title: Retinal capillary pericyte apoptosis in early human diabetic retinopathy.
abstract: OBJECTIVE
  To investigate the nature of retinal capillary pericyte dropout in early human diabetic retinopathy.
  
  
  METHODS
  In the present study, neural retinas of 12 postmortem eyes from 6 patients (3 diabetic and 3 nondiabetic) were first fixed in buffered formaldehyde and then digested with trypsin. The preparations of trypsin-digested retinal blood vessels were stained with terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) technique and then with perdiodic acid-Schiff technique (PAS), and counter-stained with hematoxylin to evaluate DNA fragmentation of cell nuclei and diabetic changes of retinal capillaries.
  
  
  RESULTS
  TUNEL-positive apoptotic pericytes were observed in retinal capillaries in all three diabetic patients in this study. The TUNEL-positive pericytes were presented as darker stained cells with PAS-hematoxylin staining. A few TUNEL-positive retinal capillary endothelial cells were discovered in both eyes of one of the three diabetic patients. Neither TUNEL-positive pericytes nor positive endothelial cells were found in the three nondiabetic patients. A variety of typical diabetic microvascular changes were noticeable with PAS-hematoxylin staining in trypsin-digested retinal preparations from diabetic patients. These changes included thickened capillary walls, microaneurysms, "ghost-cell"-appearance of pericytes, acellular segments of capillaries, and a decreased ratio of retinal capillary pericytes to endothelial cells. All of these changes are characteristics of diabetic retinal microangiopathy.
  
  
  CONCLUSIONS
  Retinal capillary pericyte apoptosis is a specific form of cell death which occurs during the early development of diabetic retinopathy. The significant decrease in the ratio of pericytes to endothelial cells and the predominant TUNEL-positive pericytes over endothelial cells suggest that a greater impact of apoptosis-related mechanisms occurs in pericytes than in endothelial cells and, thereby, a greater loss of pericytes takes place in early diabetic retinopathy. Apoptosis, therefore, is an important mechanism of pericyte dropout in the early diabetic retinopathy.
authors.affiliation: Department of Ophthalmology, Peking Union Medical College Hospital, Beijing, China.
authors.forename: W
authors.initials: W
authors.lastname: Li
authors.forename: M
authors.initials: M
authors.lastname: Yanoff
authors.forename: X
authors.initials: X
authors.lastname: Liu
authors.forename: X
authors.initials: X
authors.lastname: Ye
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D017209:Apoptosis; D002196:Capillaries / Q000473:pathology; D003930:Diabetic Retinopathy / Q000473:pathology*; D004730:Endothelium, Vascular / Q000473:pathology*; D005260:Female; D006801:Humans; D008297:Male; D012171:Retinal Vessels / Q000473:pathology*