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Gremlin 1 expressing cells appear to be skeletal stem cells
DOI:10.1038/bonekey.2015.55
In an effort to identify a skeletal stem cell, Worthley et al. traced the lineage of rare stem cells in vivo in mice using Gremlin 1 (Grem1), a specific antagonist of bone morphogenetic protein 1 (BMP1) as a specific marker for mesenchymal stem cells (MSCs).
Cells expressing Grem1 were found very close to the bone growth plate and trabecular bone. Grem1 positive osteochondroreticular (OCR) stem cells were shown to be distinct from traditional perisinusoidal MSCs and appear to make a greater contribution to development of the skeleton in the early postnatal period. Grem1-expressing reticular stem cells were also identified in the small intestine and shown to self renew, forming the periepithelial mesenchymal sheath.
Grem1+ OCR stem cells were shown to be multipotent, with the capacity to differentiate to form osteoblasts, reticular marrow stromal cells and chondrocytes, but they were not able to give rise to adipocytes. The authors suggest that these stem cells could be harvested from a donor animal and, after expansion in vitro, used in transplant therapy for fractures in recipient animals.
Editor’s comment: It is interesting that Grem1-positive OCR stem cells can generate osteoblasts, chondrocytes and reticular marrow stromal cells but not adipocytes, and that small intestinal Grem1-positive cells also serve as intestinal reticular stem cells that can generate the periepithelial intestinal mesenchymal sheath.
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