Different tartrate sensitivity and pH optimum for two isoenzymes of acid phosphatase in osteoclasts. An electron-microscopic enzyme-cytochemical study

Interactions of U937 macrophage-like cells with decellularized pericardial matrix materials: influence of crosslinking treatment

While macrophages have been implicated in the failure of bioprosthetic heart valves, the macrophage response to crosslinked native pericardial collagen has not been previously investigated. Using decellularized bovine pericardium (DBP) as a model for native collagen, this study investigated the response of macrophage-like cells (U937s) to DBP, either: (i) untreated, or (ii) exogenously crosslinked with glutaraldehyde or 1-ethyl-3-(3-dimethyl-aminopropyl)-carbodiimide (EDC). We have previously validated the use of U937 cells as models for the response of human monocyte-derived macrophages to decellularized pericardial materials and, per our previous work, differentiated the U937 cells directly on the three material surfaces. After 72h in culture, the cells and medium were analyzed for DNA content, acid phosphatase activity, and cytokine and matrix metalloproteinase release. As well, cell/substrate samples were fixed for SEM. Fewer cells attached to or survived on the glutaraldehyde-treated substrate, and some showed an abnormal morphology compared to cells cultured on the other surfaces. Further, cells on glutaraldehyde-treated surfaces released more pro-inflammatory cytokines, more MMP-1 and less MMP-2 and MMP-9. The poor performance of the U937 macrophage-like cells on the glutaraldehyde-treated surfaces appears to be due to surface characteristics rather than to soluble aldehyde or other components leaching from the crosslinked material. These results provide evidence that crosslinking with glutaraldehyde is cytotoxic to macrophage-like cells, and that crosslinking with a zero-length crosslinker like EDC can be an acceptable alternative crosslinking treatment for biomaterials.

Ultrastructural Cytochemical and Ultrastructural Morphological Differences Between Human Multinucleated Giant Cells Elicited by Wear Particles from Hip Prostheses and Artificial Ligaments at the Knee

The authors investigated the ultrastructural cytochemical features of multinucleated and mononuclear cells in periprosthetic tissues associated with bone resorption (osteolysis) and those in tissues adjoining failed artificial ligaments having no relation to bone resorption. Clinical specimens of granulation tissue of each type, respectively numbering 4 and 3, were stained for tartrate-resistant acid phosphatase (TRAP) reactions and examined by light and electron microscopy. Both periprosthetic granulation tissues and those adjoining artificial ligaments contained TRAP-positive multinucleated and mononuclear cells. Near joint prostheses, multinucleated cells, including some giant cells, showed TRAP activity and cytoplasmic features resembling osteoclasts, while others had features consistent with foreign-body giant cells, and still others showed degenerative changes. Near artificial ligaments, TRAP-positive multinucleated cells lacked osteoclastic features. At both sites, TRAP-positive multinucleated cells had phagocytised wear particles. TRAP-positive mononuclear cells at both sites also showed phagocytic cytoplasmic features, but not osteoclastic cytoplasmic features. Human mononuclear phagocytes and multinucleated giant cells induced by wear particles possess TRAP activity. Those multinucleated giant cells at sites of osteolysis developed osteoclastic cytoplasmic features and have a phagocytic function.

The interaction between hydrolytic and oxidative pathways in macrophage-mediated polyurethane degradation

Although relatively resistant to oxidation, polycarbonate-based polyurethanes (PCNUs) are degraded by monocyte-derived macrophages (MDM) by a co-mediated mechanism involving both hydrolytic and oxidative pathways. Since a previous study showed that PCNU pretreatment with H(2)O(2) modulated degradation by esterases, human MDM were used to further elucidate this dual pathway mechanism of degradation for (14)C-radiolabeled PCNUs (synthesized with 1,6-hexane diisocyanate:polycarbonatediol: butanediol with different stoichiometry (HDI431 and HDI321) or another diisocyanate 4,4'-methylene bisphenyl diisocyanate (MDI321)). Scanning electron microscopy of PCNU slips pretreated with 20% H(2)O(2) showed that HDI431 had visible holes with more radiolabel release than from the other PCNUs. When MDM were seeded on H(2)O(2)-treated PCNUs, degradation of HDI321 and MDI321, but not HDI431 was decreased. Esterase activity was inhibited in MDM on all surfaces except MDI321, whereas inhibition of acid phosphatase occurred on all surfaces. The material surface itself, induced H(2)O(2) release from live MDM, with more H(2)O(2) elicited by phorbol myristate acetate treated MDM when cultured on HDI431 but not the other materials. H(2)O(2) pretreatment affected cell function by chemically altering the material surface and MDM-mediated degradation, known to be dependent on surface chemistry. The findings highlight that both oxidative and hydrolytic mechanisms need to be understood in order to tailor material chemistry to produce desired cell responses for in vivo applications.

Cytodifferentiation of the odontoclast prior to the shedding of human deciduous teeth: an ultrastructural and cytochemical study

BACKGROUND

In human deciduous teeth, odontoclastic resorption takes place at the pulpal surface of the coronal dentine prior to shedding, and this resorption shows clear time-related histological changes (Sahara et al., 1992).

METHODS

Using this phenomenon as an observation system, we examined the cytodifferentiation of human odontoclasts by light and electron microscopy. For a histochemical marker of odontoclast differentiation and function, tartrate-resistant acid phosphatase (TRAP) activity was determined by light and electron microscopic enzyme histochemistry.

RESULTS

As root resorption neared completion, TRAP-positive mononuclear cells were initially detected in the pulp chamber. They had abundant mitochondria, small lysosomes, and moderately developed rough endoplasmic reticulum throughout their cytoplasm. In these mononuclear cells, TRAP activity was localized in compartments of the biosynthetic pathway, i.e., in cisternae of the endoplasmic reticulum and Golgi lamellae, as well as small lysosomes. The TRAP-positive mononuclear cells first made contact with the predentine surface by their elongated cellular processes. After attachment, they spread out along the predentine surface and developed specialized membrane structures, clear zones, and ruffled borders. Next, they fused with each other on the predentine surface and formed typical multinucleate odontoclasts. After termination of their resorption function, the odontoclasts lost their ruffled borders and became detached from the resorbed surface. Most of the detached odontoclasts had numerous large pale vacuoles and secondary lysosomes and appeared to be in the process of degeneration.

CONCLUSIONS

The present study demonstrates that: (1) odontoclasts differentiated from TRAP-positive mononuclear cells, which presumably originate from circulating progenitor cells, (2) membrane specialization of odontoclasts, i.e., development of a clear zone and ruffled border, is induced following their contact with the resorption surface, (3) multinucleation of odontoclasts takes place only after their attachment to the resorption surface, (4) mature multinucleate odontoclasts can resorb predentine as well as dentine in the same way as osteoclasts resorb bone, and (5) at the end of the resorption, odontoclasts gradually lose their ruffled borders and become detached from the resorbed surface.

Myeloblastic cell line expresses osteoclastic properties following coculture with marrow stromal adipocytes

Osteoclasts are derived from hemopoietic precursors in the marrow. Their differentiation pathway is still undefined, but an important role was observed for the marrow microenvironment in the regulation of osteoclastogenesis. Various marrow stromal cell subtypes were used to study their possible role in the formation of osteoclasts from myeloblast (M1) cells. Interactions between M1 cells and the 14F1.1 endothelial-adipocyte stromal cell line were demonstrated in a coculture model. M1 cells attached to the adherent layer of 14F1.1 cells and formed distinct foci reminiscente of "cobblestone areas." Following these interactions, M1 cells developed specific enzymatic activities and became multinucleated. Both mononuclear and multinuclear M1 cells became positive to tartrate-resistant acid phosphatase (TRaP) and ATPase, a feature characteristic of osteoclasts, and were also responsive to calcitonin. Furthermore, they attached to mineralized bone particles and their membrane changed into a ruffled border at the zone of interaction with the bone matrix. We thus demonstrated that marrow endothelial-adipocytes may play a role in regulating the differentiation of myeloblasts into osteoclasts.

Tartrate-resistant acid phosphatase accumulated in the matrix of developing medullary bone induced by estrogen treatment of male Japanese quail

Tartrate-resistant acid phosphatase (TRAP) in medullary bone matrix and bone cells was histochemically examined employing estrogen-induced medullary bone of male Japanese quail. Within 2 days after estrogen administration, medullary bone matrix was identified and the matrix and osteoblasts were negative for TRAP activity. Osteoclasts showing TRAP activity were occasionally seen. By 4 days, the projection of medullary bone trabeculae was seen and TRAP became positive in the deeper part of the bone matrix of trabeculae as well as the matrix located near cortical bone, but the surface areas and extending margins of medullary bone trabeculae were negative in activity. Osteoblasts were also negative for TRAP activity. By 7 days, TRAP-positive bone matrix conspicuously increased accompanying increment of bone volume, but TRAP-negative bone matrix was still seen at the surface areas or extending areas of the medullary bone trabeculae. Osteoblasts showed no reaction product. Osteoclasts showing TRAP activity increased in number. The results demonstrate that TRAP accumulates in medullary bone matrix with bone formation. Circumstantial evidence suggests that medullary bone osteoblasts may be involved in TRAP accumulation in the matrix despite their negative activity.

Tartrate resistant acid phosphatase activity in rat cultured osteoclasts is inhibited by a carboxyl terminal peptide (osteostatin) from parathyroid hormone-related protein

A carboxyl-terminal peptide sequence ("osteostatin") from parathyroid hormone related protein has been shown to have an inhibitory effect on osteoclastic bone resorption--an action opposite to its amino-terminal sequence. In this study, we proposed that inhibition of osteoclastic bone resorption by osteostatin was associated with reduction of tartrate resistant acid phosphatase (TRAcP) activity in osteoclasts. Our results have indicated that osteostatin reduced TRAcP activity in a dose dependent manner. This effect of osteostatin was both sensitive (half maximal effect approximately 5 x 10(-13) M) and potent (maximum inhibition approximately 50% of control). In the first 90 min of treatment, however, reduction of TRAcP activity was erratic but became persistent and progressive when the time course was extended. Moreover, throughout the experimental period the levels of TRAcP activity in the culture medium had fallen significantly. It appears that osteostatin has a biphasic effect on TRAcP activity, inhibiting its secretion and either suppressing its synthesis or increasing its degradation. In addition, osteostatin induced rapid cellular retraction of both human and rat cultured osteoclasts, which was morphologically distinct from that produced by calcitonin.

A histochemical study of acid phosphatases in medullary bone matrix and osteoclasts in laying Japanese quail

Acid phosphatase activity in medullary bone matrix and osteoclasts of laying Japanese quail was examined histochemically. To avoid nonspecific staining, the reactivity of the enzyme was evaluated using both the azo dye method and the lead salt method and nonembedded thick sections and resin-embedded thin sections. The pH of the incubation medium was also varied from the acid range (pH 5.0 and 6.5) to the alkaline range (pH 8.5). Medullary bone osteoclasts contain both tartrate-resistant acid phosphatase (TRAP) activity and fluoride-resistant acid phosphatase (FRAP) activity, and no significant difference in intensity was detected between active and inactive osteoclasts. The entire matrix of medullary bone was positive for tartrate-resistant, fluoride-sensitive acid phosphatase activity. No reaction product was observed in sections incubated in substrate-free and pH 8.5 media. The results demonstrate the existence of FRAP in medullary bone osteoclasts and suggest that medullary bone matrix includes TRAP throughout the matrix.

Ultrastructural and ultracytochemical characteristics of multinucleated cells after hydroxyapatite implantation into rat periodontal tissue

Multinucleated cells (MNCs) that appeared after hydroxyapatite (HAP) implantation into experimentally-produced bone defects in rat periodontal tissues were investigated both ultrastructurally and ultracytochemically. At day 5 after implantation, MNCs first appeared along the HAP surface. They had no features of typical osteoclasts such as ruffled border and clear zone. By d 14, these cells acquired features similar to osteoclasts, including ruffled border and clear zone. With the appearance of ruffled borders in MNCs, new bone deposited around the implanted HAP. MNCs appeared to excavate both newly-formed bone and implanted HAP simultaneously. Ingested HAP particles were observed not only in MNCs but also in macrophages. MNCs contained both tartrate-resistant acid phosphatase (ACPase) and carbonic anhydrase (CAase). ACPase activity was detected along all the biosynthesizing pathways in MNCs. Extracellular ACPase activity around the ruffled border region was also demonstrable. CAase activity could be detected only in the cytosol, vesicles and mitochondrial cristae of the MNCs. These cytochemical characteristics were almost the same regardless of the time elapsed after implantation.

Biphasic effect of calcitonin on tartrate-resistant acid phosphatase activity in isolated rat osteoclasts

Tartrate-resistant acid phosphatase (TRAP) has been implicated as being involved in osteoclastic bone resorption, and calcitonin (CT) is known to inhibit the resorptive process. This study investigates the kinetics of CT action on TRAP activity in isolated rat osteoclasts using both biochemical and quantitative cytochemical methods. The latter technique has been developed to detect very small changes in intracellular TRAP activity at the single-cell level. The biochemical study showed that 10(-9) M salmon CT (sCT) decreased TRAP activity in medium throughout the experimental period; TRAP activity in the cells was increased during the first 2 h but subsequently declined and was decreased to a significant level at 6 h. TRAP activity in sCT-treated osteoclasts measured by the cytochemical method showed significant increases within the first hour. This response was dose dependent between 10(-16) and 10(-11) M sCT with EC50 at 8 X 10(-14) M. After 1 h, the initial increase in intracellular TRAP activity in CT-treated osteoclasts was followed by a decline to below control levels, reaching statistical significance at 9 h. Treatment with forskolin (10(-5) M) showed a similar trend, suggesting that this response is mediated by cyclic AMP-regulated phosphorylation events. From these results, we conclude that CT has two actions on TRAP in isolated rat osteoclasts: the first to inhibit its release, the second to inhibit its synthesis and/or increase its degradation.

Osteoclasts: structure and function

Osteoclasts are multinucleated giant cells showing specialized membrane structures, clear zones and ruffled borders, which are responsible for the process of bone resorption. These cells arrive at the resorption site via the bloodstream as mononuclear cells, derived from haemopoietic precursors in the spleen or bone marrow, which fuse prior to resorption. The osteoclast may share an early progenitor cell, the granulocyte macrophage colony-forming unit (GM-CFU) with monocytes, macrophages and granulocytes, implying that osteoclasts share the pluripotent haemopoietic stem cell with all other haemopoietic cells. In the past, elucidation of the structure of these cells relied upon traditional ultrastructural techniques. Transmission electron microscopic studies revealed details of the unique ultrastructure of these cells and, in combination with stereological techniques, showed the response of cells to various hormonal stimuli. Scanning electron microscopy not only demonstrated the surface appearance of osteoclasts, and their predilection for spreading on various substratum components, but has also been used as an adjunct in resorption assays in which areas of resorption lacunae are measured as indicators of cell activity. Recent advances in fields such as immunocytochemistry and freeze fracture techniques have contributed towards a more detailed delineation of antigenic profile, cytoskeletal structure and localization of enzymatic pathways. The osteoclast is subject to extensive regulatory mechanisms and it has been established that the osteoblast plays a major rôle in mediating the effects of osteotropic hormones and local mediators on these cells. Hence, research aimed at elucidating the coupling mechanisms between these two cells may result in new therapies for bone disease.

Ultrastructural distribution of NADPase within the Golgi apparatus and lysosomes of mammalian cells

Cytochemical studies with over 40 different mammalian cell types have indicated that NADPase activity is associated with the Golgi apparatus and/or lysosomes of all cells. In the majority of cases, NADPase is restricted to saccular elements comprising the medial region of the Golgi stack and an occasional lysosome. There is often weak NADPase activity in other Golgi compartments such as the trans Golgi saccules and/or elements of the trans Golgi network. In some cells, however, strong NADPase activity is found within these latter compartments, either exclusively in trans Golgi saccules or elements of the trans Golgi network, or in combination with medial Golgi saccules and each other including (1) medial Golgi saccules + trans Golgi saccules, (2) medial Golgi saccules + trans Golgi saccules + trans Golgi network, or (3) trans Golgi saccules + trans Golgi network. In some rare cases, no NADPase activity is detectable in either Golgi saccules or elements of the trans Golgi network, but it is observed in an occasional lysosome or throughout the lysosomal system of these cells. It is unclear at present if these variations in the distribution of NADPase across the Golgi apparatus, and between the Golgi apparatus and lysosomal system, are due to differences in targeting mechanisms or to the existence of "bottlenecks" in the natural flow of NADPase along the biosynthetic pathway toward lysosomes. While no clear pattern in the association of strong NADPase activity with lysosomes was apparent relative to the ultrastructural distribution of NADPase activity in Golgi saccules or elements of the trans Golgi network, the results of this investigation suggested that cells having NADPase localized predominantly toward the trans aspect of the Golgi apparatus (in trans Golgi saccules or elements of the trans Golgi network or both) have few NADPase-positive lysosomes. The only exception is hepatocytes which were classified as predominantly trans but had noticeable NADPase activity within medial Golgi saccules and elements of the trans Golgi network as well, and highly reactive lysosomes. Other cells showing highly reactive lysosomes including (1) Kupffer cells of liver and those forming the proximal convoluted tubules of the kidney, both of which also had strong NADPase activity within medial and trans Golgi saccules and elements of the trans Golgi network, (2) Leydig cells of the testis and interstitial cells of the ovary, which also showed strong NADPase activity within medial Golgi saccules, and (3) macrophages from lung, spleen and testis, and Sertoli cells from the testis all of which showed no Golgi associated NADPase activity.(ABSTRACT TRUNCATED AT 400 WORDS)