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#tissue regeneration

3 public questions tagged with this topic.

Stem Cell -ll

The term 'stem cell niche' refers to:

Schofield originally proposed the niche concept in 1978 to describe a specialized environmental unit that physically limits stem cell number and preserves phenotype. Molecularly, it comprises supporting stromal cells secreting BMP, Wnt, FGF, adhesion molecules like N-cadherin, oxygen tension modulators, and extracellular matrix providing mechanical cues through stiffness. Disruption of niche architecture leads to stem cell loss or tumorigenic over-proliferation due to loss of quiescence signals. Unlike generic storage sites, the niche actively instructs self-renewal versus differentiation balance through short-range juxtacrine and paracrine interactions governing regeneration and aging.

Ref: Schofield, Blood Cells 1978; Spradling et al., Nature 2001: Niche microenvironment regulating stem cell behavior.

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Stem Cell -lll

Which of the following is an example of a stem cell niche?

A niche is defined as a local microenvironment that physically anchors, sustains, and instructively controls stem cell behavior through contact, paracrine signals, and extracellular matrix mechanics. Classic examples include basal layer of interfollicular epidermis where hemidesmosomes attach basal keratinocyte stem cells to laminin-rich basement membrane, and adjacent dermal fibroblasts provide Wnt and BMP inhibition to prevent differentiation. Other prototypes are bone marrow endosteal niche, intestinal crypt base, and Drosophila cap cells. Trophoblast, erythrocytes, and mature neurons are differentiated products, not regulatory supportive sites at all.

Ref: Scadden, Nature 2006; Fuchs et al., Cell 2004; Gilbert, Chapter 6: Niche definition skin basal layer example.

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Regeneration -l

Which process in regeneration involves the formation of a regeneration blastema?

Regeneration blastema denotes accumulation of undifferentiated proliferative cells at amputation plane beneath specialized wound epidermis. Its formation defines epimorphosis, regeneration involving considerable cell dedifferentiation, migration, and mitotic expansion prior to re-differentiation recapitulating developmental morphogenesis. Salamander limb blastema requires nerve signals and FGF from apical epidermal cap to sustain proliferation. Morphallaxis proceeds without visible blastema via repatterning existing tissues, compensatory regeneration expands remaining cells via hypertrophy and mitosis without blastema as liver, direct transdifferentiation converts differentiated cell type into another without intermediate blastema, such as lens regeneration from iris pigment epithelium.

Ref: Gilbert, Developmental Biology, 12th ed., Chapter 19: Epimorphosis and regeneration blastema in salamander limb.

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