Stable acid phosphatase: II. Effects of pH and inhibitors

Clinical and biological aspects of acid phosphatase

The identity and genetic origins of the nonspecific orthophosphate monoesterases with an acid pH optimum--the acid phosphatases--are now becoming clear. They form a family of genetically distinct isoenzymes, many of which show significant posttranslational modification. Four true isoenzymes exist. The erythrocytic and lysosomal forms show widespread distribution and are expressed in most cells; in contrast, the prostatic and macrophagic forms have a more limited expression. The erythrocytic and macrophagic forms are distinguished from the others in resisting inhibition by dextrorotatory tartrate. The prostatic form has long been used as a marker for prostatic cancer and the macrophagic forms have been linked with miscellaneous disorders, notably increased osteolysis, Gaucher's disease of spleen, and hairy cell leukemia, whereas the normal levels of intravesical lysosomal acid phosphatase in I cell disease pointed the way toward the mechanisms underlying its intracellular processing.

Histochemistry of tartrate-resistant acid phosphatase and carbonic anhydrase isoenzyme II in osteoclast-like giant cells in bone tumours

Using routinely processed, paraffin-embedded tissue specimens, osteoclast-like giant cells in giant cell tumour of bone (GCT), chondroblastoma, osteoblastoma and osteoblastic osteosarcoma were examined histochemically for osteoclast-specific enzymes tartrate-resistant acid phosphatase (TRAP) and carbonic anhydrase isoenzyme II (CA-II). Osteoclast-like giant cells and some mononuclear cells possessed TRAP activity. These were further classified with respect to CA-II immunoreactivity, i.e. cells with CA-II were seen in GCT and chondroblastoma, while those in osteoblastoma and osteoblastic osteosarcoma were negative for CA-II. All the cellular components in malignant fibrous histiocytoma and various extraosseous inflammatory lesions including malignant giant cells and macrophage polykaryons were negative for both TRAP and CA-II. These results indicate that osteoclast-like giant cells in GCT, chondroblastoma, osteoblastoma and osteoblastic osteosarcoma are all osteoclasts and generated by fusion of mononuclear cells with the same histochemical characteristics as osteoclast-like giant cells. The difference in CA-II immunoreactivity suggests the functional or maturational difference between osteoclast-like giant cells in GCT and chondroblastoma and those in osteoblastoma and osteosarcoma.

Local effects of impaired mechanical properties of collagen on bone formation and resorption

To study the relationship between the mechanical properties of collagen and the bone turnover, 2-week-old Balb/C mice were fed on a diet containing 0.25% Beta aminopropionitrile (B-APN), a potent inhibitor of collagen crosslink formation, for 3 weeks. Mandibular incisor socket was selected for the analysis of bone formation and resorption parameters. Plastic embedded sections stained with toluidine blue and cut at 4 microns were used to analyze the average area of bone lamellae, bone-forming surface, and the number of osteoblasts/mm of forming surface. Similar sections were used to localize acid phosphatase on resorbing surfaces and within the osteoclasts, while bone alkaline phosphatase was determined by a colorimetric method. Morphometric analyses showed that the area of newly formed bone lamellae, total forming surface, number of osteoblasts and the Alk. Pase activity were significantly lower in B-APN-fed mice as compared to the controls. There was a concomitant smaller, but significant, reduction in total resorption surface, active resorption surface and the number of osteoclasts. These results suggest that the regulation of bone formation and resorption at this site, which is independent of systemic regulation, is influenced by the mechanical properties of the collagenous matrix, which in turn may have a significant effect on the existing pool of bone-forming cells, but may not influence the recruitment of new cells.

Purification and characterization of a tartrate-resistant acid phosphatase from human osteoclastomas

Tartrate-resistant acid phosphatase is one of the major enzymes produced and secreted by osteoclasts. To obtain sufficient enzyme for biochemical characterization, we have purified this enzyme from human osteoclastomas by sequential chromatography on SP-Sephadex, CM-Sephadex, hydroxylapatite, Sephadex G-150 and concanavalin A-Sepharose. The purification over the original tumour extract was about 2000-fold, with a yield of 10%. The enzyme appeared to be homogeneous when assessed by SDS/polyacrylamide-gel electrophoresis. Both gel filtration and SDS/polyacrylamide-gel electrophoresis indicated an Mr of about 30,000. The reduced and alkylated enzyme consists of two subunits with Mrs of 15,000 and 17,500. The N-terminal amino acid sequence of both subunits indicates that there is a high degree of identity between the osteoclastoma enzyme and similar enzymes purified from spleen and uterus. Using 4-methylumbelliferyl phosphate as substrate, the specific activity of the purified enzyme was 387 units.mg-1, and the Km was 284 microns. The pH optimum was 5.7. Unlike similar enzymes purified from human and bovine bone, osteoclastoma acid phosphatase is not activated by reducing agents (2-mercaptoethanol or ascorbic acid). The enzyme contains 4.8 mol of Fe2+/3+, 0.3 mol of Mn2+ and 1.7 mol of Mg2+ per mol of enzyme. Although the enzyme loses 50% of its activity in the presence of EDTA, it is not inhibited by the iron chelator 1,10-phenanthroline. However, the enzyme is activated to a small extent by Mn2+ and Mg2+. Using a variety of substrates and inhibitors, we demonstrate that there are differences between the osteoclastoma acid phosphatase and the enzyme purified from other sources.

Evidence for osteoclast production in mixed bone cell culture

Osteoclastlike cells (OLCs) were recognized by their morphological, histochemical, and behavioral characteristics. These characteristics were initially observed in freshly isolated osteoclasts when neonatal rat bone cells were introduced into culture. Epithelioid cells proliferated during the first week to form a confluent layer. The cells' alkaline phosphatase content and ability to produce elevated levels of cyclic adenosine monophosphate in response to parathyroid hormone (PTH) led us to tentatively describe them as osteoblastlike cells. When a second addition of neonatal bone cells was made onto this confluent layer, OLCs were produced, their numbers increasing to a maximum 7 days later and dying out 3 weeks later. Mononuclear cells with similar characteristics to these multinuclear OLCs were observed and their production and disappearance closely paralleled that of the OLCs. Fusion of OLCs was observed. The conditions under which OLCs were produced are described.

Enzyme patterns in human endocytotic multinucleate giant cells--a histochemical study

A series of human multinucleate giant cells (MGCs) of the endocytotic type were studied using enzyme histochemical methods for dehydrogenases, glycosidases, phosphatases, and peptidases. Several enzyme patterns were found. The subgroup of MGCs associated with inflammatory granulomatous processes (sarcoidosis, granulomatous myositis, familial granulomatosis, lymphogranuloma, granulomatous cholangitis) was characterized by high activities of nonspecific esterase (NE) and tartrate-sensitive acid phosphatase (AcPase-Ts). There was no detectable activity of peptidases or tartrate-resistant isoenzyme of acid phosphatase (AcPase-Tr). This enzyme equipment was indistinguishable from that in mononuclear precursors in the granulomas. The other MGCs of the series displayed enzyme patterns substantially different from their monocytic precursors (blood monocytes and Langerhans cells). The subgroup of foreign body associated MGCs (resorption of fat, keratin, and suture material) was characterized by high activities of NE, AcPase-Tr, and greatly variable activities of both peptidases studied. The latter lacked predilection for certain subcellular regions. The subgroup of osteoclasts and so-called giant cell tumours (osteoclastoma, giant cell tumour of soft parts, giant cell epulis of peripheral, and central types) displayed very low activity of NE, high activity of AcPase-Tr, and strong activities of peptidases. The latter were localized near the surface membrane of the polykarya. MGCs in histiocytosis X (HX) differed from the previous group by higher values of NE in average. All MGC types had common denominator in the absence of alkaline phosphatase activity, on average intense dehydrogenase activities, mostly low beta-glucuronidase and highly variable alpha-mannosidase activities. The enzyme pattern heterogeneity is discussed with regard to the phenomenon of enzyme induction and depression occurring in course of polykaryon production. The variability of phenomenon may reflect reactive adaptation to varying functional demands imposed on MGCs under different conditions.

The pathobiology of the osteoclast

This article reviews recent information concerning the origin of osteoclasts and the local and systemic regulation of their activity. It appears that much of the environmental responsiveness of osteoclasts is mediated by cells of the osteoblastic lineage, which exert a major influence on the localisation, induction, stimulation, and inhibition of osteoclastic bone resorption. Some of the mechanisms by which osteoclast function may be disturbed by inflammatory and neoplastic diseases are discussed, and it is suggested that many pathological disturbances of osteoclastic bone resorption may be explicable as mimicry of physiological regulatory mechanisms by local hormones introduced into bone as the local regulators of the diseased tissue.

Staining of demineralized cartilage. I. Alcoholic versus aqueous demineralization at neutral and acidic pH

Demineralization of cartilage with alcoholic EDTA provides cartilage staining that is no better, as measured by scanning microdensitometry, than that of adequately fixed specimens demineralized with aqueous EDTA. Aqueous EDTA is a faster demineralizing agent than alcoholic EDTA. Certain fixatives can preserve maximal proteoglycan staining in articular cartilage even with subsequent rapid demineralization in formate buffer at pH 3.3. Although alcoholic formalin fixation provided optimum quantitative cartilage staining, cetylpyridinium chloride (CPC) in aqueous buffered formalin improved cellular detail, but CPC partially suppressed matrix staining.

Stable acid phosphatase: I. Demonstration and distribution

After a pH-dependent reactivation a highly stable form of acid phosphatase (SAPhase) could be demonstrated in active cells of the macrophage/giant cell/osteoclast series and also in epiphyseal chondrocytes, in cells lining bone undergoing resorption and in hamster eosinophils. Because acid phosphatases of epithelial cells in rat, hamster and Macaca sp. tissues did not possess this stability, SAPhase served as a useful cell marker for the above mesenchymal cell types in paraffin and glycol-methacylate sections even after rapid demineralization in acidic buffers. Conformational alterations appear to occur in the enzyme during formaldehyde fixation, embedding, and reactivation. The granular staining of SAPhase and the successful use of a non-aqueous fixative suggest an association of SAPhase with lysosomes and their membranes. Cells of mesencymal origin that are actively engaged in intra- and/or extracellular digestion contain high levels of SAPhase. The distribution and properties of SAPhase indicate an interrelationship between mononuclear and mutinuclear cell types actively engaged in such digestive processes.