Biomedical subjects

Hongfang Wang

Publications and source records attributed to Hongfang Wang.

4 recordsLinked to original sources

PubMed2006

Distinct roles of IL-7 and stem cell factor in the OP9-DL1 T-cell differentiation culture system.

OBJECTIVE: The OP9-DL1 culture system is an in vitro model for T-cell development in which activation of the Notch pathway by Delta-like 1 promotes differentiation of mature T cells from progenitors. The roles of specific cytokines in this culture system have not been well defined, and controversy regarding the role of IL-7 has recently emerged. We examined the roles played by IL-7, Flt3 ligand, and stem cell factor (SCF) in differentiation of adult bone marrow cells in the OP9-DL1 culture system. METHODS: Hematopoietic progenitor cells isolated from mouse bone marrow were cultured with OP9 or OP9-DL1 stromal cells and evaluated for T and B lymphocyte differentiation using immunofluorescent staining. RESULTS: IL-7 provided both survival/proliferation and differentiation signals in a dose-dependent manner. T-cell development from the CD4/CD8 double-negative (DN) stage to the CD4/CD8 double-positive (DP) stage required IL-7 provided by the stromal cells, while differentiation from the DP to the CD8 single-positive (SP) stage required addition of exogenous IL-7. SCF favored the proliferation of DN lymphoid progenitors and inhibited differentiation to the DP stage in a dose-dependent manner. Conversely, blocking the function of SCF expressed endogenously by OP9-DL1 cells inhibited proliferation of lymphoid progenitors and accelerated T-lineage differentiation. Flt3 ligand promoted proliferation without affecting differentiation. CONCLUSION: These results validate the OP9-DL1 model for the analysis of T-cell development from bone marrow-derived progenitor cells, and demonstrate specific roles of SCF, IL-7, and Flt3L in promoting efficient T-lineage differentiation.

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PubMed2005

Lymphoid potential of primitive bone marrow progenitors evaluated in vitro.

Bone marrow contains a heterogeneous mixture of mature and maturing precursors of blood cells, progenitor cells for myeloid and lymphoid lineages, and hematopoietic and mesenchymal stem cells. The differentiation potential of these different stem, progenitor, and precursor populations can be evaluated by using transplantation and cell culture assays. In this study, we used a stromal cell co-culture system to evaluate the B and T lineage potential of different subsets of mouse bone marrow. We enriched hematopoietic stem (Lin(-)Sca-1(+)c-kit(+)Thy1.1(low) [Thy1.1(low)]) cells and lymphoid progenitor (Lin(-)Sca-1(+)c-kit(+)Thy1.1(-) [Thy1.1(-)]) cells from mouse bone marrow and co-cultured these populations with OP9 or OP9-DL1 stromal cell lines. Development of the B and T lineages was evaluated over time. Both populations gave rise to B and T cells but with different kinetics. Thy1.1(-) lymphoid progenitors gave rise to B and T lineage cells earlier than did Thy1.1(low) stem cells; and at any given time, percentages of differentiating B and T cells were higher in Thy1.1(-) cultures than in Thy1.1(low) cultures. We also compared the lineage potential of Thy-1.1(-) lymphoid progenitors with that of the recently described common lymphoid progenitor 2 (isolated as Lin(-)Sca-1(+)c-kit(-)Thy1.1(-)B220(+) cells [B220(+)]). B220(+) cells produced B lineage progeny in OP9 cultures more rapidly than did Thy1.1(-) cells and produced higher percentages of differentiating T cells in OP9-DL1 cultures. These studies demonstrate the utility of the OP9 and OP9-DL1 co-culture systems for evaluation of lymphoid lineage potential and for determining the relative position of specific bone marrow populations within the hematopoietic hierarchy.

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PubMed2003

L-selectin defines a bone marrow analog to the thymic early T-lineage progenitor.

The recent description of an early T-lineage progenitor (ETP) population in adult mouse thymus implies the presence of a bone marrow predecessor that has not yet been identified. Here we describe a Lin(Neg) Sca-1(Pos) c-kit(Hi) Thy-1.1(Neg) L-selectin(Pos) adult mouse bone marrow population that resembles the thymic ETP in both antigen expression phenotype and posttransplantation lineage potential. These cells produce wavelike kinetics of thymic seeding and reconstitute the irradiated thymus with kinetics comparable to a thymocyte graft after intravenous transplantation. Transient B-lineage reconstitution is also observed, but little myeloid potential can be detected in transplant experiments. A second subset of progenitors is L-selectin(Neg) and is highly enriched for rapid and persistent T- and B-lineage potential, as well as some myeloid potential. L-selectin (CD62L) is therefore an effective marker for separating lymphoid progenitors from myeloid progenitors and hematopoietic stem cells in mouse bone marrow.

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PubMed2003

Aspects of early lymphoid commitment.

In the past year, significant progress has been realized in understanding the molecular underpinnings of commitment to the lymphoid pathways of differentiation. Several new approaches of phenotypic identification have revealed early stages of lymphoid commitment, and recent new studies have provided additional information regarding the central role of Notch receptors and their ligands and modulators as important regulators of the T/B lineage decision. The identification of PU.1 as a transcriptional regulator of the interleukin-7 receptor has established one mechanism by which PU.1 regulates lymphoid development. Finally, two studies have provided insight into the mechanisms of thymic selection. Still to be resolved, however, is the question of whether the T lineage is specified in bone marrow or only after migration of multipotent progenitors to the thymus.

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