Stem Cell Antigen-1 Expression Marks a Population of Mouse Ovarian Surface Epithelial Cells with Enhanced Stem/Progenitor Cell Characteristics.
Bibliographic record
Abstract
Stem cell antigen-1 (Sca-1) is the most common marker used to enrich for murine hematopoietic stem cells and with the realization that many stem cell types share conserved biochemical pathways, Sca-1 has become an attractive stem cell marker candidate for identifying a variety of tissue specific stem/progenitor cells (referred to as stem cells). The mouse ovarian surface epithelium (OSE) is a single layer of poorly differentiated cells that covers the surface of the ovary and is ruptured during ovulation. The remaining OSE cells surrounding the ovulatory wound then proliferate rapidly to regenerate the surface layer of cells. Since rapid healing also occurs in other epithelial tissues where stem cells are the source of proliferating cells, we propose that the OSE contains a Sca-1+ stem cell population which gives rise to the rapidly proliferating cells that close ovulatory wounds. Using flow cytometry we have shown that the OSE contains a side population of cells (SP, 3% of all OSE) that rapidly effluxes Hoechst 33342, a characteristic that is frequently found in stem cells in other tissues. Since SP analysis typically identifies a heterogeneous population of cells we used quantitative RT-PCR to compare expression levels of specific stem cell markers in SP versus non-SP cells. We have determined that OSE SP cells express 5-fold higher levels of Sca-1 mRNA and 3-fold higher levels of the stem cell marker CD117 (KIT) mRNA when compared to non-SP cells. These results indicate that both Sca-1 and CD117 are potential candidate stem cell markers in the OSE. To compare growth potential and the ability of the Sca-1+/- and CD117+/- OSE cells to self-renew in vitro, spheroid generating efficiency was assessed. Using magnet assisted cell sorting, we divided OSE cells into Sca-1+ and Sca-1- fractions (0.89% and 99.1% respectively) and CD117+ and CD117- fractions (2.3% and 97.7% respectively) and compared sphere generating efficiency in methylcellulose. The Sca-1+ fraction yielded significantly more spheres (p<0.001) compared to all other fractions (% sphere generating efficiency after 28 days: Sca-1+ 0.37; Sca-1- 0.020; CD117+ 0.028; CD117- 0.013) suggesting that it is a good marker for OSE stem cell enrichment. The sphere generating efficiencies of the CD117+ and CD117- OSE fractions (0.028% vs. 0.013%) was not statistically different indicating that CD117 may not be a useful marker for isolating a population of OSE cells with enhanced stem cell characteristics. The incidence of sphere formation can be increased by at least two factors highly expressed at ovulation (TGF-beta and LIF) indicating that ovulation may influence the OSE stem cell population. Currently, we are performing in vivo experiments to determine if Sca-1+ OSE have the ability to repopulate the surface of the ovary. Preliminary results show that only the Sca-1+ OSE are able to attach to the surface of the ovary and survive for at least 5 weeks which indicates that this fraction may be enriched for OSE stem cells. These results indicate that the OSE contains a population of Sca-1+ cells with enhanced stem cell properties (inclusion in SP, enhanced sphere generating efficiency, ability to attach and survive on the surface of the ovary). Interestingly, we have also found that factors highly expressed in follicular fluid at the time of ovulation may influence OSE stem cell activity thereby driving ovulatory wound healing. (platform)
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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 | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
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".