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Embryonic Stem Cells – Definition, Properties, Applications

What is Embryonic Stem Cell?

  • Embryonic stem cells (ESCs) are pluripotent cells originating from the inner cell mass of the blastocyst, an early developmental stage of the embryo that emerges 4-5 days post-fertilization. At this juncture, the embryo comprises 50-150 cells.
  • The process of extracting the inner cell mass, termed embryoblast, necessitates the use of immunosurgery, leading to the obliteration of the blastocyst. This procedure has ignited ethical debates, particularly concerning the moral status of pre-implantation embryos in comparison to post-implantation stages.
  • Embryonic stem cells possess a unique capability: they can differentiate into any cell type within an organism, a phenomenon termed cellular differentiation.
  • This intrinsic property is vital during embryonic development, as cells transition from a generalized state to specialized roles, culminating in the formation of diverse organs, tissues, and systems. The initial cell formed post-fertilization, when the sperm merges its DNA with an egg (oocyte), is known as a zygote. This cell is, in essence, an embryonic stem cell, as its subsequent divisions will give rise to the entirety of the organism’s cellular constituents.
  • The zygote and its immediate progeny possess the potential to differentiate into any tissue type, even having the capacity to form a complete organism. A case in point is identical twins, which arise from a single zygote that inadvertently divides during its initial stages of cell division.
  • The scientific community is fervently exploring the therapeutic prospects of embryonic stem cells. Many laboratories are striving to harness these cells for clinical applications, with potential treatments targeting ailments such as diabetes and heart disease.
  • Beyond therapeutic interventions, embryonic stem cells are also being investigated as models for genetic disorders and avenues for cellular and DNA repair. Nonetheless, it’s imperative to note that the research trajectory has encountered challenges, including the manifestation of tumors and undesirable immune reactions.
  • In summation, embryonic stem cells are pivotal entities in developmental biology, holding immense potential for therapeutic applications, albeit accompanied by ethical considerations and scientific challenges.

Definition of Embryonic Stem Cell

Embryonic stem cells (ESCs) are pluripotent cells derived from the inner cell mass of a blastocyst, an early-stage embryo, capable of differentiating into any cell type within an organism.

History of Embryonic Stem Cell

The history of embryonic stem cells (ESCs) is marked by pioneering discoveries and significant milestones that have shaped the trajectory of stem cell research. Here is a chronological overview of the key events in the history of embryonic stem cells:

  1. 1964: Lewis Kleinsmith and G. Barry Pierce Jr. isolated cells from a teratocarcinoma, a tumor derived from germ cells. These cells, termed embryonal carcinoma (EC) cells, exhibited stem cell properties. However, these cells had genetic mutations, emphasizing the need to culture pluripotent cells directly from the inner cell mass.
  2. 1981: Two independent groups, one led by Martin Evans and Matthew Kaufman at the University of Cambridge and the other by Gail R. Martin at the University of California, San Francisco, successfully derived embryonic stem cells from mouse embryos. Martin coined the term “Embryonic Stem Cell.”
  3. 1989: Mario R. Cappechi, Martin J. Evans, and Oliver Smithies introduced the concept of “knockout mice” by isolating and genetically modifying embryonic stem cells. This innovation provided a novel method to study diseases.
  4. 1996: The Roslin Institute at the University of Edinburgh achieved a significant breakthrough by cloning Dolly, the first mammal cloned from an adult cell. This experiment demonstrated the potential of specialized adult cells to revert to a pluripotent state.
  5. 1998: A team from the University of Wisconsin, Madison, led by James A. Thomson, derived the first human embryonic stem cell lines. They highlighted the cells’ pluripotency and self-renewal capabilities, marking a pivotal moment in stem cell research.
  6. 2001: President George W. Bush permitted federal funding for research on approximately 60 pre-existing embryonic stem cell lines, ensuring that no new embryos were destroyed using federal funds.
  7. 2006: Japanese scientists Shinya Yamanaka and Kazutoshi Takashi introduced induced pluripotent stem cells (iPSCs) by reprogramming adult mouse fibroblasts. iPSCs, resembling embryonic stem cells but without the associated ethical concerns, represented a significant advancement in the field.
  8. January 2009: The US Food and Drug Administration (FDA) approved the phase I trial of Geron Corporation’s human embryonic stem cell-derived treatment for spinal cord injuries. This treatment was derived from cell lines sanctioned under President George W. Bush’s policy.
  9. March 2009: President Barack Obama signed Executive Order 13505, lifting the restrictions on federal funding for human embryonic stem cell research. This order mandated the National Institutes of Health (NIH) to revise federal funding guidelines for stem cell research.

In summary, the journey of embryonic stem cell research has been marked by groundbreaking discoveries, ethical debates, and regulatory shifts. From the initial isolation of cells from teratocarcinomas to the derivation of human embryonic stem cell lines and the introduction of iPSCs, the field has witnessed rapid advancements that hold promise for regenerative medicine and therapeutic applications.

Properties of Embryonic Stem Cell

Embryonic stem cells (ESCs) are unique cells with distinct characteristics that set them apart from other cell types. Here are the primary properties of embryonic stem cells:

  1. Pluripotency: ESCs are pluripotent, meaning they have the ability to differentiate into any cell type derived from the three primary germ layers: ectoderm, endoderm, and mesoderm. This allows them to give rise to over 220 different cell types present in the adult human body.
  2. Self-Renewal: One of the defining characteristics of ESCs is their capacity for self-renewal. They can replicate themselves indefinitely under appropriate conditions while maintaining their undifferentiated state.
  3. Normal Karyotype: ESCs maintain a normal chromosomal arrangement, ensuring their genetic stability over prolonged periods of culture.
  4. High Telomerase Activity: ESCs exhibit elevated telomerase activity, which contributes to their long-term proliferative potential and prevents premature cellular aging.
  5. Rapid Growth Dynamics: The cell cycle of ESCs is characterized by a shortened G1 phase, leading to frequent cell divisions. This rapid proliferation is essential for early embryonic development.
  6. Regulated by Pluripotency Factors: Certain transcription factors, such as Oct4 and Nanog, play crucial roles in maintaining the pluripotent state of ESCs and regulating their cell cycle.
  7. Therapeutic Potential: Due to their pluripotency and self-renewal capabilities, ESCs hold significant promise for regenerative medicine, offering potential treatments for various diseases and injuries.
  8. Research Utility: Beyond therapeutic applications, ESCs are invaluable tools for scientific research, especially in studying early human development, genetic disorders, and for in vitro toxicology testing.

In essence, the pluripotency and self-renewal capabilities of embryonic stem cells, combined with their genetic stability and rapid growth dynamics, make them a focal point in both scientific research and potential medical applications.

Approaches to human embryonic stem cell derivation

Human embryonic stem cells (hESCs) have been at the forefront of regenerative medicine due to their potential to differentiate into any cell type in the human body. The derivation of these cells, however, has been a subject of scientific, ethical, and political debate.

  1. Initial Derivation from Blastocysts: In 1998, Thomson et al. achieved a significant milestone by isolating hESCs from the inner cell mass (ICM) of preimplantation human blastocysts. This method, while revolutionary, raised ethical concerns as it necessitated the destruction of a human embryo.
  2. Federal Funding and Ethical Concerns: Recognizing the potential of hESC research, the Bush administration in 2001 permitted federal funding for research on pre-existing hESC lines, establishing the NIH hESC registry to monitor approved lines. This decision aimed to balance the potential of hESC research with ethical concerns surrounding embryo destruction.
  3. Characteristics of hESCs: hESCs, like ICM cells, possess the ability to differentiate into all human body tissues. They express specific markers of pluripotency, including transcription factors Oct-4, NANOG, Rex-1, and cell surface antigens SSEA-3, SSEA-4, TRA-1-60, and TRA-1-81. These cells can self-renew indefinitely under appropriate culture conditions and can form teratomas when injected into immunodeficient mice.
  4. Traditional Derivation Methods: The conventional method involved deriving ESCs from day 5-7 blastocysts, typically using a feeder layer of mitotically inactivated mouse embryonic fibroblasts. This method, however, raised concerns about potential contamination with animal products.
  5. Alternative Approaches: To address ethical and safety concerns, researchers have explored alternative methods for hESC derivation:
    • Human Feeders and Feeder-Free Matrices: Newer methods have eliminated the use of mouse feeder cells, opting for human feeders or feeder-free matrices to avoid potential xenovirus contamination.
    • Derivation from IVF Embryos and Unfertilized Oocytes: Some hESCs have been derived from growth-arrested IVF embryos and unfertilized oocytes, which cannot form developmentally competent embryos.
    • Single Blastomere Derivation: A promising technique involves deriving hESCs from a single blastomere of a morula stage embryo, leaving the embryo unharmed. This approach addresses the ethical concerns of embryo destruction.
    • Parthenote hESCs (hPESC): Derived from chemically activated unfertilized oocytes, hPESCs are similar to ICM-derived hESCs in morphology, growth behavior, and pluripotency markers. They offer potential advantages in immune compatibility and ethical acceptability.
    • Somatic Cell Nuclear Transfer (SCNT): This technique involves transferring the nucleus of a donor cell into an enucleated unfertilized egg, leading to the formation of a blastocyst. ESCs derived from such blastocysts would be genetically identical to the nucleus donor, offering potential for autologous transplants.
  6. Naïve hESCs: Recent advancements have introduced the concept of “naïve” hESCs, which exist in a more primitive state compared to the “primed” hESCs typically derived. Naïve hESCs have unique properties, such as better survival after single cell dissociation and more efficient differentiation capabilities.

In conclusion, the derivation of human embryonic stem cells has evolved significantly since the initial isolation from blastocysts. While the potential of these cells in regenerative medicine is undeniable, the methods of derivation continue to be refined to address ethical, safety, and efficiency concerns.

Maintenance of human embryonic stem cell

Human embryonic stem cells (hESCs) are derived from the inner cell mass (ICM) of blastocysts and possess the unique ability to differentiate into any cell type in the human body. However, maintaining their pluripotency in vitro presents a significant challenge, given their natural inclination to differentiate once they reach a certain density or “critical mass.”

  1. Culture Conditions: To sustain hESCs in their pluripotent state, culture conditions have been meticulously optimized. These conditions aim to inhibit spontaneous differentiation and ensure the cells remain undifferentiated across numerous passages.
  2. Feeder Systems: Historically, mouse embryonic fibroblasts or human fibroblasts sourced from various tissues have been employed as feeder layers to support hESC growth. The associated medium typically comprises Knockout-DMEM (KO-DMEM) and Knockout Serum Replacement (KSR), further supplemented with human bFGF. Variations might include the addition of Plasmanate or a mix of KO-DMEM and F12 medium. On these feeders, hESCs exhibit a distinct morphology, characterized by well-defined colonies of compact, epithelial-like cells.
  3. Feeder-Free Systems: With advancements in stem cell research, feeder-free systems have been developed to eliminate the reliance on animal-derived feeder layers. These systems utilize matrices like Matrigel, a dilute solution derived from mouse sarcoma cells, or CellStart, an extracellular matrix derived from human placenta. While these systems offer a more defined environment, they may sometimes result in hESCs that appear more spread out. Nevertheless, these cells maintain their pluripotent properties.
  4. Defined Culture Systems: For clinical applications, it’s preferable to avoid animal-derived components in hESC culture. Several commercial systems now offer animal-free media and matrices. Examples include Nutristem, TeSR2, and StemFit media, as well as laminin, iMatrix, and Vitronectin matrices. These xeno-free systems are more compatible with clinical applications, ensuring that hESC derivatives are more amenable for therapeutic use.
  5. Challenges in hESC Maintenance: One of the primary challenges in maintaining hESCs is their propensity to differentiate once they reach a certain density in culture. This intrinsic characteristic necessitates constant monitoring and optimization of culture conditions to ensure pluripotency is retained.

In summary, the maintenance of human embryonic stem cells in vitro requires a delicate balance of conditions to ensure their pluripotency is preserved. With the advent of xeno-free and defined culture systems, the field is moving closer to generating hESC lines that are suitable for clinical applications in regenerative medicine.

Subculture of human embryonic stem cell

Human embryonic stem cells (hESCs), derived from the inner cell mass (ICM) of a developing blastocyst, possess the intrinsic ability to differentiate into derivatives of the three germ layers. While this characteristic makes hESCs a valuable resource for regenerative medicine, it also presents challenges in their maintenance in vitro. The natural inclination of hESCs to differentiate, especially when colonies reach a particular size, necessitates careful subculturing techniques to ensure their pluripotency.

  1. Spontaneous Differentiation: hESCs have a propensity to spontaneously differentiate, especially when colonies attain a specific size. This differentiation is influenced by the microenvironment and the intricate cell-cell and cell-matrix interactions. Timely passaging can disrupt these interactions, allowing the cells to remain in a pluripotent state and continue their self-renewal process.
  2. Mechanical Dispersion: Historically, mechanical colony dispersion and hand-picking have been the preferred methods for subculturing hESCs. This approach allows for the selection of colonies with the correct morphology, minimizing cellular stress. However, this method requires skilled operators, as there’s a risk of selecting aneuploid cells that proliferate rapidly. It’s essential to handle cells with care, especially when they are grown in feeder-free systems, as these colonies tend to be more fragile.
  3. Enzymatic Dissociation: For large-scale cultures, especially in therapeutic applications, enzymatic dissociation is more efficient than mechanical methods. Various enzymes, including collagenase, accutase, trypsin, TrypLE, and EDTA, are employed to dissociate hESCs into single cells or small clumps. However, this method can inadvertently promote clonal aneuploidy, as the distribution might include aneuploid cells. This propensity underscores the importance of routine karyotyping during the subculturing process.
  4. Karyotyping: Given the tendency of hESCs to undergo clonal aneuploidy, it’s crucial to perform routine karyotyping during subculturing. Techniques such as G-banding, examining a minimum of 20 cells, or fluorescence in situ hybridization (FISH) targeting chromosomes 12 and 17 on at least 200 cells, are recommended. These chromosomes are particularly significant as the gain of extra copies often provides aneuploid hESCs with a growth advantage.

In conclusion, the subculture of human embryonic stem cells requires meticulous techniques to ensure the maintenance of their pluripotent state. Both mechanical and enzymatic methods have their merits and challenges, but the overarching goal is to prevent unwanted differentiation and ensure the stability of the hESC genome.

Selecting Embryos For Producing Embryonic Stem Cells

The process of deriving human embryonic stem cells (hESCs) is contingent upon the judicious selection of human embryos. The criteria adopted for this selection play a pivotal role in determining the success rates of hESC derivation.

  1. Developmental Potential: The developmental potential of an embryo is a crucial factor in its selection. Embryos with higher developmental potential are more likely to yield successful hESC lines.
  2. Fresh vs. Frozen Embryos: Comparative studies have shown that fresh, non-frozen embryos are more efficient for hESC derivation than their frozen-thawed counterparts. For instance, in a study conducted by Reubinoff et al. (2000) and Trounson (2001a), twelve selected fresh blastocyst-stage embryos, cultivated in coculture with human fallopian tube epithelial cells, resulted in the production of six ESC lines. This success rate was notably high, especially when juxtaposed with the outcomes from larger numbers of frozen embryos, which are typically donated post-IVF treatments.
  3. Mosaic Human Blastocysts: An innovative approach involves the construction of mosaic human blastocysts. These are formed by aggregating uninuclear cells from poor-quality embryos, which would traditionally be discarded due to their diminished developmental potential. However, the genomic variations in these mosaic embryos could curtail their utility in hESC derivation.
  4. Embryos with Genetic Anomalies: Recent advancements have seen the derivation of hESC lines from embryos with specific genetic mutations or chromosomal abnormalities. These embryos are identified through preimplantation genetic diagnosis (PGD). Examples include embryos with genetic markers for Huntington’s disease, cystic fibrosis, thalassaemia, Fanconi anaemia A, fragile X syndrome, and Duchenne muscular dystrophy. Such hESC lines are invaluable for studying disease differentiation and function both in vitro and in vivo. Furthermore, they provide a platform for screening molecular libraries to identify potential drugs that could modulate the expression of the disease phenotype.

In conclusion, the meticulous selection of embryos is paramount for the successful derivation of hESCs. While fresh embryos have shown higher efficiency, the exploration of embryos with genetic anomalies offers a promising avenue for disease research and potential therapeutic interventions.

Pluripotential Markers Of Embryonic Stem Cells

Embryonic stem cells (ESCs) possess the unique ability to differentiate into various cell types, a characteristic known as pluripotency. To identify and validate the pluripotential nature of these cells, specific markers are employed. These markers are essential proteins or genes that are expressed in pluripotent cells.

  1. Transcription Factors:
    • POU5F1 (Oct4): A pivotal transcription factor, Oct4 is highly expressed in pluripotential human ESCs, embryonal carcinoma cells (ECC), and seminomas. It plays a crucial role in maintaining the pluripotent state of stem cells.
    • Sox2: Another transcription factor, Sox2, is vital for pluripotency and is abundantly expressed in ESCs.
    • Nanog: This transcription factor is essential for maintaining the self-renewal capabilities of ESCs.
    • Foxd3: A member of the forkhead family, Foxd3 interacts with Oct4 and is vital for the maintenance of primitive ectoderm in mice.
    • Rex1 and UTF1: These are additional transcription factors associated with pluripotency.
  2. DNA Modifiers:
    • DNMT3B: This DNA methylase plays a role in early embryogenesis.
    • TERF1, CHK2: These are other DNA modifiers linked to pluripotency.
  3. Surface Markers and Growth Factors:
    • GFA1: A recognized surface marker.
    • GDF3: A growth factor associated with pluripotency.
    • TDGF1: A receptor linked with pluripotency.
    • Stella and FLJ10713: Other markers indicative of pluripotency.
  4. Characterization Markers:
    • Stage-specific embryonic antigens (SSEA)-3 and -4: These antigens are commonly used for hESC characterization.
    • hESC antigens: These include TRA-1-60, TRA-1-81, GCTM-2, TG-30, and TG-343.
    • Other markers: CD9, Thy1, and major histocompatibility complex class 1 are also reported for hESC characterization.
  5. Heterogeneity in Marker Expression: It’s crucial to note that not all cells within an ESC colony express these markers uniformly. For instance, only a subset of cells expressing GCTM-2 and negative for TG-30 also express Oct4 protein.
  6. Other Stem Cell Antigens: Some antigens, such as AC133, c-kit (CD117), and flt3 (CD135), are expressed only in a fraction of the hESC population. These markers might indicate specific subpopulations within the heterogeneous hESC population.
  7. Oct4 Expression Considerations: While Oct4 is a significant marker, its presence alone might not be definitive proof of pluripotency. Oct4 expression persists for a while even in differentiating hESC and is also found in other pluripotent cell populations.

Genetic Manipulation Of Embryonic Stem Cells

Embryonic stem cells (ESCs) hold immense promise for regenerative medicine due to their ability to differentiate into diverse cell lineages. Harnessing this potential necessitates precise control over their differentiation pathways, ensuring they yield the desired cell types without forming unwanted tissues, such as teratomas.

  1. Challenges in Cell Identification:
    • Monitoring the differentiation of specific cell types in culture can be challenging. Often, early stages of differentiation don’t exhibit distinct morphological changes.
    • Current identification methods are reliant on labor-intensive techniques like immunological assays and reverse transcriptase polymerase chain reaction (rtPCR) to detect specific markers.
  2. Separation of Desired Cells:
    • If the differentiated cells are intended for transplantation, it’s crucial to isolate them from a mixed cell population. This ensures that only the desired cell type, free from contaminants, is used for therapeutic applications.
  3. Genetic Modification Techniques:
    • Clonal Derivation: Achieving clonal derivation of ESCs is intricate, making the efficiency of homologous recombination for gene “knock-in” or “knockout” quite low.
    • Fluorescent Gene Tags: Recent advancements have enabled the tagging of genes of interest with fluorescent markers, aiding in their identification during differentiation.
    • Random Integration: ESCs can be transfected using DNA constructs designed for specific purposes, allowing for the upregulation of transcription factors or the identification of gene expression via reporter genes.
    • Transfection Methods: Conventional methods have proven effective, and lentiviral methods offer another avenue for successful transfection.
    • Electroporation: This technique has been employed to achieve homologous recombination in ESC colony fragments, as demonstrated by Zwaka and Thomson (2005).
  4. Exploring Gene Function with siRNA:
    • Small inhibitory RNAs (siRNA) present a novel approach to investigate gene function in ESCs. By using siRNA, researchers can delve into various cellular processes, including renewal, differentiation, apoptosis, and oncogenesis.

In conclusion, the genetic manipulation of embryonic stem cells is a rapidly evolving field. By employing a combination of advanced techniques, researchers aim to harness the therapeutic potential of ESCs, ensuring their safe and effective use in regenerative medicine.

Differentiation Of Embryonic Stem Cells

Embryonic stem cells (ESCs) possess the unique ability to differentiate into a myriad of cell types, making them a focal point in regenerative medicine and biological research. Their differentiation patterns and the methods to harness this potential are of paramount importance.

  1. Early Differentiation:
    • Within a week post-passage, early morphological differentiation events can be discerned in ESC colonies. The onset of differentiation is evident in the central piled-up areas and the leading-edge borders of the colony. This differentiation encompasses various tissue types, including ectodermal neuroectoderm, mesodermal muscle, and endodermal organ tissues.
  2. Three-dimensional Cultures:
    • When ESCs are cultured in three-dimensional environments, such as “hanging drops” or non-adhesive plastic dishes, they aggregate into structures known as embryoid bodies. Within these bodies, differentiation into primary embryonic germ lineages occurs within five to seven days. These embryoid bodies exhibit a consistent vesicular structure and contain a plethora of cell types, which often display a more random organization compared to their mouse counterparts.
  3. Cell Selection and Enrichment:
    • Specific cell populations can be isolated from embryoid bodies using cell surface markers and separation techniques like fluorescence-activated cell sorting (FACS). Additionally, lineage-specific promoters driving reporter genes can be employed for cell selection. For instance, ESC-derived cardiomyocytes can be enriched using buoyant density gradient separation methods.
  4. Teratoma Formation:
    • When a significant number of ESCs are transplanted into animal tissues, they can form teratomas, which are solid tumors comprising various tissue types. These teratomas, when examined histologically, often contain well-organized embryonic or fetal organs.
  5. Hematopoietic Differentiation:
    • Blood islands, precursors to hematopoietic cells, can form in differentiating ESCs. By exposing embryoid bodies to a mix of hematopoietic cytokines, hematopoietic progenitors can be induced, leading to the formation of both erythroid and myeloid derivatives. These progenitors exhibit markers similar to hematopoietic progenitors of the dorsal aorta.
  6. Endodermal Differentiation:
    • Differentiating cells of the endodermal lineage has been challenging due to the absence of early endoderm progenitor markers. There’s significant interest in generating pancreatic β-islet cells for potential diabetes treatment. While some embryoid body cells stain positive for insulin, they often lack other markers, suggesting they might not be true insulin-producing cells. However, differentiation into hepatocyte-like cells has been achieved using specific treatments, leading to the expression of hepatocyte markers and functionalities.

In summary, the differentiation of embryonic stem cells is a multifaceted process, with each lineage requiring specific conditions and markers for identification. Harnessing this differentiation potential is crucial for therapeutic applications and understanding developmental biology.

Applications of Embryonic Stem Cell

Embryonic stem cells (ESCs) offer a plethora of applications in both scientific research and medical therapeutics due to their inherent ability to differentiate into various cell types. Here are the primary applications of embryonic stem cells:

  1. Tissue Engineering: ESCs are pivotal in tissue engineering. Their ability to perform specific biological functions, such as cytokine secretion, interaction with neighboring cells, and extracellular matrix production, makes them invaluable. They can self-renew and differentiate into specialized cells, making them a prime candidate for tissue engineering endeavors. Advanced techniques aim to modify ESCs to prevent immune responses upon implantation, which would mark a significant advancement in tissue engineering.
  2. Cell Replacement Therapies: ESCs are being explored for their potential to differentiate into various cell types, such as cardiomyocytes, neurons, hepatocytes, bone marrow cells, islet cells, and endothelial cells. This differentiation potential offers promising avenues for cell replacement therapies, addressing conditions like Parkinson’s disease, heart ailments, and more.
  3. Clinical Potential: ESCs have been differentiated into dopamine-producing cells, offering potential treatments for Parkinson’s disease. They have also been differentiated into natural killer cells, bone tissue, and insulin-producing cells, presenting potential therapeutic avenues for diabetes and other conditions.
  4. Drug Discovery: ESCs are instrumental in toxicology and as cellular screens for new drug entities. Cardiomyocytes derived from ESCs serve as in vitro models to test drug responses and predict toxicity profiles. Additionally, ESC-derived hepatocytes can be used in drug metabolism studies during the preclinical stages of drug discovery.
  5. Models of Genetic Disorders: ESCs are being utilized to model genetic disorders. By genetically manipulating these cells or deriving diseased cell lines through prenatal genetic diagnosis, researchers can study disorders like Fragile-X syndrome, Cystic fibrosis, and other genetic conditions.
  6. DNA Damage Repair: ESCs employ robust mechanisms to repair DNA damages accurately. They predominantly use homologous recombinational repair (HRR) for double-strand breaks, ensuring genetic stability. If repair fails, ESCs undergo programmed cell death, preventing mutation and potential progression to cancer.
  7. Clinical Trials: The world’s first human ESC trial began in 2009, focusing on the transplantation of oligodendrocytes derived from human ESCs into spinal cord-injured individuals. This trial aimed to assess the safety and potential efficacy of the treatment. Subsequent trials have continued to explore the therapeutic potential of ESCs in spinal cord injuries.
  8. Commercialization and Funding: Companies like Asterias Biotherapeutics have received funding to re-initiate clinical trials involving ESCs for spinal cord injuries. Their product, AST-OPC1, derived from human ESCs, contains oligodendrocyte progenitor cells, which support nerve cells in the spinal cord and brain. Early phase trials have shown promise, and further funding aims to support later-stage trials and potential commercialization.

In summary, embryonic stem cells, with their unparalleled differentiation potential, are at the forefront of regenerative medicine, drug discovery, and scientific research. Their applications span from tissue engineering to modeling genetic disorders, making them an invaluable asset in the quest to address various medical challenges.


What is the unique capability of embryonic stem cells (ESCs)?
a) They can only differentiate into muscle cells.
b) They can only differentiate into nerve cells.
c) They can differentiate into any cell type of the body.
d) They cannot differentiate into any cell type.

Which stage of the embryo are embryonic stem cells derived from?
a) Morula
b) Gastrula
c) Blastocyst
d) Zygote

Which of the following markers is NOT associated with pluripotency in embryonic stem cells?
a) Oct4
b) Sox2
c) Hemoglobin
d) Nanog

What is the potential risk when transplanting embryonic stem cells into tissues?
a) They might not differentiate.
b) They can form teratomas.
c) They can turn into blood cells only.
d) They can only form nerve cells.

In which culture method do embryonic stem cells form structures called embryoid bodies?
a) Two-dimensional culture
b) Hanging drop culture
c) Direct contact culture
d) Suspension culture

Which of the following is NOT a method used for genetic manipulation of embryonic stem cells?
a) Electroporation
b) Lentiviral methods
c) Homologous recombination
d) Photosynthesis

Which of the following is a challenge in maintaining embryonic stem cells in culture?
a) They differentiate easily.
b) They grow too slowly.
c) They require high oxygen levels.
d) They cannot be frozen.

Which of the following is NOT a method for subculturing embryonic stem cells?
a) Mechanical colony dispersion
b) Enzymatic dissociation
c) Ultraviolet radiation
d) Hand-picking

Which of the following antigens is commonly used to characterize embryonic stem cells?
a) SSEA-3
b) Hemoglobin
c) Insulin
d) Melanin

What is the primary reason for interest in producing pancreatic β-islet cells from embryonic stem cells?
a) To treat skin diseases.
b) To treat diabetes.
c) To treat cardiovascular diseases.
d) To treat respiratory diseases.


What are embryonic stem cells (ESCs)?

Embryonic stem cells are pluripotent stem cells derived from the inner cell mass of a blastocyst, an early-stage embryo.

How are ESCs different from adult stem cells?

Unlike adult stem cells, which are limited to differentiating into different cell types of their tissue of origin, ESCs are pluripotent, meaning they have the potential to differentiate into any cell type in the body.

Why are embryonic stem cells important for research?

ESCs offer a valuable model to study early human development and have the potential for regenerative medicine, including tissue repair and replacement.

Is there any controversy surrounding embryonic stem cell research?

Yes, because the derivation of ESCs typically involves the destruction of an embryo, it raises ethical concerns, especially in cultures and religions that believe life begins at conception.

What are the potential therapeutic uses of ESCs?

ESCs have the potential to treat a range of diseases, including Parkinson’s disease, diabetes, heart disease, and spinal cord injuries, among others.

How are ESCs derived?

ESCs are derived from the inner cell mass of blastocysts, which are embryos that are about 3-5 days old.

Can ESCs form tumors?

Yes, one of the challenges with ESCs is their potential to form tumors called teratomas when transplanted into tissues.

What are embryoid bodies?

Embryoid bodies are three-dimensional aggregates formed when ESCs are cultured in suspension, allowing them to differentiate into various cell types.

Are there alternative methods to obtain pluripotent stem cells without destroying embryos?

Yes, induced pluripotent stem cells (iPSCs) are cells that have been reprogrammed to an embryonic-like state, typically by introducing specific genes. They offer a way to obtain pluripotent cells without using embryos.

What are the challenges in using ESCs for regenerative medicine?

Challenges include controlling ESC differentiation into specific cell types, avoiding immune rejection, and ensuring that the cells do not form tumors upon transplantation.


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  2. Rathjen, J., & Rathjen, P. (2013). Embryonic Stem Cells. Brenner’s Encyclopedia of Genetics, 479–481. doi:10.1016/b978-0-12-374984-0.00490-3
  3. Klimanskaya, I., Kimbrel, E. A., & Lanza, R. (2014). Embryonic Stem Cells. Principles of Tissue Engineering, 565–579. doi:10.1016/b978-0-12-398358-9.00029-x
  4. Klimanskaya, I., Kimbrel, E. A., & Lanza, R. (2020). Embryonic stem cells. Principles of Tissue Engineering, 421–434. doi:10.1016/b978-0-12-818422-6.00024-1
  5. Trounson, A. (2007). Embryonic Stem Cells. Principles of Tissue Engineering, 421–429. doi:10.1016/b978-012370615-7/50034-2
  6. Yu, J., & Thomson, J. A. (2014). Embryonic Stem Cells. Essentials of Stem Cell Biology, 387–398. doi:10.1016/b978-0-12-409503-8.00027-5
  7. Klimanskaya, I. (2019). Embryonic Stem Cells. Principles of Regenerative Medicine, 113–123. doi:10.1016/b978-0-12-809880-6.00007-2
  8. Yu, J., & Thomson, J. A. (2013). Embryonic Stem Cells. Handbook of Stem Cells, 275–286. doi:10.1016/b978-0-12-385942-6.00022-6
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What is a digital colony counter? Why do Laboratory incubators need CO2? What is Karyotyping? What are the scope of Microbiology? What is DNA Library? What is Simple Staining? What is Negative Staining? What is Western Blot? What are Transgenic Plants? Breakthrough Discovery: Crystal Cells in Fruit Flies Key to Oxygen Transport
What is a digital colony counter? Why do Laboratory incubators need CO2? What is Karyotyping? What are the scope of Microbiology? What is DNA Library? What is Simple Staining? What is Negative Staining? What is Western Blot? What are Transgenic Plants? Breakthrough Discovery: Crystal Cells in Fruit Flies Key to Oxygen Transport
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