A sensitive method for the detection of poly-A tails of mRNA using a biotin-labelled heteropolymer OF dT:rA

S100A8 and S100A9 in Human Arterial Wall

Atherogenesis is a complex process involving inflammation. S100A8 and S100A9, the Ca2+-binding neutrophil cytosolic proteins, are associated with innate immunity and regulate processes leading to leukocyte adhesion and transmigration. In neutrophils and monocytes the S100A8-S100A9 complex regulates phosphorylation, NADPH-oxidase activity, and fatty acid transport. The proteins have anti-microbial properties, and S100A8 may play a role in oxidant defense in inflammation. Murine S100A8 is regulated by inflammatory mediators and recruits macrophages with a proatherogenic phenotype. S100A9 but not S100A8 was found in macrophages in ApoE-/- murine atherosclerotic lesions, whereas both proteins are expressed in human giant cell arteritis. Here we demonstrate S100A8 and S100A9 protein and mRNA in macrophages, foam cells, and neovessels in human atheroma. Monomeric and complexed forms were detected in plaque extracts. S100A9 was strongly expressed in calcifying areas and the surrounding extracellular matrix. Vascular matrix vesicles contain high levels of Ca2+-binding proteins and phospholipids that regulate calcification. Matrix vesicles characterized by electron microscopy, x-ray microanalysis, nucleoside triphosphate pyrophosphohydrolase assay and cholesterol/phospholipid analysis contained predominantly S100A9. We propose that S100A9 associated with lipid structures in matrix vesicles may influence phospholipid-Ca2+ binding properties to promote dystrophic calcification. S100A8 and S100A9 were more sensitive to hypochlorite oxidation than albumin or low density lipoprotein and immunoaffinity confirmed S100A8-S100A9 complexes; some were resistant to reduction, suggesting that hypochlorite may contribute to protein cross-linking. S100A8 and S100A9 in atherosclerotic plaque and calcifying matrix vesicles may significantly influence redox- and Ca2+-dependent processes during atherogenesis and its chronic complications, particularly dystrophic calcification.

Macrophages at the skeletal tissue-device interface of loosened prosthetic devices express bone-related genes and their products

Aseptic loosening of prosthetic arthroplasty is the most common reason for implant failure in adult orthopaedic reconstruction. At the interface of aseptic loosened prostheses, there is an abundance of particle-activated macrophages and other inflammatory cells. The role of these particle-laden macrophages in the osteogenic arm of the remodeling skeleton in this pathological condition is poorly understood. Molecular signaling by mesenchymal cells and mononuclear inflammatory cells residing in the interfacial tissues between bone and cement or prosthetic material of aseptically loosened joint prostheses was studied using in situ hybridization and immunohistochemical techniques. We found that a range of collagenous and noncollagenous matrix proteins, including osteopontin, osteocalcin, bone sialoprotein, and type I collagen, were produced in the periprosthetic tissue by foamy macrophages, as well as nearby osteogenic cells. The former accumulated in profusion in the three zones of interfacial tissues: pseudomembranous, fibrous, and osseous. Spindle mesenchymal cells in the fibrous zone failed to express any of the osteogenic mRNAs or proteins sought. The expression of bone-related genes and proteins by foamy macrophages at the interface of an aseptic loosened prosthesis may contribute to the disturbance of bone remodeling at this site.

Differentiation of human bone-derived cells grown on GRGDSP-peptide bound titanium surfaces

Various surface modifications have been applied to titanium alloy (Ti-6Al-4V) implants, in an attempt to enhance osseointegration; crucial for ideal prosthetic fixation. Despite the numerous studies demonstrating that peptide-modified surfaces influence in vitro cellular behavior, there is relatively little data reporting their effects on bone remodeling. The objective of this article was to examine the effects of chemically modifying Ti-6Al-4V surfaces with a common RGD sequence, a 15-residue peptide containing GRGDSP (glycine-arginine-glycine-aspartate-serine-proline), on the modulation of bone remodeling. The expression of proteins known to be associated with osseous matrix and bone resorption were studied during the growth of human bone-derived cells (HBDC) on these peptide-modified surfaces. HBDC grown for 7 days on RGD surfaces displayed significantly increased levels of osteocalcin, and pro-collagen Ialpha1 mRNAs, compared with the production by HBDC grown on the native Ti-6Al-4V. A pattern that was also reflected at the protein levels for osteocalcin, type I collagen, and bone sialoprotein. Moreover, HBDC grown for 7 and 14 days on RGD-modified Ti-6Al-4V expressed significantly higher level of osteoclast differentiation factors and lower levels of osteoprotegerin and IL-6 proteins compared with other surfaces tested. These results suggest that different chemical treatments of implant material (Ti-6Al-4V) surface result in differential bone responses, not only their ability to form bone but also to stimulate osteoclastic formation.

Quantitative aspects of an in situ hybridization procedure for detecting mRNAs in cells using 96-well microplates

The universal quantitation of the DNA hybridization reaction has been a goal sought by many researchers. Part of this search has been the need to develop a rapid, sensitive, easy-to-perform, and quantitative method to measure the abundance of specific mRNAs directly within cells. Conventionally mRNA detection can be done by advanced quantitative in situ hybridization (ISH) using either image analysis or fluorescence in situ hybridization (FISH), or indirectly by extraction of mRNA from cells or tissue and using Northern blot or quantitative polymerase chain reaction (PCR). We examined the quantitative nature of probe binding to intracellular mRNA in a sensitive and easy-to-use nonisotopic method of ISH previously developed in our laboratories. The method is applicable to isolated primary cells or cells in culture. The procedural details are very simple, with cells being centrifuged into 96-well microplates, fixed with formalin, and pretreated with Triton X-100 and Nonidet P-40 before photobiotin-labeled cDNA probes are applied. Biotin from the hybridization of probe to target is detected using multiple applications of streptavidin and biotinylated alkaline phosphatase and visualized by the p-nitrophenyl phosphate conversion method. The quantitative parameters of the ISH procedure were determined by measuring the levels of expression of erythropoietin (EPO) mRNA and its translated protein in transfected COS-7 cells. There is a log-linear relationship between the levels of signal obtained in the ISH reaction in 96-well microplates and the EPO protein levels measured by enzyme-linked immunosorbent assay (ELISA). This demonstrated relationship is important in the standardization and use of these procedures to measure quantitatively mRNAs within cells.

Localization and Regulation of Thrombopoietin mRNA Expression in Human Kidney, Liver, Bone Marrow, and Spleen Using In Situ Hybridization

Thrombopoietin (TPO) is the primary hematopoietic growth factor involved in the regulation of platelet production. Although the kidney, liver, bone marrow (BM), and spleen have been identified as the major sources of TPO production, the precise cellular location of TPO mRNA expression in these tissues remains unknown. We have identified the cells expressing TPO mRNA in the human kidney, liver, and BM using an in situ hybridization assay. In the BM of individuals with normal platelet counts, the hybridization signal was too weak to allow identification of the TPO mRNA expressing cells. However, in thrombocytopenic subjects with aplastic anemia, postchemotherapy marrow aplasia, and immune thrombocytopenia, the stromal cells showed strong TPO mRNA expression. In the human subjects with normal platelet counts, the cells of the proximal convoluted tubules of the kidney showed consistent positive staining whereas the signal in the cells of the distal convoluted tubules was less consistent. Strong hybridization signal was also evident in the hepatocytes. The hybridization signal in the spleen, even in thrombocytopenic subjects, was too weak to allow confident identification of the cells expressing TPO mRNA. In all subjects, the interstitial cells and endothelial cells of the liver and spleen, the renal peritubular cells, and the hematopoietic precursor cells of the BM showed no TPO mRNA expression. Our data suggest that TPO mRNA expression in the human BM may be modulated by platelet mass.

Localization and Regulation of Thrombopoietin mRNA Expression in Human Kidney, Liver, Bone Marrow, and Spleen Using In Situ Hybridization

Thrombopoietin (TPO) is the primary hematopoietic growth factor involved in the regulation of platelet production. Although the kidney, liver, bone marrow (BM), and spleen have been identified as the major sources of TPO production, the precise cellular location of TPO mRNA expression in these tissues remains unknown. We have identified the cells expressing TPO mRNA in the human kidney, liver, and BM using an in situ hybridization assay. In the BM of individuals with normal platelet counts, the hybridization signal was too weak to allow identification of the TPO mRNA expressing cells. However, in thrombocytopenic subjects with aplastic anemia, postchemotherapy marrow aplasia, and immune thrombocytopenia, the stromal cells showed strong TPO mRNA expression. In the human subjects with normal platelet counts, the cells of the proximal convoluted tubules of the kidney showed consistent positive staining whereas the signal in the cells of the distal convoluted tubules was less consistent. Strong hybridization signal was also evident in the hepatocytes. The hybridization signal in the spleen, even in thrombocytopenic subjects, was too weak to allow confident identification of the cells expressing TPO mRNA. In all subjects, the interstitial cells and endothelial cells of the liver and spleen, the renal peritubular cells, and the hematopoietic precursor cells of the BM showed no TPO mRNA expression. Our data suggest that TPO mRNA expression in the human BM may be modulated by platelet mass.

Identification of mRNA-rich keratinocytes in the basal/suprabasal layers of psoriatic skin

In this study, we examined the relative amounts of mRNA expressed in normal versus psoriatic epidermis, using in situ hybridization with a biotinylated oligonucleotide poly d(T) probe. The hybridization image was analyzed by Laser Scanning Confocal Microscopy (LSCM). In normal human skin, hybridization signals were detected homogeneously throughout the epidermis, mostly in nucleus. These signals disappeared following RNase T2 or RNase A treatment, indicating that the target for this probe is RNA; by implication, mRNA. In psoriatic lesions, the overall signal intensity was significantly elevated, especially in the basal/suprabasal layers. Moreover, those signals were most prominent in the cytoplasm, not in the nucleus. In contrast, the signals of uninvolved epidermis adjacent to the psoriatic lesions were indistinguishable from those of normal skin in both signal intensity and hybridization profile. Our data are consistent with the notion that one of the characteristic features of psoriasis is an elevated (or uncontrolled) synthesis of mRNA and proteins.

Application of non-radiolabeled in situ hybridization system for the detection of polyadenylated RNA to normal and psoriatic human skin

The concentration and distribution of total mRNA is thought to reflect cellular activity. To clarify the distribution of total mRNA in normal and psoriatic human skin, in situ hybridization with a digoxigenin-labeled poly(dT) probe was carried out. In normal skin, polyadenylated RNA was distributed uniformly throughout the epidermis, including the basal, spinous, and granular layers. The nucleus and cytoplasm of skin appendages were stained more strongly than those of epidermal cells. The concentration of total mRNA in the epidermis of psoriatic skin was thought to be increased because of strong staining, especially in the basal layer, compared with that in normal epidermis, possibly reflecting hyperproliferation of keratinocytes. Results suggest that in situ hybridization with a poly(dT) probe is a useful strategy to study total mRNA distribution in human skin.

Expression of cytokeratin messenger RNA versus protein in the normal mammary gland and in breast cancer

It is not known how tightly regulation of cytokeratin (CK) protein expression is correlated with transcriptional activity in breast cancer. The level of control of CK expression in the normal mammary gland and in breast cancer has been assessed by combining in situ hybridization with riboprobes, and with immunohistochemistry using monospecific antibodies. In normal mammary gland, luminal cells showed abundant hybridization with complementary RNA (cRNA) probes for CK7, CK8, CK18, and CK19. Proteins of these CKs were correspondingly distributed except for that of CK19, which showed a heterogeneous staining. In primary carcinomas, both messenger RNAs (mRNAs) and proteins of CK8 and CK18 were generally expressed to a degree similar to that of normal epithelia, but a lower level of mRNA and protein of CK18 was observed in metastatic carcinomas. Reduced expression of CK7 and CK14 was observed in all carcinomas, and the correlation between mRNA and protein for these two cytokeratins was unbalanced, whereas the expression of CK19 mRNA and the proportion of its protein-positive cells were increased. The results suggest that these major CKs in normal mammary gland epithelia are regulated at the transcriptional level except for CK19, which is partially under the posttranscriptional control. The alterations observed in breast cancer are not only reflected by the reduced or increased expression of individual cytokeratins, but characterized by partial loss of the normal regulation of cytokeratin expression.

Quantitation of soluble and membrane-bound Fc gamma RIIA (CD32A) mRNA in platelets and megakaryoblastic cell line (Meg-01)

Fc gamma receptors (Fc gamma Rs) are glycoproteins on platelet surface that bind IgG-containing immune complexes. However, excessive binding of immune complexes leads to platelet activation and thrombosis or increased platelet clearance and thrombocytopenia. In this study, Fc gamma R transcripts in platelets and megakaryoblastic cell line (Meg-01) were investigated using specifically designed oligonucleotides and a new quantitative in situ hybridization assay. Platelets and Meg-01 cells were found to express only Fc gamma RII transcripts. Of Fc gamma RIIA mRNA isoforms (Fc gamma RIIA, B and C), Fc gamma RIIA mRNA predominates in these cells. Platelets and Meg-01 cells contain both alternative spliced forms of Fc gamma RIIA mRNA, those with and without the transmembrane (TM) exon and both forms were present in near equal amounts. In contrast, Fc gamma RIIA transcript with the TM exon predominates in neutrophils and monocytes, suggesting that the splicing of the TM exon is under lineage-specific control.

Idiotypic oligonucleotide probes to detect myeloma cells by mRNA in situ hybridization

An mRNA in situ hybridization (ISH) method which used non-radioactive idiotypic oligonucleotide probes has been used to detect malignant cells in the bone marrow and peripheral blood of patients with multiple myeloma. For each of two patients with multiple myeloma a pair of biotinylated antisense oligonucleotide probes (18-22mer) was prepared from non-germline sequences of the rear-ranged immunoglobulin heavy chain (IgH) gene. These oligonucleotide sequences were not homologous with any previously published sequence. The probes from each patient were specific as shown by a failure to hybridize to any cells from six other myeloma patients and four normal individuals. Specific staining of IgH gene mRNA occurred only when the myeloma cells and the sequence of the probe used were from the same patient. Using simultaneous fluorescent immunocytochemistry it was shown that more than 95% of the ISH-positive cells expressed the malignant light chain in their cytoplasm. ISH positive cells were found in 1-4% of the peripheral blood mononuclear fraction of these two patients. These studies show that idiotypic oligonucleotide IgH gene probes can be used to identify individual cells belonging to the malignant clone and offer the possibility of developing innovative tumour-specific therapeutic procedures using antisense technology for patients with myeloma.

The oncoprotein phenotype of plasma cells from patients with multiple myeloma

The expression of 6 different oncoproteins and 2 tumour suppressor gene products in the plasma cells of 63 bone marrow samples was used to determine a profile of the oncogenic phenotype of patients with multiple myeloma. Dual label flow cytometry after periodatelysine paraformaldehyde fixation was used to detect cell surface phenotype and intracellular protein expression simultaneously. The normal range for both the incidence and intensity of expression was determined for each protein by analysing plasma cells (high CD38 intensity) in 22 normal bone marrow samples. The percentage of myeloma patients with a greater than normal incidence of plasma cells expressing these proteins was 53% for c-myc, 28% for Rb, 28% for bcl-2, 27% for c-fos, 24% for p53 wild, 22% for p53 mutant, 13% for c-neu and 13% for pan-ras. When a panel of 8 antibodies was used, 82% of the samples (n = 28) had an increased incidence of expression by at least one oncoprotein or tumour suppressor gene product. The 5 patients with a normal incidence of expression of all 8 proteins were in plateau stage and 4 had not received chemotherapy for more than 12 months. The number of patients with an increased incidence of expression by 2 or more oncoproteins was significantly greater (X2 = 9.0; p < 0.005) in progressive disease (55%) than in stable disease (14%) but there was no specific phenotype pattern associated with progressive disease. All 6 oncoproteins and both tumour suppressor gene products had a greater incidence and intensity of expression in progressive than in stable disease. The expression of c-myc oncoprotein correlated with c-myc mRNA expression in the same samples (n = 10) but c-myc did not correlate with either the plasma cell labelling index (r = -0.15) nor serum thymidine kinase (r = 0.10). Our results suggest that there is a heterogeneous, non-systematic but almost universal presence of activated oncogenes and tumour suppressor genes in the plasma cells of patients with multiple myeloma and that disease progression is associated with the accumulation of a variety of secondary genetic changes which confer increased malignant behaviour.

Quantitation of Fc gamma RII mRNA in platelets and megakaryoblastic cell lines by a new method of in situ hybridization

We have developed a highly sensitive and quantitative, non-isotopic method of in situ hybridization in which the level of probe binding to intracellular mRNA is determined using an ELISA based detection method. Highly purified cell preparations or cells from a cultured cell line are centrifuged into 96 well microtiter plates. The cells are fixed with formalin and pre-treated with Triton X-100 and Nonidet P40 before photobiotin labeled cDNA probes are applied. The biotin from the hybridization is detected using multiple applications of streptavidin and biotinylated alkaline phosphatase and then visualized by the p-NPP (p-nitrophenyl phosphate) conversion method. We have determined a number of the optimal parameters in the procedure including the effects of cell numbers per well, development times and standardization of data using ubiquitous beta-actin mRNA and poly-A+ RNA expression as controls. We have used the technique to study the level of expression of FcgR mRNA in platelets and precursors. We found that platelets and megakaryoblastic cell lines only express mRNA for Fc gamma RII. The presence of the Fc gamma RII molecules was confirmed by complementary studies using immunohistochemistry with specific monoclonal antibodies IV.3 and KB61.