Soluble mediators in packed red blood cells augment lipopolysaccharide-induced monocyte interleukin-1β production

BACKGROUND AND OBJECTIVES

Soluble mediators in packed red-blood-cell (PRBC) units have been hypothesized as a mechanism associated with transfusion-related immune modulation. Soluble mediators including damage-associated molecular patterns (DAMPs) are known to activate inflammasomes. Inflammasome complexes maturate caspase-1 and interleukin (IL)-1β. We assessed whether PRBC supernatants (SN) modulated IL-1β driven inflammation and whether macrophage migration inhibitory factor (MIF) was a contributing factor.

MATERIALS AND METHODS

Isolated monocytes were incubated with PRBC-SN in an in vitro transfusion model. Lipopolysaccharide (LPS) was added in parallel to model a bacterial infection. Separately, recombinant MIF was used in the model to assess its role in IL-1β driven inflammation. IL-1β and caspase-1 were quantified in the PRBC-SN and culture SN from the in vitro model.

RESULTS

PRBC-SN alone did not induce IL-1β production from monocytes. However, PRBC-SN alone increased caspase-1 production. LPS alone induced both IL-1β and caspase-1 production. PRBC-SN augmented LPS-driven IL-1β and caspase-1 production. Recombinant MIF did not modulate IL-1β production in our model.

CONCLUSIONS

Soluble mediators in PRBC modulate monocyte IL-1β inflammation, which may be a contributing factor to adverse effects of transfusion associated with poor patient outcomes. While MIF was present in PRBC-SN, we found no evidence that MIF was responsible for IL-1β associated immune modulation.

Coronary artery bypass grafting surgery differentially modulates the leucocyte gene expression profile

Coronary artery bypass grafting (CABG) surgery triggers a systemic inflammatory response activating leucocyte subsets and cytokine secretion. Changes to the patient immune profile post-surgery may contribute to adverse outcomes such as infection. Investigating patient immune modulation at the molecular level may improve our understanding of the underlying mechanisms associated with adverse outcomes post-surgery. This study assessed changes to the leucocyte gene expression profile of CABG patients (n=50) at 5 time-points (admission, intra-operative, ICU, day 3, day 5). RNA was isolated from freshly collected whole blood for cDNA synthesis, pre-amplification and RT-PCR of 48 genes using the TaqMan Gene Expression Array Cards (Applied Biosystems). Gene expression at each time-point was compared to admission (repeated-measures one-way ANOVA with Dunnett’s post-test; P<0.05). Antigen presentation capacity was decreased throughout the post-operative period, evidenced by reduced expression of key regulator genes TAP1, TAP2, HLA-DRA and CD40. CABG surgery increased gene expression of cytokines and chemokines including IL-12A, IL-6 and TNF before decreasing throughout the post-operative period. CABG also modulated the expression of signalling molecules including JAK1, RELA and STAT3, however expression returned towards baseline levels post-surgery. This study demonstrated CABG significantly impaired the patient immune response and key immune pathways at the molecular level. Understanding how CABG alters the patient immune profile assists in elucidating underlying mechanisms of adverse outcomes.

Coronary artery bypass grafting is associated with immunoparalysis of monocytes and dendritic cells

Coronary artery bypass grafting (CABG) triggers a systemic inflammatory response that may contribute to adverse outcomes. Dendritic cells (DC) and monocytes are immunoregulatory cells potentially affected by CABG, contributing to an altered immune state. This study investigated changes in DC and monocyte responses in CABG patients at 5 time-points: admission, peri-operative, ICU, day 3 and day 5. Whole blood from 49 CABG patients was used in an ex vivo whole blood culture model to prospectively assess DC and monocyte responses. Lipopolysaccharide (LPS) was added in parallel to model responses to an infectious complication. Co-stimulatory and adhesion molecule expression and intracellular mediator production was measured by flow cytometry. CABG modulated monocyte and DC responses. In addition, DC and monocytes were immunoparalysed, evidenced by failure of co-stimulatory and adhesion molecules (eg HLA-DR), and intracellular mediators (eg IL-6) to respond to LPS stimulation. DC and monocyte modulation was associated with prolonged ICU length of stay and post-operative atrial fibrillation. DC and monocyte cytokine production did not recover by day 5 post-surgery. This study provides evidence that CABG modulates DC and monocyte responses. Using an ex vivo model to assess immune competency of CABG patients may help identify biomarkers to predict adverse outcomes.

Analysis of mitochondrial function and localisation during human embryonic stem cell differentiation in vitro

Human embryonic stem cell (hESC) derivatives show promise as viable cell therapy options for multiple disorders in different tissues. Recent advances in stem cell biology have lead to the reliable production and detailed molecular characterisation of a range of cell-types. However, the role of mitochondria during differentiation has yet to be fully elucidated. Mitochondria mediate a cells response to altered energy requirements (e.g. cardiomyocyte contraction) and, as such, the mitochondrial phenotype is likely to change during the dynamic process of hESC differentiation. We demonstrate that manipulating mitochondrial biogenesis alters mesendoderm commitment. To investigate mitochondrial localisation during early lineage specification of hESCs we developed a mitochondrial reporter line, KMEL2, in which sequences encoding the green fluorescent protein (GFP) are targeted to the mitochondria. Differentiation of KMEL2 lines into the three germ layers showed that the mitochondria in these differentiated progeny are GFP positive. Therefore, KMEL2 hESCs facilitate the study of mitochondria in a range of cell types and, importantly, permit real-time analysis of mitochondria via the GFP tag.

Long term culture of human embryonic stem cells on recombinant vitronectin in ascorbate free media

Human embryonic stem cells (hESC) are expected to provide revolutionary therapeutic applications and drug discovery technologies. In order for this to be achieved a reproducible, defined animal component free culture system is required for the scale-up production of undifferentiated hESC. In this work we have investigated the applicability of a recombinantly produced domain of human vitronectin as an extracellular matrix alternative to the common standards Geltrex or Matrigel. In addition we have validated an ascorbate free media capable of supporting CD30(low) populations of hESC through a multi-factorial analysis of bFGF and Activin A. The recombinant vitronectin domain combined with the ascorbate free media were capable of supporting 3 cell lines, MEL1, MEL2 and hES3 for 10 or more passages while maintaining hESC pluripotency markers and differentiation capacity. The culture method outlined here provides a platform for future investigation into growth factor and extracellular matrix effects on hESC maintenance prior to bioreactor scale-up.

Radiofrequency ablation for treatment of primary atrial tachycardias

OBJECTIVES

The purpose of this study was to determine the safety and efficacy of radiofrequency ablation as definitive therapy for primary atrial tachycardias.

BACKGROUND

Primary atrial tachycardias are often difficult to control with antiarrhythmic medications and frequently require nonpharmacologic interventions for definitive therapy. Despite isolated reports of successful treatment of primary atrial tachycardias with radiofrequency ablation, the safety and efficacy of this technique have not been established in a larger series with long-term follow-up.

METHODS

The immediate procedural success rate, associated complications and follow-up data of radiofrequency ablation were evaluated in 15 consecutive patients (11 adults and 4 children) with primary atrial arrhythmias that were refractory to medical management.

RESULTS

The clinical arrhythmia was ectopic atrial tachycardia in 11 patients and sinus node reentry in 4. The site of origin of the tachycardia was in the right atrium in 14 patients and in the left atrium in 1 patient (with two distinct foci) where the local atrial electrogram preceded the onset of the P wave by 10 to 30 ms. Radiofrequency energy successfully terminated the primary atrial tachycardia in each of the patients, and all were discharged from the electrophysiology laboratory in sinus rhythm without inducible atrial tachycardia. A mean of 10.8 +/- 9.9 radiofrequency applications were delivered using 30 W of power for 30 s. The local intracardiac activation time (relative to the P wave in the surface electrocardiogram) was a mean of -21 +/- 5 ms at the successful ablation site and -15 +/- 6 ms at unsuccessful sites (p < 0.001). No complications were observed, although one patient with incessant ectopic atrial tachycardia had sinus pauses after ablation. During a mean follow-up period of 277 +/- 133 days, the clinical arrhythmia recurred in three patients (20%, 95% confidence intervals 3% to 37%) including two patients with ectopic atrial tachycardia and one patient with sinus node reentry. One of these patients was successfully treated in a second ablation session.

CONCLUSIONS

Thus, radiofrequency catheter ablation appears to be a safe and effective technique for the treatment of primary atrial arrhythmias that are refractory to antiarrhythmic medications.

The role of closed pleural needle biopsy in the diagnosis of malignant mesothelioma of the pleura

Malignant mesothelioma of the pleura is a disease that requires a biopsy procedure for a definitive diagnosis. In the past, closed pleural needle biopsy (CPNB) has given poor yields due to the small amount of tissue obtained, and the patient has subsequently been subjected to a diagnostic thoracotomy. In recent years, the availability of more accurate histopathologic tests have enabled the pathologist to make a diagnosis more easily on samples obtained at CPNB. In this retrospective study of 20 consecutive cases of malignant mesothelioma of the pleura diagnosed between 1980 and 1990, we found that a blind CPNB was diagnostic in five of seven procedures and CT-guided CPNB was diagnostic in five of six procedures. An open pleural biopsy (OPB) was diagnostic in ten of ten procedures performed. There were no complications associated with any of the CPNB procedures. We conclude that CPNB is a safe and effective manner of diagnosing malignant mesothelioma of the pleura, and should be attempted prior to OPB.