Reduction of endothelial and smooth muscle density in the corpora cavernosa of the streptozotocin induced diabetic rat

Purpose: Erectile dysfunction is one of the most prevalent complications of diabetes in males. Because adequate vascular perfusion is needed for appro priate erectile tissue function a likely reason for the high incidence of t his complication in diabetics is a pathological change associated with the disease in vascularization of erectile tissues. We investigate whether chro nic diabetes may induce changes in vascularization of the corpora cavernosa using a computerized image analysis system to quantify changes in the smoo th muscle and endothelial cell content of the corpora cavernosa of diabetic rats induced by streptozotocin 6 months previously, and compare these chan ges to those associated with aging. Materials and Methods: We studied 3 groups of rats, including 10-week-old u ntreated controls, diabetic rats treated with streptozotocin for 6 months s tarting at age 10 weeks and 18-month-old rats (aged). Penile shafts from th ese groups were excised, fixed, sectioned and immunostained with anti-smoot h muscle actin to identify smooth muscle cells and anti-CD31 to identify en dothelial cells. Computerized image analysis was used to quantify the perce nt area within the corpora cavernosa occupied by smooth muscle cells or end othelial cells, and the data were compared among the groups. Results: We identified a highly significant decrease in the percentage of s mooth muscle and endothelial cells within the cavernosa areas of diabetic r ats compared to control or aged rats. Mean cavernous smooth muscle cell con tent was 15.28 +/- 2.54% in control rats and 9.83 +/- 1.21% in diabetic rat s (p = 0.0001). Likewise, cavernous endothelial cell content was 6.93 +/- 0 .86% in the control group and 4.01 +/- 1.08% in the diabetic group (p = 0.0 001). However, no statistical difference of smooth muscle or endothelial ce ll content was found between control and aged rats. Conclusions: Using the streptozotocin treated rat as a model for diabetes, we showed that smooth muscle and endothelial cell density is significantly decreased in diabetic corpora cavernosa but not in normal aged rats. This o bservation is a further step toward the understanding of the pathomechanism s for diabetic related erectile dysfunction.