The Bioactive Acidic Serine- and Aspartate-Rich Motif Peptide

The organic component of the bone matrix comprises 40% dry weight of bone. The organic component is mostly composed of type I collagen and small amounts of non-collagenous proteins (NCPs) (10-15% of the total bone protein content). The small integrin-binding ligand N-linked glycoprotein (SIBLING) family, a NCP, is considered to play a key role in bone mineralization. SIBLING family of proteins share common structural features and includes the arginine-glycine-aspartic acid (RGD) motif and acidic serine- and aspartic acid-rich motif (ASARM). Clinical manifestations of gene mutations and/or genetically modified mice indicate that SIBLINGs play diverse roles in bone and extraskeletal tissues. ASARM peptides might not be primary responsible for the functional diversity of SIBLINGs, but this motif is suggested to be a key domain of SIBLINGs. However, the exact function of ASARM peptides is poorly understood. In this article, we discuss the considerable progress made in understanding the role of ASARM as a bioactive peptide

Functional Diversity of Fibroblast Growth Factors in Bone Formation

The functional significance of fibroblast growth factor (FGF) signaling in bone formation has been demonstrated through genetic loss-of-function and gain-of-function approaches. FGFs, comprising 22 family members, are classified into three subfamilies: canonical, hormone-like, and intracellular. The former two subfamilies activate their signaling pathways through FGF receptors (FGFRs). Currently, intracellular FGFs appear to be primarily involved in the nervous system. Canonical FGFs such as FGF2 play significant roles in bone formation, and precise spatiotemporal control of FGFs and FGFRs at the transcriptional and posttranscriptional levels may allow for the functional diversity of FGFs during bone formation. Recently, several research groups, including ours, have shown that FGF23, a member of the hormone-like FGF subfamily, is primarily expressed in osteocytes/osteoblasts.This polypeptide decreases serum phosphate levels by inhibiting renal phosphate reabsorption and vitamin D3 activation, resulting in mineralization defects in the bone. Thus, FGFs are involved in the positive and negative regulation of bone formation. In this review, we focus on the reciprocal roles of FGFs in bone formation in relation to their local versus systemic effects

Preparation of α-mannoside hydrogel and electrical detection of saccharide-protein interactions using the smart gel-modified gate field effect transistor

The purpose of this study was to detect saccharide-protein interaction capitalizing on the gel-modified field effect transistor [FET]. A lectin-sensitive polymer gel that undergoes volume changes in response to the formation of molecular complex between 'pendant' carbohydrate and a 'target' lectin concanavalin A [Con A] was synthesized. It was revealed that direction and magnitude of the gel response (swelling or deswelling) could be readily designed depending on composition and network density of the gel. The Con A-sensitive polymer gel has shown the ability to transduce the detection of saccharide-protein interactions into electrical signals for FET

Imaging and mapping of mouse bone using MALDI-imaging mass spectrometry

Matrix-assisted laser desorption/ionization-imaging mass spectrometry (MALDI-IMS) is an advanced method used globally to analyze the distribution of biomolecules on tissue cryosections without any probes. In bones, however, hydroxyapatite crystals make it difficult to determine the distribution of biomolecules using MALDI-IMS. Additionally, there is limited information regarding the use of this method to analyze bone tissues. To determine whether MALDI-IMS analysis of bone tissues can facilitate comprehensive mapping of biomolecules in mouse bone, we first dissected femurs and tibiae from 8-week-old male mice and characterized the quality of multiple fixation and decalcification methods for preparation of the samples. Cryosections were mounted on indium tin oxide-coated glass slides, dried, and then a matrix solution was sprayed on the tissue surface. Images were acquired using an iMScope at a mass-to-charge range of 100–1000. Hematoxylin-eosin, Alcian blue, Azan, and periodic acid-Schiff staining of adjacent sections was used to evaluate histological and histochemical features. Among the various fixation and decalcification conditions, sections from trichloroacetic acid-treated samples were most suitable to examine both histology and comprehensive MS images. However, histotypic MS signals were detected in all sections. In addition to the MS images, phosphocholine was identified as a candidate metabolite. These results indicate successful detection of biomolecules in bone using MALDI-IMS. Although analytical procedures and compositional adjustment regarding the performance of the device still require further development, IMS appears to be a powerful tool to determine the distribution of biomolecules in bone tissues

Does the tube-compensation function of two modern mechanical ventilators provide effective work of breathing relief?

OBJECTIVE: An endotracheal tube (ETT) imposes work of breathing on mechanically ventilated patients. Using a bellows-in-a-box model lung, we compared the tube compensation (TC) performances of the Nellcor Puritan-Bennett 840 ventilator and of the Dräger Evita 4 ventilator. MEASUREMENTS AND RESULTS: Each ventilator was connected to the model lung. The respiratory rate of the model lung was set at 10 breaths/min with 1 s inspiratory time. Inspiratory flows were 30 or 60 l/min. A full-length 8 mm bore ETT was inserted between the ventilator circuit and the model lung. The TC was set at 0%, 10%, 50%, and 100% for both ventilators. Pressure was monitored at the airway, the trachea, and the pleura, and the data were recorded on a computer for later analysis of the delay time, of the inspiratory trigger pressure, and of the pressure–time product (PTP). The delay time was calculated as the time between the start of inspiration and minimum airway pressure, and the inspiratory trigger pressure was defined as the most negative pressure level. The same measurements were performed under pressure support ventilation of 4 and 8 cmH(2)O. The PTP increased according to the magnitude of inspiratory flow. Even with 100% TC, neither ventilator could completely compensate for the PTP imposed by the ETT. At 0% TC the PTP tended to be less with the Nellcor Puritan-Bennett 840 ventilator, while at 100% TC the PTP tended to be less with the Dräger Evita 4 ventilator. A small amount of pressure support can be equally effective to reduce the inspiratory effort compared with the TC. CONCLUSION: Although both ventilators provided effective TC, even when set to 100% TC they could not entirely compensate for a ventilator and ETT-imposed work of breathing. The effect of TC is less than that of pressure support ventilation. Physicians should be aware of this when using TC in weaning trials

The PPARgamma-selective ligand BRL-49653 differentially regulates the fate choices of rat calvaria versus rat bone marrow stromal cell populations

Abstract Background Osteoblasts and adipocytes are derived from a common mesenchymal progenitor and an inverse relationship between expression of the two lineages is seen with certain experimental manipulations and in certain diseases, i.e., osteoporosis, but the cellular pathway(s) and developmental stages underlying the inverse relationship is still under active investigation. To determine which precursor mesenchymal cell types can differentiate into adipocytes, we compared the effects of BRL-49653 (BRL), a selective ligand for peroxisome proliferators-activated receptor (PPAR)γ, a master transcription factor of adipogenesis, on osteo/adipogeneis in two different osteoblast culture models: the rat bone marrow (RBM) versus the fetal rat calvaria (RC) cell system. Results BRL increased the number of adipocytes and corresponding marker expression, such as lipoprotein lipase, fatty acid-binding protein (aP2), and adipsin, in both culture models, but affected osteoblastogenesis only in RBM cultures, where a reciprocal decrease in bone nodule formation and osteoblast markers, e.g., osteopontin, alkaline phosphatase (ALP), bone sialoprotein, and osteocalcin was seen, and not in RC cell cultures. Even though adipocytes were histologically undetectable in RC cultures not treated with BRL, RC cells expressed PPAR and CCAAT/enhancer binding protein (C/EBP) mRNAs throughout osteoblast development and their expression was increased by BRL. Some single cell-derived BRL-treated osteogenic RC colonies were stained not only with ALP/von Kossa but also with oil red O and co-expressed the mature adipocyte marker adipsin and the mature osteoblast marker OCN, as well as PPAR and C/EBP mRNAs. Conclusion The data show that there are clear differences in the capacity of BRL to alter the fate choices of precursor cells in stromal (RBM) versus calvarial (RC) cell populations and that recruitment of adipocytes can occur from multiple precursor cell pools (committed preadipocyte pool, multi-/bipotential osteo-adipoprogenitor pool and conversion of osteoprogenitor cells or osteoblasts into adipocytes (transdifferentiation or plasticity)). They also show that mechanisms beyond activation of PPARγ by its ligand are required for changing the fate of committed osteoprogenitor cells and/or osteoblasts into adipocytes

The EP4-ERK-dependent pathway stimulates osteo-adipogenic progenitor proliferation resulting in increased adipogenesis in fetal rat calvaria cell cultures

We previously reported that fetal rat calvaria (RC) cells are osteo-adipogenic bipotential and that PGE2 receptors EP2 and EP4 are involved in bone nodule formation via both common and distinct MAPK pathways in RC cell cultures. Because PGE2 participates in multiple biological processes including adipogenesis, it is of interest to determine the additional role(s) of PGE2 in RC cells. PGE2 increased the number of adipocyte colonies when RC cells were treated during proliferation but not other development stages. Of four EP agonists tested, the EP4 agonist ONO-AE1-437 (EP4A) was the most effective in promoting adipogenesis. Concomitantly, EP4A increased the number of cells with BrdU labeling and gene expression of CCAAT/enhancer binding protein (C/EBP)δ and c-fos but not peroxisome proliferator-activated receptor γ2 and C/EBPα. Amongst MAPK inhibitors, U0126, an inhibitor of MEK1/2, abrogated the EP4A-dependent effects. Our results suggest that the PGE2–EP4-ERK pathway increases the number of osteo-adipogenic bipotential progenitor cells, with a resultant increase in adipogenesis in RC cell cultures.This work was supported in part by grants from the Ministry of Education, Science, Sports and Culture of Japan (13771074 to YY)and Ono Pharmaceutical Co. (to YY), and the Canadian Institutes of Health Research (CIHR; FRN 83704 to JEA)

1α,25-dihydroxyvitamin D3 acts predominately in mature osteoblasts under conditions of high extracellular phosphate to increase fibroblast growth factor 23 production in vitro

Osteoblasts/osteocytes are the principle sources of fibroblast growth factor 23 (FGF23), a phosphaturic hormone, but the regulation of FGF23 expression during osteoblast development remains uncertain. Because 1α,25-dihydroxyvitamin D3 (1,25(OH)2D3) and inorganic phosphate (Pi) may act as potent activators of FGF23 expression, we estimated how these molecules regulate FGF23 expression during rat osteoblast development in vitro. 1,25(OH)2D3-dependent FGF23 production was restricted largely to mature cells in correlation with increased vitamin D receptor (VDR) mRNA levels, in particular, when Pi was present. Pi alone and more so in combination with 1,25(OH)2D3 increased FGF23 production and VDR mRNA expression. Parathyroid hormone, stanniocalcin 1, prostaglandin E2, FGF2, and foscarnet did not increase FGF23 mRNA expression. Thus, these results suggest that 1,25(OH)2D3 may exert its largest effect on FGF23 expression/production when exposed to high levels of extracellular Pi in osteoblasts/osteocytes

Soluble Klotho causes hypomineralization in Klotho-deficient mice

The type I transmembrane protein αKlotho (Klotho) serves as a coreceptor for the phosphaturic hormone fibroblast growth factor 23 (FGF23) in kidney, while a truncated form of Klotho (soluble Klotho, sKL) is thought to exhibit multiple activities, including acting as a hormone, but whose mode(s) of action in different organ systems remains to be fully elucidated. FGF23 is expressed primarily in osteoblasts/osteocytes and aberrantly high levels in the circulation acting via signaling through an FGF receptor (FGFR)-Klotho coreceptor complex cause renal phosphate wasting and osteomalacia. We assessed the effects of exogenously added sKL on osteoblasts and bone using Klotho-deficient (kl/kl) mice and cell and organ cultures. sKL induced FGF23 signaling in bone and exacerbated the hypomineralization without exacerbating the hyperphosphatemia, hypercalcemia and hypervitaminosis D in kl/kl mice. The same effects were seen in rodent bone models in vitro, in which we also detected formation of a sKL complex with FGF23-FGFR and decreased Phex (gene responsible for X-linked hypophosphatemic rickets (XLH)/osteomalacia) expression. Further, sKL-FGF23-dependent hypomineralization in vitro was rescued by soluble PHEX. These data suggest that exogenously added sKL directly participates in FGF23 signaling in bone and that PHEX is a downstream effector of the sKL-FGF23-FGFR axis in bone.This work was supported in part by grants from the Ministry of Education, Science, Sports and Culture, Japan (18592001 and 20592139 to Y Y and 21791788 to T M), and the Canadian Institutes of Health Research (MOP 83704 to J E A)