included in this cross-sectional study. Logistic regression and mediation analysis were used to investigate the relationship between BMI and hyperuricemia as well as liver enzyme levels. Standard methods were used to determine the biochemical indexes, including SUA, liver enzymes, and blood lipids in the collected samples.

RESULTS

The study revealed that the prevalence of hyperuricemia was 28.0%. Furthermore, the prevalence of overweight and obesity was as high as 48.5%, with 70.7% of this subgroup presenting with hyperuricemia. There was a positive correlation between BMI and hyperuricemia, and elevated levels of liver enzymes (ALT, AST, GGT) were associated with a higher risk of hyperuricemia. The study also observed a positive correlation between BMI and liver enzymes (ALT, AST, GGT). The study findings suggested that ALT, AST, and GGT played significant mediating roles in the relationship between BMI and SUA. Specifically, the unadjusted model revealed that ALT and GGT accounted for 22.12% and 18.13% of the mediation effects, respectively.

CONCLUSIONS

The study found that BMI is associated with hyperuricemia, where liver enzyme abnormalities may have a mediating role. It is suggested that being overweight or obese may affect liver enzyme levels, leading to increased SUA levels. Controlling weight and liver enzyme levels may help prevent and treat hyperuricemia.

Blockade of brain alkaline phosphatase efficiently reduces amyloid-β plaque burden and associated cognitive impairment

BACKGROUND

Alzheimer's disease (AD) is the most prevalent neurodegenerative disease. Three new drugs for AD based on monoclonal antibodies against the amyloid-β peptide (Aβ) have recently been approved because they favor the reduction of the burden of senile plaque in the AD patient's brain. Nonetheless, both drugs have very limited applicability and benefits and show several side effects. These limitations invite us to find alternative strategies for treating patients with AD. Here, we explored whether tissue-nonspecific alkaline phosphatase (TNAP), an ectoenzyme upregulated in the brain of AD patients and whose inhibition has beneficial effects on tau-induced pathology, is also efficient in reducing senile plaque burden.

METHODS

To evaluate whether TNAP may reduce cerebral senile plaque loading and Aβ-related toxicity, we use both pharmacological and genetic approaches. We analyze postmortem samples from human AD patients, APP/PS1 mice (a mouse model that mimics amyloid pathology observed in AD patients) treated or not with TNAP inhibitors, and the newly generated transgenic mouse line, TNAP-deficient APP/PS1 mice.

RESULTS

For the first time, we describe that genetic or pharmacological blockade of TNAP effectively reduces senile plaque burden by promoting its clearance, which leads to amelioration of cognitive impairment caused by Aβ-induced toxicity. These beneficial effects of TNAP inhibition occur concomitantly with higher microglial recruitment toward the senile plaque and increased microglial phagocytic capacity of Aβ by a mechanism involving metalloprotease-depending osteopontin processing. In addition, we also found that TNAP blockade favors LRP1-mediated transport of Aβ through the BBB.

CONCLUSIONS

Here, we have shown that TNAP inhibition effectively reduces brain senile plaque burden and associated behavioral defects. Furthermore, given that we had previously reported that TNAP blockade also ameliorates Tau-induced neurotoxicity and increases lifespan of P301S tauopathy mouse model, we can state that TNAP blockade may be a novel and efficient therapy for treating patients with AD.

Calcium Pyrophosphate Crystal Formation and Deposition: Where Do we Stand and What Does the Future hold?

PURPOSE OF THE REVIEW

Although calcium pyrophosphate deposition (CPPD) has been known since the 1960s, our understanding of its pathogenesis remains rudimentary. This review aims to illustrate the known mechanisms underlying calcium pyrophosphate (CPP) crystal formation and deposition and explore future directions in research. By examining various perspectives, from basic research to clinical and imaging assessments, as well as new emerging methodologies, we can establish a starting point for a deeper understanding of CPPD pathogenesis.

RECENT FINDINGS

Recent years have seen significant advances in CPPD research, particularly in the clinical field with the development of the 2023 ACR/EULAR classification criteria for CPPD disease, and in imaging with the introduction of the OMERACT ultrasonographic definitions and scoring system. However, progress in basic research has been slower. New laboratory approaches, such as Raman spectroscopy and omics sciences, offer promising insights that may help piece together the puzzle of CPPD. CPPD is a common yet understudied condition. As the population ages and CPPD becomes more prevalent, there is an urgent need to better understand the disease and the mechanisms involved in crystal formation and deposition, in order to improve diagnosis and therapeutic approaches.

Intersecting Paths: Unraveling the Complex Journey of Cancer to Bone Metastasis

The phenomenon of bone metastases presents a significant challenge within the context of advanced cancer treatments, particularly pertaining to breast, prostate, and lung cancers. These metastatic occurrences stem from the dissemination of cancerous cells into the bone, thereby interrupting the equilibrium between osteoblasts and osteoclasts. Such disruption results in skeletal complications, adversely affecting patient morbidity and quality of life. This review discusses the intricate interplay between cancer cells and the bone microenvironment, positing the bone not merely as a passive recipient of metastatic cells but as an active contributor to cancer progression through its distinctive biochemical and cellular makeup. A thorough examination of bone structure and the dynamics of bone remodeling is undertaken, elucidating how metastatic cancer cells exploit these processes. This review explores the genetic and molecular pathways that underpin the onset and development of bone metastases. Particular emphasis is placed on the roles of cytokines and growth factors in facilitating osteoclastogenesis and influencing osteoblast activity. Additionally, this paper offers a meticulous critique of current diagnostic methodologies, ranging from conventional radiography to advanced molecular imaging techniques, and discusses the implications of a nuanced understanding of bone metastasis biology for therapeutic intervention. This includes the development of targeted therapies and strategies for managing bone pain and other skeletal-related events. Moreover, this review underscores the imperative of ongoing research efforts aimed at identifying novel therapeutic targets and refining management approaches for bone metastases. It advocates for a multidisciplinary strategy that integrates advancements in medical oncology and radiology with insights derived from molecular biology and genetics, to enhance prognostic outcomes and the quality of life for patients afflicted by this debilitating condition. In summary, bone metastases constitute a complex issue that demands a comprehensive and informed approach to treatment. This article contributes to the ongoing discourse by consolidating existing knowledge and identifying avenues for future investigation, with the overarching objective of ameliorating patient care in the domain of oncology.

A retrotransposon-derived DNA zip code internalizes myeloma cells through Clathrin-Rab5a-mediated endocytosis

Introduction

We have demonstrated that transposons derived from ctDNA can be transferred between cancer cells. The present research aimed to investigate the cellular uptake and intracellular trafficking of Multiple Myeloma-zip code (MM-ZC), a cell-specific zip code, in myeloma cell lines. We demonstrated that MM-ZC uptake by myeloma cells was concentration-, time- and cell-type-dependent.

Methods

Flow cytometry and confocal microscopy methods were used to identify the level of internalization of the zip codes in MM cells. To screen for the mechanism of internalization, we used multiple inhibitors of endocytosis. These experiments were followed by biotin pulldown and confocal microscopy for validation. Single interference RNA (siRNA) targeting some of the proteins involved in endocytosis was used to validate the role of this pathway in ZC cell internalization.

Results

Endocytosis inhibitors identified that Monensin and Chlorpromazine hydrochloride significantly reduced MM-ZC internalization. These findings suggested that Clathrin-mediated endocytosis and endosomal maturation play a crucial role in the cellular uptake of MM-ZC. Biotin pulldown and confocal microscopic studies revealed the involvement of proteins such as Clathrin, Rab5a, Syntaxin-6, and RCAS1 in facilitating the internalization of MM-ZC. Knockdown of Rab5a and Clathrin proteins reduced cellular uptake of MM-ZC and conclusively demonstrated the involvement of Clathrin-Rab5a pathways in MM-ZC endocytosis. Furthermore, both Rab5a and Clathrin reciprocally affected their association with MM-ZC when we depleted their proteins by siRNAs. Additionally, the loss of Rab5a decreased the Syntaxin-6 association with MMZC but not vice versa. Conversely, MM-ZC treatment enhanced the association between Clathrin and Rab5a.

Conclusion

Overall, the current study provides valuable insights into the cellular uptake and intracellular trafficking of MM-ZC in myeloma cells. Identifying these mechanisms and molecular players involved in MM-ZC uptake contributes to a better understanding of the delivery and potential applications of cell-specific Zip-Codes in gene delivery and drug targeting in cancer research.

Impact of alkaline phosphatase on clinical outcomes in patients with ischemic stroke: a nationwide registry analysis

Background

Data on the association between serum alkaline phosphatase (ALP) levels and clinical outcomes in patients with ischemic stroke (IS) are inconsistent and limited. Therefore, this study aimed to investigate the correlation between ALP and prognosis in patients with IS.

Methods

Patients with acute ischemic stroke (AIS) or transient ischemic attack (TIA) from the Third China National Stroke Registry were divided into four groups according to the quartiles of serum ALP levels on admission. Cox proportional hazards and logistic regression models were used to evaluate the correlation between ALP and the risk of all-cause mortality, disability (modified Rankin Scale (mRS) score 3-5), and poor functional outcomes (mRS score 3-6).

Results

A total of 11,405 patients were included in the study. Higher levels of ALP were associated with all-cause mortality at 3 months (adjusted hazard ratio [HR] per standard deviation [SD]: 1.16; 95% confidence interval (CI): 1.07-1.27; p = 0.001) and 1 year (adjusted HR: 1.11; 95% CI: 1.03-1.20; p = 0.010). At the 3-month follow-up, each SD increase of ALP was associated with a 12 and 14% higher risk of disability (adjusted odds ratio (OR): 1.12; 95% CI: 1.06-1.18; p < 0.001) and poor functional outcomes (adjusted OR: 1.14; 95% CI: 1.08-1.20; p < 0.001). Similar results were observed at the 1-year follow-up. Higher ALP levels were associated with an increased risk of all-cause mortality, disability, and poor functional outcomes in patients with "others" subtypes (including other determined etiology and undetermined etiology) (p < 0.05).

Conclusion

Elevated ALP levels were associated with an increased risk of all-cause mortality, disability, and poor function outcomes in patients with IS. Heterogeneity was observed among the subtypes of different etiologies.

A new perspective on intervertebral disc calcification-from bench to bedside

Disc degeneration primarily contributes to chronic low back and neck pain. Consequently, there is an urgent need to understand the spectrum of disc degeneration phenotypes such as fibrosis, ectopic calcification, herniation, or mixed phenotypes. Amongst these phenotypes, disc calcification is the least studied. Ectopic calcification, by definition, is the pathological mineralization of soft tissues, widely studied in the context of conditions that afflict vasculature, skin, and cartilage. Clinically, disc calcification is associated with poor surgical outcomes and back pain refractory to conservative treatment. It is frequently seen as a consequence of disc aging and progressive degeneration but exhibits unique molecular and morphological characteristics: hypertrophic chondrocyte-like cell differentiation; TNAP, ENPP1, and ANK upregulation; cell death; altered Pi and PPi homeostasis; and local inflammation. Recent studies in mouse models have provided a better understanding of the mechanisms underlying this phenotype. It is essential to recognize that the presentation and nature of mineralization differ between AF, NP, and EP compartments. Moreover, the combination of anatomic location, genetics, and environmental stressors, such as aging or trauma, govern the predisposition to calcification. Lastly, the systemic regulation of calcium and Pi metabolism is less important than the local activity of PPi modulated by the ANK-ENPP1 axis, along with disc cell death and differentiation status. While there is limited understanding of this phenotype, understanding the molecular pathways governing local intervertebral disc calcification may lead to developing disease-modifying drugs and better clinical management of degeneration-related pathologies.

Nanocomposites of iron oxide, sodium alginate, and eugenol induce apoptosis via PI3K/Akt/mTOR signaling in Hep3 cells and in vivo hepatotoxicity in the zebrafish model

Hepatic cancer is among the most recurrently detected malignancies worldwide and one of the main contributors to cancer-associated mortality. With few available therapeutic choices, there is an instant necessity to explore suitable options. In this aspect, Nanotechnology has been employed to explore prospective chemotherapeutic approaches, especially for cancer treatment. Nanotechnology is concerned with the biological and physical properties of nanoparticles in the therapeutic use of drugs. In the current work, formulation, and characterization of α-Fe2O3-Sodium Alginate-Eugenol nanocomposites (FSE NCs) using several approaches like SEM and TEM, UV-visible, FTIR, and PL spectroscopy, XRD, EDAX, and DLS studies have been performed. With an average size of 50 nm, the rhombohedral structure of NCs was identified. Further, their anticancer activity against Hep3B liver cancer cell lines has been performed by cell viability, dual staining, DCFH-DA, Annexin-V/-FITC/PI, cell cycle analysis methods, and PI3K/Akt/mTOR signaling proteins were studied to assess the anticancer effects of the NCs in Hep3B cells. Also, anti-cancer activity on animal modeling in-vivo using zebra fishes to hematological parameters, liver enzymes, and histopathology study effectiveness was noticed. Moreover, the NCs reduced the viability, elevated the ROS accumulation, diminished the membrane integrity, reduced the antioxidants, blocked the cell cycle, and triggered the PI3K/Akt/mTOR signaling axis that eventually resulted in cell death. As a result, FSE NCs possess huge potential for use as a possible anticancer candidate.

Hypertrophic chondrocytes at the junction of musculoskeletal structures

Hypertrophic chondrocytes are found at unique locations at the junction of skeletal tissues, cartilage growth plate, articular cartilage, enthesis and intervertebral discs. Their role in the skeleton is best understood in the process of endochondral ossification in development and bone fracture healing. Chondrocyte hypertrophy occurs in degenerative conditions such as osteoarthritis. Thus, the role of hypertrophic chondrocytes in skeletal biology and pathology is context dependent. This review will focus on hypertrophic chondrocytes in endochondral ossification, in which they exist in a transient state, but acting as a central regulator of differentiation, mineralization, vascularization and conversion to bone. The amazing journey of a chondrocyte from being entrapped in the extracellular matrix environment to becoming proliferative then hypertrophic will be discussed. Recent studies on the dynamic changes and plasticity of hypertrophic chondrocytes have provided new insights into how we view these cells, not as terminally differentiated but as cells that can dedifferentiate to more progenitor-like cells in a transition to osteoblasts and adipocytes, as well as a source of skeletal stem and progenitor cells residing in the bone marrow. This will provide a foundation for studies of hypertrophic chondrocytes at other skeletal sites in development, tissue maintenance, pathology and therapy.

Contributions of increased osteopontin and hypophosphatemia to dentoalveolar defects in osteomalacic Hyp mice

X-linked hypophosphatemia (XLH) is an inherited disorder caused by inactivating mutations in the PHEX gene leading to renal phosphate wasting, rickets and osteomalacia. XLH is also associated with dentoalveolar mineralization defects in tooth enamel, dentin and cementum, and in alveolar bone, which lead to an increased prevalence of dental abscesses, periodontal disease and tooth loss. Genetic mouse experiments, and deficiencies in XLH patient therapies where treatments do not fully ameliorate mineralization defects, suggest that other pathogenic mechanisms may exist in XLH. The mineralization-inhibiting, secreted extracellular matrix phosphoprotein osteopontin (OPN, gene Spp1) is a substrate for the PHEX enzyme whereby extensive and inactivating degradation of inhibitory OPN by PHEX facilitates mineralization. Conversely, excess OPN accumulation in skeletal and dental tissues - for example in XLH where inactivating mutations in the PHEX gene limit degradation of inhibitory OPN, or as occurs in Fgf23-null mice - contributes to mineralization defects. We hypothesized that Spp1/OPN ablation in Hyp mice (a mouse model for XLH) would reduce dentoalveolar mineralization defects. Immunostaining revealed increased OPN in Hyp vs. wild-type (WT) alveolar bone, particularly in osteocyte lacunocanalicular networks where Hyp mice have characteristic hypomineralized peri-osteocytic lesions (POLs). Micro-computed tomography and histology showed that ablation of Spp1 in Hyp mice (Hyp;Spp1-/-) on a normal diet did not ameliorate bulk defects in enamel, dentin, or alveolar bone. On a high-phosphate diet, both Hyp and Hyp;Spp1-/- mice showed improved mineralization of enamel, dentin, and alveolar bone. Silver staining indicated Spp1 ablation did not improve alveolar or mandibular bone osteocyte POLs in Hyp mice; however, they were normalized by a high-phosphate diet in both Hyp and Hyp;Spp1-/- mice, although inducing increased OPN. Collectively, these data indicate that despite changes in OPN content in the dentoalveolar mineralized tissues, there exist other compensatory mineralization mechanisms that arise from knockout of Spp1/OPN in the Hyp background.

Evidence that pyrophosphate acts as an extracellular signalling molecule to exert direct functional effects in primary cultures of osteoblasts and osteoclasts

Extracellular pyrophosphate (PPi) is well known for its fundamental role as a physiochemical mineralisation inhibitor. However, information about its direct actions on bone cells remains limited. This study shows that PPi decreased osteoclast formation and resorptive activity by ≤50 %. These inhibitory actions were associated with reduced expression of genes involved in osteoclastogenesis (Tnfrsf11a, Dcstamp) and bone resorption (Ctsk, Car2, Acp5). In osteoblasts, PPi present for the entire (0-21 days) or latter stages of culture (7-21/14-21 days) decreased bone mineralisation by ≤95 %. However, PPi present for the differentiation phase only (0-7/0-14 days) increased bone formation (≤70 %). Prolonged treatment with PPi resulted in earlier matrix deposition and increased soluble collagen levels (≤2.3-fold). Expression of osteoblast (RUNX2, Bglap) and early osteocyte (E11, Dmp1) genes along with mineralisation inhibitors (Spp1, Mgp) was increased by PPi (≤3-fold). PPi levels are regulated by tissue non-specific alkaline phosphatase (TNAP) and ecto-nucleotide pyrophosphatase/phosphodiesterase 1 (NPP1). PPi reduced NPP1 expression in both cell types whereas TNAP expression (≤2.5-fold) and activity (≤35 %) were increased in osteoblasts. Breakdown of extracellular ATP by NPP1 represents a key source of PPi. ATP release from osteoclasts and osteoblasts was decreased ≤60 % by PPi and by a selective TNAP inhibitor (CAS496014-12-2). Pertussis toxin, which prevents Gαi subunit activation, was used to investigate whether G-protein coupled receptor (GPCR) signalling mediates the effects of PPi. The actions of PPi on bone mineralisation, collagen production, ATP release, gene/protein expression and osteoclast formation were abolished or attenuated by pertussis toxin. Together these findings show that PPi, modulates differentiation, function and gene expression in osteoblasts and osteoclasts. The ability of PPi to alter ATP release and NPP1/TNAP expression and activity indicates that cells can detect PPi levels and respond accordingly. Our data also raise the possibility that some actions of PPi on bone cells could be mediated by a Gαi-linked GPCR.

Dentoalveolar Alterations in an Adenine-Induced Chronic Kidney Disease Mouse Model

Chronic kidney disease (CKD) is characterized by kidney damage and loss of renal function. CKD mineral and bone disorder (CKD-MBD) describes the dysregulation of mineral homeostasis, including hyperphosphatemia and elevated parathyroid hormone (PTH) secretion, skeletal abnormalities, and vascular calcification. CKD-MBD impacts the oral cavity, with effects including salivary gland dysfunction, enamel hypoplasia and damage, increased dentin formation, decreased pulp volume, pulp calcifications, and altered jaw bones, contributing to clinical manifestations of periodontal disease and tooth loss. Underlying mechanisms are not fully understood, and CKD mouse models commonly require invasive procedures with high rates of infection and mortality. We aimed to characterize the dentoalveolar effects of an adenine diet (AD)-induced CKD (AD-CKD) mouse model. Eight-week-old C57BL/6J mice were provided either a normal phosphorus diet control (CTR) or adenine and high-phosphorus diet CKD to induce kidney failure. Mice were euthanized at 15 weeks old, and mandibles were collected for micro-computed tomography and histology. CKD mice exhibited kidney failure, hyperphosphatemia, and hyperparathyroidism in association with porous cortical bone in femurs. CKD mice showed a 30% decrease in molar enamel volume compared to CTR mice. Enamel wear was associated with reduced ductal components, ectopic calcifications, and altered osteopontin (OPN) deposition in submandibular salivary glands of CKD mice. Molar cusps in CKD mice were flattened, exposing dentin. Molar dentin/cementum volume increased 7% in CKD mice and pulp volume decreased. Histology revealed excessive reactionary dentin and altered pulp-dentin extracellular matrix proteins, including increased OPN. Mandibular bone volume fraction decreased 12% and bone mineral density decreased 9% in CKD versus CTR mice. Alveolar bone in CKD mice exhibited increased tissue-nonspecific alkaline phosphatase localization, OPN deposition, and greater osteoclast numbers. AD-CKD recapitulated key aspects reported in CKD patients and revealed new insights into CKD-associated oral defects. This model has potential for studying mechanisms of dentoalveolar defects or therapeutic interventions. © 2023 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Loss of function mutation in Ank causes aberrant mineralization and acquisition of osteoblast-like-phenotype by the cells of the intervertebral disc

Pathological mineralization of intervertebral disc is debilitating and painful and linked to disc degeneration in a subset of human patients. An adenosine triphosphate efflux transporter, progressive ankylosis (ANK) is a regulator of extracellular inorganic pyrophosphate levels and plays an important role in tissue mineralization. However, the function of ANK in intervertebral disc has not been fully explored. Herein we analyzed the spinal phenotype of Ank mutant mice (ank/ank) with attenuated ANK function. Micro-computed tomography and histological analysis showed that loss of ANK function results in the aberrant annulus fibrosus mineralization and peripheral disc fusions with cranial to caudal progression in the spine. Vertebrae in ank mice exhibit elevated cortical bone mass and increased tissue non-specific alkaline phosphatase-positive endplate chondrocytes with decreased subchondral endplate porosity. The acellular dystrophic mineral inclusions in the annulus fibrosus were localized adjacent to apoptotic cells and cells that acquired osteoblast-like phenotype. Fourier transform infrared spectral imaging showed that the apatite mineral in the outer annulus fibrosus had similar chemical composition to that of vertebral bone. Transcriptomic analysis of annulus fibrosus and nucleus pulposus tissues showed changes in several biological themes with a prominent dysregulation of BMAL1/CLOCK circadian regulation. The present study provides new insights into the role of ANK in the disc tissue compartments and highlights the importance of local inorganic pyrophosphate metabolism in inhibiting the mineralization of this important connective tissue.

Salivary microbiome and hypertension in the Qatari population

BACKGROUND

The prevalence of hypertension in Qatar is 33 percent of the adult population. It is postulated that the salivary microbiome can regulate blood pressure (BP). However, limited investigations exist to prove this hypothesis. Therefore, we examined the difference in the salivary microbiome composition between hypertensive and normotensive Qatari subjects.

METHODS

A total of 1190 Qatar Genome Project (QGP) participants (Mean age = 43 years) were included in this study. BP for all participants was classified into Normal (n = 357), Stage1 (n = 336), and Stage2: (n = 161) according to the American Heart Association guidelines. 16S-rRNA libraries were sequenced and analyzed using QIIME-pipeline, and PICRUST was used to predict functional metabolic routes. Machine Learning (ML) strategies were applied to identify salivary microbiome-based predictors of hypertension.

RESULTS

Differential abundant analysis (DAA) revealed that Bacteroides and Atopobium were the significant members of the hypertensive groups. Alpha and beta diversity indices indicated dysbiosis between the normotensive and hypertensive groups. ML-based prediction models revealed that these markers could predict hypertension with an AUC (Area under the curve) of 0.89. Functional predictive analysis disclosed that Cysteine and Methionine metabolism and the sulphur metabolic pathways involving the renin-angiotensin system were significantly higher in the normotensive group. Therefore, members of Bacteroides and Atopobium can serve as predictors of hypertension. Likewise, Prevotella, Neisseria, and Haemophilus can be the protectors that regulate BP via nitric acid synthesis and regulation of the renin-angiotensin system.

CONCLUSION

It is one of the first studies to assess salivary microbiome and hypertension as disease models in a large cohort of the Qatari population. Further research is needed to confirm these findings and validate the mechanisms involved.

Matrix Metalloproteinases Contribute to the Calcification Phenotype in Pseudoxanthoma Elasticum

Ectopic calcification and dysregulated extracellular matrix remodeling are prominent hallmarks of the complex heterogenous pathobiochemistry of pseudoxanthoma elasticum (PXE). The disease arises from mutations in ABCC6, an ATP-binding cassette transporter expressed predominantly in the liver. Neither its substrate nor the mechanisms by which it contributes to PXE are completely understood. The fibroblasts isolated from PXE patients and Abcc6-/- mice were subjected to RNA sequencing. A group of matrix metalloproteinases (MMPs) clustering on human chromosome 11q21-23, respectively, murine chromosome 9, was found to be overexpressed. A real-time quantitative polymerase chain reaction, enzyme-linked immunosorbent assay and immunofluorescent staining confirmed these findings. The induction of calcification by CaCl2 resulted in the elevated expression of selected MMPs. On this basis, the influence of the MMP inhibitor Marimastat (BB-2516) on calcification was assessed. PXE fibroblasts (PXEFs) exhibited a pro-calcification phenotype basally. PXEF and normal human dermal fibroblasts responded with calcium deposit accumulation and the induced expression of osteopontin to the addition of Marimastat to the calcifying medium. The raised MMP expression in PXEFs and during cultivation with calcium indicates a correlation of ECM remodeling and ectopic calcification in PXE pathobiochemistry. We assume that MMPs make elastic fibers accessible to controlled, potentially osteopontin-dependent calcium deposition under calcifying conditions.

Role of carboxylic organic molecules in interfibrillar collagen mineralization

Bone is a composite material made up of inorganic and organic counterparts. Most of the inorganic counterpart accounts for calcium phosphate (CaP) whereas the major organic part is composed of collagen. The interfibrillar mineralization of collagen is an important step in the biomineralization of bone and tooth. Studies have shown that synthetic CaP undergoes auto-transformation to apatite nanocrystals before entering the gap zone of collagen. Also, the synthetic amorphous calcium phosphate/collagen combination alone is not capable of initiating apatite nucleation rapidly. Therefore, it was understood that there is the presence of a nucleation catalyst obstructing the auto-transformation of CaP before entering the collagen gap zone and initiating rapid nucleation after entering the collagen gap zone. Therefore, studies were focused on finding the nucleation catalyst responsible for the regulation of interfibrillar collagen mineralization. Organic macromolecules and low-molecular-weight carboxylic compounds are predominantly present in the bone and tooth. These organic compounds can interact with both apatite and collagen. Adsorption of the organic compounds on the apatite nanocrystal governs the nucleation, crystal growth, lattice orientation, particle size, and distribution. Additionally, they prevent the auto-transformation of CaP into apatite before entering the interfibrillar compartment of the collagen fibril. Therefore, many carboxylic organic compounds have been utilized in developing CaP. In this review, we have covered different carboxylate organic compounds governing collagen interfibrillar mineralization.

Tideglusib enhances odontogenic differentiation in human dental pulp stem cells in vitro

AIM

Tideglusib is a small molecule agonist of the canonical Wnt pathway. The present study investigated the influence of Tideglusib on human dental pulp stem cell (hDPSC) proliferation, apoptosis, migration and odonto/osteogenic differentiation.

METHODOLOGY

hDPSCs were treated with 50, 100 nM or 200 nM Tideglusib. β-catenin accumulation was detected by immunofluorescence staining. Colony-forming unit ability was assessed by staining with Coomassie blue. Cell cycle progression and cell apoptosis were investigated using flow cytometry. Cell migration was examined using an in vitro wound-healing assay. Osteogenic differentiation was examined using alkaline phosphatase (ALP) staining, alizarin red S staining and osteogenic-related gene expression. The gene expression profile was examined using a high-throughput RNA sequencing technique. All experiments were repeated using cells derived from at least four different donors (n = 4). The Mann-Whitney U-test was used to identify significant differences between two independent group comparisons. For three or more group comparisons, statistical differences were assessed using the Kruskal-Wallis test followed by pairwise comparison. The significance level was set at 5% (p < .05).

RESULTS

Tideglusib activated the Wnt signalling pathway in hDPSCs as demonstrated by an increase in cytoplasmic β-catenin accumulation and nuclear translocation. Tideglusib did not affect hDPSC proliferation, cell cycle progression, cell apoptosis or cell migration. In contrast, 50 and 100 nM Tideglusib significantly enhanced mineralization and osteogenic marker gene expression (RUNX2, ALP, BMP2 and DSPP; p < .05).

CONCLUSIONS

Tideglusib enhanced the odonto/osteogenic differentiation of hDPSCs. Therefore, incorporating this bioactive molecule in a pulp-capping material could be a promising strategy to promote dentine repair.

Gene Therapy Using Recombinant AAV Type 8 Vector Encoding TNAP-D10 Improves the Skeletal Phenotypes in Murine Models of Osteomalacia

Hypophosphatasia (HPP), caused by loss-of-function mutations in the ALPL gene encoding tissue-nonspecific alkaline phosphatase (TNAP), is characterized by skeletal and dental hypomineralization that can vary in severity from life-threatening to milder manifestations only in adulthood. PHOSPHO1 deficiency leads to early-onset scoliosis, osteomalacia, and fractures that mimic pseudo-HPP. Asfotase alfa, a life-saving enzyme replacement therapy approved for pediatric-onset HPP, requires subcutaneous injections 3 to 6 times per week. We recently showed that a single injection of an adeno-associated virus vector serotype 8 harboring TNAP-D10 (AAV8-TNAP-D10) effectively prevented skeletal disease and prolonged life in Alpl -/- mice phenocopying infantile HPP. Here, we aimed to determine the efficacy of AAV8-TNAP-D10 in improving the skeletal and dental phenotype in the Alpl Prx1/Prx1 and Phospho1 -/- mouse models of late-onset (adult) HPP and pseudo-HPP, respectively. A single dose of 3 × 1011 vector genomes per body (vg/b) was injected intramuscularly into 8-week-old Alpl Prx1/Prx1 and wild-type (WT) littermates, or into 3-day-old Phospho1 -/- and WT mice, and treatment efficacy was evaluated after 60 days for late-onset HPP mice and after 90 days for Phospho1 -/- mice. Biochemical analysis showed sustained serum alkaline phosphatase activity and reduced plasma PPi levels, and radiographic images, micro-computed tomography (micro-CT) analysis, and hematoxylin and eosin (H&E) staining showed improvements in the long bones in the late-onset HPP mice and corrected scoliosis in the Phospho1 -/- mice. Micro-CT analysis of the dentoalveolar complex did not reveal significant changes in the phenotype of late-onset HPP and pseudo-HPP models. Moreover, alizarin red staining analysis showed that AAV8-TNAP-D10 treatment did not promote ectopic calcification of soft organs in adult HPP mice after 60 days of treatment, even after inducing chronic kidney disease. Overall, the AAV8-TNAP-D10 treatment improved the skeletal phenotype in both the adult HPP and pseudo-HPP mouse models. This preclinical study will contribute to the advancement of gene therapy for the improvement of skeletal disease in patients with heritable forms of osteomalacia. © 2022 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Inhibition of alkaline phosphatase impairs dyslipidemia and protects mice from atherosclerosis

Calcium accumulation in atherosclerotic plaques predicts cardiovascular mortality, but the mechanisms responsible for plaque calcification and how calcification impacts plaque stability remain debated. Tissue-nonspecific alkaline phosphatase (TNAP) recently emerged as a promising therapeutic target to block cardiovascular calcification. In this study, we sought to investigate the effect of the recently developed TNAP inhibitor SBI-425 on atherosclerosis plaque calcification and progression. TNAP levels were investigated in ApoE-deficient mice fed a high-fat diet from 10 weeks of age and in plaques from the human ECLAGEN biocollection (101 calcified and 14 non-calcified carotid plaques). TNAP was inhibited in mice using SBI-425 administered from 10 to 25 weeks of age, and in human vascular smooth muscle cells (VSMCs) with MLS-0038949. Plaque calcification was imaged in vivo with ¹⁸F-NaF-PET/CT, ex vivo with osteosense, and in vitro with alizarin red. Bone architecture was determined with µCT. TNAP activation preceded and predicted calcification in human and mouse plaques, and TNAP inhibition prevented calcification in human VSMCs and in ApoE-deficient mice. More unexpectedly, TNAP inhibition reduced the blood levels of cholesterol and triglycerides, and protected mice from atherosclerosis, without impacting the skeletal architecture. Metabolomics analysis of liver extracts identified phosphocholine as a substrate of liver TNAP, who's decreased dephosphorylation upon TNAP inhibition likely reduced the release of cholesterol and triglycerides into the blood. Systemic inhibition of TNAP protects from atherosclerosis, by ameliorating dyslipidemia, and preventing plaque calcification.

Evaluation of De Ritis (AST/ALT), ALP/ALT, and AST/ALP ratios as prognostic factors in patients with acute ischemic stroke

BACKGROUND

Stroke is one of the leading causes of disability worldwide. Recently, stroke prognosis estimation has received much attention. This study investigates the prognostic role of aspartate transaminase/alanine transaminase (De Ritis, AAR), alkaline phosphatase/alanine transaminase (ALP/ALT), and aspartate transaminase/alkaline phosphatase (AST/ALP) ratios in acute ischemic stroke (AIS).

METHODS

This retrospective cohort study involved patients who experienced their first-ever AIS between September 2019 and June 2021. Clinical and laboratory data were collected within the first 24 hours after admission. Functional and mortality outcomes were evaluated 90 days after hospital discharge in clinical follow-up. Functional outcome was assessed by a modified Rankin Scale (mRS). The correlation between the laboratory data and study outcomes was evaluated using univariate analysis. In addition, regression models were developed to evaluate the predictive role of AST/ALP, ALP/ALT, and AAR ratios on the study outcomes.

RESULTS

Two hundred seventy-seven patients (mean age 69.10 ± 13.55, 53.1% female) were included. According to univariate analysis, there was a weak association between 3-months mRS, and both AST/ALT (r = 0.222, P < 0.001), and AST/ALP (r = 0.164, P = 0.008). Subsequently, higher levels of these ratios and absolute values of AST, ALT, and ALP were reported in deceased patients. Based on regression models adjusted with co-variable (age, gender, underlying disease, and history of smoking) AST/ALT and AST/ALP ratios had a significant independent association with 3-month mRS (CI:1.37-4.52, p = 0.003, and CI: 4.45-11,547.32, p = 0.007, respectively) and mortality (CI: 0.17-1.06, adjusted R² = 0.21, p = 0.007, and CI: 0.10-2.91, p = 0.035, adjusted R² = 0.20, respectively).

CONCLUSIONS

Elevated AST/ALP and AAR ratios at admission were correlated with poorer outcomes at 3 months in patients with first-ever AIS. Prospective studies in larger cohorts are required to confirm our findings and to evaluate further whether the AST/ALP and De Ritis ratios may represent a useful tool for determining the prognosis of AIS patients.

Shedding Light on the Role of Na,K-ATPase as a Phosphatase during Matrix-Vesicle-Mediated Mineralization

Matrix vesicles (MVs) contain the whole machinery necessary to initiate apatite formation in their lumen. We suspected that, in addition to tissue-nonspecific alkaline phosphatase (TNAP), Na,K,-ATPase (NKA) could be involved in supplying phopshate (P_i) in the early stages of MV-mediated mineralization. MVs were extracted from the growth plate cartilage of chicken embryos. Their average mean diameters were determined by Dynamic Light Scattering (DLS) (212 ± 19 nm) and by Atomic Force Microcopy (AFM) (180 ± 85 nm). The MVs had a specific activity for TNAP of 9.2 ± 4.6 U·mg^-1 confirming that the MVs were mineralization competent. The ability to hydrolyze ATP was assayed by a colorimetric method and by ³¹P NMR with and without Levamisole and SBI-425 (two TNAP inhibitors), ouabain (an NKA inhibitor), and ARL-67156 (an NTPDase1, NTPDase3 and Ecto-nucleotide pyrophosphatase/phosphodiesterase 1 (NPP1) competitive inhibitor). The mineralization profile served to monitor the formation of precipitated calcium phosphate complexes, while IR spectroscopy allowed the identification of apatite. Proteoliposomes containing NKA with either dipalmitoylphosphatidylcholine (DPPC) or a mixture of 1:1 of DPPC and dipalmitoylphosphatidylethanolamine (DPPE) served to verify if the proteoliposomes were able to initiate mineral formation. Around 69-72% of the total ATP hydrolysis by MVs was inhibited by 5 mM Levamisole, which indicated that TNAP was the main enzyme hydrolyzing ATP. The addition of 0.1 mM of ARL-67156 inhibited 8-13.7% of the total ATP hydrolysis in MVs, suggesting that NTPDase1, NTPDase3, and/or NPP1 could also participate in ATP hydrolysis. Ouabain (3 mM) inhibited 3-8% of the total ATP hydrolysis by MVs, suggesting that NKA contributed only a small percentage of the total ATP hydrolysis. MVs induced mineralization via ATP hydrolysis that was significantly inhibited by Levamisole and also by cleaving TNAP from MVs, confirming that TNAP is the main enzyme hydrolyzing this substrate, while the addition of either ARL-6715 or ouabain had a lesser effect on mineralization. DPPC:DPPE (1:1)-NKA liposome in the presence of a nucleator (PS-CPLX) was more efficient in mineralizing compared with a DPPC-NKA liposome due to a better orientation of the NKA active site. Both types of proteoliposomes were able to induce apatite formation, as evidenced by the presence of the 1040 cm^-1 band. Taken together, the findings indicated that the hydrolysis of ATP was dominated by TNAP and other phosphatases present in MVs, while only 3-8% of the total hydrolysis of ATP could be attributed to NKA. It was hypothesized that the loss of Na/K asymmetry in MVs could be caused by a complete depletion of ATP inside MVs, impairing the maintenance of symmetry by NKA. Our study carried out on NKA-liposomes confirmed that NKA could contribute to mineral formation inside MVs, which might complement the known action of PHOSPHO1 in the MV lumen.

Proposing a clinical algorithm for better diagnosis of hypophosphatasia in resource-limiting situations

Early diagnosis of hypophosphatasia (HPP) is challenging. Here, we propose to broaden the diagnostic criteria of HPP by reviewing published data on BMD and fractures in HPP patients. Non-osteoporotic fractures and higher than normal lumbar BMD were recurrent in HPP patients and could be included as diagnostic criteria. HPP is a genetic disorder caused by autosomal recessive or dominant loss-of-function mutations in the ALPL gene that encodes for tissue-nonspecific alkaline phosphatase (TNSALP). Expressive genetic heterogeneity and varying severity of TNSALP deficiency lead to a wide-ranging presentation of skeletal diseases at different ages that coupled with HPP's rarity and limitation of biochemical and mutational studies present serious hurdles to early diagnosis and management of HPP. To widen the scope of HPP diagnosis, we assessed the possibility of areal bone mineral density (BMD) as an additional clinical feature of this disease. PubMed, Web of Science, and ScienceDirect were searched with the following keywords: ("Hypophosphatasia OR HPP") AND ("Bone Mineral Density OR BMD") AND "Human". Studies and case reports of subjects with age ≥ 18 years and having BMD data were included. We pooled data from 25 publications comprising 356 subjects (90 males, 266 females). Only four studies had a control group. Biochemical hallmarks, pyridoxal 5'-phosphate (PLP) and phosphoethanolamine (PEA), were reported in fifteen and six studies, respectively. Twenty studies reported genetic data, nineteen studies reported non-vertebral fractures, all studies reported lumbar spine (LS) BMD, and nineteen reported non-vertebral BMD. Higher than normal and normal BMD at LS were reported in three and two studies, respectively. There was marked heterogeneity in BMD at the non-vertebral sites. Higher than normal or normal LS BMD in an adult with minimal or insufficient fractures, pseudofractures, non-healing fractures, fragility fractures, and stress fractures may be included in the diagnostic protocol of HPP. However, genetic testing is recommended for a definitive diagnosis.

In Vitro and In Vivo Pharmacological Profiles of DS-1211, a Novel Potent, Selective, and Orally Bioavailable Tissue-Nonspecific Alkaline Phosphatase Inhibitor

Inhibition of tissue-nonspecific alkaline phosphatase (TNAP) may prevent ectopic soft tissue calcification by increasing endogenous pyrophosphate (PPi). DS-1211 is a potent and selective novel small molecule TNAP inhibitor with well-characterized pharmacokinetics (PKs) in rodent and monkey. Herein, we report a comprehensive summary of studies establishing the pharmaceutical profile of DS-1211. In vitro studies characterized the mode of inhibition and inhibitory effects of DS-1211 on three human alkaline phosphatase (ALP) isozymes-TNAP, human intestinal ALP, human placental ALP-and on ALP activity across species in mouse, monkey, and human plasma. In vivo PK and pharmacodynamic (PD) effects of a single oral dose of DS-1211 in mice and monkeys were evaluated, including biomarker changes in PPi and pyridoxal 5'-phosphate (PLP). Oral bioavailability (BA) was determined through administration of DS-1211 at a 0.3-mg/kg dose in monkeys. In vitro experiments demonstrated DS-1211 inhibited ALP activity through an uncompetitive mode of action. DS-1211 exhibited TNAP selectivity and potent inhibition of TNAP across species. In vivo studies in mice and monkeys after single oral administration of DS-1211 showed linear PKs, with dose-dependent inhibition of ALP activity and increases in plasma PPi and PLP. Inhibitory effects of DS-1211 were consistent in both mouse and monkey. Mean absolute oral BA was 73.9%. Overall, in vitro and in vivo studies showed DS-1211 is a potent and selective TNAP inhibitor across species. Further in vivo pharmacology studies in ectopic calcification animal models and clinical investigations of DS-1211 in patient populations are warranted. © 2022 Daiichi Sankyo, Inc. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Dual peptide-functionalized hydrogels differentially control periodontal cell function and promote tissue regeneration

Restoring the tooth-supporting tissues lost during periodontitis is a significant clinical challenge, despite advances in both biomaterial and cell-based approaches. This study investigated poly(ethylene glycol) (PEG) hydrogels functionalized with integrin-binding peptides RGD and GFOGER for controlling periodontal ligament cell (PDLC) activity and promoting periodontal tissue regeneration. Dual presentation of RGD and GFOGER within PEG hydrogels potentiated two key PDLC functions, alkaline phosphatase (ALP) activity and matrix mineralization, over either peptide alone and could be tuned to differentially promote each function. Hydrogel matrix mineralization, fostered by high concentrations of GFOGER together with RGD, identified a PDLC phenotype with accelerated matrix adhesion formation and expression of cementoblast and osteoblast genes. In contrast, maximizing ALP activity through high RGD and low GFOGER levels resulted in minimal hydrogel mineralization, in part, through altered PDLC pyrophosphate regulation. Transplantation of PDLCs in hydrogels optimized for either outcome promoted cementum formation in rat periodontal defects; however, only hydrogels optimized for in vitro mineralization improved new bone formation. Overall, these results highlight the utility of engineered hydrogel systems for controlling PDLC functions and their promise for promoting periodontal tissue regeneration.

Between a rock and a hard place: Regulation of mineralization in the periodontium

The periodontium supports and attaches teeth via mineralized and nonmineralized tissues. It consists of two, unique mineralized tissues, cementum and alveolar bone. In between these tissues, lies an unmineralized, fibrous periodontal ligament (PDL), which distributes occlusal forces, nourishes and invests teeth, and harbors progenitor cells for dentoalveolar repair. Many unanswered questions remain regarding periodontal biology. This review will focus on recent research providing insights into one enduring mystery: the precise regulation of the hard-soft tissue borders in the periodontium which define the interfaces of the cementum-PDL-alveolar bone structure. We will focus on advances in understanding the molecular mechanisms that maintain the unmineralized PDL "between a rock and a hard place" by regulating the mineralization of cementum and alveolar bone.

Bone-microarchitecture and bone-strength in a sample of adults with hypophosphatasia and a matched reference population assessed by HR-pQCT and impact microindentation

BACKGROUND

Hypophosphatasia (HPP) is an autosomal recessive or dominate disease affecting bone mineralization, and adults with HPP are in risk to develop metatarsal stress fractures and femoral pseudofractures. Given to the scarce data on the bone quality and its association to the fracture risk in adults with HPP, this study aimed to evaluate bone turnover, bone strength and structure in adults with HPP.

METHODS

In this cross-sectional study, we included 14 adults with genetically verified HPP and 14 sex-, age-, BMI-, and menopausal status-matched reference individuals. We analyzed bone turnover markers, and measured bone material strength index (BMSi) by impact microindentation. Bone geometry, volumetric density and bone microarchitecture as well as failure load at the distal radius and tibia were evaluated using a second-generation high-resolution peripheral quantitative computed tomography system.

RESULTS

Bone turnover markers did not differ between patients with HPP and reference individuals. BMSi did not differ between the groups (67.90 [63.75-76.00] vs 65.45 [58.43-69.55], p = 0.149). Parameters of bone geometry and volumetric density did not differ between adults with HPP and the reference group. Patients with HPP had a tendency toward higher trabecular separation (0.664 [0.613-0.724] mm vs 0.620 [0.578-0.659] mm, p = 0.054) and inhomogeneity of trabecular network (0.253 [0.235-0.283] mm vs 0.229 [0.208-0.252] mm, p = 0.056) as well as lower trabecular bone volume fraction (18.8 [16.4-22.7] % vs 22.8 [20.6-24.7] %, p = 0.054) at the distal radius. In addition, compound heterozygous adults with HPP had a significantly higher cortical porosity at the distal radius than reference individuals (1.5 [0.9-2.2] % vs 0.7 [0.6-0.7] %, p = 0.041).

CONCLUSIONS

BMSi is not reduced in adults with HPP. Increased cortical porosity may contribute to the occurrence of femoral pseudofractures in compound heterozygous adults with HPP. However, further studies investigating larger cohorts of adults with HPP using methods of bone histomorphometry are recommended to adequately assess the bone quality in adults with HPP.

Preoperative Serum Alkaline Phosphatase and Neurological Outcome of Cerebrovascular Surgery

This study evaluated the relationship between the preoperative alkaline phosphatase (ALP) level and major postoperative neurological complications in patients undergoing cerebral bypass surgery. This was a retrospective analysis of a prospective database of all patients undergoing cerebral bypass surgery after a diagnosis of cerebrovascular stenosis or occlusion between May 2003 and August 2017. The patients were divided into tertiles based on serum alkaline phosphatase (ALP) levels (low: <63, intermediate: 63~79, and high: ALP > 79 IU/mL). The incidence of neurological events according to ALP level was analyzed. The study analyzed 211 cases. The incidence of acute infarction was highest in the third serum ALP tertile (5.7% vs. 2.9% vs. 16.9% in the first, second, and third tertile, respectively, p = 0.007). Logistic regression analysis showed that the third tertile of serum ALP was an independent predictor of acute cerebral infarction (odds ratio 3.346, 95% confidence interval 1.026−10.984, p = 0.045). On Kaplan−Meier time-to-event curves, the incidence of acute infarction increased significantly with ALP (log rank = 0.048). Preoperative serum ALP level can be used as a biomarker to predict acute cerebral infarction in patients undergoing cerebral bypass surgery for vascular stenosis or occlusion.

Alkaline Phosphatase: An Old Friend as Treatment Target for Cardiovascular and Mineral Bone Disorders in Chronic Kidney Disease

Alkaline phosphatase (ALP) is an evolutionary conserved enzyme and widely used biomarker in clinical practice. Tissue-nonspecific alkaline phosphatase (TNALP) is one of four human isozymes that are expressed as distinct TNALP isoforms after posttranslational modifications, mainly in bone, liver, and kidney tissues. Beyond the well-known effects on bone mineralization, the bone ALP (BALP) isoforms (B/I, B1, B1x, and B2) are also involved in the pathogenesis of ectopic calcification. This narrative review summarizes the recent clinical investigations and mechanisms that link ALP and BALP to inflammation, metabolic syndrome, vascular calcification, endothelial dysfunction, fibrosis, cardiovascular disease, and mortality. The association between ALP, vitamin K, bone metabolism, and fracture risk in patients with chronic kidney disease (CKD) is also discussed. Recent advances in different pharmacological strategies are highlighted, with the potential to modulate the expression of ALP directly and indirectly in CKD–mineral and bone disorder (CKD-MBD), e.g., epigenetic modulation, phosphate binders, calcimimetics, vitamin D, and other anti-fracture treatments. We conclude that the significant evidence for ALP as a pathogenic factor and risk marker in CKD-MBD supports the inclusion of concrete treatment targets for ALP in clinical guidelines. While a target value below 120 U/L is associated with improved survival, further experimental and clinical research should explore interventional strategies with optimal risk–benefit profiles. The future holds great promise for novel drug therapies modulating ALP.

Nucleotide pyrophosphatase/phosphodiesterases (NPPs) including NPP1 and NPP2/ ATX as important drug targets: A patent review (2015-2020)

INTRODUCTION

Nucleoside triphosphate diphosphohydrolases (NTPDases), alkaline phosphatases (APs), and ecto-nucleotide pyrophosphatases/phosphodiesterases (NPPs) are nucleotidases found on the cell surface. It is a promising therapeutic target for a range of disorders, including fibrosis, tumour metastasis, pruritus, inflammation, multiple sclerosis, and autoimmune diseases. As a result, therapeutic intervention including selective inhibitors of NPPs is required.

AREA COVERED

Many chemical substances, including pyrazole, pyridine and bicyclic compounds have demonstrated promising inhibitory potential for ecto-nucleotide pyrophosphatase/phosphodiesterases. The chemistry and clinical applications of NPPs inhibitors patented between 2015 and 2020 are discussed in this review.

EXPERT OPINION

: In recent years, there has been a lot of effort put into finding effective and selective inhibitors of NPPs. Despite the fact that a variety of synthetic inhibitors have been created, only a few investigations on their in vivo activity have been published. In addition to IOA-289 which has passed Phase Ia clinical trials; potent ATX inhibitor compounds such as BLD-0409, IPF and BBT-877 have been placed in phase I clinical studies. Some of the most promising ATX inhibitors in recent years are closely related analogs of previously known inhibitors, such as PF-8380. Knowledge of the structure activity relationship of such promising inhibitors can potentially translate into the discovery of more potent and effective inhibitors of NPP with a variety of structural characteristics and favourable therapeutic activities.

Chondrocyte-derived exosomes promote cartilage calcification in temporomandibular joint osteoarthritis

BACKGROUNDS

Abnormal cartilage calcification is one of the pathological changes of temporomandibular joint (TMJ) osteoarthritis (OA). Recent studies have reported that exosomes can regulate the formation of abnormal calcified nodules in diseases including atherosclerosis and chronic kidney disease. However, the influences of chondrocyte-derived exosomes on abnormal cartilage calcification in TMJ OA are still unclear.

METHODS

TMJ OA was induced by unilateral anterior crossbite (UAC) for 4, 8, or 12 weeks in rats to observe abnormal calcification in TMJ condylar cartilage and exosome formation. Concomitantly, GW4869, the inhibitor of exosome formation, was locally injected to the TMJ of rats under stimulation of UAC, while the exosomes extracted from primary condylar chondrocytes stimulated with fluid flow shear stress (FFSS) were locally injected to rats TMJ.

RESULTS

Abnormal calcification was enhanced in the degenerative cartilage of TMJ OA in UAC rats, and a large number of exosome-like structures with diameters of 50-150 nm were found in the calcified cartilage together with decreased expression of matrix Gla protein (MGP) and increased expression of CD63, tissue-nonspecific alkaline phosphatase (TNAP) and nucleotide pyrophosphatase/phosphodiesterase-1 (NPP1). After FFSS stimulation, the number of exosomes secreted by chondrocytes and the numbers of calcified nodules were increased in cultured cells, and the protein levels of MGP, TNAP, and NPP1 in exosomes were changed. Inhibition of exosome formation, TNAP, and NPP1 or supplementation with exogenous MGP effectively alleviated FFSS-induced chondrocyte calcification. Local injection of GW4869, the exosome inhibitor, alleviated TMJ OA-related cartilage degeneration and calcification in UAC rats. Local injection of exosomes obtained from chondrocytes stimulated by FFSS to the TMJs of normal rats induced cartilage degeneration and calcification similar to that in TMJ OA.

CONCLUSIONS

Abnormal biomechanical loading leads to enhanced formation of chondrocyte-derived exosomes, in which promoters of calcification increased and inhibitors decreased, resulting in accelerating abnormal cartilage calcification in TMJ OA. The inhibition of degenerative chondrocyte-derived exosomes is expected to be a new way to prevent and treat TMJ OA.

Interaction of Serum Alkaline Phosphatase and Folic Acid Treatment on Chronic Kidney Disease Progression in Treated Hypertensive Adults

The relation of alkaline phosphatase (ALP) with chronic kidney disease (CKD) is still uncertain. We aimed to examine the prospective association between serum ALP and CKD progression, and the modifying effect of serum ALP on folic acid in preventing CKD progression in treated hypertensive patients. This is a post-hoc analysis of 12,734 hypertensive adults with relevant measurements and without liver disease at baseline from the renal sub-study of the China Stroke Primary Prevention Trial, where participants were randomly assigned to daily treatments of 10 mg enalapril and 0.8 mg folic acid, or 10 mg enalapril alone. The primary outcome was CKD progression, defined as a decrease in estimated glomerular filtration rate (eGFR) of ≥30% and to a level of <60 ml/min/1.73 m² if baseline eGFR was ≥60 ml/min/1.73 m²; or a decrease in eGFR of ≥50% if baseline eGFR was <60 ml/min/1.73 m²; or end-stage renal disease. Over a median of 4.4 years, in the enalapril only group, participants with baseline serum ALP≥110IU/L (quartile 4) had a significantly higher risk of CKD progression (3.4% vs 2.3%; adjusted OR,1.61; 95%CI:1.11, 2.32), compared with those with ALP<110IU/L. For those with enalapril and folic acid treatment, compared with the enalapril only treatment, the risk of CKD progression was reduced from 3.4 to 2.1% (adjusted OR, 0.53; 95%CI:0.34, 0.83) among participants with baseline ALP≥110IU/L, whereas there was no significant effect among those with ALP<110IU/L. In hypertensive patients, higher serum ALP was associated with increased risk of CKD progression, and this risk was reduced by 47% with folic acid treatment.

Effects of tralopyril on histological, biochemical and molecular impacts in Pacific oyster, Crassostrea gigas

Recently, the toxic effects of tralopyril, as a new antifouling biocide, on aquatic organisms have aroused widespread attention about the potential toxicity. However, the mechanism of tralopyril on marine mollusks has not been elaborated clearly. In this study, the histological, biochemical and molecular impacts of tralopyril on adult Crassostrea gigas were investigated. The results indicated that the 96 h LC50 of tralopyril to adult Crassostrea gigas was 911 μg/L. After exposure to tralopyril (0, 40, 80 and 160 μg/L) for 6 days, the mantle mucus secretion coverage ratio of Crassostrea gigas was increased with a dose-dependent pattern. Catalase (CAT) activity was significantly increased, amylase (AMS) activity, acid phosphatase (ACP) activity and calcium ion (Ca²⁺) concentration significantly decreased. Meanwhile, integrated biomarker responses (IBR) index suggested that higher concentrations of tralopyril caused severer damage to Crassostrea gigas. In addition, the mRNA expression levels of biomineralization related genes in the mantle were significantly upregulated. Collectively, this study firstly revealed the histological, biochemical and molecular impacts of tralopyril exposure on adult Crassostrea gigas, which provided new insights for understanding the toxicity of tralopyril in marine mollusks.

Perspective on Dentoalveolar Manifestations Resulting From PHOSPHO1 Loss-of-Function: A Form of Pseudohypophosphatasia?

Mineralization of the skeleton occurs by several physicochemical and biochemical processes and mechanisms that facilitate the deposition of hydroxyapatite (HA) in specific areas of the extracellular matrix (ECM). Two key phosphatases, phosphatase, orphan 1 (PHOSPHO1) and tissue-non-specific alkaline phosphatase (TNAP), play complementary roles in the mineralization process. The actions of PHOSPHO1 on phosphocholine and phosphoethanolamine in matrix vesicles (MVs) produce inorganic phosphate (P_i) for the initiation of HA mineral formation within MVs. TNAP hydrolyzes adenosine triphosphate (ATP) and the mineralization inhibitor, inorganic pyrophosphate (PP_i), to generate P_i that is incorporated into MVs. Genetic mutations in the ALPL gene-encoding TNAP lead to hypophosphatasia (HPP), characterized by low circulating TNAP levels (ALP), rickets in children and/or osteomalacia in adults, and a spectrum of dentoalveolar defects, the most prevalent being lack of acellular cementum leading to premature tooth loss. Given that the skeletal manifestations of genetic ablation of the Phospho1 gene in mice resemble many of the manifestations of HPP, we propose that Phospho1 gene mutations may underlie some cases of "pseudo-HPP" where ALP may be normal to subnormal, but ALPL mutation(s) have not been identified. The goal of this perspective article is to compare and contrast the loss-of-function effects of TNAP and PHOSPHO1 on the dentoalveolar complex to predict the likely dental phenotype in humans that may result from PHOSPHO1 mutations. Potential cases of pseudo-HPP associated with PHOSPHO1 mutations may resist diagnosis, and the dental manifestations could be a key criterion for consideration.

Inflammation and Microcalcification: A Never-Ending Vicious Cycle in Atherosclerosis?

Inflammatory cells and cytokines are known for long to worsen the development of atherosclerotic plaques in mice, and intense efforts are today devoted to develop anti-inflammatory therapeutic strategies to slow down plaque development. Increasing data indicate that plaque inflammation is intimately associated with microcalcifications, which exert harmful effects eventually culminating with plaque rupture. In this review article, we will first introduce microcalcification location, detection, and effects in atherosclerotic plaques. Then, we will present the numerous data suggesting that inflammatory cells and molecules are responsible for the formation of microcalcifications and the articles showing that microcalcifications stimulate macrophages and smooth muscle cells to produce more pro-inflammatory cytokines. Finally, we will discuss the possibility that microcalcifications might stimulate smooth muscle cells to produce larger and more stable calcifications to stabilize plaques, to exit the vicious cycle associating inflammation and microcalcification in atherosclerotic plaques.

Phase I studies of the safety, tolerability, pharmacokinetics, and pharmacodynamics of DS-1211, a tissue-nonspecific alkaline phosphatase inhibitor

Tissue-nonspecific alkaline phosphatase (TNAP) hydrolyzes and inactivates inorganic pyrophosphate (PPi), a potent inhibitor of calcification; therefore, TNAP inhibition is a potential target to treat ectopic calcification. These two first-in-human studies evaluated safety, tolerability, pharmacokinetics (PKs), and pharmacodynamics (PDs) of single (SAD) and multiple-ascending doses (MAD) of DS-1211, a TNAP inhibitor. Healthy adults were randomized 6:2 to DS-1211 or placebo, eight subjects per dose cohort. SAD study subjects received one dose of DS-1211 (range, 3-3000 mg) or placebo, whereas MAD study subjects received DS-1211 (range, 10-300 mg) once daily, 150 mg twice daily (b.i.d.), or placebo for 10 days. Primary end points were safety and tolerability. PK and PD assessments included plasma concentrations of DS-1211, alkaline phosphatase (ALP) activity, and TNAP substrates (PPi, pyridoxal 5'-phosphate [PLP], and phosphoethanolamine [PEA]). A total of 56 (DS-1211: n = 42; placebo: n = 14) and 40 (DS-1211: n = 30; placebo: n = 10) subjects enrolled in the SAD and MAD studies, respectively. In both studies, adverse events were mild or moderate and did not increase with dose. PKs of DS-1211 were linear up to 100 mg administered as a single dose and 150 mg b.i.d. administered as a multiple-dose regimen. In multiple dosing, there was minimal accumulation of DS-1211. Increased DS-1211 exposure correlated with dose-dependent ALP inhibition and concomitant increases in PPi, PLP, and PEA. In two phase I studies, DS-1211 appeared safe and well-tolerated. Post-treatment PD assessments were consistent with exposure-dependent TNAP inhibition. These data support further evaluation of DS-1211 for ectopic calcification diseases.

TNAP as a therapeutic target for cardiovascular calcification: a discussion of its pleiotropic functions in the body

Cardiovascular calcification (CVC) is associated with increased morbidity and mortality. It develops in several diseases and locations, such as in the tunica intima in atherosclerosis plaques, in the tunica media in type 2 diabetes and chronic kidney disease, and in aortic valves. In spite of the wide occurrence of CVC and its detrimental effects on cardiovascular diseases (CVD), no treatment is yet available. Most of CVC involve mechanisms similar to those occurring during endochondral and/or intramembranous ossification. Logically, since tissue-nonspecific alkaline phosphatase (TNAP) is the key-enzyme responsible for skeletal/dental mineralization, it is a promising target to limit CVC. Tools have recently been developed to inhibit its activity and preclinical studies conducted in animal models of vascular calcification already provided promising results. Nevertheless, as its name indicates, TNAP is ubiquitous and recent data indicate that it dephosphorylates different substrates in vivo to participate in other important physiological functions besides mineralization. For instance, TNAP is involved in the metabolism of pyridoxal phosphate and the production of neurotransmitters. TNAP has also been described as an anti-inflammatory enzyme able to dephosphorylate adenosine nucleotides and lipopolysaccharide. A better understanding of the full spectrum of TNAP's functions is needed to better characterize the effects of TNAP inhibition in diseases associated with CVC. In this review, after a brief description of the different types of CVC, we describe the newly uncovered additional functions of TNAP and discuss the expected consequences of its systemic inhibition in vivo.

Effect of increasing mineralization on pre-osteoblast response to native collagen fibril scaffolds for bone tissue repair and regeneration

With limited availability of auto- and allografts, there is increasing demand for alternative bone repair and regeneration materials. Inspired by a mimetic approach, the utility of producing engineered native protein scaffolds is being increasingly realized, demonstrating the need for continued research in this field. In previous work, we detailed a process for producing mineralized collagen scaffolds using tendon to create collagen templates of highly aligned, natively crosslinked collagen fibrils. The process produced mineral phase closely matching that of native bone, and integration of mineral with the collagen template was demonstrated to be easily controlled, allowing scaffolds to be mechanically tuned. In the current study, we have extended this work to investigate how variation in the mineralization level of these scaffolds affects the osteogenic response of pre-osteoblastic cells. Scaffolds were produced under three treatment groups, where collagen templates underwent 0, 5, or 20 mineralization cycles. Scaffolds in each treatment group were cultured with MC3T3-E1 cells for 1, 7, or 14 days. Morphologic assessment under SEM indicated decreased attachment to the mineralized scaffolds, supported by DNA results showing a significant drop between culture days 1 and 7 for mineralized scaffolds only. For adherent cells, increasing scaffold mineralization also delayed cell spreading. While mineralization presented a barrier to cell coverage of scaffolds, it increased osteogenic activity, with cells on the mineralized scaffolds showing significantly greater alkaline phosphatase activity and osteocalcin production. Understanding how increasing collagen mineralization effects pre-osteoblast function may enable design of more advanced mineralized collagen scaffolds for bone repair and regeneration.

Positive Association Between Serum Alkaline Phosphatase and First Stroke in Hypertensive Adults

The relation of alkaline phosphatase (ALP) with stroke risk remains uncertain. We aimed to examine the association between serum ALP and the risk of first stroke, and explore the possible effect modifiers in the association, among adults with hypertension. A total of 19,747 participants with baseline ALP measurements and without liver disease at baseline from the China Stroke Primary Prevention Trial (CSPPT) were included. The primary outcome was a first stroke. Over a median follow-up of 4.5 years, there was a positive association between serum ALP levels and the risk of first stroke (per SD increment, adjusted HR, 1.10; 95%CI: 1.01, 1.20). When serum ALP was evaluated as quartiles, a significantly higher risk of first stroke was observed in those in quartile 2–4 (ALP ≥79 IU/L; adjusted HR, 1.38; 95% CI: 1.11, 1.71), compared with participants in quartile 1 (ALP <79 IU/L). Similar results were found for first ischemic or hemorrhagic stroke. Similar findings were also found in those with a normal range of baseline ALP levels (20–140 IU/L) (per SD increment, adjusted HR, 1.15; 95%CI: 1.05, 1.27). None of the variables, including sex, age, body mass index, smoking, alcohol drinking, blood pressure, total cholesterol, fasting glucose levels at baseline, and blood pressure levels during the treatment period, significantly modified the association. In summary, our study suggests that higher serum ALP levels, even in normal range, were significantly related to higher risk of first stroke among Chinese hypertensive adults.

The phytochemical plumbagin reciprocally modulates osteoblasts and osteoclasts

Bone metabolism is essential for maintaining bone mineral density and bone strength through a balance between bone formation and bone resorption. Bone formation is associated with osteoblast activity whereas bone resorption is linked to osteoclast differentiation. Osteoblast progenitors give rise to the formation of mature osteoblasts whereas monocytes are the precursors for multi-nucleated osteoclasts. Chronic inflammation, auto-inflammation, hormonal changes or adiposity have the potential to disturb the balance between bone formation and bone loss. Several plant-derived components are described to modulate bone metabolism and alleviate osteoporosis by enhancing bone formation and inhibiting bone resorption. The plant-derived naphthoquinone plumbagin is a bioactive compound that can be isolated from the roots of the Plumbago genus. It has been used as traditional medicine for treating infectious diseases, rheumatoid arthritis and dermatological diseases. Reportedly, plumbagin exerts its biological activities primarily through induction of reactive oxygen species and triggers osteoblast-mediated bone formation. It is plausible that plumbagin's reciprocal actions - inhibiting or inducing death in osteoclasts but promoting survival or growth of osteoblasts - are a function of the synergy with bone-metabolizing hormones calcitonin, Parathormone and vitamin D. Herein, we develop a framework for plausible molecular modus operandi of plumbagin in bone metabolism.

Pathogenesis of calcium pyrophosphate deposition disease

Calcium pyrophosphate deposition disease is defined by the presence of calcium pyrophosphate (CPP) crystals in articular cartilage and is the fourth most common type of arthritis in adults. Despite its high prevalence, the etiology of CPPD disease remains unclear and no specific therapies currently exist. It has been known for several decades that abnormalities of cartilage pyrophosphate metabolism are common in patients with CPPD disease, and this classic work will be reviewed here. Recent studies of rare familial forms of CPPD disease have provided additional novel information about its pathophysiology. This work suggests that CPPD disease occurs through at least two unique and potentially intertwined biomolecular pathways. We are hopeful that a detailed understanding of the components and regulation of these pathways will lead to improved therapies for this common disease.

The Physiological and Pathological Role of Tissue Nonspecific Alkaline Phosphatase beyond Mineralization

Tissue-nonspecific alkaline phosphatase (TNAP) is a key enzyme responsible for skeletal tissue mineralization. It is involved in the dephosphorylation of various physiological substrates, and has vital physiological functions, including extra-skeletal functions, such as neuronal development, detoxification of lipopolysaccharide (LPS), an anti-inflammatory role, bile pH regulation, and the maintenance of the blood brain barrier (BBB). TNAP is also implicated in ectopic pathological calcification of soft tissues, especially the vasculature. Although it is the crucial enzyme in mineralization of skeletal and dental tissues, it is a logical clinical target to attenuate vascular calcification. Various tools and studies have been developed to inhibit its activity to arrest soft tissue mineralization. However, we should not neglect its other physiological functions prior to therapies targeting TNAP. Therefore, a better understanding into the mechanisms mediated by TNAP is needed for minimizing off targeted effects and aid in the betterment of various pathological scenarios. In this review, we have discussed the mechanism of mineralization and functions of TNAP beyond its primary role of hard tissue mineralization.

Pyrophosphate inhibits periodontal ligament stem cell differentiation and mineralization through MAPK signaling pathways

BACKGROUND AND OBJECTIVE

Periodontal ligament stem cells (PDLSCs) are the primary cell source for the regeneration and remodeling of periodontal ligament (PDL). It is crucial to prevent PDLSCs from mineralization when using the PDLSCs for PDL regeneration. At present, little is known about how to inhibit PDLSC mineralization. This study investigates the effects of pyrophosphate (PPi) on inhibiting PDLSC osteogenic differentiation and mineralization as well as the underlying mechanism.

MATERIALS AND METHODS

Human PDLSCs were cultured in an osteogenic differentiation medium with different PPi concentrations (0, 10, or 100 μM). The effects of PPi on osteogenic differentiation were assessed by ALP activity and the expressions of osteogenic related proteins (OPN, RUNX2, OSX, and DMP1). The mineralization formation was detected by alizarin red staining. The activation of MAPK signaling pathways (ERK1/2, JNK, and p38) was determined by western blotting and pathway blockade assays. The gene expressions of PPi's regulators (Ank, Enpp1, and Alpl) were assessed by real-time PCR.

RESULTS

Both low and high concentrations (10 μM and 100 μM) of PPi inhibited the mineralization of PDLSCs. The addition of PPi (10 μM or 100 μM) decreased the ALP activity of the PDLSCs to approximately two-thirds of the control group on day 3. PPi reduced the expressions of RUNX2, OSX, and DMP1 on days 7, 14, and 21, while it increased the expression of OPN at the three time points. PPi enhanced the phosphorylation of MAPK pathways, and the application of corresponding MAPK pathway inhibitors reversed the osteogenic inhibition effects of PPi.

CONCLUSION

PPi inhibits the osteogenic differentiation and mineralization of PDLSCs in vitro through activating ERK1/2, JNK, and p38 signaling pathways.

Identifying critical genes associated with aneurysmal subarachnoid hemorrhage by weighted gene co-expression network analysis

Aneurysmal subarachnoid hemorrhage (aSAH) is a life-threatening medical condition with a high mortality and disability rate. aSAH has an unclear pathogenesis, and limited treatment options are available. Here, we aimed to identify critical genes involved in aSAH pathogenesis using peripheral blood gene expression data of 43 patients with aSAH due to ruptured intracranial aneurysms and 18 controls with headache, downloaded from Gene Expression Omnibus. These data were used to construct a co-expression network using weighted gene co-expression network analysis (WGCNA). The biological functions of the hub genes were explored, and critical genes were selected by combining with differentially expressed genes analysis. Fourteen modules were identified by WGCNA. Among those modules, red, blue, brown and cyan modules were closely associated with aSAH. Moreover, 364 hub genes in the significant modules were found to play important roles in aSAH. Biological function analysis suggested that protein biosynthesis-related processes and inflammatory responses-related processes were involved in the pathology of aSAH pathology. Combined with differentially expressed genes analysis and validation in 35 clinical samples, seven gene (CD27, ANXA3, ACSL1, PGLYRP1, ALPL, ARG1, and TPST1) were identified as potential biomarkers for aSAH, and three genes (ANXA3, ALPL, and ARG1) were changed with disease development, that may provide new insights into potential molecular mechanisms for aSAH.

Chronic Kidney Disease-Induced Arterial Media Calcification in Rats Prevented by Tissue Non-Specific Alkaline Phosphatase Substrate Supplementation Rather Than Inhibition of the Enzyme

Patients with chronic kidney disease (CKD) suffer from arterial media calcification and a disturbed bone metabolism. Tissue-nonspecific alkaline phosphatase (TNAP) hydrolyzes the calcification inhibitor pyrophosphate (PPi) into inorganic phosphate (Pi) and thereby stimulates arterial media calcification as well as physiological bone mineralization. This study investigates whether the TNAP inhibitor SBI-425, PPi or the combination of both inhibit arterial media calcification in an 0.75% adenine rat model of CKD. Treatments started with the induction of CKD, including (i) rats with normal renal function (control diet) treated with vehicle and CKD rats treated with either (ii) vehicle, (iii) 10 mg/kg/day SBI-425, (iv) 120 µmol/kg/day PPi and (v) 120 µmol/kg/day PPi and 10 mg/kg/day SBI-425. All CKD groups developed a stable chronic renal failure reflected by hyperphosphatemia, hypocalcemia and high serum creatinine levels. CKD induced arterial media calcification and bone metabolic defects. All treatments, except for SBI-425 alone, blocked CKD-related arterial media calcification. More important, SBI-425 alone and in combination with PPi increased osteoid area pointing to a less efficient bone mineralization. Clearly, potential side effects on bone mineralization will need to be assessed in any clinical trial aimed at modifying the Pi/PPi ratio in CKD patients who already suffer from a compromised bone status.