Stem cells

Two types broadly defined as embryonic and adult.

Human embryonic stem cells isolated from a 50-150 cell, 4-5 day old post fertilization blastocyst.

Human embryonic stem cells generate every specialized cell in the body and are able to demonstrate indefinite ex-vivo proliferation.

Human embryonic stem cells exist only transiently in-vivo during embryogenesis.

Embryonic stem cells difficult to control because of tendency to form tumors of all types of tissues.

Embryonic cells of the inner cell mass are pluripotent and give rise to the embryo itself, in contrast to the trophoblast, which gives rise to the extra embryonic tissues present during gestation.

Adult stem cells are located throughout the body and function as a reservoir to replace damaged and aging cells.

Stem cells are the longest living cells in many tissues.

The bone marrow, blood, and adipose tissue naturally harbor readily accessible adult stem cells.

Adult stem cells are present in significant numbers in many tissues throughout life.

Adult stem cells decrease in frequency with aging.

Stem cells and progenitor cells residing in various tissues are capable of generating daughter cells of different lineages.

Advancing age, the presence of comorbid conditions, the presence of underlying disease affect the ability of adult stem cells to regenerative repair.

Pluripotent embryonic stem cells are derived from the inner cell mass of pre-implantation blastocysts and are capable of performing all lineages of the body, while adult stem cells have a more restricted multi-potent differentiation capacity.

Defined by their ability to self renew, and the potential to form the cells derived from all three germ cell layers.

Embryonic stem cells are capable of giving rise to all tissues of the developing organism across all 3 embryonic germ layers when allowed to differentiate within the appropriate microenvironment.

Progenitor cells are referred to as having self renewal capacity, but with more restricted potential, and also are referred to as hematopoietic stem cells or mesenchymal stem cells.

Adult stem cells restricted in differentiation to cell lineages of the organ system in which they are located under physiologic conditions.

Both extrinsic and intrinsic cell factors regulate essential stem cell property of self renewal in each tissue.

The primary difference between a stem cell and other tissue cells is the epigenetic make up of DNA methylation and chromatin modifications.

Epigenetic regulators, transcription factors, and microRNAs play important roles in the self renewal of stem cells.

In contrast with pluripotental embryonic stem cells, adult stem cell have more limited defferentiation capacity.

Cell damage that occurs from toxins, ultraviolet radiation, or inflammation results and sell laws in replacement becomes accelerated.

Adult stem cells are multipotentnt in that they give rise to specialize cells restricted to an embryological germ layer despite cultivation and nurturing in an embryonic environment.

Adult stem cells are derived from bone marrow, adipose tissue and tissue-resident stem cells.

An adult human has approximately 10,000 to 20,000 hematopoetic stem cells.

Of bone marrow origin can differentiate into multiple hematopoietic and nonhematopoietic cell lines.

2 major stem cells in bone marrow are hematopoietic stem cells and mesenchymal stem cells.

Hematopoietic stem cells reside near the endosteum and the mesenchymal stem cells surround the vasculature and trabeculae.

Mesenchymal stem cells from multipotent stromal cells residing in various tissues including the bone marrow, adipose tissue, liver, and skeletal muscle and are able to contribute to tissue repairs and are able differentiating osteoblasts, adipocytes, or chondrocytes.

Hematopoietic stem cells provide the lineage for all mature blood cells.

Hematopoetic stem cells divide andcan give rise to either another stem cells or to a progenitor cell that eventually differentiated into mature cells such as red blood cells, granulocytes, lymphocytes, and platelets.

Self renewal refers to cell division that generates themselves.

Hematopoietic stem cells constitute approximately one of 50,000-100,000 nucleated bone marrow cells.

A single hematopoetic stem cell can regenerate the blood system in a lethally radiated mouse.

Hematopoietic stem cells-only 10-20% of injected intravenously home to bone marrow.

Maintain hematopoiesis by reconstituting into progenitor cells committed to lymphoid, myeloid cells.

Hematopoietic stem cells must balance demands of hematopoiesis with longer range goals of maintaining blood cell production for an individual’s lifetime.

Hematopoietic stem cells located in the bone marrow associated with a niche, a highly organized structure formed by stroma cells.

Hematopoietic stem cells can be mobilized by cytokines and chemokines with deaths-adhesion of such cells from the niche.

Apoptosis plays a major role in regulation of size of hematopoietic stem cell pool, as well as in the processes of hematopoietic cell differentiation.

There is a measurable and progressive decline in hematopoietic, intestinal and muscle stem cell function with aging, as noted by decline in immune cell function and age related anemia in elderly.

Hematopoietic stem cell aging is intrinsic to the aged cell and cannot be reversed by exposing cells to a younger microenvironment.

Mesenchymal stem cells can differentiate along multiple lineages and form cells of mesodermal lineage and can generate cells of other germ layers via transdifferentiation.

Mesenchymal themselves, also known as marrow stromal cells can give rise to bone, cartilage, and adipose tissue.

Mesenchymal stem cells can differentiate into neurons and can be found in the circulation and other types of tissues.

Differentiated adult cells, in contrast to stem cells do not spontaneously change their fates: but redirection is achievable by perturbations of transcriptional regulators present in each cell.

Bone marrow stem cells can differentiate into hepatocytes, dermal, lung, neuronal, endothelial gastrointestinal and cardiac muscle cells.

From umbilical cord blood associated with a decreased incidence of graft-versus-host disease.

The absolute number of CD34+ cells per kilogram of recipient weight is the most reliable and practical method for determining adequacy of a stem cell product.

Derived from bone marrow can differentiate into cells of mesodermal, ectodermal and endodermal origin.

Derived from bone marrow can generate endometrium.

Of gastrointestinal origin are under significant pressure secondary to high cell turnover rate.

Gastrointestinal stem cells are influenced by cytokines and growth factors that influence the fate of progenitor stem cells.

The entire lining of the gut is replaced approximately every seven days.

The skin epithelium is replaced once a month.

Gastrointestinal stem cells are supported by underlying mesenchymal cells in the lamina propria and communication and interaction between the mesenchymal and stem cells take place.

Gastrointestinal stem cells reside of the bottom of the colonic epithelial crypt.

Gastrointestinal stem cells in the small intestine occupy the fourth position counting from the crypt bottom where Paneth cells are located.

Perinatal stem cells are derived from umbilical cord blood and amniotic fluid derived stem cells.

Umbilical cord blood and amniotic fluid derived stem cells can give rise to adipose tissue, osteogenic, myogenic, endothelial, neuronal and hepatic lines.

In patients with chronic ischemic heart failure, transendocardial injection of autologous bone marrow mononuclear cells does not improve left ventricular end systolic volume, maximal oxygen consumption or reversibility on single photon emission tomography (FOCUS-CCTRN Trial).

In a phase 1/2 randomized comparison (POSEIDON study) of allogeneic and autologous mesenchymal stem cells in 30 patients with left ventricular dysfunction due to ischemic cardiomyopathy and followed for 13 months: Transendocardial injection of allogeneic and autologous mesenchymal stem cells were associated with low rates of serious adverse events, including immunologic reactions, and patients were favorably affected by functional capacity, quality-of-life, and ventricular remodeling.

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