Objective     To study the differentiation of muscle-derived stem cells (MDSCs) and metergasis of periurethral intrinsic sphincter after MDSCs transplantation into proximal urethra of stress urinary incontinence (SUI) rats.      Methods     Sciatic nerve transection was used to establish rat model of SUI. MDSCs were isolated by improved preplate technique. After transfected with pEGFP-N1 plasmid

MDSCs were injected into proximal urethra of SUI rats. Urodynamic test was used to measure leak point pressure (LPP) and maximal bladder cap

acity at 1

st

week and 2

nd

week after MDSCs transplantation. On day 1

3

7

10

14 after injection

fluorocytes were observed by fluorescence microscope.      Results     LPP were significantly increased at 1

st

week and 2

nd

week after MDSCs injection

while LPP at 2

nd

week was significantly higher than that at 1

st

week. On day 1

3 after injection

the cells were small

round and short-fusiform

and distributed around the injected point; On day 7

some high-fluorescence cells were elongated and occupied larger area

but still localized within muscles surrounding urethra; On day 10

some fluorescent cells were long-fusiform and of strong fluorescence

while others lost normal form and were of weakened fluorescence; On day 14

fluorescent cells decreased with weakened fluorescence.      Conclusion     MDSCs could survive and differentiate after transplanted into proximal urethra of SUI rats and could improve function of sphincter muscle of urethra

suggesting that MDSCs transplantation may be an effective method to treat SUI.