In this review the authors compared the architecture of the 2 HSC niches …

• Abstract
• Introduction
• Homeostatic regulation of stem cells by the niche
• The role of the osteoblastic niche in supporting HSC maintenance
• The role of the vascular niche in supporting proliferation, differentiation, and transendothelial migration of HSCs
• The relationship between the osteoblastic and vascular niches
• Molecules that mediate signaling and adhesive interactions between stem cells and their niches
• Adhesion molecules in the stem cell niches
• The vascular niche
• Chemokines and other molecules involved in HSC/HPC homing and mobilization
• Not all osteoblasts function as part of the HSC niche
• Conclusion
• Acknowledgments
• References
• Figures

We appreciate proofreading and editing by D. di Natale. We apologize to those whose papers are not cited here due to space limitations.

Footnotes 

Nonstandard abbreviations used: Ang-1, angiopoietin 1; BMP, bone morphogenic protein; CaR, Ca²⁺-sensing receptor; HPC, hematopoietic progenitor cell; LT-HSC, long-term HSC; MSC, mesenchymal stem cell; OPG, osteoprotegerin; PTH, parathyroid hormone; PTHrP, PTH-related protein; RANKL, receptor activator of NF-B ligand; SDF-1, stromal cell–derived factor 1; TK, herpesvirus thymidine kinase; VE-cadherin, vascular endothelial cadherin.

Conflict of interest: The authors have declared that no conflict of interest exists.