Adipose-derived stromal cells grown on a hydroxyapatite scaffold can support hematopoiesis in regenerated bone marrow in vivo

Osteoblastic cells are a key component of the bone marrow (BM) stem cell niche and help regulate hematopoietic stem cells (HSCs). We have previously demonstrated that adipose-derived stromal cells (ADSCs) can differentiate into both osteogenic and chondrogenic cells in vitro. The current study examined whether the anatomical architecture of the BM could be regenerated in vivo by using ADSCs cultured on a hydroxyapatite (HA) scaffold. ADSCs from GFP transgenic mice were cultured in vitro on an HA scaffold. The scaffold with the attached cells was implanted subcutaneously onto the backs of C57/BL6 (Ly5.2) recipient mice. Lineage-negative (Lin-) Ly5.1 BM cells transduced with a lentiviral vector containing the luciferase (Luc) gene were intravenously administered to the recipient mice after lethal irradiation. Eight weeks after BM transplantation, the scaffolds were removed from the first recipient mice and subcutaneously implanted into lethally irradiated second recipient mice. The biodistribution and kinetics of Luc(+) Ly5.1 cells were monitored by bioluminescence imaging and flow cytometry. Luc(+) hematopoietic cells were present in the scaffolds of the secondary implanted mice for at least 8 months. Subcutaneous injection of G-CSF resulted in wide distribution of bioluminescence signals from the original scaffolds to the whole body. Therefore, BM regenerated using ADSCs grown on an HA scaffold can support HSC populations in vivo, suggesting that a functional BM niche is reconstituted. These results may have a significant impact on the development of therapeutic strategies for various hematopoietic diseases.