Premium
Osteoblastic Activation in the Hematopoietic Stem Cell Niche
Author(s) -
CALVI LAURA M.
Publication year - 2006
Publication title -
annals of the new york academy of sciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.712
H-Index - 248
eISSN - 1749-6632
pISSN - 0077-8923
DOI - 10.1196/annals.1346.021
Subject(s) - stem cell , microbiology and biotechnology , haematopoiesis , biology , bone marrow , hematopoietic stem cell , notch signaling pathway , stem cell factor , immunology , signal transduction
Hematopoietic stem cells (HSC) are rare primitive cells capable of reconstituting all blood cell lineages throughout the life of an individual. The microenvironment in which stem cells reside is essential for their survival, self‐renewal, and differentiation. This microenvironment, or HSC niche, has been difficult to define in bone and bone marrow, but recent studies from our laboratory and others have shown that osteoblasts, the bone‐forming cells, are an essential regulatory component of this complex cellular network. We established that parathyroid hormone (PTH), through activation of the PTH/PTHrP receptor (PTH1R) in osteoblastic cells, could alter the HSC niche resulting in HSC expansion in vivo and in vitro and improving dramatically the survival of mice receiving bone marrow transplants. These findings are of great clinical appeal, because they suggest that a strategy aimed at modifying supportive cells in a stem cell niche can expand HSC. While a number of molecules have been found to be important for hematopoietic/osteoblastic interactions, we have focused on the Jagged1/Notch signaling pathway, which was necessary for the PTH‐dependent HSC expansion. Since the Jagged1/Notch signaling pathway has been implicated in the microenvironmental control of stem cell self‐renewal in several organ systems, definition of Jagged1 modulation, which is currently poorly understood, should provide additional molecular targets for stem cell regulation and advance the understanding of stem cell‐microenvironmental interactions.