Immunofluorescence-guided segmentation of three-dimensional features in micro-computed tomography datasets of human lung tissue

Micro-computed tomography (µCT) provides non-destructive three-dimensional (3D) imaging of soft tissue microstructures. Specific features in µCT images can be identified using correlated two-dimensional (2D) histology images allowing manual segmentation. However, this is very time-consuming and requires specialist knowledge of the tissue and imaging modalities involved. Using a custom-designed µCT system optimized for imaging unstained formalin-fixed paraffin-embedded soft tissues, we imaged human lung tissue at isotropic voxel sizes less than 10 µm. Tissue sections were stained with haematoxylin and eosin or cytokeratin 18 in columnar airway epithelial cells using immunofluorescence (IF), as an exemplar of this workflow. Novel utilization of tissue autofluorescence allowed automatic alignment of 2D microscopy images to the 3D µCT data using scripted co-registration and automated image warping algorithms. Warped IF images, which were accurately aligned with the µCT datasets, allowed 3D segmentation of immunoreactive tissue microstructures in the human lung. Blood vessels were segmented semi-automatically using the co-registered µCT datasets. Correlating 2D IF and 3D µCT data enables accurate identification, localization and segmentation of features in fixed soft lung tissue. Our novel correlative imaging workflow provides faster and more automated 3D segmentation of µCT datasets. This is applicable to the huge range of formalin-fixed paraffin-embedded tissues held in biobanks and archives.

Small airways disease in mild and moderate chronic obstructive pulmonary disease: a cross-sectional study

BACKGROUND

The concept that small conducting airways less than 2 mm in diameter become the major site of airflow obstruction in chronic obstructive pulmonary disease (COPD) is well established in the scientific literature, and the last generation of small conducting airways, terminal bronchioles, are known to be destroyed in patients with very severe COPD. We aimed to determine whether destruction of the terminal and transitional bronchioles (the first generation of respiratory airways) occurs before, or in parallel with, emphysematous tissue destruction.

METHODS

In this cross-sectional analysis, we applied a novel multiresolution CT imaging protocol to tissue samples obtained using a systematic uniform sampling method to obtain representative unbiased samples of the whole lung or lobe of smokers with normal lung function (controls) and patients with mild COPD (Global Initiative for Chronic Obstructive Lung Disease [GOLD] stage 1), moderate COPD (GOLD 2), or very severe COPD (GOLD 4). Patients with GOLD 1 or GOLD 2 COPD and smokers with normal lung function had undergone lobectomy and pneumonectomy, and patients with GOLD 4 COPD had undergone lung transplantation. Lung tissue samples were used for stereological assessment of the number and morphology of terminal and transitional bronchioles, airspace size (mean linear intercept), and alveolar surface area.

FINDINGS

Of the 34 patients included in this study, ten were controls (smokers with normal lung function), ten patients had GOLD 1 COPD, eight had GOLD 2 COPD, and six had GOLD 4 COPD with centrilobular emphysema. The 34 lung specimens provided 262 lung samples. Compared with control smokers, the number of terminal bronchioles decreased by 40% in patients with GOLD 1 COPD (p=0·014) and 43% in patients with GOLD 2 COPD (p=0·036), the number of transitional bronchioles decreased by 56% in patients with GOLD 1 COPD (p=0·0001) and 59% in patients with GOLD 2 COPD (p=0·0001), and alveolar surface area decreased by 33% in patients with GOLD 1 COPD (p=0·019) and 45% in patients with GOLD 2 COPD (p=0·0021). These pathological changes were found to correlate with lung function decline. We also showed significant loss of terminal and transitional bronchioles in lung samples from patients with GOLD 1 or GOLD 2 COPD that had a normal alveolar surface area. Remaining small airways were found to have thickened walls and narrowed lumens, which become more obstructed with increasing COPD GOLD stage.

INTERPRETATION

These data show that small airways disease is a pathological feature in mild and moderate COPD. Importantly, this study emphasises that early intervention for disease modification might be required by patients with mild or moderate COPD.

FUNDING

Canadian Institutes of Health Research.

MicroRNA-328 is involved in wound repair process in human bronchial epithelial cells

Our aim was to investigate the role of microRNA on epithelial wound repair by global microRNA silencing. We have also analysed the influence of five miRNAs (miR-328, miR-342, miR-411, miR-609, miR-888, previously identified) on wound repair in 16HBE14o-bronchial epithelial cell line. Cells were transfected with siRNAs against human DROSHA and DICER1 or miRNA mimics or inhibitors. Wounding assays were performed and the cells were observed using time-lapse microscopy. The area of damage was calculated at chosen time points, followed by data analysis. Cells with silenced global miRNA expression showed a significantly slower repair rate compared to the control cells (p=0.001). For miR-328, we observed significantly delayed repair in cells transfected with the inhibitor compared to control (p=0.02). Global microRNA silencing significantly decreased the repair rate of airway epithelial cells in vitro, indicating an important role of miRNA in the regulation of wound repair and that miR-328, possibly involved in actin pathway, may be a potent modifier of this process.

Accuracy of diagnostic testing in primary ciliary dyskinesia

Diagnosis of primary ciliary dyskinesia (PCD) lacks a “gold standard” test and is therefore based on combinations of tests including nasal nitric oxide (nNO), high-speed video microscopy analysis (HSVMA), genotyping and transmission electron microscopy (TEM). There are few published data on the accuracy of this approach.

Using prospectively collected data from 654 consecutive patients referred for PCD diagnostics we calculated sensitivity and specificity for individual and combination testing strategies. Not all patients underwent all tests.

HSVMA had excellent sensitivity and specificity (100% and 93%, respectively). TEM was 100% specific, but 21% of PCD patients had normal ultrastructure. nNO (30 nL·min⁻¹ cut-off) had good sensitivity and specificity (91% and 96%, respectively). Simultaneous testing using HSVMA and TEM was 100% sensitive and 92% specific.

In conclusion, combination testing was found to be a highly accurate approach for diagnosing PCD. HSVMA alone has excellent accuracy, but requires significant expertise, and repeated sampling or cell culture is often needed. TEM alone is specific but misses 21% of cases. nNO (≤30 nL·min⁻¹) contributes well to the diagnostic process. In isolation nNO screening at this cut-off would miss ∼10% of cases, but in combination with HSVMA could reduce unnecessary further testing. Standardisation of testing between centres is a future priority.

Combination testing in PCD diagnosis remains the most accurate approach, but standardisation is neededhttp://ow.ly/TLEDu

Increased conjunctival expression of protease activated receptor 2 (PAR-2) in seasonal allergic conjunctivitis: a role for abnormal conjunctival epithelial permeability in disease pathogenesis?

AIMS

Aeroallergen exposure to the conjunctival epithelium in seasonal allergic conjunctivitis (SAC) may induce a cellular stress response that disrupts the barrier properties of the conjunctival epithelium, resulting in allergic disease. Whether such changes occur in SAC is unknown. Epithelial permeability is known to be increased when protease activated receptor 2 (PAR-2) is activated. We evaluated the expression of PAR-2 in patients with SAC-in-season (SACS) and compared it with control non-atopic subjects or those with out-of-season allergic conjunctivitis (OSAC).

METHODS

Six SACS, eight normal and four OSAC specimens were examined immunohistochemically for PAR-2 and quantified in a masked fashion for the percentage of epithelia stained for each marker using Image-J software. Conjunctival epithelial heights were measured in all groups to confirm the presence of allergic eye disease.

RESULTS

Mean percentage staining of PAR-2 was significantly greater in SACS that in normal specimens (73.4 ± 15.4% vs 32.8 ± 30.0%, p=0.038) or in OSAC (73.4 ± 15.4% vs 1.4 ± 2.2%, p=0.01). Mean conjunctival epithelial height was significantly raised in SACS (63.8 ± 9.0 μm) versus controls (44.7 ± 11.2 μm) (p=0.003, unpaired t test).

CONCLUSIONS

Conjunctival epithelial PAR-2 is significantly upregulated in SAC. This supports the view that disruption of the barrier properties of the conjunctival epithelium is an important event in SAC pathogenesis.

Identification of FOXP1 and SNX2 as novel ABL1 fusion partners in acute lymphoblastic leukaemia

We have identified two novel ABL1 fusion genes in two patients with B-cell acute lymphoblastic leukaemia (ALL) associated with a t(3;9)(p12;q34) and a t(5;9)(q23;q34), respectively. Molecular analysis revealed a FOXP1-ABL1 fusion for the t(3;9) and a SNX2-ABL1 fusion for the t(5;9). The fusions were confirmed by specific amplification of the genomic breakpoints using reverse transcription polymerase chain reaction. The identification of ALL with rare ABL1 fusion partners is important because the leukaemia may respond to tyrosine kinase inhibitors in the same way as ALL patients with a classical BCR-ABL1 fusion gene.

CD44 isoform expression on colonic epithelium mediates lamina propria lymphocyte adhesion and is controlled by Th1 and Th2 cytokines

BACKGROUND AND AIMS

CD44v6 and CD44v3 are expressed on the surface of colonic epithelial cells in ulcerative colitis to a much greater extent than in Crohn's disease. We investigated mediators that induce CD44v6 and CD44v3 expression on colonic epithelium and the potential role of CD44 in mediating leucocyte-epithelial adhesion.

DESIGN AND METHODS

HT-29 cells were exposed to a range of T-helper 1 and T-helper 2 cytokines. Flow cytometry was used to determine their effect on CD44 isoform expression. The adhesion of peripheral blood and lamina propria lymphocytes to HT-29 monolayers was assessed and the effect of induction and blocking of CD44 isoforms was investigated.

RESULTS

Treatment of HT-29 cells with IL-4 and IL-13 resulted in a two- to three-fold increase in membrane expression of CD44v6 and CD44v3 isoforms. This was inhibited by T-helper 1 cytokines and hydrocortisone (P < 0.001). IL-4 increased lymphocyte adhesion to HT-29 monolayers approximately two-fold (P < 0.01). This increased adhesion of both lamina propria leucocytes and peripheral blood lymphocytes was abolished by anti-CD44v6 monoclonal antibodies (P < 0.01 and P < 0.05, respectively).

CONCLUSION

IL-4 and IL-13 are potent inducers of CD44v6 and CD44v3 expression on colon epithelial cells. The reciprocal effects of T-helper 2 and T-helper 1 cytokines on CD44 isoform expression may explain the observed differences between ulcerative colitis and colonic Crohn's disease. We have identified increased adhesion between lymphocytes and colon epithelial cells caused by IL-4-induced CD44v6 expression. This may contribute to epithelial targeting of inflammation in ulcerative colitis.

Immunolocalization of cathepsin D in pneumocytes of normal human lung and in pulmonary fibrosis

Cathepsin D expression has been assessed by immunohistochemistry and immunoelectron microscopy in fetal, normal adult and injured lungs of human beings. In addition to the well known positivity of alveolar macrophages and the bronchial epithelial cells, normal type I and to a lesser extent type II pneumocytes showed a granular, cytoplasmic staining pattern. Using immunogold labelling of lowicryl embedded human lung, cathepsin D was present in lysosomes of epithelial cells. Double immunofluorescence labelling employing type I and type II specific antibodies or lectins confirmed the epithelial staining for cathepsin D. At the terminal sac period during lung development cathepsin D appears in the alveolar epithelium. In fibrotic specimens, enhanced immunoreactivity was found in epithelial and non-epithelial cells. Proliferative epithelial formations were strongly stained with cathepsin D antibodies, whereas detached, desquamated epithelial cells were weakly positive or negative. We suggest that cathepsin D plays a role in the remodelling process during fibrogenesis.

A flow cytometric method for the detection of intracellular basic proteins in unseparated peripheral blood and bone marrow eosinophils

Eosinophils and their basic proteins play a major role in allergic disease and methods are required to monitor their expression in clinical situations. In this article we describe a flow cytometric method for the detection of intracellular eosinophil cationic protein (ECP) and eosinophil peroxidase (EPO) in unseparated clinical samples. After fixation with parabenzoquinone and permeabilization with n-octyl-beta-D-glucopyranoside, the detection of intracellularly stored proteins was achieved using of monoclonal antibodies against ECP (EG1, EG2) and EPO in combination with an FITC-labeled second step antibody. Confocal microscopy was used to demonstrate the intracellular origin of the fluorescent signal. Fixation with parabenzoquinone was superior to a previously described protocol using paraformaldehyde, since it reduces non-specific binding of FITC to the basic proteins in eosinophils. Fixation and permeabilization do not alter the light scatter characteristics of eosinophils in contrast to other leukocytes and thus permit gating on eosinophils without prior purification. Furthermore, the procedure does not alter the detection of cell surface antigens on eosinophils and simultaneous measurements of surface antigens and intracellular proteins is possible. We have used different clinical samples (peripheral blood, bone marrow cells) to demonstrate differences in the expression of ECP and EPO. We conclude that the detection of intracellular eosinophil proteins by flow cytometry is a rapid, easy and semiquantitative procedure which may be used to study their expression in diseases where eosinophils are involved.

T-cell cytokine profile evaluated at the single cell level in BAL and blood in allergic asthma

Atopic asthma is characterized by bronchial mucosal inflammation, involving eosinophils, mast cells, and lymphocytes. It has been suggested that the development and maintenance of this allergic inflammation is due to T-lymphocyte activation with predominant production of the cytokines interleukin 4 (IL-4) and IL-5. To address the ability of peripheral blood and bronchoalveolar lavage T-cells to generate IL-2, IL-4, or interferon gamma (IFN-gamma), we have employed a flow cytometric method which permits analysis of cytokine production at the single cell level within 5 h of obtaining cell samples. When stimulated with PMA and ionomycin, there was a greatly increased percentage of IFN-gamma-producing cells among bronchoalveolar lavage (BAL) T-cells from the subjects with asthma (median 74%), compared with atopic and nonatopic controls (35 and 43%, respectively; P>0.01). The proportion of BAL T-cells producing IL-4 was small (median 1.7%, range 0 to 7.8% in the asthmatic group). In all three groups, the proportion of BAL T-cells producing IL-2 or IFN-gamma was increased compared with T-cells from peripheral blood. There was no significant difference between the three groups in the percentage of BAL T-cells producing IL-2, or in the percentage of peripheral blood T-cells producing IFN-gamma, IL-2 or IL-4. These findings indicate that IL-4 production is confined to a relatively small proportion of airway and blood T-cells and that there is selective enhancement of IFN-gamma production by airway T-cells in asthma.

Morphometric analysis of chronic B-cell leukemias--an aid to the classification of lymphoid cell types

In order to evaluate the ultrastructural features which may be of relevance in distinguishing cells from the various chronic B-cell leukemias, a morphometric analysis was performed on a large number of cells from each disease group. The parameters selected were: cell size, nucleo: cytoplasmic ratio, chromatin condensation, size of the nucleolus and degree of irregularity of both the nucleus and the cytoplasmic outlines. The mean values obtained for each parameter for each disease group were compared statistically. In disorders in which the cells have villous cytoplasmic projections, the quantitative analysis of the cellular features was helpful to characterise the different types of B cells involved. Thus, cells from cases of splenic lymphoma were found to be different from those of hairy cell leukemia, and a variant form of HCL was also identified by its distinct ultrastructural features. Similarly cells from chronic lymphocytic, prolymphocytic leukemia and an intermediate group CLL/PL were identified by the size of the nucleolus and the degree of chromatin condensation. The morphometric findings provided an objective morphological basis for the differential diagnosis between these closely related B-cell leukemias which was further supported by differences in the cells immunophenotype.

Immunostaining of neuron-specific enolase is a valuable aid to the cytological diagnosis of neuroendocrine tumours of the lung

The neuroendocrine marker neuron-specific enolase (NSE) has been reported to be detectable by immunohistochemistry in paraffin sections of neuroendocrine neoplasms of the lung. There is no study of immunodetection of NSE in cytological smear preparations from these tumours. We have examined 10 cases of small cell carcinoma of the lung, using cells obtained from serous fluids or bronchial biopsies, and found all but one had NSE-like immunoreactivity. No such immunoreactivity was found in 26 serous fluids and 19 biopsies from non-small-cell carcinomas. It is suggested, therefore, that immunostaining for NSE is a valuable aid to the cytological diagnosis of small cell carcinoma of the lung.

Hyperplasia of antral G cells in uraemic patients

In this study we have performed a quantitative analysis of antral gastrin cells in 9 uraemic patients under dialytic treatment compared to a group of 10 chronic gastritis patients with a similar histological degree of gastritis. Immunocytochemistry was carried out on endoscopic biopsies of both groups. Using a computerised image analysing system we showed a significant increase of G-cell density (number of cells/mm2) in uraemic patients compared to non-uraemics (p less than 0.001). These findings provide a further morphological basis for the elevation of gastrin levels in chronic uraemic patients, suggesting the existence of a specific factor inducing G-cell proliferation in these patients.