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

Can the Baryon Number Density and the Cosmological Constant be interrelated?

A toy model is proposed in which the cosmological constant and the baryon number density of the universe are interrelated. The model combines the mechanism of Dimopoulos and Susskind in which the baryon number density of the universe is generated by the time-dependence of the phase of a complex scalar field, i.e. its `angular momentum' in the two-dimensinal complex field space, with that of Yoshimura in which the `centrifugal force' due the `angular momentum' pushes the vacuum expectation value of the scalar field out of a negative potential minimum and provides a small but positive cosmological constant. Unfortunately, our model fails to relate the smallness of the two numbers directly, requiring a fine-tuning of the negative potential minimum.Comment: 13pages, Added references, corrected typos, some changes to abstract and discussion, version to appear in PL

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

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

Processes of Osteophyte Formation in Guinea Pigs with Spontaneous Osteoarthritis

In this study, we investigated osteophyte formation processes in guinea pigs with spontaneous osteoarthritis, histochemically and immunohistochemically. Serial thin frontal sections of right knee joints were prepared from Hartley guinea pigs aged 1, 3, 5, 8, 12 and 18 months. The severity of osteoarthritis was evaluated by safranin-O staining, and the animals were classified into 3 groups: mild, moderate and severe. In addition, immunostaining was performed by using primary antibodies against the proliferating cell nuclear antigen (PCNA), type-I, -II and -III collagens, insulin-like growth factor 1 (IGF-1) and IGF-1 receptor. In the mild group, there was fibrous connective tissue continuous with the synovial membrane and covering the margins of the articular cartilage of the medial tibial condyle. This tissue contained spindle-shaped fibroblastic-like cells. These cells were positive for PCNA, type-I and -III collagens, IGF-1 and IGF-1 receptor. In the moderate group, the chondrocytes beneath the fibroblastic-like cell layer had proliferated and were clustered together. These chondrocytes were also positive for PCNA, type-I and -III collagens, IGF-1 and IGF-1 receptor. In the severe group, this marginal area had been replaced by type-II collagen-positive chondrophytes, which further changed to osteophytes due to the process of endochondral ossification. In guinea pigs, fibroblastic-like cells at the margins of the articular cartilage of the knee joints seemed to be totipotent immature mesenchymal cells. These cells may be the precursors of osteophytes, and IGF-1 appears to be involved in their formation

Apoptotic Cell Death and p53 Expression in Leiomyosarcoma of Soft-Tissue Origin

Leiomyosarcoma (LMS) of soft-tissue origin was studied on the expression and the biological significance of apoptosis in relation to p53 oncoprotein. Immunohistochemical analysis was performed initially on the paraffin-embbeded sections taken from 29 surgical tissues (20 cases) including 9 recurrent/metastatic tumors. The results are as follows: A positive correlation was observed between the p53 indices (PIs) and the proliferative markers designated by Ki-67, PCNA and MCM2, both of which increased significantly in the high-grade malignant LMS much more than in the low-grade one (P < 0.001). Apoptotic cells were detected by the TUNEL method and evaluated as the apoptotic index (AI). A high AI-level was shown in the high-grade malignant LMS, especially in cases of the recurrent/metastatic sites in comparison with the tumors of the primary site (P < 0.05). The AI was statistically higher in the p53-positive cases of high-grade malignant LMS than in the p53-negative cases of low-grade malignant LMS. In conclusion, apoptotic activity paralleled the overexpression of p53 protein along with an increasing grade of malignancy and may be related intimately to the increased malignant potential, especially to recurrence/metastasis