The endogenous thrombin potential in patients with left ventricular assist device or heart transplant.

Background: The Heartmate 3 (HM 3) is a left ventricular assist device featuring less shear stress, milder acquired von Willebrand syndrome, and fewer bleeding incidences than its predecessor the Heartmate II (HM II). The novel surface coating of the HM 3 suggests less contact activation of plasmatic coagulation. We hypothesized that patients with HM 3 exhibit fewer aberrations in their thrombin potential than patients with HM II. We compared these results with the thrombin potential of patients with heart transplantation (HTX). Methods: Thrombin generation in plasma samples of patients with HM II (n = 16), HM 3 (n = 20), and HTX (n = 13) was analyzed 3 days after implantation/transplantation and after long-term support (3-24 months) with HM II (n = 16) or HM 3 (n = 12) using calibrated automated thrombography. Heparin in postoperative samples was antagonized with polybrene. Results: Three days postoperatively HM II patients exhibited a lower endogenous thrombin potential (ETP) than HM 3 and HTX patients (HM II: 947 ± 291 nM*min; HM 3: 1231 ± 176 nM*min; HTX: 1376 ± 162 nM*min, p < 0.001) and a lower velocity index of thrombin generation (HM II: 18.74 ± 10.90 nM/min; HM 3: 32.41 ± 9.51 nM/min; HTX: 37.65 ± 9.41 nM/min, p < 0.01). Subtle differences in the thrombin generation profiles remained in HM II and HM 3 patients under long-term support (Velocity Index: HM II: 38.70 ± 28.46 nM/min; HM 3: 73.32 ± 32.83 nM/min, p < 0.05). Prothrombin fragments 1 + 2 were higher in HM II than in HM 3 patients (HM II: 377.7 ± 208.4 pM; HM 3: 202.1 ± 87.7 pM, p < 0.05) and correlated inversely with the ETP (r = -0.584, p < 0.05). Conclusion: We observed a more aberrant thrombin generation in HM II than in HM 3 despite comparable anticoagulation and routine parameters. A trend toward lower values was still observable in HM 3 compared to HTX patients. Calibrated automated thrombography may be a good tool to monitor the coagulation state of these patients and guide anticoagulation in the future.

Mild Acquired von Willebrand Syndrome and Cholestasis in Pediatric and Adult Patients with Fontan Circulation.

Background: Hemodynamic alterations in Fontan patients (FP) are associated with hemostatic dysbalance and Fontan-associated liver disease. Studies of other hepatopathologies indicate an interplay between cholestasis, tissue factor (TF), and von Willebrand factor (VWF). Hence, we hypothesized a relationship between the accumulation of bile acids (BA) and these hemostatic factors in FP. Methods: We included 34 FP (Phenprocoumon n = 15, acetylsalicylic acid (ASA) n = 16). BA were assessed by mass spectrometry. TF activity and VWF antigen (VWF:Ag) were determined by chromogenic assays. VWF collagen-binding activity (VWF:CB) was assessed via ELISA. Results: Cholestasis was observed in 6/34 FP (total BA ≥ 10 µM). BA levels and TF activity did not correlate (p = 0.724). Cholestatic FP had lower platelet counts (p = 0.013) from which 5/6 FP were not treated with ASA. VWF:Ag levels were increased in 9/34 FP and significantly lower in FP receiving ASA (p = 0.044). Acquired von Willebrand syndrome (AVWS) was observed in 10/34-FP, with a higher incidence in cholestatic FP (4/6) (p = 0.048). Conclusions: Cholestasis is unexpectedly infrequent in FP and seems to be less frequent under ASA therapy. Therefore, ASA may reduce the risk of advanced liver fibrosis. FP should be screened for AVWS to avoid bleeding events, especially in cholestatic states.

Neonatal Platelets: Lower G12/13 Expression Contributes to Reduced Secretion of Dense Granules.

Despite fully functional primary hemostasis, platelets of healthy neonates exhibit hypoaggregability and secretion defects, which may be adaptations to specific requirements in this developmental stage. The etiologies for reduced signal transduction vary with the type of agonist. The discovered peculiarities are lower receptor densities, reduced calcium mobilization, and functional impairments of G proteins. Reduced secretion of dense granules has been attributed to lower numbers of granules. Signaling studies with adult platelets have shown a regulating effect of the G12/13 signaling pathway on dense granule secretion via RhoA. We comparatively analyzed secretion profiles using flow cytometry and expression levels of Gq, Gi, and G12/13 using Western blot analysis in platelets from cord blood and adults. Furthermore, we evaluated Rho activation after in vitro platelet stimulation with thrombin using a pulldown assay. We observed a markedly reduced expression of the dense granule marker CD63 on neonatal platelets after thrombin stimulation. Gα12/13 expression was significantly decreased in neonatal platelets and correlated with lower Rho activation after thrombin stimulation. We conclude that lower expression of G12/13 in neonatal platelets results in attenuated activation of Rho and may contribute to reduced secretion of dense granules after exposure to thrombin.

The Covert Surge: Murine Bile Acid Levels Are Associated With Pruritus in Pediatric Autoimmune Sclerosing Cholangitis.

Objectives: The exact etiology of pruritus in chronic cholestasis is unknown. Pruritus intensity does not correlate with common biochemical indices and there is a lack of biomarkers guiding diagnosis and treatment. We explored profiles of bile acids (BA) and muricholic acids (MCA) as well as autotaxin (ATX) antigen levels as potential circulating biomarkers of pruritus in pediatric patients. Methods: In 27 pediatric cholestatic patients [autoimmune sclerosing cholangitis (ASC) n = 20 (with pruritus n = 6, without pruritus n = 14); progressive familial intrahepatic cholestasis (PFIC) n = 7 (with pruritus n = 5, without pruritus n = 2)] and 23 age-matched controls pruritus was assessed by a visual analog scale of pruritus (PVAS). We obtained profiles of serum human BA including MCA using a mass-spectrometry assay and ATX antigen levels with a commercial ELISA. Results: PFIC and ASC patients exhibited significantly higher BA-, and MCA levels, than healthy controls, but only PFIC patients showed elevated ATX antigen levels higher [median: 1,650 ng/ml, interquartile rang (IQR): 776.9-3,742] compared to controls (median: 315.9 ng/ml, IQR: 251.1-417.2; PFIC p = 0.0003). ASC patients with pruritus showed only a minor increase in total BA (tBA) levels (median: 76.5 µmol/L, IQR: 54.7-205), but strikingly higher T-conjugated BA (median: 16.4 µmol/L, IQR: 8.9-41.4) and total MCA (tMCA) (median: 1.15 µmol/L, IQR: 0.77-2.44) levels compared to ASC patients without pruritus (tBA median: 24.3 µmol/L, IQR: 16.2-80.8; p < 0.0408; T-conjugated BA median: 1.3 µmol/L, IQR: 0.8-4.9; p = 0.0023; tMCA median: 0.30 µmol/L, IQR: 0.13-0.64, p = 0.0033). BA/MCA profiles distinctly differed depending on presence/absence of pruritus. Different from PFIC patients, ATX antigen levels were not significantly elevated in ASC patients with (median: 665.8 ng/ml, IQR: 357.8-1,203) and without pruritus (median: 391.0 ng/ml, IQR: 283.2-485.6). In ASC patients, tBA, tMCA, and ATX antigen levels did not correlate with pruritus severity. Conclusion: Despite the same underlying disease, pediatric ASC patients with pruritus exhibit significantly altered BA profiles and MCA levels compared to ASC patients without pruritus. ATX antigen levels seem to have little diagnostic or prognostic meaning in ASC patients. An increased ATX activity alone seems not to be causal for pruritus genesis in ASC patients. Clinical Trial Registration: [www.drks.de], identifier [DRKS00026913].

Bile acid-induced tissue factor activity in hepatocytes correlates with activation of farnesoid X receptor.

Bile acids (BA) have been found to promote coagulation by increasing tissue factor (TF) activity. The contribution of elevated BA levels and cholestasis to TF decryption within the liver parenchyma and the role of farnesoid X receptor (FXR) in this process remain unclear. We investigated the effects of BA on TF activity and thrombin generation in hepatocytes and correlated these effects with activation of FXR-dependent signaling and apoptosis. HepG2 cells and primary hepatocytes were incubated with chenodeoxycholic acid (CDCA), glycochenodeoxycholic acid (GCDCA), ursodeoxycholic acid (UCDA), or the synthetic FXR agonist GW4064 for 24 h. MTT tests demonstrated cell viability throughout experiments. TF activity was tested via factor Xa generation and thrombin generation was measured by calibrated automated thrombography. Increased TF activity alongside enhanced thrombin generation was observed with CDCA and GW4064 but not with GCDCA and UDCA. TF activity was substantially reduced when FXR activation was blocked with the antagonist DY 268. Quantitative polymerase chain reaction revealed upregulation of FXR target genes only by CDCA and GW4064. Western blot analysis and fluorescence microscopy showed no TF overexpression arguing for TF decryption. Caspase 3 activity measurements and flow cytometric analysis of Annexin V binding showed no signs of apoptosis. Long-term exposure of hepatocytes to nontoxic BA may cause intracellular FXR overstimulation, triggering TF decryption irrespective of the amphiphilic properties of BA. The effect of BA on TF activation correlates with the molecule's ability to enter the cells and activate FXR. TF decryption occurs independently of apoptotic mechanisms.

Cell Surface Glycoprotein CD24 Marks Bone Marrow-Derived Human Mesenchymal Stem/Stromal Cells with Reduced Proliferative and Differentiation Capacity In Vitro.

Bone marrow-derived mesenchymal stem/stromal cells (BMSCs) are fundamental to bone regenerative therapies, tissue engineering, and postmenopausal osteoporosis. Donor variation among patients, cell heterogeneity, and unpredictable capacity for differentiation reduce effectiveness of BMSCs for regenerative cell therapies. The cell surface glycoprotein CD24 exhibits the most prominent differential expression during osteogenic versus adipogenic differentiation of human BMSCs. Therefore, CD24 may represent a selective biomarker for subpopulations of BMSCs with increased osteoblastic potential. In undifferentiated human BMSCs, CD24 cell surface expression is variable among donors (range: 2%-10%) and increased by two to fourfold upon osteogenic differentiation. Strikingly, FACS sorted CD24pos cells exhibit delayed mineralization and reduced capacity for adipocyte differentiation. RNAseq analysis of CD24pos and CD24neg BMSCs identified a limited number of genes with increased expression in CD24pos cells that are associated with cell adhesion, motility, and extracellular matrix. Downregulated genes are associated with cell cycle regulation, and biological assays revealed that CD24pos cells have reduced proliferation. Hence, expression of the cell surface glycoprotein CD24 identifies a subpopulation of human BMSCs with reduced capacity for proliferation and extracellular matrix mineralization. Functional specialization among BMSCs populations may support their regenerative potential and therapeutic success by accommodating cell activities that promote skeletal tissue formation, homeostasis, and repair.

Cytokine treatment optimises the immunotherapeutic effects of umbilical cord-derived MSC for treatment of inflammatory liver disease.

BACKGROUND: Mesenchymal stromal cells (MSC) possess immunomodulatory properties and low immunogenicity, both crucial properties for their development into an effective cellular immunotherapy. They have shown benefit in clinical trials targeting liver diseases; however the efficacy of MSC therapy will benefit from improvement of the immunomodulatory and immunogenic properties of MSC. METHODS: MSC derived from human umbilical cords (ucMSC) were treated for 3 days in vitro with various inflammatory factors, interleukins, vitamins and serum deprivation. Their immunogenicity and immunomodulatory capacity were examined by gene-expression analysis, surface-marker expressions, IDO activity, PGE2 secretion and inhibition of T cell proliferation and IFNγ production. Furthermore, their activation of NK cell cytotoxicity was investigated via CD107a expression on NK cells. The immunomodulatory capacity, biodistribution and survival of pre-treated ucMSC were investigated in a CCl4-induced liver disease mouse model. In addition, capacity of pre-treated MSC to ameliorate liver inflammation was examined in an ex vivo liver inflammation co-culture model. RESULTS: IFN-γ and a multiple cytokine cocktail (MC) consisting of IFN-γ, TGFß and retinoic acid upregulated the expression of immunomodulatory factor PD-L1 and IDO activity. Subsequently, both treatments enhanced the capacity of ucMSC to inhibit CD4 and CD8 T cell proliferation and IFN-γ production. The susceptibility of ucMSC for NK cell lysis was decreased by IFN-ß, TGFß and MC treatment. In vivo, no immunomodulation was observed by the ucMSC. Four hours after intravenous infusion in mice with CCl4-induced inflammatory liver injury, the majority of ucMSC were trapped in the lungs. Rapid clearance of ucMSC(VitB6), ucMSC(Starv + VitB6) and ucMSC(MC) and altered bio-distribution of ucMSC(TGFß) compared to untreated ucMSC was observed. In the ex vivo co-culture system with inflammatory liver slices ucMSC(MC) showed significantly enhanced modulatory capacity compared to untreated ucMSC. CONCLUSIONS: The present study demonstrates the responsiveness of ucMSC to in vitro optimisation treatment. The observed improvements in immunomodulatory capacity as well as immunogenicity after MC treatment may improve the efficacy of ucMSC as immunotherapy targeted towards liver inflammation.

Aging of bone marrow- and umbilical cord-derived mesenchymal stromal cells during expansion.

BACKGROUND AIMS: Mesenchymal stromal cells (MSCs) are used as experimental immunotherapy. Extensive culture expansion is necessary to obtain clinically relevant cell numbers, although the impact on MSCs stability and function is unclear. This study investigated the effects of long-term in vitro expansion on the stability and function of MSCs. METHODS: Human bone marrow-derived (bmMSCs) and umbilical cord-derived (ucMSCs) MSCs were in vitro expanded. During expansion, their proliferative capacity was examined. At passages 4, 8 and 12, analyses were performed to investigate the ploidy, metabolic stability, telomere length and immunophenotype. In addition, their potential to suppress lymphocyte proliferation and susceptibility to natural killer cell lysis was examined. RESULTS: BmMSCs and ucMSCs showed decreasing proliferative capacity over time, while their telomere lengths and mitochondrial activity remained stable. Percentage of aneuploidy in cultures was unchanged after expansion. Furthermore, expression of MSC markers and markers associated with stress or aging remained unchanged. Reduced capacity to suppress CD4 and CD8 T-cell proliferation was observed for passage 8 and 12 bmMSCs and ucMSCs. Finally, susceptibility of bmMSCs and ucMSCs to NK-cell lysis remained stable. CONCLUSIONS: We showed that after long-term expansion, phenotype of bmMSCs and ucMSCs remains stable and cells exhibit similar immunogenic properties compared with lower passage cells. However, immunosuppressive properties of MSCs are reduced. These findings reveal the consequences of application of higher passage MSCs in the clinic, which will help increase the yield of therapeutic MSCs but may interfere with their efficacy.

Identification of Three Early Phases of Cell-Fate Determination during Osteogenic and Adipogenic Differentiation by Transcription Factor Dynamics.

Age-related skeletal degeneration in patients with osteoporosis is characterized by decreased bone mass and occurs concomitant with an increase in bone marrow adipocytes. Using microarray expression profiling with high temporal resolution, we identified gene regulatory events in early stages of osteogenic and adipogenic lineage commitment of human mesenchymal stromal cells (hMSCs). Data analysis revealed three distinct phases when cells adopt a committed expression phenotype: initiation of differentiation (0-3 hr, phase I), lineage acquisition (6-24 hr, phase II), and early lineage progression (48-96 hr, phase III). Upstream regulator analysis identified 34 transcription factors (TFs) in phase I with a role in hMSC differentiation. Interestingly, expression levels of identified TFs did not always change and indicate additional post-transcriptional regulatory mechanisms. Functional analysis revealed that forced expression of IRF2 enhances osteogenic differentiation. Thus, IRF2 and other early-responder TFs may control osteogenic cell fate of MSCs and should be considered in mechanistic models that clarify bone-anabolic changes during clinical progression of osteoporosis.

Inactivated Mesenchymal Stem Cells Maintain Immunomodulatory Capacity.

Mesenchymal stem cells (MSC) are studied as a cell therapeutic agent for treatment of various immune diseases. However, therapy with living culture-expanded cells comes with safety concerns. Furthermore, development of effective MSC immunotherapy is hampered by lack of knowledge of the mechanisms of action and the therapeutic components of MSC. Such knowledge allows better identification of diseases that are responsive to MSC treatment, optimization of the MSC product, and development of therapy based on functional components of MSC. To close in on the components that carry the therapeutic immunomodulatory activity of MSC, we generated MSC that were unable to respond to inflammatory signals or secrete immunomodulatory factors, but preserved their cellular integrity [heat-inactivated MSC (HI-MSC)]. Secretome-deficient HI-MSC and control MSC showed the same biodistribution and persistence after infusion in mice with ischemic kidney injury. Both control and HI-MSC induced mild inflammatory responses in healthy mice and dramatic increases in interleukin-10, and reductions in interferon gamma levels in sepsis mice. In vitro experiments showed that opposite to control MSC, HI-MSC lacked the capability to suppress T-cell proliferation or induce regulatory B-cell formation. However, both HI-MSC and control MSC modulated monocyte function in response to lipopolysaccharides. The results of this study demonstrate that, in particular disease models, the immunomodulatory effect of MSC does not depend on their secretome or active cross-talk with immune cells, but on recognition of MSC by monocytic cells. These findings provide a new view on MSC-induced immunomodulation and help identify key components of the therapeutic effects of MSC.

Effects of Freeze-Thawing and Intravenous Infusion on Mesenchymal Stromal Cell Gene Expression.

Mesenchymal stromal cells (MSC) are increasingly used as an investigative therapeutic product for immune disorders and degenerative disease. Typically, MSC are isolated from human tissue, expanded in culture, and cryopreserved until usage. The safety and efficacy of MSC therapy will depend on the phenotypical and functional characteristics of MSC. The freeze-thawing procedure may change these characteristics. Furthermore, the cells encounter a microenvironment after administration that may impact their properties. It has been demonstrated that the majority of MSC localize to the lungs after intravenous infusion, making this the site to study the effects of the in vivo milieu on administered MSC. In this study, we investigated the effect of freeze-thawing and the mouse lung microenvironment on human adipose tissue-derived MSC. There were effects of freeze-thawing on the whole genome expression profile of MSC, although the effects did not exceed interdonor differences. There were no major changes in the expression of hemostatic regulators on transcriptional level, but significantly increased expression of procoagulant tissue factor on the surface of thawed adipose MSC, correlating with increased procoagulant activity of thawed cells. Exposure for 2 h to the lung microenvironment had a major effect on MSC gene expression and affected several immunological pathways. This indicates that MSC undergo functional changes shortly after infusion and this may influence the efficacy of MSC to modulate inflammatory responses. The results of this study demonstrate that MSC rapidly alter in response to the local milieu and disease-specific conditions may shape MSC after administration.