Effects of local injection and intravenous injection of allogeneic bone marrow mesenchymal stem cells on the structure and function of damaged anal sphincter in rats.

Anal sphincter injury leads to damage to the anal structure and functions and has been identified as a major risk factor for fecal incontinence. Bone marrow mesenchymal stem cells (BMSC) with capacities of multi-differentiation, paracrine and low immunogenicity have been widely used in tissue repair and regeneration. The primary objective of this research was to compare the effects of different injection therapies of BMSCs on the injured anal sphincters. 96 SD female rats were randomly divided into four groups(n=24 each): intravenous injection, local injection, sham operation, and normal control. For the first three groups, 25% removal of the anal sphincter complex was performed 0.3 ml PBS (containing 107 GFP-labeled allogeneic BMSCs) were given accordingly to the treatment group 24h after operation for 7 consecutive days, while the sham operation group were injected with 0.3 ml PBS only. All cases were undergone evaluation in the 1st,7th,14th and 28th postoperative days. The rats were sacrificed on the 28th postoperative day, and the anal sphincters were dissected to analyze by morphological examination. At 14 days postoperatively, local injection of BMSC significantly improved the peak contraction pressure, electromyography amplitude and frequency of the injured anal sphincter compared with tail vein, but there was no significant difference in resting pressure until 28 days after sphincterectomy. Masson staining results confirmed that the local injection group had significantly more new muscles on the wound. BMSC could remarkably improve peak contraction pressure, EMG amplitude and muscle fibres on the wound, and local injection is superior to intravenous injection.