Stem cells Flashcards
Tissue eng
Tissue engineering is an interdisciplinary field that applies the principles of engineering and the life sciences toward the development of biological substitutes that restore, maintain, or improve tissue function.
Three general strategies for the creation of new tissue
Three general strategies have been adopted for the creation of new tissue
1) Isolated cells or cell substitutes.
2) Tissue-inducing substances.
3) Cells placed on or within matrices.
ECM
- The biochemical and biophysical properties of the extracellular matrix (ECM) dictate tissue-specific cell behaviour
- The molecules that are associated with the ECM of each tissue, including collagens, proteoglycans, laminins and fibronectin, and the manner in which they are assembled determine the structure and the organization of the resultant ECM.
- The product is a specific ECM signature that is comprised of unique compositional and topographical features that both reflect and facilitate the functional requirements of the tissue
ECM collagen
- Small, modular subunits form homopolymers and heteropolymers that become supramolecular assemblies with highly specialized organization
- Collagens are the major proteins of the ECM. The structural hallmark of all collagens is the triple helix, which is a right-handed helix of three polypeptide α- chains (homotrimers and heterotrimers), each of which contains one or more regions that are characterized by the repeating amino acid motif Gly-X-Y, where X and Y can be any amino acid
pluripotent stem cells
Can make all types of specialized cells in the body
Embryonic stem cells are pluripotent
Multipotent
Can make multiple types of specialized cells, but not all types Tissue stem cells are multipotent
Organogenesis
The series of organized integrated processes that transform an amorphous mass of cells into a complete organ in the developing embryo.
small, heterogeneous, variable complexity in cellular composition
lack stromal, vascular and immunological components
4 elements influencing organoid culture
Cell source
soluble factors
matrix
physical cues/ integrating cues
What do you do to cells after collection to make organoids
Enzymatic tissue dissociation -> dissolve ECM
Mechanical tissue dissociation
4 R’s of Term
Repair
Regenerate
Replacement
Restoration of impaired function
What was the first organ transplant
mass gen kidney transplant1954
Isolated Cells or Cell Substitutes, def, pros, cons
Transplantation of specific cells to replace malfunctioning or absent cells in a patient, avoiding surgical complications and focusing on replacing only the needed cells.
Benefits: Less invasive, avoids surgery, allows pre-manipulation of cells, targets therapy specifically.
Limitations: Potential failure to maintain function in the recipient, risk of immunological rejection.
Tissue-Inducing Substances, def, needs, ex.
Biologically active molecules like growth factors used to stimulate the body’s own tissue repair mechanisms. Tissue-inducing substances can influence chemically, mech and bio the growth and development of a stem cell
Key Needs: Purification and large-scale production of signal molecules; development of precise delivery methods to target sites.
Example: Bone Morphogenetic Proteins BMPs for bone healing
Cells Placed on or Within Matrices
Embedding cells in natural or synthetic matrices to support tissue formation or repair, used in both closed (immunoprotected) and open (integrated) systems.
Closed Systems: Semi-permeable membranes isolate cells from the immune system, used for implants or extracorporeal devices.
Open Systems: Cells in matrices are implanted to integrate with bodily tissues, using materials like collagen or synthetic polymers.
Immunological Strategies: Use of immunosuppressive drugs or autologous cells to prevent rejection.
Ross G. Harrison (1910) innovations
Achieved the first successful ex vivo cell culture, proving nerve fibers originate from nerve cells, not secreted by other tissues. Utilized a solution containing clotted frog lymph for structural support, overcoming challenges with previous methods.
Introduced the hanging drop technique, adapting from microbiology to embryology, facilitating unrestricted cell growth.
Overcame bacterial infection in cultures by establishing sterile working conditions.
Alexis Carrel (1873–1944) tissue culture
Nobel Laureate who pioneered cell culture techniques, growing endothermal animal cells ex vivo using clotted plasma as a scaffold, foundational for modern tissue culture.
Tissue Culture Established (1912): Carrel developed methodologies for mass cell culture, leading to the establishment of tissue culture as a key experimental tool in biology and medical sciences.
Carrel’s Laboratory Practices: Technicians in Carrel’s lab at the Rockefeller Institute wore distinctive full-length black, hooded gowns, reflecting the unique work culture and the era’s scientific practices.
Alan Turing and Morphogenesis
Introduced the first computational model for biological phenomena, demonstrating how reaction-diffusion systems could explain pattern formation in biological development through mathematical models.
ECM Influence on Cell Behavior
The biochemical and biophysical properties of the extracellular matrix (ECM) are crucial in dictating tissue-specific cell behavior, guiding how cells grow, differentiate, and interact.
Composition and Assembly ECM
ECM is composed of collagens, proteoglycans, laminins, and fibronectin. The specific assembly and organization of these molecules create a unique ECM signature for each tissue, reflecting its structural and functional needs.
- The extracellular matrix (ECM) is a dynamic structure that is constantly remodelled to control tissue homeostasis
- The ECM in mammals is composed of around 300 proteins, known as the core matrisome
Tissue-Specific ECM Roles
Each tissue features a specialized ECM that provides structural support, transmits forces, and filters macromolecules
Different classes of ECM molecules are designed to interact with each other, producing unique physical and signaling properties essential for tissue health and activity.
Structural Composition and triple helix of collagen
Structural Composition: Collagen, the primary protein in the ECM, forms through the assembly of small, modular subunits into homopolymers and heteropolymers, creating supramolecular assemblies with a highly specialized organization.
Triple Helix Hallmark: The defining structural feature of collagen is its triple helix configuration, comprising three polypeptide α-chains (either homotrimers or heterotrimers) that wind into a right-handed helix. This structure is characterized by the repeating amino acid motif Gly-X-Y, where X and Y can be any amino acid(proline and hydroxyproline), allowing for varied composition and properties among collagen types.
Complex Assembly Process collagen
The transformation from the initial translational product of collagen into a mature fibrillar structure involves intricate intracellular and extracellular post-translational modifications. These steps ensure the collagen fibrils are properly formed and capable of withstanding tensile forces.
collagen peptides are synthesized in the endoplasmic reticulum as procollagen, which includes additional peptide sequences at both ends. These procollagen molecules are then transported to the Golgi apparatus, where they are processed and packaged before being secreted outside the cell. Once outside, the extra peptide sequences are cleaved off, allowing the collagen molecules to assemble into triple helices and form fibrils. These fibrils then aggregate to form mature collagen fibers, providing structural support and tensile strength to tissues.
Mechanical Properties Collagen source
The unique mechanical strengths of fibrillar collagen, essential for tissue integrity and function, are directly attributable to its triple helical structure. This relationship between the collagen’s three-dimensional protein structure and its role in the ECM highlights the critical interplay between molecular configuration and ECM functionality.
Types and Locations ECM proteoglycans
Heparan Sulfate Proteoglycans (HSPGs): Found in the basement membrane, crucial for cellular signaling and filtration.
Chondroitin Sulfate Proteoglycans (CSPGs): Located in cartilage and neural ECMs, they play key roles in structural integrity and cell signaling.
