Effects of sera on bone resorption in tissue culture

Masquelet technique: The effect of altering implant material and topography on membrane matrix composition, mechanical and barrier properties in a rat defect model

The Masquelet technique is a surgical procedure to regenerate segmental bone defects. The two-phase treatment relies on the production of a vascularized foreign-body membrane to support bone grafts over three times larger than the traditional maximum. Historically, the procedure has always utilized a bone cement spacer to evoke membrane production. However, membrane formation can easily be effected by implant surface properties such as material and topology. This study sought to determine if the membrane's mechanical or barrier properties are affected by changing the spacer material to titanium or roughening the surface finish. Ten-week-old, male Sprague Dawley rats were given an externally stabilized, 6 mm femur defect which was filled with a pre-made spacer of bone cement (PMMA) or titanium (TI) with a smooth (∼1 μm) or roughened (∼8 μm) finish. After 4 weeks of implantation, the membranes were harvested, and the matrix composition, tensile mechanics, shrinkage, and barrier function was assessed. Roughening the spacers resulted in significantly more compliant membranes. TI spacers created membranes that inhibited solute transport more. There were no differences between groups in collagen or elastin distribution. This suggests that different membrane characteristics can be created by altering the spacer surface properties. Surgeons may unknowingly effecting membrane formation via bone cement preparation techniques.

Osteoclast inhibition by factors from cells associated with regenerative tissue

Guided tissue regeneration (GTR) uses expanded polytetrafluoroethylene (ePTFE) membranes to favor the repopulation of the healing wound with cells with bone regenerative potential. As bone remodeling is a tightly coupled process, inhibition of osteoclast-mediated bone resorption may be critical to regeneration. Thus, this study was undertaken to determine whether cells associated with regenerative tissue can inhibit osteoclast differentiation and activity and to begin characterizing and identifying the factor(s) mediating the observed effects. Conditioned media were harvested from human periodontal cell lines established in culture: cells adherent to ePTFE membranes, recovered from patients after GTR; cells adherent to ePTFE augmentation membranes, recovered from edentulous ridge augmentation procedures; and periodontal ligament cells from periodontally healthy bicuspids. Conditioned medium from each of these regenerative cell lines reduced the number of tartrate-resistant acid phosphatase-positive osteoclast-like cells formed from hemopoietic precursors in mouse bone marrow cultures. Also, both the total resorbed surface area and number of resorption pits formed by these cells on calcium phosphate ceramic films were reduced. The factor in the conditioned medium which inhibited osteoclast differentiation was soluble, heat labile, and resided in the lower molecular weight (< 30 kDa) fraction, the same fraction which would contain cytokines. Western blot analysis of the conditioned medium detected a band at the molecular weight of interferon gamma (IFN-gamma), using a polyclonal rabbit anti-human IFN-gamma. Thus, the factor in the conditioned medium with inhibitory activity may have identity with IFN-gamma or one of the other anti-inflammatory cytokines.

Light and electron microscopic observations of osteoclastic alveolar bone resorption in rats monoinfected with Actinomyces naeslundii

Alveolar bone destruction in rats monoinfected with Actinomyces naeslundii proceeds via osteoclastic resorption. The osteoclastic activity is discontinuous, i.e. short periods of vigorous osteoclastic activity are followed by longer periods of inactivity during which the alveolar crest may be covered with osteoblastic cells or in many cases devoid of bone cells. The net effect in the monoinfected rats is rapid bone loss. Periods of osteoclastic activity were associated with dense inflammatory infiltration of the interdental tissue, ulceration of col epithelium and the presence of large adherent plaques of Actinomyces. Ultrastructural examination revealed uninuclear as well as multinuclear osteoclasts. These cells contained numerous mitochondria, abundant Golgi apparatuses, and well developed ruffled borders indicating that they were physiologically active in bone resorption.

Organ culture of osteopetrotic (ia) rat bone: evidence that the defect is cellular

Calvarial bone from osteopetrotic (ia) rats and normal littermates has been cultured in a chemically defined medium supplemented with homologous serum to test for the presence of inhibitors or the absence of promoters of bone resorption in mutant serum. In addition, the response of mutant and normal bone to parathyroid extract and hydrocortisone was tested in vitro. The results indicate that mutant and normal serum do not differ with respect to their ability to support bone resorption and that ia bone responds to hydrocortisone but not parathyroid extract in organ culture. These data indicate that the skeletal defect in ia rats is not humoral but cellular.

Stimulation of bone resorption by various prostaglandins in organ culture

The ability of E, F, A and B prostaglandins to stimulate bone resorption was demonstrated in organ culture. All of the compounds tested were able to increase the release of previously incorporated 45Ca from fetal rat bone by 60 to 135 per cent at maximally effective doses, but prostaglandins of the E series were 10- to 100- fold more potent than F, A or B prostaglandins. Compounds with two double bonds in the side chain were usually more potent than those with one double bond. PGE2 stimulation of bone resorption increased linearly with the logarithm of the medium concentration over the range of 10(-9)M to 10(-5)M, then decreased at higher concentrations. PGE2 stimulated bone resorption more slowly than did parathyroid hormone but caused complete resorption after six days in the culture system. Equilibrium dialysis studies showed no significant binding of F, and 16-34% binding of E and A prostaglandins to bovine serum albumin, which was present in the medium at 1 mg/ml. These differences in albumin binding could not account for differences in potency.

Bone resorption in chronic otitis media. A light-microscopical and histochemical investigation of acid phosphatase activity

As a continuation of our previous work, where we have demonstrated that in chronic otitis media the picture in the submucosa-bone marginal zone is dominated by capillary proliferation and occurrence of a mononuclear, histiocyte-like cell containing lysosome-like cytoplasmatic bodies, we now report the presence of considerable activity of acid phosphatase in close relation to the eroded bone. The activity was localized both extracellularly, spread along the bony surface, as well as intracellularly in mononuclear, histiocyte-like cells. The acid phosphatase is the "marker" enzyme for lysosomes, and cells with these lysosomes guarantee the presence of enzymatic activity capable of attacking bone collagen. It is difficult to avoid the conclusion that the lysosomes and their enzymes are directly involved in the processes of bone resorption.