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Background: We have previously demonstrated increased pressures after MSC treatment after anal sphincterotomy. This study aims to evaluate homing after intravenous MSC injection and document quantitatively the EMG activity of the anal sphincter after injury and after treatment with MSC.METHODS:70 virgin female Sprague Dawley rats were randomly group into 2 treatment with sham groups direct injection to the anal sphincter(n=35) and intravenous(IV) tail vein injection(n-35). These were further divided in equal numbers of injury groups (sphincterotomy SP and pudendal nerve transection PNC).EMG testing was done before treatment.24 hours after injury, each animal was injected with either saline(PBS) or 2 million labelled green fluorescing protein(GFP) MSC. 10 days post injury, EMG was repeated. Stains used were alpha-actin for smooth muscles, GFP for MSC and DAPI for nuclear stain. Quantitative anal EMG for amplitude and frequency was analyzed in all groups. The data was analyzed using repeated measures mixed models. The model examined the effects of population(sham, SP, PNC), treatment condition (MSC,PBS), route (direct,IV), EMG read time (0, 10), on frequency and amplitude. Population was significant for both measures. Pairwise comparisons for each measure were made for the various population groups. Bonferroni corrections were applied to the P-Value to adjust for multiple comparisons. RESULTS:No statistically significant differences were noted on EMG amplitude and frequency after MSC treatment compared to the PBS (Sham) injection in the direct and IV groups among both sphincterotomy and pudendal nerve injury groups.Green GFP fluorescing cells were found bordering the external anal sphincter after direct and IV TX after in the sphincterotomy group and red fluorescing cells which are endothelial vascular structures were seen independent of the GFP(+) cells indicating that the GFP(+ ) MSC had traversed the blood vessels to lie in the connective tissue.CONCLUSION: MSC home to the injured anal sphincter after IV MSC treatment. MSC treatment did not affect EMG potentials after anal sphincterotomy and pudendal nerve crush. Pressure increases seen after MSC injection cannot be attributed to EMG activity
Results

Variable	Route	Treatment	Pre treatment	Post treatment	p value
Amplitude(µv)	Direct	PBS	1.67±0.21	0.99±0.23	0.04
Amplitude(µv)	IV	PBS	1.91±0.31	1.30±0.10	<0.001*
Amplitude(µv)	Direct	MSC	1.93±0.16	1.35±0.17	0.02*
Amplitude(µv)	IV	MSC	1.88±0.21	1.66±0.10	0.88
FrequencyHz	Direct	PBS	47.80±8.80	28.53±4.72	0.18
FrequencyHz	IV	PBS	41.89±16.46	18.96±3.91	0.04*
FrequencyHz	Direct	MSC	62.06±9.47	47±6.76	0.05*
FrequencyHz	IV	MSC	61.88±12.66	58.50±10.25	0.97