Abstract
The hematopoietic system consists of: (1) a network of stem and progenitor cells of varying degrees of maturity interacting with other cells that possess supportive and regulatory capacities and (2) vascular stem cell niches with supporting stem cells in their selfโrenewal, proliferation, differentiation, and mobilization to the circulation. Recent data suggest that selective expression of organโspecific chemokines promotes the mobilization of boneโmarrowโderived pluripotent cells, a process that is essential for tissue vascularization and organ regeneration. Despite intensive investigation, the pathways by which mechanical signals are converted to biochemical responses are not completely understood. Recent studies have suggested that chromatin shifts and cell cycle effects stem cell gene expression, and thus results in changes of its surface receptor expression at different points of the cell cycle machinery, therefore changing cell cycle transit. This review will attempt to discuss new approaches to determine the regulation of stem cell growth and differentiation by underlying the significance of the chaotic dynamics of transcriptional networks within a cell, with a combination of chemokines and cytokines in the environment, and mechanical forces, such as; stretch, strain and laminar flow, all involving both cooperation and competition. J. Cell. Physiol. 213:672โ678. ยฉ 2007 WileyโLiss, Inc.