A model of osteoblast–osteocyte kinetics in the development of secondary osteons in rabbits

Pazzaglia, U. E.; Congiu, Terenzio; Franzetti, Eleonora; Marchese, Marcella; Spagnuolo, Francesco; Mascio, Livio Di; Zarattini, Guido

doi:10.1111/j.1469-7580.2012.01477.x

Cited by 18 publications

(26 citation statements)

References 35 publications

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“…It is also consistent with the concept that osteocyte domain is derived from the architecture of the osteonal lacunar‐canalicular system (Pazzaglia et al. ,b; Pazzaglia & Congiu, ). However, when a complete roof for the lacuna has been built, any further apposition outside of the lacuna by the osteocyte itself is not possible.…”

Section: Discussionsupporting

confidence: 90%

“…This does not imply that the endosteal entrapment index calculated in rabbit femur would be the same inside cortical osteons or human bones, since geometric parameters differ (Pazzaglia et al. ,c; Pazzaglia & Congiu, ). Likewise, there is no evidence that the bone apposition rate would be the same in all the other sites of tubular bones, such as the periosteum, endosteum and cortical cutting cones (Rauch et al.…”

Section: Discussionmentioning

confidence: 98%

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Osteoblast‐osteocyte transformation. A SEM densitometric analysis of endosteal apposition in rabbit femur

et al. 2013

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Transformation of osteoblasts into osteocytes is marked by changes in volume and cell shape. The reduction of volume and the entrapment process are correlated with the synthesis activity of the cell which decreases consequently. This transformation process has been extensively investigated by transmission electron microscopy (TEM) but no data have yet been published regarding osteoblast-osteocyte dynamic histomorphometry. Scanning electron microscope (SEM) densitometric analysis was carried out to determine the osteoblast and open osteocyte lacunae density in corresponding areas of a rabbit femur endosteal surface. The lining cell density was 4900.1 AE 30.03 n mm À2 , the one of open osteocyte lacunae 72.89 AE 22.55 n mm À2. This corresponds to an index of entrapment of one cell every 67.23 osteoblasts (approximated by defect). The entrapment sequence begins with flattening of the osteoblast and spreading of equatorial processes. At first these are covered by the new apposed matrix and then also the whole cellular body of the osteocyte undergoing entrapment. The dorsal aspect of the cell membrane suggests that closure of the osteocyte lacuna may be partially carried out by the same osteoblast-osteocyte which developed a dorsal secretory territory. A significant proportion of the endosteal surface was analysed by SEM, without observing any evidence of osteoblast mitotic figures. This indicates that recruitment of the pool of osteogenic cells in cortical bone lamellar systems occurs prior to the entrapment process. No further additions occurred once osteoblasts were positioned on the bone surface and began lamellar apposition. The number of active osteoblasts on the endosteal surface exceeded that of the cells which become incorporated as osteocytes (whose number was indicated by the number of osteocyte lacunae). Therefore such a balance must be equilibrated by the osteoblasts' transformation in resting lining cells or by apoptosis. The current work characterised osteoblast shape changes throughout the entrapment process, allowing approximate calculation of an osteoblast entrapment index in the rabbit endosteal cortex.

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Section: Discussionsupporting

confidence: 90%

Section: Discussionmentioning

confidence: 98%

Osteoblast‐osteocyte transformation. A SEM densitometric analysis of endosteal apposition in rabbit femur

et al. 2013

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“…Therefore all the osteoblasts recruited from the vascular loop are committed to bone apposition and finally to entrapment without further cell addition in the osteon refilling (Pazzaglia et al. ). In a recent study carried out in diaphyses of equine and canine long bones using functions that describe the probability of finding two canals separated by a given distance and the shortest distance distribution, Shabar et al.…”

Section: Discussionmentioning

confidence: 99%

“…However, the idea that all the osteoblasts become osteocytes and no osteoblasts are lost was not confirmed in a 2‐D model of osteoblasts–osteocyte kinetics in rabbit osteons (Pazzaglia et al. ). The time taken for refilling, however, has never been measured.…”

Section: Discussionmentioning

confidence: 99%

Morphometric analysis of osteonal architecture in bones from healthy young human male subjects using scanning electron microscopy

et al. 2013

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The shape and structure of bones is a topic that has been studied for a long time by morphologists and biologists with the goal of explaining the laws governing their development, aging and pathology. The osteonal architecture of tibial and femoral mid-diaphyses was examined morphometrically with scanning electron microscopy in four healthy young male subjects. In transverse sections of the mid-diaphysis, the total area of the anterior, posterior, lateral and medial cortex sectors was measured and analysed for osteonal parameters including osteon number and density, osteon total and bone area and vascular space area. Osteons were grouped into four classes including cutting heads (A), transversely cut osteons (B), longitudinally cut osteons (C) and sealed osteons (D). The morphometric parameters were compared between the inner (endosteal) and outer (periosteal) half of the cortex. Of 5927 examined osteons, 24.4% cutting heads, 71.1% transversely cut osteons, 2.3% longitudinally cut osteons and 2.2% sealed osteons were found. The interosteonic bone (measured as the area in a lamellar system that has lost contact with its own central canal) corresponded to 51.2% of the endosteal and 52.4% of the periosteal half-cortex. The mean number of class A cutting heads and class B osteons was significantly higher in the periosteal than in the endosteal half-cortex (P < 0.001 and P < 0.05, respectively), whereas there was no significant difference in density. The mean osteon total area, osteon bone area and vascular space area of both classes A and B were significantly higher (P < 0.001 for all three parameters) in the endosteal than in the periosteal half-cortex. The significant differences between the two layers of the cortex suggest that the osteoclast activity is distributed throughout the whole cortical thickness, with more numerous excavations in the external layer, but larger resorption lacunae closer to the marrow canal. A randomly selected population of 109 intact class B osteons was examined at higher magnification (350×) to count osteocyte lacuna and to analyse their relationship with osteon size parameters. The distribution frequency of the mean number of osteocyte lacunae increased with the increment in the sub-classes of osteon bone area, whereas the density did not show significant differences. The number of osteocyte lacunae had a direct correlation with the osteon bone area and the mean osteon wall thickness, as well as the mean number of lamellae. The osteocyte lacunae density showed an inverse relationship. These data suggest a biological regulation of osteoblast activity with a limit to the volume of matrix produced by each cell and proportionality with the number of available cells in the space of the cutting cone (total osteon area). The collected data can be useful as a set of control parameters in healthy human bone for studies on bone aging and metabolic bone diseases.

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“…In this study, the assessment of bone architecture, determined by osteocyte numbers and the preferential alignment of biological apatite (BAp) c ‐axis and collagen fibers, was performed for the evaluation of bone quality. Osteocyte numbers in osteocytic lacunae were counted because osteocytes are detectable in resin‐embedded samples with toluidine blue staining using BZ‐9000 with higher magnification . The area around the implant neck, where the original cortical bone would be located, was used to investigate osteocyte numbers and alignment of collagen fibers (AOI; 500 μm × 500 μm).…”

Section: Methodsmentioning

confidence: 99%

Structural and Qualitative Bone Remodeling Around Repetitive Loaded Implants in Rabbits

Kuroshima

Yasutake

Tsuiki

et al. 2015

Clin Implant Dent Rel Res

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A model of osteoblast–osteocyte kinetics in the development of secondary osteons in rabbits

Cited by 18 publications

References 35 publications

Osteoblast‐osteocyte transformation. A SEM densitometric analysis of endosteal apposition in rabbit femur

Osteoblast‐osteocyte transformation. A SEM densitometric analysis of endosteal apposition in rabbit femur

Morphometric analysis of osteonal architecture in bones from healthy young human male subjects using scanning electron microscopy

Structural and Qualitative Bone Remodeling Around Repetitive Loaded Implants in Rabbits

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