L5: Stem Cells & Regenerative Medicine Flashcards by BLACK H

What are the types of stem cells?

→embryonic
→induced
→pluripotent

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What is the origin of embryonic stem cells?

→pre-implantation embryo

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Give examples of stem cells uses

→ Model for basic and translational studies
→Cell replacement therapy
→Cell differentiation
→3D organoid models
→Drug screening

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What can endodermal line differentiate into?

→lung

→pancreas

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What can mesodermal line differentiate into?

→heart muscle

→RBCs

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What can ectodermal line differentiate into?

→skin

→neuron

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How are tissue specific stem cells maintained?

→special supportive microenvironments called stem cell niches.

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What are the features of stem cell niches?

→Supporting ECM
→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.).

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What are the advantages of ESCs

→pluripotent- differentiate into any type of cell
→unlimited growth potential, high cell potency
→very low probability of mutation-induced damage in DNA

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What are the disadvantages of ESCs?

→higher risk of tumour creation- spontaneous disease

→risk of being genetically different from the recipient’s cells- rejection

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What are the advantages of adult stem cells?

→compatible with recipient’s cells- low risk of rejection

→less risk of tumour creation

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What are the disadvantages of adult stem cells?

→oligopotent, limited cell potency
→limited numbers may be obtained
→higher probability of mutation induced damage of DNA

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What are the advantages of induced pluripotent stem cells?

→low risk of rejection

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What are the disadvantages of iPSCs?

→low growth potential
→low risk of tumour formation
→rather limited numbers may be induced
→higher probability of mutation induced damage of DNA

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What do iPSCs and ESCs have in common?

→cells have a similar global gene expression profile to that of ES cells

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Describe how iPSCs are generated?

→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.

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What are the pluripotent factors involved in iPSCs generation?

→c-Myc
→Oct3/4
→Sox2
→Klf4

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What factor does Klf4 and Sox2co-operate with?

→Oct3/4

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What type of chromatin is present in pluripotent iPSCs?

→most of the chromatin exists as euchromatin

→bearing histone marks associated with transcriptional activity

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What is adult cardiomyocyte turnover like?

→low

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What are the two types of regenerative strategies?

→Cell transplantation

→direct stimulation of endogenous cardiomyocyte production

What is cell transplantation aimed at?

→replenishing lost cardiomyocytes.

What are the challenges of cell based regenerative therapies?

→Immune rejection, manufacture

→isolation of sufficient cells, mode of delivery

→clinical regulation all challenges.

What does cell free regenerative therapy involve?

→re-activation of developmental pathways e.g. epicardium based on models where the is no/reduced scarring and full cardiac regeneration

What is neovascularisation?

→Improved circulation to injured area →Paracrine effects improving CM replacement

What is reactivation of epicardium important for?

→coronary blood vessels

Compare immune response of CV disease in adults and neonatal

→adults= monocytes derived macrophage, no CM proliferation, and limited vascularisation →fibrotic scar, contractile dysfunction →neonatal= infiltration of injury by embryonic macrophages, and cardiomyocytes proliferation, and CM revascularisation →functional recovery

How are cardiac lineages from iPSCs made?

→Somatic cells are reprogrammed by Ymanak factors eg OCT4 and Sox2 to make iPSCs →iPSCs exposed to GSK3b inhibition to make pre-cardiac mesoderm →Wnt signalling inhibition to make CV progenitor cells →exposed to TGF-b, PDGF, VEGF to make specialised cardiac cells

What is necessary for epicardial migration and coronary vasculature in developmental gene activation?

→Myocardial thymosin β4

What does addition of Tb4 to adult hearts do?

→stimulate epicardial outgrowth and neovascualarisation

What is involved in transplantation and paracrine signals in CV regeneration?

→grafting sheet cells onto a heart →cells do not seem to integrate into the heart tissue. Instead, they may release paracrine factors that help to regenerate the damaged muscle.

What is lost in a MI?

→Epicardial expression | →FSTL1 in the epicardium has potent cardiogenic activity

What is involved in stem cell therapy for cancer?

→Effector immune cells from iPSC/ESCs e.g. engineered T and NK cells targeted for immunotherapy. →MSCs/NSCs deliver genes, nanoparticles, and oncolytic viruses to tumour niche →Mutation correction in vitro, drug testing in vitro before replacement in vivo.

How are burns treated?

→Generate ECM and produce paracrine signals which aid healing

What are the different types of stem cells involved in burn therapy?

→fetal fibroblasts from ESCs →epidermal stem cells →mesenchymal →iPSCs

How are fetal fibroblasts used in burn therapy?

→improve skin repair due to the high expansion ability, →low immunogenicity, →intense secretion of bioactive substances such asFGFs, VEGFs, KGFs

What do fetal fibroblasts secrete?

→FGFs, VEGFs, KGFs

Why are epidermal stems cells used in burn therapy?

→high proliferation rate →easy access →keep their potency and differentiation potential for long periods. →Generate most skin cell types for repair and regeneration

Why are MSC used in burn therapy?

→They have a high differentiation potential →a certain degree of plasticity. →Migrate to the injured tissues, differentiate, →regulate the tissue regeneration by the production of growth factors, cytokines, and chemokines

Why are iPSCs used in burn therapy?

→can be differentiated into dermal fibroblasts, keratinocytes, and melanocytes

What are limbal stem cells?

→Stem cells at the edge of the cornea

What happens if limbal cells ate lost?

→cornea can no longer be repaired

How are limbal cells used to treat eye injury or disease?

→Limbal stem cells are collected from an adequately healthy donor eye →are expanded in the laboratory to sufficient number →transplanted into the damaged eye →Repairs the cornea and permanently restores vision.

How is rejection avoided in eye injury therapy?

→works if the patient has a healthy section of limbus from which to collect the limbal stem cells.

How is iPSCs used to treat eye injury?

be induced to make corneal epithelial cells for transplant | →exposure to the right signals can transform fibroblast cells into limbal stem cells

What is RPE?

→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

What can happen to the eye without RPE?

→parts of the retina can die

How can the RPE be damaged?

→age-related macular degeneration (AMD), →retinitis pigmentosa →Leber’s congenital aneurosis.

How can RPEs be made?

→ESC and iPSC

How are iPSCs used to treat spinal injury?

→somatic cells biopsies from patients →transform into iPSCs →differentiate into different neural cells

What results do NSPCs therapy in spinal injury show?

→can form functional synaptic subnetworks whose activity patterns resemble intact spinal cord →grafts can integrate into sites of spinal cord injury (SCI) and generate neuronal relays across lesions