Molecular profiling of Ebf2+ and Ebf2- PαS mesenchymal stem cells from mouse dorsal skin

While extensive efforts have been on understanding bone marrow (BM) niche contribution to normal and malignant hematopoiesis, the role of extramedullary niches has been largely ignored. Evidence suggests a BM mesenchymal stem cell (MSC) counterpart exists in skin. However, their native identity and role in hematopoiesis remain unexplored. Here, we demonstrated that mouse skin harbors MSC subsets that are phenotypically and molecularly similar to BM MSCs, including a primitive MSC population marked by Early B-cell Factor 2 (Ebf2) and downstream MSCs lacking Ebf2. Functionally, skin MSCs not only support acute myeloid leukemia (AML) stem cells but also protect them from chemotherapy. This persistence of AML cells in skin were further amplified in AML-promoting microenvironment lacking Lama4. Our study demonstrated the features of extramedullary niches in skin and their previously unrecognized role in supporting AML stem cells during chemotherapy, opening a new path for understanding the extramedullary manifestation of AML in patients. Examination of mRNA profiles in skin mesenchymal stem cells sorted from 3 mice and bone marrow mesenchymal stem cells sorted from 4 mice.