Science : "Stem-cell" et régénération cellulaire


Cette semaine dans Nature, 4 articles, voire 5 sur un même sujet. Ce qui est plus qu'exceptionnel. Ainsi que 3 éditoriaux.

En fait, je n'ai jamais vu ça.

Le thème : les cellules souches (je pense que c'est la meilleur traduction), ou Stem Cells. C'est à dire des cellules qui peuvent évoluer et donc se différencier en n'importe quelle lignée cellulaire.

Le premier article fait le point sur les moyens employés pour éviter le rejet par les patients de ces stem cells :

Nature. 2008 May 15;453(7193):330-7.

Tolerance strategies for stem-cell-based therapies.

Chidgey AP, Layton D, Trounson A, Boyd RL.

There is much interest in using embryonic stem cells to regenerate tissues and organs. For this approach to succeed, these stem cells or their derivatives must engraft in patients over the long term. Unless a cell transplant is derived from the patient's own cells, however, the cells will be targeted for rejection by the immune system. Although standard methods for suppressing the immune system achieve some success, rejection of the transplant is inevitable. Emerging approaches to address this issue include 're-educating' the immune system to induce tolerance to foreign cells and reducing the immune targeting of the transplant by administering 'self stem cells' instead of foreign cells, but each of these approaches has associated challenges.

Le deuxième article fait le point sur l'utilisation dans les pathologies cardiaques de stem-cells non pas embyonnaires mais adultes

Nature. 2008 May 15;453(7193):322-9.

Stem-cell-based therapy and lessons from the heart.

Passier R, van Laake LW, Mummery CL.

The potential usefulness of human embryonic stem cells for therapy derives from their ability to form any cell in the body. This potential has been used to justify intensive research despite some ethical concerns. In parallel, scientists have searched for adult stem cells that can be used as an alternative to embryonic cells, and, for the heart at least, these efforts have led to promising results. However, most adult cardiomyocytes are unable to divide and form new cardiomyocytes and would therefore be unable to replace those lost as a result of disease. Basic questions - for example, whether cardiomyocyte replacement or alternatives, such as providing the damaged heart with new blood vessels or growth factors to activate resident stem cells, are the best approach - remain to be fully addressed. Despite this, preclinical studies on cardiomyocyte transplantation in animals and the first clinical trials with adult stem cells have recently been published with mixed results.

Les deux derniers articles sont plus techniques (imagerie et chimie).

Et enfin, un cinquième article, un peu plus généraliste, aborde les possibilités de la médecine "régénérative". Et j'avoue que je me demande si les auteurs n'ont pas raison quand ils déclarent que le bond en avant que cela peut constituer est à rapprocher de ce que les antibiotiques ont pu apporter au 20ème siècle.

Nature. 2008 May 15;453(7193):314-21.

Wound repair and regeneration.

Gurtner GC, Werner S, Barrandon Y, Longaker MT.

The repair of wounds is one of the most complex biological processes that occur during human life. After an injury, multiple biological pathways immediately become activated and are synchronized to respond. In human adults, the wound repair process commonly leads to a non-functioning mass of fibrotic tissue known as a scar. By contrast, early in gestation, injured fetal tissues can be completely recreated, without fibrosis, in a process resembling regeneration. Some organisms, however, retain the ability to regenerate tissue throughout adult life. Knowledge gained from studying such organisms might help to unlock latent regenerative pathways in humans, which would change medical practice as much as the introduction of antibiotics did in the twentieth century.

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