Stem Cells

Stem cells are relatively ‘unspecialized’ cells that have the unique potential to develop into ‘specialized’ cell types in the body (for example, blood cells, muscle

cells or nerve cells). They occur at all stages of human development, from embryo to adult, and in many

tissues of the body.

What are Stem Cells

General Properties of Stem cell

Stem cells differ from other kinds of cells in the body. All stem cells (regardless of their source) have three general properties:

• They are capable of dividing and renewing themselves for long periods;

• They are unspecialized; • They can give rise to specialized cell types.

Characteristics of Stem cells

• In some organs, such as the gut and bone marrow, stem cells regularly divide to repair and replace worn out or damaged tissues.

• In other organs, however, such as the pancreas and the heart, stem cells only divide under special conditions.

Where Are Stem Cells Found?

Stem cells come from several sources in the body. The names of the cells below indicate the sources from which they are derived.

Embryonic Stem Cells:These stem cells come from embryos in the early stages of development. They have the ability to differentiate into any type of cell in the initial stages of development and become slightly more specialized as they mature.

Fetal Stem Cells:

• These stem cells come from a fetus. At about nine weeks, a maturing embryo enters into the fetal stage of development.

• Fetal stem cells are found in fetal tissues, blood and bone marrow. They have the potential to develop into almost any type of cell.

Umbilical Cord Blood Stem Cells

• These stem cells are derived from umbilical cord blood.• Umbilical cord stem cells are similar to those found in mature or adult stem cells. • They are specialized cells that develop into specific types of

cells.

Placental Stem Cells

These stem cells are contained within the placenta. Like cord blood stem cells, these cells are specialized cells that develop into specific types of cells. Placentas however, contain several times more stem cells than do umbilical cords.

Adult Stem Cells

• These stem cells are present in mature body tissues in infants, children and adults.

• They may also be found in fetal and umbilical cord blood cells.

• Adult stem cells are specific to a particular tissue or organ and produce the cells within that particular tissue or organ.

• These stem cells help to maintain and repair organs and tissues throughout a person's life.

Hematopoietic stem cells: • Hematopoietic stem cells (HSCs) are cells present in blood

and bone marrow. They are capable of forming mature blood cells, such as red blood cells (the cells that carry oxygen), platelets (the cells that help stop bleeding) and white blood cells (the cells that fight infections).

• They give rise to the myeloid (monocytes and macrophages, neutrophils, basophils, eosinophils, erythrocytes,megakaryocytes/platelets, dendritic cells), and lymphoid lineages (T-cells, B-cells, NK-cells).

Hematopoietic Stem Cell

Types of Stem Cell

• Totipotent Stem Cells

These stem cells have the ability to differentiate into any type of cell in the body. Totipotent stem cells develop during sexual reproduction when male and female gametes fuse during fertilization to form a zygote. The zygote is totipotent because its cells can become any type of cell and they have limitless replicative abilities. As the zygote continues to divide and mature, its cells develop into more specialized cells called pluripotent stem cells.

• Pluripotent Stem Cells

These stem cells have the ability to differentiate into several different types of cells. Specialization in pluripotent stem cells is minimal and therefore they can develop into almost any type of cell. Embryonic stem cells and fetal stem cells are two types of pluripotent cells.

• Multipotent Stem Cells

These stem cells have the ability to differentiate into a limited number of specialized cell types.

Multipotent stem cells typically develop into any cell of a particular group or type. For example, bone marrow stem cells can produce any type of blood cell. However, bone marrow cells don't produce heart cells.

Adult stem cells and umbilical cord stem cells are examples of multipotent cells. 

• Mesenchymal stem cells are multipotent cells of bone marrow that have the ability to differentiate into several types of specialized cells related to, but not including blood cells. These stem cells give rise to cells that form specialized connective tissues, as well as cells that support the formation of blood.

Oligopotent Stem Cells

These stem cells have the ability to differentiate into just a few types of cells.

A lymphoid stem cell is an example of a oligopotent stem cell. This type of stem cell can not develop into any type of blood cell as bone marrow stem cells can.

They only give rise to blood cells of the lymphatic system, such as T cells.

• Unipotent Stem Cells– These stem cells have unlimited reproductive capabilities,

but can only differentiate into a single type of cell or tissue.– Unipotent stem cells are derived from multipotent stem

cells and formed in adult tissue. – Skin cells are one of the most prolific examples of

unipotent stem cells. These cells must readily undergo cell division to replace damaged cells.

Stem cell and Diseases

Stem-cell therapy is an intervention strategy that introduces new adult stem cells into damaged tissue in order to treat disease or injury.Stem cell research treats wider variety of diseases:

– Cancer, – Type 1 diabetes mellitus– Parkinson's disease, – Spinal cord injuries, – Huntington's disease, – Multiple sclerosis,  – Muscle damage,– Neurological disorders.

How stem cell treat various Diseases

• Tissue Repair Regenerate spinal cord, Heart tissue or any other major tissues in the body.

• Heart Disease Adult bone marrow stem cells injected into the heart arteries are believe to

improve cardiac functions in victims of heart failure or heart attack.

• Haematopoitic stem cell treatment HPCs are used in the treatment of many malignant (e.g., leukemia,

lymphoma) and non-malignant (e.g., sickle cell disease) diseases to replace or rebuild a patient's hematopoietic system. This type of treatment is called a bone marrow or stem cell transplant.

Overview of Stem cells to treat various disorders

PhospholipidsLesson of Soap Bubble

•Flexibility•Fluidity•Self Sealing•Amphipathic

Structure and Composition

Natural Sources

Phospholipids Classes •Glycerophospholipids

•Sphingolipids

•Ether phospholipids

•PhonophospholipidsDistribution limited to loweranimal/ less important to human health.

Glycero phospholipids

Applications

Industrial ApplicationsLecithin plays a growing role in the chemo-technical industry because of the growing environmental awareness of the people and the increasing need for biodegradable substances.

1. Leather and Textiles• Soothing and softening of textile • Leather tanning as natural dispersant• Textile dying

2 Paint and Inks• By improving dispensability characteristics of the pigments

more even distribution of the pigments resulted.• Good release pr parting agent .Improves adhesion of the

coat by ensuring good wetting of the base and prevents surface flaws due to optimum pigment packing

3.Industrial Microbiology•Soil polluted with petroleum can be remedied by lecithin, used as an emulsifier, dispersing and increasing the digestabilty of the petroleum by microorganism

4.Plant Protection•Plant protection products contain active biocides ingredients, emulsifier, organic solvents and oil.

•Phospho lipid increases the efficiency of biocides lowering dosage of toxic active ingredients, reducing the burden on the environment.

Health applications•Neutraceuticals.•PC protect liver cells

•Homeostasis, fundamental life processes, survival•PC in the bile fluid, help emulsify food ingredients for absorption•PS alleviate stress, support memory, learning, word recall, other cognitive brain functions

Confectionery

• Reduce the viscosity, yield point in choclates and Icecreams. • Make chewing gum better machineable and prevent

from drying.• Prevents recrystallization of sugar & achieve

homogeneous distribution of the fat by emulsification in caramels

BAKERY

roves

Improves the extensibility of the gluten; better homogenization of the different ingredients; better emulsification of the fat; improved water binding.In deep frozen doughs, lecithin improves the freezing and thawing stability.

CONVENIENCE FOOD

•Improve wetting properties•Enhance dust control•Help disperse hydrophilic and lipohilic components•Permit instantizing + agglomeration in one step•Permit complete dispersion in water

COSMETIC INDUSTRY

• Excellent film-forming properties• Hydrating, restructuring, soothing and refatting•Improves the tolerance of the formulation•Reduces irritation caused by other surfactants•Long lasting effects on skin moisturization•Important source of essential linoleic acid•Non-irritant, non-comedogenic and non-allergenic

Pharma Industry

• Natural substance, toxicologically safe • Form stable liposomes • Improve liver metabolism • Cholesterol control

          

ANIMAL FEED

•Reduces abrasion and improves pellet structure•Emulsifier for fat antioxidant•Improve digestibility of nutrients•Source of choline and inositol•Stimulates growth (fish farming)

•Ensures smooth and glossy coat or fur (pets, rabbits)•Improves performance and condition (horses)•Protect against infection (ornamental birds and fishes

Endo membrane System Different membranes that are suspended in the cytoplasm within a eukaryotic cell.

PropertiesTransport system for moving molecules through interior of the cell. Lipid bi-layer Composition with proteins attached to either side or transversing them. Divides cell into organelles.

Cell MembraneSEPARATES LIVING CELL FROM NONLIVING SURROUNDINGSo thin barrier = 8nm thick CONTROLS TRAFFIC IN & OUT OF THE CELLo selectively permeableo allows some substances to cross more easily than others hydrophobic

vs hydrophilic MADE OF PHOSPHOLIPIDS, PROTEINS & OTHER MACROMOLECULES

Phospholipids Fatty acid tails

o hydrophobic Phosphate group head

o hydrophilic Arranged as a bi layer

Phosphate

Fatty acid

Phospholipid bilayer

Polarhydrophilicheads

Nonpolarhydrophobictails

Polarhydrophilicheads

Glycoprotein

Phospholipids

Extracellular fluid

Glycolipid

Cholesterol Trans membraneproteins

Filaments ofcytoskeletonCytoplasm

Peripheralprotein

Membrane is a collage of proteins & other molecules embedded in the fluid

matrix of the lipid bilayer

Membrane fat composition Fat composition affects flexibility

o membrane must be fluid & flexibleo % unsaturated fatty acids in phospholipids keep

membrane less viscousocold-adapted organisms, like winter wheat increase %

in autumno Cholesterol in membrane

Membrane Proteins Proteins determine membrane’s specific functions

Peripheral proteins oloosely bound to surface of membraneocell surface identity marker (antigens)

Integral proteins openetrate lipid bi layer, usually across whole

membrane oTrans membrane proteinoTransport proteinsoChannels, Permeases (pumps)

ExamplesNH2

H+

COOH

Cytoplasm

Retinalchromophore

Nonpolar(hydrophobic)a-helices in thecell membrane H+

Porin monomerb-pleated sheets

Bacterialoutermembrane

Proton pump channel in photosynthetic acteria

Water Channels in Bacteria

Function through conformational change

Functions of Membrane Proteins

Outside

Plasma membrane

InsideTransporter Enzyme Activity Cell surface

Receptor

Cell surface Identity marker Cell Adhesion Attachment to

Cytoskeleton

Membrane carbohydrates Play a key role in cell-cell recognition

o important in organ & tissue developmentobasis for rejection of foreign cells by

immune system

Movement across the Cell Membrane

Passive Transport Simple diffusion

diffusion of non polar, hydrophobic molecules lipids high low concentration gradient

Facilitated transport diffusion of polar, hydrophilic molecules through a protein channel

high low concentration gradient Active transport

diffusion against concentration gradient low high

uses a protein pump requires ATP

Getting through cell membrane

ATP

ATP

Getting through cell membrane