12.3B Growth Flashcards
Stem cells
unspecialized cells that can become other types of cells, as body needs them
cells that can differentiate into other types of cells, and can also divide in self-renewal to produce more of the same type of stem cells.
- are inside BONE MARROW
- sources: adult body tissues and embryos
What makes stem cells unique?
- stem cells are unspecialized
- self-renewal is the defining property of stem cells
- divide and produce more specialized cell types (differentiation potential)
Totipotent
These stem cells can differentiate into all possible cell types.
The first few cells that appear as the zygote starts to divide are totipotent.
Zygote and morula
Pluripotent
These cells can turn into almost any cell.
Cells from the early embryo are pluripotent.
Blastocyst, fetal and adult cells
Multipotent
These cells can differentiate into a closely related family of cells.
Adult hematopoietic stem cells, for example, can become red and white blood cells or platelets.
Adult cells
Multipotent stem cells type: Oligopotent
These can differentiate into a few different cell types.
Adult lymphoid or myeloid stem cells can do this.
Adult cells
Multipotent stem cells type: Unipotent
These can only produce cells of one kind, which is their own type.
However, they are still stem cells because they can renew themselves.
Examples include adult muscle stem cells.
Adult cells
Embryonic Stem Cells
- pluripotent stem cells
- stable; can undergo MANY cell divisions
- EASY to obtain but blastocyst is destroyed
- POSSIBILITY of rejection
Adult Stem Cells
- multipotent
- LESS stable; capacity for self-renewal is LIMITED
- DIFFICULT to isolate in adult tissue
- host rejection MINIMIZED
Differentiation
- Cell differentiated is under genetic control and involves cell signaling processes
- During differentiation, genes that express proteins important for the function of that cell remain ‘switched on’
- Once a cell becomes specialized, it stops dividing and only expresses the genes are characteristic for that types of cell
Homeotic genes
control development of whole body segments or structures.
When they are overactive or missing, weird things can happen!
encode transcription factor proteins that contain a region called the homeodomain and are called Hox genes.
Stem cells uses
- cosmetology
- medicine:
drug testing, tissue replacement - research
- food
- therapy
Stem cell research
- study cell processes such as growth, differentiation and gene regulation
- the study of diseases and their development
- drug testing
- therapeutic uses in the treatment of diseases such as leukaemia (bone marrow transplant), Hunter’s disease and heart disease
- therapeutic uses in medicine, skin grafts for burns, stem cell grafts for cornea repair
Corneal stem cell therapy
- Stem cells extracted from healthy eye, cultured and transplanted back into the damaged eye
- Repairs cornea
- Shorter waiting time than traditional donation
-
Reduced chance of rejection as patient’s own cells transplanted
Ethical issues surrounding stem cells
- religious reasons
- embryos have human rights
- usage of adult stem cells remain uncontroversial
