Sonic hedgehog expands diaphyseal trabecular bone altering bone marrow niche and lymphocyte compartment.
Bone marrow contains distinct microenvironments that regulate hematopoietic stem cells (HSCs). The endosteal HSC niche includes osteoblasts, mineral, and extracellular matrix proteins that interact through various molecular signals to control HSCs. Sonic hedgehog (Shh) is a morphogen involved in the regulation of skeletal development and hematopoiesis, but the effects of Shh on bone in relation to the HSC niche are not well understood. We demonstrate that systemic overexpression of Shh in mice increases osteoblast number with the resultant formation of new trabeculae in the femoral diaphysis. Suggestive of a functional change in the hematopoietic niche, numbers of Lin(-) Sca-1(+) c-Kit(+) cells with hematopoietic progenitor function expand, although cells with in vivo repopulating capacity in the wild-type environment do not increase. Instead, Shh mediates a decrease in number of bone marrow lymphocytes accompanied by a decreased expression of stromal-derived growth factor 1 (SDF-1) and a decrease in Flk2-expressing Lin(-) Sca-1(+) c-Kit(+) cells, indicating a modulation of early lymphopoiesis. This is caused by a microenvironment-induced mechanism as Shh treatment of bone marrow recipients, but not donors, results in a dramatic depletion of lymphocytes. Together, these data suggest that Shh mediates alterations in the bone marrow hematopoietic niche affecting the early lymphoid differentiation.
Kiuru
Maija
M
Department of Genetic Medicine, Weill Medical College of Cornell University, New York, New York 10065, USA.
Hidaka
Chisa
C
Hubner
Ralf-Harto
RH
Solomon
Jason
J
Krause
Anja
A
Leopold
Philip L
PL
Crystal
Ronald G
RG
D000256:Adenoviridae / Q000235:genetics; D000818:Animals; D001853:Bone Marrow / Q000378:metabolism*; D016026:Bone Marrow Transplantation; D054377:Chemokine CXCL12 / Q000378:metabolism; D005434:Flow Cytometry; D005455:Fluorescent Antibody Technique; D005822:Genetic Vectors / Q000235:genetics; D053823:Hedgehog Proteins / Q000235:genetics / Q000502:physiology*; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D008214:Lymphocytes / Q000166:cytology* / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D010006:Osteoblasts / Q000166:cytology / Q000378:metabolism; D016133:Polymerase Chain Reaction; D055114:X-Ray Microtomography
D054377:Chemokine CXCL12; C515256:Cxcl12 protein, mouse; D053823:Hedgehog Proteins; C465570:Shh protein, mouse