Assessment of the Developmental Potential of Rat Embryonic Stem-Like (ES-Like) Cells by Diploid and Tetraploid Embryo Aggregation Confirms Their In Vivo Multipotency.
Notice bibliographique
Résumé
The rat is a model of major importance to biomedical research. The existence of genuine embryonic stem (ES) cells in the rat is highly anticipated and desirable because it would allow gene-targeting technology (i.e. knockout) in this species and permit further elucidation of gene function. At present, this powerful technology is only available in mice, and in fact, derivation of ES cells in the rat has remained elusive for many years. However, recently we have demonstrated that rat ES-like cells could be efficiently derived and cultured in vitro for extended periods while maintaining pluripotent cell markers such as alkaline phosphatase, stage-specific embryonic antigen-1, and both mRNA and protein expression of the transcription factor Oct4. These rat ES-like cells were transfected with a reporter gene, injected into diploid host blastocysts, and transferred to pseudopregnant females. The results obtained demonstrated that rat ES-like cells can contribute to multiple developing extraembryonic tissues of both midgestation and term fetuses. However, their in vivo contribution appears limited only to the extraembryonic tissues, as their presence in tissues of the embryo proper could not be detected. We hypothesized that rat ES-like cells could contribute to a wider range of tissues if host embryos at an earlier developmental stage than the blastocyst were used for testing the developmental potential. To this end, we adapted two assays frequently used in mice to generate embryonic chimeras, that is, diploid and tetraploid aggregation. The specific objectives were to: 1) develop a robust in vitro embryo culture system 2) generate tetraploid embryos 3) carry out diploid (2n<->ES) and tetraploid (4n<->ES) aggregations and compare the development rates to the morula \ blastocyst stage 4) determine the implantation rates following embryo transfer and 5) examine the contribution of the rat ES-like cells to resulting fetuses. The results obtained showed efficient development of control embryos to the morula \ blastocyst stage, indicating an efficient culture system. Tetraploid embryos were very successfully generated. No difference was observed in the rates of development to the morula \ blastocyst stage between controls, 2n<->ES, and 4n<->ES embryo aggregations. The implantation rates were similar in all groups, suggesting that the presence of rat ES-like cells in aggregates does not adversely affect implantation following embryo transfer. Importantly, these rat ES-like cells were found to have contributed in vivo to the extraembryonic tissues at midgestation, confirming similar results obtained previously using blastocyst injection. In conclusion, for the first time, we have shown that embryo aggregations are suitable to determine the developmental potential of rat ES-like cells, suggesting that such aggregations can be used to screen for pluripotent rat ES-like cell lines. This research therefore constitutes another step forward in the search for genuine rat ES cells. Supported by a Natural Sciences and Engineering Research Council of Canada Industrial Postgraduate Scholarship to S.-P. Demers and by Clonagen inc.
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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 | 0,001 |
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 ».