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Development and regeneration involves the coordination and organization of populations cells into a blastema, which is "a mound of stem cells from which regeneration begins". [25] Dedifferentiation of cells means that they lose their tissue-specific characteristics as tissues remodel during the regeneration process.
For studies of regeneration urodele amphibians such as the axolotl Ambystoma mexicanum are used, [53] and also planarian worms such as Schmidtea mediterranea. [10] Organoids have also been demonstrated as an efficient model for development. [54] Plant development has focused on the thale cress Arabidopsis thaliana as a model organism. [55]
Thus, dedifferentiation displays the ability of regeneration in the absence or scarcity of stem or progenitor cells. Recent studies discovered macrophages as an initial factor that contribute to the dedifferentiation of the cells in the site of injury and promote the formation of the progenitor cell pool during limb regeneration in the salamander.
Epimorphosis is defined as the regeneration of a specific part of an organism in a way that involves extensive cell proliferation of somatic stem cells, [1] dedifferentiation, and reformation, [2] as well as blastema formation. [3]
Examples include the injection of stem cells or progenitor cells obtained through directed differentiation (cell therapies); the induction of regeneration by biologically active molecules administered alone or as a secretion by infused cells (immunomodulation therapy); and transplantation of in vitro grown organs and tissues (tissue engineering).
Regeneration in humans is the regrowth of lost tissues or organs in response to injury. This is in contrast to wound healing, or partial regeneration, which involves closing up the injury site with some gradation of scar tissue.
Cellular atrophy is a decrease in cell size. If enough cells in an organ undergo atrophy the entire organ will decrease in size. Thymus atrophy during early human development (childhood) is an example of physiologic atrophy. Skeletal muscle atrophy is a common pathologic adaptation to skeletal muscle disuse (commonly called "disuse atrophy").
Endogenous regeneration in the brain is the ability of cells to engage in the repair and regeneration process. While the brain has a limited capacity for regeneration, endogenous neural stem cells, as well as numerous pro-regenerative molecules, can participate in replacing and repairing damaged or diseased neurons and glial cells.