Developmental analysis by histology, histochemistry, and SEM revealed a significant reduction in acellular cementum formation on Bsp-/-. Acellular extrinsic fiber cementum: a thin layer typically of μm thickness extending from the coronal extent of the root throughout, consisting of a mineralized. Acellular cementum Cellular cementum First formed cementum Formed after acellular cementum Most of it is formed before the tooth.
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Bone sialoprotein BSP is an extracellular matrix protein found in mineralized tissues of the skeleton and dentition.
BSP is multifunctional, affecting cell attachment and signaling through an RGD integrin-binding region, and acting as a cenentum regulator for mineral precipitation by nucleating hydroxyapatite crystals. BSP is present in cementum, the hard tissue covering the tooth root that anchors periodontal ligament PDL attachment.
Results collected here suggest that BSP plays a non-redundant role in acellular cementum formation, likely involved in initiating mineralization on the root surface. Through its importance to cementum integrity, BSP is essential for periodontal function. The ability of BSP to act as a positive regulator of hydroxyapatite precipitation has been demonstrated in vitro Hunter and Goldberg, and is of particular interest in terms of regulating mineralized tissue development. In addition to its inclusion in bone extracellular matrix, BSP is present in both acellular and cellular cementum MacNeil et al.
Acellular cementum is the thin, mineralized tissue covering the cervical portion of the tooth root, important for attachment of the periodontal ligament PDL to the root surface Bosshardt, ; Foster et al. Cellular cementum is a more cementtum tissue covering apical portions of roots. Developmental factors directing cementogenesis remain poorly defined, hampering progress toward more effective therapies for cementum regeneration.
The finding that BSP was present in cementum and strongly expressed by cementoblasts led to speculation that this protein might contribute to aellular formation and mineralization Somerman et al. Here, we analyzed the function of BSP in cementogenesis and periodontal stability by determining the effects of the lack of BSP on tooth formation. From 3 to 6 animals were analyzed per genotype at ages 14, 26, 30, and 60 post-natal days dpn. For SEM analysis, extracted and cleansed molars were osmium-coated.
Histomorphometry was used to quantify cementum, root-lining cells, and epithelial attachment, and statistical analysis was performed by independent-samples t test. IHC used biotinylated secondary antibodies and peroxidase substrate. Primary antibodies included rabbit anti-BSP 1: Bsp mRNA is highly expressed by cementoblasts during tooth root formation, as well acellklar by osteoblasts of the alveolar bone Fig.
BSP protein is localized to alveolar bone and to acellular and cellular cementum covering the cervical and apical portions of the molar, respectively Figs. Bone sialoprotein is required for proper acellular cementum formation. A Bsp mRNA is expressed by cementoblasts cb and osteoblasts ob during molar tooth root development at 14 dpn.
B, C BSP protein is localized to alveolar bone bacellular cementum acand cellular cementum cc at 26 dpn.
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White box in B is shown at higher magnification in C to highlight acellular cementum. F, G Newly formed acellular cementum anchors periodontal ligament pdl attachment in WT molars. At 14 post-natal days dpna basophilic layer of acellular cementum covered the root dentin in WT mice Figs. At 26 dpn, WT acellular cementum had grown thicker, and inserted PDL fibers radiated from the surface of the cervical root Figs.
Some cracking is evident as an artifact of sample preparation. WT first molar roots at 14 dpn Appendix Fig. PDL fringe fibers at the root surface suggested that the proper acellular cementum matrix was present for cementogenesis Appendix Figs. Markers of local and systemic mineral metabolism were assayed. WT molars Appendix Figs.
Histology of human cementum: Its structure, function, and development
WT molars at 26 dpn displayed dense and highly organized collagen fiber insertions in the cervical root, visualized by picrosirius red staining under polarized light Figs. There was no indication that inflammation played a significant role in the periodontal breakdown, based on histology and the lack of neutrophil infiltration into the periodontia Appendix Fig.
A, B Picrosirius-red-stained sections viewed under polarized light reveal a high degree of organization and directionality indicated by high-intensity caellular fibers of periodontal aceklular pdl collagen fibrils between acellular cementum ac and bone b in WT molars at 26 dpn. WT molars, concentrated in the cervical roots Figs. WT mandibles, particularly along the lingual aspect Figs. White boxes in A cementjm B indicate regions shown at higher magnification in C and E, respectively.
BSP is an extracellular matrix protein present in bone and cementum. Here we demonstrate for the first time that lack of BSP inhibited the formation and mineralization of acellular cementum. Because of its importance to cementum formation, BSP is essential for the formation of a functional periodontium.
Lack scellular BSP led to a severe developmental inhibition of acellular cementum formation, shown here by histology, histochemistry, immunohistochemistry, and SEM. Aceklular a late stage in odontogenesis, cementum formation depends on a number of prior developmental stages.
We have demonstrated that reduction of PP iin turn, promotes increased acellular cementum formation Foster et al. Cellular cementum size was undiminished by the loss of BSP, though mineralization was delayed at earlier ages; functional consequences of this are under study. Acellular cementum forms as a progressive mineralization of the PDL collagen fiber bundles inserting into the root surface. We have previously shown BSP binds collagen with high affinity Tye et al.
OPN functions as an inhibitor of hydroxyapatite crystal growth in vitro and in vivo Hunter et al. The presence of OPN in the absence of BSP may additionally tip the balance acelluoar inhibition of cementum mineralization.
It is also possible that another function of BSP e.
A cmeentum periodontal complex depends on stable insertion acellulzr PDL collagen fibers into the acellular cementum, as well as ability for remodeling on the bone surface of the PDL space.
Lack of PDL-tooth anchorage was followed by PDL disorganization, epithelial down-growth, and tooth and alveolar bone resorption. Similar examples of periodontal degradation have resulted in transgenic mouse models with compromised periodontal function, e. Substitution of a cemetum diet for pelletized chow is currently being studied to determine the contribution of occlusal stress to the incidence of periodontal breakdown and incisor malocclusion.
Conversely, BSP over-expression increased osteoclastic activity Valverde et al. In summary, results from these studies show, for the first time, that BSP is critical for acellular cementum formation and periodontal attachment. The role of BSP in acellular cementogenesis is likely cemenrum be in promoting mineralization at the root surface to anchor PDL fibers and provide strong attachment of the tooth to the alveolar bone.
Loss-of-function of BSP may predispose to periodontal disease through defective cementum-PDL attachment and inability to prevent establishment of biofilm in the periodontal space.
Ongoing studies will further elucidate potential roles of BSP in cementum formation and regeneration, and in wider periodontal biology.
Acellular cementum – definition of acellular cementum by The Free Dictionary
A supplemental appendix to this article is published electronically only at http: National Center for Biotechnology InformationU. Published online Nov Soenjaya2 F. Holm4 P. Zerfas5 H. Wimer6 D. Holdsworth7 J. Aubin8 G. Hunter2, 4, 9 H. Goldberg2, 4, acellulxr, a and M. Author information Article notes Copyright and License information Disclaimer. This article has been cited by other articles in Cdmentum.
Associated Data Supplementary Materials Supplementary material.
Histology of human cementum: Its structure, function, and development
Abstract Bone sialoprotein BSP is an extracellular matrix protein found in mineralized tissues of the skeleton and dentition. Open in a separate window. Discussion BSP is an extracellular matrix protein present in bone and cementum.
Acellular Cementum as a Mineralization-sensitive Tissue Lack of BSP led to a severe developmental inhibition of acellular cementum formation, shown here by histology, histochemistry, immunohistochemistry, and SEM. Supplementary Material Supplementary material: Click here to view. Phosphorylation of Ser is critical for potent bone sialoprotein-mediated nucleation of hydroxyapatite crystals.
Root development in mice lacking functional tissue non-specific alkaline phosphatase gene: J Dent Res Osteopontin deficiency increases mineral content and mineral crystallinity in mouse bone. Calcif Tissue Int Are cementoblasts a subpopulation of osteoblasts or a unique phenotype? Developmental appearance and distribution of bone sialoprotein and osteopontin in human and rat acellular.
Bone sialoprotein deficiency impairs osteoclastogenesis and mineral resorption in xementum. J Bone Miner Res Transmission electron microscopy of bone. Methods Mol Biol Connect Tissue Acellulat 44 Suppl 1: Methods for studying tooth root cementum by light microscopy. Int J Oral Sci 4: Advances in defining regulators of cementum development and periodontal regeneration.
Curr Top Dev Biol The progressive ankylosis protein regulates cementum apposition and extracellular matrix composition. Cells Tissues Organs Central role of pyrophosphate in acellular cementum formation.
Crit Rev Oral Biol Med Functional analysis of bone sialoprotein: