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quote:Adipose derived adult stem cellsAdipose-derived stem cells (ASCs) have also been isolated from human fat, usually by method of liposuction. This cell population seems to be similar in many ways to mesenchymal stem cells (MSCs) derived from bone marrow. However, it is possible to isolate many more cells from adipose tissue and the harvest procedure itself is less painful than the harvest of bone marrow. Human ASCs have been shown to differentiate in the lab into bone, cartilage, fat, muscle, and might be able to differentiate into neurons, making them a possible source for future applications in the clinic. In support of this, current studies in animals suggest that ASCs might be able to repair significant bony defects and ASCs have been recently used to successfully repair a large cranial defect in a human patient .Haematopoietic stem cellsMain article: Pluripotential hemopoietic stem cellMammary stem cellsMammary stem cells provide the source of cells for growth of the mammary gland during puberty and gestation and play an important role in carcinogenesis of the breast. Mammary stem cells have been isolated from human and mouse tissue as well as from cell lines derived from the mammary gland. A single such cell can give rise to both luminal and myoepithelial cell types of the gland and has been shown to regenerate the entire organ in mice.Neural stem cellsThe existence of stem cells in the adult brain has been postulated following the discovery that the process of neurogenesis, birth of new neurons, continues into adulthood in rats. It has since been shown that new neurons are generated in adult mice, songbirds and primates, including humans. Normally adult neurogenesis is restricted to the subvetricular zone, which lines the lateral ventricles of the brain, and the dentate gyrus of the hippocampal formation. Although the generation of new neurons in the hippocampus is well established, the presence of true self-renewing stem cells there has been debated. Under certain circumstances, such as following tissue damage in ischemia, neurogenesis can be induced in other brain regions, including the neocortex.Neural stem cells are commonly cultured in vitro as so called neurospheres - floating heterogeneous aggregates of cells, containing a large proportion of stem cells. They can be propagated for extended periods of time and differentiated into both neuronal and glia cells, and therefore behave as stem cells. However, some recent studies suggest that this behaviour is induced by the culture conditions in progenitor cells, the progeny of stem cell division that normally undergo a strictly limited number of replication cycles in vivo. Furthermore, neurosphere-derived cells do not behave as stem cells when transplanted back into the brain.Neural stem cells share many properties with haematopoietic stem cells (HSCs). Remarkably, when injected into the blood, neurosphere-derived cells differentiate into various cell types of the immune system. Cells that resemble neural stem cells have been found in the bone marrow, the home of HSCs. It has been suggested that new neurons in the dentate gyrus arise from circulating HCSs. Indeed, newborn cells first appear in the dentate in the heavily vascularised subgranular zone immediately adjacent to blood vessels.Olfactory adult stem cellsOlfactory adult stem cells have been successfully from the cells harvested from the human olfactory mucosa, the lining of the nose involved in the sense of smell.Adult stem cells isolated from the olfactory mucosa (cells lining the inside of the nose involved in the sense of smell) have the ability to develop into many different cell types if they are given the right chemical environment. These adult olfactory stem cells appear to have the same ability as embryonic stem cells in giving rise to many different cell types but have the advantage that they can be obtained from all individuals, even older people who might be most in need to stem cell therapies. Olfactory stem cells hold potential for therapeutic applications. Thanks to their location they can be harversted with ease without harm to the patient in contrast to neural stem cells.
quote:Embryonic stem cells (ESCs) are stem cells derived from the inner cell mass of a blastocyst, which is an early stage embryo - approximately 4 to 5 days old in humans - consisting of 50-150 cells. Embryonic stem cells are pluripotent, meaning they are able to differentiate into all derivatives of the three primary germ layers: ectoderm, endoderm and mesoderm. In other words, they can develop into each of the more than 200 cell types of the adult body when given sufficient and necessary stimulation for a specific cell type. When given no stimuli for differentiation, ESCs will continue to divide in vitro and each daughter cell will remain pluripotent. The pluripotency of ESCs distinguishes them from adult stem cells or progenitor cells, the latter two only having the capacity to form a more limited number of different cell types.Because of their unique combined abilities of unlimited expansion and pluripotency, embryonic stem cells are a potential source for regenerative medicine and tissue replacement after injury or disease. To date, no approved medical treatments have been derived from embryonic stem cell research. This is not unusual for a new medical research field; in this case, the first human embryonic stem cell line was only reported in 1998.
quote:Umbilical cord blood is human blood from the placenta and umbilical cord that is rich in hematopoietic stem cells. Cord blood is collected after the umbilical cord has been detached from the newborn, and utilized as a source of stem cells for transplantation. Cord blood stem cells are more proliferate and have a higher chance of matching family members than stem cells from bone marrow. Fathers have a 25% chance of matching their child's cord blood stem cells. Siblings have a 25% chance of being a perfect cord blood match.