Immunology

Vascular Origins

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Science  15 Sep 2006:
Vol. 313, Issue 5793, pp. 1543
DOI: 10.1126/science.313.5793.1543c

During the development of an embryo, cells of the hematopoietic system and endothelium have a common origin. Bone marrow-derived cells may even contribute to vessel growth in some settings. It has not been clear, however, whether hematopoietic cells normally contribute to vascular development.

Sebza et al. extend previous work in which the hematopoietic immune signaling proteins Syk and SLP-76 were found to regulate the developmental separation of lymphatic and blood vessel systems [Science 299, 247 (2003)]. Directed transgenic reexpression of SLP-76 in a subset of hematopoietic cells was sufficient to correct the defect in lymphatic-vascular connection apparent in mice that lack Syk and SLP-76. By generating chimeric animals bearing both wild-type and Syk/SLP-76-deficient cells, it was also possible to establish this phenomenon as an endothelial cell-autonomous effect. Thus, the study demonstrates that under steady-state conditions, cells of hematopoietic origin can contribute directly to blood lymphatic-vascular separation as precursors of endothelial cells. It will now be interesting to pursue experiments that more precisely characterize the progenitor cells and their relationship with endothelium during the processes of blood and lymphatic vessel growth and repair. — SJS

Dev. Cell 11, 349 (2006).

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