A primary goal of bone research is to understand the mechanism(s) by which mechanical forces dictate the cellular and metabolic activities of osteoblasts, the boneforming cells. Several studies indicate that osteblastic cells respond to physical loading by transducing signals that alter gene expression patterns. Accumulated data have documented the fundamental role of the osteoblastspecific transcription factor Cbfa1 (core-binding factor) in osteoblast differentiation and function. Here, we demonstrate that low level mechanical deformation (stretching) of human osteoblastic cells directly up-regulates the expression and DNA binding activity of Cbfa1. This effect seems to be fine tuned by stretch-triggered induction of distinct mitogen-activated protein kinase cascades. Our novel finding that activated extracellular signal-regulated kinase mitogen-activated protein kinase physically interacts and phosphorylates endogenous Cbfa1 in vivo (ultimately potentiating this transcription factor) provides a molecular link between mechanostressing and stimulation of osteoblast differentiation. Elucidation of the specific modifiers and cofactors that operate in this mechanotranscription circuitry will contribute to a better understanding of mechanical load-induced bone formation which may set the basis for nonpharmacological intervention in bone loss pathologies.Mechanical stress has been long recognized to be an important regulatory factor in bone homeostasis and a determinant of skeletal morphology during development and in postnatal life (1). Given its influence on and interactions with all other modulators of bone growth, mineralization, and remodeling, there is great interest in understanding the effect of mechanical loading on osteoblast differentiation and function. Despite extensive investigations, information regarding the precise molecular events that govern transformation of mechanical signals into biochemical responses culminating in genetic reprograming of bone cells still remains sparse and inconsistent.The osteoblast is the bone-forming cell that originates from mesenchymal stem cells. A "master" regulator of osteoblast differentiation is the transcription factor Cbfa1 (core-binding factor), a member of the runt homology family of transcription factors (2). Cbfa1 binds to the osteoblast-specific cis-acting element 2 (OSE2) 1 (3), which is found in the promoter regions of all the major osteoblast-specific genes (i.e. osteocalcin, type I collagen, bone sialoprotein, osteopontin, alkaline phosphatase, and collagenase-3) and controls their expression (2, 4, 5). Conceivably, Cbfa1 expression plays a key role during osteoblast differentiation and skeletogenesis (6 -9). Members of the AP-1 (activator protein-1) family of homo-/heterodimeric transcription factors are also instrumental in regulating genes activated early in osteoblast differentiation. Thus, the expression of several osteoblast phenotypic genes such as alkaline phosphatase, type I collagen, osteopontin, osteocalcin, and collagenase-3, which are under th...

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A therosclerosis, the principal cause of cardiovascular diseases (CVDs), is a process that involves a complex interplay among different factors and cell types, including cells of the immune system (T cells, B cells, natural killer cells, monocytes/macrophages, dendritic cells) and cells of the vessel wall (endothelial cells [ECs], vascular smooth muscle cells [VSMCs]). The atherogenic process evolves in different stages, starting from inflammatory endothelial activation/ dysfunction and resulting in plaque vulnerability and rupture. Vitamin D deficiency affects almost 50% of the population worldwide. It has been suggested that this pandemic might contribute to the worldwide increased prevalence of CVD. 9-11Several mechanisms have been proposed to account for this inverse relationship. In addition to its effects exerted on numerous tissues and organs that indirectly participate in the atherosclerosis, vitamin D is directly involved in this systemic inflammatory process.12,13 Vitamin D receptors (VDRs) are present in all cells implicated in atherosclerosis, including ECs, VSMCs, and immune cells. Vitamin D appears to regulate a wide range of physiological and pathological processes like vascular cell growth, migration, and differentiation; immune response modulation; cytokine expression; and inflammatory and fibrotic pathways, all of which play a crucial role, starting from the early stage of endothelial activation/dysfunction to the later stages of the plaque vulnerability and rupture.In this review, we provide current data on the effects of vitamin D on cells directly implicated in atherosclerosis such as ECs, VSMCs, and immune cells (lymphocytes, monocytes, macrophages, etc) with a focus on the underlying molecular mechanisms, which are still largely unknown. We also summarize reports related to the favorable (antiatherogenic) actions of vitamin D in tissues and organs that indirectly participate in the atherogenic process. Finally, we critically discuss clinical studies to assess the protective role of vitamin D and the efficacy of vitamin D and VDR agonists in CVD. Because a comprehensive background is a prerequisite for further discussions of vitamin D-induced effects, we provide a brief description of vitamin D metabolism and mechanism of action. Vitamin D Metabolism and Mechanism of ActionVitamin D is a steroid hormone that comes in 2 forms that differ chemically in their side chain, D 2 and D 3 (Figure 1). Either produced in the skin (D 3 ) from 7-dehydrocholesterol by exposure to ultraviolet-B light or ingested with foods of plant or animal origin (D 2 and D 3 , respectively), vitamin D is biologically inert and requires 2 hydroxylations to form its active metabolite. 10 The first hydroxylation is constitutive and takes place in the liver by vitamin D-25-hydroxylase to form 25(OH)D. The second hydroxylation is catalyzed by 25(OH) D-1aOHase (CYP27B1) to form the biologically active form of vitamin D, 1,25(OH) 2 D (calcitriol; see Figure 1). This latter 1a-hydroxylation of 25(OH)D takes place in most tiss...

Identifying the biological properties of the cells residing within the periodontal ligament (PDL) will help in understanding the role that these cells play in the various functions of the periodontal ligament, and will improve the success of clinical procedures such as orthodontic tooth movement. For this purpose, fibroblasts isolated from human periodontium were cultured and characterized both histochemically and biochemically with respect to their putative osteoblast-like properties. Histochemically, cultured PDL fibroblasts showed an intense staining for alkaline phosphatase (ALP). Biochemically, the basal ALP activity increased in culture over time. ALP levels after stimulation with 1 alpha, 25-dihydroxyvitamin D3 were significantly higher than those of control cultures. Moreover, immunofluorescence against osteocalcin (a highly reliable osteoblastic marker) was strongly positive. Von Kossa staining of the cell cultures revealed the formation of mineral-like nodules. These results indicate that human PDL fibroblasts exhibit in vitro phenotypic characteristics consistent with osteoblast-like cells, thus suggesting that such cells have the potential to differentiate into osteoblasts and/or cementoblasts.

The aim of the present study was to examine whether a putative relationship exists between the Class II division 2 craniofacial type and congenital anomalies of the dentition, such as missing teeth, peg-shaped laterals, transpositions, supernumerary teeth and canine impactions. Two hundred and sixty-seven untreated patients with Class II division 2 malocclusion were examined. The results show that 56.6 per cent of the patients exhibited some form of congenital tooth anomaly, 13.9 per cent agenesis of the upper lateral incisors, 7.5 per cent peg-shaped upper laterals, while impacted canines were present in 33.5 per cent of the subjects. Transpositions were present in 1.1 per cent of the patients and in all cases the canine was involved. No patient exhibited a supernumerary tooth. Comparing the results of the present study with existing data on the percentage of congenital tooth anomalies in the general population, it can be concluded that Class II division 2 malocclusions are closely associated with congenital tooth anomalies.

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The aim of the present study was to investigate putative relationships between different malocclusions such as Class III and Class II division 1, and congenital tooth anomalies. Two-hundred Class III and 215 Class II division 1 patients were examined for the presence of any of the following congenital tooth anomalies: maxillary incisor hypodontia, maxillary canine impaction, transpositions, supernumerary teeth, and tooth agenesis. Their occurrence rates were then calculated as a percentage of the total sample and were compared for statistical differences. The results revealed no statistical difference (P > 0.05) in the occurrence rates of upper lateral incisor agenesis, peg-shaped laterals, impacted canines, or supernumerary teeth between the Class III and the Class II division 1 malocclusions. When the occurrence rate of all congenital tooth anomalies was compared between the two malocclusions, Class III subjects showed significantly higher rates (P < 0.05). Comparison with published surveys on general populations showed similar occurrence rates. It can be concluded that subjects with Class III and Class II division 1 malocclusions show patterns of congenital tooth anomalies similar to those observed in the general population. Congenital tooth anomalies may represent another criterion for the study of malocclusion, with respect to their origin and development.

The polycystins PC1 and PC2 are emerging as major players in mechanotransduction, a process that influences all steps of the invasion/metastasis cascade. We hypothesized that PC1 and PC2 facilitate cancer aggressiveness. Immunoblotting, RT-PCR, semi-quantitative and quantitative real-time PCR and FACS analyses were employed to investigate the effect of polycystin overexpression in colorectal cancer (CRC) cells. The impact of PC1 inhibition on cancer-cell proliferation was evaluated through an MTT assay. In vitro data were analyzed by Student's t-test. HT29 human xenografts were treated with anti-PC1 (extracellular domain) inhibitory antibody and analyzed via immunohistochemistry to determine the in vivo role of PC1 in CRC. Clinical significance was assessed by examining PC1 and PC2 protein expression in CRC patients (immunohistochemistry). In vivo and clinical data were analyzed by non-parametric tests, Kaplan-Meier curves, log-rank test and Cox model. All statistical tests were two-sided. PC1 overexpression promotes epithelial-to-mesenchymal transition (EMT) in HCT116 cells, while PC2 overexpression results in upregulation of the mTOR pathway in SW480 cells. PC1 inhibition causes reduced cell proliferation in CRC cells inducing tumor necrosis and suppressing EMT in HT29 tumor xenografts. In clinical study, PC1 and PC2 overexpression associates with adverse pathological parameters, including invasiveness and mucinous carcinomas. Moreover, PC1 overexpression appears as an independent prognostic factor of reduced recurrence-free survival (HR 5 1.016, p 5 0.03) and lowers overall survival probability, while aberrant PC2 expression predicts poor overall survival (p 5 0.0468). These results support, for the first time, a direct link between mechanosensing polycystins (PC1 and PC2) and CRC progression.Invasion and metastasis are responsible for 90% of cancerassociated mortality. While the role of biochemical signals in invasion and metastasis is well established, growing evidence reveals that mechanical signals also regulate cancer-cell