7 research outputs found
Ultrastructural evidence in vitro of osteoclast-induced degradation of calcium phosphate ceramic by simultaneous resorption and phagocytosis mechanisms
Osteoclasts are physiological polykaryons
specialized in the resorption of calcified tissue. In the
context of the clinical use of calcium-phosphate (Cap)
ceramics as bone substitutes, this study used
transmission electron microscopy to investigate the in
vitro mechanisms of Cap ceramic degradation by
osteoclastic cell types. Osteoclasts cultured on Cap
ceramic developed typical ultrastructural features of
bone osteoclasts, such as a polarized dome shape, a clear
zone and a ruffled border. Modification of the shape and
density of Cap crystals under the ruffled border
indicated an acidic microenvironment. Moreover,
osteoclasts were able to degrade ceramic by
simultaneous resorption and phagocytosis mechanisms.
Phagocytosis did not alter the ability of osteoclasts to
resorb Cap ceramic. The phagocytosis mechanism
consisted of three steps: crystal phagocytosis,
disappearance of the endophagosome envelope
membrane and fragmentation of phagocytosed crystals
within the cytoplasm. The common mechanism of
phagocytosis described here is similar to that observed
with the monocyte/macrophage lineage, confirming that
osteoclasts are part of the mononuclear phagocyte
system. Osteoclasts are thus clearly involved in Cap
degradation by means of resorption and phagocytosi
Bone remodelling and tumour grade modifications induced by interactions between bone and swarm rat chondrosarcoma
Chondrosarcoma is currently defined as a
malignant cartilage tumour arising de novo or within a
pre-existing benign cartilage tumour. Chondrosarcoma
can be surgically resected, but all grades have significant
rates of local recurrence. The purpose of the present
study was to develop an animal intraosseous
chondrosarcoma model simulating the progression of
human chondrosarcoma and elucidating its behaviour
and biology. An intraosseous Swarm rat model was
designed to assess interactions between bone and
chondrosarcoma. A comparison of tumour grading was
carried out according to transplantation site. The effects
of chondrosarcoma cells (SRC cells) on the
mineralisation capacities of osteoblasts and on osteoclast
differentiation were studied in relation to modifications
observed in vivo at the cellular level. Transplantation of
Swarm rat chondrosarcoma within bone marrow or
contiguous to induced periosteal lesions led to extensive
bone remodelling with trabecular bone rarefaction and
periosteal apposition. Transplantation in close contact to
bone but without any periosteal lesion had no effect on
bone, suggesting that bone healing factors interact with
tumour development. With the intramedullary model, the
development of tumours of different grade confirms that
bone environment is an important factor in malignancy.
A decrease of bone nodule formation was noted after cocultures
of SRC cells with rat bone marrow, but there
was no modification of osteoclast differentiation after
cultures of total rabbit bone cells with SRC cells. These
data reveal the importance of interactions between bone
environment and tumour in inducing bone remodelling and variations in tumour malignancy
Influence of metal ion solutions on rabbit osteoclast activities in vitro
The purpose of the present study was to
compare the effects of various metal ions (aluminium,
chromium, cobalt, gold, iron, strontium, titanium and
vanadium) on rabbit osteoclast activities, with respect to
their number, size, resorptive capacity and their capacity
to release proteinases. Marked heterogeneous
osteoclastic behaviour was observed early in culture
with metal ions (24 h) in term of resorption parameters.
In contrast, protease activities (cysteine-proteinase and
metalloproteinase activities) were not modulated in our
culture conditions. Aluminium, iron, gold and titanium
reduced the number of osteoclasts significantly.
Aluminium and gold had no effect on osteoclastmediated
resorption on dentin-slices, although
aluminium induced a greater number of very small
lacunae. Titanium reduced only the mean surface area
per lacunae, cobalt reduced the mean surface area of
lacunae and increased their number, and iron reduced
both parameters. Strontium had no effect on osteoclast
formation and on total dentin slice surface resorbed.
However, strontium increased the number of small
lacunae formed on dentin-slices by osteoclasts.
Chromium had no effect on osteoclast activities. These
findings indicate that metal ions induce very early
effects on osteoclasts, which can contribute to
periprosthetic pathologies via different cellular
mechanisms
Potential synergies between matrix proteins and soluble factors on resorption and proteinase activities of rabbit bone cells
Human growth hormone (GH) has recently
been found to stimulate osteoclastic resorption, cysteineproteinase
and metalloproteinase activities (MMP-2 and
MMP-9) in vitro via insulin-like growth factor-1 (IGF-1)
produced by stromal cells. The present study
investigated the effects of two extracellular matrix
components (vitronectin and type-1 collagen) on hGHand
hIGF-1-stimulated osteoclastic resorption and
proteinase activities in a rabbit bone cell model. After 4
days of rabbit bone cell culture on dentin slices with
vitronectin coating, hGH and hIGF-1 stimulated bone
resorption and hIGF-1 upmodulated cysteine-proteinase
activities. MMP-2 expression (but not resorption,
cathepsin or MMP-9 activities) was upmodulated by
hGH and hIGF-1 on dentin slices coated with type 1
collagen as compared to those without coating. Then,
vitronectin was synergistic with hIGF-1 in the regulation
of cysteine-proteinase production whereas collagen
showed synergy with hGH and hIGF-1 in the regulation
of MMP-2 production. Anti-avB3 totally abolished the
effects of hGH and hIGF-1 on metalloproteinase release,
but had no influence on cathepsin release. The results
suggest that cysteine-proteinase modulation is not
mediated by avB3 integrin (strongly expressed on
osteoclastic surface) whereas the resorption process and
metalloproteinase modulation are clearly'mediated by
this integrin. Our finding about the collagen coating also
suggests that hGH- and hIGF-1-stimulated MMP-2
activity are mediated, along with avB3 integrin, by
another adhesion molecule
The PHEMU09 catalogue and astrometric results of the observations of the mutual occultations and eclipses of the Galilean satellites of Jupiter made in 2009
Context. In 2009, the Sun and the Earth passed through the equatorial plane of Jupiter and therefore the orbital planes of its main satellites. It was the equinox on Jupiter. This occurrence made mutual occultations and eclipses between the satellites possible. Experience has shown that the observations of such events provide accurate astrometric data able to bring new information on the dynamics of the Galilean satellites. Observations are made under the form of photometric measurements, but need to be made through the organization of a worldwide observation campaign maximizing the number and the quality of the data obtained. Aims. This work focuses on processing the complete database of photometric observations of the mutual occultations and eclipses of the Galilean satellites of Jupiter made during the international campaign in 2009. The final goal is to derive new accurate astrometric data. Methods. We used an accurate photometric model of mutual events adequate with the accuracy of the observation. Our original method was applied to derive astrometric data from photometric observations of mutual occultations and eclipses of the Galilean satellites of Jupiter. Results. We processed the 457 lightcurves obtained during the international campaign of photometric observations of the Galilean satellites of Jupiter in 2009. Compared with the theory, for successful observations, the r.m.s. of O-C residuals are equal to 45.8 mas and 81.1 mas in right ascension and declination, respectively; the mean O-C residuals are equal to -2 mas and -9 mas in right ascension and declination, respectively, for mutual occultations; and -6 mas and +1 mas in right ascension and declination, respectively, for mutual eclipses. © ESO, 2014