Characterization of Shear Stress Mediated Platelet Dysfunction: Data from an Ex Vivo Model for Extracorporeal Circulation and a Prospective Clinical Study.

Extracorporeal circulation (ECC) is frequently used in intensive care patients with impaired lung or cardiac function. Despite being a life-saving therapeutic option, ECC is associated with increased risk for both bleeding and thrombosis. The management of bleeding and thromboembolic events in ECC patients is still challenging partly due to the lack of information on the pathophysiological changes in hemostasis and platelet function during the procedure. Using a combination of an ex vivo model for shear stress and a sensitive and easy-to-use laboratory method, we analyzed platelet responsiveness during ECC. After shear stress simulation in an ex vivo closed-loop ECC model, we found a significantly decreased response of α-granules after activation with adenosine diphosphate and thrombin receptor activating peptide (TRAP-6) and CD63 expression after activation with TRAP-6. Mepacrine uptake was also significantly reduced in the ex vivo shear stress model.In the same line, platelets from patients under ECC with venovenous systems and venoarterial systems showed impaired CD62P degranulation after stimulation with ADP and TRAP-6 compared with healthy control on day 1, 6, and 10 after implantation of ECC. However, no correlation between platelet degranulation and the occurrence of bleeding or thromboembolic events was observed.The used whole blood flow cytometry with immediate fixation after drawing introduces a sensitive and easy-to-use method to determine platelet activation status and our data confirm that increased shear stress conditions under ECC can cause impaired degranulation of platelet.

Complement Proteins C5/C5a, Cathepsin D and Prolactin in Chondrocytes: A Possible Crosstalk in the Pathogenesis of Osteoarthritis.

INTRODUCTION: Both increased activity of the complement system (CS) and the role of the pituitary hormone prolactin (PRL) are implicated in osteoarthritis (OA) pathogenesis. Besides, Cathepsin D (CatD) activity is increased in the context of OA and can exert not only proteolytic but also non-proteolytic effects on cells. For the first time, possible crosstalk between two separate humoral systems: the CS and the PRL hormone systems in chondrocytes are examined together. METHODS: Primary human articular chondrocytes (hAC) were stimulated with complement protein C5 (10 µg /mL), PRL (25 ng/mL), CatD (100 ng/mL), or anaphylatoxin C5a (25 ng/mL) for 24 h or 72 h, while unstimulated cells served as controls. In addition, co-stimulations of C5 or PRL with CatD were carried out under the same conditions. The influence of the stimulants on cell viability, cell proliferation, and metabolic activity of hAC, the chondrosarcoma cell line OUMS-27, and endothelial cells of the human umbilical cord vein (HUVEC) was investigated. Gene expression analysis of C5a receptor (C5aR1), C5, complement regulatory protein CD59, PRL, PRL receptor (PRLR), CatD, and matrix metal-loproteinases (MMP)-13 were performed using real-time PCR. Also, collagen type (Col) I, Col II, C5aR1, CD59, and PRL were detected on protein level using immunofluorescence labeling. RESULTS: The stimulation of the hAC showed no significant impairment of the cell viability. C5, C5a, and PRL induced cell growth in OUMS-27 and HUVEC, but not in chondrocytes. CatD, as well as C5, significantly reduced the gene expression of CatD, C5aR1, C5, and CD59. PRLR gene expression was likewise impaired by C5, C5a, and PRL+CatD stimulation. On the protein level, CatD, as well as C5a, decreased Col II as well as C5aR1 synthesis. CONCLUSIONS: The significant suppression of the C5 gene expression under the influence of PRL+CatD and that of CD59 via PRL+/-CatD and conversely a suppression of the PRLR gene expression via C5 alone or C5a stimulation indicates an interrelation between the two mentioned systems. In addition, CatD and C5, in contrast to PRL, directly mediate possible negative feedback of their own gene expression.

Diagnosis of Platelet Function Disorders: A Challenge for Laboratories.

In patients with normal plasmatic coagulation and bleeding tendency, platelet function defect can be assumed. Congenital platelet function defects are rare. Much more commonly they are acquired. The clinical bleeding tendency of platelet function defects is heterogeneous, which makes diagnostic approaches difficult. During the years, a large variety of tests for morphological phenotyping and functional analysis have been developed. The diagnosis of platelet function defects is based on standardized bleeding assessment tools followed by a profound morphological evaluation of the platelets. Platelet function assays like light transmission aggregation, luminoaggregometry, and impedance aggregometry followed by flow cytometry are commonly used to establish the diagnosis in these patients. Nevertheless, despite great efforts, standardization of these tests is poor and in most cases, quality control is lacking. In addition, these tests are still limited to specialized laboratories. This review summarizes the approaches to morphologic phenotyping and platelet testing in patients with suspected platelet dysfunction, beginning with a standardized bleeding score and ending with flow cytometry testing. The diagnosis of a functional defect requires a good collaboration between the laboratory and the clinician.

Cardiac Fibroblast Growth Factor 23 Excess Does Not Induce Left Ventricular Hypertrophy in Healthy Mice.

Fibroblast growth factor (FGF) 23 is elevated in chronic kidney disease (CKD) to maintain phosphate homeostasis. FGF23 is associated with left ventricular hypertrophy (LVH) in CKD and induces LVH via klotho-independent FGFR4-mediated activation of calcineurin/nuclear factor of activated T cells (NFAT) signaling in animal models, displaying systemic alterations possibly contributing to heart injury. Whether elevated FGF23 per se causes LVH in healthy animals is unknown. By generating a mouse model with high intra-cardiac Fgf23 synthesis using an adeno-associated virus (AAV) expressing murine Fgf23 (AAV-Fgf23) under the control of the cardiac troponin T promoter, we investigated how cardiac Fgf23 affects cardiac remodeling and function in C57BL/6 wild-type mice. We report that AAV-Fgf23 mice showed increased cardiac-specific Fgf23 mRNA expression and synthesis of full-length intact Fgf23 (iFgf23) protein. Circulating total and iFgf23 levels were significantly elevated in AAV-Fgf23 mice compared to controls with no difference in bone Fgf23 expression, suggesting a cardiac origin. Serum of AAV-Fgf23 mice stimulated hypertrophic growth of neonatal rat ventricular myocytes (NRVM) and induced pro-hypertrophic NFAT target genes in klotho-free culture conditions in vitro. Further analysis revealed that renal Fgfr1/klotho/extracellular signal-regulated kinases 1/2 signaling was activated in AAV-Fgf23 mice, resulting in downregulation of sodium-phosphate cotransporter NaPi2a and NaPi2c and suppression of Cyp27b1, further supporting the bioactivity of cardiac-derived iFgf23. Of interest, no LVH, LV fibrosis, or impaired cardiac function was observed in klotho sufficient AAV-Fgf23 mice. Verified in NRVM, we show that co-stimulation with soluble klotho prevented Fgf23-induced cellular hypertrophy, supporting the hypothesis that high cardiac Fgf23 does not act cardiotoxic in the presence of its physiological cofactor klotho. In conclusion, chronic exposure to elevated cardiac iFgf23 does not induce LVH in healthy mice, suggesting that Fgf23 excess per se does not tackle the heart.

Relationship between admission Q waves and microvascular injury in patients with ST-elevation myocardial infarction treated with primary percutaneous coronary intervention.

BACKGROUND: Using comprehensive cardiac magnetic resonance (CMR) imaging in patients suffering from ST-elevation myocardial infarction (STEMI) treated with primary percutaneous coronary intervention (pPCI), we sought to investigate the association of admission Q waves with microvascular injury (microvascular obstruction (MVO) and intramyocardial haemorrhage (IMH)). METHODS: This prospective observational study included 195 STEMI patients treated with pPCI. Admission 12-lead electrocardiography was evaluated for the presence of pathological Q waves, defined as a Q wave duration of >30 ms and a depth of >0.1 mV. CMR was performed at 3 (interquartile range: 2-5) days after pPCI to determine infarct characteristics including MVO (late gadolinium enhancement) and IMH (T2* mapping). RESULTS: Admission Q waves were observed in 53% of patients (n = 104). These patients had a significantly lower BMI (p = 0.005), more frequent left anterior descending artery as culprit lesion (p = 0.005), were less frequent smokers (p = 0.048) and had higher rates of pre-interventional TIMI flow 0 (p = 0.018). Patients with Q waves showed a significantly larger infarct size (19%vs.12% of left ventricular mass,p < 0.001), lower ejection fraction (49%vs.54%,p = 0.001), worse global strain parameters (all p < 0.005) and more severe microvascular injury (MVO: 68%vs.34%,p < 0.001; IMH: 40%vs.20%,p = 0.002). Q waves remained associated with both MVO (odds ratio: 5.23, 95% confidence interval: 2.58 to 10.58,p < 0.001) and IMH (odds ratio: 3.94, 95% confidence interval: 1.83 to 8.46,p < 0.001) after adjusting for potential confounders (culprit lesion, pre-interventional TIMI flow 0, total ischemia time, ST-segment elevation). CONCLUSIONS: Admission Q waves, derived from the readily available ECG, emerged as independent early markers of CMR-determined microvascular injury in STEMI patients undergoing pPCI.

Aberrant ICOS+ -T cell differentiation in women with spontaneous preterm labor.

PROBLEM: Recent studies revealed appropriate differentiation of recent thymic emigrant (RTE)-regulatory T cells (Tregs) to be crucial for maintaining healthy pregnancy. Currently, the role of responder T cells (Tresps) is not known. METHOD OF STUDY: Six-color flow cytometric analysis was used to detect differences in the differentiation of highly proliferative inducible co-stimulatory (ICOS)+ -RTE-Tregs/Tresps and apoptosis-sensitive ICOS- -RTE-Tregs/Tresps into mature naïve (MN)-, CD31+ -memory and CD31- -memory Tregs/Tresps in women with spontaneous preterm labor (sPL) compared to healthy pregnancy. RESULTS: Healthy pregnancy was characterized by an increased differentiation of ICOS+ - and ICOS- -RTE-Tregs, as well as ICOS+ -RTE-Tresps via CD31+ -memory Tregs/Tresps into CD31- -memory Tregs/Tresps. Women with sPL showed an early interruption of RTE-Treg/Tresp differentiation. Instead, ICOS+ -MN-Tresps and partly ICOS- -MN-Tregs differentiated into CD31- -memory Tregs/Tresps, causing a significant reduction of both ICOS+ -Tregs and ICOS+ -Tresps, but an increase of ICOS- -Tresps within total CD4+ -T-helper cells. CONCLUSION: Aberrant differentiation of ICOS+ -T cells is associated with sPL.

The role of recent thymic emigrant-regulatory T-cell (RTE-Treg) differentiation during pregnancy.

During pregnancy, regulatory T cells (Tregs) have a key role in maternal immune tolerance to the semi-allogeneic fetus. Our previous results showed that the naive CD45RA(+)-Treg pool is functionally improved in pregnant women compared with non-pregnant women. Therefore, we examined the thymic output and differentiation of CD45RA(+)CD31(+) recent thymic emigrant (RTE)-Tregs during normal pregnancy and in the presence of preeclampsia. With the onset of pregnancy, the composition of the total CD4(+)CD127(low+/-)FoxP3(+)-Treg pool changed in the way that its percentage of RTE- and CD45RA(-)CD31(+)-memory Tregs decreased strongly, whereas that of the CD45RA(+)CD31(-)-mature naive (MN)-Tregs did not change and that of the CD45RA(-)CD31(-)-memory Tregs increased complementary. Thereby, the ratio of RTE-/MN-Tregs decreased from 1.0 to 0.7 leading to a significant increase in the suppressive activity of the naive CD45RA(+)-Treg pool. This effect was confirmed by re-assembling separated RTE- and MN-Tregs from non-pregnant women in the ratio of pregnant women. The suppressive activity of both separated naive Treg subsets was equally high in non-pregnant and pregnant women, but considerably reduced in preeclampsia patients, who showed significantly increased percentages of CD45RA(-)CD31(+)-memory Tregs, but decreased percentages of RTE- and MN-Tregs. Our results suggest a reduced thymic output of RTE-Tregs during pregnancy, which causes a decrease in the ratio of RTE-/MN-Tregs and thus an increase in the differentiation of RTE-Tregs towards CD45RA(-)CD31(-)-memory Tregs. Presumably, this differentiation of RTE-Tregs, which was impaired in preeclampsia patients, ensures the improved suppressive activity of the CD45RA(+)-naive Treg pool and thus retains the maintenance of pregnancy.

Salt sensitivity, anxiety, and irritability predict blood pressure increase over five years in healthy males.

Salt sensitivity and psychological factors are thought to be associated with a higher risk for the development of hypertension but data on the relation between age-related blood pressure increase and salt sensitivity or psychological factors are scarce. A total of 31 healthy young males who were previously classified with respect to salt sensitivity, mental stress reactivity, trait-anxiety, trait-anger, and irritability were followed up 4.8 years later by 24 hr ambulatory blood pressure monitoring (ABP). Our results showed anxiety and irritability correlated significantly with 24-hr ABP 4.8 years later (p < 0.05). The increase of diastolic blood pressure over 4.8 years was higher in salt-sensitive than salt-resistant subjects (p < 0.07). Heart rate and diastolic blood pressure correlated significantly with systolic and diastolic 24-hr ABP and blood pressure reactivity under mental stress with diastolic 24-hr ABP. A regression analysis that included cardiovascular and psychological factors yielded 34% (systolic ABP, p < 0.009) and 58% (diastolic ABP, p < 0.0001) of variance. We concluded that anxiety and irritability are important predictors of blood pressure increase over time in healthy males.

Reduced vagal activity in salt-sensitive subjects during mental challenge.

BACKGROUND: Salt-sensitive normotensive men exhibit an enhanced pressor and heart rate (HR) response to mental stress. Stress-induced HR acceleration may result from sympathetic activation or vagal withdrawal. We studied the importance of vagal withdrawal for the increased stress responsiveness of salt-sensitive subjects. METHODS: We studied cardiovascular reactivity to mental challenge in 17 salt-sensitive healthy white male students and 56 salt-resistant control subjects who were comparable with respect to age, body mass index, and physical fitness. Salt sensitivity was determined by a 2-week dietary protocol (20 mmol v 240 mmol sodium/day). Mental stress was induced by a computerized information-processing task (manometer test). Electrocardiogram and finger blood pressure (BP; Finapres, Ohmeda, Louisville, CO) were registered continuously to determine HR and interbeat-interval length. Time and frequency domain (spectral power) based measures of respiratory-related heart rate variability (HRV) were calculated to estimate vagal cardiac control; diastolic BP reactivity was assessed to estimate peripheral sympathetic effects. RESULTS: Stress-induced increase in HR was higher in salt-sensitive than in salt-resistant subjects. Salt-sensitive subjects, in comparison to salt-resistant subjects, showed significantly reduced respiratory-related HRV during baseline and mental stress conditions (P <.01). The increase in diastolic BP during mental challenge was significantly greater in salt-sensitive subjects (P <.05). CONCLUSIONS: Our findings suggest reduced vagal and increased sympathetic tone during mental challenge in salt-sensitive subjects. Altered autonomic nervous system function may contribute to later development of hypertension in salt-sensitive individuals.