Stem Cells/Cell Differentiation Flashcards
(65 cards)
1
Q
Uses for stem cells
A
- increased understanding of how diseases develop
- cure diseases
- test new drugs for safety
- generate new stem cells to replace or aid diseased or damaged organs
- research how certain cells (ex: cancer stem cells) develop into cancer
- regenerative medicine applications
- fix genetic diseases in the future
- tissue engineering– organs on a chip
- clean meat industry
2
Q
Wooly Mammoth Meatball
A
- Australian start-up company “Vow” has investigated the potential of more than 50 species from alpaca to peacocks to fish for generating meat from stem cells
- they used DNA from the mammoth (but only one gene) and inserted it into sheep cells
- not sure of the next steps to generate the meat but it was a great publicity stunt
- first product to be offered in Singapore will be Japanese Quail
3
Q
printing human organs in space
A
- printing things like capillaries, is difficult in Earth’s gravity because an initial scaffolding/support structure is necessary to form the shape of the tissue
- BioFabrication Facility wants to print in microgravity using ultra-fine layers of bioink that can be several times thinner than human hair
- long term plan: manufacture entire human organs in space
4
Q
Engineered Heart Tissues
A
- study
- looks at how human heart tissue functions in space
- uses unique 3D tissues made from heart cells derived from human indiced pluripotent stem cells (adult stem cells)
- engineered heart tissues are complex 3D structures, each about the size of a few grains of rice
- more similar to a few tissues in the body than flat cell cultures in a petri dish or those floating in a flask of liquid
5
Q
Hope Biosciences
A
- Phase II clinical trial evaluating efficacy and safety of Hope Biosciences’ analogous, adipose-derived mesenchymal stem cells to provide immune support against COVID-19
- MSCs are known for immunomodulatory and regenerative potential
- been shown to be safe and effective in attenuating systemic inflammation
6
Q
stem cell
A
- a cell that can renew (divide) or differentiate
- controlled by stem cell “niche”
- number of doublings influenced by source and type
- hESCs and iPSCs are immortal
- adult sources have 100-200 doublings–> more than a typical stem cell that is regulated by the Hayflick limit
- can make 2 differentiated cells, 2 stem cells, or one of each when dividing
7
Q
adult stem cells
A
- most popular are adipose (fat) derived mesenchymal stem cells now in more than 700 stem cell therapy trials globally
8
Q
fetal stem cells
A
amniotic, umbilical cord, placental
9
Q
embryonic stem cells
A
- hESCs and hPSCs with hESCs in US clinical trials as of 2012
10
Q
induced pluripotent stem cells
A
- iPSCs are not in clinical trials in US but patients being treated in Japan and Australia
11
Q
Differentiation
A
- cell becomes more specialized such as fibroblast or hepatocyte
- differentiation can be partial or full so critical and accepted molecular metrics need to be in place to compare (ex: one iPSC generated hepatocyte to another iPSC generated hepatocyte–> RNA Seq is one metric)
12
Q
restricted lineage
A
- some stem cells are limited to only one or two types of cells, while others are totipotent
- “progenitor” cells
13
Q
transdifferentiation
A
- direct reprogramming
- ability of a differentiated cell to become another type of differentiated cell without going through an embryonic step
- first done experimentally in 1987 but several cells have been generated since that time
- doesn’t happen naturally in vivo
14
Q
dedifferentiation and redifferentiation
A
- ability of a cell to become more embryonic-like and differentiate into another cell type in vivo
- chemicals like “reversine” can induce de-differentiation
- demonstrated in Eastern Red Spotted Newt (can regenerate lost limbs and eyes
15
Q
dedifferentiation
A
when a specialized cell reverts back to a more “stem-like” cell so that it can become other types of cells
16
Q
redifferentiation
A
- occurs after dedifferentiation and means that the cell can specialize again into the same type of cell or different
17
Q
stem cell niche
A
- stem cell microenvironment
- critical to controlling cell division vs differentiation
- complex and includes: neighboring cells, extracellular matrix, local growth factors, physical environment
18
Q
totipotent
A
- all cell types
- highest level of “stemness”
- only cell known to be totipotent is egg
19
Q
pluripotent
A
- many cell types
- restricted stemness
20
Q
multipotent
A
- several cell types
- stemness even more restricted
21
Q
unipotent
A
- one cell type only
- progenitor cell, lowest level of “stemness”
22
Q
blastocyst
A
- late pre-implantation stage embryo
- hESCs originate from inner cell mass
23
Q
chimera test
A
- can determine if a stem cell it totipotent in vivo
- legal with mice but not with humans–> can never prove that any human stem cell derived or isolated in the lab is truly totipotent
- only true test of totipotency of a candidate stem cell
- label test stem cell with GFP
- implant GFP-labelled test stem cell in blastocyst and then implant chimeric embryo in surrogate mother
- now track that GFP labelled stem cell in all tissues and organs of newborn
- mESC (mouse derived) are totipotent but can’t say the same for hESC
24
Q
biodistribution and homing
A
- ability of stem cells to find “home” (its targetted tissue)
- damaged or compromised tissue releases factors that causes endogenous MSCs to home to damage site
- occurs in vivo: transplanted XX hearts in XY patients have XY cardiomyocytes upon autopsy– a clear demonstration of endogenous stem cell homing and repair
25
induced pluripotent stem cells
- immature cells generated from adult cells that have been reprogrammed back into an embryonic-like pluripotent state
- this makes it so they can differentiate into any type of cell in the body--> unlimited source of human cells for therapeutic purposes
- discovered by Shinya Yamanaka
26
STAP
- stimulus triggered acquisition of pluripotency
- proposed method of generating pluripotent stem cells by subjecting ordinary cells to stress
- retracted as fraudulent
27
fusogenic
- problem with stem cells
- they can spontaneously fuse with each other forming a tetraploid cell (could generate cancer stem cells)
- when injected into patients mechanical stress can cause fusion
28
bioethics
- the norms of conduct
- relative term and country dependent
29
therapeutic cloning
- production of embryonic stem cells for the use in replacing/repairing damaged tissues or organs, achieved by transferring a diploid nucleus from a body cell into an egg whose nucleus has been removed
- creating embryo develops under laboratory conditions
- responsible for creating embryonic stem cells to treat diseases such as diabetes and Alzheimer's disease
30
reproductive cloning
- the deliberate production of genetically identical individuals; each newly produced individual is a clone of the original
- creating embryo develops under uterine conditions
- important for harvesting stem cells that can be used to study embryonic development
31
SCID
- severe combined immuno deficiency
- have no B and T cells and thus have a compromised immune system
- are used for determining if an injected candidate stem cell can differentiate in vivo into a multitude of tissue and cell types in vivo
- are also used to determine if a candidate human cancer cell can generate tumors in vivo
32
three ways to generate stem cells in the lab
- somatic cell nuclear transfer
- parthenogenesis
- induced pluripotent stem cells
33
Somatic cell nuclear transfer
- an oocyte is taken from female animal and its nucleus is removed
- somatic cell that still has its DNA is taken from the animal that is being cloned
- nucleus from the somatic cell is injected into the egg cell that had its nucleus removed and the cell is stimulated to begin divisions and the embryo starts to develop
- embryo is implanted into a surrogate mother where it develops into the organism
34
Sir Ian Wilmut
- cloned Dolly in 1996
35
John Gurdon
- cloned frogs in 1960 and was awarded a Nobel Prize in 2012
36
Why is SCNT challenging
- 1000s SCNT are required for one implantable embryo
- first pet clone (cat) was "Little Nicky" in 2004
- some still attempting human SCNT designed for therapeutic cloning because hESCs could serve as an autograft
37
Dolly and siblings
- Dolly was born in Edinburgh University in 1996
- Dolly was euthanizes at age 6 because of lung disease and advanced arthritis
- other identical clones in 2016 from same SCNT are fine
38
what did SCNT show
that a somatic nucleus could create an entire functioning animal due to cytoplasmic factors in the egg
39
cloning of primates
- cloned Rhesus monkey has now survived for over two years
-identical NHP are better for frug testing due to lack of genetic variability
40
parthenogenesis
- natural form of asexual reproduction
- occurs when female gamete develops into an embryo without fertilization
41
Experimental parthenogenesis
- artificial parthenogenesis was first shown in 1913 by Loeb using two experimental systems
- unfertilized sea urchin eggs were induced to undergo parthenogenesis by changing the osmolarity of the surrounding medium
- unfertilized starfish eggs could do the same using dilute acid
42
benefits of using hPSCs for therapeutic cloning
- only 200-300 eggs would be required to generate hPSCs that could match anyone in the world
43
limitations and issues of using hPSCs for therapeutic cloning
- all alleles will be homozygous because of no sperm thus chance of phenotypic expression of a mutation is high compared to heterozygote
- not FDA approved in US
44
converting human somatic cells to stem cells
= iPSCs
- somatic cells can be converted to true stem cells with only 4 additional genes
45
Shinya Yamanaka
- used retrovirus to ferry into adult human fibroblasts OCT3/4, SOX2, KLF4, and c-MYC genes
- sources were skin cells from 36 year old female and 69 year old man= age of donor somatic cell is not important
- converted human somatic cells to stem cells
46
James Thomson
- used OCT3/4, SOX2, NANOG, and LIN28 genes
- converted human somatic cells to stem cells
47
RT-PCR
- true differentiation in culture as revealed by appropriate markers
48
The SCID Mouse test
- Is a teratoma generated by iPSC injection?
- the iPSCs form teratomas in mice-- a non-malignant mass of differentiated cells derived from iPSCs
- tera= greek for monstrous
49
teratocarcinoma
- a malignant teratoma that originated from embryonic cells or stem cells
- all stem cells can differentiate into teratoma
- inside teratoma= "hand", teeth...etc
50
promise of iPSCs
- basic research on differentiation
- can make patient specific cells of individuals carrying genetic defects-- useful for drug development
- source of cells in the future for stem cell therapy
51
reversing cell aging
- "Maturation Phase Transient Reprogramming"= turning back the aging clock
- measured telomere attrition, genetic instability, epidenetic and transcriptional alterations and the accumulation of misfolded proteins-- all accepted markers of cell aging
- used same 4 Yamanaka reprogramming factors but rather than waiting 50 days culture time to generate iPSCs, they waited just 13 days and the cell has now reversed it aging process by 30 years
52
cellular reprogramming and liver regeneration
- used short-term (1 day_ Yamanaka factor protocol to partially reprogram mice liver tissue
- liver exhibited improved regeneration and younger characteristics--> didn't generate teratomas/cancers that is typical of a standard longer Yamanaka procedure
53
Pros and cons of SCNT
- could be used for an autologous or allogeneic transplant
- no US federal laws banning therapeutic or reproductive cloning but some states forbid it
- but is it ethical?--> a human embryo is being created
54
parthenogenesis
- can match to a world population-- only 300 eggs required
0 but all alleles are homozygous, not heterozygous
- allogeneic, not autologous like SCNT unless female donated egg
- But is it ethical?--> a human "embryo" is being created
55
iPSCs
- no "human embryo" created
- can be autologous or allogeneic
- but potential for teratocarcinomas
- more pluripotent than fat-derived adult mesenchymal stem cells and easier to procure
56
tumorigenicity
- stem cells have long telomeres and can divide many more times than normal cells (telomeres="mitotic clock")
- propensity to form tumors such as teratocarcinomas
- one clinical trial started in Japan--> was stopped after only one patient due to this concern
57
Immunogenicity
- propensity to trigger immune response
- the more frequent the stem cell injections the higher the chance of immune rejection complications that could include anaphylaxis
58
inappropriate differntiation
- risk of stem cells differentiating into cells that were not intended and not native to target organ
59
cord blood
blood replacement and stem cell therapy
- can be used for things like: blood disorders, immune deficiencies, genetic disorders, neurologic disorders, research...etc.
60
Private cord blood bank
- incorporated as a "for profit" organization
- donors pay an initial fee and a maintenance fee
- cells not available to the public
- better if ther is a genetic disease in the family and multiple members require the cells
61
public cord bank
- incorporated as a "not for profit" organization
- available to the public through the National Marrow Donor Program through which cord blood is attachedl
62
ViaCord
- bank cord blood cells
63
benefits and Contributions of C. elegans
- easy to grow on agar plates and is a non-pathogenic roundworm
- composed of a limited number of cells (about 1000)
- translucent= can optically section through organism
- stable mutants of C. elegans are available for study
- all cells have been coded and differentiation predicted
- cell division/differentiation patterns can be predicted and always follow the same pattern
- RNAi first discovered in C. elegans
- the first apoptotic genes were first identified in C. elegans(Robert Horvitx won Nobel prize for this)--> many gees like the apoptotic genes have mammalian homologs
- first microRNA discovered (Victor Ambros and Gary Ruvkun
64
-Par proteins
- establish polarity in C. elegans
65
what happens when stem cells are liberated from the rest of the embryo
- give them a chance to figure out how to organize in a new environment
- figure out a new way to move, but they also figure out apparently a new way to reproduce by pushing cells together in a clump to make another C-shaped Xenobot
