The functional role of platelets in the regulation of angiogenesis

Platelet-derived sphingosine-1-phosphate and inflammation: from basic mechanisms to clinical implications

Beyond key functions in hemostasis and thrombosis, platelets are recognized as key players of inflammation, an underlying feature of a variety of diseases. In this regard, platelets act as a circulating source of several pro- and anti-inflammatory molecules, which are secreted from their intracellular stores upon activation. Among them, mounting evidence highlights a crucial role of sphingosine-1-phosphate (S1P), a multifunctional sphingoid mediator. S1P-induced pleiotropic effects include those crucial in inflammatory processes, such as the maintenance of the endothelial barrier integrity, and leukocyte activation and recruitment at the injured site. This review outlines the peculiar features and molecular mechanisms that allow platelets for acting as a unique factory that produces and stores S1P in large quantities. A particular emphasis is placed on the autocrine and paracrine roles of S1P derived from the "inflamed" platelets, highlighting the role of its cross-talk with endothelial and blood cells involved in inflammation, and the mechanisms of its contribution to the development and progression of inflammatory diseases. Finally, potential clinical implications of platelet-derived S1P as diagnostic tool of inflammatory severity, and as therapeutic target in inflammation are discussed.

Possible roles of platelet-derived microparticles in atherosclerosis

Platelets and platelet-derived microparticles (PMPs) play important roles in cardiovascular diseases, especially atherosclerosis. Continued research has revealed that PMPs have numerous functions in atherosclerosis, not only in thrombosis formation, but also by induction of inflammation. PMPs also induce formation of foam cells. Recent evidence strongly indicates a significant role of PMPs in atherosclerosis. Here, current research on the function of PMPs in atherosclerosis is reviewed.

Significance of platelet count and platelet-based models for hepatocellular carcinoma recurrence

AIM: To explore the effects of platelet count (PLT) and 11 platelet-based indices on postoperative recurrence of hepatocellular carcinoma (HCC).

METHODS: We retrospectively analyzed 172 HCC patients who were treated by partial hepatectomy. Preoperative data, including laboratory biochemical results, were used to calculate the 11 indices included in the analysis. We performed receiver operating characteristic curve analysis to determine the optimal cut-off values for predicting recurrence. Cumulative rates of HCC recurrence were calculated using Kaplan-Meier survival curves and differences were analyzed by log-rank tests. Multivariate analyses were performed to identify independent predictors of recurrence, early recurrence (within one year after surgery), and late recurrence in HCC. To obtain better prognostic models, PLT-based indices were analyzed separately after being expressed as binary and continuous variables. Two platelet-unrelated, validated HCC prognostic models were included in the analyses as reference indices. Additional analyses were performed after patients were stratified based on hepatitis B virus infection status, cirrhosis, and tumor size to investigate the significance of platelets in different subgroups.

RESULTS: In the study cohort, 44.2% (76/172) of patients experienced HCC recurrence, and 50.6% (87/172) died during a median follow-up time of 46 mo. PLT and five of the 11 platelet-related models were significant predisposing factors for recurrence (P < 0.05). Multivariate analysis indicated that, among the clinical parameters, presence of ascites, PLT ≥ 148 × 10⁹/L, alkaline phosphatase ≥ 116 U/L, and tumor size ≥ 5 cm were independently associated with a higher risk of HCC recurrence (P < 0.05). Independent and significant models included the aspartate aminotransferase/PLT index, fibrosis index based on the four factors, fibro-quotient, aspartate aminotransferase/PLT/γ-glutamyl transpeptidase/alpha-fetoprotein index, and the PLT/age/alkaline phosphatase/alpha-fetoprotein/aspartate aminotransferase index. There were different risk factors between early and late recurrences, and PLT and these indices were more inclined to influence late recurrence. PLT was only predictive of recurrence in non-cirrhotic HCC patients, and was not influenced by tumor size, which was a critical confounder in our study.

CONCLUSION: PLT and PLT-based noninvasive models are effective tools for predicting postoperative recurrence, especially late recurrence. Larger cohorts are needed to validate our findings.

Platelets: still a therapeutical target for haemostatic disorders

Platelets are cytoplasmatic fragments from bone marrow megakaryocytes present in blood. In this work, we review the basis of platelet mechanisms, their participation in syndromes and in arterial thrombosis, and their potential as a target for designing new antithrombotic agents. The option of new biotechnological sources is also explored.