Red Blood Cell Deformability Distribution as a Risk Marker for Diabetic Microangiopathy

Diabetic retinopathy (DR) is an ocular disease resulting from chronic microangiopathy in the retina. Poor hyperglycemic control in diabetic patients leads to vascular damage in the retina, resulting in the appearance of microaneurysms, neovascularization, and hemorrhaging in the retina and extending into the vitreous humor. This ultimately culminates in the partial or complete loss of vision. It has been established that the pathophysiology of DR involves the metabolic effects of chronic hyperglycemia, which result in changes in vascular changes leading to retinal ischemia. However, recent studies have alluded to the possibility of perfusion impairment leading to ischemia. This speculation is founded on the discovery that red blood cells (RBCs) lose their deformability due to inflammatory and hyperglycemic factors, along with elevated cholesterol and oxidative damage. This ultimately leads to retinal hypoxia, which stimulates neovascularization. In this study, we measured RBC deformability at the single cell level, and established the RBC deformability distributions in each stage of diabetes. By applying a uniaxial load at a moderate strain rate, we queried the extensional property of RBCs in diabetic conditions using a microfluidic cross‐slot device. We discovered that RBCs from diabetic patients exhibited a bimodal distribution, possibly stemming from increased reticulocytosis. Histograms of each patient group (C, D, N, or P) were plotted to visualize the RBC deformability distributions (n = 1400). The data was fitted with the automatic Gaussian peak analysis function in Origin (OriginLab, MA, USA), and column distribution statistics analyses were performed for each case. The objectives were to (1) more accurately define the distribution profiles based on the assumption of normality and (2) identify potential parameters to quantify the bimodality and distinguish between the different cases. The results indicate an apparent two‐phase shift in the deformability of the RBCs. In the first phase, from the control to diabetes stage, there is an emergence of a secondary peak at reduced deformability (EI = 1.46 ± 0.62). It is interesting to note that the primary peak (EI = 2.93 ± 1.35) coincides with the peak in the control case (EI = 2.94 ± 1.29). From the diabetes stage to the non‐proliferative diabetic retinopathy stage, the distribution reassumes a unimodal profile, but with a leftward shift (EI = 2.62 ± 1.78). Interestingly, from the nonproliferative to proliferative stage of diabetic retinopathy, there is another emergence of a very rigid subpopulation of RBCs (EI = 1.46 ± 0.65), corresponding to the same subpopulation in the D cohort. This bimodal characteristic was present even at the individual patient level, although it was not consistent across all patients in each group. Hence this bimodal behavior may be attributed to both inter‐ and intracohort statistical variability. The skewness and kurtosis values obtained from unimodal Gaussian curve fits revealed no apparent trend across the cases, and hence do not serve as good parameters to quantify the bimodality or severity of the disease progression. In this pilot study, we discovered that RBCs from patients with DM and DR exhibited a bimodal distribution, possibly stemming from increased reticulocytosis. EI of RBCs from patients with DM and DR was significantly lower in comparison with normal healthy controls. Support or Funding Information This study was supported by CSCS/15004 (TR15CSC053) This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal .