The following is general information introducing research findings. Results reported in studies do not mean the same outcome for any individual, and most of these studies are small or early-stage.
Summary — Research on bone marrow stem cells for infertility delivered encouraging clinical results in 2026. A team at the Sixth Affiliated Hospital of Sun Yat-sen University in China randomized 60 women with severe intrauterine adhesions (Asherman syndrome) and reported in Stem Cell Research & Therapy in August 2026 that the endometrium grew thicker when bone marrow-derived mesenchymal stem cells were infused into the uterine arteries than with hormone therapy alone, and that the clinical pregnancy rate after embryo transfer was 50.0% versus 23.3% in the control group. In May 2026, the Kulakov National Medical Research Center for Obstetrics, Gynecology and Perinatology in Russia reported that 11 of 35 women with recurrent intrauterine adhesions and thin endometrium gave birth after placenta-derived mesenchymal stem cell therapy. This article summarizes human studies published overseas in the past six months.
Intrauterine adhesions and thin endometrium — causes of infertility and standard care
For a pregnancy to begin, the embryo must implant in the lining of the uterus. The endometrium grows and sheds every cycle, but when its basal layer is damaged by curettage, uterine surgery or infection, the uterine walls can stick together, forming intrauterine adhesions. When adhesions are extensive and accompanied by reduced menstruation or repeated implantation failure, the condition is called Asherman syndrome. Even without adhesions, a thin endometrium that stays below 7 mm despite hormone therapy is known to make implantation harder in in vitro fertilization (IVF).
Standard care is hysteroscopic surgery to separate the adhesions, followed by estrogen-based hormone therapy to keep them from re-forming. Many women improve with this approach, but when adhesions are severe or recur, the lining may not grow enough for a pregnancy. This is why stem cell research aimed at regenerating the damaged basal layer has drawn attention. The basics of stem cell research in female infertility are on our female infertility stem cell page.
Bone marrow stem cells for infertility — a randomized trial of uterine artery infusion in 60 women
From July 2020 to December 2024, the team at the Sixth Affiliated Hospital of Sun Yat-sen University in Guangzhou (corresponding author Xiaoyan Liang) randomized 60 women with severe intrauterine adhesions 1:1. One group received cultured mesenchymal stem cells from donor bone marrow (BMSCs), delivered by catheter directly into the uterine arteries, together with hormone therapy; the other group received hormone therapy alone. The distinctive feature is this targeted uterine artery infusion, which carries the cells through the blood vessels close to the endometrium. The results were published online in Stem Cell Research & Therapy on 7 August 2026.
The primary endpoint, increase in endometrial thickness, averaged 0.79±0.66 mm in the stem cell group and 0.20±0.44 mm in the control group, a clearly larger gain with stem cells (P<0.001). In an exploratory analysis of participants who underwent embryo transfer, the clinical pregnancy rate was 50.0% in the stem cell group and 23.3% in the control group (P=0.038), and the live birth rate was also higher with stem cells, at 34.6% versus 16.7%. Tissue and gene-expression analyses showed more microvessels and more active angiogenesis signals (such as NOTCH and VEGF) in the endometrium of the stem cell group. The interpretation is that bone marrow stem cells may help restore the vascular environment of the lining and create better conditions for implantation.
Safety
No serious treatment-related adverse events were observed during the trial. The team plans to confirm these results in larger multicenter trials with live birth and long-term safety as main goals.
Placenta-derived stem cells in 35 women — 11 births in a Russian study
On 22 May 2026, a team at the Kulakov National Medical Research Center in Moscow published in the journal Life the results of 35 women with recurrent intrauterine adhesions and thin endometrium (below 7 mm) that had not improved with surgery and hormone therapy. In this prospective single-arm study, placenta-derived mesenchymal stem cells were given both beneath the endometrium and intravenously. The primary endpoint, live birth, was achieved by 11 of 35 women (31.4%), and clinical pregnancy was confirmed in 13 (37.1%). The median time to pregnancy was 7 months.
The team also analyzed which women did best. Shorter duration of infertility or pregnancy loss, milder adhesions (AFS stage I), lower blood-flow resistance in the uterine arteries before treatment, and higher AMH levels, a marker of ovarian reserve, were associated with live birth. Endometrial thickness increased after treatment, and no severe adverse events were observed. Such analyses can help define which women are best suited to future stem cell studies.
Study phase and how to read the results
The Chinese study is a randomized trial with a control group, so it shows the gain in endometrial thickness fairly clearly; its pregnancy and birth results were presented by the authors as exploratory analyses. The Russian study is a single-arm study without a control group, a real-world record in which about one in three women who had not responded to standard care gave birth. Because the two studies differ in cell source (bone marrow vs placenta) and route (uterine artery vs subendometrial and intravenous), their numbers are best read as results reported for each approach rather than compared directly. 'An effect was reported' is not the same as 'an effect was proven' for everyone, and research in more women is continuing. For another stem cell study in women's health, see our article on randomized stem cell trials in frailty.
Position in the Japanese system
In Japan, a medical institution that wishes to provide a treatment that administers cells to the endometrium or ovary must submit a plan, reviewed by a certified committee, to the Ministry of Health, Labour and Welfare under the Act on the Safety of Regenerative Medicine. As of October 2026 there is no approved stem cell product for intrauterine adhesions or thin endometrium, and these research results are used within each institution's plans and clinical studies. The overall framework is introduced in our timeline of regenerative medicine in Japan.
Frequently asked questions
Which women took part in the bone marrow stem cell infertility research?
The Chinese trial enrolled women with severe intrauterine adhesions; the Russian study enrolled women with recurrent intrauterine adhesions and an endometrium thinner than 7 mm that had not improved with surgery and hormone therapy. Whether this suits an individual is judged by the treating medical team based on the uterus, ovarian function and general health.
What do bone marrow stem cells do in the endometrium?
Mesenchymal stem cells are studied for releasing substances such as growth factors that reduce inflammation and help new blood vessels form. In the Chinese trial, more microvessels were found in the endometrium of the stem cell group, supporting the idea that a better-perfused lining helps implantation.
Is there similar research for reduced ovarian function (premature ovarian insufficiency)?
Clinical studies of mesenchymal stem cells and exosomes for premature ovarian insufficiency or diminished ovarian reserve are under way in several countries. Because the target organ and endpoints differ from endometrial research, we plan to introduce new human results separately as they are published.
Conclusion
In 2026, overseas journals published a series of human studies in which bone marrow stem cells and placenta-derived stem cells helped regenerate a damaged endometrium. A randomized trial reported a greater gain in endometrial thickness and a higher pregnancy rate, and births were reported even among women who had not responded to standard care. For families hoping for a child, endometrial regeneration is steadily taking shape as a new research direction. We will update this article as results from larger multicenter trials appear. The suitability and risks of any treatment are judged by the treating medical team.
This content summarizes published scientific papers. Names of universities and research institutions are given to identify research sources and do not introduce or recommend any medical institution. Suitability for treatment is judged by the treating medical team.
References
- Chang Y, Guo Q, Zeng Z, Yuan P, Wang D, Peng D, et al. Targeted uterine artery infusion of bone marrow-derived mesenchymal stem cells for severe intrauterine adhesions: a randomized controlled trial with exploratory translational analyses. Stem Cell Res Ther. 2026 (published online 2026-08-07). doi:10.1186/s13287-026-05216-w https://link.springer.com/article/10.1186/s13287-026-05216-w
- Factors Associated with Live Birth After Placenta-Derived Mesenchymal Stromal Cell Therapy in Women with Recurrent Intrauterine Adhesions and Thin Endometrium. Life (Basel). 2026;16(6):871 (published 2026-05-22). V.I. Kulakov National Medical Research Center for Obstetrics, Gynecology and Perinatology. doi:10.3390/life16060871 https://doi.org/10.3390/life16060871
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