title: A synthetic peptide fragment of human MEPE stimulates new bone formation in vitro and in vivo.
abstract: Matrix extracellular phosphoglycoprotein (MEPE) was proposed as a candidate for the phosphaturic hormone phosphatonin. We found that a synthetic peptide fragment of MEPE containing the RGD and SGDG sequence stimulated new bone formation in vitro and in vivo.
  
  
  BACKGROUND
  Matrix extracellular phosphoglycoprotein (MEPE) was recently identified as a candidate for the phosphaturic hormone phosphatonin, which has been implicated in disturbed phosphate metabolism, rickets, and osteomalacia associated with X-linked hypophosphatemic rickets (XLH) and oncogenic hypophosphatemic osteomalacia (OHO). MEPE expression was predominantly found in osteoblasts, and mice deficient in a homolog of MEPE showed increased bone density, suggesting that MEPE produced in osteoblasts negatively regulates bone formation. In this study, we examined the effects of a synthetic 23mer peptide fragment of MEPE (AC-100, region 242-264) containing the RGD (integrin-binding) and SGDG (glycosaminoglycan-attachment) motif on bone formation in vitro and in vivo.
  
  
  METHODS
  The osteogenic activity of AC-100 was examined in organ cultures of neonatal mouse calvariae and in vivo by injecting AC-100 onto the calvariae of mice.
  
  
  RESULTS
  Histomorphometric examination showed that AC-100 stimulated new bone formation with increased numbers of osteoblasts in neonatal mouse calvariae in organ culture. In contrast, synthetic MEPE fragment peptides without either the RGD or SGDG motif failed to increase new bone formation. Repeated daily subcutaneous injections of AC-100 onto the calvariae in mice increased bone thickness and stimulated new bone formation as determined by the calcein double-labeling technique. However, peptides in which the RGD or SGDG sequence was scrambled did not stimulate new bone formation in vivo. AC-100 increased cell proliferation and alkaline phosphatase activity and activated focal adhesion kinase (FAK) and extracellular signal-regulated protein kinase (ERK) in human primary osteoblasts.
  
  
  CONCLUSIONS
  Our results show that a synthetic peptide corresponding with the sequence of human MEPE fragment stimulates new bone formation with increased number of osteoblasts. The results also suggest that the RGD and SGDG motifs are critical to the osteogenic activity of AC-100, presumably through activating integrin signaling pathways in osteoblasts. The anabolic effects of AC-100 may be beneficial for bone diseases associated with decreased bone formation.
authors.affiliation: Department of Biochemistry, Graduate School of Dentistry, Osaka University, Suita, Osaka, Japan.
authors.forename: Tetsuyuki
authors.initials: T
authors.lastname: Hayashibara
authors.forename: Toru
authors.initials: T
authors.lastname: Hiraga
authors.forename: Bing
authors.initials: B
authors.lastname: Yi
authors.forename: Motoyoshi
authors.initials: M
authors.lastname: Nomizu
authors.forename: Yoshinari
authors.initials: Y
authors.lastname: Kumagai
authors.forename: Riko
authors.initials: R
authors.lastname: Nishimura
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Yoneda
mesh_terms: D020816:Amino Acid Motifs / Q000502:physiology; D000595:Amino Acid Sequence; D000818:Animals; D000831:Animals, Newborn; D016326:Extracellular Matrix Proteins / Q000138:chemical synthesis / Q000235:genetics; D006023:Glycoproteins / Q000138:chemical synthesis / Q000235:genetics; D006025:Glycosaminoglycans / Q000502:physiology; D006801:Humans; D016023:Integrins / Q000378:metabolism; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000502:physiology; D009924:Organ Culture Techniques; D010012:Osteogenesis; D010446:Peptide Fragments / Q000737:chemistry / Q000494:pharmacology*; D010750:Phosphoproteins / Q000138:chemical synthesis / Q000235:genetics; D015398:Signal Transduction
chemical_list: D016326:Extracellular Matrix Proteins; D006023:Glycoproteins; D006025:Glycosaminoglycans; D016023:Integrins; C487705:MEPE protein (242-264), human; C486579:MEPE protein, human; D009842:Oligopeptides; D010446:Peptide Fragments; D010750:Phosphoproteins; C047981:arginyl-glycyl-aspartic acid; D020928:Mitogen-Activated Protein Kinases