Platelet-Derived Extracellular Vesicles for Regenerative Medicine

Extracellular vesicles (EVs) present a great potential for the development of new treatments in the biomedical field. To be used as therapeutics, many different sources have been used for EVs obtention, while only a few studies have addressed the use of platelet-derived EVs (pEVs). In fact, pEVs have been shown to intervene in different healing responses, thus some studies have evaluated their regenerative capability in wound healing or hemorrhagic shock. Even more, pEVs have proven to induce cellular differentiation, enhancing musculoskeletal or neural regeneration. However, the obtention and characterization of pEVs is widely heterogeneous and differs from the recommendations of the International Society for Extracellular Vesicles. Therefore, in this review, we aim to present the main advances in the therapeutical use of pEVs in the regenerative medicine field while highlighting the isolation and characterization steps followed. The main goal of this review is to portray the studies performed in order to enhance the translation of the pEVs research into feasible therapeutical applications.     

Coagulation cascade

The coagulation cascade is now recognized to be a series of proteolytic events mainly localized to the surface of activated platelets. Once platelets become activated by exposure to activated endothelium, they release mediators such as P-selectin and von Willebrand factor that promote microvesicle formation and platelet adherence. The microvesicles fuse with the activated platelet membrane, providing tissue factor and its ligand, factor VIIa. Clotting factors bind to adjacent receptors on the membrane, enabling the cascading proteolytic cleavages of zymogens to active enzymes, culminating in thrombin generation. Fibrin formation thus occurs in the sheltered environment of the platelet membrane, where it is localized to the site of injury and protected from circulating inhibitors.     

Si thin platelets as high-capacity negative electrode for Li-ion batteries

Pure Si platelets and Ni or Cu layer-laminated Si platelets with difference thickness were prepared, and their charge/discharge properties were examined in 1 M LiClO₄/EC + DEC (1:1 by volume) as alternative negative electrode materials to graphite for Li-ion batteries. The shape of thin platelets and lamination with Ni layer are significantly effective to improve the cycleability in Li-Si alloy system by relieving the stress during the alloying/de-alloying processes, reinforcing the mechanical strength and reducing the Li⁺ ion diffusion length. Moreover, the first irreversible capacity is minimized by reduction of the amount of Ketjen Black (KB) in the composite electrode because of electrolyte decomposition on the surface of KB. Consequently, the Si/Ni/Si-LP30 (30/30/30 nm) composite electrode with 5 wt% KB also exhibits over 700 mAh g⁻¹ even after 50 cycles in 1 M LiPF₆/EC + DEC (1:1).     

Formation of TiC hexagonal platelets and their growth mechanism

A large amount of TiC hexagonal platelets has formed on the surface of the sample made of Ti/Si/TiC/Al_0.2 after sintering at above 1450 °C in an Ar atmosphere. The basal plane of TiC platelets is (111) facet confirmed by X-ray diffraction. Small amounts of Si and Al elements dissolved in the TiC crystal structure, influencing the structure of TiC. The detailed structure and growth mechanism of the TiC platelets have been observed and analyzed. A model has been proposed to understand the formation of TiC hexagonal platelets.     

羟基红花黄色素A注射剂、阿司匹林及波立维对家兔血小板聚集及超微结构的影响

目的：观察羟基红花黄色素A（HSYA）注射剂、阿司匹林和波立维对家兔血小板聚集功能及超微结构的影响。方法：采用体内实验法,观察羟基红花黄色素A注射剂、阿司匹林和波立维对由花生四烯酸（从）、二磷酸腺苷（ADP）和血小板活化因子（PAF）诱导的家兔血小板聚集作用的影响,以及血小板超微结构的变化。结果：羟基红花黄色素A注射剂能抑制AA、PAF诱导的家兔血小板聚集;扫描电镜显示：羟基红花黄色素A注射剂能减少AA和PAF诱导后的聚集型血小板数量并使树突型血小板突起变少变短。结论：羟基红花黄色素A注射剂具有抗PAF诱导的血小板聚集作用,抑制血小板的活化,从而为临床抗血小板聚集药物的使用提供更多选择。     

凝血纤溶系统失衡与特发性肺间质纤维化发病机制及治疗的研究进展

特发性肺间质纤维化（IPF）是一种进行性间质性肺疾病,其预后比许多癌症都要差,发病机制复杂并且尚未明确。在肺纤维化的动物模型以及IPF的患者中,已证实均存在凝血系统以及纤溶系统的失衡。本文阐述了凝血纤溶系统失衡在IPF中的可能损伤机制,为IPF的治疗提供新思路。     

Proprotein Convertase Subtilisin Kexin Type 9 Inhibitors Reduce Platelet Activation Modulating ox-LDL Pathways

Background: Proprotein convertase subtilisin kexin type 9 inhibitors (PCSK9i) lower LDL-cholesterol and slow atherosclerosis preventing cardiovascular events. While it is known that circulating PCSK9 enhances platelet activation (PA) and that PCSK9i reduce it, the underlying mechanism is not still clarified. Methods: In a multicenter before–after study in 80 heterozygous familial hypercholesterolemia (HeFH) patients on treatment with maximum tolerated statin dose ± ezetimibe, PA, soluble-NOX2-derived peptide (sNOX2-dp), and oxidized-LDL (ox-LDL) were measured before and after six months of PCSK9i treatment. In vitro study investigates the effects of plasma from HeFH patients before and after PCK9i on PA in washed platelets (wPLTs) from healthy subjects. Results: Compared to baseline, PCSK9i reduced the serum levels of LDL-c, ox-LDL, Thromboxane (Tx) B2, sNOX2-dp, and PCSK9 (p < 0.001). The decrease of TxB2 correlates with that of ox-LDL, while ox-LDL reduction correlated with PCSK9 and sNOX2-dp delta. In vitro study demonstrated that wPLTs resuspended in plasma from HeFH after PCSK9i treatment induced lower PA and sNOX2-dp release than those obtained using plasma before PCSK9i treatment. This reduction was vanished by adding ox-LDL. ox-LDL-induced PA was blunted by CD36, LOX1, and NOX2 inhibition. Conclusions: PCSK9i treatment reduces PA modulating NOX2 activity and in turn ox-LDL formation in HeFH patients.     

Enhancing the performance of dye-sensitized solar cells by incorporating nanosilicate platelets in gel electrolyte

Two kinds of gel-type dye-sensitized solar cells (DSSCs), composed of two types of electrolytes, were constructed and the respective cell performance was evaluated in this study. One electrolyte, TEOS-Triton X-100 gel, was based on a hybrid organic/inorganic gel electrolyte made by the sol–gel method and the other was based on poly(vinyidene fluoride-co-hexafluoro propylene) (PVDF-HFP) copolymer. TEOS-Triton X-100 gel was based on the reticulate structure of silica, formed by hydrolysis, and condensation of tetraethoxysilane (TEOS), while its organic subphase was a mixture of surfactant (Triton X-100) and ionic liquid electrolytes. Both DSSC gel-type electrolytes were composed of iodine, 1-propy-3-methyl-imidazolium iodide, and 3-methoxypropionitrile to create the redox couple of I₃⁻/I⁻. Based on the results obtained from the I–V characteristics, it was found that the optimal iodine concentrations for the TEOS-Triton X-100 gel electrolyte and PVDF-HFP gel electrolyte are 0.05 M and 0.1 M, respectively. Although the increase in the iodine concentration could enhance the short-circuit current density (J_SC), a further increase in the iodine concentration would reduce the J_SC due to increased dark current. Therefore, the concentration of I₂ is a significant factor in determining the performance of DSSCs.In order to enhance cell performance, the addition of nanosilicate platelets (NSPs) in the above-mentioned gel electrolytes was investigated. By incorporating NSP-Triton X-100 into the electrolytes, the J_SC of the cells increased due to the decrease of diffusion resistance, while the open circuit voltage (V_OC) remained almost the same. As the loading of the NSP-Triton X-100 in the TEOS-Triton X-100 gel electrolyte increased to 0.5 wt%, the J_SC and the conversion efficiency increased from 8.5 to 12 mA/cm² and from 3.6% to 4.7%, respectively. However, the J_SC decreased as the loading of NSP-Triton X-100 exceeded 0.5 wt%. At higher NSP-Triton X-100 loading, NSPs acted as a barrier interface between the electrolyte and the dye molecules, hindering electron transfer, hence, reducing the cell's photocurrent density. The same behavior was also observed in the PVDF-HFP gel electrolyte DSSC system.     

阿魏酸乙酯的药理活性及其机制研究

目的: 观察阿魏酸乙酯的药理活性及其机制。方法: 在兔富含血小板血浆(PRP)中加入阿魏酸乙酯和阿魏酸,用ADP诱导血小板的集聚,用TYXN-91 智能血液凝集仪观察血小板聚集率,激光共聚焦显微镜观察血小板细胞聚集时细胞内钙离子的变化情况。制备CCl4 肝损伤小鼠模型,取血清测定谷丙转氨酶(ALT)、谷草转氨酶(AST)活性,取肝组织测定丙二醛(MDA)水平及超氧化物歧化酶(SOD)活性。结果: 不同浓度的阿魏酸乙酯,对ADP诱导的血小板聚集抑制百分数均显著高于等浓度的阿魏酸(n=8,P<0.05)。在阿魏酸乙酯作用下ADP诱导的血小板细胞内钙离子荧光强度的变化(ΔFI)为4.6 ±1.7,明显低于对照组ΔFI 值(10.3 ±2.6,n=8,P<0.01)。阿魏酸乙酯可使肝损伤小鼠组织MDA、血清ALT、AST 含量显著低于对照组,而肝组织的SOD 水平显著高于对照组。结论: 阿魏酸乙酯抑制ADP诱导的血小板聚集作用及对CCl4 引起的小鼠急性肝损伤的保护作用均比阿魏酸强。     

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.