Something about Stem Cells

I wish this post might be a very short introduction to the basic terminology of the field (i.e. words you can find in popular science magazines; this does not pretend to be conprehensive or complete anyway). I hope this will be either a trigger of further questions and a link between Mario’s (past) and Mathias’ (next) discussions. I provide interesting links below for those who wish to have detailed reviews on this topic.

One year before getting his MD (at solely 20 years) Giulio Bizzozero (1846-1901) provided evidences supporting the hemopoietic role of bone marrow – this was the first of an impressive list of experimental achievements (including the association of platelets with hemostasis) which crowned Bizzozero as one of the fathers of scientific medicine in Italy. Being involved in the teaching of histology and (experimental) pathology, he suggested one classification of the cells that reside in animal tissues: these were supposed to be labile (it. labili), stable (it. stabili) and permanent (it. perenni). Although its simplistic form, he recognized through this classification one essential biological truth: that is, the degree of regenerative capacity among different tissues varies greatly and can occasionally be triggered by specific stimuli (e.g. hepatocytes –stable cells- can start dividing upon hepatectomy in order to eventually reconstitute a [fully] functional organ). This intrinsic regenerative capacity is actually due to special cells called stem cells. It indirectly refers to the stamen –the reproductive organ in plants- and then to fertility, which is the capacity to generate. This is the first and most important concept to keep in mind: stem cells are able to generate more differentiated (i.e. endowed with specific physiological function) cells through a process of sequential change in the expression of [their] genes. This process is in turn due to exposure to tissue-related growth and differentiating factors and take place both in fetal and –although differently- in adult life. Isolated stem cells (or supposed to be stem cells) can be defined experimentally by using surface molecular markers (i.e. molecules expressed on their plasma membrane) and challenging through a variety of assays their capacity to multiplicate indefinitely or to differentiate. The capacity to generate one or more differentiated cell types is called potency and –according to the degree of potency- stem cells can be considered to be pluri-potent (e.g. able to generate cell types belonging to all three germ layers) or multi-potent (progenitors or precursors; think of hematopoietic stem cells [HSCs]). The ‘most potent’ (say toti-potent) array of stem cells is the embryo itself; indeed, one general distinction is made between embryonic stem cells (derived from different anatomical structures of the developing embryo and the fetus) and adult stem cells, which usually reside in specialized niches (a homely place in which the stemness is uniquely preserved) in their tissue of destination. The source of stem cells for research and/or curative intents is argument of ethical, social and scientific debate and much can be found either in the web and books on it (further issues will be developed in the blog, too). The most intriguing observation –I guess- is that wether what I have briefly described seems a one-way process, actually it is not exactly the case. Manipulation of adult differentiated cells (e.g. fibroblast in the paper by Szavo et al.; see “The plasticity of stem cells”) is a powerful tool to induce genetic reprogramming of cells toward a different phenotipyc identity from the original one. Anyway, further experimental proof (especially long-term monitoring of induced phenotype) is needed in order to apply this tricky biological game to cure disases. As we wait for that proof, the field of regenerative medicine grows prolific and promise to approach a variety of pathologic conditions. In spite of Bizzozero’s classification of cell types (which was insightful and innovative at the time), the harnessing of the physiologic potential for auto-reparation of the organism to improve our own condition –together with its corollary pro’s and con’s- is a necessary step, I guess.

1. Here a very well-done web pages dedicated to basic knowledge about stem cells:

http://stemcells.nih.gov/info/basics/

www.medicalnewstoday.com/info/stem_cell/

2. Paolo Mazzarello, Alessandro L. Calligaro & Alberto Calligaro (2001) Timeline: Giulio Bizzozero: a pioneer of cell biology Nature Reviews Molecular Cell Biology 2, 776-784.

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One Response to Something about Stem Cells

  1. Stefi says:

    I agree Davide, regenerative medicine grows prolific.
    I’d like to mention just one of the latest success, reported in 2008 by “The Lancet”, one of the most eminent international scientific journal. A group of researchers from Spain, UK and Italy successfully transplanted a tissue-engineered airway in a 30-years-old woman with a end-stage broncomalachia. This woman was going to lose her normal airway. The scientists found the way to rebuild the trachea with mesenchymal stem-cell-derived chondrocytes obtained from the woman herself. The trachea was then transplanted and it prooved to be functional. Moreover, thanks to the adult stem cells derived form the patient itself, the woman didn’t need to be on immunosuppressive drugs, which are debilitating for transplanted patients.
    And I’d like o underline that the first author of the paper….is ITALIAN!

    A similar transplant has been done on a 10-years-old boy in UK, by the same team, in March 2010.
    So…it sounds that the future of regenerative medicine is now!

    Links:
    http://www.thelancet.com/journals/lancet/article/PIIS0140-6736%2808%2961598-6/fulltext

    http://news.bbc.co.uk/2/hi/health/8576493.stm

    Bye and good luck
    Stefi

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