MSK L22 Stem Cells Mo shariff Flashcards
ESCs show
Pluripotency → Generate cells derived from all three embryonic cell types: endoderm, mesoderm, ectoderm
ESC’s’ Derived from
Inner cell mas of 4-5 day old blastocyst
Human embryonic germ cells derived from
5-10 week old foetus are also pluripotent
Adult Stem Cells: Definition
Undifferentiated cell found among differentiated cells in a tissue/organ that can renew itself, and differentiate to yield specialised clel types
Adult Stem Cells:Primary role
Is to maintain and repair the tissue in which they are found
Adult Stem Cells: Origin in mature tissues
Unknown but they exist in many tissues
Haematopoietic and mesenchymal cell differentiation:
Step 1: Haemopoeitic stem cell forms a multipotential stem cell
Two lineages:
1. Lymphoid progenitor cells
a. Production of immune cells
2. Myeloid precursor
a. Productino of neutrophils, eosinophils, blood cells etc.
Stromal cells →
- Osteoblasts
- Osteocytes
- Chondroblasts
Adult Stem Cells:
- Adult stem cells typically generate cell types of tissue in which they reside
- Recent experiments indicate stem cells from one tissue can give rise to cells of a completely different tissue = PLASTICITY
a. Haemopoitic stem cells → neurones or muscle
b. Liver cells → made to produce insulin
Trans differentiation →
adult stem cell genetically engineered to behave as embryonic stem cell
ESC characteristics
Pluripotent
Large numbers
Easy to grow in culture
ASC characteristics
o Generally limitied to differentiation into cell types of their tissue origin n.b. evidence of plasticity
o Rare 00> identification and culture methods need
o Own patients cells therefore no rejection
Haemopoitic
- Continuously renewing stem cells
- Continuously formed
- Fluid phase
- Short-lived
- Simple structures (unicellular, matrix-free)
- Inflexible phenotype – little plasticity
Mesenchymal
o Stem cells (not necessarily continuously renewing)
o Formed at certain times
o Solid phase
o Long-lived
o Complex structures (multicell, matrix-bound)
o Plastic phenotype
Multipotent Mesenchymal Stem Cells:
Produced from →
- Bone
- Cartilage
- Adipose tissue
- Fibrous tissue
- Connective tissue
Identification of Adult Human MSCs →
- Capable of self-renewal and extensive proliferation
- Transplanted in vivo can create bone organ
- Remarkable phenotypic plasticity
- Differentiate into cells of tissues that are embryologically unrelated
- Ethically non-controversial alternative to Embryonic Stem Cells
- CFU-F and progeny not identifiable
- Some antibodies available
Transitional steps in OB lineage:
- Linear sequence → osteoprogenitor to preosteoblast to osteoblast, lining cells or osteocytes
- Identification by specific products → e.g. matrix proteins and receptor expression
- Osteoblasts defined by site on bone and ability to synthesize Collagen I, osteonectin, Osteopontin, Osteocalcin, Alkaline phosphatase
Panel of monoclonal antibodies →
- Facilitate selection of autologous bone marrow stem cells
a. Improved understandin of mesenchymal cell lineages (ageing and disease)
b. Monitor effects of therapeutics and treatment regimes - Clinical applications
a. Utilise osteogenic potential of MSCs in reconstructing localised skeletal defects
b. Gene therapy with MSCs
c. Reconstitution some/all of skeletal system to cure systemic diseases of bone such as osteogenesis imperfect
Regulation of osteoblast differentiation:
- BMps (quite a few)
- Most potent factors is osteoblast differentiation and function at extracellular level
- 15 BMPs cloned, several rhBMPs produced
- Various membrers expressed during skeletogenesis
- Osteoblasts express BMPs and receptors in bone formation
CBFA1/Runx2 →aiding in differentiation (KNOW THIS)
- Core- binding factor (CBF) transcription factors
2. Strong expression at osteogenic sites implicate it as an essential TF in osteoblast differention
- Cbfa1 -/- mice have
total lack of bone and retain partially calcified cartilaginous skeleton
a. Membranous bones of skull and endochondral bone in skeleton is lacking
- Cnfa1 +/- →
Cleidocranial dysplasia syndrome (CCD)
a. Affects teeth, bone, ribs and cranium.
b. Underdevelopment of the bones above