Functional mesenchymal stem cells remain present in bone marrow microenvironment of patients with leukemia...

Mesenchymal stem cells (MSCs) and their progenies are important supporting cells in the bone marrow (BM) microenvironment. However, the function and kinetics of MSCs post-hematopoietic stem cell transplant (HSCT) remain unknown. In the present study, MSCs were cultured from a total of 76 BM samples from 15 patients receiving HSCT. Colony-forming unit fibroblasts in BM before pre-conditioning and 1, 3, 6 and 9 months post-HSCT were cultured and counted to quantify MSCs. Hematopoiesis-supporting activity of MSCs was observed with long-term culture of hematopoietic progenitors. An inhibitory effect of MSCs on in vitro lymphocyte proliferation was also observed. Results showed that post-HSCT MSCs supported in vitro hematopoiesis and inhibited lymphocyte growth. Moreover, the quantity of MSCs was reduced at an early stage and restored to baseline level 9 months post-transplant. The results indicate that functional MSCs remain present in the BM microenvironment, and these findings shed light on the understanding of BM microenvironment reconstitution post-HSCT.