ESCs are pluripotent cells that differentiate as a result of signaling mechanisms that can be replicated in vitro. 
​how?

and bringing it all together 

CRISPR and stem cells

CRISPR 

so approx. 662,000 embryos transferred resulting in 77,998 live births...
​what happened to the other
1/2  million + embryos?  

Clinical trials were recently announced to evaluate the ability of VX-880, a beta cell therapy derived from stem cells, to restore insulin production in individuals with type I diabetes. Building on the 2014 research(link is external) that established a new method for creating beta cells from stem cells, this clinical trial brings us closer to a cure for type I diabetes.

as you determine the future of stem cell research by whom you chose to elect with your votes, perhaps consider this ethical inconsistency...

Stem Cell Research

 Stem Cell Types:
​1. totipotent   2. pluripotent   3. multipotent

In a 2020 study, researchers reprogrammed a Parkinson’s patient’s skin cells into iPSCs and differentiated them into dopaminergic neurons lost by the disease. These replacement neurons were transplanted into the brain of the patient and after two years, were shown to be alive and functioning appropriately. The patient has begun to regain some daily function, prompting further investigation into this technique as a Parkinson’s treatment.

Jennifer Doudna
Professor of Chemistry and Molecular and Cell Biology at U.C. Berkeley.
developed a process for editing the DNA of any organism using an RNA-guided protein found in bacteria. This technology, called CRISPR-Cas9, has opened the floodgates of possibility for human and non-human applications of gene editing, including assisting researchers in the fight against HIV, sickle cell disease and muscular dystrophy. Doudna is an investigator with the Howard Hughes Medical Institute, senior investigator at Gladstone Institutes, and the Executive Director of the Innovative Genomics Institute. She is a member of the National Academy of Sciences, the National Academy of Medicine, the National Academy of Inventors, and the American Academy of Arts and Sciences. She is the co-author of A Crack in Creation, a personal account of her research and the societal and ethical implications of gene editing. She is a vocal proponent of its responsible use, first calling for a moratorium on using CRISPR technology to make permanent changes to the human germline in 2015.click on this pic for a video about CRISPR based therapeutics

scientists have isolated the Cas proteins and are able to use them along with manufactured RNA to target specific genes for editing. 

Stem Cells

in 2020:
there were 326,468* ART cycles performed at 449 reporting clinics in the United States resulting in 75,023 live births (deliveries of one or more living infants) and 79,942 live born infants. Of the 326,468 ART cycles performed in 2020, 123,304 were egg or embryo banking cycles in which all resulting eggs or embryos were frozen for future use. Although the use of ART is still relatively rare as compared to the potential demand, its use has more than doubled over the past decade. Approximately 2.0% of all infants born in the United States every year are conceived using ART. 
​https://www.cdc.gov/art/artdata/index.html

this is a blastocyst...
​it is the source of ESCs used in research

enhance regenerative medicine
​by regenerating and repairing diseased/damaged tissues including spinal cord injuries, diabetes, Parkinson's disease, ALS, Alzheimer's disease,
heart disease, stroke, burns, cancer and arthritis. Harnessing the potential for stem cells
to grow into new tissues provides options for tissue/organ transplants.

​The CRISPR-Cas9 system consists of two molecules that are capable of altering a DNA sequence.
1. The first is an enzyme called
 Cas9 = CRISPR associated endonuclease.
CAS9 functions like molecular scissors capable of cutting DNA. 
2. The second is a section of 
RNA called guide RNA.
gRNA is a piece of RNA with a specific sequence about 20 nucleotides long. 
The RNA binds to the DNA at a complementary sequence so that the Cas9 enzyme can cut the correct spot in the genome.

but when I googled embryo,
this pic is what first popped up...

In a small study, over half of patients with non-penetrating spinal cord injuries observed improved motor function within weeks of receiving an injection of stem cells derived from their bone marrow. This raises confidence in a clinical application of stem cells to treat spinal cord injuries, with clinical trials also exploring this possibility.

clinical applications

In patients with the “dry” form of age-related macular degeneration (AMD), clinical trials are currently underway to evaluate if transplanting retinal pigment epithelial (RPE) cells derived from iPSCs to replace those lost due to AMD can prevent further vision loss. In animal models, this therapy was shown to prevent blindness.

and challenges...

offer options for testing drugs for safety and effectiveness enhancing drug development. 
human stem cells are being programmed into tissue-specific cells to test new drugs.
​example: cardiac muscle cells could be generated to test a new drug for a cardiac disease
​to see if the drug had an effect on the cells and caused no harm.

1. Totipotent stem cells can form all the cell types in a body, plus the placental cells. Embryonic cells within the first couple of cell divisions after fertilization are the only cells that are totipotent.
2. Pluripotent stem cells can give rise to all of the cell types that make up the body; stem cells derived from the inner cell mass of a blastula are considered pluripotent.
3. Multipotent stem cells can develop into more than one cell type, but are much more limited than pluripotent cells; adult stem cells and cord blood stem cells are considered multipotent.

so again...
this is a blastocyst...
​it is the source of ESCs used in research

why does this matter??

  there isn't an 
  Ethical Consistency
between the unregulated use of embryos for IVF and the societal outrage when a few dozen discarded IVF embryos are used
to further stem cell research 

how do scientists recreate embryonic development in the lab?
 stem cells are exposed to chemical or physical signals that cause cellular differentiation including:
​
growth factors = signaling molecules that can be added to a growth medium to trigger
stem cells to transform into specialized cell types.
cell culture substrate = extracellular matrix proteins can be used as a frame on which
stem cells differentiate.
co-culture = cells can produce signaling molecules other cells respond to so stem cells
cultured with mature cells secreting growth factors can cause differentiation.
3D culture = stem cells are cultured in scaffolded "embryoid bodies" which recreate
gastrulation when the embryo's germ layers develop. 
signal inhibition = signals that might initiate an undesired differentiation can be
repressed using inhibitory growth factors.

How can science determine if the cell has fully differentiated?
1. appearance
2. gene activation
3. cell behavior

click on this pic for a video about CRISPR based therapeutics

 stem cell research is working to...

enhance our understanding of the nature of disease by discovering how stem cells mature
into heart muscle cells, bone cells, nerve cells etc.

Bacteria use special proteins called Cas proteins to protect against phage viruses. Cas proteins excise viral DNA which is then inserted into the bacterium's DNA.
​Next time the bacterium is attacked by the virus, it can destroy the virus using a Cas protein and the mRNA transcribed from the viruses DNA. 
The CRISPR arrays allow the bacteria to "remember"
​ the virus. 

               sources of research/therapeutic stem cells 
1. "adult" stem cells:
​found in small numbers in adult tissues like bone marrow and are  multipotent. adult stem cells were harvested from bone marrow more than 50 years ago. These blood-forming stem cells have been used in transplants for patients with leukemia and several other diseases for decades. In the 90s, nerve cells were regenerated adult stem cells. adult stem cells can be isolated from tissues and grown in cultures although they are relatively rare and difficult to isolate and culture.

​2. induced pluripotent stem cells ipsc's:
adult cells can also be altered to exhibit pluripotent characteristics. They are called induced pluripotent stem cells ipsc's. genetic reprogramming alters the genes in adult cells so they act like embryonic stem cells. researchers can use reprogrammed cells instead of embryonic stem cells which would prevent immune system rejection of the stem cells. research continues to see if these altered adult cells will cause adverse effects in humans. scientists have also taken connective tissue cells and reprogramed them to become heart cells. animal models with heart disease were injected with new heart cells, improving heart function.


3. perinatal stem cells:
researchers have discovered stem cells in amniotic fluid as well as umbilical cord blood. These stem cells also have the ability to change into specialized cells. amniotic fluid fills the sac that surrounds and protects a developing fetus in the uterus. Researchers have identified stem cells in samples of amniotic fluid drawn from pregnant women to test for abnormalities — a procedure called amniocentesis.

4. "embryonic" stem cells (ESCs);
arederived from blastocysts that develop 4 +/- days post fertilization. these blastocysts consist of 150 cells. the inner cell mass contains pluripotent stem cells.

in 2010:
330,773* ART (assisted reproductive technology) cycles with an average of 
2 embryos/cycle performed at 448 (reporting) clinics in the United States per year resulting in 77,998 live births  

PAM =
protospacer adjacent motif,
a DNA sequence 2-6 bp long
that follows the DNA region cleaved by CRISPR-Cas9.
PAM is required for the
nuclease to cut. It's located 
a few nucleotides downstream from the site targeted for cleavage.

scientists have isolated the Cas proteins and are able to use them along with manufactured RNA to target specific genes for editing.

​  A Research!America poll of U.S. adults conducted in partnership
with Zogby Analytics in January 2021. 
https://www.researchamerica.org/advocacy-action/issues-researchamerica-advocates/stem-cell-research

Stem cells have several promising clinical applications, providing hope in the fight against diseases and conditions that affect millions of Americans.
​ Below are some recent examples of these applications:

this is the CRISPR CAS9 system