Slices Of Human Bone Research Articles

Osteoclastogenesis of human peripheral blood, bone marrow, and cord blood monocytes

Osteoclasts are multinucleated bone resorbing cells that can be differentiated from human monocytes in vitro. There are few studies comparing osteoclastogenesis of different monocyte sources. We compared monocytes from human bone marrow (BM), peripheral blood (PB), and umbilical cord blood (CB) and their osteoclastogenic potential by culturing them with RANKL (20 and 80 ng/ml) and M-CSF (10 ng/ml) for 14 days. We also cultured cells without growth factors, as umbilical cord blood monocytes have been reported to be able to fuse spontaneously into osteoclasts. The data was analysed on d4, d8, d11, and d14. After culture with RANKL and M-CSF, all types of cell cultures developed TRACP -positive multinuclear cells that were able to form resorption pits on human bone slices. Only occasional multinuclear cells and small infrequent resorbed areas could be found in PB and CB-derived cultures without growth factors. BM-derived cells formed greater resorption areas than PB- and CB-derived monocytes. The greatest monocyte population in BM samples were intermediate (CD14++CD16+) and in PB and CB classical monocytes (76.3% and 54.4%, respectively). In conclusion, our data demonstrates that bone resorbing osteoclasts can be differentiated from BM, PB and CB. However, the osteoclast precursor origin can affect the osteoclast properties and function.

Gap junctional communication is involved in differentiation of osteoclasts from bone marrow and peripheral blood monocytes

AimsThe aim of the study was to compare the influence of gap junctional communication (GJC) in osteoclastogenesis from bone marrow (BM) and peripheral blood (PB) monocytes. These widely used sources differ in purity, since BM cultures contain a significant number of stromal cells. We studied whether stimulation of GJC in BM monocyte/stromal cell cultures differs from the effect in pure PB monocyte cultures. We compared the differentiation also in acidosis, which is a known inducer of bone resorption. Main methodsHuman BM and PB monocytes were isolated from BM aspirates or whole blood samples. The cells were cultured on human bone slices with osteoclastogenic growth factors and a GJC modulator, antiarrhythmic peptide AAP10, at physiological and acidic pH. Key findingsBoth BM and PB monocytes differentiated into osteoclasts. Acidosis increased resorption in both cultures but stimulated cell fusion only in BM cultures, which demonstrates the role of stromal cells in osteoclastogenesis. At physiological pH, AAP10 increased the number of multinuclear cells and bone resorption in both BM and PB cultures indicating that GJC is involved in differentiation in both of these osteoclastogenesis assays. Interestingly, in PB cultures at pH 6.5 the stimulation of GJC with AAP10 inhibited both osteoclastogenesis and bone resorption suggesting a different role of GJC in BM and PB monocytes at stressed environment. SignificanceThe study is conducted with primary human tissue samples and adds new knowledge on factors affecting osteoclastogenesis from different monocyte sources.

Integrin αMβ2 is differently expressed by subsets of human osteoclast precursors and mediates adhesion of classical monocytes to bone

Bone-degrading osteoclasts are formed through fusion of their monocytic precursors. In the population of human peripheral blood monocytes, three distinct subsets have been identified: classical, intermediate and non-classical monocytes. We have previously shown that when the monocyte subsets are cultured on bone, significantly more osteoclasts are formed from classical monocytes than from intermediate or non-classical monocytes. Considering that this difference does not exist when monocyte subsets are cultured on plastic, we hypothesized that classical monocytes adhere better to the bone surface compared to intermediate and non-classical monocytes. To investigate this, the different monocyte subsets were isolated from human peripheral blood and cultured on slices of human bone in the presence of the cytokine M-CSF. We found that classical monocytes adhere better to bone due to a higher expression of the integrin αMβ2 and that their ability to attach to bone is significantly decreased when the integrin is blocked. This suggests that integrin αMβ2 mediates attachment of osteoclast precursors to bone and thereby enables the formation of osteoclasts.

Distribution of Pb and Zn in slices of human bone by synchrotron µ‐XRF

AbstractSynchrotron radiation‐induced micro x‐ray fluorescence analysis (µ‐XRF) at HASYLAB beamline L was used to determine the distribution of Pb and other trace elements in slices of human bone. Using a focused synchrotron x‐ray beam of about 15 µm in diameter it was found that Pb was mostly located at the outer border of the cortical bone in various samples. Ratios of Pb intensities of cortical and trabecular bone varied from 0.027 for hip head to 0.408 for proximal tibia. Additionally Ca, Zn and Sr distributions were simultaneously recorded. A remarkable association between Pb and Zn content could be observed. Copyright © 2004 John Wiley & Sons, Ltd.

The N-terminal fragment of osteocalcin is released during osteoclastic bone resorption in vitro

As a novel method for measuring bone resorption, an immunoassay system for human N-terminal osteocalcin (N-OC) was developed to determine if osteocalcin molecules are released from bone degraded by osteoclasts in vitro. The assay system employed a monoclonal antibody to the first 20 N-terminal residues of osteocalcin as the solid phase and polyclonal antibodies against these same residues as an enzyme conjugate. This assay system could detect the N-terminal portion of osteocalcin formed during the degradation of the human osteocalcin molecule by trypsin or cathepsin D. Osteoclasts were isolated from human alveolar bone and cultured on human bone slices; the osteocalcin content in the media from these cultures was measured by this N-OC assay method. The N-terminal fragment of osteocalcin was the major form of osteocalcin released during osteoclastic bone resorption along with small amounts of intact osteocalcin. Interleukin-1 (IL-1β) and interleukin-6 (IL-6), stimulators of osteoclastic bone resorption, increased the N-OC level by 1.5 fold compared with the level of N-OC in osteoclast cultures in the absence of stimulators. In contrast, treatment of the cultures with calcitonin or an inhibitor of cathepsin D (E-64), both of which inhibit osteoclastic bone resorption, decreased the amount of N-OC in the culture supernatants. These results suggest that the N-terminal fragment of osteocalcin is released during osteoclastic bone resorption and that its level may serve as an index of bone resorption in vitro.