Presentation is loading. Please wait.

Presentation is loading. Please wait.

Stem Cells and the Maintenance of Adult Tissues

Similar presentations


Presentation on theme: "Stem Cells and the Maintenance of Adult Tissues"— Presentation transcript:

1 Stem Cells and the Maintenance of Adult Tissues
Chapt Stem cells have great potential Adult stem cells Embryonic stem cells In early development, cells proliferate rapidly, then differentiate to form specialized cells of adult tissues Most differentiated cells in adult animals are no longer capable of proliferation. If cells are lost, replace by proliferation of cells derived from self-renewing stem cells.

2 Stem Cells,Maintenance of Adult Tissues
1. Some differentiated cells can proliferate to repair damaged tissues Fibroblasts in connective tissue proliferate in response to platelet-derived growth factor (PDGF) released at wound Endothelial cells lining blood vessels proliferate to form new blood vessels (repair and regrowth of damaged tissue) Triggered by vascular endothelial growth factor (VEGF), from cells that lack oxygen Fig ,14, 15

3 Stem Cells and the Maintenance of Adult Tissues
2. Adult Stem cells: Less differentiated, self-renewing cells in most adult tissues. Retain capacity to proliferate, replace differentiated cells throughout lifetime of animal. ** Divide to produce one daughter cell that remains stem cell and one that divides, differentiates Ex. blood cells, sperm, epithelial cells skin, intestine Fig

4 specialized functions
Fig Formation of blood cells Hematopoietic (blood-forming) stem cells were the first identified (1961): distinct types specialized functions Short life span from bone marrow

5 Stem Cells and Maintenance of Adult Tissues
Epithelial cells that line intestines live only a few days before they die Fig

6 Stem Cells and the Maintenance of Adult Tissues
Adult stem cells potential utility in medicine. Hematopoietic stem cell transplantation (or bone marrow transplantation) important role in treatment of cancers. Fig Cord blood is source of hematopoietic stem cells Epithelial stem cells - skin grafts for burns, wounds, and ulcers.

7 Embryonic Stem Cells and Therapeutic Cloning
Embryonic stem cells (ES) Grow indefinitely as pure stem cell populations Pluripotency — capacity to develop into all of different types of cells in adult tissues. Enormous interest - basic science and clinical applications. Distinction cloning cells versus cloning organisms

8 Embryonic Stem Cells and Therapeutic Cloning
ES cells first cultured from mouse embryos in 1981. Mouse ES cells important experimental tool: Can introduce altered genes into mice. Model system to study molecular basis of cell differentiation Fig ES cells can differentiate: Martin Expt: neuron-like, endodermal, cartilage

9 Embryonic Stem Cells and Therapeutic Cloning
Mouse ES cells need growth factor LIF, to maintain undifferentiated state (leukemia inhibitory factor) LIF signals through JAK/STAT path If LIF is removed, cells aggregate and differentiate. Different growth factors direct differentiation along specific paths Model for future human therapeutics: Diseases like Parkinson’s, diabetes Human ES cell lines exist Fig

10 Embryonic Stem Cells and Therapeutic Cloning
1997 Dolly the sheep cloned: Somatic cell nuclear transfer process This cloning in mammals is difficult and inefficient Possible therapeutic cloning Fig

11 Embryonic Stem Cells and Therapeutic Cloning
Nucleus from adult human cell transferred to enucleated egg Resulting embryo cells used to produce differentiated cells for transplantation therapy. Bypasses problem of tissue rejection Problems with therapeutic cloning: Low efficiency of generating embryos by somatic cell nuclear transfer. Ethical concerns: Possible cloning of humans (reproductive cloning), destruction of embryos Fig therapeutic cloning for personalized tissue transplants

12 Embryonic Stem Cells and Therapeutic Cloning
Induced pluripotent stem cells: Very recent procedures may overcome technical, ethical difficulties Reprogram somatic cells to resemble embryonic stem cells. Only 4 key transcription factors reprogram adult mouse somatic cells Oct4, Sox2, Klf4, c-Myc) Also adult human fibroblasts Fig


Download ppt "Stem Cells and the Maintenance of Adult Tissues"

Similar presentations


Ads by Google