Stem cells for stress urinary incontinence: do they work?

Can stress urinary incontinence be treated with stem cells? In this article we look at a recent study that analysed and summarised the experience of many different studies on the subject.

What is stress urinary incontinence

Stress urinary incontinence is the involuntary loss of urine when you cough, sneeze, laugh, lift something heavy or exercise. It is the most common form of urinary incontinence and mainly affects women: according to the studies cited by the authors, it is a problem that affects between 20% and 44% of adult women, and the real number is probably higher, because many women do not talk to their doctor about it out of embarrassment.

The condition is caused by two mechanisms, which are often present together:

1. the urethra moves too much during effort because the pelvic floor gives it too little support, or
2. the sphincter, the ring-shaped muscle that closes the urethra, can no longer close it properly. With advancing age, any childbirths and the onset of menopause, the sphincter muscle shrinks in size and tone and, as a result, the supporting tissue weakens.

Current treatments and possible alternatives

Treatment for urinary incontinence follows a step-by-step approach. It starts with pelvic floor exercises guided by a specialist, usually a physiotherapist or a midwife, which remain the first-choice treatment, together with correcting any unhelpful habits and, in some cases, vaginal pessaries. Medicines such as duloxetine have limited effectiveness and several side effects.

When urine leakage persists despite the initial treatments and is particularly bothersome, the next step is medical procedures.

Specific substances can be injected around the urethra to make it "thicker" (bulking agents): they are minimally invasive, but the effect often wears off and they need to be repeated.

Another option is surgery, which consists of placing a tape under the urethra, also called a sling: it works well, but it is a synthetic mesh that stays in the body permanently and can cause problems in some patients. One study cited by the authors reports a new operation for mesh complications in 6.9% of cases at nine years.

None of these treatments repairs the damaged muscle: they replace it, support it or train it. Hence the idea of regenerative medicine.

How stem cell therapy for urinary incontinence works

Stem cells are cells that can turn into different types of tissue and release substances that stimulate the repair of nearby tissues. The idea is to inject them into the urethral sphincter so that they rebuild the missing muscle.

In most studies the cells come from the patient herself: a small piece of muscle is taken, usually from the thigh, with a biopsy; in the laboratory the muscle cells are isolated and multiplied, and after a few weeks they are injected into the urethra. The injection is given from the inside, through the urethra with an optical instrument, or from the outside, through the tissues around the urethra. Some studies use cells taken from fat, bone marrow, the lining of the mouth or umbilical cord blood.

The study on urinary incontinence and stem cells: the details

A group of researchers from Ras Al Khaimah Medical and Health Sciences University, in the United Arab Emirates, searched three large databases for all studies of women with stress incontinence treated with stem cell injections into the urethra, up to April 2026, following the PRISMA guidelines.

Of 1,729 articles examined, they selected 21, published between 2007 and 2026, with a total of 885 women in 15 countries. Most were small studies (15 patients on average) without a comparison group. Only five were randomised trials, that is, with patients assigned at random to the therapy or to an alternative. Fifteen studies used cells of muscle origin. Almost all patients had already tried at least one other treatment before, without success. The mean age ranged from 45 to 63 years, and patients were followed during treatment for 3 to 48 months.

Stress urinary incontinence and stem cells: what are the results

How many women improve with stem cells for the treatment of urinary incontinence?

Combining the results of 17 studies, 63.7% of women improved after treatment according to the success criterion chosen by each study (95% confidence interval from 56.7% to 70.5%). The result varies widely from one study to another, from less than half to almost eight women out of ten, partly because each study measured success in its own way: with the pad test, with a leakage diary or with dedicated questionnaires.

The comparison with placebo

This is the most important finding of the study. Two randomised trials compared stem cells with a placebo injection, that is, a solution without cells, using the same criterion: at least a halving of leakage episodes at 12 months. The result was practically identical in the two groups (risk ratio 1.02, non-significant difference).

The largest of these trials, carried out in 297 women at several centres, found an improvement in 53.6% of patients treated with placebo, when the researchers had expected 30%. The authors explain that the biopsy, the injection into the sphincter, frequent check-ups and expectations can in themselves improve symptoms, and that the needle itself can cause a small tissue reaction with a temporary "bulking" effect. Another placebo-controlled study measured the volume of the sphincter with ultrasound: it increased both with cells and with placebo, with no difference between the two groups.

In short, many women improve after the injection, but for now it cannot be shown that the cells are responsible.

Only one signal points in a different direction: in the large trial, among women who had already had surgery for incontinence in the past, a reduction in leakage of at least 75% was achieved by 40% of patients treated with cells compared with 16% of those treated with placebo. This is a subgroup analysis, which needs to be confirmed by dedicated studies.

The comparison with surgery

Two small randomised trials compared stem cells with the sling. In one, in 30 women, at 12 months 93.3% of the patients who had surgery had improved compared with 66.6% of those treated with cells, and complete cure was 80% versus 33.3%. In the other, with cells taken from the mouth, the initial results were close (negative cough test in 73% versus 80%), but at two years satisfaction was higher with surgery, which however had caused more complications, including pain during sexual intercourse.

What seems to matter

Subgroup analyses measured better results when the injection was guided by ultrasound (78% versus 57%), when patients had stress incontinence only and not urgency to urinate as well (76% versus 55%), and when pelvic floor physiotherapy followed the injection (78% versus 58%). These data should be taken with caution: for physiotherapy there were only two groups, and the ultrasound studies were also those with more selected patients. The type of cells, the injection route and the number of cells injected showed no differences.

Safety

Side effects were mostly mild and temporary. At the injection site: burning when urinating (for example 14 women out of 199 in the largest trial), urgency, minor bleeding and some cases of cystitis, usually resolved with antibiotics. At the biopsy site: pain, bruising, small haematomas. Some patients had difficulty emptying the bladder for a few days. Serious reactions were very rare: in the largest trial, one severe allergic reaction in 199 women, resolved within 24 hours.

The authors point out, however, that the studies had few patients and were short in duration: they are not enough to rule out rare or late complications, such as abnormal tissue growth or scarring.

What it means for patients

A woman who reads about "stem cells for urinary incontinence" should be told clearly that today this is an experimental therapy. The authors themselves conclude that it should not be offered as routine treatment, but only within controlled clinical trials.

The first step is still an assessment with a gynaecologist or urologist, and the gynaecological examination also helps to understand whether the incontinence is pure stress incontinence or mixed. Pelvic floor exercises guided by a physiotherapist remain the first-choice treatment, and surgery remains the most effective option when they are not enough.

Anyone who is offered paid stem cell treatment outside a clinical trial should ask what evidence exists, who checks how the cells are prepared and how the results are followed over time.

What are the limitations of this review

• Most studies were small and had no comparison group: the percentage of women who improved describes what happens after treatment, not the effect of the cells.
• Each study defined success in its own way, with different tests and questionnaires.
• There are only two comparisons with placebo, and those with surgery are small.
• The subgroups (ultrasound, type of incontinence, physiotherapy) are based on few studies and may be influenced by other differences between the studies.
• The review protocol had not been registered in advance, and only articles in English were included.
• Follow-up usually reaches 12-24 months: too short to judge how long the effect lasts and long-term safety.

Stress urinary incontinence and stem cells: message for doctors

The 63.7% response rate in the treated arms should be read together with the 53.6% response to placebo in the largest phase III trial. The risk ratio of 1.02 in the two placebo-controlled trials indicates that, with current evidence, the specific effect of the cells has not been demonstrated, although smaller benefits or benefits in selected groups, such as women who have already had surgery, cannot be ruled out. Comparisons with the sling favour surgery. To establish the real effectiveness of this treatment for urinary incontinence with greater certainty, we need trials controlled with a procedural placebo, standardised preparation and injection protocols, ultrasound guidance compared directly with unguided injection, clinically meaningful outcomes and follow-up of at least five years.

References

1. Mohammed Bahutair SN, Fathima S, Tayade KD, Akhter A, Dube R, Patni MM, Salama RAA. Post-Treatment Response and Safety of Stem Cell-Based Urethral Injection Therapy for Female Stress Urinary Incontinence: A Systematic Review and Meta-Analysis. Journal of Clinical Medicine. 2026;15(19):7737. doi:10.3390/jcm15197737. PubMed