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The zymogen protease Plasminogen (Plg) and its active form plasmin (Plm) carry out important functions in the blood clot disintegration (breakdown of fibrin fibers) process. Inhibition of plasmin effectively reduces fibrinolysis to circumvent heavy bleeding. Currently, available Plm inhibitor tranexamic acid (TXA) used for treating severe hemorrhages is associated with an increased incidence of seizures which in turn were traced to gamma-aminobutyric acid antagonistic activity (GABAa) in addition to having multiple side effects. Fibrinolysis can be suppressed by targeting the three important protein domains: the kringle-2 domain of tissue plasminogen activator, the kringle-1 domain of plasminogen, and the serine protease domain of plasminogen. In the present study, one million molecules were screened from the ZINC database. These ligands were docked to their respective protein targets using Autodock Vina, Schrödinger Glide, and ParDOCK/BAPPL+. Thereafter, the drug-likeness properties of the ligands were evaluated using Discovery Studio 3.5. Subsequently, we subjected the protein-ligand complexes to molecular dynamics simulation of 200 ns in GROMACS. The identified ligands P76(ZINC09970930), C97(ZINC14888376), and U97(ZINC11839443) for each protein target are found to impart higher stability and greater compactness to the protein-ligand complexes. Principal component analysis (PCA) implicates, that the identified ligands occupy smaller phase space, form stable clusters, and provide greater rigidity to the protein-ligand complexes. Molecular Mechanics Poisson-Boltzmann Surface Area (MMPBSA) analysis reveals that P76, C97, and U97 exhibit better binding free energy (ΔG) when compared to that of the standard ligands. Thus, our findings can be useful for the development of promising anti-fibrinolytic agents.Communicated by Ramaswamy H. Sarma.

Antifibrinolytic drugs are used extensively for on-demand treatment of severe acute bleeding. Controlling fibrinolysis may also be an effective strategy to prevent or lessen chronic recurring bleeding in bleeding disorders such as hemophilia A (HA), but current antifibrinolytics have unfavorable pharmacokinetic profiles. Here, we developed a long-lasting antifibrinolytic using small interfering RNA (siRNA) targeting plasminogen packaged in clinically used lipid nanoparticles (LNPs) and tested it to determine whether reducing plasmin activity in animal models of HA could decrease bleeding frequency and severity. Treatment with the siRNA-carrying LNPs reduced circulating plasminogen and suppressed fibrinolysis in wild-type and HA mice and dogs. In HA mice, hemostatic efficacy depended on the injury model; plasminogen knockdown improved hemostasis after a saphenous vein injury but not tail vein transection injury, suggesting that saphenous vein injury is a murine bleeding model sensitive to the contribution of fibrinolysis. In dogs with HA, LNPs carrying siRNA targeting plasminogen were as effective at stabilizing clots as tranexamic acid, a clinical antifibrinolytic, and in a pilot study of two dogs with HA, the incidence of spontaneous or excess bleeding was reduced during 4 months of prolonged knockdown. Collectively, these data demonstrate that long-acting antifibrinolytic therapy can be achieved and that it provides hemostatic benefit in animal models of HA.

Hypothermia affects coagulation, but the effect of hypothermia on fibrinolysis is not clarified. Imbalance in the fibrinolytic system may lead to increased risk of bleeding or thrombosis. Our aim was to investigate if resuscitated cardiac arrest patients treated with hypothermia had an unbalanced fibrinolysis. A prospective cohort study, including 82 patients were treated with hypothermia at 33°C ± 1°C after out-of-hospital cardiac arrest. Blood samples were collected at 24 hours (hypothermia) and at 72 hours (normothermia). Samples were analyzed for fibrin D-dimer, tissue plasminogen activator (tPA), plasminogen, plasminogen activator Inhibitor-1 (PAI-1), thrombin-activatable fibrinolysis inhibitor (TAFI), and an in-house dynamic fibrin clot formation and lysis assay.Compared with normothermia, hypothermia significantly increased plasminogen activity (mean difference = 10.4%, 95% confidence interval [CI] 7.9-12.9), p  < 0.001), PAI-1 levels (mean difference = 275 ng/mL, 95% CI 203-348, p  < 0.001), and tPA levels (mean difference = 1.0 ng/mL, 95% CI 0.2-1.7, p  = 0.01). No differences between hypothermia and normothermia were found in TAFI activity ( p  = 0.59) or in the fibrin D-dimer levels ( p  = 0.08). The fibrin clot lysis curves showed three different patterns: normal-, flat-, or resistant clot lysis curve. At hypothermia 45 (55%) patients had a resistant clot lysis curve and 33 (44%) patients had a resistant clot lysis curve at normothermia ( p  = 0.047). Comatose, resuscitated, cardiac arrest patients treated with hypothermia express an inhibited fibrinolysis even after rewarming. This could potentially increase the thromboembolic risk. ClinicalTrials.gov ID: NCT02258360.

Vitreomacular traction syndrome results from persistent vitreoretinal adhesions in the setting of partial posterior vitreous detachment (PVD). Vitrectomy and reattachment of retina is an effective therapeutic approach. The adhesion between vitreous cortex and internal limiting membrane (ILM) of the retina is stronger in youth, which brings difficulties to induce PVD in vitrectomy. Several clinical investigations demonstrated that intravitreous injection of plasmin before vitrectomy could reduce the risk of detachment. In our study, a novel recombinant human microplasminogen (rhμPlg) was expressed by Pichia pastoris. Molecular docking showed that the binding of rhμPlg with tissue plasminogen activator (t-PA) was similar to plasminogen, suggesting rh μPlg could be activated by t-PA to generate microplasmin (μPlm). Moreover, rhμPlg had higher catalytic activity than plasminogen in amidolytic assays. Complete PVD was found at vitreous posterior pole of 125 μg rhμPlg-treated eyes without morphological change of retina in juvenile rabbits via intraocular injection. Our results demonstrate that rhμPlg has a potential value in the treatment of vitreoretinopathy., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Background: Fibrinolysisis is essential for vascular blood flow maintenance and is triggered by endothelial and platelet release of tissue plasminogen activator (t-PA). In certain critical conditions, e.g. sepsis, acute respiratory failure (ARF) and trauma, the fibrinolytic response is reduced and may lead to widespread thrombosis and multi-organ failure. The mechanisms underpinning fibrinolysis resistance include reduced t-PA expression and/or release, reduced t-PA and/or plasmin effect due to elevated inhibitor levels, increased consumption and/or clearance. This study in critically ill patients with fibrinolysis resistance aimed to evaluate the ability of t-PA and plasminogen supplementation to restore fibrinolysis with assessment using point-of-care ClotPro viscoelastic testing (VET)., Methods: In prospective, observational studies, whole-blood ClotPro VET evaluation was carried out in 105 critically ill patients. In 32 of 58 patients identified as fibrinolysis-resistant (clot lysis time > 300 s on the TPA-test: tissue factor activated coagulation with t-PA accelerated fibrinolysis), consecutive experimental whole-blood VET was carried out with repeat TPA-tests spiked with additional t-PA and/or plasminogen and the effect on lysis time determined. In an interventional study in a patient with ARF and fibrinolysis resistance, the impact of a 24 h intravenous low-dose alteplase infusion on coagulation and fibrinolysis was prospectively monitored using standard ClotPro VET., Results: Distinct response groups emerged in the ex vivo experimental VET, with increased fibrinolysis observed following supplementation with (i) t-PA only or (ii) plasminogen and t-PA. A baseline TPA-test lysis time of > 1000 s was associated with the latter group. In the interventional study, a gradual reduction (25%) in serial TPA-test lysis times was observed during the 24 h low-dose alteplase infusion., Conclusions: ClotPro viscoelastic testing, the associated TPA-test and the novel experimental assays may be utilised to (i) investigate the potential mechanisms of fibrinolysis resistance, (ii) guide corrective treatment and (iii) monitor in real-time the treatment effect. Such a precision medicine and personalised treatment approach to the management of fibrinolysis resistance has the potential to increase treatment benefit, while minimising adverse events in critically ill patients., Trial Registration: VETtiPAT-ARF, a clinical trial evaluating ClotPro-guided t-PA (alteplase) administration in fibrinolysis-resistant patients with ARF, is ongoing (ClinicalTrials.gov NCT05540834 ; retrospectively registered September 15th 2022)., (© 2023. The Author(s).)

Arteriovenous fistula (AVF) thrombosis occurs less often when compared to arteriovenous grafts. Since the number of AVFs has increased in the United States, AVF thrombosis is seen more frequently today. AVF thrombectomy can be tedious, requires physician ingenuity, and many times results in failure. Substantial clot burden in megafistulas and aneurysms is considered a relative contraindication to endovascular thrombectomy. Usually, it results in surgical referral for open thrombectomy or, at times, abandonment of the fistula altogether. Herein, we describe the technique, results, and cautions of combining a continuous infusion of recombinant tissue plasminogen (rTPA) followed by angioplasty of the culprit stenotic lesion that was successful in opening five of six AVFs with a substantial clot burden.

Introduction: Basic fibroblast growth factor (bFGF) plays a critical role in odontoblast differentiation and dentin matrix deposition, thereby aiding pulpo-dentin repair and regeneration., Objectives: The purpose of this study was to clarify the effects of bFGF on plasminogen activation factors, TIMP-1), ALP; and SPARC (osteonectin) expression/production of stem cells from apical papilla (SCAP) in vitro; and the involvement of MEK/ERK, p38, Akt, and TAK1 signaling., Methods: SCAP were exposed to bFGF with/without pretreatment and co-incubation with various signal transduction inhibitors (U0126, SB203580, LY294002, and 5Z-7-oxozeaenol). The expression of FGF receptors (FGFRs), PAI-1, uPA, p-ERK, p-TAK1, and p-p38 was analyzed via immunofluorescent staining. The gene expression and protein secretion of SCAP were determined via real-time PCR and ELISA. ALP activity was evaluated via ALP staining., Results: SCAP expressed FGFR1, 2, 3, and 4. bFGF stimulated the PAI-1, uPA, uPAR, and TIMP-1 mRNA expression (p < 0.05). bFGF induced PAI-1, uPA, and soluble uPAR production (p < 0.05) but suppressed the ALP activity and SPARC production (p < 0.05) of SCAP. bFGF stimulated ERK, TAK1, and p38 phosphorylation of SCAP. U0126 (a MEK/ERK inhibitor) and 5Z-7-oxozeaenol (a TAK1 inhibitor) attenuated the bFGF-induced PAI-1, uPA, uPAR, and TIMP-1 expression and production of SCAP, but SB203580 (a p38 inhibitor) did not. LY294002, SB203580, and 5Z-7oxozeaenol could not reverse the inhibition of ALP activity caused by bFGF. Interestingly, U0126 and 5Z-7-oxozeaenol prevented the bFGF-induced decline of SPARC production (p < 0.05)., Conclusion: bFGF may regulate fibrinolysis and matrix turnover via modulation of PAI-1, uPA, uPAR, and TIMP-1, but bFGF inhibited the differentiation (ALP, SPARC) of SCAP. These events are mainly regulated by MEK/ERK, p38, and TAK1. Combined use of bFGF and SCAP may facilitate pulpal/root repair and regeneration via regulation of the plasminogen activation system, migration, matrix turnover, and differentiation of SCAP., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Acknowledgments This study is supported by the Ministry of Science and Technology, Taipei, Taiwan (MOST104-2314-B-255- 010-MY3, MOST106-2314-B-002-033-MY2, MOST106-2314-B-002-034-MY2, MOST107-2314- B-255-009-MY3, MOST107-2314-B-255-008-MY2, MOST108-2314 -B-002-043-MY3, MOST110-2314-B255-002-MY3. MOST110-2314-B-255-003-MY3) and Chang Gung Memorial Hospital (CMRPF1G0101, CMRPF1G0102, CMRPF1F0071, CMRPF1H0061, CMRPF1H0062, CMRPF1H0063, CMRPF3E0022, CMRPF3E0023, NMRPF3E0041, NMRPF3E0042, NMRPF3E0043, NMRPF3H0061, NMRPF3H0062, NMRPF3H0071, NMRPF3H0072, NMRPF3H0073, NMRPF3L0031, NMRPF3L0041, CMRPF1K0071, CMRPF1K0072). The authors declare no conflict of interest regarding this manuscript., (Copyright © 2022. Production and hosting by Elsevier B.V.)

Objectives: Preeclampsia (PE) is a serious complication of pregnancy. The fibrinolytic system play crucial roles regarding placentation and evolution of PE., Aim: To study comprehensively components of the fibrinolytic system and fibrin lysability in women with PE., Design and Methods: 117 women with PE and matched controls were included. Tissue type plasminogen activator (t-PA), plasminogen, PAI-1, plasmin inhibitor (PI), D-dimer, the fibrinolytic potential of dextran sulphate euglobulin fraction (DEF), PAI-2, polymere PAI-2, fibrin clot lysability, thrombin activatable fibrinolysis inhibitor (TAFI) and fibrinogen were assessed., Results: Women with PE had significantly increased concentrations of t-PA and PAI-1, whereas the plasma concentration of PAI-2 was significantly lower compared to controls, p < 0.0001. Polymere PAI-2 was detected in both groups. DEF, TAFI and fibrinogen were not different between the groups. D-dimer was significantly increased and plasminogen/PI together with fibrin clot lysability time decreased in the PE-group, p  =  0.0004 p  =  0.04, p  =  0.03, p < 0.0001 respectively., Conclusion: This study demonstrates that PE is associated with an affected t-PA/PAI-1 system, decreased PAI-2 and increased fibrin lysability. Furthermore, PAI-2 has the potential to polymerize during pregnancy.