Abstract
Purpose:
Diabetic retinopathy (DR) is the leading cause of new cases of blindness among the working aged population in North America. One of the most important morphological manifestations of the disease is pericyte loss as described in animal models. The purpose of this study is to evaluate the presence of pericytes in vitreous samples from diabetic and non-diabetic patients.
Methods:
Vitreous specimens from 125 patients who underwent pars plana vitrectomy for different clinical conditions were analyzed. All samples were centrifuged and the sediment was processed to obtain a cell block, for routine paraffin embedded histopathological sections. Forty cases (32%) had blood vessels in the vitrectomy sections and were selected for further analysis. Detailed clinical data, including glycemia, creatinine, and glomerular filtration rate (GFR), were recorded. The presence of pericytes was evaluated by immunohistochemistry for alpha-smooth muscle actin (aSMA), and was quantified using the following scoring system: total loss (3), >50% loss (2), <50% loss (1), and no loss (0). The results were evaluated using a digital scanner to compare the immunohistochemical results of the vitrectomy samples between diabetic and non-diabetic patients.
Results:
Thirty-three of the 40 cases were included in the subsequent analysis due to the unequivocal presence of blood vessels. The average age was 60.42±12.9 years; 22 samples were from males; and 29 samples were from diabetic patients. The 29 diabetic patients had DR. Six diabetic patients had a score of 1 (less than 50% pericyte loss); 8 diabetic patients had a score of 2 (>50% pericyte loss); 15 patients had a score of 3 (absence of pericytes). A positive correlation between glycemia levels and pericyte loss was observed (r2=0.21, P=0.04). Moreover, all non-diabetic cases had a score of 0 (no pericyte loss), while all diabetic cases showed some degree of pericyte loss (sensitivity and specificity = 100%).
Conclusions:
To the best of our knowledge, this is the first study analyzing cell block sections of vitrectomy samples using immunohistochemistry and digital pathology. Pericyte loss is a sensitive and specific marker of DR and correlates with glycemia levels. This finding supports the hypothesis that hyperglycemia is the primary cause of DR. This technique may be used to evaluate DR-like damage in glucose intolerant patients.