What are stem cells ?

Characteristics that distinguish stem cells from other cells They are undifferentiated cells (their job is to become special cells when needed) They can be grown continuously in a culture (stem cell line) They can be changed (using chemicals) to become cells with special functions

Why the name “stem cells”

What controls differentiation? When a cell becomes a special cell type What controls differentiation? Chemicals released by other cells The location of the cells (the stem cell niche)

Day 14 still the size of a pencil tip Cells in the blastocyst migrate to form three layers of cells. Each of these layers are stem cells, but can only become certain types of cells. These cells have begun to differentiate. Day 14 still the size of a pencil tip

All cells have the same genes (information) However, eye cells differ from nose cells So how do they become different?

Gene Activation: As a cell differentiates, some genes are turned on and some are turned off Only the genes necessary to make the type of cell needed will be working. Like a computer with all information, but only certain programs are turned on, others are off

Cells in the embryo continue to migrate and differentiate. 19-26 Days Cells in the embryo continue to migrate and differentiate. The brain and spinal cord begin to form.

By 4 weeks the heart is beating. 4 weeks 1/6 inch By 4 weeks the heart is beating. Cells are still differentiating.

5 weeks 1/6 inch

6-8 weeks ½ inch

12-16 Weeks 2.5 inches ½ ounce

Two basic types of stem cells: Embryonic stem cells (ESC)- obtained from fertilized eggs left over from in vitro fertilization (IVF). Collected from the inner cell mass (ICM) Original 30 cells yield millions of embryonic stem cells Batches of them can be frozen and shipped to other laboratories

ESC’s Scientists have "recipes" of chemicals for the differentiating ESC’s into specific cell types approx. 30 cells

Adult stem cells (ASC) - both children and adults have them in specific areas (niche) The cells divide and differentiate when needed One cell always remains a stem cell

Regenerative Medicine https://www.youtube.com/watch?v=_GyQWAiDu0w Short version 2 minutes https://www.youtube.com/watch?v=O_OI4TtzlDw Longer version 4 minutes