Hemorrhagic Transformation After Large Cerebral Infarction in Rats Pretreated With Dabigatran or Warfarin

Before, during, and after: An Argument for Safety and Improved Outcome of Thrombolysis in Acute Ischemic Stroke with Direct Oral Anticoagulant Treatment

Direct oral anticoagulants are the primary stroke prevention option in patients with atrial fibrillation. Anticoagulant use before stroke, however, might inhibit clinician comfort with thrombolysis if a stroke does occur. Resuming anticoagulants after ischemic stroke is also problematic for fear of hemorrhage. We describe extensive literature showing that thrombolysis is safe after stroke with direct anticoagulant use. Early reinstitution of direct anticoagulant treatment is associated with lower risk of embolic recurrence and lower hemorrhage risk. The use of direct anticoagulants before, during, and after thrombolysis appears to be safe and is likely to promote improved outcomes after ischemic stroke. ANN NEUROL 2024.

Predictive model for the risk of hemorrhagic transformation after rt-PA intravenous thrombolysis in patients with acute ischemic stroke: A systematic review and meta-analysis

OBJECTIVE

To systematically review the risk prediction model of Hemorrhages Transformation (HT) after intravenous thrombolysis in patients with Acute Ischemic Stroke (AIS).

METHODS

Web of Science, The Cochrane Library, PubMed, Embase, CINAHL, CNKI, CBM, WanFang, and VIP were searched from inception to February 25, 2023 for literature related to the risk prediction model for HT after thrombolysis in AIS.

RESULTS

A total of 17 included studies contained 26 prediction models, and the AUC of all models at the time of modeling ranged from 0.662 to 0.9854, 16 models had AUC>0.8, indicating that the models had good predictive performance. However, most of the included studies were at risk of bias. the results of the Meta-analysis showed that atrial fibrillation (OR=2.72, 95% CI:1.98-3.73), NIHSS score (OR=1.09, 95% CI:1.07-1.11), glucose (OR=1.12, 95% CI:1.06-1.18), moderate to severe leukoaraiosis (OR=3.47, 95% CI:1.61-7.52), hyperdense middle cerebral artery sign (OR=2.35, 95% CI:1.10-4.98), large cerebral infarction (OR=7.57, 95% CI:2.09-27.43), and early signs of infarction (OR=4.80, 95% CI:1.74-13.25) were effective predictors of HT after intravenous thrombolysis in patients with AIS.

CONCLUSIONS

The performance of the models for HT after thrombolysis in patients with AIS in the Chinese population is good, but there is some risk of bias. Future post-intravenous HT conversion prediction models for AIS patients in the Chinese population should focus on predictors such as atrial fibrillation, NIHSS score, glucose, moderate to severe leukoaraiosis, hyperdense middle cerebral artery sign, massive cerebral infarction, and early signs of infarction.

Polyphosphate-crosslinked collagen scaffolds for hemostasis and alveolar bone regeneration after tooth extraction

Post-extraction bleeding and alveolar bone resorption are the two frequently encountered complications after tooth extraction that result in poor healing and rehabilitation difficulties. The present study covalently bonded polyphosphate onto a collagen scaffold (P-CS) by crosslinking. The P-CS demonstrated improved hemostatic property in a healthy rat model and an anticoagulant-treated rat model. This improvement is attributed to the increase in hydrophilicity, increased thrombin generation, platelet activation and stimulation of the intrinsic coagulation pathway. In addition, the P-CS promoted the in-situ bone regeneration and alveolar ridge preservation in a rat alveolar bone defect model. The promotion is attributed to enhanced osteogenic differentiation of bone marrow stromal cells. Osteogenesis was improved by both polyphosphate and blood clots. Taken together, P-CS possesses favorable hemostasis and alveolar ridge preservation capability. It may be used as an effective treatment option for post-extraction bleeding and alveolar bone loss.

Statement of significance

Collagen scaffold is commonly used for the treatment of post-extraction bleeding and alveolar bone loss after tooth extraction. However, its application is hampered by insufficient hemostatic and osteoinductive property. Crosslinking polyphosphate with collagen produces a modified collagen scaffold that possesses improved hemostatic performance and augmented bone regeneration potential.

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Polyphosphate-crosslinked collagen scaffold (P-CS) showed better hemostatic effect in healthy or anticoagulant-treated rats.

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The promoted bone regeneration ability of P-CS might also be related to the clot alteration caused by polyphosphate.

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P-CS has therapeutic potential in bleeding control and alveolar ridge preservation after tooth extraction.

The Research Progress of Direct Thrombin Inhibitors

Blood coagulation is the process of changing the blood from the flowing state to the gel state. It is an important part of the hemostatic function. Coagulation is a process by which a series of coagulation factors are sequentially activated, and finally thrombin is formed to form fibrin clot. Direct thrombin inhibitors are important anticoagulant drug. These drugs can selectively bind to the active site of thrombin, inhibit thrombin activity, have strong action and high specificity, and have important significance in the clinical treatment of thrombus diseases. Some of them come from natural products of animals or plants, and many of them have been applied in the clinic. The other part is derived from the design, synthesis and activity studies of small molecule inhibitors. This review discusses the progress of direct thrombin inhibitors in recent years.

Dabigatran reduces endothelial permeability through inhibition of thrombin-induced cytoskeleton reorganization

Dabigatran etexilate (DE), a new oral anti-coagulant, is a direct thrombin inhibitor. Clinical trials showed the favorable benefit-to-risk profile of DE compared to warfarin for the prevention of ischemic stroke in patients with atrial fibrillation. Remarkably, patients treated with dabigatran showed reduced rates of intracerebral hemorrhage compared to warfarin. As the breakdown of endothelial barrier integrity is associated with hemorrhagic events and as thrombin increases endothelial permeability, we hypothesized that dabigatran preserves the endothelial barrier by inhibiting thrombin-induced permeability. We assessed leakage of fluorescein isothiocyanate (FITC)-dextran through the endothelial monolayer and measured trans-endothelial electrical resistance of the endothelial monolayer after treatment of thrombin or thrombin pre-incubated with dabigatran. Thrombin increased the permeability of endothelial cells. Dabigatran effectively blocked the ability of thrombin to increase permeability. Dabigatran inhibited the formation of actin stress fibers induced by thrombin and inhibited consequent destabilization of junctional protein complexes and intercellular gap formation. The interaction of thrombin with protease activated receptor-1 activates the Rho A guanosine triphosphate (GTP)ase-myosin light chain (MLC) phosphorylation signaling axis, leading to actin cytoskeleton changes. This signaling pathway was effectively inhibited by dabigatran in endothelial cells. Consistently, the number of phosphorylated MLC-positive cells was significantly decreased in ischemic tissue of rat brains. These results indicate dabigatran blocks the ability of thrombin to induce vascular permeability and the resulting underlying signaling cascade in endothelial cells. Our findings provide evidence that dabigatran may confer a lower risk of intracerebral hemorrhage by preserving endothelial barrier integrity.