cells

Views:
 
     
 

Presentation Description

No description available.

Comments

Presentation Transcript

PowerPoint Presentation:

Tissue Engineering Cells (adhesion & extracellular matrix)

PowerPoint Presentation:

Cell-cell Cell-Extracellular Matrix (ECM) Cell-Substrate Adhesion:

PowerPoint Presentation:

Adhesion sites between Cell-cell & cell-ECM: Gap junction (Communicating junctions ) Desmosome (macula adheres) Hemidesmosome Tight junction (occluding j. )

PowerPoint Presentation:

Communicating junctions (Gap junctions) : The channels connect the lipid bilayers of two cells. Connection between the plasma membranes of adjacent cells. Allow for small molecules to pass from cell to cell (less than 1000 daltons). has an intercellular gap of approximately 2-4nm electrically excitable cells

PowerPoint Presentation:

Desmosome 30-50 nm Mechanically attached cells (and their cytoskeletons) to the cells or the ECM. They are formed by a homotypic association of transmembrane glycoproteins called cadherin. The cytosolic ends of cadherins are associated with cytoskeletal actin microfilaments and intermediated filaments.

PowerPoint Presentation:

Hemidesmosomes: Similar to desmosome They are “spot welding” that connect cells to ECM. In the case of epithelial tissues, the connections are to a dense ECM meshwork called the basal lamina or basement membrane. t.j. tight junction (occludens), a.b. adhesion belt (adherens), d.s. desmosome (spot), g.j. gap junction (communicating), h.d. hemidesmosome

PowerPoint Presentation:

Tight junctions (occluding j. ): < 5 nm gap Forms between to adjacent cells. Acts as a barrier to diffusion, even small molecules (but not water). The junctions are the basis of the high electrical resistance of many epithelia. These junctions (as well as the desmosomes) as also dynamic structures (intermittently dissociate and reform.

PowerPoint Presentation:

Cell-solid substrata adhesion: Focal adhesion: Close contact Extracellular matrix contact Preadsorbed proteins Proteins produced by the cell Substratum properties Strength and type of adhesion

PowerPoint Presentation:

Secondary minimum Primary minimum Energy barrier DLVO theory

PowerPoint Presentation:

Extracellular Matrix (ECM) ECM is composed of: Fibers (collagen and elastin) A large amorphous interfibrillary matrix (mainly proteoglycans, noncollagenous cell-binding adhesive glycoproteins, solutes, and water)

PowerPoint Presentation:

The principal functions of ECM: Mechanical support for cell anchorage Determination of cell orientation Control of cell growth Maintenance of cell differentiation Scaffolding for orderly tissue renewal Establishment of tissue microenvironment Sequestration, storage, and presentation of soluble regulatory molecules

PowerPoint Presentation:

Note : Polysaccharides are polymers of simple sugars. They exist in tissues as a highly viscose material that interact readily with proteins, including collagen, resulting in glycosaminoglycans (GAGs) [also known as mucopolysaccharides (MPS) ] or proteoglycans .

Cell Spreading and Locomotion:

Cell Spreading and Locomotion

Thermodynamic of Adhesion and Spreading:

Thermodynamic of Adhesion and Spreading

Signaling:

Signaling Cell communication is critical in multicellular organisms. 1. Extracellular signaling 2. Intercellular signaling Cell communicate over short or long distance. The gap junctions connect two adjacent cells.

Extracellular signaling via soluble mediators: :

Extracellular signaling via soluble mediators: 1- Paracrine: immediate vicinity, minimal diffusion 2- Synaptic: activation of neural tissue 3- Endocrine: hormones,… Kinds of signaling: 1- Chemical 2- Mechanical 3- Electrical 4- Structural

Cell specialization and differentiation:

Cell specialization and differentiation Basic functions cells: Nutrient absorption and assimilation Respiration Synthesis of micromolecules Growth Reproduction

PowerPoint Presentation:

Specialized cells have additional capabilities and functions ( such as absorption and secretion of molecules, …) The cells differentiate in order to exhibit specialization. The structural and functional changes that occur during cellular differentiation are usually irreversible. Increasing specialization results in a loss of potentiality and a loss in the capability for cell division. Cellular differentiations involves an alteration in gene expression.

Cell death:

Cell death Necrosis: The localized death of living cells( as from infection or the interruption of blood supply) Apoptosis: A type of cell death in which the cell uses specialized cellular machinery to kill itself.( a cell suicide mechanism)

Stem Cell:

Stem Cell Cells that have the ability to self-replicate and give rise to specialized cells . Stem cells can be found at different stages of fetal development and are present in a wide range of adult tissues.

PowerPoint Presentation:

Self-renewal - the ability to go through numerous cycle of cell division while maintaining the undifferentiated state. Stem cell division and differentiation. A - stem cells; B - progenitor cell; C - differentiated cell; 1 - symmetric stem cell division; 2 - asymmetric stem cell division; 3 - progenitor division; 4 - terminal differentiation

PowerPoint Presentation:

There are three basic types of stem cells . Totipotent stem cells, meaning their potential is total, have the capacity to give rise to every cell type of the body and to form an entire organism. (over 200 different cell type) Pluripotent stem cells, such as embryonic stem cells, are capable of generating virtually all cell types of the body but are unable to form a functioning organism. Multipotent stem cells can give rise only to a limited number of cell types.

PowerPoint Presentation:

For example, adult stem cells, also called organ- or tissue-specific stem cells, are multipotent stem cells found in specialized organs and tissues after birth. Their primary function is to replenish cells lost from normal turnover or disease in the specific organs and tissues in which they are found.

PowerPoint Presentation:

Totipotent stem cells occur at the earliest stage of embryonic development. The union of sperm and egg creates a single totipotent cell. The first differentiation of totipotent cells forms a hollow sphere of cells called the blastocyst. The blastocyst has an outer layer of cells and an inner cell mass inside the sphere. Three primary germ layers of the inner cell mass : ectoderm, mesoderm, and endoderm.

PowerPoint Presentation:

Embryonic stem cells are derived from the inner cell mass of the blastocyst. (very early 4-5 days embryo) Embryonic stem cells cannot form a complete organism because they are unable to generate the entire spectrum of cells and structures required for fetal development. Thus, embryonic stem cells are pluripotent, not totipotent, stem cells.

PowerPoint Presentation:

Adult stem cell derived from adult tissue, undifferentiated progenitor (precursor) cells which mature (differentiate) into functional cell types characteristic of original tissue. (they also may differentiate into some closely related specialized tissues)

PowerPoint Presentation:

Plasticity Under special conditions tissue-specific adult stem cells can generate a whole spectrum of cell types of other tissues, even crossing germ layers. This phenomenon is referred to as stem cell transdifferentiation or plasticity . It can be induced by modifying the growth medium when stem cells are cultured in vitro or transplanting them to an organ of the body different from the one they were originally isolated from.

Some kinds of adult stem cell:

Some kinds of adult stem cell Adipose derived adult stem cells Adipose-derived stem cells (ASCs) have also been isolated from human fat, usually by method of liposuction. Mammary stem cells Mammary stem cells provide the source of cells for growth of the mammary gland during puberty and gestation and play an important role in carcinogenesis of the breast .

PowerPoint Presentation:

Mesenchymal stem cells Mesenchymal stem cells have been classically obtained from the bone marrow . MSCs are multipotent stem cell that can differentiate into a variety of cell types. ( osteoblasts, chondracytes, myocytes, adipocytes, neuronal cells, and into beta-pancreatic islets cells ) Olfactory adult stem cells Olfactory adult stem cells have been successfully harvested from the human olfactory mucosa cells, the lining of the nose involved in the sense of smell. These adult olfactory stem cells appear to have the same ability as embryonic stem cells in giving rise to many different cell types but have the advantage that they can be obtained from all individuals, even older people who might be most in need of stem cell therapies .

Haematopoietic stem cells HSC are stem cells found in the bone marrow. :

Haematopoietic stem cells HSC are stem cells found in the bone marrow.

PowerPoint Presentation:

Neural stem cells The existence of stem cells in the adult brain has been postulated following the discovery that the process of neurogenesis, songbirth of new neurons, continues into adulthood in rats. It has since been shown that new neurons are generated in adult mice, songbirds and primates, including humans.

Some open questions in adult stem cell research :

Some open questions in adult stem cell research Are stem cells found in different tissues fundamentally distinct, or is there a universal adult stem cell? Which adult tissues harbor stem cells? What is the origin of adult stem cells? What regulates stemness , the range of cell types that a cell's progeny can generate?

authorStream Live Help