The hematopoietic system produces a large number of highly specialized cell types that are derived through a hierarchical differentiation process from a common stem cell population. miRNAs are ...critical players in orchestrating this differentiation. Here, we report the development and application of a high-throughput microfluidic real-time quantitative PCR (RT-qPCR) approach for generating global miRNA profiles for 27 phenotypically distinct cell populations isolated from normal adult mouse hematopoietic tissues. A total of 80,000 RT-qPCR assays were used to map the landscape of miRNA expression across the hematopoietic hierarchy, including rare progenitor and stem cell populations. We show that miRNA profiles allow for the direct inference of cell lineage relations and functional similarity. Our analysis reveals a close relatedness of the miRNA expression patterns in multipotent progenitors and stem cells, followed by a major reprogramming upon restriction of differentiation potential to a single lineage. The analysis of miRNA expression in single hematopoietic cells further demonstrates that miRNA expression is very tightly regulated within highly purified populations, underscoring the potential of single-cell miRNA profiling for assessing compartment heterogeneity.
Gene therapy as well as methods capable of returning cells to a pluripotent state (iPS) have enabled the correction of genetic deficiencies in syngenic adult progenitors, reducing the need for ...immunosuppression in cell therapy approaches. However, in diseases involving mutations that lead to the complete lack of a protein, such as Duchenne muscular dystrophy, the main immunogens leading to rejection of transplanted cells are the therapeutic proteins themselves. In these cases even iPS cells would not circumvent the need for immunosuppression, and alternative strategies must be developed. One such potential strategy seeks to induce immune tolerance using hematopoietic stem cells originated from the same donor or iPS line from which the therapeutic progenitors are derived. However, donor hematopoietic stem cells (HSCs) are available in limiting numbers and embryonic stem (ES) cell-derived HSCs engraft poorly in adults. While these limitations have been circumvented by ectopic expression of HOXB4, overexpression of this protein is associated with inefficient lymphoid reconstitution. Here we show that adult HSCs expanded with a NUP98-HOXA10hd fusion protein sustain long-term engraftment in immunologically mismatched recipients and generate normal numbers of lymphoid cells. In addition, NUP98-HOXA10hd-expanded cells induce functional immune tolerance to a subsequent transplant of myogenic progenitors immunologically matched with the transplanted HSCs.
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