Identification Of Hematopoietic Stem Cell Self-renewal And Amplification- Related Niche Cells And Genes

HSC transplantation is a most effective therapy for many hematopoietic diseases such as bone marrow failure, leukemia and lymphoma. However such treatment is limited by the shortage of HSC resources. In vitro amplification of HSC is believed to be the most efficient way to address such problem. Studies suggested that HSC self-renewal and amplification in vivo is regulated by signaling emerged from bone marrow microenvironments(Niches). However, in current in vitro culture system, due to the lack of Niche signal protection, HSCs are exhausted primarily because of diminished self-renewal capacity. We speculated that by identification of cellular and molecular components that are involved in regulation of HSC self-renewal in bone marrow niche, we might be able to improve in vitro HSC amplification through best manipulating bone marrow niche by addition of self-renewal promoting factors and removal of undesirable factors from culture system.In bone marrow of 5-FU-treated mice and newborn mice, HSCs first undergo amplification and then become quiescent dynamic changes. To support such changes, the niche environment also undergoes dynamic changes. By taking the advantage of these two conditions, we investigated the HSC-correlated changes of bone marrow non-hematopoietic cells and gene expression. Results showed that alterations of CD45-Ter119-CD140a+ cells and CD45-Ter119-CD31 high cells in both conditions were correlated to HSC alterations. In addition, by using colony-forming assay, we found that mesenchymal stem cells(MSCs) were enriched in CD45-Ter119-CD140+ cells. The dynamic alterations of MSCs were also correlated to HSC changes. These data suggested that CD45-Ter119-CD140+ cells and CD45-Ter119-CD31 high cells might be involved in regulating HSC self-renewal and expansion.In order to identify HSC self-renewal and amplification-related niche genes, we isolated non-hematopoietic cells from bone marrow of mice at different time points after 5FU treatment and also mice during early postnatal development. Gene expression profiles were examined and compared by deep RNA sequencing assay. Such high-throughput RNA sequencing allow us to identify 5066 differentially expressed genes, which contain large amount of biological information. By carefully analysis, we were able to indentify many differentially expressed secrete fectors and cell membrane proteins. We believe that these proteins can directly interact with HSC and provide stimulation of repression activity to HSC. We are in the process to verify the function of the top candidate genes.