Review Article

Stem Cell Niche Dynamics: From Homeostasis to Carcinogenesis

Figure 1

Quantitative aspects of the hematopoietic stem cell (HSC) niche. The left panel provides a structural picture of the niche, while the right panel shows a schematic representation of a mathematical model for the regulation of hematopoietic stem cell fate. The model incorporates population counts and signaling pathways that may play a role in regulating stem cell population dynamics. Cellular populations comprising the bone and vascular niches include osteoblasts (OBs), endothelial cells, HSCs, multipotent progenitors (MPPs), common myeloid progenitors (CMPs), common lymphoid progenitors(CLPs), and differentiated cells. Signaling from Wnt, β-catenin, p21, p18, and bmi-1 regulate self-renewal, while Notch and GSK3 feedback from progenitors inhibit differentiation that usually accompanies self-renewal. Signaling from osteoblasts includes osteopontin (Opn) expression that inhibits HSC self-renewal, parathyroid hormone-related protein (PPR) which increases HSCs, N-cadherin which binds β-catenin, and Tie2/angiopoietin which regulates quiescence.
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