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  • 1
    ISSN: 1432-0878
    Keywords: Key words: Periodontium ; Osteopontin ; Bone sialoprotein ; Cell proliferation ; Rat (Wistar)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. Cellular repopulation was studied in a model in which adjacent mineralising and soft connective tissue matrices are regenerated. Window wounds were created through alveolar bone, with either preservation or removal of periodontal ligament, in 30 male Wistar rats. Three animals per time period were killed on days 1, 3, 7, 14, and 28 after surgery for each wound type. Cellular proliferation in alveolar bone and periodontal ligament was assessed by 3H-thymidine labelling 1 h before death, followed by radioautographic analysis. Cellular differentiation was determined by the temporal expression of the bone-related markers osteopontin and bone sialoprotein, using immunohistochemical methods. In regenerating periodontium, osteopontin was expressed earlier than bone sialoprotein, which was restricted to alveolar bone. After wounding, transient expression of osteopontin was detected in the periodontal ligament at days 1 and 3. In general, wounding induced fivefold higher proliferation and clonal growth of periodontal ligament cells compared to the unwounded (control) side. Combined immunostaining and radioautography demonstrated colocalisation of osteopontin in sites with high numbers of labelled cells in both nascent periodontal ligament and regenerating alveolar bone at days 3 and 7. In contrast, bone sialoprotein, which appeared in regenerating alveolar bone on days 14–28 after wounding, was expressed much later than the peak of cellular proliferation. We conclude that (1) the intact periodontal ligament influences cell proliferation and osteopontin expression; (2) osteopontin is an early marker of periodontal tissue regeneration that is temporally and spatially associated with intensive cell proliferation and migration in osteogenic and periodontal ligament cell populations; and (3) bone sialoprotein is expressed after proliferation at sites of mineralising bone formation.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0878
    Keywords: Key words Periodontal ligament ; α-Smooth muscle actin ; Osteopontin ; Bone sialoprotein ; Bone morphogenic protein ; Rat (Wistar)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  Periodontal ligament width is precisely maintained throughout the lifetime of adult mammals but the biological mechanisms that inhibit ingrowth of bone into this soft connective tissue are unknown. As bone morphogenic proteins strongly stimulate osteogenesis and can induce ectopic bone formation in vivo, we tested the hypothesis that topical application of this powerful osteogenic agent will overwhelm the osteogenic inhibitory mechanisms of periodontal ligament cells and induce ankylosis. Wounds through the alveolar bone and periodontal ligament were created in 45 male Wistar rats. Defects were filled with either a collagen implant or collagen plus bone morphogenic protein (BMP-7), or were left unfilled (controls). Three animals per time period were killed on days 2, 5, 10, 21 and 60 after surgery for each wound type. Cellular proliferation and clonal growth in periodontal tissues were assessed by 3H-thymidine labeling 1 h before death, followed by radioautography. Cellular differentiation of soft and mineralizing connective tissue cell populations was determined by immunohistochemical staining of α-smooth muscle actin, osteopontin and bone sialoprotein. In regenerating periodontium, BMP-7 induced abundant bone formation by 21 days (2.5-fold greater than controls or collagen implant only; P〈0.001), but by day 60 the volume of the newly formed bone had returned to baseline levels and was similar for all groups. Independent of the type of treatment, periodontal ligament width was unchanged throughout the experimental period (P〉0.05). Animals treated with BMP-7 implants showed greatly increased cellular proliferation in the periodontal ligament adjacent to the wound site and in the regenerating alveolar bone at days 5 and 10 after wounding compared to the other treatment groups (P〈0.005). Animals in the BMP-7 group exhibited similar spatial and temporal staining patterns for α-smooth muscle actin, osteopontin and bone sialoprotein as controls. Collectively, these data show that BMP-7 promoted the proliferation of precursor cells in the periodontal ligament but did not induce osteogenic differentiation in this compartment. Consequently a powerful osteogenic stimulus like BMP-7 cannot significantly perturb the mechanisms that regulate periodontal ligament width and maintain periodontal homeostasis.
    Type of Medium: Electronic Resource
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