Hematopoietic stem cell origin of adipocytes

Objective It has generally been believed that adipocytes are derived from mesenchymal stem cells via fibroblasts. We recently reported that fibroblasts/myofibroblasts in a number of tissues and organs are derived from hematopoietic stem cells (HSCs). In the present study, we tested the hypothesis that HSCs also give rise to adipocytes. Materials and Methods Using transplantation of a single enhanced green fluorescent protein−positive (EGFP+ ) HSC and primary culture, we examined generation of adipocytes from HSCs. Results Adipose tissues from clonally engrafted mice showed EGFP+ adipocytes that stained positive for leptin, perilipin, and fatty acid binding protein 4. A diet containing rosiglitazone, a peroxisome proliferator−activated receptor-γ agonist, significantly enhanced the number of EGFP+ adipocytes. When EGFP+ bone marrow cells from clonally engrafted mice were cultured under adipogenic conditions, all of the cultured cells stained positive with Oil Red O and Sudan Black B and exhibited the presence of abundant mRNA for adipocyte markers. Finally, clonal culture- and sorting-based studies of Mac-1 expression of hematopoietic progenitors suggested that adipocytes are derived from HSCs via progenitors for monocytes/macrophages. Conclusion Together, these studies clarify the current controversy regarding the ability of HSCs to give rise to adipocytes. Furthermore, our primary culture method that generates adipocytes from uncommitted hematopoietic cells should contribute to the studies of the mechanisms of early adipocytic differentiation and may lead to development of therapeutic solutions for many general obesity issues.