Stem Cells Flashcards
1
Q
What are stem cells and self renewal
A
- Stem Cell: Relatively undifferentiated cells that divide as necessary to produce new cells
- Self-Renew: To make more stem cells, sometimes after long periods of inactivity, mitotically divide, resulting cells continue to be unspecialised
2
Q
What is differentiation
A
- Under physiologic / experimental conditions, able to specialise into a cell type
- Extraordinary replication potential
- Resident stem cells maintain tissue homeostasis in response to perturbations / deviations
- The higher the degree of differentiation, the lower the replication potential of the cells
3
Q
What is somatic cell nuclear transfer (SCNT)
A
- Genome of differentiated adult somatic sheep cell (mammary gland cell) transplanted into an enucleated unfertilised oocyte donor embryo
- Hybrid cell stimulated to divide and at blastocyst stage implanted in a surrogate mother
- Specialised, differentiated cell types of the adult body contain a genome as complete as any embryo’s
- In mammals, genes are not lost during development, must therefore be regulated
- Change in gene expression, plays a key role in guiding and maintaining cell differentiation
- No father but three mothers: one provided egg, one DNA, one was the surrogate animal
4
Q
What is the potency of a stem cell
A
- Potency specifies the differentiation potential into other cell types
- Main difference between embryonic stem cells and Adult stem cells is the type of potency
- Totipotent, pluripotent, multi-potent, unipotent and induced pluripotent
5
Q
What are totipotent stem cells
A
- Only totipotent cells are fertilised egg and cells produced by first few divisions
- Isolated cell to produce a fertile, adult individual, ovum derived cytoplasmic (non-genetic) factors are critical
- Totipotent stem cells give rise to somatic stem/progenitor cells and primitive germ-line stem cells
6
Q
What are pluripotent stem cells
A
- Descendants of totipotent cells
- Self-renewal and a differentiation potential for all cell types and tissues of adult organism
- Multi-lineage differentiation
- Not capable of undergoing development on their own to form an entire organism
- Embryonic stem cells
7
Q
What are multipoint stem cells
A
- Potential to differentiate into multiple, but limited cell types (multi-lineage differentiation)
- Most adult stem cells (tissue / haematopoietic)
8
Q
What are unipotent stem cells
A
- Arise from multi-potent cells
- Only give rise to one cell type
- Can also self-renew
- Muscle, epithelial cells, RBC, WBC, platelets
9
Q
What are the uses of embryonic stem cells
A
IVF:
- Fertilisation by manually combining an egg and sperm in a laboratory dish
- Fertilised egg (zygote) is cultured for 2–6 days in a growth medium and implanted into a woman
- Several zygotes cultured at same time, excess frozen
- Saved for later implantation, donated for research
Stem Cell Line:
- Can be grown in vitro and propagated in their undifferentiated while retaining a normal karyotype
- Maintain property of multi lineage commitment over time
- Can differentiate in vitro into all cell types present in an organism, embryonic stem cell marker: Oct4
- Ethical and moral discussion on when life starts, no human application yet
10
Q
What are somatic stem cells
A
- Important for growth and to maintain tissue homeostasis by replenishing senescent or damaged cells
- Maintenance and regeneration of tissues dramatically decreases with age
- Reside in a specific area of tissue, a “stem cell niche”
- Can be extracted from many areas of body including bone marrow, fat, and peripheral blood
11
Q
What are induced pluripotent (iPSC) stem cells
A
- Differentiated somatic cells that have been genetically reprogrammed to pluripotent embryonic stem cell
- Forced to express genes important for maintaining defining properties of embryonic stem cells
- Not yet known if iPSCs and embryonic stem cells differ in clinically significant ways
- Human iPS cells were similar to human embryonic stem cells in morphology, proliferation, surface antigens, gene expression, epigenetic status of pluripotent cell-specific genes, and telomerase activity
- iPS cells could in vitro differentiate into cell types of three germ layers
12
Q
What are different applications of stem cells
A
- Cell Therapy: Traumatic spinal cord injury, parkinson’s, diabetes, heart disease, vision / hearing loss, burns, osteoarthritis
- Research: Info about complex events that occur during human development, disease modelling
- Drug Development: New medications tested on differentiated cells generated from pluripotent cell lines, safety and efficacy
- Regenerative Medicine: Cell replacement therapies, bone marrow stem cells, peripheral blood stem cells, umbilical cord blood stem cells, adipose tissue (fat) stem cells
13
Q
What are bone marrow transplants
A
- Procedure to replace defective bone marrow stem cells with healthy cells
- From peripheral blood after stimulation of stem cell replication through growth factors
- Or from bone marrow removed from a large bone through a large needle
- Replace stem cells that have been damaged by high doses of chemotherapy in patients
14
Q
What are allogenic stem cell transplantations
A
- Donor and recipient of stem cells are different people
- Possibility of graft-vs-host disease = rejection of tissue which is “not self”
- Allogeneic HSC donors must have a Human Leukocyte Antigen (HLA) type that matches the recipient
- Transplant donors may be related or unrelated (national marrow donor program)
- Even despite a good match of critical alleles, recipient will require immunosuppressive medications
- Also performed using umbilical cord blood as source of stem cells
15
Q
What is autologous stem cell therapy
A
- Isolation of own stem cells
- Harvested adult stem cells purified, assessed for quality and frozen
- Reintroduction of own cells (directly / after expansion to increase reserve)
- To replace destroyed tissue and resume patient’s normal blood cell production
- Stem cells come from same patient, there is no rejection
