Age Related Changes in Hoechst 33342 Efflux Dynamics and Side Population Phenotype in Murine Bone Marrow.
Notice bibliographique
Résumé
Abstract The mechanisms underlying the aging of the hematopoietic stem cell (HSC) compartment remain poorly understood. The ATP-binding cassette cell surface transport protein, ABCG2, has been identified as the transporter responsible for Hoechst 33342 (Hst) efflux in primitive stem cells and its expression is associated with the side population (SP) phenotype in both murine and human bone marrow (BM). ABCG2 expression and Hst efflux activity is highest in those cells with the greatest repopulating potential and is progressively downregulated during differentiation. The substrate profile of ABCG2, which includes a number of antineoplastic drugs, protoporphyrin IX and the chlorophyll breakdown product pheophorbide, suggest that ABCG2 transporters may function to protect stem cells from cytotoxic insults, a function which may be of great importance in stem cell maintenance. Amongst laboratory mice, the C57BL/6 strain is the longest lived and appears to accumulate HSC’s with age as assessed by both phenotype and colony forming assays. While the phenotypic features of the SP profile have been well characterized in both humans and young mice, little is known of the Hst efflux dynamics or phenotype of the SP profile in old and very old C57BL/6 mice. In order to further characterize the SP profile in old mice, whole BM was extracted from the femurs, tibiae, pelvis and thoracolumbar vertebral bodies of young (9–13 week) and old (95–108 week) C57BL/6 (Ly5.1) mice. Cells were stained with 5μg/ml Hst followed by staining with a combination of CD45.1 FITC, Sca1 PE, c-kit APC, CD34 FITC, biotinylated CD34 and lineage markers and strep PE-Texas Red. In addition, serial sampling of Hst incubated cells was performed to assess Hst efflux activity at 20 mins incubation through to 100mins. Six-color flow analysis was performed on a FACS Vantage™ (BD) cytometer and data analyzed using FlowJo™ software. Results show a marked increase in cells with an SP phenotype in old vs young mice (mean±SD 1.85%±0.88 vs 0.15%±0.09) which were more highly enriched for CD34-Sca1+ckit+ (22.2%±8.65 vs 8.89%±6.7) cells. Subdividing the SP profile into four regions (R1 to R4) from highest to lowest Hst efflux activity revealed that in old mice, SP cells with the highest Hst efflux activity were almost exclusively of a CD34-Sca1+ckit+ phenotype (82.3%±14.0 vs 11.5%±7.8), with a decreasing proportion of these cells represented throughout the remaining SP tail, though a significant proportion of cells within R4 remain CD34-Sca1+ckit+ (15.3%±7.83 vs 4.19±3.01). Similar patterns have been observed in both whole and lineage depleted BM. In addition, BM cells from old C57BL/6 mice show prolonged Hst efflux activity with an increase in cells in the SP gate at 100 mins (1.51%±0.50 vs 0.10%±0.06). We conclude that in old C57Bl/6 mice, cells accumulate which have the capacity to efflux Hst in agreement with previous reports of an increase in HSC number with age in this mouse strain.
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| 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 | 0,001 | 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) | 0,001 | 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 source (Gemma direct ou Codex distillé), 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 ».