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hASCs: A Simple and Feasible Treatment Option for Anal Sphincter Muscle Injury

Review of “Functional outcome of human adipose stem cell injections in rat anal sphincter acute injury model” from STEM CELLS Translational Medicine by Stuart P. Atkinson

Injury to the anal sphincter muscle and the subsequent onset of anal incontinence (AI) can lead to a significant reduction in quality of life, especially in females [1]. Current treatment methods can be expensive and associated with multiple complications, and so, many research groups have begun to explore alternative therapeutic options, including stem cell therapy. Studies have described treatments with muscle-derived stem cells and bone marrow stem cells in animal models, while, most recently, a study reported a small trial [2] with easy to obtain and mesenchymal-like adipose-derived stem cells (ASCs) [3]. 

Now, the research group of Kirsi Kuismanen (University of Tampere, Finland) has assessed the efficacy of a hASC-based therapy in a rat AI model and their new STEM CELLS Translational Medicine study reports that the injection of hASCs isolated and expanded in clinically viable conditions represents a simple and feasible treatment option for anal sphincter muscle injury [4].

So what were the details of this new trial?

  • The trial employed 14-week old female Sprague-Dawley rats
    • Anal sphincter muscles cut and repaired to resemble the human injury
  • The study then divided rats into four treatment groups receiving injections into the anal sphincter muscle
    • Injection of 300,000 hASCs in saline solution
    • Injection of 300,000 hASCs in 2.5 % polyacrylamide hydrogel (as an enhanced ASC carrier)
    • Saline Control
    • Polyacrylamide hydrogel Control
  • The authors then assessed outcomes at two and four weeks post injection employing several methods
    • hASC treatment groups displayed improvements in median resting pressure and the peak pressure during spontaneous contraction of the anal sphincter complex
    • Histological analysis found no evidence of survival of hASCs and no statistical differences in sphincter muscle continuity, fibrosis, or collagen formation between the hASC and Control treatment groups
    • Both hASC treatment groups exhibited higher levels of inflammation, especially in the hASC in saline treatment group
    • Micro-computed tomography (μCT) analysis supported the histological findings

The authors hope that this animal study will demonstrate the simplicity and feasibility of human ASC injections as a treatment for anal sphincter muscle damage and AI and provide an impetus for additional studies in chronic injury animal models with more extended follow-up periods to confirm functional restoration.

For more on the potential of hASCs in anal sphincter muscle repair, and beyond, stay tuned to the Stem Cells Portal.


  1. Mundet L, Ribas Y, Arco S, et al., Quality of Life Differences in Female and Male Patients with Fecal Incontinence. J Neurogastroenterol Motil 2016;22:94-101.
  2. Sarveazad A, Newstead GL, Mirzaei R, et al., A new method for treating fecal incontinence by implanting stem cells derived from human adipose tissue: preliminary findings of a randomized double-blind clinical trial. Stem Cell Res Ther 2017;8:40.
  3. Lindroos B, Suuronen R, and Miettinen S, The potential of adipose stem cells in regenerative medicine. Stem Cell Rev 2011;7:269-91.
  4. Kuismanen K, Juntunen M, Narra Girish N, et al., Functional Outcome of Human Adipose Stem Cell Injections in Rat Anal Sphincter Acute Injury Model. STEM CELLS Translational Medicine 2018;7:295-304.