Oxygen tension regulates osteoblast function

doi:10.1016/S0889-5406(94)70006-0

American Journal of Orthodontics and Dentofacial Orthopedics

Volume 105, Issue 5, May 1994, Pages 457-463

https://doi.org/10.1016/S0889-5406(94)70006-0 Get rights and content

Abstract

Abrupt changes in oxygen availability within the periodontium have been suggested to have a regulatory role in alveolar bone remodeling during tooth movement; arguably, similar to that seen in bone growth or fracture healing. The purpose of this investigation was therefore to study the effects of ambient hypoxia and hyperoxia on osteoblast function in vitro. Osteoblast-enriched cultures from fetal rat calvariae were exposed to atmospheres of hyperoxia (90% O₂) and hypoxia (10% O₂) and assayed for media pH, PO₂, pCO₂, cellular proliferation, alkaline phosphatase (AP) activity, and collagen synthesis. Results of this study show that in low ambient oxygen tension cellular proliferation increases, whereas the AP activity, collagen synthesis, media PO₂, PCO₂ decreases. In contrast, in hyperoxic conditions cellular proliferation is suppressed with concomitant increases in: AP activity, collagen synthesis, and partial pressures for oxygen and carbon dioxide. Media pH remained unaffected. In crossover experiments, where cells were initially grown in hypoxic conditions and were switched to hyperoxic conditions, their metabolic activities were abruptly reversed. These findings in conjunction with earlier reports, suggest a triggering role for oxygen tension (an environmental factor) in bone remodeling. (AM J ORTHOD DENTOFAC ORTHOP 1994;105:457-63.)

Section snippets

Materials

Tissue culture supplies were obtained from Gibco (Grand Island, N.Y.), and the bacterial crude collagenase was purchased from Sigma (St. Louis, Mo.). Isoton was obtained from Fisher Scientific (Itasca, Ill). Data were analyzed by Student's t test, where appropriate.

Bone cell isolation

Cells were obtained from 19- to 21-day-old embryonic Sprague-Dawley rat calvariae by sequential collagenase digestion,²⁴ and the latter digests were taken as osteoblastic for their high alkaline phosphatase activity and the ability

Results

The results presented here portray readings from at least four or eight separate experiments; each assay was performed in triplicate or in quadruplicate. Data are expressed as mean readings ± standard error of the mean (SEM).

Discussion

Although the reaction of alveolar bone to application of orthodontic forces is a complex process, results of this study are suggestive that oxygen tension might serve to modulate the osteoblastic activity. Thus, potential regulation of remodeling by mechanically induced vascular activity10, 11 in the oxygen-sensitive periodontal structures appear to be a reasonable conjecture.16, 23 With orthodontic pressure application, tissue fluids are squeezed out and blood vessels are collapsed. We

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Original ArticlesOxygen tension regulates osteoblast function

Abstract

Section snippets

Materials

Bone cell isolation

Results

Discussion

AM J ORTHOD

AM J ORTHOD

AM J ORTHOD

AM J ORTHOD DENTOFAC ORTHOP

AM J ORTHOD DENTOFAC ORTHOP

Metab Bone Dis Relat Res

Dev Biol

Bone

Bone

AM J ORTHOD DENTOFAC ORTHOP

The biomechanical rationale of orthodontic therapy

The role of cyclic AMP, calcium and prostaglandins in bone resorption associated with experimental tooth movement

J Dent Res

Leukotrines in orthodontic tooth movement

AM J ORTHOD DENTOFAC ORTHOP

The effect of indomethacin (an aspirin-like drug) on the rate of orthodontic tooth movement

AM J ORTHOD

Kinetics of cell proliferation and migration associated with orthodontically-induced osteogenesis

J Dent Res

A bone resorptive agent extracted from orthodontically-treated tissues of the rat

Angle Orthod

Original Articles
Oxygen tension regulates osteoblast function