Short-term chilled storage of zebrafish (Danio rerio) embryos in cryoprotectant as an alternative to cryopreservation.

As zebrafish embryos have never been cryopreserved, we developed a protocol to store zebrafish embryos (50% epiboly-5.3 hour post fertilization) for up to 18 h at 0°C. Initial experiments to optimize the cryoprotectant (CPA) solution demonstrated improved embryo hatching rate following chilling at 0°C for 18 h with 1 M MeOH+0.1 M sucrose (56 ± 5%) compared with other combinations of methanol (0.2-0.5 M) and sucrose (0.05-0.1 M). This combination of CPAs that protects against chilling injury was further tested to assess its impact on sox gene and protein expression. Significant decreases in sox3 gene expression were observed in hatched embryos that had been chilled for 18 h in 1 M MeOH+0.1 sucrose compared with non-chilled controls, however the expression of both sox2 and sox3 proteins was unaffected. Significant decreases in sox2 protein expression were, however, observed in embryos that had been chilled without CPAs and these embryos also had lower hatching rates than those chilled with the optimal CPA solution. We, therefore, conclude that the CPA combination of 1 M MeOH+0.1 M sucrose facilitates chilled storage of early stage (50% epiboly) zebrafish embryos for up to 18 h without compromising transcriptional response

Use of methanol as cryoprotectant and its effect on sox genes and proteins in chilled zebrafish embryos

Methanol is a widely used cryoprotectant (CPA) in cryopreservation of fish embryos, however little is known about its effect at the molecular level. This study investigated the effect of methanol on sox gene and protein expression in zebrafish embryos (50% epiboly) when they were chilled for 3. h and subsequently warmed and cultured to the hatching stages. Initial experiments were carried out to evaluate the chilling tolerance of 50% epiboly embryos which showed no significant differences in hatching rates for up to 6. h chilling in methanol (0.2-, 0.5- and 1. M). Subsequent experiments in embryos that had been chilled for 3. h in 1. M methanol and warmed and cultured up to the hatching stages found that sox2 and sox3 gene expression were increased significantly in hatched embryos that had been chilled compared to non-chilled controls. Sox19a gene expression also remained above control levels in the chilled embryos at all developmental stages tested. Whilst stable sox2 protein expression was observed between non-chilled controls and embryos chilled for 3. h with or without MeOH, a surge in sox19a protein expression was observed in embryos chilled for 3. h in the presence of 1. M MeOH compared to non-chilled controls and then returned to control levels by the hatching stage. The protective effect of MeOH was increased with increasing concentrations. Effect of methanol at molecular level during chilling was reported here first time which could add new parameter in selection of cryoprotectant while designing cryopreservation protocol

Studies on the effect of chilling on sox genes and protein expression in zebrafish (Danio rerio) embryos

A thesis is submitted to the University of Bedfordshire in partial fulfilment of the requirements for the degree of Doctor of PhilosophyIn aquaculture, short term chilled storage has been used to transport brood stock fish embryos for genetic improvement programmes. It is therefore important to understand the effect of chilling on embryos at both developmental and molecular levels. In the present study, gene expression patterns in zebrafish embryos were studied before investigations were carried out on the effect of chilling on gene and protein expression in these embryos. The gene expression results obtained in different developmental stages using conventional PCR showed that, only sox genes were expressed throughout the tested developmental stages from 30% epiboly to 6 somites. Quantitative RT-PCR was then used to investigate sox gene expression patterns during chilling of 50% epiboly stage embryos at 0°C for up to 180 min and also after warming. Significant decreases in sox2 and sox3 expressions were observed when compared to those of controls following chilling whilst significant increases of expressions of the two genes were observed after warming in the embryos chilled for 30 and 60 min. Studies on the impact of cryoprotectant MeOH on sox genes and protein expression showed that 50% epiboly stage zebrafish embryos could tolerate chilling for up to 6 h with or without MeOH. It was observed that expression of all three sox genes were significantly decreased following chilling for 3 h at 0°C. However the degree of decrease was less pronounced in embryos chilled with different concentrations of MeOH. Significant increases in sox genes were observed in hatching stage embryos chilled with 1 M MeOH for 3h but subsequent sox2 and sox19a protein expression was not affected. The effect of long term chilling (18h) on sox gene and protein expression in 50% epiboly stage embryos was also investigated. Improved hatching rates (56% ± 5) were achieved when embryos were chilled with 1 M MeOH + 0.1 M sucrose. Results from gene expression studies showed a stable sox2 gene expression in 18 h chilled embryos in cryoprotectant mixture when compared to that of embryos chilled without cryoprotectant mixture. Similar patterns were observed when the expression of sox2 and sox3 protein was investigated. This is the first study carried out on the effect of chilling in early stage zebrafish embryos at the molecular level. The results obtained from the present study provided useful information on the molecular mechanisms of the effect of chilling on zebrafish embryos and will have important implications in designing chilled storage protocols for fish embryos

Effect of chilling on sox2, sox3 and sox19a gene expression in zebrafish (Danio rerio) embryos

Zebrafish embryos have not been cryopreserved due to their structural limitations. Although embryo survival rates have been used as the measured outcome for most of the cryopreservation protocols studied, there are very limited data available at the molecular level. This study focused on the effect of chilling and subsequent warming on gene expression of sox2, sox3 and sox19a which play vital roles in the development of zebrafish embryos. A quantitative RT-PCR approach was used to investigate gene expression following chilling at 0°C for up to 180 min. The effect on gene expression was also studied during a 180 min warming period after chilling for 30 or 60 min. There were significant decreases in sox2 (up to 4-fold) and sox3 (up to 3-fold) expressions following chilling. Significant increases in gene expressions of sox2 (up to 2-fold), sox3 (up to 33-fold) and sox19a (up to 25-fold) were observed during warming in the embryos that had been chilled for 30 min. Similarly, significant increases were observed in sox2 (up to 3-fold) and sox3 (up to 2-fold) during warming in embryos that had been chilled for 60 min. These increases may be explained by compensation for the suppression observed during chilling and/or to activate repair mechanisms or maintain homeostasis

Haemodynamic-guided management of heart failure (GUIDE-HF): A randomised controlled trial

BACKGROUND: Previous studies have suggested that haemodynamic-guided management using an implantable pulmonary artery pressure monitor reduces heart failure hospitalisations in patients with moderately symptomatic (New York Heart Association [NYHA] functional class III) chronic heart failure and a hospitalisation in the past year, irrespective of ejection fraction. It is unclear if these benefits extend to patients with mild (NYHA functional class II) or severe (NYHA functional class IV) symptoms of heart failure or to patients with elevated natriuretic peptides without a recent heart failure hospitalisation. This trial was designed to evaluate whether haemodynamic-guided management using remote pulmonary artery pressure monitoring could reduce heart failure events and mortality in patients with heart failure across the spectrum of symptom severity (NYHA funational class II-IV), including those with elevated natriuretic peptides but without a recent heart failure hospitalisation. METHODS: The randomised arm of the haemodynamic-GUIDEed management of Heart Failure (GUIDE-HF) trial was a multicentre, single-blind study at 118 centres in the USA and Canada. Following successful implantation of a pulmonary artery pressure monitor, patients with all ejection fractions, NYHA functional class II-IV chronic heart failure, and either a recent heart failure hospitalisation or elevated natriuretic peptides (based on a-priori thresholds) were randomly assigned (1:1) to either haemodynamic-guided heart failure management based on pulmonary artery pressure or a usual care control group. Patients were masked to their study group assignment. Investigators were aware of treatment assignment but did not have access to pulmonary artery pressure data for control patients. The primary endpoint was a composite of all-cause mortality and total heart failure events (heart failure hospitalisations and urgent heart failure hospital visits) at 12 months assessed in all randomly assigned patients. Safety was assessed in all patients. A pre-COVID-19 impact analysis for the primary and secondary outcomes was prespecified. This study is registered with ClinicalTrials.gov, NCT03387813. FINDINGS: Between March 15, 2018, and Dec 20, 2019, 1022 patients were enrolled, with 1000 patients implanted successfully, and follow-up was completed on Jan 8, 2021. There were 253 primary endpoint events (0·563 per patient-year) among 497 patients in the haemodynamic-guided management group (treatment group) and 289 (0·640 per patient-year) in 503 patients in the control group (hazard ratio [HR] 0·88, 95% CI 0·74-1·05; p=0·16). A prespecified COVID-19 sensitivity analysis using a time-dependent variable to compare events before COVID-19 and during the pandemic suggested a treatment interaction (pinteraction=0·11) due to a change in the primary endpoint event rate during the pandemic phase of the trial, warranting a pre-COVID-19 impact analysis. In the pre-COVID-19 impact analysis, there were 177 primary events (0·553 per patient-year) in the intervention group and 224 events (0·682 per patient-year) in the control group (HR 0·81, 95% CI 0·66-1·00; p=0·049). This difference in primary events almost disappeared during COVID-19, with a 21% decrease in the control group (0·536 per patient-year) relative to pre-COVID-19, virtually no change in the treatment group (0·597 per patient-year), and no difference between groups (HR 1·11, 95% CI 0·80-1·55; p=0·53). The cumulative incidence of heart failure events was not reduced by haemodynamic-guided management (0·85, 0·70-1·03; p=0·096) in the overall study analysis but was significantly decreased in the pre-COVID-19 impact analysis (0·76, 0·61-0·95; p=0·014). 1014 (99%) of 1022 patients had freedom from device or system-related complications. INTERPRETATION: Haemodynamic-guided management of heart failure did not result in a lower composite endpoint rate of mortality and total heart failure events compared with the control group in the overall study analysis. However, a pre-COVID-19 impact analysis indicated a possible benefit of haemodynamic-guided management on the primary outcome in the pre-COVID-19 period, primarily driven by a lower heart failure hospitalisation rate compared with the control group. FUNDING: Abbott