Does Stem Cell Therapy Work for Crohn's Anal Fistulas?

Stem cell therapy is an innovative, minimally invasive treatment for complex anal fistulas in people with Crohn’s disease whose fistulas have not healed with standard biologics or conventional surgery ^[1][2]. The treatment uses mesenchymal stem cells (often a specific therapy called darvadstrocel, or Alofisel), which are specialized cells derived from healthy donor fat tissue ^[2]. Instead of physically cutting out or opening the fistula tract, doctors inject these stem cells directly into the walls of the fistula to calm the local immune response and help the tissue heal from the inside out ^[3][4].

Note on Availability: While darvadstrocel is approved for use in Europe, the UK, and Japan, it is not currently FDA-approved in the United States. In the US, it may only be accessible through clinical trials.

How Does the Treatment Work?

The procedure is typically performed in an operating room while you are under anesthesia. The therapy relies on two major steps: careful surgical preparation and the stem cell injection itself ^[2][5].

The Procedure

First, the surgeon cleans out the fistula tract (a process called curettage) and mechanically closes the internal opening inside the rectum ^[2][5]. If you currently have setons in place to keep the fistula draining, they are removed during this surgical preparation. After the tract is prepared, the surgeon injects a solution containing millions of stem cells directly into the tissue walls surrounding the fistula ^[2].

The Mechanism of Healing

Unlike medications that you take as a pill or infusion, these stem cells act locally at the site of the fistula. They promote healing through two main mechanisms:

• Calming Inflammation (Immunomodulation): Crohn’s fistulas are kept open by constant, localized inflammation. The injected stem cells interact with your immune cells and release signals that dial down this overactive immune response, creating an environment where healing can begin ^[3][4].
• Tissue Regeneration: Once the inflammation is reduced, the stem cells encourage the growth of new blood vessels and support the natural regeneration of healthy tissue, encouraging the fistula tract to fill in and close ^[3][4].
• No Match Required: Even though the cells come from a donor, mesenchymal stem cells do not require a genetic match. They do not trigger a rejection response in your body, meaning you do not need to take anti-rejection drugs like an organ transplant patient would ^[2].

How Effective Is It?

Research shows that stem cell therapy can offer significant hope for stubborn fistulas. In a landmark clinical trial called ADMIRE-CD, 50% of patients who received the stem cell injection achieved combined remission—meaning the external openings closed and an MRI confirmed there were no hidden abscesses—compared to 34% in the placebo group ^[2]. Long-term follow-up has shown that this healing can be sustained for up to two years or more ^[6][7].

However, a more recent phase 3 trial (ADMIRE-CD II) failed to meet its primary goal. It showed that the stem cell injection did not outperform the placebo. In this study, nearly half of the patients in both the stem cell group and the placebo group achieved remission ^[5]. This finding underscores that the meticulous surgical cleaning and closure of the internal opening (which both groups received) is a powerful driver of healing on its own, though the stem cell injection remains a valuable tool for complex, hard-to-treat cases ^[5].

Safety and Patient Eligibility

One of the biggest advantages of stem cell therapy is its favorable safety profile ^[1][8]. Because the treatment involves injections rather than cutting through the anal sphincter muscles, it does not increase the risk of fecal incontinence—a common concern with traditional fistula surgeries ^[9][10].

The therapy is generally well-tolerated, with the most common side effects being typical postoperative issues like temporary pain or the development of an anal abscess ^[2][11].

It is specifically indicated for adults whose intestinal (luminal) Crohn’s disease is either inactive or only mildly active ^[12]. If your intestinal inflammation is severe, your medical team will likely focus on calming the gut before attempting stem cell therapy for a fistula ^[12]. You will generally continue taking your standard Crohn’s medications (like biologics) to keep your intestinal disease controlled while the fistula heals.

What to Expect During Recovery

Following the procedure, you may experience some mild discomfort or pain in the perianal area, similar to other minor anal surgeries. While recovery is generally faster than with traditional sphincter-cutting surgeries, you will still need to limit strenuous activities for a short period to allow the internal closure to heal. Your doctor will likely schedule a follow-up exam and an MRI—usually several months later (e.g., at 6 months)—to confirm whether the fistula has truly healed internally.