Platelets play a key role in the pathogenesis of atherothrombosis, and also perform the physiological hemostasis. The platelet function assays have values in the investigating patients with suspected platelet disorders and in studying the effects of anti-platelet drugs. There are increasing assays for investigating platelet function, including assessment of platelet adhesion, activation and aggregation, etc. However, all of these assays have certain limited sensitivity. It is necessary to develop a simple, sensitive assay that measures the activated platelet. This article reviewed advances of researches on platelet function assays, including assay for general function of platelet, assay of platelet adhesion function, platelet activation assay, platelet aggregation assay, platelet coagulation assay and application of flow cytometry in assessment of platelet functions, etc. and looked forward to research prospect in this field.
Blood Platelets ; physiology ; Humans ; Platelet Activation ; physiology ; Platelet Adhesiveness ; physiology ; Platelet Aggregation ; physiology ; Platelet Function Tests ; methods ; trends

OBJECTIVE: To study the effect of gradient shear stress on platelet aggregation by microfluidic chip Technology. METHODS: Microfluidic chip was used to simulate 80% fixed stenotic microchannel, and the hydrodynamic behavior of the stenotic microchannel model was analyzed by the finite element analysis module of sollidwork software. Microfluidic chip was used to analyze the adhesion and aggregation behavior of platelets in patients with different diseases, and flow cytometry was used to detect expression of the platelet activation marker CD62p. Aspirin, Tirofiban and protocatechuic acid were used to treat the blood, and the adhesion and aggregation of platelets were observed by fluorescence microscope. RESULTS: The gradient fluid shear rate produced by the stenosis model of microfluidic chip could induce platelet aggregation, and the degree of platelet adhesion and aggregation increased with the increase of shear rate within a certain range of shear rate. The effect of platelet aggregation in patients with arterial thrombotic diseases were significantly higher than normal group (P<0.05), and the effect of platelet aggregation in patients with myelodysplastic disease was lower than normal group (P<0.05). CONCLUSION The microfluidic chip analysis technology can accurately analyze and evaluate the platelet adhesion and aggregation effects of various thrombotic diseases unde the environment of the shear rate, and is helpful for auxiliary diagnosis of clinical thrombotic diseases.
Humans ; Microfluidics ; Platelet Adhesiveness ; Platelet Aggregation ; Blood Platelets/metabolism* ; Platelet Aggregation Inhibitors/pharmacology* ; Platelet Activation/physiology* ; Thrombosis

Platelet clearance has already been studied in physiological and pathological conditions and shown its occurrence mainly in the liver and the spleen. It is still not clear what mechanisms are responsible for recognition and removal of either aged or damaged platelets by the scavenging system. So study of the clearance mechanism will be useful to prolong the survival time of platelets in vivo. And it may be related to a new strategy to store platelets. This article focuses on the advances in studies of the clearance mechanism of transfused platelet concentrates, including roles of P-selectin, GPI balpha and its receptor Mac-1 in platelet clearance, and effect of endogenous metalloproteinase in platelet clearance.
Blood Platelets ; physiology ; Blood Preservation ; Cellular Senescence ; Humans ; Macrophage-1 Antigen ; physiology ; Metalloproteases ; physiology ; P-Selectin ; physiology ; Platelet Activation ; Platelet Glycoprotein GPIb-IX Complex ; physiology ; Platelet Transfusion

OBJECTIVETo investigate the relationship between platelet parameters and delayed graft function (DGF) early after kidney transplantation.

METHODSWe retrospectively analyzed the clinical data of 232 recipients within 2 months following kidney transplantation performed between January, 2009 and September, 2013, among whom 29 experienced DGF. The laboratory data of the preoperative and postoperative platelets were collected from all the recipients.

RESULTSCompared with the preoperative levels, the platelet number (PLT) and platelet hematocrit (PCT) were decreased on day 1 after kidney transplantation and was the lowest on day 5 (P<0.05), followed by gradual increase till reaching the highest levels on day 15 (P<0.05) and recovery of the preoperative level in days 30-60. The average platelet volume (MPV), platelet volume distribution width (PDW) and large platelet ratio (P-LCR) were increased on day 1, highest on day 7 (P<0.05), and reduced to the preoperative level on day 15, but then rose again slowly. MPV and P-LCR in days 30 to 60 and PDW in days 45 to 60 were significantly higher than the preoperative levels (P<0.05). The patients with DGF showed lowered PLT than those without DGF since day 2, and this difference was statistically significant in days 7 to 10, while PCT remained comparable between the two groups; MPV, PDW, and P-LCR were higher in DGF group than in DGF-free group with statistically significant difference on days 7, 10, and 15 (P<0.05).

CONCLUSIONPlatelet function is associated with postoperative renal graft function recovery, and platelet parameters can provide new markers for monitoring the occurrence and reversion of DGF.

Biomarkers ; Blood Platelets ; physiology ; Delayed Graft Function ; Humans ; Kidney Transplantation ; Platelet Activation ; Platelet Count ; Postoperative Period ; Retrospective Studies

OBJECTIVETo assess the effects of hormone replacement therapy (HRT) on platelet activation in postmenopausal women compared with premenopausal women.

METHODSThe expressions of CD41 and CD62P in fifteen postmenopausal women before and after HRT were detected using flow cytometry (FCM), with fifteen premenopausal women with a mean age of 47 years as controls.

RESULTSThe expressions of CD41 and CD62P in postmenopausal women were higher than those in the control group. CD62P(%), CD62P(I) and CD41 were reduced from 36.40 +/- 5.9, 37.75 +/- 5.8, and 470.11 +/- 74.0 to 27.97 +/- 5.6, 26.64 +/- 4.9, and 303.23 +/- 72.8 after six months of HRT (P < 0.05).

CONCLUSIONSPlatelet activation in postmenopausal women was higher than in premenopausal women and was reduced significantly after six months of HRT. HRT may have a favorable effect on reduction of platelet activity.

Adult ; Female ; Hormone Replacement Therapy ; Humans ; Middle Aged ; Platelet Activation ; drug effects ; Postmenopause ; physiology

Atherosclerosis ; complications ; pathology ; Blood Platelets ; physiology ; Humans ; Platelet Activation ; Thrombosis ; etiology ; pathology

This study was designed to compare the effects of protease-activated receptor 1 (PAR-1) and protease-activated receptor 4 (PAR-4) to the expression of platelet surface GPIbalpha and cytoskeleton reorganization, then to investigate the role of PARs in platelet signal transmission. PAR1 (25 micromol/L) and PAR4 (250 micromol/L) were used to stimulate platelet at different time points (0 - 60 minutes), and the platelet surface GPIbalpha, actin and myosin and P-selectin were detected with flow cytometry, the alteration of GPIbalpha, actin and myosin in cytoskeleton was compared by Western blot, the membrane cytoskeleton followed GPIbalpha immunoprecipitation was analyzed. The results showed that an increase of P-selectin and reversible decrease of GPIbalpha expression were obtained after platelet activation by PAR1 o r PAR4, and a different kinetics of redistribution of GPIbalpha was found for the two peptides all over the time course (P < 0.05). PAR1 acted more potently and rapidly than PAR4, but the effect of PAR4 persisted longer in the course of platelet activation. Meanwhile, there was a transient change of actin, myosin and GPIbalpha in cytoskeleton proteins. Similar redistribution was also found in GPIbalpha/myosin and GPIbalpha/actin association. It is concluded that PAR1 and PAR4 possess an important role in platelet signal transmission. Either of the receptors can mediate platelet activation and GPIbalpha redistribution, which is correlated with cytoskeleton reorganization. PAR1 acts more rapidly, and effect of PAR4 persists longer.
Cytoskeleton ; chemistry ; Flow Cytometry ; Humans ; Myosins ; analysis ; P-Selectin ; analysis ; Platelet Activation ; Platelet Glycoprotein GPIb-IX Complex ; Receptor, PAR-1 ; physiology ; Receptors, Thrombin ; physiology

OBJECTIVETo explore whether normal platelet contains tissue factor (TF), and the significance of platelet-associated TF (PATF).

METHODSPlatelets were isolated by Sepharose 2B gel column. ELISA was used to detect the TF content in the lysates of washed platelets. Procoagulant activity of PATF was measured by one stage clotting time assay. The mRNA of TF was detected by reverse transcription polymerase chain reaction (RT-PCR).

RESULTSA certain amount of TF antigen (16.37 +/- 6.39) ng/L was detected in the washed-platelet lysates. Upon activation by collagen, platelets released TF and caused a marked increase in TF level in plasma (P <0.05). Resting platelets had no TF procoagulant activity, while procoagulant activity of platelets activated by collagen increased significantly, which could be blocked by TF McAb and poor VII plasma. TF mRNA could not be detected in washed platelets. TF content in platelets from patients with coronary heart disease was significantly higher than that from normal controls (P < 0.05). Resting platelets from the patients showed a higher procoagulant activity, which could be inhibited by TF McAb.

CONCLUSIONPlatelets contain TF and the latter released by activated platelet was functionally active. Platelet itself might not synthesize TF. Protein content and procoagulant activity of PATF in patients with coronary heart disease were higher than that in controls. All these indicate that platelet may be involved in coagulation and thrombosis by releasing TF.

Adolescent ; Adult ; Blood Platelets ; chemistry ; Coronary Artery Disease ; metabolism ; physiopathology ; Female ; Humans ; Male ; Middle Aged ; Platelet Activation ; Thromboplastin ; metabolism ; physiology

Platelets, small pieces of cytoplasm with biological activity, split and fall off the megakaryocytes and mature from the bone marrow. After stimulated, platelets produce nitric oxide to inhibit their own activation and aggregation. Pathologically, the injury of endothelial cells activates platelets and changes their functions. The release of inflammatory mediators and cytokines induces and enhances the development and progression of atherosclerosis, and thereby promotes the occurrence of erectile dysfunction. Besides, platelets and their related functional parameters may serve as important indicators in the diagnosis and treatment of erectile dysfunction.
Atherosclerosis ; etiology ; Blood Platelets ; physiology ; Cytokines ; metabolism ; Endothelial Cells ; Erectile Dysfunction ; etiology ; Humans ; Male ; Nitric Oxide ; biosynthesis ; Platelet Activation

OBJECTIVE: To explore the regulation of mitochondria on platelet apoptosis and activation, and the relationship between platelet apoptosis and activation. METHODS: Platelets were isolated from peripheral venous blood of healthy volunteers. Cyclosporin A (CsA), which has a protective effect on the function of platelet mitochondria, BAPTA, which can chelate calcium ions across membranes in platelets, and NAC, an antioxidant that reduces the level of intracellular reactive oxygen species, were selected for coincubation with washed platelets, respectively. By flow cytometry, platelet aggregator was used to detect the changes of platelet mitochondrial function and platelet activation indexes after different interventions. RESULTS: H89, staurosporine, and A23187 led to platelet mitochondrial abnormalities, while CsA could effectively reverse the decline of platelet mitochondrial membrane potential caused by them. Antioxidant NAC could reverse platelet mitochondrial damage correspondingly, and completely reverse platelet shrinkage and phosphatidylserine eversion induced by H89. BAPTA, prostaglandin E1, acetylsalicylic acid and other inhibitors could not reverse the decline of platelet mitochondrial membrane potential. CONCLUSION Mitochondrial function plays an important role in platelet apoptosis and activation. Abnormal mitochondrial function causes the imbalance of reduction/oxidation state in platelets, which leads to platelet apoptosis. Platelet apoptosis and activation are independent signal processes.
Humans ; Blood Platelets/metabolism* ; Antioxidants/pharmacology* ; Mitochondria/physiology* ; Platelet Activation ; Apoptosis ; Membrane Potential, Mitochondrial ; Reactive Oxygen Species/pharmacology*