A study on etiology of incontinence in double knockout mouse model.

INTRODUCTION AND OBJECTIVE: Stress urinary incontinence is of concern in both pediatric and adult population. Double mutant GLI family zinc finger Gli2+/-; Gli3Δ699/+ murine model of stress incontinence has been recently developed as a reliable model which does not require surgical manipulation to create incontinence and is shown to survive to adulthood. The aim of this study was to establish the etiology of incontinence in the double mutant Gli2+/-; Gli3Δ699/+ mice. STUDY DESIGN: We used 13 cluster of differentiation 1 (CD-1) mice (7-9 weeks) for demonstration of histology of the bladder and urethra. There were 3 Wild Gli2+/- females, 2 Wild Gli2+/- males, 4 Gli2+/-;Gli3Δ699/+ females and 4 Gli2+/-;Gli3Δ699/+ males. The Wild Gli2+/- mice served as the control group and Gli2+/-;Gli3Δ699/+ mice served as the test group. Additionally, eight 16.5 days mice (2 each of Wild Gli2+/- females, Wild Gli2+/- males, double knockout (DKO) Gli2+/-;Gli3Δ699/+ females and Gli2+/-;Gli3Δ699/+ males) were used to assess the histology of the spinal cord. The gross appearance of bladder and urethra was studied using ink injection assays. Immunohistochemistry was done for smooth muscle actin and cytokeratin. RESULTS: Gross and histologic appearance confirmed the previously reported widening of bladder outlet and hypoplasia of smooth muscles in female urethra and also established them in the male urethra of Gli2+/-;Gli3Δ699/+ mice compared to Gli2+/- mice. The double knockout mice were smaller than the Gli2 mice (5.2 vs 6.1 cm, p = 0.002). Immunohistochemistry demonstrated epithelial hyperplasia and smooth muscle hypoplasia. Additionally, there was prostatic hypoplasia in the Gli2+/-;Gli3Δ699/+ male mice. The spinal cord length for body size appeared comparable between the Gli2+/- and Gli2+/-;Gli3Δ699/+ mice but histological evaluation revealed abnormal development of the caudal end of the vertebral body with premature termination of the spinal cord (Figure). DISCUSSION: The histological changes in the bladder neck and urethra were consistent to those previously reported. While previous report described the findings in female mice only, we confirmed that these findings are also present in males as well as prostatic hypoplasia, a possible additional factor leading to stress incontinence. The most important finding in the present study however, was the detection of premature termination of spinal cord in the DKO Gli2+/-; Gli3Δ699/+ mice which has not been reported previously and is likely a major contributor to incontinence in this model. CONCLUSION: The incontinence in male as well as female Gli2+/-; Gli3Δ699/+ mice is due to both myogenic and neurogenic involvement. These double knockout mice are a valuable model of stress incontinence related to neurogenic bladder due to low outlet resistance.

The impact of sex hormones on genital wound healing in mice: a comparative study.

INTRODUCTION AND OBJECTIVE: The effects estrogen and testosterone have on penile wound healing are still uncertain. This study evaluated the effects of these hormones on the wound healing process of penile and non-penile skin in wild-type (Mus musculus species) 4-5-week-old mice. METHODOLOGY: Seventy wild-type Mus musculus species were randomly assigned to four groups control (n = 17), 1-week post-operative topical estrogen (n = 18), 1-week pre-operative testosterone (n = 17), and immediate post-operative testosterone (n = 18). Incisions were made on the ventrum of the penis and dorsal neck skin. On post-operative day 3, 7, and 14, incision sites were harvested. Evaluation was performed grossly for postsurgical penile edema and histologically for inflammatory cell concentration, presence of fibrinopurulent materials and distribution of collagen-fibroblastic cells. Each treatment group was compared at the three post-operative time points using the Fisher-Freeman--Halton exact test. CD34 and androgen receptor immunohistostaining was performed for between-group differences to assess microvascular density or vasodilatation and androgen receptor upregulation. RESULTS: In this study, the experiment noted significant penile edema on post-operative day 7 in the testosterone groups, whereas less edema in the estrogen group (P = 0.010; Figure). On histologic evaluation of the penile wounds, a significantly increased inflammatory cell concentration was noted for both pre-operative and post-operative testosterone groups on post-operative day 14 (P = 0.023). The estrogen group revealed significantly increased fibrinopurulent material on the 3rd and 7th post-operative days (P = 0.045 and P = 0.005, respectively). No significant between-group differences in the collagen-fibroblastic distribution were noted over the three-time phases. On histologic evaluation of the skin wounds, no significant differences were noted between the groups for inflammatory cell concentration and presence of fibrinopurulent materials. However, compared with the testosterone treatment groups, a significant higher collagen-fibroblast distribution was noted in the estrogen groups on post-operative day 3 and 14 (P = 0.001 and P = 0.044, respectively). CONCLUSION: Sex hormones, when given peri-operatively, may affect the wound healing process in mice. Testosterone appears to stimulate a prolonged inflammatory effect on penile wounds. Conversely, estrogen induces a fibrinopurulent congregation early in the penile wound healing process. For general skin healing, estrogen induces earlier collagen and fibroblast distribution, whereas testosterone has a delayed effect. The findings of this study should be further investigated in larger animal model with longer follow-up period.