Hematopoiesis in Bone Marrow Regenerated from Adipose-Derived Stromal Cells.

Background: Adipose-derived stromal cells (ASCs) are highly promising cells for tissue engineering because of their pluripotency and low donor morbidity. We have previously shown that ASCs differentiate into a variety of mesenchymal tissues including bone and bone marrow (BM) like architecture. Osteoblastic cells lining the endosteal surface are a key component of the hematopoietic niche to promote and regulate hematopoietic stem cells (HSCs). In the present study, we investigated whether ASCs derived BM can functionally support hematopoiesis.

Methods: ASCs were isolated from the inguinal fat pads from C57/BL6 mice (Ly5.2) after collagenase treatment and were cultured for three passages in the culture plates. The attached cells were trypsinized and replated onto a hydoxyapatite (HA) scaffold with numerous small pores for 3 days. The scaffold with attached cells was implanted subcutaneously onto the back of C57/BL6 recipient mice. 4.0×105 Lineage negative (Lin-) Ly5.1 BM cells transduced with a lentiviral vector containing the luciferase (Luc) gene were intravenously administered into the recipient mice after lethal irradiation. After 8 weeks, the scaffolds including Luc+ cells were removed and re-transplanted to the lethally irradiated second recipient mice.

Results: Excised HA scaffolds were totally covered with adipose tissues. Hematoxylin-eosin staining showed that microspores were filled with typical bone marrow architecture composed of adipocytes, vasculatures, stroma, and a variety of hematopoietic cells. In vivo bioluminescence imaging showed that Luc+ hematopoitic cells were detected in the scaffolds in the secondary transplanted mice for at least 6 months after transplantation. Bioluminescence signals were also detectable on the whole body including the head, extremities, chest, and abdomen after G-CSF injection.

Conclusions: We demonstrated that BM could be regenerated by ASCs. The ASCs derived BM were capable of maintenance of hematopoietic progenitor cells in vivo. BM regeneration from non-BM cells raises new possibilities to treat various hematopoietic diseases.