Hematopoiesis in regenerated bone marrow within hydroxyapatite scaffold

We examined whether regenerated bone marrow (BM) with BM-derived stromal cells (BMSCs) on hydroxyapatite (HA) scaffolds can reconstitute the functional niche. Ly5.2 BMSCs on HA scaffolds were implanted s.c. onto the backs of Ly5.2 recipient mice. Lineage negative Ly5.1 BM cells expressing luciferase (luc) were i.v. administered into the recipient mice. Eight weeks after primary transplantation, secondary implantation was performed; the scaffolds removed from the first recipient mice were s.c. implanted into secondary recipient mice. Luc+ cells were detected in the scaffolds for 6 mo after secondary implantation. Injection of G-CSF resulted in wide distribution of bioluminescence from the original scaffolds to the whole body. Even after removing the scaffolds from the secondary recipient mice, luc+ cells were emitted by G-CSF stimulation, indicating that regenerated BM is capable of supporting hematopoietic stem cells (HSCs) and delivering HSCs to native BM in vivo. These data suggest that the functional niche is reconstituted at least partly and that regenerated BM on the scaffold may be used as a portable source of HSCs.