Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Extracellular matrix wikipedia , lookup
Signal transduction wikipedia , lookup
Cell culture wikipedia , lookup
List of types of proteins wikipedia , lookup
Cell encapsulation wikipedia , lookup
Tissue engineering wikipedia , lookup
Cellular differentiation wikipedia , lookup
The sentinel stem cell Since Irving Weissman’s research team reported that hematopoietic stem cells (HSCs) are known to circulate in blood physiologically (1), functional significance of the constitutive migration has remained elusive. A team led by Ulrich von Andrian at Harvard has recently reported in Cell (2) an important role of circulating HSCs – to provide an immediate source to boost innate immunity. Mature lymphocytes that circulate in blood migrate into organs and subsequently drain into lymph for immunosurveillance. To investigate whether circulating HSCs themselves follow this path, von Andrian’s group initially identified a HSC pool in thoracic duct lymph using both immunotyping and serial transplantation. They also showed using pharmacological approach that HSCs egress from extramedullary tissues into lymph in part via a Gαi-coupled S1P1 receptor. Since HSCs also express Toll-like receptors necessary for recognition of bacterial lipopolysaccharide (LPS), the research team implanted isolated HSCs in kidney with or without LPS and showed that HSCs respond to LPS by actively differentiating into myeloid cells. During differentiation, HSCs and their progenitors appear to reside within peripheral tissues as there is lower number of implanted cells in circulation after LPS treatment. Finally, their in vitro experiment suggests that LPS treatment slows down the mobility of HSCs and progenitors and this correlates with the downregulation of S1P1 receptor mRNA. Source: Fig. 7c Schematic model illustrating the trafficking of migratory HSCs and progenitors under physiological conditions and during an inflammation (Massberg et al., 2007, Copyright, Cell Press) This study demonstrates for the first time the role of constitutively circulating HSCs. With better understanding of molecular players responsible for migration and homing of HSCs in the immune system, it will be possible for us to leverage a differentiating capacity of adult stem cells in endogenously supplying sentinel cells upon immune attack. This may obviate an inconvenient approach to correct a defective immune system, such as T-cell immunotherapy. It also remains to be elucidated what controls trafficking of HSCs from blood into specific organs. 1. http://www.sciencemag.org/cgi/content/abstract/sci;294/5548/1933 2. http://www.cell.com/content/article/abstract?uid=PIIS0092867407013566 Posted by Jae-Won Shin 12/02/07