**2. Cell therapy for USI**

Pharmaceutical treatment of SUI has not been successful [8]; in addition, periurethral injection of bulking agents has poor long-term efficacy and is associated with complications such as voiding dysfunction, abscess formation, and pulmonary embolism [9]. Several surgical procedures such as urethral sling surgery or installation of an artificial sphincter have been used to treat patients with SUI over last three decades [10]. Although these procedures can

© 2013 Shi et al.; licensee InTech. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2013 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

reinforce weak muscle tissue at the pelvic floor or around the urethra, deficient urethral sphincter function remains. Furthermore, surgery for SUI sometimes causes complications such as infection and postoperative voiding difficulty [11]. Autologous adult stem cell injection therapy for SUI has recently provided a promising alternative for sphincter tissue regeneration for repair of SUI. Stem cells obtained from skeletal muscle [12], bone marrow [13-15], umbilical cord [16], adipose tissue [17], and more recently, induced pluripotent cells [18] are regarded as possible candidates for use in this therapy. However, harvesting these types of cells is invasive and may cause complications. Furthermore, the amount of tissue that can be safely harvested in some patients, such as skeletal muscle-derived progenitor cells or bone marrow stem cells (BMSCs) in older individuals, limits clinical applications [19]. Thus, an autologous stem cell source that can be obtained using non invasive techniques would be desirable.

Mesechymal stem cells (MSCs) are often used as a cell source for cell therapy in two ways. First, stem cells are implanted directly into the tissues where repair is needed. By secreting paracrine factors, MSCs promote angiogenesis, decrease fibrosis, and recruit stem cells from native tissues to complete the repair, replacement, and regeneration processes at the injured sites. In addition, the surrounding normal cell- and tissue-based signals from the host envi‐ ronment guide the undifferentiated stem cells to give rise to the specific target cells required for tissue regeneration [20]. Second, stem cells are induced to differentiate into the target cells or tissue–like cells *in vitro*. The induced cells are then implanted into defective sites where normal cells and tissues are not available.

In clinical settings, most patients with SUI acquire chronic injuries related to urethral dys‐ function spanning years or even decades. In cases with extensive injuries and fibroblast formation, it would be better to induce the stem cells to differentiate into a myogenic lineage before injection, since the unhealthy or diseased environment (e.g. muscular dystrophy) may not be able to provide efficient differentiation cues required for efficient stem cells differen‐ tiation. Therefore, our strategy is to guide USCs to give rise to myogenic differentiation and then lead to repairing the deficiency, and also determine whether USCs can secrete paracrine factors to recruit the resident cells from the host to participate in tissue repair.
