Fluid Mechanics of Blood Clot Formation

Intravascular blood clots form in an environment in which hydrodynamic forces dominate and in which fluid-mediated transport is the primary means of moving material. The clotting system has evolved to exploit fluid dynamic mechanisms and to overcome fluid dynamic challenges to ensure that clots that preserve vascular integrity can form over the wide range of flow conditions found in the circulation. Fluid-mediated interactions between the many large deformable red blood cells and the few small rigid platelets lead to high platelet concentrations near vessel walls where platelets contribute to clotting. Receptor-ligand pairs with diverse kinetic and mechanical characteristics work synergistically to arrest rapidly flowing cells on an injured vessel. Variations in hydrodynamic stresses switch on and off the function of key clotting polymers. Protein transport to, from, and within a developing clot determines whether and how fast it grows. We review ongoing experimental and modeling research to understand these and related phenomena.[1]


Role of Blood Clot Formation on Early Edema Development After Experimental Intracerebral Hemorrhage

Background and Purpose—Blood “toxicity” is hypothesized to induce edema and brain tissue injury following intracerebral hemorrhage (ICH). Lobar ICH in pigs produces rapidly developing, marked perihematomal edema (>10% increase in water content) associated with clot-derived plasma protein accumulation. Coagulation cascade activation and, specifically, thrombin itself contribute to edema development during the first 24 hours after gray matter ICH in rats. In the present study, we sought to determine whether blood clot formation is necessary for edema development by comparing intracerebral infusions of heparinized and unheparinized blood in pig (white matter) and in rat (gray matter). We also examined heparin’s effect on thrombin-induced gray matter edema.

Methods—In pigs, we infused autologous blood (with or without heparin) into the cerebral white matter to produce lobar hematomas and froze the brains in situ at 1, 4, or 24 hours after ICH. We determined hematomal and perihematomal edema volumes on coronal sections by computer-assisted morphometry. In rats, we infused either blood or thrombin (with or without heparin) into the basal ganglia and measured water, sodium, and potassium contents at 24 hours after ICH.

Results—In pigs, unheparinized blood induced rapid (at 1 hour) and prolonged (24 hours) perihematomal edema (average volume, 1.29±0.20 mL; n=6). No perihematomal edema was present following heparinized blood infusions (n=6). In rats, unheparinized blood produced significantly greater edema than heparinized blood infusions. As with whole blood, thrombin-induced gray matter edema at 24 hours was significantly reduced by coinjection of heparin.

Conclusions—After ICH, blood clot formation is required for rapid and prolonged edema development in perihematomal white and gray matter. Thrombin also contributes to prolonged edema in gray matter.[2]


Engineering Design of Optimal Strategies for Blood Clot Dissolution

Blood clots form under hemodynamic conditions and can obstruct flow during angina, acute myocardial infarction, stroke, deep vein thrombosis, pulmonary embolism, peripheral thrombosis, or dialysis access graft thrombosis. Therapies to remove these clots through enzymatic and/or mechanical approaches require consideration of the biochemistry and structure of blood clots in conjunction with local transport phenomena. Because blood clots are porous objects exposed to local hemodynamic forces, pressure-driven interstitial permeation often controls drug penetration and the overall lysis rate of an occlusive thrombus. Reaction engineering and transport phenomena provide a framework to relate dosage of a given agent to potential outcomes. The design and testing of thrombolytic agents and the design of therapies must account for (a) the binding, catalytic, and systemic clearance properties of the therapeutic enzyme; (b) the dose and delivery regimen; (c) the biochemical and structural aspects of the thrombotic occlusion; (d) the prevailing hemodynamics and anatomical location of the thrombus; and (e) therapeutic constraints and risks of side effects. These principles also impact the design and analysis of local delivery devices.[3]


Assessment of Thrombolytic Activity of Five Bangladeshi Medicinal Plants: Potential Source for Thrombolytic Compounds

Aim: The aim of our project work was to assess the thrombolytic activity of five common Bangladeshi plant extract in different solvent. Five plants are Geodorum densiflorum (Shankhamul), Pistia stratiotes (Topa Pana), Smilax zeylanica (Kumarilata), Pandanus foetidus (Keya) & Tabernaemontana coronaria (Tagar). Plants were collected and air dried separately for three weeks. They were ground into a coarse powder. Cold extractions were performed for all plants by using different solvents.

Place and Duration of Study: Department of Pharmacy, University of Chittagong and University of Science and Technology Chittagong, November, 2013.

Methodology: Fresh blood was collected from healthy individuals ten volunteers (n=10). Blood was allowed to form clots in a pre-weighed sterile micro-centrifuge eppendorf tubes. After clot serum was removed and blood clot was weighed then blood clot was allowed to lysis by streptokinase. After lysis fluid was removed and the remaining of blood clot was again weighed along with the tube. Percentage of blood clot lysis was calculated on the basis of the weight difference. Weight difference of tubes obtained by weighing before and after clot lyses of blood. % clot lysis=(Weight after clot lysis/ Weight of clot before lysis)×100. This method was repeated for all extracts.

Result: Among the herbs studied Pandanus foetidus (C), Pandanus foetidus (PE), Smilax zeylanica (E) and Pistia stratiotes-Root (M) showed significant % of clot lysis 47.54%   41.49%, 43.35% and 35.85% respectively with reference to standard, streptokinase (70.24%).

Conclusion: These extracts lyse the blood clots In-vitro, however, we need to know In-vivo clot dissolving property. Further systemic research on these plants and may be a potential source of thrombolytic agent in future.[4]


Platelet-rich Fibrin Formation was delayed in Plastic Tubes

Introduction: Platelet-rich fibrin (PRF) is used in many regenerative treatments. Preparing PRF in glass tubes requires quick handling and generates biohazard concerns about silica contamination and glass breakage. Using plastic tubes may be an alternative to glass tubes.

Objectives: This study investigated the formation of PRF prepared in polypropylene (PP) and polystyrene (PS) tubes compared with glass tubes.

Methodology: PRF was prepared from human blood (n=20) in PP, PS, and glass tubes. The time required for PRF clot formation and retraction from the tube wall were observed. The PDGF-AB, TGF-β1 levels, and the gross/SEM appearance of the PRF clots were also evaluated. 

Results: The PRF clots in PP and PS tubes formed and retracted significantly slower compared with those in glass tubes. The PDGF-AB levels in the PRF from PP, PS, and glass tubes were not significantly different. Although the TGF-β1 levels in the PRF from PP and glass tubes were not different, that from the PRF from PS tubes was significantly higher. The gross structure and SEM appearance of PRF from the three tube types were similar.

Conclusion: The slow clot formation in PP and PS tubes can extend PRF handling time while retaining PDGF-AB level and fibrin appearance. Owing to this delay in clot formation, we could obtain the plasma without adding any anticoagulant chemical agents. The plasma can be used for accelerating bone regeneration as platelet-rich plasma.[5]

Reference

[1] Fogelson, A.L. and Neeves, K.B., 2015. Fluid mechanics of blood clot formation. Annual review of fluid mechanics, 47, pp.377-403.

[2] Xi, G., Wagner, K.R., Keep, R.F., Hua, Y., de Courten-Myers, G.M., Broderick, J.P., Brott, T.G. and Hoff, J.T., 1998. Role of blood clot formation on early edema development after experimental intracerebral hemorrhage. Stroke, 29(12), pp.2580-2586.

[3] Diamond, S.L., 1999. Engineering design of optimal strategies for blood clot dissolution. Annual review of biomedical engineering, 1(1), pp.427-461.

[4] Hossen, S.M., Sarkar, M.M.I. and Jahid, M.A., 2014. Assessment of thrombolytic activity of five Bangladeshi medicinal plants: Potential source for thrombolytic compounds. International Blood Research & Reviews, pp.262-269.

[5] Jianpeampoolpol, B., Phuminart, S. and Subbalekha, K., 2016. Platelet-rich fibrin formation was delayed in plastic tubes. Journal of Advances in Medicine and Medical Research, pp.1-9.