Increasing creatine kinase activity protects against hypoxia / reoxygenation injury but not against anthracycline toxicity in vitro

Identification of potential biomarkers for cerebral palsy and the development of prediction models

Cerebral palsy (CP) is a prevalent motor disorder originating from early brain injury or malformation, with significant variability in its clinical presentation and etiology. Early diagnosis and personalized therapeutic interventions are hindered by the lack of reliable biomarkers. This study aims to identify potential biomarkers for cerebral palsy and develop predictive models to enhance early diagnosis and prognosis. We conducted a comprehensive bioinformatics analysis of gene expression profiles in muscle samples from CP patients to identify candidate biomarkers. Six key genes (CKMT2, TNNT2, MYH4, MYH1, GOT1, and LPL) were validated in an independent cohort, and potential biological pathways and molecular networks involved in CP pathogenesis were analyzed. The importance of processes such as functional regulation, energy metabolism, and cell signaling pathways in the muscles of CP patients was emphasized. Predictive models of muscle sample biomarkers related to CP were developed and visualized. Calibration curves and receiver operating characteristic analysis demonstrated that the predictive models exhibit high sensitivity and specificity in distinguishing individuals at risk of CP. The identified biomarkers and developed prediction models offer significant potential for early diagnosis and personalized management of CP. Future research should focus on validating these biomarkers in larger cohorts and integrating them into clinical practice to improve outcomes for individuals with CP.

Maintaining energy provision in the heart: the creatine kinase system in ischaemia-reperfusion injury and chronic heart failure

The non-stop provision of chemical energy is of critical importance to normal cardiac function, requiring the rapid turnover of ATP to power both relaxation and contraction. Central to this is the creatine kinase (CK) phosphagen system, which buffers local ATP levels to optimise the energy available from ATP hydrolysis, to stimulate energy production via the mitochondria and to smooth out mismatches between energy supply and demand. In this review, we discuss the changes that occur in high-energy phosphate metabolism (i.e., in ATP and phosphocreatine) during ischaemia and reperfusion, which represents an acute crisis of energy provision. Evidence is presented from preclinical models that augmentation of the CK system can reduce ischaemia-reperfusion injury and improve functional recovery. Energetic impairment is also a hallmark of chronic heart failure, in particular, down-regulation of the CK system and loss of adenine nucleotides, which may contribute to pathophysiology by limiting ATP supply. Herein, we discuss the evidence for this hypothesis based on preclinical studies and in patients using magnetic resonance spectroscopy. We conclude that the correlative evidence linking impaired energetics to cardiac dysfunction is compelling; however, causal evidence from loss-of-function models remains equivocal. Nevertheless, proof-of-principle studies suggest that augmentation of CK activity is a therapeutic target to improve cardiac function and remodelling in the failing heart. Further work is necessary to translate these findings to the clinic, in particular, a better understanding of the mechanisms by which the CK system is regulated in disease.

The Impact of Normobaric Hypoxia and Intermittent Hypoxic Training on Cardiac Biomarkers in Endurance Athletes: A Pilot Study

This study explores the effects of normobaric hypoxia and intermittent hypoxic training (IHT) on the physiological condition of the cardiac muscle in swimmers. Hypoxia has been reported to elicit both beneficial and adverse changes in the cardiovascular system, but its impact on the myocardium during acute exercise and altitude/hypoxic training remains less understood. We aimed to determine how a single bout of intense interval exercise and a four-week period of high-intensity endurance training under normobaric hypoxia affect cardiac marker activity in swimmers. Sixteen young male swimmers were divided into two groups: one undergoing training in hypoxia and the other in normoxia. Cardiac markers, including troponin I and T (cTnI and cTnT), heart-type fatty acid-binding protein (H-FABP), creatine kinase-MB isoenzyme (CK-MB), and myoglobin (Mb), were analyzed to assess the myocardium's response. We found no significant differences in the physiological response of the cardiac muscle to intense physical exertion between hypoxia and normoxia. Four weeks of IHT did not alter the resting levels of cTnT, cTnI, and H-FABP, but it resulted in a noteworthy decrease in the resting concentration of CK-MB, suggesting enhanced cardiac muscle adaptation to exercise. In contrast, a reduction in resting Mb levels was observed in the control group training in normoxia. These findings suggest that IHT at moderate altitudes does not adversely affect cardiac muscle condition and may support cardiac muscle adaptation, affirming the safety and efficacy of IHT as a training method for athletes.

SERCA2 phosphorylation at serine 663 is a key regulator of Ca2+ homeostasis in heart diseases

Despite advances in cardioprotection, new therapeutic strategies capable of preventing ischemia-reperfusion injury of patients are still needed. Here, we discover that sarcoplasmic/endoplasmic reticulum Ca2+ ATPase (SERCA2) phosphorylation at serine 663 is a clinical and pathophysiological event of cardiac function. Indeed, the phosphorylation level of SERCA2 at serine 663 is increased in ischemic hearts of patients and mouse. Analyses on different human cell lines indicate that preventing serine 663 phosphorylation significantly increases SERCA2 activity and protects against cell death, by counteracting cytosolic and mitochondrial Ca2+ overload. By identifying the phosphorylation level of SERCA2 at serine 663 as an essential regulator of SERCA2 activity, Ca2+ homeostasis and infarct size, these data contribute to a more comprehensive understanding of the excitation/contraction coupling of cardiomyocytes and establish the pathophysiological role and the therapeutic potential of SERCA2 modulation in acute myocardial infarction, based on the hotspot phosphorylation level of SERCA2 at serine 663 residue.

Proteomics as a Tool for the Study of Mitochondrial Proteome, Its Dysfunctionality and Pathological Consequences in Cardiovascular Diseases

The focus of this review is on the proteomic approaches applied to the study of the qualitative/quantitative changes in mitochondrial proteins that are related to impaired mitochondrial function and consequently different types of pathologies. Proteomic techniques developed in recent years have created a powerful tool for the characterization of both static and dynamic proteomes. They can detect protein-protein interactions and a broad repertoire of post-translation modifications that play pivotal roles in mitochondrial regulation, maintenance and proper function. Based on accumulated proteomic data, conclusions can be derived on how to proceed in disease prevention and treatment. In addition, this article will present an overview of the recently published proteomic papers that deal with the regulatory roles of post-translational modifications of mitochondrial proteins and specifically with cardiovascular diseases connected to mitochondrial dysfunction.

An in vitro approach to understand contribution of kidney cells to human urinary extracellular vesicles

Extracellular vesicles (EV) are membranous particles secreted by all cells and found in body fluids. Established EV contents include a variety of RNA species, proteins, lipids and metabolites that are considered to reflect the physiological status of their parental cells. However, to date, little is known about cell-type enriched EV cargo in complex EV mixtures, especially in urine. To test whether EV secretion from distinct human kidney cells in culture differ and can recapitulate findings in normal urine, we comprehensively analysed EV components, (particularly miRNAs, long RNAs and protein) from conditionally immortalised human kidney cell lines (podocyte, glomerular endothelial, mesangial and proximal tubular cells) and compared to EV secreted in human urine. EV from cell culture media derived from immortalised kidney cells were isolated by hydrostatic filtration dialysis (HFD) and characterised by electron microscopy (EM), nanoparticle tracking analysis (NTA) and Western blotting (WB). RNA was isolated from EV and subjected to miRNA and RNA sequencing and proteins were profiled by tandem mass tag proteomics. Representative sets of EV miRNAs, RNAs and proteins were detected in each cell type and compared to human urinary EV isolates (uEV), EV cargo database, kidney biopsy bulk RNA sequencing and proteomics, and single-cell transcriptomics. This revealed that a high proportion of the in vitro EV signatures were also found in in vivo datasets. Thus, highlighting the robustness of our in vitro model and showing that this approach enables the dissection of cell type specific EV cargo in biofluids and the potential identification of cell-type specific EV biomarkers of kidney disease.

Serum Cardiac and Skeletal Muscle Marker Changes in Repetitive Breath-hold Diving

Background

Breath-hold diving (BH-diving) is associated to extreme environmental conditions, prolonged physical activity, and complex adaptation mechanisms to supply enough O₂ to vital organs. Consequently, one of the biggest effects could be an increased exercise-induced muscle fatigue, in both skeletal and cardiac muscles that can induce an increase of muscles injury markers including creatine kinase (CK), aspartate transferase (AST), and alanine transferase (ALT) when concerning the skeletal muscle, cardiac creatine kinase isoenzyme (CK-MBm) and cardiac troponin I (cTnI) when concerning the cardiac muscle, and lactate dehydrogenase (LDH) as index of muscle stress. The aim of this study is to investigate serum cardiac and skeletal muscle markers before and after a BH-diving training session.

Results

We found statistically significant increases of CK (T0: 136.1% p < 0.0001; T1: 138.5%, p < 0.0001), CK-MBm (T0: 145.1%, p < 0.0001; T1: 153.2%, p < 0.0001) LDH (T0: 110.4%, p < 0.0003; T1: 110.1%, p < 0.0013) in both T0 and T1 blood samples, as compared to basal value. AST showed a statistically significant increase only at T0 (106.8%, p < 0.0007) while ALT did not exhibit statistically significant changes. We did not find any changes in cTnI levels between pre-dive and post-dive samples.

Conclusions

Our data seem to indicate that during a BH-diving training session, skeletal and cardiac muscles react to physical effort releasing stress-related substances. Although the peculiar nature of BH-diving makes it difficult to understand if our results are related only to exercise induced muscle adaptation or whether acute hypoxia or a response to environmental changes (pressure) play a role to explain the observed changes, further studies are needed to better understand if these biomarker changes are linked to physical exercise or to acute hypoxia, or if both conditions play a role.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40798-021-00349-z.

Conceptus metabolomic profiling reveals stage-specific phenotypes leading up to pregnancy recognition in cattle†

Reproductive efficiency in livestock is a major driver of sustainable food production. The poorly understood process of ruminant conceptus elongation (a) prerequisites maternal pregnancy recognition, (b) is essential to successful pregnancy establishment, and (c) coincides with a period of significant conceptus mortality. Conceptuses at five key developmental stages between Days 8-16 were recovered and cultured in vitro for 6 h prior to conditioned media analysis by untargeted ultrahigh-performance liquid chromatography tandem mass spectroscopy. This global temporal biochemical interrogation of the ex situ bovine conceptus unearths two antithetical stage-specific metabolic phenotypes during tubular (metabolically retentive) vs. filamentous (secretory) development. Moreover, the retentive conceptus phenotype on Day 14 coincides with an established period of elevated metabolic density in the uterine fluid of heifers with high systemic progesterone-a model of accelerated conceptus elongation. These data, combined, suggest a metabolic mechanism underpinning conceptus elongation, thereby enhancing our understanding of the biochemical reciprocity of maternal-conceptus communication, prior to maternal pregnancy recognition.

Phosphorylation in Novel Mitochondrial Creatine Kinase Tyrosine Residues Render Cardioprotection against Hypoxia/Reoxygenation Injury

Objective

Ischemic cardiomyopathy (ICM) is the leading cause of heart failure. Proteomic and genomic studies have demonstrated ischemic preconditioning (IPC) can assert cardioprotection against ICM through mitochondrial function regulation. Considering IPC is conducted in a relatively brief period, regulation of protein expression also occurs very rapidly, highlighting the importance of protein function modulation by post-translational modifications. This study aimed to identify and analyze novel phosphorylated mitochondrial proteins that can be harnessed for therapeutic strategies for preventing ischemia/reperfusion (I/R) injury.

Methods

Sprague-Dawley rat hearts were used in an ex vivo Langendorff system to simulate normal perfusion, I/R, and IPC condition, after which the samples were prepared for phosphoproteomic analysis. Employing human cardiomyocyte AC16 cells, we investigated the cardioprotective role of CKMT2 through overexpression and how site-directed mutagenesis of putative CKMT2 phosphorylation sites (Y159A, Y255A, and Y368A) can affect cardioprotection by measuring CKMT2 protein activity, mitochondrial function and protein expression changes.

Results

The phosphoproteomic analysis revealed dephosphorylation of mitochondrial creatine kinase (CKMT2) during ischemia and I/R, while preserving its phosphorylated state during IPC. CKMT2 overexpression conferred cardioprotection against hypoxia/reoxygenation (H/R) by increasing cell viability and mitochondrial adenosine triphosphate level, preserving mitochondrial membrane potential, and reduced reactive oxygen species (ROS) generation, while phosphomutations, especially in Y368, nullified cardioprotection by significantly reducing cell viability and increasing ROS production during H/R. CKMT2 overexpression increased mitochondrial function by mediating the proliferator-activated receptor γ coactivator-1α/estrogen-related receptor-α pathway, and these effects were mostly inhibited by Y368A mutation.

Conclusion

These results suggest that regulation of quantitative expression and phosphorylation site Y368 of CKMT2 offers a unique mechanism in future ICM therapeutics.

Use of Creatine and Creatinine to Minimize Doxorubicin-Induced Cytotoxicity in Cardiac and Skeletal Muscle Myoblasts

Doxorubicin (DOX), an effective anticancer agent, can damage cardiac and skeletal muscle tissue via excessive generation of reactive oxygen species (ROS). Supplemental creatine (Cr) has been shown to have a therapeutic role in disease states characterized by increased oxidative stress. To investigate the effects of Cr and creatinine (CrN) on DOX-induced cytotoxicity. Cultured L6 and H9C2 myoblasts were exposed to 25 μM DOX, 10 mM Cr, 10 mM CrN, 25 μM DOX + 10 mM Cr, 25 μM DOX + 10 mM CrN, or control media for 12 h. Viability was assessed using Confocal and Widefield imaging. Immunoblotting was used to determine protein expression. Viability was lowest in the DOX-treated group regardless of cell type; however, when DOX was combined with Cr or CrN, viability was improved. Levels of oxidative stress, as measured by 4-hydroxynonenal (4HNE), were significantly (p < 0.05) higher in the DOX treated cells vs. controls; however, Cr + DOX and CrN + DOX significantly lowered 4HNE levels compared to DOX-treated cells. Creatine kinase (CK), a key marker of cellular damage, was significantly higher in DOX-treated H9c2 cells vs. controls. However, Cr or CrN in combination with DOX, resulted in no significant differences in CK vs. controls. Supplementation with Cr or CrN may preserve cell viability during DOX treatment.

Non-invasive investigation of myocardial energetics in cardiac disease using 31P magnetic resonance spectroscopy

Cardiac metabolism and function are intrinsically linked. High-energy phosphates occupy a central and obligate position in cardiac metabolism, coupling oxygen and substrate fuel delivery to the myocardium with external work. This insight underlies the widespread clinical use of ischaemia testing. However, other deficits in high-energy phosphate metabolism (not secondary to supply-demand mismatch of oxygen and substrate fuels) may also be documented, and are of particular interest when found in the context of structural heart disease. This review introduces the scope of deficits in high-energy phosphate metabolism that may be observed in the myocardium, how to assess for them, and how they might be interpreted.

Scriptaid/exercise-induced lysine acetylation is another type of posttranslational modification occurring in titin

Titin serves important functions in skeletal muscle during exercise, and posttranslational modifications of titin participate in the regulation of titin-based sarcomeric functions. Scriptaid has exercise-like effects through the inhibition of HDAC and regulatory acetylation of proteins. However, it remains mostly unclear if exercise could result in titin’s acetylation and whether Scriptaid could regulate acetylation of titin. We treated C57BL/6 mice with 6-wk treadmill exercise and 6-wk Scriptaid administration to explore Scriptaid’s effects on mice exercise capacity and whether Scriptaid administration/exercise could induce titin’s acetylation modification. An exercise endurance test was conducted to explore their effects on mice exercise capacity, and proteomic studies were conducted with gastrocnemius muscle tissue of mice from different groups to explore titin’s acetylation modification. We found that Scriptaid and exercise did not change titin’s protein expression, but they did induce acetylation modification changes of titin. In total, 333 acetylated lysine sites were identified. Exercise changed the acetylation levels of 33 lysine sites of titin, whereas Scriptaid changed acetylation levels of 31 titin lysine sites. Exercise treatment and Scriptaid administration shared 11 lysine sites. In conclusion, Scriptaid increased exercise endurance of mice by increasing the time mice spent running to fatigue. Acetylation is a common type of posttranslational modification of titin, and exercise/Scriptaid changed the acetylation levels of titin and titin-interacting proteins. Most importantly, titin may be a mediator through which Scriptaid and exercise modulate the properties and functions of exercise-induced skeletal muscle at the molecular level.

NEW & NOTEWORTHY Scriptaid administration increased mouse exercise endurance. Acetylation is another type of posttranslational modification of titin. Scriptaid/exercise changed acetylation levels of titin and titin-interacting proteins. Titin may mediate exercise-induced skeletal muscle properties and functions.

Involvement of the phosphoryl transfer network in gill bioenergetic imbalance of pacamã (Lophiosilurus alexandri) subjected to hypoxia: notable participation of creatine kinase

Hypoxia is among the most critical environmental stressors for fish in aquatic environments, and several energetic alterations have been associated with it. The aim of the present study was to evaluate the involvement of the phosphoryl transfer network and its effects on adenosine triphosphate (ATP)-dependent enzymes during hypoxia, as well as the role of oxidative stress in the activity of the phosphoryl transfer network in pacamã (Lophiosilurus alexandri) subjected to severe hypoxia. Branchial creatine kinase (CK; cytosolic and mitochondrial fractions), adenylate kinase (AK), and pyruvate kinase (PK) activities were inhibited after 72 h of exposure to hypoxia compared to their respective normoxia groups, and remained low (except for AK) after 24 and 72 h of re-oxygenation. Activities of the branchial sodium-potassium pump (Na⁺, K⁺-ATPase) and proton pump (H⁺-ATPase) were inhibited in fish exposed to 72 h of hypoxia compared to the normoxia group, remained inhibited after 24 h of re-oxygenation, and were restored to physiological levels after 72 h of re-oxygenation. Levels of branchial reactive oxygen species (ROS) were higher in fish exposed to hypoxia for 72 h compared to the normoxia group, and increased during re-oxygenation. Lipid peroxidation (LOOH) levels were higher in fish subjected to 72 h of hypoxia compared to the normoxia group, and remained higher during re-oxygenation. On the other hand, protein sulfhydryl (PSH) levels were lower in fish exposed to hypoxia for 72 h compared to the normoxia group, and remained low during re-oxygenation. Based on this evidence, inhibition of the activities of enzymes belonging to phosphoryl transfer network contributed to impairing energetic homeostasis linked to ATP production and ATP utilization in gills of pacamã subjected to hypoxia, and remained inhibited during re-oxygenation (except AK activity). Moreover, inhibition of the phosphoryl transfer network impaired activity of ATP-dependent enzymes, which can be mediated by ROS overproduction, lipid peroxidation, and oxidation of SH groups.

Overexpression of mitochondrial creatine kinase preserves cardiac energetics without ameliorating murine chronic heart failure

Mitochondrial creatine kinase (Mt-CK) is a major determinant of cardiac energetic status and is down-regulated in chronic heart failure, which may contribute to disease progression. We hypothesised that cardiomyocyte-specific overexpression of Mt-CK would mitigate against these changes and thereby preserve cardiac function. Male Mt-CK overexpressing mice (OE) and WT littermates were subjected to transverse aortic constriction (TAC) or sham surgery and assessed by echocardiography at 0, 3 and 6 weeks alongside a final LV haemodynamic assessment. Regardless of genotype, TAC mice developed progressive LV hypertrophy, dilatation and contractile dysfunction commensurate with pressure overload-induced chronic heart failure. There was a trend for improved survival in OE-TAC mice (90% vs 73%, P = 0.08), however, OE-TAC mice exhibited greater LV dilatation compared to WT and no functional parameters were significantly different under baseline conditions or during dobutamine stress test. CK activity was 37% higher in OE-sham versus WT-sham hearts and reduced in both TAC groups, but was maintained above normal values in the OE-TAC hearts. A separate cohort of mice received in vivo cardiac ³¹P-MRS to measure high-energy phosphates. There was no difference in the ratio of phosphocreatine-to-ATP in the sham mice, however, PCr/ATP was reduced in WT-TAC but preserved in OE-TAC (1.04 ± 0.10 vs 2.04 ± 0.22; P = 0.007). In conclusion, overexpression of Mt-CK activity prevented the changes in cardiac energetics that are considered hallmarks of a failing heart. This had a positive effect on early survival but was not associated with improved LV remodelling or function during the development of chronic heart failure.

Over-expression of mitochondrial creatine kinase in the murine heart improves functional recovery and protects against injury following ischaemia-reperfusion

Aims

Mitochondrial creatine kinase (MtCK) couples ATP production via oxidative phosphorylation to phosphocreatine in the cytosol, which acts as a mobile energy store available for regeneration of ATP at times of high demand. We hypothesized that elevating MtCK would be beneficial in ischaemia-reperfusion (I/R) injury.

Methods and results

Mice were created over-expressing the sarcomeric MtCK gene with αMHC promoter at the Rosa26 locus (MtCK-OE) and compared with wild-type (WT) littermates. MtCK activity was 27% higher than WT, with no change in other CK isoenzymes or creatine levels. Electron microscopy confirmed normal mitochondrial cell density and mitochondrial localization of transgenic protein. Respiration in isolated mitochondria was unaltered and metabolomic analysis by 1 H-NMR suggests that cellular metabolism was not grossly affected by transgene expression. There were no significant differences in cardiac structure or function under baseline conditions by cine-MRI or LV haemodynamics. In Langendorff-perfused hearts subjected to 20 min ischaemia and 30 min reperfusion, MtCK-OE exhibited less ischaemic contracture, and improved functional recovery (Rate pressure product 58% above WT; P < 0.001). These hearts had reduced myocardial infarct size, which was confirmed in vivo: 55 ± 4% in WT vs. 29 ± 4% in MtCK-OE; P < 0.0001). Isolated cardiomyocytes from MtCK-OE hearts exhibited delayed opening of the mitochondrial permeability transition pore (mPTP) compared to WT, which was confirmed by reduced mitochondrial swelling in response to calcium. There was no detectable change in the structural integrity of the mitochondrial membrane.

Conclusions

Modest elevation of MtCK activity in the heart does not adversely affect cellular metabolism, mitochondrial or in vivo cardiac function, but modifies mPTP opening to protect against I/R injury and improve functional recovery. Our findings support MtCK as a prime therapeutic target in myocardial ischaemia.

Comprehensive Evaluation of White Matter Damage and Neuron Death and Whole-Transcriptome Analysis of Rats With Chronic Cerebral Hypoperfusion

Background/Aims

Chronic cerebral hypoperfusion (CCH) is induced by chronic deficit of brain perfusion, contributes to a persistent or progressive cognitive dysfunction, which is characterized by diverse neuropathological manifestations. There are currently no effective medications available. White matter damage (WMD) and cortical neuron death may be caused by CCH, which are related to cognitive impairment, while the underlying molecular mechanisms remain unclear. In the study, a database of the transcriptome level was built to determine potential biomarkers in cortex of CCH.

Methods

CCH was induced in male Sprague-Dawley rats by permanent occlusion of the bilateral common carotid arteries. Rats were randomly divided into three groups: Sham-operated group (n = 24), the 4th and 8th week of CCH groups (total = 56, n = 28 for each group). Cognitive function was evaluated using the Morris water maze task. WMD and neuron damage were detected using diffusion tensor imaging and histological analysis, respectively. Western blotting analysis of various markers was used to examine neuronal death. Whole-transcriptome microarray was performed to assess mRNA, circRNA, and lncRNA expression profiles at 4th and 8th weeks after CCH. Diversified bioinformatic tools were performed to analyze and predict the key biological processes and signaling pathways of differentially expressed RNAs and co-expressed potential target genes. Co-expression networks of mRNA–circRNA–miRNA and lncRNA–mRNA were constructed.

Results

Compared to the sham group, cognitive impairment, disintegration of white matter, blood-brain barrier damage and neuron death were induced by CCH. Neuron death including apoptosis and necroptosis might occur in the cortex of CCH. We constructed the regulatory networks of whole-transcriptomic including differentially expressed mRNAs, circRNAs, and lncRNAs, and related biological functions and pathways involved in neurological disease, cell death and survival, energy and metabolism, et al. Our results also indicated that Cyr61 mRNA may play a role in the CCH-related cortical neuronal death.

Conclusion

WMD and cortical neuronal death are worthy of attention in the pathogenesis of CCH. Additionally, the present results provide potential evidence at the whole-transcription level for CCH, offering candidate biomarkers and therapeutic targets.

Cardioprotective reperfusion strategies differentially affect mitochondria: Studies in an isolated rat heart model of donation after circulatory death (DCD)

Donation after circulatory death (DCD) holds great promise for improving cardiac graft availability; however, concerns persist regarding injury following warm ischemia, after donor circulatory arrest, and subsequent reperfusion. Application of preischemic treatments is limited for ethical reasons; thus, cardioprotective strategies applied at graft procurement (reperfusion) are of particular importance in optimizing graft quality. Given the key role of mitochondria in cardiac ischemia-reperfusion injury, we hypothesize that 3 reperfusion strategies-mild hypothermia, mechanical postconditioning, and hypoxia, when briefly applied at reperfusion onset-provoke mitochondrial changes that may underlie their cardioprotective effects. Using an isolated, working rat heart model of DCD, we demonstrate that all 3 strategies improve oxygen-consumption-cardiac-work coupling and increase tissue adenosine triphosphate content, in parallel with increased functional recovery. These reperfusion strategies, however, differentially affect mitochondria; mild hypothermia also increases phosphocreatine content, while mechanical postconditioning stimulates mitochondrial complex I activity and reduces cytochrome c release (marker of mitochondrial damage), whereas hypoxia upregulates the expression of peroxisome proliferator-activated receptor-gamma coactivator (regulator of mitochondrial biogenesis). Characterization of the role of mitochondria in cardioprotective reperfusion strategies should aid in the identification of new, mitochondrial-based therapeutic targets and the development of effective reperfusion strategies that could ultimately facilitate DCD heart transplantation.

The creatine kinase system as a therapeutic target for myocardial ischaemia-reperfusion injury

Restoring blood flow following an acute myocardial infarction saves lives, but results in tissue damage due to ischaemia–reperfusion injury (I/R). Ameliorating this damage is a major research goal to improve recovery and reduce subsequent morbidity due to heart failure. Both the ischaemic and reperfusion phases represent crises of cellular energy provision in which the mitochondria play a central role. This mini-review will explore the rationale and therapeutic potential of augmenting the creatine kinase (CK) energy shuttle, which constitutes the primary short-term energy buffer and transport system in the cardiomyocyte. Proof-of-principle data from several transgenic mouse models have demonstrated robust cardioprotection by either raising myocardial creatine levels or by overexpressing specific CK isoforms. The effect on cardiac function, high-energy phosphates and myocardial injury will be discussed and possible directions for future research highlighted. We conclude that the CK system represents a viable target for therapeutic intervention in I/R injury; however, much needed translational studies will require the development of new pharmacological tools.

Expression of atresia biomarkers in granulosa cells after ovarian stimulation in heifers

The use of younger gamete donors in dairy cattle genetic selection programs significantly accelerates genetic gains by decreasing the interval between generations. Ovarian stimulation (OS) and the practice of follicle-stimulating hormone (FSH) withdrawal, also known as coasting, are intensively used in pre-pubertal heifers without detrimental effects on subsequent reproductive performance but generally with lower embryo yields. However, recent data from embryo transfer programs showed similar embryo yields in younger and sexually mature animals but with a significant difference in the coasting period. The aim of the present study was to identify a set of granulosa cell biomarkers capable of distinguishing optimal follicle differentiation from late differentiation and atresia in order to assess the differences in coasting dynamics between pre- and post-pubertal donors. We integrated transcriptomic data sets from a public depository and used vote counting meta-analysis in order to elucidate the molecular changes occurring in granulosa cells during late follicle differentiation and atresia. The meta-analysis revealed the gene expression associated with follicle demise, and most importantly, identified potential biomarkers of that status in bovine granulosa cells. The comparison of the expression of six biomarkers between pre- and post-pubertal donors revealed that younger donors had more signs of atresia after the same period of coasting. We found different follicular dynamics following coasting in younger donors. It is possible that younger donors are less capable to sustain follicular survival most likely due to insufficient luteinizing hormone signaling. In summary, the pre-pubertal status influences follicular dynamics and reduces the oocyte developmental competence curve following OS and FSH withdrawal in heifers.