Polymerization and adhesion, dynamic processes that are hallmarks of sickle cell disease (SCD), have thus far been studied in vitro only separately. Here, we present quantitative results of the simultaneous and synergistic effects of adhesion and polymerization of deoxygenated sickle hemoglobin (HbS) in the human red blood cell (RBC) on the mechanisms underlying vasoocclusive pain crisis. For this purpose, we employ a specially developed hypoxic microfluidic platform, which is capable of inducing sickling and unsickling of RBCs in vitro, to test blood samples from eight patients with SCD. We supplemented these experimental results with detailed molecular-level computational simulations of cytoadherence and biorheology using dissipative particle dynamics. By recourse to image analysis techniques, we characterize sickle RBC maturation stages in the following order of the degree of adhesion susceptibility under hypoxia: sickle reticulocytes in circulation (SRs) → sickle mature erythrocytes (SMEs) → irreversibly sickled cells (ISCs). We show that (i) hypoxia significantly enhances sickle RBC adherence; (ii) HbS polymerization enhances sickle cell adherence in SRs and SMEs, but not in ISCs; (iii) SRs exhibit unique adhesion dynamics where HbS fiber projections growing outward from the cell surface create multiple sites of adhesion; and (iv) polymerization stimulates adhesion and vice versa, thereby establishing the bidirectional coupling between the two processes. These findings offer insights into possible mechanistic pathways leading to vasoocclusion crisis. They also elucidate the processes underlying the onset of occlusion that may involve circulating reticulocytes, which are more abundant in hemolytic anemias due to robust compensatory erythropoiesis.

迄今为止，聚合和粘附，动态过程是镰状细胞疾病（SCD）的标志，仅在体外进行了研究。在这里，我们介绍了人类红细胞（RBC）中脱氧镰刀血红蛋白（HbS）的黏附和聚合作用的协同效应和协同效应的定量结果，这些机制涉及血管闭塞性疼痛危机的潜在机制。为此，我们采用了专门开发的低氧微流控平台，该平台能够在体外诱导RBC的镰刀形和非镰形，以测试八名SCD患者的血液样本。我们用耗散粒子动力学对细胞粘附和生物流变学进行了详细的分子水平计算模拟，对这些实验结果进行了补充。借助图像分析技术，我们在缺氧条件下按照以下顺序对镰状红细胞的成熟阶段进行了表征：循环中的镰状网状细胞（SR）→镰状成熟红细胞（SME）→不可逆镰状细胞（ISC）。我们证明（i）缺氧显着增强镰刀对RBC的依从性；（ii）HbS聚合可增强SR和SME中镰状细胞的粘附性，但不能增强ISC中镰状细胞的粘附性；（iii）SR表现出独特的粘附动力学，其中从细胞表面向外生长的HbS纤维突起形成多个粘附部位；（iv）聚合反应刺激粘附，反之亦然，从而在两个过程之间建立双向偶联。这些发现提供了导致血管闭塞危机的可能机制的见解。他们还阐明了闭塞发作的潜在过程，该过程可能涉及循环网织红细胞，由于强烈的代偿性红细胞生成，在溶血性贫血中更为丰富。