Maturation And De-differntiation Potentials Of Partially-Differentiated Leukemia Cells And Isolation And Identification Of Novel Adult Stem Cells From Murine Bone Marrow

This dissertation has two parts: Part I addresses the maturation and differentiation potentials of partially-differentiated leukemia cells.According to the step-wise manner of LSC differentiation,combined use of RA and Irf8 induction depleted the total leukemogenic potential.Part II refers to the isolation and identification of novel adult stem cell from murine bone marrow.The LCSSC cells we isolated from murine bone marrow by flowcytometry were shown to potentially participate in the reconstruction of bone marrow,but the differentiation potential and characteristics needed further investigation.Part ? Maturation and de-differentiation potentials of partially-differentiated leukemia cellsThe differentiation of leukemia stem cells(LSCs)is generally regarded as a one-way alterative process to self-renewal.However,how differentiation impacts LSC stemness has largely been unexplored.Here we show that before reaching terminal differentiation(TD),apical LSCs of mouse acute promyelocytic leukemia passed through a partial differentiation(PD)stage,wherein the leukemia cells re-initiated leukemia via de-differentiation albeit at a reduced rate.Notably,while retinoic acid(RA)preferentially drove the transition of LSC to PD,monocytic Irf8 skewed PD cells to terminal maturation over de-differentiation and/or expansion.Remarkably,the combined use of RA and Irf8 induction depleted the total leukemogenic potential,which indicates that discrete stage-or lineage-specific mechanisms elaborate a step-wise LSC differentiation.Part ? Isolation and identification of novel adult stem cell from murine bone marrowIn addition to serving as the main hematopoietic organ,bone marrow is also a great pool for multiple types of adult stem/progenitor cells.Except for the well-documented hematopoietic stem cells,it is hypothesized that certain non-hematopoietic stem cells exist,possessing multiple lineage differentiation potentials.Our data showed a heterogeneity within the cell population of murine bone marrow Lin-CD45-Sca-1+ cells,which can be divided into at least two subpopulations according to their size.As the SSC(side scatter channel)of Lin-CD45-Sca-1+ cells was mediate,so we named them LCSSC instead.Interestingly,in the reconstruction bone marrow model generated by semi-lethal irradiation or 5-FU treatment,we observed that LCSSC entered into the cell cycle and proliferated transiently before the hematopoietic progenitors responded,and then went back to the quiescent status,indicating it might play a role in the bone marrow reconstruction post tissue injury.However,further studies are needed to clarify the pluripotency and differentiation potentials of large and small LCSSCs.