Cell cycle specific, differentially tagged ribosomal proteins to measure phase specific transcriptomes from asynchronously cycling cells

Asynchronously cycling cells pose a challenge to the accurate characterization of phase-specific gene expression. Current strategies, including RNAseq, survey the steady state gene expression across the cell cycle and are inherently limited by their inability to resolve dynamic gene regulatory networks. Single cell RNAseq (scRNAseq) can identify different cell cycle transcriptomes if enough cycling cells are present, however some cells are not amenable to scRNAseq. Therefore, we merged two powerful strategies, the CDT1 and GMNN degrons used in Fluorescent Ubiquitination-based Cell Cycle Indicator (FUCCI) cell cycle sensors and the ribosomal protein epitope tagging used in RiboTrap/Tag technologies to isolate cell cycle phase-specific mRNA for sequencing. The resulting cell cycle dependent, tagged ribosomal proteins (ccTaggedRP) were differentially expressed during the cell cycle, had similar subcellular locations as endogenous ribosomal proteins, incorporated into ribosomes and polysomes, and facilitated the recovery of cell cycle phase-specific RNA for sequencing. ccTaggedRP has broad applications to investigate phase-specific gene expression in complex cell populations.

Therapy-Related Clonal Hematopoiesis: A New Link Between Cancer and Cardiovascular Disease

Clonal hematopoiesis is a precancerous state that is recognized as a new causal risk factor for cardiovascular disease. Therapy-related clonal hematopoiesis is a condition that is often found in cancer survivors. These clonal expansions are caused by mutations in DNA damage-response pathway genes that allow hematopoietic stem cells to undergo positive selection in response to the genotoxic stress. These mutant cells increasingly give rise to progeny leukocytes that display enhanced proinflammatory properties. Recent experimental studies suggest that therapy-related clonal hematopoiesis may contribute to the medium- to long-term risk of genotoxic therapies on the cardiovascular system.

Routine Use of Contrast on Admission Transthoracic Echocardiography for Heart Failure Reduces the Rate of Repeat Echocardiography during Index Admission

BACKGROUND

The authors retrospectively evaluated the impact of ultrasound enhancing agent (UEA) use in the first transthoracic echocardiographic (TTE) examination, regardless of baseline image quality, on the number of repeat TTEs and length of stay (LOS) during a heart failure (HF) admission.

METHODS

There were 9,115 HF admissions associated with admission TTE examinations over a 4-year period (5,337 men; mean age, 67.6 ± 15.0 years). Patients were grouped into those who received UEAs (contrast group) in the first TTE study and those who did not (noncontrast group). Repeat TTE examinations were classified as justified if performed for concrete clinical indications during hospitalization.

RESULTS

In the 9,115 admissions for HF (5,600 in the contrast group, 3,515 in the noncontrast group), 927 patients underwent repeat TTE studies (505 in the contrast group, 422 in the noncontrast group), which were considered justified in 823 patients. Of the 104 patients who underwent unjustified repeat TTE studies, 80 (76.7%) belonged to the noncontrast group and 24 to the contrast group. Also, UEA use increased from 50.4% in 2014 to 74.3%, and the rate of unjustified repeat studies decreased from 1.3% to 0.9%. The rates of unjustified repeat TTE imaging were 2.3% and 0.4% (in the noncontrast and contrast groups, respectively), and patients in the contrast group were less likely to undergo unjustified repeat examinations (odds ratio, 0.18; 95% CI, 0.12-0.29; P < .0001). The mean LOS was significantly lower in the contrast group (9.5 ± 10.5 vs 11.1 ± 13.7 days). The use of UEA in the first TTE study was also associated with reduced LOS (linear regression, β₁ = -0.47, P = .036), with 20% lower odds for odds of prolonged (>6 days) LOS.

CONCLUSIONS

The routine use of UEA in the first TTE examination for HF irrespective of image quality is associated with reduced unjustified repeat TTE testing and may reduce LOS during an index HF admission.

Mitochondrial pyruvate carriers are required for myocardial stress adaptation

In addition to fatty acids, glucose and lactate are important myocardial substrates under physiologic and stress conditions. They are metabolized to pyruvate, which enters mitochondria via the mitochondrial pyruvate carrier (MPC) for citric acid cycle metabolism. In the present study, we show that MPC-mediated mitochondrial pyruvate utilization is essential for the partitioning of glucose-derived cytosolic metabolic intermediates, which modulate myocardial stress adaptation. Mice with cardiomyocyte-restricted deletion of subunit 1 of MPC (cMPC1^-/-) developed age-dependent pathologic cardiac hypertrophy, transitioning to a dilated cardiomyopathy and premature death. Hypertrophied hearts accumulated lactate, pyruvate and glycogen, and displayed increased protein O-linked N-acetylglucosamine, which was prevented by increasing availability of non-glucose substrates in vivo by a ketogenic diet (KD) or a high-fat diet, which reversed the structural, metabolic and functional remodelling of non-stressed cMPC1^-/- hearts. Although concurrent short-term KDs did not rescue cMPC1^-/- hearts from rapid decompensation and early mortality after pressure overload, 3 weeks of a KD before transverse aortic constriction was sufficient to rescue this phenotype. Together, our results highlight the centrality of pyruvate metabolism to myocardial metabolism and function.

Lack of chondrogenic expression in mouse limb bud micromass cultures exposed to exogenous beta galactosidase or N-acetyl-beta-glucosaminidase

The effect of two exoglycosidases, beta-galactosidase and N-acetyl-beta-glucosaminidase (GlcNAc-ase) on chondrogenic expression of stage 19 mouse limb bud micromass cultures was investigated. Chondrogenic expression was monitored by Alcian blue staining and immunofluorescent localization of cartilage-specific proteoglycan and type II collagen. Chondrogenesis was inhibited by exposure to 0.1 U/ml beta-galactosidase or 0.025 U/ml GlcNAc-ase for 24 h or longer in culture. The effect of both enzymes was concentration and time dependent. Exoglycosidic hydrolysis of galactose or N-acetylglucosamine was substantiated by treatment with HRP-conjugated peanut agglutinin and succinylated wheat germ agglutinin, respectively. Cells treated with beta-galactosidase appeared to be flattened with a stellate morphology, whereas GlcNAc-ase-treated cells were bipolar forming ridge-like mounds that had a directional orientation. The antichondrogenic effect was not alleviated when the cells were induced to assume a spherical shape upon treatment with cytochalasin D. DNA measurements indicated that the lack of chondrogenic expression was not related to cell attachment or cell proliferation. These data support the hypothesis that the expression of specific terminal sugars on cell surface glycoconjugates of limb bud cells represents an important component of the chondrogenic process.

Effects of centrifugation, glycerol level, cooling to 5°C, freezing rate and thawing rate on the post-thaw motility of equine sperm

Five experiments evaluated the effects of processing, freezing and thawing techniques on post-thaw motility of equine sperm. Post-thaw motility was similar for sperm frozen using two cooling rates. Inclusion of 4% glycerol extender was superior to 2 or 6%. Thawing in 75 degrees C water for 7 sec was superior to thawing in 37 degrees C water for 30 sec. The best procedure for concentrating sperm, based on sperm motility, was diluting semen to 50 x 10(6) sperm/ml with a citrate-based centrifugation medium at 20 degrees C and centrifuging at 400 x g for 15 min. There was no difference in sperm motility between semen cooled slowly in extender with or without glycerol to 5 degrees C prior to freezing to -120 degrees C and semen cooled continuously from 20 degrees C to -120 degrees C. From these experiments, a new procedure for processing, freezing and thawing semen evolved. The new procedure involved dilution of semen to 50 x 10(6) sperm/ml in centrifugation medium and centrifugation at 400 x g for 15 min, resuspension of sperm in lactose-EDTA-egg yolk extender containing 4% glycerol, packaging in 0.5-ml polyvinyl chloride straws, freezing at 10 degrees C/min from 20 degrees C to -15 degrees C and 25 degrees C/min from -15 degrees C to -120 degrees C, storage at -196 degrees C, and thawing at 75 degrees C for 7 sec. Post-thaw motility of sperm averaged 34% for the new method as compared to 22% for the old method (P<0.01).

Study of irreversibly sickled cells in an animal model

Erythrocytes (RBCs) from six patients with sickle cell anemia were transfused to laboratory rats in order to study the intravascular survival of irreversibly sickled cells (ISCs). Fifteen minutes after transfusion, a mean of 48.8 percent (range 23-95 percent) of the ICSs injected were present in the rats' blood, a value that was significantly lower than that for the total population of sickle cell anemia erythrocytes transfused (mean 82.4 percent, range 36-114 percent). The intravascular half-life of ISCs was also lower (mean 0.83 hours ± 0.18 SD) than that observed for the total sickle cell anemia erythrocytes (mean 1.62 hours ± 0.19 SD) during the initial two hours of the transfusion experiments. The irreversibly sickled cells that remained in the rats' blood thereafter survived as well as those cells that were not irreversibly sickled. Severe hypoxia in the recipient animals did not appear to selectively remove ISCs from circulation. These data are consistent with heterogeneity of ISCs in terms of their intravascular viability. Some ISCs may have adapted to the stress of circulation despite their abnormal shape.