Computer Science 129 Stem Cells

Stem Cells There are two types of stem cells Embryonic Stem Cells Adult Stem Cells To figure out where they come from we need to understand a little embryology

Stem Cells http://www.youtube.com/watch?v=rN3lep6roRI Watch the above video until part 5 (watch the first 16 minutes)

Stem Cells

Stem Cells Cells from a morula are considered totipotent – they can develop into anything embryonic or extra-embryonic Cells from the inner cell mass are called pluripotent – they can be anything except trophoblast cells Once a cell has differentiated they are multipotent – ex. Ectoderm can become skin, brain or nervous tissue – multiple things

Stem Cells

Stem Cells Fertilization occurs in the fallopian tubes of a woman (uterine tubes) When the sperm combines with the ovum, we have a zygote The zygote undergoes cell division and we end up with a ball of cells called the morula The morula develops into a blastocyst with the inner cell mass inside

Stem Cells The cells on the outside of the blastocyst are called trophoblasts. These cells protect the inner cell mass, which is the developing embryo, from the mother’s immune system (the mother’s immune system views the developing embryo as foreign since half of it is from the father – actually it is 51% mom and 49% dad because of the mitochondrial DNA from mom makes it a little more mom than dad)

Stem Cells The inner cell mass, which is developed at around day 7-10, is where scientists harvest embryonic stem cells These cells have not differentiated, or become determined at this point. When cells become determined, it is “determined” what they will become when they grow up. The cells will become endoderm, mesoderm or ectoderm

Stem Cells The following table indicates the type of cells that each of the germ layers will ultimately develop into

Stem Cells Germ Layer Structures they become Ectoderm Epidermis – outer layer of skin Brain, spinal cord, nerves Mesoderm Bones, muscle, dermis-lower layers of skin, blood, connective tissue, reproductive tissue, urinary tissue (basically everything else that is not from endoderm or ectoderm) Endoderm Linings of the guts and associated organs and linings of lungs and respiratory tissues

Stem Cells Once a cell has become determined, or become a germ layer, they will continue to develop into those tissue types. You can not make an endoderm cell become brain tissue or mesoderm become guts and so on. If a cell is gotten before it is determined, it can be forced to become any tissue. They are metabolically more active as well.

Stem Cells It is no longer legal to make embryos for the purpose of destroying the embryo to do stem cell work. Where do scientists get them then? Unused embryos from fertility clinics Wharton’s jelly on the placenta

Stem Cells Use of stem cells from Wharton’s jelly is ideal since there is no destruction of an embryo involved.

Stem Cells What about Adult Stem Cells? Where can we harvest those? Adipose tissue (fat) Skin Spinal fluid Heart cells Liver cells Brain Bone marrow Teeth