Mineralization defects in cementum and craniofacial bone from loss of bone sialoprotein

Abstract Bone sialoprotein (BSP) is a multifunctional extracellular matrix protein found in mineralized tissues, including bone, cartilage, tooth root cementum (both acellular and cellular types), and dentin. In order to define the role BSP plays in the process of biomineralization of these tissues,...

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Published in:	Bone (New York, N.Y.) Vol. 78; pp. 150 - 164
Main Authors:	Foster, B.L, Ao, M, Willoughby, C, Soenjaya, Y, Holm, E, Lukashova, L, Tran, A.B, Wimer, H.F, Zerfas, P.M, Nociti, F.H, Kantovitz, K.R, Quan, B.D, Sone, E.D, Goldberg, H.A, Somerman, M.J
Format:	Journal Article
Language:	English
Published:	United States Elsevier Inc 01-09-2015
Subjects:	Animals Bone Bone Resorption Cartilage Cartilage - metabolism Cementogenesis Cementum Dental Cementum - metabolism Dentin Dentin - metabolism Dentinogenesis Extracellular matrix Extracellular Matrix - metabolism Facial Bones - diagnostic imaging Facial Bones - pathology Imaging, Three-Dimensional Integrin-Binding Sialoprotein - metabolism Mice Mice, Knockout Microscopy, Electron, Transmission Mineralization Molar - metabolism Odontogenesis Orthopedics Osteoclasts - metabolism Osteogenesis Osteopontin - genetics Osteopontin - metabolism Polymerase Chain Reaction RANK Ligand - metabolism Skull - diagnostic imaging Skull - pathology Tooth - physiology Tooth Root - metabolism X-Ray Microtomography Dentin Cartilage Extracellular matrix Bone Mineralization Cementum
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Summary:	Abstract Bone sialoprotein (BSP) is a multifunctional extracellular matrix protein found in mineralized tissues, including bone, cartilage, tooth root cementum (both acellular and cellular types), and dentin. In order to define the role BSP plays in the process of biomineralization of these tissues, we analyzed cementogenesis, dentinogenesis, and osteogenesis (intramembranous and endochondral) in craniofacial bone in Bsp null mice and wild-type (WT) controls over a developmental period (1–60 days post natal; dpn) by histology, immunohistochemistry, undecalcified histochemistry, microcomputed tomography (microCT), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and quantitative PCR (qPCR). Regions of intramembranous ossification in the alveolus, mandible, and calvaria presented delayed mineralization and osteoid accumulation, assessed by von Kossa and Goldner's trichrome stains at 1 and 14 dpn. Moreover, Bsp−/− mice featured increased cranial suture size at the early time point, 1 dpn. Immunostaining and PCR demonstrated that osteoblast markers, osterix, alkaline phosphatase, and osteopontin were unchanged in Bsp null mandibles compared to WT. Bsp−/− mouse molars featured a lack of functional acellular cementum formation by histology, SEM, and TEM, and subsequent loss of Sharpey's collagen fiber insertion into the tooth root structure. Bsp−/− mouse alveolar and mandibular bone featured equivalent or fewer osteoclasts at early ages (1 and 14 dpn), however, increased RANKL immunostaining and mRNA, and significantly increased number of osteoclast-like cells (2–5 fold) were found at later ages (26 and 60 dpn), corresponding to periodontal breakdown and severe alveolar bone resorption observed following molar teeth entering occlusion. Dentin formation was unperturbed in Bsp−/− mouse molars, with no delay in mineralization, no alteration in dentin dimensions, and no differences in odontoblast markers analyzed. No defects were identified in endochondral ossification in the cranial base, and craniofacial morphology was unaffected in Bsp−/− mice. These analyses confirm a critical role for BSP in processes of cementogenesis and intramembranous ossification of craniofacial bone, whereas endochondral ossification in the cranial base was minimally affected and dentinogenesis was normal in Bsp−/− molar teeth. Dissimilar effects of loss of BSP on mineralization of dental and craniofacial tissues suggest local differences in the role of BSP and/or yet to be defined interactions with site-specific factors.
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 Martha J. Somerman Martha.somerman@nih.gov Bryan D. Quan bryan.quan@utoronto.ca Lyudmila Lukashova lukashoval@hss.edu Anne B. Tran anne.tran2@nih.gov Patricia M. Zerfas patricia.zerfas@nih.gov Chelsea Willoughby chelseawilloughby15@gmail.com Harvey A. Goldberg hagoldbe@uwo.ca Min Ao fnu.aomin@nih.gov Yohannes Soenjaya yosoenjay@uwo.ca Helen F. Wimer helen.wimer@nih.gov Kamila R. Kantovitz kamilark@yahoo.com.br Eli D. Sone eli.sone@utotonto.ca Erik Holm eholm@uwo.ca Francisco H. Nociti nociti@unicamp.br
ISSN:	8756-3282 1873-2763
DOI:	10.1016/j.bone.2015.05.007