**1. Introduction**

Stress urinary incontinence (SUI) is the prevalent form of urinary tract infection [1], affecting nearly 34 million women in the US [2,3]. In men undergoing prostatectomy, postoperative removal of the catheter leads to urine leakage due to SUI in 50% of cases [4]. The costs of medicine and health care related to SUI are estimated to be \$26 billion US dollars annually [5]. Damage to the sphincter muscle around the middle segment of urethra and its connective tissue and nerves is a major cause of SUI [6]. The urethra consists of proximal, middle, and distal segments. The midurethra is a critical component in the urethral sphincter complex, which mainly consists of the inner smooth muscle and outer striated muscles. The striated muscle contributes the most to the complex. Urethral striated muscle is significantly reduced with increasing age. Thus, in patients with SUI, when the lost striated muscle can be restored, amelioration of SUI can be expected. Otherwise, the smooth muscle plays a lesser role, but it is still a desirable treatment target to recover sphincter function [7]. Strategies to replace skeletal muscle cells with stem cell therapy could be used in treatment of SUI.
