How would you define the regenerative potential of a tissue/organ?

Dear stem cell biologists and bioinformaticians: I’ve got a pretty serious question for you. How would you define and quantify the native (endogeneous, in-built) regenerative potential of a tissue/organ or more generally of a specially localized functional cell population in the human body? In the literature the term “regenerative potential” of a tissue is often used concerning the response to damage and repair due to the contribution of the tissue-specific resident stem cell niche or from the circulation, but I haven’t found any strict and quantitative concept and definition yet. If you do please inform me. A working operational definition (update: of a regenerative potential of a tissue/organ) designed to model a conceptual definition could be the basic building block of a whole body regeneration model, which is needed for any attempt to launch systemic regenerative medicine.

So here is my initial offer:

Let us assume that we calculated the following cell numbers of a tissue/organ with some method (stereology, fluorescence activated cell sorter, theorethical calculation based on other measurements and data):

- number of differentiated functional cells

- number of tissue, organ and lineage specific endogenous stem cells

- number of tissue, organ specific progenitor (or transit amplifying cells TACs) cells.

Based on the estimated proportion of stem cell/differentiated cells or TACs/differentiated cells in a defined tissue or organ I’d like to introduce the tissue and organ specific theoretical and practical Regenerative Potential.

I define the Theorethical Regenerative Potential of a tissue or organ as follows: the ratio of quiscent self-renewing stem cells in a stem cell niche/differentiated cells in a tissue or organ. (Or we can use all cells= differentiated+stem+TACs as a denominator.) Continue reading

Best paper on stem cells and ageing by Thomas Rando: Figure 1

One of the promo material of last December Cambridge Embryonic Stem Cell Symposium was the Nature Insight: Stem Cells which was a supplement in Nature Vol. 441, No. 7097 pp1059-1102 from June , 2006. In it I found the best, brilliantly argumented and conceptualized, data-rich paper of Thomas Rando from Stanford University on Stem cells, ageing and the quest for immortality. I plan to introduce the thoughts of the paper in great details in future posts of Pimm. For today I just copy here Fig. 1: Tissue heterogeneity and stem-cell functionality for homeostasis and repair and the legend because this is the essential starting point of systemic regenerative medicine. Take an hour to think about it.

randofig1

You can also discuss the paper here, or comment all the reviews of Nature Insight: Stem Cells on a special Nature blog-like surface.