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Regenerating the Anal Sphincter: Cytokines, Stem Cells, or Both?

Sun, Li M.D.; Xie, Zhuojun M.D.; Kuang, Mei Ph.D.; Penn, Marc M.D., Ph.D.; Damaser, Margot S. Ph.D.; Zutshi, Massarat M.D.

Diseases of the Colon & Rectum: April 2017 - Volume 60 - Issue 4 - p 416–425
doi: 10.1097/DCR.0000000000000783
Original Contributions: Pelvic Floor
Denotes Associated Video Abstract

BACKGROUND: Healing of an anal sphincter defect at a time distant from injury is a challenge.

OBJECTIVE: We aimed to investigate whether re-establishing stem cell homing at the site of an anal sphincter defect when cytokine expression has declined using a plasmid engineered to express stromal derived factor 1 with or without mesenchymal stem cells can improve anatomic and functional outcome.

DESIGN: This was a randomized animal study.

SETTINGS: Thirty-two female age- and weight-matched Sprague Dawley rats underwent 50% excision of the anal sphincter complex. Three weeks after injury, 4 interventions were randomly allocated (n = 8), including no intervention, 100-μg plasmid, plasmid and 800,000 cells, and plasmid with a gelatin scaffold mixed with cells.

MAIN OUTCOME MEASURES: The differences in anal sphincter resting pressures just before and 4 weeks after intervention were used for functional analysis. Histology was analyzed using Masson staining. One-way ANOVA followed by the Tukey post hoc test was used for pressure and histological analysis.

RESULTS: All 3 of the intervention groups had a significantly greater change in resting pressure (plasmid p = 0.009; plasmid + cells p = 0.047; plasmid + cells in scaffold p = 0.009) compared with the control group. The plasmid-with-cells group showed increased organization of muscle architecture and increased muscle percentage, whereas the control group showed disorganized architecture at the site of the defect. Histological quantification revealed significantly more muscle at the site of defect in the plasmid-plus-cells group compared with the control group, which had the least muscle. Quantification of connective tissue revealed significantly less fibrosis at the site of defect in the plasmid and plasmid-plus-cells groups compared with the control group.

LIMITATIONS: Midterm evaluation and muscle morphology were not defined.

CONCLUSIONS: At this midterm follow-up, local delivery of a stromal derived factor 1 plasmid with or without local mesenchymal stem cells enhanced anal sphincter muscle regeneration long after an anal sphincter injury, thereby improving functional outcome. See Video Abstract at

1 Department of Colorectal Surgery, Cleveland Clinic, Cleveland, Ohio

2 Department of Biomedical Engineering, Cleveland Clinic, Cleveland, Ohio

3 Summa Cardiovascular Institute, Akron, Ohio

4 Glickman Urological & Kidney Institute, Cleveland Clinic, Cleveland, Ohio

5 Advanced Platform Technology Center, Louis Stokes Cleveland Department of Veterans Affairs Medical Center, Cleveland, Ohio

Funding/Support: This study was funded by the Armed Forces Institute of Regenerative Medicine (AFIRM-2) W81XWH-13-AFIRMIIRP grant.

Financial Disclosure: Dr Penn is the inventor of the SDF-1 plasmid and a founder of Juventas Therapeutics Inc.

Podium presentation at the meeting of The American Society of Colon and Rectal Surgeons, Los Angeles, CA, April 30 to May 4, 2016.

Correspondence: Massarat Zutshi, M.D., Cleveland Clinic, Department of Colorectal Surgery, 9500 Euclid Ave, A30, Cleveland, OH 44195. E-mail:

© 2017 The American Society of Colon and Rectal Surgeons