Mir-125a Confers Multi-Lineage Long-Term Repopulating Stem Cell Activity to Human Hematopoietic Committed Progenitors
Bibliographic record
Abstract
Abstract Recent studies have shown that several miRNA are differentially expressed in hematopoietic stem cells (HSC) and involved in regulating self-renewal, pointing to a new axis of epigenetic control of HSC function. Murine studies have documented a role for miR-125a in regulating HSC as miR-125a enforced expression augments self-renewal. We examined whether these attributes are evolutionarily conserved within human hematopoiesis. Lentiviral vectors over-expressing miR-125a (miR-125OE) were developed and HSC function was investigated using xenotransplantation of CD34+ CD38- human umbilical cord blood (CB) hematopoietic stem and progenitor cells (HSPCs). miR-125OE resulted in significantly increased human bone marrow (BM) chimerism at 12 and 24 weeks post-transplantation and splenomegaly. Within enlarged spleens, there were significantly increased proportions of CD34+CD19+CD10+CD20-B lymphoid cells suggesting a partial B cell differentiation block at the pro-B cell stage. In the BM, CD41+ megakaryocytes, GlyA+ erythroid and CD3+ T cell populations were significantly expanded. Within the primitive compartment, multi-lymphoid progenitors (MLP) were massively expanded by 12 weeks, followed by a combined reduction of immuno-phenotypic HSC and multi-potent progenitors (MPP) by 24 weeks. Given this loss of immuno-phenotypic HSC, we wondered whether stem cell function was compromised in vivo. Secondary transplantation with limiting dilution (LDA) revealed that stem cell frequencies were increased by 4.5 fold in miR-125OE recipients. Using lentivirus sponge-mediated inhibition of miR-125 (miR-125KD) in CD34+CD38-human CB, we were able to directly link these effects to miR-125: B cells increased at the expense of T cells; immuno-phenotypic HSC increased with a concomitant loss of MLP; and functional HSC were decreased by 2.5 fold using secondary LDA assays. Together, these data strongly suggest that miR-125a expression levels regulate human HSC self-renewal and lineage commitment. Since HSC frequency increased so substantially upon miR-125OE, we asked whether more committed cell populations might also be endowed with enhanced self-renewal. Highly purified populations of HSC, MPP and MLP and CD34+CD38+ committed progenitors were transduced and transplanted cells into xenografts. Unexpectedly, miR-125OE transduced CD34+CD38+ progenitors produced a substantial graft after 12 weeks. Control transduced CD34+CD38+ cells did not engraft and only control transduced HSC generated a disseminating graft in recipient mice. miR-125OE transduced HSC and MPP generated robust engraftment, while MLP did not. In all cases, xenografts generated by CD34+CD38+ and MPP transduced with miR-125OE showed multi-lineage repopulation. Moreover, the miR-125OE grafts from CD34+CD38+ and MPP recipients were durable as secondary transplantation generated multi-lineage grafts for at least 20 weeks in 5/7 and 6/10 recipients, respectively; no control transduced groups generated secondary grafts. Thus, the enhancement of self-renewal by enforced expression of miR-125a occurs not only in HSC, but also in MPP and to an as yet unidentified subpopulation within the CD34+38+ committed progenitor compartment. Using protein mass spectrometry, we identified and validated a miR-125a target network in CD34+ CB that normally functions to restrain self-renewal in more committed progenitors. Together, our data suggest that increased miR-125a expression can endow an HSC-like program upon a selected set of non-self-renewing hematopoietic progenitors. Our findings offer the innovative potential to use MPP with enhanced self-renewal to augment limited sources of HSC to improve clinical outcomes. Disclosures No relevant conflicts of interest to declare.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".