Early Embryo and Stem Cells Flashcards
What is a stem cell? characteristics
a primitive cell that can either self-renew (reproduce itself) or give rise to more specialized cell types
single stem cells differentiate into multiple, functional cell types…functionally reconstitute a given tissue in vivo
what are the different classifications of stem cells and how are they different from each other
totipotency: give rise to all structures…zygote only
pluripotency: ability of a cell to give rise to all cells of embryo and subsequently adult tissues (but not extraembryonic cells)…embryonic stem cells
multipotency: ability of a cell to give rise to different cell types of a given lineage…adult stem cells
what are some avenues of stem cell research?
- identify drug targets and test potential therapeutics
- toxicity testing
- study cell differentiation -> understand prevention and treatment of birth defects
- tissues/cells for transplantation: bone marrow, nerve cells, heart muscle cells, pancreatic islet cells
what are the types of stem cells
adult stem cells/tissue specific stem cells germline stem cells (GSCs) fetal stem cells cord blood stem cells (CB-SCs) embryonic stem cells (ES/ESCs) induced pluripotent stem cells (iPSCs)
what is the role of adult stem cells?
- respond to demands of growth or repair - require restrictions on developmental potential
- proper tissue organization
may show relaxation of restrictions in an altered environment -> accounting for some plasticity (low frequency of this however)
where are adult stem cells found (type of environment)
kept in a nursed state in a “niche” - very sensitive to this area and the signals that occur here
ex: hematopoietic stem cells are kept in the bone marrow
what are the paths a stem cell can take?
stem cells can differentiate to precursor/progenitor cells -> differentiated cells (can also go in the reverse)
stem cells (also precursor/progenitor cells) can replicate themselves
they can undergo death (PCD) or senescence
describe hematopoietic stem cells
can be in a long term phase, short term phase (can differentiate from long term to short term or can self-renew) and then from short term go to multipotent progenitor cells and then differentiate to all of the blood cells
how do you get embryonic stem cells? characteristics?
derived from pluripotent cell population of 5 day old human embryos created during IVF before specialized tissues of the body begin to form…can grow indefinitely in culture in primitive embryonic state
- maintain normal karyotype
- retain pluripotency
- can differentiate into all somatic cells and germline tissues
what are some reasons FOR using human blastocyst cells? and what cells are used?
- body plan not yet apparent
- many cells will not form human, but instead tissues that will support pregnancy
- not necessarily a unique individual (twining up to 14 days)
- no nervous system
- not possible to predict a term pregnancy
cells: inner cell mass
what is a result of cell interactions between pluripotent cells and extra-embryonic stem cells?
embryonic stem cells give rise to disorganized growths called teratomas without these cell interactions
ES cells on their own are incapable of generating the body plan
in vitro, can just spontaneously go down different differentiation paths even though they are in the same dish
what is the difference between adult and embryonic stem cells?
cannot return adult stem cells back to embryonic stem cell status -> epigenetic factors, mutations, etc.
both sources of stem cells should be pursued simultaneously because they each offer the potential for cures and are not replacements for one another
adult advantages: immune response is unlikely because patients are using their own cells, available, partially specialized
adult disadvantages: limited longevity, difficult in maintain in culture, difficult to find and extract from mature tissues, many unknowns, multipotent, uncommon and grow more scarce with age, genetic defects
embryonic advantages: immortal, easy to extract in a lab, pluripotent, readily available, immune rejection is not normally an issue (SCNT - somatic nuclear transfer)
embryonic disadvantage: immune rejection if use IVF, difficult to control/get it to differentiate to what you want
what are the two main strategies for generating patient-specific cells?
- induced pluripotent stem cells - patient derived
- induced pluripotent stem cells/embryonic stem cells - non-patient derived
primary cells can be reprogrammed or ESCs/iPSCs can be differentiated directly
what are challenges for regenerative medicine and transplantation therapy?
- production of required cell type in sufficient numbers and pure form
- what cell to transplant
- delivery and proper integration
- problems of tissue/immune rejection: Graft vs host disease
- embryonic or fetal derived grafts may be immunogenic
- some transplantation sites may be immunologically privileged
what are solutions to the rejection problem?
- large banks of ES cell lines
- replacement of hematopoietic/lymphoid tissue prior to transplant
- manipulation of T cell response with antibodies or drugs
- somatic cell nuclear transfer stem cells
- manipulation of histocompatibility genes in ES cells
