Self-renewal of stem cells Asymmetric cell division : to maintain the stem cell numberA. Intrinsic asymmetric cell divisionB. Extrinsic (Eviromental) asymetric cell devision Morrison & Kimble 2006
Intrinsic asymmetric cell division One stem cell divides into two daughter cells, which are different from each other. One of daughter cells is similar to the parental cell and The other daughter cell becomes progenitor cell, which will eventually differentiate into tissue committed resident cell.
Stem cells NICHE The microenvironment in which stem cells are found. The microenvironment interacts with stem cells to regulate stem cell fate. Various niche factors act on stem cells to alter their gene expression, and induce their proliferation or differentiation.
Stem Cells NICHENiche factors include: 1. cell-cell interactions between stem cells, 2. interactions between stem cells and neighboring differentiated cells, 3. interactions between stem cells and extra- cellular matrix components, adhesion molecules,growth factors, cytokines and physiochemical nature of the microenvironment. 4. Niche has both anatomic and functional dimensions.
Regenerative medicinal applications should meet the following criteria: Can be found in abundant quantities (millions to billions of cells) Can be harvested by a minimally invasive procedure Can be differentiated along multiple cell lineage pathways in a regulatable and reproducible manner. Can be safely and effectively transplanted to either an autologous or allogeneic host
Stem Cells Transplantation Autologous Allogeneic : from individuals belonging to the same species but genetically dissimilar (and hence immunologiccally incmpatible) Syngeneic : between geneticcally identical individual (tween) Xenogeneic : From individuals of different species (hence of disparate cell type)