Light microscopic localization of alkaline phosphatase in fetal bovine bone using immunoperoxidase and immunogold-silver staining procedures

High metabolic activity of tissue-nonspecific alkaline phosphatase not only in young but also in adult bone as demonstrated using a new histochemical detection protocol

Tissue-nonspecific alkaline phosphatase (TNAP) is playing a key role in bone calcification, as has been demonstrated in different mammalian species including human and rodents. However, to investigate age-related changes during life history, histochemical demonstration of TNAP is severely hampered, particularly in the elderly, by technical difficulties associated with sectioning calcified tissue. Sufficient fixation must precede decalcification since poorly fixed bone tissue is exposed to the deleterious effects of decalcification reagents. In order to find a method that would allow cryosectioning of bone without loss of TNAP activity, we assessed the efficacy of different fixation reagents regarding the effects on structural integrity and TNAP activity using liver and osseous tissue from younger and older horses. The results of this study reveal that glyoxal-based fixatives sufficiently preserved bone tissue for successful cryosectioning without compromising TNAP activity. The method described combines the demonstration of TNAP activity with optimal preservation of tissue morphology in osseous tissue of younger and even of older mammals. As a model species, we selected horse bones in light of potentially higher similarities to ageing history and lifelong locomotion in humans as compared to other, mostly smaller, experimental model species with a much shorter life span and artificial locomotive activity when kept in cages. This may serve as a basis for future studies addressing the impact of different life traits in iconic, domestic and companion animals, which are often patients in veterinary medicine, as well as for basic research on human physiology and pathologies of the musculoskeletal system.

Cellular and molecular changes in orthodontic tooth movement

Tooth movement induced by orthodontic treatment can cause sequential reactions involving the periodontal tissue and alveolar bone, resulting in the release of numerous substances from the dental tissues and surrounding structures. To better understand the biological processes involved in orthodontic treatment, improve treatment, and reduce adverse side effects, several of these substances have been proposed as biomarkers. Potential biological markers can be collected from different tissue samples, and suitable sampling is important to accurately reflect biological processes. This paper covers the tissue changes that are involved during orthodontic tooth movement such as at compression region (involving osteoblasts), tension region (involving osteoclasts), dental root, and pulp tissues. Besides, the involvement of stem cells and their development towards osteoblasts and osteoclasts during orthodontic treatment have also been explained. Several possible biomarkers representing these biological changes during specific phenomenon, that is, bone remodelling (formation and resorption), inflammation, and root resorption have also been proposed. The knowledge of these biomarkers could be used in accelerating orthodontic treatment.

Site-specific localization of two distinct phosphatases along the osteoblast plasma membrane: tissue non-specific alkaline phosphatase and plasma membrane calcium ATPase

In osteoblasts, alkaline phosphatase has been reported to be restricted to the basolateral domains. In recent studies, we have demonstrated phosphatase activities different from those of tissue non-specific alkaline phosphatase (TNSALP) along the osteoidal aspect of osteoblast membrane at alkaline and neutral pH on undecalcified freshly frozen sections of rat bones. In the present study, we sought to further characterize and define the nature of membrane-associated phosphatases along the osteoidal aspect of osteoblasts. Histochemical properties of the enzymes and their localization in vivo were examined in long bones of normal Wistar rats and TNSALP null mutant mice and their wild type littermates. Molecular profiles of the enzymes in the osteoblast extracts were also examined. The enzymatic activity of the phosphatase along the osteoidal surface of osteoblasts proved to be activated by both Mg2+ and Ca2+. Unlike TNSALP, the activity was inhibited by vanadate but resistant to levamisole, implicating a similarity between this enzyme and plasma membrane Ca2+ transport ATPase (PMCA). Immunohistochemistry showed that PMCA immunoreactions were restricted to the osteoidal domain of the plasma membrane. Native-PAGE analysis of osteoblast extracts suggested the presence of two phosphatases corresponding, respectively, to TNSALP and PMCA. Western blot analysis after SDS-PAGE of osteoblast extracts confirmed the existence of PMCA (140 kDa) and TNSALP (80 kDa). Gel-chemical analysis of the osteoblast extract from TNSALP null mutant mice depicted phosphatase activity, which was resistant to levamisole. These data suggest the presence of a phosphatase different from TNSALP, most plausibly PMCA, on the osteoidal surface of osteoblasts.

Alkaline phosphatase isozymes in insects and comparison with mammalian enzyme

Studies of insect alkaline phosphatases (ALPs) are reviewed, including general insect isozyme papers from earlier periods. Results of biochemical and genetic investigations of the silkworm midgut ALPs are described. The membrane-bound (m-ALP) and soluble form (s-ALP) are controlled by distinct genes on the same chromosome. These isozymes were different in tissue localization, antigenicity, stability under alkaline conditions and sugar chains. Compared with mammalian ALPs, silkworm ALPs represented specificity in the monomeric structure, tissue localization and inhibition by amino acids. The amino acid sequence deduced from cDNA sequence of silkworm m-ALP showed 42.7-44.6% homology to three human types of ALP. Comparison of the amino acid sequences in functionally important parts of various ALP isozymes showed a significant conservation. Physiological roles of ALPs were discussed and the significance of the study in temporal and spatial regulations of both silkworm ALP genes was pointed out. In addition, the evolutionary relationship among various genes was discussed.

Immunolocalization of alkaline phosphatase in osteoblasts and matrix vesicles of human fetal bone

A monoclonal antibody raised against alkaline phosphatase (ALP) of human osteosarcoma was used to localize this enzyme in human fetal bone tissue. For light microscopy, the presence of alkaline phosphatase in osteoblasts and osteocytes was demonstrated by use of an avidin-biotin immunoperoxidase procedure. Electron microscopic immunolocalization was accomplished with an indirect immunoperoxidase method which revealed a concentration of the enzyme on matrix vesicle and osteoblast plasma membranes. In addition, many vesicular protrusions arising from areas of plasma membrane on the lateral surfaces of adjacent osteoblasts were strongly immunolabeled. Immunostaining for ALP was absent in vesicles which contained fine crystallites. Alkaline-phosphatase-rich matrix vesicles may play a significant role in the mineralization of the extracellular matrix.

Increased matrix vesicle protein in rachitic rat epiphyseal growth plates

Extracellular, membrane-bound vesicles are widely regarded to be the initial site of calcification in a variety of tissues under normal and pathological conditions. Alkaline phosphatase is believed to play a vital role in this process by hydrolysing ester phosphates or mineral inhibitors, e.g. inorganic phosphates. In the present study, matrix vesicles from normal and rachitic rat growth plates were compared with regard to specific activity of alkaline phosphatase, total vesicle protein and ultrastructural distribution of alkaline phosphatase activity. Matrix vesicles were released from normal or rachitic growth plates by collagenase digestion and isolated by differential centrifugation. Enzyme cytochemical localization involving a cerium capture method was performed on vesicles collected by vacuum filtration on Millipore filters. SDS gels and Western blots on fractions of both normal and rachitic matrix vesicles showed major proteins to be almost identical and confirmed the presence of alkaline phosphatase in both. Total matrix vesicle protein ((mg total matrix vesicle protein/rat) x 10(2)) per rat was significantly greater for the rachitic animals (9.0 +/- 2.0 vs. 4.0 +/- 1.0), P less than 0.0001. Alkaline phosphatase specific activity (units alkaline phosphatase/mg vesicle protein) in the rachitic and normal matrix vesicles was 25.29 +/- 9.36 and 18.78 +/- 3.37, respectively (0.05 less than P less than 0.1). Electron dense cerium phosphate deposits were localized to the outer membrane surface of matrix vesicles derived from both types of rats. This data, the first to quantify the relationship between rickets, matrix vesicle protein and alkaline phosphatase specific activity, suggests that matrix vesicles from rachitic and normal rats have biochemical and morphological similarity.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunogold-silver labeling in histology

Immunogold-silver staining is a relatively new technique in light-microscopic immunocytochemistry. It is based on silver enhancement of 1 to 10 nm gold probes immunologically bound to antigenic determinants in tissue sections. The detection efficiency of this third-generation detection technique is compared to that of the peroxidase-based ABC technique in routinely processed, paraffin-embedded, human biopsy material.

Heterotopic ossification: a case report and immunohistochemical observations

This report describes the case of a 69-year-old man with adenocarcinoma of the transverse colon who developed heterotopic ossification in a metastatic axillary lymph node. The areas of pathologic bone formation were characterized by the appearance of osteoblast-like cells at the surfaces of the mineral deposits. Immunostaining for alkaline phosphatase revealed a significant concentration of this enzyme in these cells and, to a lesser degree, on the apical membrane of the glandular cells of the adenocarcinoma adjacent to the ossification centers. Proliferating mesenchymal cells in close proximity to the areas of osteogenesis also showed significant immunolabeling. We conclude that metastatic colonic carcinoma can promote heterotopic ossification, and that alkaline phosphatase is intimately associated with bone formation under these pathologic conditions.