Module 4 Multipotent Stem Cells

Question 1

What are mesenchymal stem cells?

Answer 1

Multipotent stem cells found in bone marrow that are important for making and repairing skeletal tissue. Also play an important role in maintaining environment of the bone marrow along with assisting in the immune response. Note that these also begin to decrease as we age.

Question 2

What are adult stem cells?

Answer 2

Undifferentiated multipotent stem cells that reside in differentiated tissues.

Question 3

Autologous vs allogenic MSC therapy?

Answer 3

Autologous: self donation, own MSC can be the reason for their disease, long time.
Allogeneic: Donated MSC, immediate use, cells can be selectively derived from young donors.

Question 4

What are satellite cells?

Answer 4

They are myogenic (muscle) stem cells that help with muscle regeneration throughout the lifespan.

Question 5

What is Duchenne muscular dystrophy?

Answer 5

X-linked disease that is most common form of MD that primarily affects boys due to absence of dystrophin, a protein involved in in the integrity of the muscle.
Signs: Swayed back, weak butt muscles, shoulder and arms held back, thin weak thighs.

Question 6

What is dystrophin?

Answer 6

Anchor-type protein that sits just inside muscle cell membrane and tethers structural proteins inside the cell to the proteins that sit in outer surface of cell membrane.

Question 7

Name the different approaches to treat DMD?

Answer 7

Myoblasts: Clinical trials in 1991 but other studies show mixed results in improving muscle strength. You also have to do these injections all over the body.

Satellite cells: Precursor population that can differentiate into myoblasts and repair muscle fibers or self renew and remain dormant awaiting muscle regeneration. Problem: small number of satellite cells can be extracted from biopsies and not easy to expand in culture.

MSC’s: Works but is limited in muscle regeneration

ES and IPs: Powerful as it can make any cells but ethical concerns and fear of tumor.
Stem cell scaffold will be vital for all these approaches to rebuild muscle

Question 8

Chondrocytes come from which germ layer and form what 3 types of cartilage?

Answer 8

The mesodermal origin.
1. Hyaline (articular) cartilage: Found in joints, rib cartilage, nose, and trachea.
2. Elastic cartilage: Found in ear, epiglottis, and larynx.
3. Fibrous: Found in intervertebral discs.

Question 9

Describe the components and composition of articular cartilage

Answer 9

Majority is a matrix made up of water with remaining solid materials:
Collagen: Resist shear stress and give structure and tensile strength
Proteoglycans and proteins: Shock absorbers
Chondrocytes: Cells that produce ECM for development and maintenance.

Question 10

Define osteophyte

Answer 10

bony outgrowth associated with the degeneration of cartilage at joints

Question 11

Describe the composition of bone

Answer 11

60% weight of bone is mineral (calcium and phosphate) and the rest is water and matrix, with the matrix proteins being collagen to provide strength.

Question 12

Describe the bone remodeling cycle

Answer 12

Osteoclasts perform bone resorption (removing bone to be replaced)> reversal stage> osteoblasts perform bone formation (ossification) > osteocytes and mineralization. It’s believed that osteoporosis has an uneven relationship with osteoblasts and osteoclasts.

Question 13

Describe phase of bone’s natural healing process

Answer 13

Reactive phase: Blood cells migrate to tissue surrounding fracture and constrict to stop bleeding.

Reparative phase: Periosteal cells close to fracture develop into chondroblasts to form hyaline cartilage while periosteal cells furthest from fracture turn into osteoblasts to form bone. The 2 tissues grow unite and is replaced with lamellar bone and finally with trabecular bone.

Remodeling Phase: Trabecular bone undergoes bone remodeling phase and becomes compact bone.

All around can take 3-5 years.

Question 14

Properties of bone grafting

Answer 14

Graft osteogenesis: Cellular events within a donor graft which survive transplantation and synthesize new bone at recipient site.

Graft osteoinduction: New bone formation through active recruitment of host MSC from surrounding tissue. Facilitated by growth factor Bone Morphogenetic Proteins (BMPs).

Graft osteoconduction: Facilitation of blood-vessel incursion and new bone formation into graft structure.

Question 15

Properties of ideal bone-graft

Answer 15

Biocompatible, bioresorbable, osteoconductive, osteoinductive, structurally similar, and cost-effective

Question 16

Describe the bone marrow microenvironment

Answer 16

Niches: Local tissue microenvironments that maintain and regulate stem cells.
Hematopoiesis: Formation of blood and cellular components provides a model for understanding mammalian stem cells and their niches.

Question 17

What are HSCs and why are they important?

Answer 17

Hematopoietic stems cells are multipotent stem cells that give rise to cells of both the blood and immune cell lineage. As these HSCs are found mostly in the bone marrow, understanding the HSC niche helps in improving regeneration following injury or transplantation.

Question 18

Describe the composition of blood

Answer 18

55% is plasma (water with proteins that help with electrolyte balance and infection resistance)
45% is erythrocytes (RBC)
1% is leukocytes (WBC) and platelets (thrombocytes)

Question 19

What are the 3 important proteins in plasma that help with electrolyte balance and protect the body from blood infections and disorders

Answer 19

Albumin, Globulin, Fibrinogen

Question 20

What is serum in blood?

Answer 20

Clear yellowish fluid that remains from blood plasma after clotting factors have been removed (fibrinogen).

Question 21

Remember the blood types and reasons on who can donate to who?

Answer 21

Are you a blud?

Question 22

What was the niche hypothesis

Answer 22

Femur contained marrow cavities where primitive cells tend to localize.
Trabeculae: Minute projection of bone are found throughout the metaphysis so many cells are close to the bone surface.
Endosteum: Interface of bone and marrow and contains osteoblasts and osteoclasts. Arteries carry oxygen, nutrients, and growth factors into bone marrow before feeding the sinusoids.

Question 23

What are the two distinct niches that reside in the bone marrow?

Answer 23

Endosteal niche: Outer edge of bone marrow containing osteocytes, bone matrix, and HSCs.
Perivascular niche: Inner core of bone marrow with actively diving HSCs, sinusoidal endothelium, and MSCs.

Question 24

What occurs when bone marrow is damaged or diseased?

Answer 24

It’s likely individuals develop blood or autoimmune disease, and/or cancer. Examples include Leukemia, Lymphoma, and Myeloma.

Question 25

What is Leukemia? (Symptoms and Causes)

Answer 25

Bone marrows greater abnormally large number of immature white blood cells that don’t function called blasts cells or blasts. This causes the white blood cells not able to fight infection and impairs the ability of the bone marrow to produce other import blood lineage cells

Symptoms: Being ill, anemia, and excessive bleeding.

Possible causes: Radiation/toxin exposure, viruses, genes, chemicals.

Acute vs Chronic: Acute gets worse quickly while chronic gets wore slowly.

Question 26

Name the types of leukemia

Answer 26

Chronic lymphocytic leukemia: Abnormal transcription factors affecting development of B and T cells (affects children).
Chronic myeloid leukemia: Chromosomal deletion or somatic hypermutation (affects adults, twice in men)
Acute lymphocytic leukemia: Oncogenic mutations leading to accumulated immature myeloid blasts (affects adults)
Acute myeloid leukemia: Tyrosine kinase pathway (affects 20-50, rare in children).

Question 27

What is myeloma?

Answer 27

Blood cancer that targets plasma cells and prevent normal production of antibodies. Myeloma cells results in production of abnormal antibodies, or M proteins which offer no benefit to the body and outcrowd functioning antibodies.

Diseased plasma cells exploit normal bone marrow microenvironment for their survival.

Question 28

What is lymphoma?

Answer 28

Cancer that occurs when lymphocytes (T cells, B cells, NK cells) proliferate in an uncontrolled manner. The abnormal lymphocytes clump together and form a mass in the lymph nodes or other organs of the lymphatic system.

Question 29

Hodgkin lymphoma vs Non-Hodgkin lymphoma?

Answer 29

Hodgkin Lymphoma:
-One of the most curable types of cancer as predictable pattern of growth (one lymph node to another)
-Reed-Sternberg cells help distinguish Hodgkin from other types of lymphoma.
- Rarely found outside of the lymph nodes

Non Hodgkin Lymphoma:
-30 types and can be classified by the types of lymphocytes affected.
-NHL frequently exists anywhere/distributed throughout the body.

Question 30

What is cancer cell dormancy?

Answer 30

Cancer cells enter an state of quiescence or dormancy which makes therapeutics targeting high proliferation not effective and these can be activated at a later time and cause recurrence. Given cancer deaths occur after 5 year of survival, it’s been an effort to stimulate the quiescent endosteal niche to the more active perivascular niche.

Question 31

Describe Cancer Hijack of MSCs in the bone marrow

Answer 31

MSCs and immune cells are recruited to tumors through inflammatory chemokines and their recruitment helps promote vascularization, tissue remodeling and immune responses. They also differentiate into supportive stromal cells to support this tumor microenvironment. However, due to their unique homing ability, this can be a good option for therapeutic modifications.

Question 32

What is umbilical cord blood and what 2 cell types of stem cells were identified in it?

Answer 32

Blood that remains in fetal portion of placenta and in the attached umbilical cord after childbirth. Cord blood contains stem cells that can treat hematopoietic and genetic disorders. The placenta helps transfer nutrients and oxygen from mothers blood to fetal blood.

MSCs and HSCs

Question 33

What is GVHD?

Answer 33

It’s Graft vs Host Disease and is the massive immune attack that results from HLA mismatch. GVHD itself can kill you and with it being so immunosuppressive, it’s predispose their patients to life threatening infections.

Question 34

Pros and Cons of storing umbilical cord blood

Answer 34

Pros:
No donor risk
Stored indefinitely and rapid availability
Increased ethnic diversity of donor pool
High proliferative potential

Cons:
Private companies began to overtake public companies offering it for free and now has made it costly.
Child’s own cord blood would rarely be suitable for transplant back to the individual today as the cord blood stem cells carry the same condition to the recipient and can’t treat genetic diseases.
AAP and Obstetricians and Gynecologic have declared use of cord blood as biological insurance to be unwise.
Lots of misinformation about cord blood successfully treating things such as Alzheimer’s Parkinson’s, spinal cord injuries.

Rando fact: Each child shares one of its 2 HLA genes with each parent

Question 35

What is peripheral blood stem cells?

Answer 35

It’s today’s standard of care and use GCSF (granulocytes colony stimulating factor) to stimulate release of stems cells in bone marrow to circulating (peripheral blood). Alongside this, physicians can take enough cells for 2 transplants incase the first one doesn’t work. They don’t use banked cord blood cells as it’s usually not enough cells and unknown about the quality of collection.

Question 36

Why is cell dosage important?

Answer 36

Generally with donor engraftments, it’s more successful when patients receive a lower number of cells that go below cell dose threshold in comparison to larger number of cells, which can be deadly, especially for pediatric patients. However, it’s also important to improve the number of cord blood cells available for adult cord blood transplantation.

Question 37

What are 2 types of cells in the nervous tissue?

Answer 37

Neurons: Excitable nerve cells that transmit electrical signals. Live for 100 years and don’t divide.
Glial (Supporting cells) : “Nerve glue”

CNS:
astrocytes: metabolism and synapse formation
oligodendrocytes: produce myelin sheaths in CNS
microglia: phagocytes
ependymal cells: lines the cavity of CNS and spinal cord: cilia

PNS:
Schwann cells: Form myelin in PNS
satellite cells: surround neuron cell body and gas and nutrient exchange

Question 38

What are clusters called in the CNS vs the PNS?

Answer 38

CNS: nuclei
PNS: ganglia

Question 39

What are the 3 things neurons can synapse with?

Answer 39

Neurons, muscles, and glands.

Question 40

Oligodendrocytes vs Schwann cells?

Answer 40

Schwann (PNS) wrap themselves around a single segment of axon’s myelin sheath while oligodendrocytes (CNS) wrap around numerous axons at once. (Google image for refresher).

Question 41

Gray vs White matter of CNS?

Answer 41

Gray matter: Neuron cells bodies are clustered.
White matter: Millions of axons running between different parts of CNS, in bundles of ‘tracts’. The white comes from myelin sheaths.

Question 42

Name the types of nerves

Answer 42

Nerves are bundles of nerve fibers (long axons) in connective tissue
Mixed: Carry both sensory (afferent) and motor (efferent fibers). Ex. spinal nerves
Sensory or afferent nerves: to CNS
Motor or efferent nerves: ventral roots of spinal cord.

Question 43

What are purkinje cells?

Answer 43

Large neurons with many branching extensions found in the cerebellum that help control motor movement. They release neurotransmitters that have inhibitory actions on nerve impulses, allow these cells to regular and coordinate motor movements.

Question 44

What are the approaches for peripheral nerve injuries?

Answer 44

It’s better that during an injury to neurons that distal portions like the axon are damaged rather than close to neuron body as they can undergo a good amount of regeneration.
1. Suturing severed peripheral nerves
2. Autologous nerve grafts (autographs)
3. Artificial scaffolds and substrates to guide natural regeneration

Question 45

What are nerve guides?

Answer 45

They’re the tubes use to bridge the stumps of damaged nerves together. They’re usually filled with fluid and cytokines to promote regeneration. They however have a critical gap length where successful regeneration will occur 50% of the time. Things that increase this critical gap length are adding Schwann cells, making them out of degradable collagen, introducing a collagen GAG-matrix.

Question 46

Examples of Neurodegenerative diseases:

Answer 46

Parkinson’s Disease: Disorder of the CNS as a result of death of dopamine generating cells in region of the midbrain.
Alzheimers Disease: Hyperphosphorylated tau proteins pair with other threads of tau that form protein tangles in nerve cell bodies and disintegrate microtubule and collapse neuron’s transport system.
Huntington’s Disease: Gene mutation that leads to toxic accumulation of protein in the brain and destroy cells in the basal ganglia.
Multiple Sclerosis (MS): Inflammatory disease which myelin nerve cells in brain and spinal cord are damaged and therefore inhibit nervous system communication.
ALS: Motor neurons>spinal cord>muscles. ALS degenerates motor neurons and therefore brain is unable to control muscles.