Introduction to special issue

New Release: The Complete Guide to Organ Repair

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Science  05 Dec 2008:
Vol. 322, Issue 5907, pp. 1489
DOI: 10.1126/science.322.5907.1489

Clinicians and patients will clamor for a copy when publishers send out this announcement. But how long until its release? No one knows. Fortunately, collaborations between basic research and translational medicine are providing enough information to start writing the prologue. Research is telling us that in most cases, successful organ repair will not result from simply tossing willy-nilly a few ingredients, such as stem cells, into the broken body. Instead, assembly of the repair and regeneration toolkit will require detailed knowledge of the specific cell types in an organ, efficient ways to direct cell differentiation and target cell delivery, methods to tweak cell communication, and sophisticated bioengineering innovation.

The collection of articles in this issue boasts exciting advances toward elucidating diverse organ features. A Review by Chien and colleages (p. 1494) highlights organ complexity as exemplified in cardiogenesis. Despite a long-held view of the heart as a simple muscular pump, there is much more to it—cells of varied types and intricate collaboration with the vasculature and electrical conduction system, not to mention the involvement of biomechanical forces and three-dimensional structure. Substantial progress has been made toward understanding two other organs, the liver and pancreas, which share a common endodermal origin. Zaret and Grompe (p. 1490) detail how mechanisms of normal development are recapitulated during regeneration, or not. But where is the engine that powers organ development and regeneration? We turn to stem cells for this, at least in part. Although we've witnessed intense scientific and public interest in these valuable cells, do we really know what they are, which ones truly exist in the body, or their origin? Slack (p. 1498) gives his perspective.

To make an organ or prompt its natural regeneration, we must step back to gain an intimate understanding of basic cell movements and collaboration. As highlighted by Montell (p. 1502), single disconnected cells do not an organ make; collective cell activities are key. In a related Review, Lu and Werb (p. 1506) describe organ cell morphogenesis as it occurs in the branching systems of the vertebrate mammary gland, prostate, and lung, as well as the invertebrate tracheal system.

Related content in Science Signaling (9 December 2008) highlights organogenesis in plants. Root nodules develop on the roots of legumes in response to bacterial infection. These specialized organs serve as the site for nitrogen fixation. Crespi and Frugier focus on the bacterial and host-generated signals that induce and regulate nodule organogenesis. The more familiar plant organ, the leaf, is crucial for photosynthesis and respiration. Gray et al. discuss peptide signals that activate leucine-rich repeat receptor pathways to regulate vein versus stoma cell fate in the leaf.

Although chapters of the clinicians' and horticulturists' repair guides are in the drafting stages, the long lists of capable contributors are sure to craft a good read.

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