Chapter 3: Stem Cells and Regenerative Medicine Flashcards
What are the three main classes of naturally occurring stem cells?
- Embryonic stem cells (ESC)
- Adult Stem Cells (ASC)
- Fetal/perinatal stem cells (FSC)
4th category - Induced pluripotent stem cells (IPSC)
What are the different types of potency of stem cells?
-** Totipotent** - Can differentiate into cells from each of the germ layer lineages (endoderm, mesoderm, ectoderm) as well as extra-embryonic tissue
-** Pluripotent** - Capacity to differentiate into cells from more than one germ layer lineage but NOT extraembryonic tissues
- **Multipotent **- Differentiation is restricted to the germ layer lineage from which they originate
What are some concerns regarding the use of embryonic stem cells?
- Ethical concerns regarding harvesting
- Tumorigenic potential (teratoma formation) when implanted into immune compromised adult animals
What are the three best-characterized cell line examples of adult stem cells?
- Haematopoietic stem cells
- Mesenchymal stem cells
- Neural stem cells (dentate gyrus of the hippocampus)
Where are perinatal stem cells harvested from?
-Umbilical cord
- Amniotic fluid
- Fetal membranes
These are multipotent but may have superior expansion potential, increased plasticity and superior immune privilege when compared to ASC
How are induced pluripotent stem cells generated?
By directly reprogramming adult somatic cells.
Retroviral and lentiviral vectors most commonly used
Adenoviral and sendai viral vectors have been successfully used for integration-free viral delivery
Where do mesenchymal stem cells reside?
In all adult somatic tissue in perivascular locations
What are the 2 morphologically diverse mesenchymal stem cell populations within a single colony?
- Small, rapidly self-renewing cells (RS cells)
- Larger, more slowly replicating cells
RS cells are superior at lineage-specific differentiation and predominate for the first 4-5 passages/replication cycles
List the 4 features which define a mesenchymal stem cell:
- Adheres to tissue culture plastic and exhibits a spindle-shaped appearance
- Form colonies of cells from single parent cells
- Express a specific set of surface marker proteins that exclude it from hematopoietic lineages
- Ability to differentiate into osteoblasts, adipocytes and chondrocytes (trilineage differentiation)
What features of mesenchymal stem cells make them excellent candidates for regenerative medicine?
- Can be isolated from adult tissues
- Undergo rapid, but not limitless, proliferation to produce massive numbers of cells
- Unlikely to induce an immune response when used in an autologous manner
- Produce a number of anabolic and anti-inflammatory agents (TSG-6, IL-1ra, PGE2)
What do canine mesenchymal stem cells (MSCs) require to undergo consistent, robust, osteogenic potential?
BMP-2
Where are mesenchymal stem cells (MSCs) most commonly isolated from in humans?
In animals?
Humans:
- Bone marrow aspirates
- Lipoaspirates
Animals:
- Bone marrow aspirates
- Enzymatic digestion of adipose tissue
What is a faster alternative to culture-expanded mesenchymal stem cells?
Unprocessed, minimally manipulated preparations of tissues that can be rapidly generated at point of care.
- Bone marrow concentrate (BMC)
- Stromal vascular fraction (SVC)
What are the options for mesenchymal stem cell (MSC) administration?
- Intravascular infusion (cytotherapy) - less than 5%of cells successfully migrate to location of injury and survive
- Direct implantation/injection (eg, seed onto a scaffold, intra-articular injection) ‘tissue engineering’
What are the main limitations/concerns regarding mesenchymal stem cell therapy in small animals?
- Gaps in knowledge
- Inherent variability in product
- Access to facilities and expertise
- Increasing federal oversight (FDA has banned in humans in many states)
- Unknown safety - May stimulate growth of neoplasms? Increased risk of infection?
- Administration of IV bolus has risk of microvascular embolization and ischemia
- Current lack of strong evidence
