Mesenchymal stromal cells (MSCs) have therapeutic potential for repairing tissue damage and are involved in immune regulation. MSCs are predominantly isolated from bone marrow (BM), adipose tissue or placental tissue. Further to these well-known sources, the isolation of MSCs from human tonsils was previously reported. The aim of the present study was to investigate a potential role for tonsil-derived MSCs (T-MSCs) in BM reconstitution and application towards supplementing hematopoiesis in a mouse model of BM transplantation (BMT). Eight-week-old BALB/c female mice received 80 mg/kg busulfan (Bu)/200 mg/kg cyclophosphamide (Cy) conditioning chemotherapy for BM ablation. Subsequently, human T-MSCs were injected into the Bu/Cy-treated mice with or without BM cells (BMCs) obtained from allogeneic C57BL/6 male mice. After 3 weeks, peripheral blood and BM was collected for analysis. The red blood cell count in the group that received BMCs had almost returned to normal, whereas mononuclear cell counts and BM cellularity were most improved in the T-MSCs + BMCs group. These results indicate that the T-MSCs enhanced myelopoiesis in the allogeneic BMT mouse model, as evidenced by the restoration of BM with hematopoietic cells, as well as increased myeloid colony formation in vitro. Therefore, T-MSCs may provide a source of MSCs to facilitate myelopoiesis and megakaryocytosis following BMT.

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