Generation of Megakaryocytes from Human Embryonic Stem Cells.
Bibliographic record
Abstract
Abstract The ability to generate multiple cell types from human embryonic stem cells (hESC) in culture offers an unprecedented opportunity to produce an unlimited supply of cells for research and clinical purposes. Megakaryocytes comprise only 0.02–0.05% of the nucleated cell population in the bone marrow, thus making them a difficult cell to isolate and study. The ES cell technology provides a resource for generating megakaryocyte progenitors for in vitro and in vivo analyses. For this approach to be successful, reproducible differentiation schemes that generate sufficient numbers of cells are necessary. With an embryoid body (EB)-based protocol, in serum-free media we are able to generate hematopoietic populations with megakaryocyte potential from two different hESC lines; H1 and HES2. Using CD41 as an early marker of definitive hematopoiesis, we found that 4 to 12% of the day 11–12 EB population expressed high levels of the marker (CD41Hi) whereas 10 to 20% expressed low levels of the marker (CD41Lo). Cells from the CD41Hi but not the CD41Lo population expressed the megakaryocyte marker GPIb. To further analyze these populations, both were isolated from day 12 EBs by cell sorting and cultured in media containing TPO and SCF. Following several days in culture, the CD41Hi population expressed increasing levels of GPIb, as determined by flow cytometry and real time PCR. PF4 was detected in the sorted CD41Hi population and levels increased 10-fold following culture. These cells also adhered to fibrinogen and collagen and stained positive for von Willebrand factor (vWF) and P-selectin. Following activation by PAR1, the cells bound soluble fibrinogen and expressed P-selectin on their surface. Few to no progenitors were detected in the CD41Hi fraction by colony assays suggesting that this population contained cells that were already committed to the megakaryocyte lineage. Incubation of the CD41Lo population of cells in the presence of TPO resulted in 70–80% of the cells expressing increased levels of CD41 and GPIb. Immunostaining revealed vWF and P-selectin expression following adhesion of the cells to fibrinogen and collagen. Both fibrinogen binding and P-selectin surface expression were detected following activation with PAR1. Quantitative PCR analysis demonstrated low levels of PF4 message in the sorted population with an increase of 3-fold following incubation in the presence of TPO. Progenitor cells were detected in colony assays suggesting that this population of cells contained megakaryocyte-like progenitors. Taken together, these finding demonstrate the efficient and reproducible generation of megakaryocytes from hESC using a serum-free EB protocol.
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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 | 0.001 |
| Insufficient payload (model declined to judge) | 0.003 | 0.002 |
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".