Influence of periurethral injection of insulin-like growth factor-I on the expression of IGF-I and IGF-II mRNA following urethral sphincter muscle injury in female rats

Abstract

Objective To investigate the effect of periurethral injection of insulin-like growth factor(IGF)-Ⅰ on the expression of IGF-Ⅰ and IGF-Ⅱ mRNA during regeneration period following urethral sphincter muscle injury in female rats. Methods Model of urethral sphincter muscle injury was made in female virgin SD rats (n=50) by intravaginal balloon inflation. Then the rats were divid-ed randomly into treatment group (n= 25) and control group (n= 25), treatment group accepted peri-urethral injection of 1.0μg human IGF-Ⅱ to the middle urethral muscle, control group accepted nor-mal saline injection. Five rats in each group were sacrificed at 2, 4, 6, 8, 14 day respectively and the whole urethra specimens were processed for RT-PCR to detect the expression of IGF-Ⅰ ,Ⅱ mRNA. A normal control group (n = 5) was set without intravaginal balloon inflation and injection. Results The expression of IGF-Ⅰ mRNA in control group increased at day 4, 6, 8, 14, the IGF-Ⅰ/β-actin ra-tios were 0. 58±0.15, 1.73±0.31, 2.30±0.29, 0. 46±0. 06. The expression of IGF-Ⅰ mRNA in treatment group increased at all time points, as 0. 69±0.21, 1.45±0.17, 2.25±0.45, 2.90±0.49, 1.92±0. 31. The difference was significant on day 4, 14(P<0.01), and day 8 (P<0.05) compared with the control group. The expression of IGF-Ⅱ mRNA in control group increased at day 4, 6, 8, as 0.42±0. 14, 1.51±0. 59, 1.31±1.04. The expression of IGF-Ⅱ mRNA in treatment group in-creased at day 4, 6, 8, 14, as 1.04±0.23, 1.94±0.29, 1.75±0.41, 0. 81±0.15. The significant difference was noted on day 4 (P<0. 01)compared with the control group. No expression of IGF-Ⅰand Ⅱ mRNA in the normal control group. Conclusions The expression of endogenous IGF-Ⅰ and IGF-Ⅱ mRNA was up-regulated by periurethral injection of IGF-Ⅰ during regeneration period follow-ing urethral sphincter muscle injury in female rat. Our findings suggest that IGF-Ⅰ facilitates the re-generation of the urethral muscles and may play a role in treatment of stress urinary incontinence in-duced by urethral sphincter muscle dysfunction. Key words: Insulin-like growth factor; Urethral sphincter muscle; Injury; Stress urinaryincontience