stem cells

endoderm

gives rise to epithelial lining of the gut and associated organs such as lungs, esophagus, intestine, etc

mesoderm

connective tissue such as cartilage, bone, muscles, vascular system, etc

ectoderm

epidermis, nervous system

fertilized egg cleaves into a _____

blastula

throughout development, cells become _____

less potent

totipotent

potential to give rise to all cell types

examples of totipotent cells

zygote, early blastula

pluripotent

potential to give rise to almost all cell types

examples of pluripotent cell

late blastula

multipotent

potential to give rise to multiple cell types

example of multipotent

mesoderm, ectoderm, endoderm

differentiation

process where cell becomes specialized to perform a specific function

how do cells change what they change into

by changing transcription factors that change what genes are expressed

morphogen

one way to differentiate

morphogens are signal molecules that tell cells how to differentiate depending on concentration of signal recieved

lateral inhibition

cell interactions that force neighboring cells to be different

asymmetric cell division

cell divides transcription factors unevenly which results in daughter cells with different levels of transcription factors

stem cells

specialized cells that provide fresh supply of differentiated cells

defined by: not terminally differentiated, can divide without limit, have choice to differentiate or remain stem cell

absorptive cell

intestinal cell that takes up nutrients

general gut epithelial cell

goblet cell

secretes mucus into inside of gut to protect cells

paneth cells

help protect stem cells

provide innate immunity because we eat bacteria

enteroendocrine cell

regulatory cell, secretes hormones into body as response from gut

crypt

top: nondividing, differentiated cells

middle: rapidly dividing cells

bottom: stem cells and nondividing differentiated paneth cells interspersed

transit amplifying cells

undifferentiated but divides very quickly, once out of crypt, differentiate

what kind of cells do stem cells differentiate into

more stem cells, differentiated cells, or both

Lgr5

stem cell marker

one intestinal crypt stem cell can do what

create all types of gut cell and start to form proper shape

paneth cells create the stem cell niche

paneth cell in middle of bottom of crypt expresses wnt, surrounding cells will express EphB

cells not in crypt do not get wnt

notch and Wnt signaling maintain and drive cell diversification

paneth cell expresses delta, surrounding stem cells express notch

daughters of the stem cell turn into transit amplifying cells which are not true stem cells

transit amplifying cells exhibit lateral inhibition, one expresses delta and results in secretory cell, the other activated notch and results in two absorptive cells

Wnt signaling leads to

expressing of delta and notch

activated _____ prevents differentiation

notch

bone marrow stromal cells are fibroblasts that are multipotent, referred to as _____

mesenchymal stem cells

cartilage cells

chondrocytes

cartilage matrix

uniform and highly hydrated

cartilage growth

chondrocyte division

bone cells

osteocyte, osteoblast, osteocast

bone matrix

dense and rigid

bone growth

apposition- outward like a tree

osteocyte

bone cell surrounded by calcium phosphate

osteoid

new, uncalcified bone matrix

osteoblasts

give rise to osteocytes

how do bone cells form

osteoblast sits, builds up the matrix around it, the matrix calcifies, osteoblast is now osteocyte

lacuna

hole in bone where body of the cell sits

canaliculi

tunnels where the arms of the cells sit in bones

how do osteoclasts remodel bone

they spit out acid & proteases that eat matrix proteins

they chew up bone so that it can regenerate

they can also excavate tunnels through old bone to make way for new blood vessels

what do blood cells come from

hematopoietic stem cells which can also give rise to osteoclasts

red blood cells are called

erythrocytes

white blood cells are called

leukocytes

chemical signal molecules recruit white blood cells to damaged tissue

when exposed to mediators of inflammation that were released from damaged tissues, white blood cells in capillaries chemotaxis toward attractants released from damaged tissue, white blood cells escape capillary and crawl through connective tissue with lamellipodium

identifying hematopoietic stem cells

x-irradiation halts blood cell production of mouse, mouse given injection of bone marrow cells from healthy donor, mouse survives because the donor stem cells colonize its hematopoietic tissues and generate a steady supply of new blood cells

commitment is a stepwise process

multipotent hematopoietic stem cell to multipotent hematopoietic progenitor, to committed progenitor, to differentiated cells

what are the factors that regulate hematopoiesis

stem cell niche, erythropoietin

stem cell niche

kit on stem cell bound to kit ligand on stromal cell

when in contact, won’t differentiate

what are the two other names for kit ligand

SCF- stem cell factor

steel

erythropoietin

boosts production of red blood cells in response to low oxygen or erythrocyte shortage

colony stimulating factors (CSFs)

promote growth of colonies of differentiated blood cells

parameters CSFs can control

frequency of stem-cell division

probability of stem cell death

probability that stem-cell daughter will become committed progenitor cell of given type

division cycle time of committed progenitor cell

probability of progenitor cell death

number of committed progenitor cell divisions before terminal differentiation

lifetime of differentiated cells

autologous stem cell transplants

self transplant

take stem cells from patient, multiply in culture, transplant into patient

hope that stem cells are free from cancer mutation

allogenic stem cell transplant

from a donor

risks rejection

donor immune system attacks

satellite cell

stem cell that sits on top of skeletal muscle fiber

satellite cell process

damage to muscle fiber activates satellite cell to divide into muscle progenitor cells which fuse back into the muscle and regenerate muscle fiber

examples of regeneration

planarian worms, newt limbs, pancreas beta cells, liver hepatocytes

what tissues are not renewable

auditory epithelium, retinal epithelium, and some nerve cells in brain

transplanted cell memory

remain largely faithful to their origins

cell reprogramming

nuclei can be reprogrammed, embryonic stem cells can generate any part of body, fibroblasts can be reprogrammed to be pluripotent

what part of the cell decides what type it is?

the cytoplasm

transcription factors are found here and can reprogram the nucleus

embryonic stem cells

come from the inner cell mass of fertilized egg

pluripotent- cannot form placenta

to get ES cells

fertilize egg cell in vitro, harvest inner cells causing destruction of embryo

what is the problem with making iPS cells

inefficient and slow

very hard to make and not all cell types will go all the way when treated

what are the four transcription factors used to create iPS cells

Klf4, Myc, Sox2, Oct4

what is the result of treating cells with Klf4, Myc, Sox2, and Oct4

upregulation of embryonic stem cell genes

upregulation of cell proliferation

loosening of chromatin structure

down regulation of differentiation genes

major events in iPS reprogramming

loss of fibroblast specific marker protein

gain of embryonic marker protein

endogenous oct4 gene switched on

uses of iPS cells

can test what drug would work the best for a specific patient

use gene targeting to repair disease-causing mutation

pros of iPS cells

avoid tissue rejection by immune system

allow for study of diseases ranging from many cell types

avoid moral debate/regulation

cons of iPS cells

production is inefficient

cell memory