It seems appropriate that Science, one of the world’s top scientific journals, has this week published a special edition that surveys recent progress in our understanding of how our organs develop. This basic research underpins the use of stem cells in medicine and tissue engineering, and the reviews that make up the special report provide an excellent insight into how much we have learned in the past decade, and how much we have yet to learn. Amid the discussion of different theories about how particular cells and tissues develop and the strength of the evidence supporting those theories one thing becomes very clear; the vital role played by research on animals as diverse as the fly, zebrafish, chick and mouse. For example while discussing one area of research, the process of branching morphogenesis where cells expand their surface area by forming extensions during organ development, Pengfei Lu and Zena Werb (1) observe that:
“Due to their structural simplicity and genetic accessibility, the Drosophila tracheal and air sac systems have given insight into understanding how epithelial branching occurs in the more complex organ systems of vertebrates. With recent technical advances, including modern mouse genetics, cell fate–mapping, mosaic analysis, and live imaging of organ cultures, our understanding of vertebrate branching mechanisms has dramatically improved.”
An excellent example of ongoing research into organ development is provided by scientists at UCLA (2) who have shown in developing mouse embryos that the hematopoietic stem cells that produce the cells of the blood originate in the endothelial cells that line the inside of blood vessels. This discovery will help scientists who are trying to find ways to produce hematipoietic stem cells from the cells of a patient’s own blood vessels in the lab for use in transplants, for example after treatment for leukemia. If that is successful it may well benefit from another piece of work published this week (3), this time by scientists at Harvard University. The Harvard team used sophisticated imaging techniques, including the use of GFP-labeled cells, to map the fate of hematopoietic stem cells and their derivatives that were injected into mice. This work, which demonstrates what happens to the cells under different conditions in unprecedented detail, should enable scientists to develop new techniques to optimize hematopoietic stem cell transplant.
Regenerative medicine and tissue engineering are exciting areas of research, and will no doubt grab many headlines in coming years; its worth remembering all the animal researchers who work hard behind the scenes to make the breakthroughs happen.
1) Lu. P and Werb Z. “Patterning mechanisms of branched organs” Science Vol. 322 (5907) pages 1506-1509 (2008) DOI: 10.1126/science.1162783
2) Zovein A.C. et al. “Fate tracing reveals the endothelial origin of hematopoietic stem cells” Cell Stem Cell, Vol. 3 (6), pages 625-636 (2008) DOI:10.1016/j.stem.2008.09.018
3) Celso C.L. et al. “Live-animal tracking of individual haematopoietic stem/progenitor cells in their niche” Nature, Published online 3 December 2008, DOI:10.1038/nature07434