#adult stem cells

Stem Cell -l

Which adult tissue is NOT known to have resident adult stem cells?

Adult tissues with turnover retain resident stem cells in specialized microenvironments. Brain harbors neural stem cells in subventricular zone and hippocampal dentate gyrus, muscle contains satellite cells beneath basal lamina, liver possesses oval cells and facultative progenitors for regeneration. Mature red blood cells are terminally differentiated, enucleated, anucleate biconcave discs lacking DNA, ribosomes, and proliferative capacity. They cannot divide or act as stem cells and are themselves products of hematopoietic stem cells. Their short lifespan of about 120 days requires continuous replacement from bone marrow, not intrinsic self-renewal within circulation.

Ref: Alberts, Molecular Biology of the Cell, 6th ed., Chapter 22: Adult stem cell niches.

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Stem Cell -ll

Which tissue does NOT contain adult stem cells?

Adult or tissue-specific stem cells populate most organs possessing high turnover or regenerative demand, including neural subventricular zone progenitors, hepatic oval cells, muscle satellite cells, and epidermal basal layer keratinocytes. They maintain full genomic complement, DNA repair capacity, and mitotic competence enabling self-renewal. Mature mammalian red blood cells extrude nucleus, ribosomes, and organelles during terminal differentiation steps to accommodate maximal hemoglobin content and enhance vascular deformability. Lacking chromatin, transcription, and division machinery, they cannot dedifferentiate or serve as stem cell reservoir, making them incapable of supporting sustained blood cell production despite abundance.

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 18: RBC enucleation terminal differentiation no stem cells.

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Stem Cell -ll

Which of the following is NOT a natural source of pluripotent stem cells?

Pluripotent cells naturally arise in early embryo as inner cell mass and embryonic stem cell cultures derived therefrom using LIF and 2i conditions, capable of generating three germ layers in differentiation. Induced pluripotent stem cells are engineered artificial surrogates recapitulating pluripotency but are not natural products of mammalian development in vivo. Mesenchymal stem cells from bone marrow, adipose tissue, and umbilical cord are multipotent, differentiating into bone, cartilage, and fat under Runx2, Sox9, PPAR-gamma control, not all embryonic lineages. Thus they are not classified among pluripotent sources, distinguishing broad embryonic potency from lineage-limited stromal potential.

Ref: Dominici et al., Cytotherapy 2006; Gilbert, Chapter 6: Mesenchymal stem cells multipotent not pluripotent source.

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Stem Cell -lll

Which tissue does NOT contain adult stem cells?

Adult stem cells are identified in many regenerative tissues including bone marrow hematopoietic and mesenchymal compartments, intestinal crypts, hair follicle bulge, basal epidermis, liver oval cells, satellite cells of muscle, and subventricular zone of brain. They require vascular support, stromal signals, and basement membrane attachment for survival. Mature erythrocytes are highly specialized, enucleated, organelle-free cells lacking DNA, transcriptional capacity, and mitotic machinery. Therefore they cannot house self-renewing reserve, de-differentiate, or contribute to regeneration, distinguishing terminal differentiation from stem cell reservoirs essential for homeostasis.

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 18: Adult stem cell reservoirs and terminal RBC anucleation.

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Stem Cell -lll

Adult stem cells are primarily responsible for:

Adult stem cells persist postnatally within specialized niches such as bone marrow, intestinal crypts, and hair follicle bulge. Unlike embryonic stem cells that construct the entire organism, these tissue-resident populations maintain homeostasis by replacing short-lived differentiated cells lost to turnover, injury, or mechanical stress. Through balanced self-renewal and lineage commitment governed by Wnt, Notch, BMP and local growth factors, they generate transit-amplifying progenitors that restore epithelia, blood, muscle, and neural lineages, ensuring long-term repair without forming extraembryonic tissues or whole embryos during adulthood.

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 6: Adult stem cells, niche maintenance and tissue repair mechanisms.

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