Defected red blood cell membranes and direct correlation with the uraemic milieu: the connection with the decreased red blood cell lifespan observed in haemodialysis patients

Abstract

Together with impaired production of erythropoietin and iron deficiency, the decreased lifespan of red blood cells (RBCs) is a main factor contributing to the chronic anaemia observed in haemodialysis (HD) patients. Atomic force microscopy is employed in this work to thoroughly survey the membrane of intact RBCs (iRBCs) of HD patients in comparison to those of healthy donors, aiming to obtain direct information on the structural status of RBCs that can be related to their decreased lifespan. We observed that the iRBC membrane of the HD patients is overpopulated with extended circular defects, termed 'orifices', that have typical dimension ranging between 0.2 and 1.0 μm. The 'orifice' index-that is, the mean population of 'orifices' per top membrane surface-exhibits a pronounced relative increase of order 54 ± 12% for the HD patients as compared to healthy donors. Interestingly, for the HD patients, the 'orifice' index, which relates to the structural status of the RBC membrane, correlates strongly with urea concentration, which is a basic index of the uraemic milieu. Thus, these results indicate that the uraemic milieu downgrades the structural status of the RBC membrane, possibly triggering biochemical processes that result in their premature elimination from the circulation. This process could decrease the lifespan of RBCs, as observed in HD patients.

Does the extracorporeal circulation worsen anemia in hemodialysis patients? Investigation with advanced microscopes of red blood cells drawn at the beginning and end of dialysis

“…Three-dimensional renderings of the whole cell (pre-HD [ Figure 1A] and post-HD [ Figure 1E]) and most important two-dimensional presentations of specific subareas of the RBC membranes (pre-HD [ Figure 1B show that the RBC membrane exhibits local defects of circular form ( Figure 1A and E), termed "orifices" for the rest of this work. 7,19 These defects were also recorded in the RBCs of the healthy donors. 7,19 An advantage of the AFM technique originates from the fact that obtained information of nanometer resolution comes in digital form.…”

“…7,19 These defects were also recorded in the RBCs of the healthy donors. 7,19 An advantage of the AFM technique originates from the fact that obtained information of nanometer resolution comes in digital form. Thus, it can be processed with the relevant software so that all the desired dimensions of the observed characteristics can be estimated with great accuracy by using the Z profile option (pre-HD [ Figure 1C] and post-HD [ Figure 1G]) of a specific line scan (pre-HD [ Figure 1B] and post-HD [ Figure 1F]).…”

“…Interestingly, the crevices are quite rare features exhibiting an order of magnitude lower relative incidence when compared to the orifices (see below). Extending the previous work by Stamopoulos et al, 7 here we employed SEM (in addition to AFM) to validate the observation of these RBC membrane defects with another technique that is minimally invasive (though not entirely noninvasive like AFM). The investigation of blood smears with SEM (Figure 2A) revealed the orifices and crevices of the RBC membranes as well (Figure 2B and C).…”

“…7,[17][18][19][20][21][22][23][24][25] With AFM and SEM, we accessed thorough structural information from the membranes of intact RBCs (iRBCs) of HD patients, drawn both pre-and post-HD. A comparison to healthy donors was also performed.…”

“…16 In a previous work, Stamopoulos et al reported the strong correlation of the orifice index with urea, but not with creatinine. 7 In the present study, excepting urea and creatinine, we investigated how the orifice index depends on the concentration of two other basic uremic markers, calcium and phosphorous. In our analysis, we divided HD patients into two subgroups, of low and high uremic marker concentration.…”