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Abstract: FR-PO779

Cell Turnover Dynamics in the Human Kidney Using Radiocarbon Dating

Session Information

Category: Development, Stem Cells, and Regenerative Medicine

  • 500 Development, Stem Cells, and Regenerative Medicine

Authors

  • Jones, Christina, Karolinska Institutet, Huddinge, Sweden
  • Fu, Keng-Yeh, Karolinska Institutet, Huddinge, Sweden
  • Kiss, Endre, Karolinska Institutet, Huddinge, Sweden
  • Alkass, Kanar, Karolinska Institutet, Huddinge, Sweden
  • Kjellman, Anders, Karolinska Institutet, Huddinge, Sweden
  • Patrakka, Jaakko, Karolinska Institutet, Huddinge, Sweden
  • Bernard, Samuel, CNRS, Villeurbanne, France
  • Druid, Henrik, Karolinska Institutet, Huddinge, Sweden
  • Spalding, Kirsty, Karolinska Institutet, Huddinge, Sweden
Background

Kidney cell turnover is fundamental to maintain organ homeostasis and to replace lost cells in response to injury. This study aims to define regeneration in the human kidney and explore turnover kinetics in health and disease. Proximal tubular epithelial cells are known to turnover, however questions remain about the dynamics and source of replacement cells. Podocytes were traditionally considered irreplaceable, however reports of putative progenitors have sparked interest in podocyte regeneration. The novel method of radiocarbon dating DNA to determine human cell age (Spalding et al. 2005) has been used to answer fundamental questions about human regeneration in the brain, heart and adipose tissue. This study adapts the method to address these important questions in the kidney.

Methods

Human kidney nuclei sorting was developed for this study. The method is effective for whole kidney tissue and isolated glomerular fraction analyses, from either fresh or frozen tissue from both nephrectomy and postmortem sources. Podocyte, endothelial and proximal tubule nuclei were isolated, antibody-labeled and sorted by flow cytometry. This method yields over 10 million cell-type specific nuclei per sample with over 95% sort purity required for radiocarbon dating. DNA was extracted using carbon-clean methods and sent for carbon isotope analysis using accelerator mass spectrometry.

Results

Preliminary results from a cohort of 10 kidneys, collected from nephrectomy, indicates human proximal tubules have an average age of 13.3 years (±2.6), turning over at a rate of 7.7% per year. This was not impacted by patient age. Endothelial and podocyte dating is ongoing. DNA content analysis, via flow cytometric analysis of DAPI-labeled nuclei, indicates limited endoreduplication.

Conclusion

Radiocarbon dating has the potential to definitively answer questions regarding kidney regeneration in humans. Nuclei-based sorting provides an unbiased method to efficiently sort large numbers of cell-specific nuclei for a range of downstream analyses. Preliminary results of proximal tubules and ongoing successful sorts of podocytes and endothelial cells provides proof-of-principle that human kidney cell age can be determined. From physiological turnover, this study forms the basis for ongoing examination of kidney regeneration in pathology.

Funding

  • Commercial Support