ABSTRACT
In both human chronic lymphocytic leukemia (CLL) and the New Zealand Black (NZB) murine model of CLL, decreased levels of microRNAs miR-15a/16 play an important role in the disease. Here we investigate the effects of this microRNA on early steps of B cell development and the capacity of miR-15a-deficient hematopoietic stem cells (HSC) and B1 progenitor cells (B1P) to reproduce CLL-like phenotype both in vitro and in vivo. Our results demonstrate that both miR-15a deficient HSC and B1P cells are capable of repopulating irradiated recipients and produce higher numbers of B1 cells than sources with normal miR-15a/16 levels. Furthermore, induced pluripotent stem (iPS) cells derived for the first time from NZB mice, provided insights into the B cell differentiation roadblock inherent in this strain. In addition, exogenously delivered miR-15a into the NZB derived B cell line provided valuable clues into novel targets such as Mmp10 and Mt2. Our data supports the hypothesis that miR-15a/16 deficient stem cells and B1Ps experience a maturation blockage, which contributes to B1 cells bias in development. This work will help understand the role of miR-15a in early events of CLL and points to B1P cells as potential cells of origin for this incurable disease.
Subject(s)
Leukemia, Lymphocytic, Chronic, B-Cell/metabolism , MicroRNAs/metabolism , Animals , Apoptosis/drug effects , B-Lymphocytes/metabolism , Cell Differentiation , Cell Line, Tumor , Cell Separation , Disease Models, Animal , Leukemia, Lymphocytic, Chronic, B-Cell/genetics , Lymphocyte Activation , Mice , Mice, Inbred BALB C , Mice, Inbred DBA , Neoplastic Stem Cells/metabolism , Stem Cells/metabolismABSTRACT
This study examined the effect of hyaluronan (HA) molecular weight on immune response. HA with molecular weights ranging from the unitary disaccharide unit (400 Da) up to 1.7 × 10(6) Da and with very low endotoxin contamination level (less than 0.03 EU/mg) was used. Primary human monocyte/macrophage cultures were assayed for IL-1ß production under a variety of inflammatory conditions with or without HA. Under the highest inflammatory states, production of interleukin 1ß (IL-1ß) was suppressed in the presence of high molecular weight hyaluronan (HMW-HA) and in the presence of low molecular weight hyaluronan (LMW-HA) at mg/mL concentrations. There was variability in the sensitivity of the response to HA fragments with MW below 5000 Da at micromolar concentrations. There was variability in IL-1ß cytokine productions from donor to donor in unstimulated human cell cultures. This study supplements our previous published study that investigated the immunogenic effect of HA molecular weights using murine cell line RAW264.6, rat splenocytes, and rat adherent differentiated primary macrophages. These data support the hypothesis that if the amount of endotoxin is reduced to an extremely low level, LMW-HA may not directly provoke normal tissue macrophage-mediated inflammatory reactions.
