[Impact of aging on the secretion of insulin-like growth factor-1 in the corpus cavernosum smooth muscle cells of rats in vitro].

OBJECTIVE: To observe the secretion of insulin-like growth factor-1 (IGF-1) in corpus cavernosum smooth muscle cells (CCSMCs) in rats of different ages and explore the possible relationship of IGF-1 with aging-related erectile dysfunction (ED). METHODS: We primarily cultured CCSMCs of rats aged 4, 12 and 24 months, and identified them by immunohistochemistry. We quantitatively cultured the CCSMCs in 6-well culture plates, determined the levels of IGF-1 secreted from the CCSMCs by enzyme immunoassay (EIA) and analyzed the effect of age on the IGF-1 level. RESULTS: CCSMCs were successfully cultured in vitro. The level of IGF-1 secreted from the CCSMCs was decreased with the increase of age, with 7.1 ng/10(5) cells in the 4-month-old group, 2.2 ng/10(5) cells in the 12-month group, and 1.9 ng/10(5) cells in the 24-month group, with statistically significant differences among the three groups (P < 0.01). CONCLUSION: The secretion of IGF-1 is reduced with the increase of age, and the decreased expression of IGF-1 might be associated with aging-related ED.

Improvement in erectile dysfunction after insulin-like growth factor-1 gene therapy in diabetic rats.

AIM: To determine whether adenoviral gene transfer of insulin like growth factor-1 (IGF-1) to the penis of streptozotocin (STZ)-induced diabetic rats could improve erectile capacity. METHODS: THE STZ diabetic rats were transfected with AdCMV-betagal or AdCMV-IGF-1. These rats underwent cavernous nerve stimulation to assess erectile function and their responses were compared with those of age-matched control rats 1 to 2 days after transfection. In control and transfected STZ diabetic rats, IGF-1 expression were examined by reverse transcription polymerase chain reaction (RT-PCR), Western blot and histology. The penis beta-galactosidase activity and localization of the STZ diabetic rats were also determined. RESULTS: One to two days after transfection, the beta-galactosidase was found in the smooth muscle cells of the diabetic rat penis transfected with AdCMV-betagal. One to 2 days after administration of AdCMV-IGF-1, the cavernosal pressure, as determined by the ratio of maximal intracavernous pressure-to-mean arterial pressure (ICP/MAP) and total intracavernous pressure (ICP), was increased in response to cavernous nerve stimulation. Transgene expression was confirmed by RT-PCR, Western blot and histology. CONCLUSION: Gene transfer of IGF-1 significantly increased erectile function in the STZ diabetic rats. These results suggest that in vivo gene transfer of IGF-1 might be a new therapeutic intervention for the treatment of erectile dysfunction (ED) in the STZ diabetic rats.