Quantitative assessment of sensing and sequestration of spherocytic erythrocytes by the human spleen

Abstract

IntroductionDuring their 120-day life span, human RBCs repeatedly traverse capillaries of the vascular bed and interendothelial slits of the venous sinus of spleen red pulp, both of which are narrower than their smallest dimension. 1 This necessitates maintenance of the ability of RBCs to undergo repeated, extensive, and reversible deformations. Repeated major membrane deformations induce ion and water permeability changes in the RBCs. [2][3][4][5] The biconcave discoid shape endows the human RBC with an advantageous surface area-to-volume (S/V) ratio, allowing the cell to undergo marked deformations while maintaining a constant surface area. [6][7][8] A reduced RBC S/V ratio has long been recognized to contribute to pathogenesis of several RBC disorders, 9-11 including hereditary spherocytosis (HS), the most common cause of inherited chronic hemolytic anemia in Northern Europe and North America, with an estimated incidence of 1 in 2000. 11 The clinical presentation of HS can range from mild to severe hemolytic anemia. 12,13 The molecular basis of HS is heterogeneous, the common denominator being the loss of HS RBC membrane surface area due to specific molecular defects in several membrane proteins (␣ or ␤ spectrin, ankyrin, protein 4.2, and protein band 3), which result in the loss of cohesion between the lipid bilayer and the membrane skeleton. 10,11,14,15 The loss of membrane surface area results in the transformation of the biconcave discoid shape, first to a stomatocyte and finally to a spherocyte, with a progressive reduction in cellular deformability.Although a major role for the spleen in pathogenesis of HS is well established, 16 there are currently no data on the quantitative relationship between the extent of surface area loss and the extent of splenic entrapment. The only indirect evidence comes from early studies documenting reduced survival of Cr 51 -labeled spherocytes infused into healthy recipients, whereas the survival of normal RBCs in HS subjects was normal. [17][18][19] This implied that the reduced life span and splenic entrapment was an intrinsic feature of HS RBCs. Unfortunately, because neither the surface area nor the S/V ratio of infused spherocytes was measured in these studies, the extent of membrane surface area loss (or reduced S/V ratio) that leads to splenic retention of altered RBCs remains undefined. As a result, there is no predictive biologic parameter with which to estimate the risk of splenic entrapment of spherocytic cells and the ensuing anemia. Previously, we addressed this important issue using the isolated human spleen system 20 perfused with human RBCs with defined extents of surface area loss.RBCs with defined loss in membrane surface area can be generated experimentally by treatment with lysophosphatidylcholine (LPC). 6,7 By initially accumulating exclusively in the external leaflet of the RBC lipid bilayer, LPC induces in a dose-dependent manner echinocytosis There is an Inside Blood commentary on this article in this issue.The online version of this article contai...

In Vivo Splenic Clearance Correlates with In Vitro Deformability of Red Blood Cells from Plasmodium yoelii-Infected Mice

“…Drug-induced changes in RBC size and shape are one possible factor (47) that could have a direct impact on RBC deformability (35,43,48,49). Indeed, significant changes in the size and sphericity of iRBCs (trophozoites and schizonts) were observed (see Fig.…”

“…As the red pulp of the spleen is capable of retaining the abnormal and hardened RBCs, a fraction of splenic minced RBCs was attributable to the splenic trapped RBCs, while the remainder would represent healthy, normally circulating RBCs (34). Therefore, two significant RBC subpopulations in the spleen minced RBCs were assumed: (i) "flowthrough" RBCs that share very similar mechanical properties with the peripheral RBCs and (ii) abnormal or senescent RBCs that were trapped in the splenic meshwork (16,35). Mathematically the population wide splenic RBC velocity profile can be expressed as follows: V SMB ϭ (1 Ϫ a 1 )V PVB ϩ a 1 V trapped , where V SMB , V PVB , and V trapped represent the average deformabilities (or velocities) of SMB, flowthrough, and splenic trapped RBCs, respectively, and a 1 denotes the fraction of SMB that came from spleen-trapped cells.…”

Lipid bilayer and cytoskeletal interactions in a red blood cell

“…Furthermore, when the RBCs pass through the interendothelial slits in the spleen, they undergo severe deformation. Here, the biophysical properties mediated by the bilayer-cytoskeletal interactions may play a significant role in the ensuing mechanical filtering process (5,6).…”

Functional significance of glutamate–cysteine ligase modifier for erythrocyte survival in vitro and in vivo

“…Injured erythrocytes are mainly sequestered in the spleen where they are cleared from the bloodstream. 16 Thus, we performed histological analyses of the spleens at 24 h post-PHZ treatment. As expected, greater number of erythrocytes were apparent in the spleens of gclm À / À mice, as evident from hematoxylin and eosin stain (H&E) and iron staining (Figure 3a).…”