Stem Cells and Regenerative Medicine Flashcards
What are Stem Cells
- Can differentiate into many different cell types
- Capable of self-renewal via cell division
- Provide new cells as an organism grows and can replace cells that are damaged or lost
- Several different types of stem cells: embryonic, adult and induced pluripotent stem cells
- Targeted by researchers for their therapeutic potential
What conditions can be treated with stem cell therapy
- Blindness
- Wound healing
- Myocardial Infarction
- Spinal cord injury
- cancers
List the three stem cell sources
- Adult stem cells
- Embryonic stem cells
- Induced pluripotent stem cells
What roles do adult stem cells have
- replace damaged cells
- reduced function as can only differentiate into a few cell types
- Multipotent tissue-specific cells
- Can be extracted and manipulated in-vitro
What roles do Embryonic stem cells have
- can become all cell types
- pluripotent
What roles do induced pluripotent stem cells have
- lab made by converting normal cells by exposing them to chemicals
- reduced graft rejection
- used for organ models
What can all stem cells be used for
- Model for basic and translational studies
- Disease modelling
- Drug screening
- Cell replacement therapy
- Cell differentiation - 3D organoid models
- Developmental biology
What are stem cell niches
Tissue-specific stem cells are maintained in special supportive microenvironments called stem cell niches.
List some stem cell niches
- Supporting Extracellular matrix
- neighbouring niche cells
- secreted soluble signalling factors (e.g. growth factors and cytokines)
- physical parameters; shear stress, tissue stiffness, and topography),
- environmental signals (metabolites, hypoxia, inflammation, etc.).
Compare the properties of each stem cells
Embryonic Stem Cells:
- Pluripotent
- High risk of tumour creation
- High risk of rejection
- high cell potency
- low probability of mutation
Adult stem cells:
- Oligopotent, Unipotent
- Less risk of tumour creation
- low risk of rejection
- A limited number of cells may be obtained
- high mutation risk
Induced pluripotent stem cells:
- less growth than embryonic stem cells
- less risk of tumour formation
- low risk of rejection
- A limited number of cells may be obtained
- high mutation risk
How can you generate iPSC
- Adult somatic cells are taken from a donor
- The cells are treated with reprogramming factors
- Then transferred to ESCs media
- They undergo Morphological and expressional transitions
- the cells then mature to iPSCs
What transcription facts are use and what does each do
- c-Myc promotes DNA replication and relaxes chromatin structure
- allows Oct3/4 to access its target genes.
- Sox2 and Klf4 also co-operate with Oct3/4 to activate target genes
- these encode transcription factors which establish the pluripotent transcription factor network
- result in the activation of the epigenetic processes (more open chromatin) that establish the pluripotent epigenome.
- The iPS cells have a similar global gene expression profile to that of ES cells.
How can stem cells be tracked in the body
A fluorescent reporter gene is inserted into the cells
the cells can be tracked where they go to non-invasively
List the 2 CVS regeneration strategies
- Cell transplantation approaches to promote cardiac regeneration and repair
- Therapies based on direct stimulation of endogenous cardiomyocyte production
Explain models which regenerate cardiac tissue
Zebrafish, amphibians and some neonatal mice can regenerate the heart.
- Re-expression of developmental programmes
- Reactivation of epicardium and endocardium
- cardiomyocyte redifferentiation
- fibrin clot formation
- cardiomyocyte proliferation and heart regeneration
Explain the immune response in CVS regeneration
In normal mice, after monocyte-derived macrophage infiltration, there is limited revascularization and scar tissue is formed.
In neonatal mice, there is embryonic macrophage infiltration and growth and regeneration of the heart.
Explain the lymphatic response in CVS regeneration
In endogenous lymphatic response, there is insufficient clearing of tissue fluid leading to inflammation and oedema.
VEGFC-C156S administration causes augmented lymphatic response and clearance of excess tissue fluid
How can you make cardiac lineages from iPSC cells
- Somatic cells to iPSCS by the delivery of Yamanaka factors
- Into pre-cardiac mesoderm with GSK-3B inhibition
- Into cardiovascular progenitor cells with Ant signalling inhibition
- These cells can become all the cells of the heart via other signalling pathways
Describe stem cell transplantation
Induced pluripotent stem cells (iPSCs) are a potential source of autologous patient-specific cardiomyocytes for cardiac repair providing a major benefit over other sources of cells in terms of immune rejection.
Grafted cardiomyocytes (GFP+) survived for 12 weeks with no evidence of immune rejection. Showed:
1.electrical coupling with host cardiomyocytes
2.improved cardiac contractile function at 4 and 12 weeks after transplantation
But incidence of ventricular tachycardia increased compared to controls.
What is the role of Myocardial thymosin
Necessary for epicardial migration, coronary vasculature and cardiomyocyte survival
Importantly Tb4 addition to adult hearts can stimulate epicardial outgrowth and neovascualarisation
What is FSTL1
FSTL1 in the epicardium has potent cardiogenic activity
Epicardial expression is lost after MI
If restored experimentally, it promotes regeneration of pre-existing cardiomyocytes in mouse and pig models
List some Stem cell-based therapy for cancer
- Chemo/radiotherapy kills cancerous cells. Transplantation of stem cells reconstitutes healthy cells
- Clinical trials for other tumour types; brain and breast cancer, neuroblastoma, sarcoma
- Effector immune cells from iPSC/ESCs e.g. engineered T and NK cells targeted for immunotherapy.
- production of anti-cancer vaccines
- MSCs/NSCs deliver genes, nanoparticles, and oncolytic viruses to tumour niche due to intrinsic tumour tropism.
- exosomes extracted from the culture of drug-priming MSCs/NSCs can target the drugs to tumour sites.
- Mutation correction in vitro, drug testing in vitro before replacement in vivo.
List some Stem cell-based therapy for burns
Replace lost skin cell types, speeding up endogenous healing. Generate ECM and produce paracrine signals which aid healing.
- Fetal fibroblasts (from ESCs); improve skin repair due to the high expansion ability, low immunogenicity, and intense secretion of bioactive substances such asFGFs, VEGFs, KGFs
- Epidermal stem cells; high proliferation rate and easy access and keep their potency and differentiation potential for long periods. Generate most skin cell types for repair and regeneration
- Mesenchymal stem cells; They have a high differentiation potential and a certain degree of plasticity. Migrate to the injured tissues, differentiate, and regulate the tissue regeneration by the production of growth factors, cytokines, and chemokines
- iPSCs; can be differentiated into dermal fibroblasts, keratinocytes, and melanocytes.
List some Stem cell-based therapy for Eye injuries (cornea)
- Stem cells at the edge of the cornea, limbal stem cells are responsible for making new corneal cells to replace damaged ones.
- If these stem cells are lost due to injury or disease, the cornea can no longer be repaired. This affects the ability of light to enter the eye, resulting in a significant loss of vision.
- Limbal stem cells are collected from an adequately healthy donor eye, and are expanded in the laboratory to sufficient numbers and transplanted into the damaged eye.
- Repairs the cornea and permanently restores vision.
- To avoid immune rejection this treatment only works if the patient has a healthy section of limbus from which to collect the limbal stem cells.
- iPSC cells can be induced to make corneal epithelial cells for transplant and exposure to the right signals can transfor fibroblast cells into limbal stem cells
List some Stem cell-based therapy for Eye injuries (retina)
- Retinal pigment epithelium (RPE) is a single layer of post-mitotic cells, acting as a selective barrier to and a vegetative regulator of the overlying photoreceptor layer,
- RPE has a key role in retina maintenance and parts of the retina can die without a functional RPE leading to loss of vision
- RPE cells can be damaged in a variety of diseases such as: age-related macular degeneration (AMD), retinitis pigmentosa and Leber’s congenital aneurosis.
- RPE cells have been made from both ESC and iPSC
List some Stem cell-based therapy for Spinal injury
- Biopsy of somatic cells from donor
- Reprogram to iPSC
- Differentiate into neural stem cells
- Implant cells into the injury location
- cells differentiate into many types to tapir the injury
