Comparison of cell fixation methods of induced sputum specimens: an immunocytochemical analysis

The Combination of Paraformaldehyde and Glutaraldehyde Is a Potential Fixative for Mitochondria

Mitochondria are highly dynamic organelles, constantly undergoing shape changes, which are controlled by mitochondrial movement, fusion, and fission. Mitochondria play a pivotal role in various cellular processes under physiological and pathological conditions, including metabolism, superoxide generation, calcium homeostasis, and apoptosis. Abnormal mitochondrial morphology and mitochondrial protein expression are always closely related to the health status of cells. Analysis of mitochondrial morphology and mitochondrial protein expression in situ is widely used to reflect the abnormality of cell function in the chemical fixed sample. Paraformaldehyde (PFA), the most commonly used fixative in cellular immunostaining, still has disadvantages, including loss of antigenicity and disruption of morphology during fixation. We tested the effect of ethanol (ETHO), PFA, and glutaraldehyde (GA) fixation on cellular mitochondria. The results showed that 3% PFA and 1.5% GA (PFA-GA) combination reserved mitochondrial morphology better than them alone in situ in cells. Mitochondrial network and protein antigenicity were well maintained, indicated by preserved MitoTracker and mitochondrial immunostaining after PFA-GA fixation. Our results suggest that the PFA-GA combination is a valuable fixative for the study of mitochondria in situ.

Flow-cytometric quantification of microbial cells on sand from water biofilters

Rapid quantification of absolute microbial cell abundances is important for a comprehensive interpretation of microbiome surveys and crucial to support theoretical modelling and the design of engineered systems. In this paper, we propose a protocol specifically optimised for the quantification of microbial abundances in water biofilters using flow cytometry (FCM). We optimised cell detachment from sand biofilter particles for FCM quantification through the evaluation of five chemical dispersants (NaCl, Triton-X100, CaCl₂, sodium pyrophosphate (PP), Tween 80 combined with PP), different mechanical pre-treatments (low and high energy sonication and shaking) and two fixation methods (glutaraldehyde and ethanol). The developed protocol was cross-compared using other established and commonly employed methods for biomass quantification in water filter samples (adenosine triphosphate (ATP) quantification, real-time quantitative PCR (qPCR) and volatile solids (VS)). The highest microbial count was obtained by detaching the biofilm from biofilter grains and dispersing clusters into singles cells using Tween 80 and sodium pyrophosphate combined with four steps of high energy sonication (27W, for 80 s each step); glutaraldehyde was shown to be the best fixative solution. The developed protocol was reliable and highly reproducible and produced results that are comparable to data from alternative quantification methods. Indeed, high correlations were found with trends obtained through ATP and qPCR (ρ = 0.98 and ρ = 0.91) measurements. The VS content was confirmed as an inaccurate method to express biomass in sand samples since it correlated poorly with all the other three methods (ρ = 0.005 with FCM, 0.002 with ATP and 0.177 with qPCR). FCM and ATP showed the strongest agreement between absolute counts with a slope of the correlation equal to 0.7, while qPCR seemed to overestimate cell counts by a factor of ten. The rapidity and reproducibility of the method developed make its application ideal for routine quantification of microbial cell abundances on sand from water biofilters and thus useful in revealing the ecological patterns and quantifying the metabolic kinetics involved in such systems.

Biomechanical investigation of a minimally invasive posterior spine stabilization system in comparison to the Universal Spinal System (USS)

Background

Although minimally invasive posterior spine implant systems have been introduced, clinical studies reported on reduced quality of spinal column realignment due to correction loss. The aim of this study was to compare biomechanically two minimally invasive spine stabilization systems versus the Universal Spine Stabilization system (USS).

Methods

Three groups with 5 specimens each and 2 foam bars per specimen were instrumented with USS (Group 1) or a minimally invasive posterior spine stabilization system with either polyaxial (Group 2) or monoaxial (Group 3) screws.

Mechanical testing was performed under quasi-static ramp loading in axial compression and torsion, followed by destructive cyclic loading run under axial compression at constant amplitude and then with progressively increasing amplitude until construct failure.

Bending construct stiffness, torsional stiffness and cycles to failure were investigated.

Results

Initial bending stiffness was highest in Group 3, followed by Group 2 and Group 1, without any significant differences between the groups.

A significant increase in bending stiffness after 20’000 cycles was observed in Group 1 (p = 0.002) and Group 2 (p = 0.001), but not in Group 3, though the secondary bending stiffness showed no significant differences between the groups.

Initial and secondary torsional stiffness was highest in Group 1, followed by Group 3 and Group 2, with significant differences between all groups (p ≤ 0.047). A significant increase in initial torsional stiffness after 20’000 cycles was observed in Group 2 (p = 0.017) and 3 (p = 0.013), but not in Group 1.

The highest number of cycles to failure was detected in Group 1, followed by Group 3 and Group 2. This parameter was significantly different between Group 1 and Group 2 (p = 0.001), between Group 2 and Group 3 (p = 0.002), but not between Group 1 and Group 3.

Conclusions

These findings quantify the correction loss for minimally invasive spine implant systems and imply that unstable spine fractures might benefit from stabilization with conventional implants like the USS.

Chemical fixation methods for Raman spectroscopy-based analysis of bacteria

Preservation of biological samples for downstream analysis is important for analytical methods that measure the biochemical composition of a sample. One such method, Raman microspectroscopy, is commonly used as a rapid phenotypic technique to measure biomolecular composition for the purposes of identification and discrimination of species and strains of bacteria, as well as investigating physiological responses to external stressors and the uptake of stable isotope-labelled substrates in single cells. This study examines the influence of a number of common chemical fixation and inactivation methods on the Raman spectrum of six species of bacteria. Modifications to the Raman-phenotype caused by fixation were compared to unfixed control samples using difference spectra and Principal Components Analysis (PCA). Additionally, the effect of fixation on the ability to accurately classify bacterial species using their Raman phenotype was determined. The results showed that common fixatives such as glutaraldehyde and ethanol cause significant changes to the Raman spectra of bacteria, whereas formaldehyde and sodium azide were better at preserving spectral features.

HOPE-preservation of paraffin-embedded sputum samples--a new way of bioprofiling in COPD

Induced sputum is a non-invasive sampling technique for the analysis of airway inflammation in various lung diseases and comprises valuable potential for the identification of biomarkers and therapeutic targets by molecular methods. In the context of biobanking with preservation of induced sputum samples for subsequent analyses we applied the HEPES-glutamic acid buffer-mediated organic solvent protection effect (HOPE)-technique for preparation of induced sputum samples. Induced sputum samples of 20 patients with moderate to severe chronic obstructive pulmonary disease (COPD) and 12 healthy controls were collected. Cell pellets of induced sputum samples were preserved with HOPE and subsequently embedded in paraffin. Immunostaining of paraffin-block sections for interleukin-8, interleukin-17, myeloperoxidase, matrixmetalloproteinase-9, CD68, and CD8 revealed distinct signals without antigen retrieval. Moreover, RNA was extracted and successfully used for transcription microarray analysis. Sputum samples preserved by the HOPE-technique display a tool to address scientific approaches in pulmonary research, which can enable the identification of new biomarkers and therapeutic targets in respiratory diseases.

The dynamic changes of circulating OCN+ cells versus insulinlike growth factor-I during primary healing of orthognathic surgeries

OBJECTIVE

The objective of this study was to determine the dynamic changes of circulating osteocalcin(+) (OCN(+)) cells and insulinlike growth factor-I (IGF-I) in peripheral blood during early primary repair of jaw bones in patients with orthognathic surgery.

STUDY DESIGN

The expression of bone-related genes was detected by RT-PCR in circulating OCN(+) cells. The numbers of OCN(+) cells and serum level of IGF-I were determined by flow cytometry, immunocytochemical staining, and ELISA.

RESULTS

OCN(+) cells significantly increased in peripheral blood, and reached the peak at 1 to 2 weeks after surgery (P < .05). IGF-I in patients significantly decreased 1 week after surgery (P < .05), and then returned gradually to the normal level. There was no significant correlation between the number of circulating OCN(+) cells and the level of IGF-I (P > .05).

CONCLUSIONS

These findings suggested that circulating OCN(+) cells, at least in part, could be mobilized in response to bone injury, and contribute to bone repair in patients with orthognathic surgery.

Optimization of fixation methods for observation of bacterial cell morphology and surface ultrastructures by atomic force microscopy

Fixation ability of five common fixation solutions, including 2.5% glutaraldehyde, 10% formalin, 4% paraformaldehyde, methanol/acetone (1:1), and ethanol/acetic acid (3:1) were evaluated by using atomic force microscopy in the present study. Three model bacteria, i.e., Escherichia coli, Pseudomonas putida, and Bacillus subtilis were applied to observe the above fixation methods for the morphology preservation of bacterial cells and surface ultrastructures. All the fixation methods could effectively preserve cell morphology. However, for preserving bacterial surface ultrastructures, the methods applying aldehyde fixations performed much better than those using alcohols, since the alcohols could detach the surface filaments (i.e., flagella and pili) significantly. Based on the quantitative and qualitative assessments, the 2.5% glutaraldehyde was proposed as a promising fixation solution both for observing morphology of both bacterial cell and surface ultrastructures, while the methonal/acetone mixture was the worst fixation solution which may obtain unreliable results.

Characterization of pentraxin 3 in the horse and its expression in airways

The long pentraxin 3 (PTX3) plays an important role in host defence and its over-expression may contribute to airway injury. The aim of the present study was therefore to characterize in more detail PTX3 and its expression in the horses’ airway. Six healthy horses and six horses affected by recurrent airway obstruction (R.A.O.) were submitted to a dusty environment challenge. PTX3 DNA and cDNA were cloned and sequenced. PTX3 expression was evaluated by RT-qPCR, Western blotting and immuno-histochemistry in bronchoalveolar lavage fluid (BALF) cells, BALF supernatant and bronchial epithelial cells. An alternative splicing of the second exon of PTX3 occurred, resulting in two forms of the protein: “spliced” (32 kDa) and “full length” (42 kDa). PTX3 was detected in BALF macrophages, neutrophils and bronchial epithelial cells. It was over-expressed in the BALF supernatant from R.A.O.-affected horses in crisis. However, dust was unable to induce PTX3 in BALF cells ex vivo, indicating that dust is an indirect inducer of PTX3. Dust exposure in-vivo induced PTX3 in BALF macrophages but there was no significant difference between healthy and R.A.O.-affected horses. Conversely, PTX3 was over-expressed in the bronchial epithelial cells from R.A.O.-affected horses in crisis. These data indicate a differential regulatory mechanism in inflammatory and bronchial epithelial cells and offer therapeutically interesting perspectives.

Alveolar macrophage subpopulations in bronchoalveolar lavage and induced sputum of asthmatic and control subjects

BACKGROUND

Alveolar macrophages (AM) are the most numerous immune cells in the airways and are involved in the immunological homeostasis of the lung. Intriguingly, their role in asthma remains unclear probably, in part, because of their heterogeneity.

OBJECTIVE

To characterize AM population from bronchoalveolar lavage (BAL) and induced sputum (IS) of asthmatic and normal subjects using specific biomarkers.

METHODS

Non-asthmatic non-allergic and allergic mild asthmatic subjects were recruited for this study. AM were obtained from BAL and IS and cytospins were prepared. Immunocytochemistry was performed for nine cellular markers (CD68, RFD7, CD14, CD11b, CD83, CD64, CD80, CD86, and FIZZ1).

RESULTS

Asthmatic subjects had more AM RFD7(+) in BAL compared with IS, whereas control subjects had more AM RFD7(+) in IS than in BAL. Consequently, there was an increased number of AM RFD7(+) in BAL of asthmatic subjects compared with BAL of control subjects. AM CD11b(+) was higher in BAL than in IS in both groups. The expression of FIZZ1, marker of macrophage alternative activation, was similar in asthmatic and normal subjects.

CONCLUSION

The expression of cellular markers on AM differs according to their localization in the lung. Subpopulations of AM may contribute to the inflammatory profile observed in asthmatic subjects.