What are MenSCs?

According to the World Bank, on any given day, over 300 million women around the world are menstruating (World Bank, Menstrual Health and Hygiene). Yet in many cultures, menstruation is still stigmatized — labeled as unclean, taboo, or even shameful. As a result, menstrual blood has historically been treated as a biological waste product, managed through sanitary products and promptly discarded.

However, emerging scientific research over the past two decades has revealed that menstrual blood contains biologically active stem cells with regenerative and immunomodulatory properties. Known as menstrual blood-derived mesenchymal stem cells (MenSCs), these cells are being investigated for their therapeutic potential in tissue repair, inflammation regulation, and disease modification across a range of conditions, including diabetes, liver disease, and intrauterine adhesions (Chen et al., 2019).

These stem cells, referred to in early literature as endometrial regenerative cells, were first characterized in 2007 by Dr. Caroline Gargett and colleagues in a foundational paper on endometrial stem cells (CE Gargett et al., 2007). MenSCs are a type of adult mesenchymal stem cell (MSC) that originate from the basal layer of the endometrium, the inner lining of the uterus. During the menstrual cycle, the functional layer of the endometrium proliferates in preparation for implantation; if fertilization does not occur, this layer is shed during menstruation.

Embedded within the shed tissue are progenitor-like stem cells, which detach from the basal layer and enter the menstrual blood during this regenerative turnover. Compared to traditional MSC sources such as bone marrow or adipose tissue, MenSCs are notable for their non-invasive collection, higher proliferative capacity, and lack of associated ethical concerns, particularly when compared to embryonic stem cells (ESCs).

MenSCs also exhibit significant biological characteristics:

• High proliferation rate: MenSCs exhibit a faster doubling time than bone marrow-derived MSCs (BM-MSCs), making them well suited for scalable expansion in culture

• Multipotency: They can differentiate into multiple lineages, including osteocytes (bone), adipocytes (fat), chondrocytes (cartilage), neurons, and even endothelial cells.

• Low immunogenicity: MenSCs exhibit low expression of MHC class II and lack key hematopoietic markers such as CD45, reducing the likelihood of host immune rejection and making them promising for allogeneic transplantation.

• Potent paracrine activity: They secrete cytokines like VEGF, IL-10, and TGF-β, which promote angiogenesis, reduce inflammation, and enhance tissue regeneration.

On the surface, they express the classic markers of MSCs — CD73, CD90, CD105 — while lacking hematopoietic and immunogenic markers like CD45 and HLA-DR. These markers are routinely used to confirm MSC identity and purity during manufacturing (Chen et al., 2019).

MenSCs have already been explored in both preclinical and early-phase clinical studies across a range of conditions. In Part II of this series, we will review the current landscape of MenSC clinical applications — including studies in critical limb ischemia, Asherman’s syndrome, and COVID-19 — and evaluate what the emerging data suggest about their therapeutic potential.

This article was reviewed by Dr Badrul Hisham Yahaya, Professor at the Stem Cell Biology and Regenerative Medicine in Universiti Sains Malaysia, Deputy Director (Research and Networks) at the Advanced Medical & Dental Institute and Editor-in-Chief of Journal of Biomedical and Clinical Sciences (JBCS). Access his biography here: https://www.amdi.usm.my/badrulyahayagroup.