Constitutive Cardiomyocyte Proliferation in the Postnatal Leopard Gecko ( <i>Eublepharis macularius</i> )
Bibliographic record
Abstract
Although historically considered to be mitotically inactive, mammalian cardiac muscle cells (cardiomyocytes) are now widely viewed as being capable of at least low levels of homeostatic renewal throughout adulthood. Emerging evidence indicates that the extent to which cardiomyocytes can spontaneously re‐enter the cell cycle correlates with the capacity for cardiac self‐repair and regeneration. Therefore, proliferation rates may offer a predictive tool for investigating the regenerative potential of a species. Here we explore homeostatic cardiomyocyte proliferation in a representative reptile, the leopard gecko ( Eublepharis macularius ) . The gecko heart is characterized by a trabeculated, spongy‐like ventricular lumen. This architecture is also seen in species capable of cardiac regeneration (such as zebrafish), as it provides an increased surface area for diffusion with a decreased reliance on coronary circulation. To assess cardiac cell proliferation, we employed a short duration bromodeoxyurdine (BrdU) pulse‐chase experiment (2 day pulse, 7 day chase), and immunostained for the S phase marker proliferating cell nuclear antigen (PCNA) and the mitotic marker phosphorylated histone H3 (pHH3). We determined that cardiac cells of the gecko heart continually proliferate, even into adulthood. Using double immunofluorescence, we then co‐localized the cardiomyocyte marker myosin heavy chain (MHC) with each of PCNA and pHH3. We found that ~10% of cardiomyocytes have entered the synthesis phase (MHC+/PCNA+), while ~0.5% are mitotically active (MHC+/pHH3+). Next, we performed a long duration BrdU pulse‐chase experiment (7 day pulse, 140 day chase). Unexpectedly, we observed long‐term label‐retaining (= slow cycling) cells throughout the ventricular myocardium. These data suggest that the gecko heart contains populations of both constitutively active and comparatively quiescent cells. Our results combined with a trabeculated ventricular architecture point towards the gecko as an excellent candidate to study cardiac self‐repair and regeneration. Support or Funding Information Natural Sciences and Engineering Research Council (NSERC) Discovery Grant 400358
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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) | 0.001 | 0.000 |
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".