Mechanism Of Calcification Research Articles

Klotho-FGF23, Cardiovascular Disease, and Vascular Calcification: Black or White?

Patients affected by Chronic Kidney Disease and Mineral Bone Disorder (CKD-MBD) have a high risk of cardiovascular (CV) mortality that is poorly explained by traditional risk factors. The newest medical treatments for CKD-MBD have been associated with encouraging, but still inconsistent, improvement in CV disease complications and patient survival. A better understanding of the biomarkers and mechanisms of left ventricular hypertrophy (LVH), atherosclerosis, and vascular calcification (VC) may help with diagnosis and treatment of the organ damage that occurs secondary to CKD-MBD, thus improving survival. Recent insights about fibroblast growth factor-23 (FGF23) and its co-receptor, Klotho, have led to marked advancement in interpreting data on vascular aging and CKDMBD. This review will discuss the current experimental and clinical evidence regarding FGF23 and Klotho, with a particular focus on their roles in LVH, atherosclerosis, and VC.

Mechanisms of Arterial Calcification: The Role of Matrix Vesicles

Vascular calcification is related to vascular diseases, for example, atherosclerosis, and its comorbidities, such as diabetes and chronic kidney disease. In each condition, a distinctive histological pattern can be recognised that may influence technical choices, possible intra-operative complications, and procedure outcomes, no matter if the intervention is performed by open or endovascular means. This review considers the classification and initiating mechanisms of vascular calcification. Dystrophic and metastatic calcifications, Monckeberg's calcification, and genetic forms are firstly outlined, followed by their alleged initiation mechanisms; these include (a) ineffective macrophage efferocytosis; (b) ectopic osteogenesis driven by modified resident or circulating osteoprogenitors. As in physiological bio-mineralisation, active calcification starts with the deposition of cell derived matrix vesicles into the extracellular matrix. To substantiate this belief, an in depth ultra-structural documentation of hydroxyapatite crystal deposition on such vesicles is provided in an ex-vivo human vascular cell model. Revealing the vesicle composition and phenotype in normal and pathological vascular conditions will be essential for the development of new therapeutic strategies, in order to prevent and treat vascular calcification.

Regulation of calcification in human aortic smooth muscle cells infected with high-glucose-treated Porphyromonas gingivalis.

Porphyromonas (P.) gingivalis infection leading to the periodontitis has been associated with the development of systemic diseases, including cardiovascular diseases and diabetes. However, the effect of a high concentration of glucose (HG) on the invasion efficiency of P. gingivalis and the consequent modulation of pathogenesis in vascular cells, especially in the vascular smooth muscle cells (VSMCs), remains unclear. Hence, the aim of this study was to investigate whether treating P. gingivalis with HG could change its invasion capability and result in VSMC calcification and the underlying mechanism. Human aortic SMCs (HASMCs) and P. gingivalis strain CCUG25226 were used in this study. We found that HGPg infection of HASMCs could initiate the HASMC calcification by stimulating the autocrine regulation of bone morphogenetic protein (BMP) 4 in HASMCs. The upregulation of BMP4 expression in HASMCs was mediated by toll-like receptor 4 and ERK1/2-p38 signaling after P. gingivalis infection. Moreover, the autocrine action of BMP4 in HGPg infection-initiated HASMC calcification upregulated BMP4-specific downstream smad1/5/8-runx2 signaling to increase the expressions of bone-related matrix proteins, that is, osteopontin, osteocalcin, and alkaline phosphatase. This study elucidates the detailed mechanism of HGPg infection-initiated calcification of HASMCs and indicates a possible therapeutic role of BMP4 in P. gingivalis infection-associated vascular calcification.

Chronic Kidney Disease Circulating Calciprotein Particles and Extracellular Vesicles Promote Vascular Calcification: A Role for GRP (Gla-Rich Protein).

Inhibition of mineral crystal formation is a crucial step in ectopic calcification. Serum calciprotein particles (CPPs) have been linked to chronic kidney disease (CKD) calcification propensity, but additional knowledge is required to understand their function, assemblage, and composition. The role of other circulating nanostructures, such as extracellular vesicles (EVs) in vascular calcification is currently unknown. Here, we investigated the association of GRP (Gla-rich protein) with circulating CPP and EVs and the role of CKD CPPs and EVs in vascular calcification. Biological CPPs and EVs were isolated from healthy and CKD patients and comparatively characterized using ultrastructural, analytic, molecular, and immuno-based techniques. Our results show that GRP is a constitutive component of circulating CPPs and EVs. CKD stage 5 serum CPPs and EVs are characterized by lower levels of fetuin-A and GRP, and CPPs CKD stage 5 have increased mineral maturation, resembling secondary CPP particles. Vascular smooth muscle cell calcification assays reveal that CPPs CKD stage 5 and EVs CKD stage 5 are taken up by vascular smooth muscle cells and induce vascular calcification by promoting cell osteochondrogenic differentiation and inflammation. These effects were rescued by incubation of CPPs CKD stage 5 with γ-carboxylated GRP. In vitro, formation and maturation of basic calcium phosphate crystals was highly reduced in the presence of γ-carboxylated GRP, fetuin-A, and MGP (matrix gla protein), and a similar antimineralization system was identified in vivo. Uremic CPPs and EVs are important players in the mechanisms of widespread calcification in CKD. We propose a major role for cGRP as inhibitory factor to prevent calcification at systemic and tissue levels.

Calcification of the heart arteries in coronary athero­sclerosis

The review shows the participation of smooth muscle cells, macrophages, bone marrow stem cells in the calcification of arteries, the effect of microcalcifications and diffuse calcium accumulation on the vulnerability of plaque. The relationship between calcification of coronary arteries and such major factors of cardiovascular risk as age, hypercholesterolemia, diabetes mellitus has been clarified. Data on the effect of inflammation on calcium deposition in the vascular wall and the effect of statins on the calcification of atherosclerotic plaques are presented. Assessment of the presence and severity of vascular calcification can significantly improve the accuracy of the diagnosis of atherosclerosis and the prognosis of its course. Calcification mechanisms may be targets for pharmacological interventions, having significant impact on the development and progression of atherosclerosis.

Pathogenesis and Management of Vascular Calcification in Patients with End-Stage Renal Disease.

Vascular calcification is common in patients with end-stage renal disease (ESRD). In addition to traditional cardiovascular risk factors, ESRD patients also have a number of nontraditional cardiovascular risk factors that may play an important role in the pathogenesis of vascular calcification. The transformation of vascular smooth muscle cells into osteoblast-like cells may be a key element in the pathogenesis of vascular calcification in the presence of calcium and phosphate deposition due to abnormal bone metabolism and impaired renal excretion. Vascular calcification causes increased arterial stiffness, left ventricular hypertrophy, decreased coronary artery perfusion, myocardial ischemia, and increased cardiovascular morbidity and mortality. Although current treatment strategies focus on correcting abnormal calcium, phosphate, parathyroid hormone, or vitamin D levels in ESRD patients, a better understanding of the mechanisms of abnormal tissue calcification may lead to the development of new therapeutic agents that are capable of reducing vascular calcification and improving the cardiovascular outcome of ESRD patients. This review summarizes the pathogenesis and management of vascular calcification in ESRD patients.

Utility of coronary calcium score in women

Coronary artery disease is a major cause of death and disability among women, worldwide, particularly during the postmenopausal state, with the caveat that their presenting symptoms are atypical compared to men. Also, there is conflicting data regarding the ideal method to determine their risk, particularly for primary prevention. During this review, we sought to determine the utility of the coronary calcium score for assessing such risk in asymptomatic women, by reviewing the most representative current data and analyzing additional studies to help improve the understanding of mechanisms of coronary artery calcification and determine better strategies of prevention and treatment in women with a positive CCS.

Microcalcifications, Their Genesis, Growth, and Biomechanical Stability in Fibrous Cap Rupture.

For many decades, cardiovascular calcification has been considered as a passive process, accompanying atheroma progression, correlated with plaque burden, and apparently without a major role on plaque vulnerability. Clinical and pathological analyses have previously focused on the total amount of calcification (calcified area in a whole atheroma cross section) and whether more calcification means higher risk of plaque rupture or not. However, this paradigm has been changing in the last decade or so. Recent research has focused on the presence of microcalcifications (μCalcs) in the atheroma and more importantly on whether clusters of μCalcs are located in the cap of the atheroma. While the vast majority of μCalcs are found in the lipid pool or necrotic core, they are inconsequential to vulnerable plaque. Nevertheless, it has been shown that μCalcs located within the fibrous cap could be numerous and that they behave as an intensifier of the background circumferential stress in the cap. It is now known that such intensifying effect depends on the size and shape of the μCalc as well as the proximity between two or more μCalcs. If μCalcs are located in caps with very low background stress, the increase in stress concentration may not be sufficient to reach the rupture threshold. However, the presence of μCalc(s) in the cap with a background stress of about one fifth to one half the rupture threshold (a stable plaque) will produce a significant increase in local stress, which may exceed the cap rupture threshold and thus transform a non-vulnerable plaque into a vulnerable one. Also, the classic view that treats cardiovascular calcification as a passive process has been challenged, and emerging data suggest that cardiovascular calcification may encompass both passive and active processes. The passive calcification process comprises biochemical factors, specifically circulating nucleating complexes, which would lead to calcification of the atheroma. The active mechanism of atherosclerotic calcification is a cell-mediated process via cell death of macrophages and smooth muscle cells (SMCs) and/or the release of matrix vesicles by SMCs.

Reduced calcification and osteogenic features in advanced atherosclerotic plaques of mice with macrophage-specific loss of TRPC3

Background and aimsRecent in vitro studies have showed that in macrophages, deletion of the non-selective Ca2+-permeable channel TRPC3 impairs expression of the osteogenic protein BMP-2. The pathophysiological relevance of this effect in atherosclerotic plaque calcification remains to be determined. MethodsWe used Ldlr−/− mice with macrophage-specific loss of TRPC3 (MacTrpc3−/−/Ldlr−/−) to examine the effect of macrophage Trpc3 on plaque calcification and osteogenic features in advanced atherosclerosis. ResultsAfter 25 weeks on high fat diet, aortic root plaques in MacTrpc3−/−/Ldlr−/− mice showed reduced size, lipid and macrophage content compared to controls. Plaque calcification was decreased in MacTrpc3−/−/Ldlr−/− mice, and this was accompanied by marked reduction in BMP-2, Runx-2 and phospho-SMAD1/5 contents within macrophage-rich areas. Expression of Bmp-2 and Runx-2 was also reduced in bone marrow-derived macrophages from MacTrpc3−/−/Ldlr−/− mice. ConclusionsThese findings show that, in advanced atherosclerosis, selective deletion of TRPC3 in macrophages favors plaque regression and impairs the activity of a novel macrophage-associated, BMP-2-dependent mechanism of calcification.

A Novel Mechanism for Atherosclerotic Calcification: Potential Resolution of the Oxidation Paradox.

In this study, we tested the hypothesis that lipid peroxide-derived dicarboxylic acids (DCAs), by virtue of their ability to bind to calcium (Ca), might be involved in atherosclerotic calcification. We determined the ability of azelaic acid (AzA) to promote calcification in human aortic smooth muscle cells (HASMCs), identified AzA in human calcified atherosclerotic lesions, and compared its levels with control and noncalcified atherosclerotic lesions. HASMCs efficiently converted 9-oxononanoic acid (ONA), a lipid peroxide-derived monocarboxylic aldehyde, to AzA. In vitro incubations of AzA micelles with HASMC resulted in the formation of Ca deposits, which contained AzA. Liquid chromatography-mass spectrometry analysis of human control uninvolved artery, noncalcified, and calcified lesions showed significant increase of AzA in calcified lesions compared with noncalcified and control tissues. Calcified mouse atherosclerotic lesions also showed substantial presence of AzA in Ca complexes. This study identifies a DCA, AzA, as an integral part of the Ca complex. The study also demonstrates the conversion of a lipid peroxidation product, ONA, as a potential source of AzA, and establishes the presence of AzA in calcified materials isolated from human and mouse lesions. The presence of AzA as a Ca sequestering agent in atherosclerotic lesions (i) might indicate participation of oxidized low-density lipoprotein (Ox-LDL) derived products in calcification, (ii) explain the potential correlation between calcification and overall plaque burden (as Ox-LDL has been suggested to be involved in atherogenesis), (iii) could contribute to plaque stabilization via its anti-inflammatory actions, and (iv) might explain why antioxidants failed to affect atherosclerosis in clinical studies. Antioxid. Redox Signal. 29, 471-483.

Multidisciplinary Approach to Understand Medial Arterial Calcification.

Vascular calcification significantly increases morbidity in life-threatening diseases, and no treatments are available because of lack of understanding of the underlying molecular mechanism. Here, we study the physicochemical details of mineral nucleation and growth in an animal model that faithfully recapitulates medial arterial calcification in humans, to understand how pathological calcification is initiated on the vascular extracellular matrix. MGP (matrix Gla protein) is a potent mineralization inhibitor. We study the evolution of medial calcification in MGP-deficient mice over the course of 5 weeks using a combination of material science techniques and find that mineral composition and crystallinity evolve over time and space. We show that calcium is adsorbed first and then amorphous calcium phosphate and octacalcium phosphate forms, which then transform into hydroxyapatite and carbonated apatite. These events are repeated after each nucleation event, providing a snapshot of the overall mineral evolution at each time point analyzed. Our results show that an interdisciplinary approach combining animal models and materials science can provide insights into the mechanism of vascular calcification and suggest the importance of analyzing mineral phases, rather than just overall mineralization extent, to diagnose and possibly prevent disease development.

Coral calcification mechanisms facilitate adaptive responses to ocean acidification.

Ocean acidification (OA) is a pressing threat to reef-building corals, but it remains poorly understood how coral calcification is inhibited by OA and whether corals could acclimatize and/or adapt to OA. Using a novel geochemical approach, we reconstructed the carbonate chemistry of the calcifying fluid in two coral species using both a pH and dissolved inorganic carbon (DIC) proxy (δ11B and B/Ca, respectively). To address the potential for adaptive responses, both species were collected from two sites spanning a natural gradient in seawater pH and temperature, and then subjected to three pHT levels (8.04, 7.88, 7.71) crossed by two temperatures (control, +1.5°C) for 14 weeks. Corals from the site with naturally lower seawater pH calcified faster and maintained growth better under simulated OA than corals from the higher-pH site. This ability was consistently linked to higher pH yet lower DIC values in the calcifying fluid, suggesting that these differences are the result of long-term acclimatization and/or local adaptation to naturally lower seawater pH. Nevertheless, all corals elevated both pH and DIC significantly over seawater values, even under OA. This implies that high pH upregulation combined with moderate levels of DIC upregulation promote resistance and adaptive responses of coral calcification to OA.

Pregnancy history, coronary artery calcification and bone mineral density in menopausal women

Objective: This study examined relationships, by pregnancy histories, between bone mineral density (BMD) and coronary artery calcification (CAC) in postmenopausal women.Methods: Forty women identified from their medical record as having pre-eclampsia (PE) were age/parity-matched with 40 women having a normotensive pregnancy (NP). Vertebral (T4–9) BMD and CAC were assessed by quantitative computed tomography in 73 (37 with PE and 36 with NP) of the 80 women. Analyses included linear regression using generalized estimating equations.Results: Women averaged 59 years of age and 35 years from the index pregnancy. There were no significant differences in cortical, trabecular or central BMD between groups. CAC was significantly greater in the PE group (p = 0.026). In multivariable analysis, CAC was positively associated with cortical BMD (p = 0.001) and negatively associated with central BMD (p = 0.036). There was a borderline difference in the association between CAC and central BMD by pregnancy history (interaction, p = 0.057).Conclusions: Although CAC was greater in women with a history of PE, vertebral BMD did not differ between groups. However, both cortical and central BMD were associated with CAC. The central BMD association was marginally different by pregnancy history, suggesting perhaps differences in underlying mechanisms of soft tissue calcification.

Mussel larvae modify calcifying fluid carbonate chemistry to promote calcification

Understanding mollusk calcification sensitivity to ocean acidification (OA) requires a better knowledge of calcification mechanisms. Especially in rapidly calcifying larval stages, mechanisms of shell formation are largely unexplored—yet these are the most vulnerable life stages. Here we find rapid generation of crystalline shell material in mussel larvae. We find no evidence for intracellular CaCO3 formation, indicating that mineral formation could be constrained to the calcifying space beneath the shell. Using microelectrodes we show that larvae can increase pH and [CO32−] beneath the growing shell, leading to a ~1.5-fold elevation in calcium carbonate saturation state (Ωarag). Larvae exposed to OA exhibit a drop in pH, [CO32−] and Ωarag at the site of calcification, which correlates with decreased shell growth, and, eventually, shell dissolution. Our findings help explain why bivalve larvae can form shells under moderate acidification scenarios and provide a direct link between ocean carbonate chemistry and larval calcification rate.

Ultrastructural, Elemental and Mineralogical Analysis of Vascular Calcification in Atherosclerosis

Over the past few decades, remarkable progress has been achieved in terms of understanding the molecular and cellular mechanisms of atherosclerotic vascular calcification and the important role of matrix vesicles in initiating and propagating pathologic tissue mineralization has been widely recognized. Despite these recent advances, however, no definitive data are currently available regarding the texture and composition of the minerals that grow in the vessel wall during the course of the disease. Using different electron microscopy imaging and analysis, we demonstrate that vascular cells can produce and secrete more than one type of matrix vesicles which act as sites for initial mineral deposition independently of their structural features. Our results reveal that apatite formation in the atherosclerotic lesions of the human aorta occur through the deposition of amorphous calcium phosphate that matures over time, transforms into crystalline hydroxyapatite, and radiates towards the lumen of the vesicles, finally forming the calcified spherules. Elemental and mineralogical analyses also demonstrate that the presence of mature and stable amorphous calcium phosphate deposits in the affected tissues is linked to the incorporation of magnesium, which probably delay the conversion to the crystalline phase. Though more rarely, the presence of calcium oxalate crystals has been also documented.

Osteocalcin, Vascular Calcification, and Atherosclerosis: A Systematic Review and Meta-analysis.

Osteocalcin (OC) is an intriguing hormone, concomitantly being the most abundant non-collagenous peptide found in the mineralized matrix of bone, and expanding the endocrine function of the skeleton with far-reaching extra-osseous effects. A new line of enquiry between OC and vascular calcification has emerged in response to observations that the mechanism of vascular calcification resembles that of bone mineralisation. To date, studies have reported mixed results. This systematic review and meta-analysis aimed to identify any association between OC and vascular calcification and atherosclerosis. Databases were searched for original, peer reviewed human studies. A total of 1,453 articles were retrieved, of which 46 met the eligibility criteria. Overall 26 positive, 17 negative, and 29 neutral relationships were reported for assessments between OC (either concentration in blood, presence of OC-positive cells, or histological staining for OC) and extent of calcification or atherosclerosis. Studies that measured OC-positive cells or histological staining for OC reported positive relationships (11 studies). A higher percentage of Asian studies found a negative relationship (36%) in contrast to European studies (6%). Studies examining carboxylated and undercarboxylated forms of OC in the blood failed to report consistent results. The meta-analysis found no significant difference between OC concentration in the blood between patients with "atherosclerosis" and control (p = 0.13, n = 1,197). No definitive association was determined between OC and vascular calcification or atherosclerosis; however, the presence of OC-positive cells and histological staining had a consistent positive correlation with calcification or atherosclerosis. The review highlighted several themes, which may influence OC within differing populations leading to inconclusive results. Large, longitudinal studies are required to further current understanding of the clinical relevance of OC in vascular calcification and atherosclerosis.

Skeletal growth controls on Mg/Ca and P/Ca ratios in tropical Eastern Pacific rhodoliths (coralline red algae)

The Mg/Ca ratios of non-geniculate coralline red algae (CA) are often assumed to be solely dependent on the sea surface temperature (SST) in which they grow, suggesting that they are ideal proxies for SST reconstruction. Mg/Ca ratio cyclicity is also commonly used as a marker for annual growth band identification in many CA species. However, other controls on elemental uptake such as light, calcification mechanisms, and vital effects may control elemental ratios (e.g. Mg/Ca and P/Ca) in certain genera or species of CA, thus complicating the use of Mg/Ca and P/Ca ratios as a proxy source for SST and paleo-environmental reconstructions. Here we present evidence showing that the Mg/Ca and P/Ca ratio cyclicity in unattached living tropical Lithothamnion sp. (n=8) rhodoliths correlate >90% to the number of sub-annual growth bands (n=1 to 20) formed during a 172-day controlled growth experiment and not to temperature or other environmental conditions (e.g. salinity, pH, etc.). This pattern is also observed in the wild, pre-experimental growth further supporting that the bands are not annual. The Mg/Caalga (R2=0.67; p-value=0.013; n=8) and P/Caalga (R2=0.64; p-value=0.018; n=8) significantly correlate to skeletal extension during the experiment. This work has implications for trace elemental proxy development using CA as well as the influence of skeletal extension on elemental incorporation in biogenic carbonates, particularly rhodoliths of Lithothamnion sp. from the Gulf of Panama, Panama.

Rigor and Reproducibility in Analysis of Vascular Calcification.

Clinical and preclinical studies of cardiovascular calcification often require interpretation of images from histopathology, computed tomography, intravascular ultrasound, and positron emission tomography. To avoid potential pitfalls in biological inferences, investigators should know what happens to data in image processing algorithms, the limitations of cross-sectional images in studying mechanostability, and how smoothing algorithms can mask partial-volume artifacts in positron emission tomography. Years ago, a head-on collision sent a motorcyclist to intensive care with multiple limb fractures. A cardiologist was paged to evaluate the unconscious patient for a dangerously low value of cardiac index, suggesting severe cardiac injury. On evaluation, pulse, blood pressure, and cardiac output were normal despite the extremely low cardiac index. How could that be? It turned out that this low value was the result of a common error: failure to scrutinize adjustments in processed data. Cardiac index is a type of processed data, which is derived from cardiac output divided by body surface area, which is, in turn, derived from height and weight. On assessing this adjustment, the cardiologist found that the patient’s weight included the casts on his arms and leg. Although it is obvious that casts do not require perfusion, this is an example of blindly following protocol, in this case resulting in a gross overestimate of weight, overestimate of body surface area, and underestimate of cardiac index. The moral of the story is that blind adherence to adjustment protocols may cause clinical errors. Does this happen in research? Corrections, adjustments, and technical limitations are common in imaging of preclinical and clinical vascular calcification, such as x-ray computed tomography (CT), intravascular ultrasound (IVUS), and, fused positron emission tomography (PET)-CT using the bone-seeking 18F-fluoride PET tracer. There is growing interest in using such imaging methods to infer molecular and cellular mechanisms of vascular calcification. However, colleagues …

Relationship Between Calcium-phosphorous Product, Native and Bioprosthetic Mitral Valve Calcifications

Calcification is a common cause of failure of natural and bioprosthetic valves (BPV). Prior research on patients with chronic kidney disease identified increased calcium-phosphorus (Ca-P) product as a risk factor for both arterial and valvular calcifications, an aspect not thoroughly investigated in general population. The aims of our study were to analyse the functional impact of native and bioprosthetic mitral valve (MV) calcification detected on cardiac computed tomography angiography (CCTA), to evaluate risk factors and to assess potential differences from a morphological and chemical point of view between BPV and native MV calcification. The authors performed a retrospective study on 270 patients who underwent CCTA for suspected coronary artery disease, 225 patients with no history of MV replacement and 45 patients with bioprosthetic MV. Mitral leaflet calcification (MLC) was registered in 21 (9.33%) and mitral annular calcification (MAC) in 27 (12%) of the 225 patients suspected for CVD. Echocardiography identified MV sclerosis in 20 cases (8.89%) and MV stenosis in 12 cases (5.33%) with MLC and/or MAC. In the BPV group, 13 patients (28.89%) presented visible BPV calcification associated to echocardiographic regurgitation in 3 (30.77%) cases and higher mean transvalvular gradients. Increased Ca-P product and diabetes mellitus proved to be risk factors for both native and BPV calcification and time since surgery only for BPV calcification. Native and BPV calcification are associated to valve dysfunction and share structural characteristics, thus indicating similar calcification mechanisms. Good glycaemic control in diabetic patients and careful administration of bisphosphonates, calcium and vitamin D supplements are mandatory especially in patients with BPV in order to prevent valve dysfunction due to calcification.

Osteoblastic differentiation and cell calcification of adamantinomatous craniopharyngioma induced by bone morphogenetic protein-2.

The calcification of adamantinomatous craniopharyngioma (ACP) often creates difficulties for surgical therapy. Nevertheless, the mechanism of ACP calcification is unclear. Our previous studies demonstrated that osteoblastic factors might play important roles in ACP calcification. We examined the effects of recombinant human Bmp2 on ACP cell differentiation by testing osteoblastic proteins and calcium deposition. The expression of osteoblastic factors including osteopontin (OPN), Runx2, and osterix in Bmp2-treated ACP cells was examined by western blot and/or real time PCR. ALP activity and calcium deposition after Bmp2 induction were also tested. Bmp2 significantly amplified the expression of Runx2, Osterix and OPN, as well as ALP activity. Both of these effects could be repressed by noggin treatment. Bmp2 also significantly induced the calcification of ACP, and noggin inhibited this calcium deposition. Our study demonstrated for the first time that ACP cells could differentiate into an osteoblastic lineage via induction by Bmp2. The mechanism of ACP calcification likely involves osteoblastic differentiation modulated by Bmp2. Further studies targeting Bmp2 cascades could result in novel therapeutic interventions for recurrent ACP.