Ultra-structural changes in collagen of penile tunica albuginea in aged and diabetic rats

Tunica albuginea (TA) of the penis, which has an important role in mechanism of erection, is composed mainly of collagen bundles. Both aging and diabetes mellitus (DM) were reported to be associated with many alterations in collagen content and architecture in several body tissues. So, the aim of this work was to evaluate the effects of both conditions on the collagen bundles of penile TA in rats. Our diabetic models were three groups of Zucker Diabetic Fatty (ZDF) rats with non-insulin-dependent DM (NIDDM) aged 15, 40 and 75 weeks. Their age-matched controls were Zucker Fatty (ZF) rats. TA were excised from the side of mid-penile shaft and were examined by scanning electron microscopy using chemical digestion to extract collagen components. With aging, only the (70 w) ZF rats showed a significant increase in both thickness (P < 0.005) and loss of undulation of its bundles (P < 0.005) compared with the younger animals. In ZDF animals, a significant gradual increase in bundle thickness (P < 0.005) and loss of its undulation (P < 0.005) were found as the disease progressed to 40 w duration. Comparing these two parameters between both study groups showed that DM animals had significantly higher bundle thickness (P < 0.005) with loss of its undulation (P < 0.005) than controls starting from 40 w old. In conclusion, with progress of both aging and NIDDM, an increase in both thickness and loss of undulation of collagen bundles of penile TA was appreciated. The association of DM with aging could represent a cofactor effect that ultimately led to a greater impact on architecture of the bundles. The resulting changes may explain the compromised rigidity of the penis during erection under both conditions.