In adult mammals, maturation of blood and bone cells from their respective progenitors occurs in the bone marrow. The marrow region contains many progenitor and stem cell types that are confined by their biochemical and cellular microenvironments, referred to as stem cell niches. The unique properties of each niche assist the survival, proliferation, migration, and differentiation of that particular stem or progenitor cell type. Among the different niches of the bone marrow, our understanding of the osteohematopoietic niche is the most complete. Its properties, described in this chapter, are a model for studying adult stem cell differentiation, but a lot remains unknown. Our improved understanding of hematopoietic stem cell biology and its relationship with the properties of these niches are critical in the effective and safe use of these cells in regenerative medicine. Here, we review the current knowledge on the properties of these niches and suggest how the potential of hematopoietic progenitors can be utilized in regenerative medicine.
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