FLT3-Ligand Alone Enables the Identification and Maintenance <i>in Vitro</i> of Viable Quiescent Human Fetal Liver Hematopoietic Stem Cells with Maintenance of Their Function
Notice bibliographique
Résumé
Cells with sustained multi-lineage blood cell regenerative potential are referred to as hematopoietic stem cells (HSCs). Current findings indicate that they are responsible for lifelong blood production, are first detected within the first month of development in humans and are largely created prior to birth after which they expand their numbers in response to physiological demands for normal or enhanced blood cell output requirements. Interestingly, a number of the intrinsically determined functional properties of HSCs also change after birth. These include an apparent decline in their self-renewal potential. Thus, for example, in humans as in mice, cells with long-term (&gt;6 month) HSC regenerative properties present in the developing fetal liver (FL) are a source of HSCs that possess a much higher in vivo regenerative capability than those from older donor sources, such as adult bone marrow or even cord blood (CB). Accordingly, it has been of longstanding interest to better understand the molecular regulation of this high regenerative capacity prevalent in fetal HSCs for potential future therapeutic as well as scientific exploitation. Here, we describe the results of experiments designed to answer the hypothesis that human FL HSCs with human-relevant self-renewal properties can be isolated as a quiescent CD49f+ subset of the GPI80+CD90+CD38-CD45RA-CD34+CD45+ population following their incubation in standard serum-free culture medium supplemented with FLT3-ligand (FLT3-L) alone. Initial experiments showed expression of the CD49f integrin on first trimester hFL cells selectively depleted cells able to produce colonies of granulocytes, macrophages or erythroid cells in standard 2-week methylcellulose cultures containing SCF, GM-CSF, IL6, IL3 and EPO. Conversely, expression of the CD49f integrin selectively enriched for cells with 12-week output capabilities in both growth factor (GF)-supplemented stromal co-cultures and in sublethally irradiated, transplanted immunodeficient NOD-Rag1 -/-IL2Rγc -/- W 41/41 (NRG-W) mice. Initial experiments designed to test the effect of multiple GF and small molecule additives on the maintenance over a 7-day period of this in vivo regenerative ability of the input FL HSC confirmed GPI80 expression to be a continuing positive selective phenotype. In addition, the result of transplant experiments showed that a 2-day incubation in FLT3-L alone maintained the 12-week serially transplantable activity of the HSCs (12-weeks/cycle) as fully equivalent to the unmanipulated input cells and significantly superior (P&lt;0.05) to FLT3-L+IL3+SF (3GF) with or without addition of UM171, stemregenin, or eltrombopag. Interestingly, in vitro monitoring of GPI80+ cells showed FLT3-L alone maintained the survival of only 20% of the input GPI80+ cells compared to any of the 3GF-based conditions. In addition, the time to complete a first division and subsequent divisions of the input cells was delayed and prolonged, respectively, in the FLT3-L versus the 3GF conditions. Subsequent 7-day suspension cultures and 6-week GF-supplemented stromal co-cultures experiments have confirmed the existence of a G0 population within the HSC-enriched subset of human FL cells that best maintains their growth potential in FLT3-L alone. Together, these results demonstrate CD49f expression to be a pervasive marker of human HSCs throughout development and reveal the importance of different GF conditions to support the maintenance of viability and retention of self-renewal capability of human fetal HSCs in contrast to those required to activate/support a rapid initiation of cell division. These findings set the stage for future development of strategies to exploit human FL cells therapeutically and may also be critical to designing conditions that will best support the ex vivo maintenance of HSCs at and after birth.
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Comment cette classification a été obtenuedéplier
Prédiction distillée sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Apprise à partir de 10 348 étiquettes directes de Codex et de 10 348 étiquettes directes de Gemma. Le mode candidate est l'union des têtes enseignantes seuillées; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont ni des étiquettes humaines ni des étiquettes directes de modèles de pointe.
Scores Codex et Gemma par catégorie
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,000 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule tête enseignante, pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».