Introduction

Antiplatelet therapy for neonates and infants is often extrapolated from the adult experience, based on limited observation of agonist-induced neonatal platelet hypoactivity and poor understanding of flow shear-mediated platelet activation. Therefore, thrombotic events due to device-associated disturbed flow are inadequately mitigated in critically ill neonates with indwelling umbilical catheters and infants receiving cardiovascular implants.

Methods

Whole blood (WB), platelet-rich plasma (PRP), and gel-filtered platelets (GFP) were prepared from umbilical cord and adult blood, and exposed to biochemical agonists or pathological shear stress of 70 dyne/cm². We evaluated α-granule release, phosphatidylserine (PS) scrambling, and procoagulant response using P-selectin expression, Annexin V binding, and thrombin generation (PAS), respectively. Activation modulation due to depletion of intracellular and extracellular calcium, requisite second messengers, was also examined.

Results

Similar P-selectin expression was observed for sheared adult and cord platelets, with concordant inhibition due to intracellular and extracellular calcium depletion. Sheared cord platelet Annexin V binding and PAS activity was similar to adult values in GFP, but lower in PRP and WB. Annexin V on sheared cord platelets was calcium-independent, with PAS slightly reduced by intracellular calcium depletion.

Conclusions

Increased PS activity on purified sheared cord platelets suggest that their intrinsic function under pathological flow conditions is suppressed by cell-cell or plasmatic components. Although secretory functions of adult and cord platelets retain comparable calcium-dependence, PS exposure in sheared cord platelets is uniquely calcium-independent and distinct from adults. Identification of calcium-regulated developmental disparities in shear-mediated platelet function may provide novel targets for age-specific antiplatelet therapy.

中文翻译：

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剪切诱导的血小板激活对年龄和钙利用率敏感：成人血和脐带血的比较

介绍

对新生儿和婴儿的抗血小板治疗通常是根据成人经验推断的，基于对激动剂引起的新生儿血小板活性低下的有限观察以及对流剪切介导的血小板活化的了解不足。因此，在留置脐带导管的危重新生儿和接受心血管植入物的婴儿中，由于装置相关的血流紊乱而导致的血栓事件没有得到充分缓解。

方法

从脐带和成人血液中制备全血(WB)、富含血小板的血浆(PRP)和凝胶过滤的血小板(GFP)，并暴露于生化激动剂或70达因/cm 2 的病理剪切^应力。我们分别使用 P-选择素表达、膜联蛋白 V 结合和凝血酶生成 (PAS) 评估了 α 颗粒释放、磷脂酰丝氨酸 (PS) 扰乱和促凝血反应。还检查了由于细胞内和细胞外钙（必需的第二信使）消耗而引起的激活调节。

结果

在剪切的成人血小板和脐带血小板中观察到类似的 P-选择素表达，由于细胞内和细胞外钙消耗而具有一致的抑制作用。剪切脐带血小板膜联蛋白 V 结合和 PAS 活性与 GFP 中的成人值相似，但 PRP 和 WB 中较低。剪切脐带血小板上的膜联蛋白 V 不依赖于钙，PAS 会因细胞内钙消耗而略有降低。

结论

纯化的剪切索血小板上 PS 活性的增加表明它们在病理流动条件下的内在功能受到细胞-细胞或血浆成分的抑制。尽管成人和脐带血小板的分泌功能保留了相当的钙依赖性，但剪切脐带血小板中的 PS 暴露是独特的钙独立性，并且与成人不同。鉴定剪切介导的血小板功能中钙调节的发育差异可能为年龄特异性抗血小板治疗提供新的靶标。