The use of E. coli exonuclease III to generate single stranded DNA in BrdUrd cell-cycle analysis permits simultaneous detection of cell surface antigens

Ultraviolet-induced detection of halogenated pyrimidines: simultaneous analysis of DNA replication and cellular markers

BACKGROUND

We describe a new nonenzymatic methodology that allows the simultaneous detection of DNA replication and other cellular markers such as immunophenotyping. DNA replicating cells are identified by their incorporation of halogenated thymidine analogs, e.g., 5-bromo-deoxyuridine (BrdUrd).

METHODS

Irradiation with ultraviolet (UV)-B or UV-A light in the presence of Hoechst 33258 and subsequent treatment with a hypotonic buffer makes BrdUrd accessible to monoclonal antibodies (mAb), thus allowing its sensitive detection.

RESULTS

The photolysis of BrdUrd in DNA with UV light is sequence dependent and results in DNA damage, allowing the detection of remaining BrdUrd using hypotonic conditions. However, treatment with other inducers of single or double- strand breaks of DNA such as gamma irradiation or hydrogen peroxide did not allow BrdUrd detection. The new methodology is compatible with both mild crosslinking fixation, i.e., aldehydes, or coagulative fixation, i.e., alcohols. The successful identification of CD34+, CD138+, or CD19+ cells out of heterogeneous cell suspensions and their cell-cycle analysis are described. Results correlated very well with acid denaturation (r = 0.972). The average coefficient of variation (CV) of G(1) in the DNA histogram was smaller than 5%, resulting in good preservation of DNA distribution. Also, the signal-to-noise ratio was almost twice as high as for 2N acid denaturation, facilitating convenient discrimination of BrdUrd-positive cells.

CONCLUSIONS

In contrast to previous approaches, this methodology eliminates the need for any additional enzymatic treatment such as DNA digestion or strand-break labeling after UV irradiation. The method is fast, convenient, and inexpensive and should be able to promote the use of halogenated pyrimidines in basic and clinical research of cancer, immunology, and pharmacology.

Biocompatibility analysis of different biomaterials in human bone marrow cell cultures

A cell culture system for biocompatibility testing of hip implant materials is described. Human bone marrow cells have been chosen because these cells are in direct contact with the biomaterial after implantation in situ. The sensitivity of this method is evaluated for materials which are already being used as implants in humans and animal, e.g., hydroxyapatite (HA) ceramic, pure titanium, and ultra-high-molecular-weight polyethylene (UHMWPE). As indicative parameters of biocompatibility primary cell adherence, cell number, cell proliferation, production of extracellular matrix, cell vitality, and cell differentiation are described. After 2 weeks in culture, obvious differences between the biomaterials with respect to the indicative parameters could be observed. Cell numbers were greatest on the HA specimens. In the case of titanium alloys, we observed a decreased number of cells. The production of extracellular matrix was high for the HA ceramics but reduced for titanium specimens. The polymers allowed only a few adherent cells and showed no signs of extracellular matrix production. The results can be correlated astonishingly well to animal experiments and clinical experiences. Therefore, we suggest that this cell culture system seems to be a useful tool for biocompatibility testing of bone implantation materials. It also helps reduce animal experiments. With the help of flow cytophotometry, we analyzed the influence of biomaterials on large numbers of cells with respect to differentiation. There were similar populations of T cells and monocytes on all specimens tested. Extended B-cell and granulocyte populations, however, were observed with titanium and UHMWPE. Most osteocalcin-containing cells adhered to the HA ceramics.

Biocompatibility analysis of different biomaterials in human bone marrow cell cultures

A cell culture system for biocompatibility testing of hip implant materials is described. Human bone marrow cells have been chosen because these cells are in direct contact with the biomaterial after implantation in situ. The sensitivity of this method is evaluated for materials which are already being used as implants in humans and animal, e.g., hydroxyapatite (HA) ceramic, pure titanium, and ultra-high-molecular-weight polyethylene (UHMWPE). As indicative parameters of biocompatibility primary cell adherence, cell number, cell proliferation, production of extracellular matrix, cell vitality, and cell differentiation are described. After 2 weeks in culture, obvious differences between the biomaterials with respect to the indicative parameters could be observed. Cell numbers were greatest on the HA specimens. In the case of titanium alloys, we observed a decreased number of cells. The production of extracellular matrix was high for the HA ceramics but reduced for titanium specimens. The polymers allowed only a few adherent cells and showed no signs of extracellular matrix production. The results can be correlated astonishingly well to animal experiments and clinical experiences. Therefore, we suggest that this cell culture system seems to be a useful tool for biocompatibility testing of bone implantation materials. It also helps reduce animal experiments. With the help of flow cytophotometry, we analyzed the influence of biomaterials on large numbers of cells with respect to differentiation. There were similar populations of T cells and monocytes on all specimens tested. Extended B-cell and granulocyte populations, however, were observed with titanium and UHMWPE. Most osteocalcin-containing cells adhered to the HA ceramics.

Immunocytochemical analysis of mitogen responses of carp (Cyprinus carpio L.) peripheral blood leucocytes

Phytohaemagglutinin (PHA) and lipopolysaccharide (LPS) responses of surface immunoglobulin-positive (sIg+) and surface immunoglobulin-negative (sIg-) carp peripheral blood leucocytes (PBL) were studied. sIg+ cell-enriched and depleted carp PBL populations (sIg+ and sIg- cell fractions, respectively) were obtained by magnetic cell sorting (MACS) and mitogenic stimulation in vitro was measured by 3H-thymidine incorporation. The mitogen responses of sIg+ and sIg- cells in non-separated carp PBL cultures were analysed by simultaneous detection of incorporated 5-bromo-2'-deoxyuridine (BrdU) and sIg with the fluorescence microscope and flow cytometer. Flow cytometric determination of the percentage of sIg+ cells in combination with absolute cell counting, revealed an increase of sIg+ cells but not of sIg- cells after LPS stimulation while the number of sIg- cells and not of sIg+ cells was enhanced after PHA stimulation. LPS stimulation showed an increased 3H-thymidine incorporation in the sIg- cell fraction compared with non-separated cells and BrdU incorporation was observed in sIg- cells from LPS-stimulated cultures by fluorescence microscopy. However, flow cytometric analysis showed that mainly dull sIg+ cells and not sIg- cells are stimulated by LPS. These dull sIg+ cells were not sorted from sIg- cells with MACS and could apparently not be distinguished from sIg- cells by light microscopy. PHA stimulates sIg- cells and not sIg+ cells as was estimated by all techniques used.

Bromodeoxyuridine (BrdU) immunocytochemistry by exonuclease III (Exo III) digestion

A new procedure is described to generate single-stranded DNA by exonuclease III (Exo III) digestion for bromodeoxyuridine (BrdU) immunocytochemistry on tissue sections. We compared this procedure with the most widely used procedure of DNA denaturation with 2 N HCl. In vivo and in vitro pulse and continuous labelling of tissues and cells were used. The specimens were fixed in formalin, ethanol, glutaraldehyde, Carnoy's, Bouin's or Zamboni's fixative and embedded in paraffin or used unfixed as cryostat sections or cytospin preparations. After Exo III digestion, BrdU substituted DNA was detected irrespective of the fixation procedure applied. The optimal protocol for nuclease digestion appeared to be simultaneous incubation, of 10 Units Exo III per ml EcoRI buffer and anti-BrdU monoclonal antibody at 37 degrees C. The advantages of Exo III digestion for BrdU immunocytochemistry compared to acid denaturation were: less non-specific nuclear background reactivity, no DNA renaturation, less DNA loss, optimal nuclear morphology, increase in antibody efficiency and the possibility for simultaneous detection of acid-sensitive tissue constituents. Disadvantages of the Exo III digestion are decreased sensitivity and the need for more rigorous pepsin pretreatment. We conclude that Exo III digestion of DNA is an appropriate alternative for acid denaturation for BrdU immunocytochemistry on sections of pulse-labelled specimens.

Identification of DNA-replicating lymphocyte subsets using a new method to label the bromo-deoxyuridine incorporated into the DNA

A flow cytometric procedure measuring the 5-bromo-2-deoxyuridine incorporated into the DNA of cells in S phase was modified to make it compatible with the immunofluorescence labelling of cell surface antigens. The modifications were introduced at the stages of cell fixation and DNA denaturation. Ethanol was replaced by Tween 20-containing paraformaldehyde and hydrochloric acid was used for the denaturation of DNA by bovine pancreatic DNase-I. These two modifications permitted the preservation of immunofluorescence properties and the use of fluorochromes of the phycobiliprotein family such as phycoerythrin and allophycocyanin. This new procedure is suitable for evaluating leucocyte subsets proliferating in vitro following stimulation. As an illustration the immunosuppressive effect of cyclosporin A on PHA stimulated T4-lymphocytes was evaluated.

Simultaneous in situ hybridisation of native mRNA and immunoglobulin detection by conventional immunofluorescence in paraffin wax embedded sections

AIMS

The development of a technique for simultaneous in situ hybridisation for native mRNA and conventional immunofluorescence for cytoplasmic antigens in routine pathology specimens.

METHODS

Cocktails of synthetic deoxyoligonucleotides coding for immunoglobulin J chain and kappa light chain were 3' end labelled enzymatically with digoxigenin using terminal deoxynucleotidyl transferase. Native mRNA sequences were "unmasked" using proteolytic digestion with proteinase K and hybrid detection was achieved with an alkaline phosphatase labelled anti-digoxigenin antibody. Alkaline phosphatase was visualised with Fast red/naphthol AS-MX phosphate. Fluorescein isothiocyanate (FITC) conjugated anti-isotype antibodies were used simultaneously at the detection stage to identify the isotype production by individual plasma cells in endoscopic duodenal biopsy specimens.

RESULTS

The IgA plasma cells of the lamina propria were identified by immunofluorescence and hybrids were detected in the anticipated plasma cell population by Fast red visualisation. The reaction product was visible in bright field or ultraviolet illumination which allowed FITC and Fast red labels to be visualised together under ultraviolet light at 490 nm. Dual labelled cells were clearly visible. Morphology was well preserved throughout.

CONCLUSIONS

This technique permits the demonstration of specific mRNA species in cells expressing immunoglobulin. It combines all the advantages of non-radioactive synthetic oligonucleotide probes and conventional immunofluorescence techniques in routine formol-saline fixed and paraffin wax embedded sections with good retention of morphology.