Biomedical subjects

Steven B Bradfute

Publications and source records attributed to Steven B Bradfute.

5 recordsLinked to original sources

PubMed2005

Differential mRNA processing in hematopoietic stem cells.

Hematopoietic stem cells (HSCs) maintain tissue homeostasis by rapidly responding to environmental changes. Although this function is well understood, the molecular mechanisms governing this characteristic are largely unknown. We used a sequenced-based strategy to explore the role of both transcriptional and post-transcriptional regulation in HSC biology. We characterized the gene expression differences between HSCs, both quiescent and proliferating, and their differentiated progeny. This analysis revealed a large fraction of sequence tags aligned to intronic sequences, which we showed were derived from unspliced transcripts. A comparison of the biological properties of the observed spliced versus unspliced transcripts in HSCs showed that the unspliced transcripts were enriched in genes involved in DNA binding and RNA processing. In addition, levels of unspliced message decreased in a transcript-specific fashion after HSC activation in vivo. This change in unspliced transcript level coordinated with increases in gene expression of splicing machinery components. Combined, these results suggest that post-transcriptional regulation is important in HSC activation in vivo.

Animals↗

PubMed2005

Roles of Sca-1 in hematopoietic stem/progenitor cell function.

OBJECTIVE: This study was focused on studying the role of Sca-1 (Ly-6 A/E) in hematopoietic stem/progenitor cell self-renewal, activation, and lineage fate. MATERIALS AND METHODS: Sca-1(-/-) bone marrow cells were transplanted into wild-type recipient mice and assessed for self-renewal activity and lineage choice. In addition, Sca-1(-/-) mice were injected with 5-FU and Lin(-) cells were analyzed. Sca-1 was also overexpressed in mouse and human stem/progenitor cells to assess the effect of Sca-1 overexpression on stem/progenitor differentiation and proliferation. RESULTS: Self-renewal of Sca-1(-/-) HSC appeared to be normal, but lineage skewing was observed in B cells, NK cells, and granulocytes/macrophages derived from Sca-1(-/-) HSC. There was also a decrease in c-kit expression on activated Sca-1(-/-) progenitor cells. Overexpression of mouse Sca-1 decreased the in vitro myeloid activity of both mouse and human progenitors. CONCLUSION: These data indicate that Sca-1 plays a role in hematopoietic progenitor/stem cell lineage fate and c-kit expression. In addition, mouse Sca-1 overexpression affects human as well as mouse stem/progenitor cell activity, suggesting the possibility of a functional human Sca-1 homologue.

Animals↗

PubMed2004

Cardiac muscle plasticity in adult and embryo by heart-derived progenitor cells.

The evidence of cardiomyocyte proliferation in damaged heart implied cardiac regeneration might occur by resident or extra cardiac stem cells. However, the specification and origin of these cells remain unknown. Here, we report using fluorescence-activated cell sorting that cardiac progenitor cells resided in adult heart and colocalized with small capillary vessels, within the stem cell antigen (Sca-1) population expressing high telomerase activity. Notably, hematopoietic stem cells capable of efflux Hoechst 33342, termed side population cells, also were identified within the heart-derived cells. The cardiac progenitor cells (CD45(-)/CD34(-)) express neither cardiac muscle nor endothelial cell markers at an undifferentiated stage. The exposure of 5-azacytidine induced cardiac differentiation, which depends, in part, on Bmpr1a, a type IA receptor for bone morphogenetic protein (BMP). The capability of adult Sca1(+) cells to adopt a cardiac muscle in embryogenesis was substantiated by blastocyst injection, using progenitors from the adult hearts of transgenic mice that harbor a bacterial artificial chromosome expressing GFP via the Nkx-2.5 locus. Intravenously injected progenitors, shortly after ischemic/reperfusion, homed and functionally differentiated 3.5% of total left ventricle in the host myocardium. Differentiation included both fusion-independent and fusion-associated components, proved by the Cre/loxP donor/recipient system. Our studies suggest that endogenous cardiac progenitors reside in the adult heart, regenerate cardiomyocytes functionally, and integrate into the existing heart circuitry.

Adult↗

PubMed2003

Cardiac progenitor cells from adult myocardium: homing, differentiation, and fusion after infarction.

Potential repair by cell grafting or mobilizing endogenous cells holds particular attraction in heart disease, where the meager capacity for cardiomyocyte proliferation likely contributes to the irreversibility of heart failure. Whether cardiac progenitors exist in adult myocardium itself is unanswered, as is the question whether undifferentiated cardiac precursor cells merely fuse with preexisting myocytes. Here we report the existence of adult heart-derived cardiac progenitor cells expressing stem cell antigen-1. Initially, the cells express neither cardiac structural genes nor Nkx2.5 but differentiate in vitro in response to 5'-azacytidine, in part depending on Bmpr1a, a receptor for bone morphogenetic proteins. Given intravenously after ischemia/reperfusion, cardiac stem cell antigen 1 cells home to injured myocardium. By using a Cre/Lox donor/recipient pair (alphaMHC-Cre/R26R), differentiation was shown to occur roughly equally, with and without fusion to host cells.

Animals↗

PubMed2003

Adenoviral transduction of mouse hematopoietic stem cells.

Hematopoietic stem cells (HSC) are quiescent, self-renewing cells that can give rise to all blood cell lineages. HSC are an attractive target for gene therapy, due to their differentiation capacity and the number of diseases that result from abnormal HSC function. While human HSC have been shown to be transduced with adenoviral vectors, the adenoviral transduction of mouse HSC has not been extensively studied. We show here that a population of mouse bone marrow highly enriched for HSC (called side population, or SP, cells) can be transduced with adenovirus type 5 (Ad5) at a low multiplicity of infection. Transduced SP cells showed normal in vitro myeloid differentiation potential compared to mock-transduced SP cells. Transduced SP cells retained substantial but reduced in vivo long-term repopulating activity and contributed to all blood cell lineages. Ad5 transduction of mouse SP cells was dependent on coxsackie and adenovirus receptor (CAR), as an anti-CAR blocking antibody greatly reduced transduction. Therefore, adenoviral transduction of mouse HSC can be achieved without ablation of the hematopoietic repopulating activity.

Adenoviridae↗