1. This presentation will provide a brief introduction into stem cell technology. I hope that you enjoy the lecture. There will be several quiz questions as well to test your comprehension of the material. Best of luck and enjoy the presentation.

2. Learning Objectives
At the conclusion of this lesson you should be able to:
Understand the key terms and definitions regarding stem cells
Differentiate between the adult and embryonic stem cells
Differentiate between mesenchymal and hematopoietic stem cells lineages
Describe the key advantages of mesenchymal stem cells
Describe how mesenchymal stem cells (MSC) differentiate into bone cells to create a bone matrix
These are the learning objectives that will be addressed during this presentation.

3. What Are Stem Cells?
Stem cells have the remarkable potential to develop into many different cell types in the body.
Serving as a sort of repair system for the body, they can theoretically divide without limit to replenish other cells as long as the person or animal is still alive.
When a stem cell divides, each new cell has the potential to either remain a stem cell or become another type of cell with a more specialized function, such as a muscle cell, a red blood cell, or a bone cell.
Source:

4. Stem Cell Potency
A stem cell’s potential is a measure of of the cells ability to differentiate into specialized cells.
Potency Classifications
Totipotent: ability to differentiate into any cell
Pluripotent: descendant of totipotent cells, and can form most cells
Multipotent: ability to differentiate into specialized cells within a lineage
Unipotent : ability to produce only one type of cell

5. Stem Cell Classifications
Adult Stem Cells
Hematopoetic
Multipotent
Mesenchymal (Bone Marrow Stromal)
Embryonic Stem Cells
Early Embryonic
Totipotent
Blastocyst Embryonic
Pluripotent
Fetal Stem Cells
Umbilical Stem Cells
Early, Blastocyst, and Fetal Stem Cells are highly potent, which explains there therapeutic applications. The location of these cells from embryonic tissue make them highly controversial and will inspire debate for some time to come.
In contrast, adult stem cells are multipotent, so there are a limited number of cells they may become. Most important, these cells avoid the debate inspired by embryonic cells.
Source:

6. Stem Cell Classifications
Adult Stem Cells
Potential: Multipotential
Ability to form SPECIFIC cells within a lineage
Can make multiple copies of themselves over a prolonged period
Can give rise to mature cells with specialized functions
Primary Role: Maintain or repair tissue
Categories:
Mesenchymal
Bone, cartilage, fat, muscle, nerve cells
Hematopoetic
Blood Cells
The primary role of Adult Stem Cells are to maintain or repair tissue. Normal wear or injury will signal these cells to begin to differentiate to repair the required tissue.

7. Mesenchymal Stem Cells
MSCs have the ability to differentiate into specialized cells such as nerve, bone, muscle, or cartilage based on the body’s signals.

8. Stem Cell Identification
Cells are identified by their surface markers
Hematopoetic stem cells are CD 34+,45+, while Mesenchymal Stem Cells (MSCs) are CD 34-,45-
Mesenchymal stem cells have CD166 markers among many others.
The key to stem cell based therapy is the identification process for the cells. Every cell contains surface markers or proteins which identify the type of cell and allow the cell to carry out its tasks. There are a vast number of markers on every cell, but scientist can use the commonalities to group cells into families.
Mesenchymal Stem Cells, for instance, have a Cluster Designation or CD marker of 106 and One of the many makers inherent to hematopoetic cells is CD 45.
It is important to note that MSCs lack the CD45 marker.

9. Why is CD34 & 45 relevant?
CD34 and CD45 are a cell surface antigen selectively expressed on human hematopoetic progenitor cells
These antigens can induce an immune response when transplanted into a foreign environment by inducing T-cell activation
That immune response may result in rejection of the tissue

10. Therapeutic Advantages of MSCs
Hypo-immunogenic
Will not illicit an immune response in the recipient
Universal donor
Will differentiate into bone, cartilage, muscle, or fat given the proper signals.

11. Mixed Lymphocyte Reaction
A measure of histocompatability
Lymphocytes from incompatible individuals will stimulate each other to proliferate significantly (immune response)
Tissue is considered compatible if the test does not generate a MLR

12. Mesenchymal Stem Cells
Generate bone, cartilage, fat, and fibrous connective tissue
CD 34- and CD45-
CD 166+
Hypo-immunogenic
MSCs do not illicit an immune response
Prevent T-cell activation
SUMMARY
Mesenchymal stem cells inhibit T cell proliferation, activate suppressor T cells, inhibit homeostatic T cell expansion and can be used as universal donors in some situations due to their hypo immunogenic activities as well as ability to suppress alloreactivity.
Source: Journal of Inflammation 2005, 2:8

13. Bone Healing Process Three distinct and overlapping phases
Early inflammatory phase
Repair phase
Late remodeling phase
Clinically MSCs have a vital role in the healing process. The human has numerous actions that result from osseous disruption be it from normal wear, trauma, disease, or surgery.
There are three distinct phases:
Early Inflammation
Repair Phase
Remodeling Phase

14. Bone Healing Process Inflammatory Stage
Hematoma develops at site of osseous injury
Prostaglandin mediates infiltration of inflammatory cells (macrophages, lymphocytes, etc.)
Granulation tissue forms
Angiogenesis
MSC migration
Process may be inhibited by anti-inflammatory medication
During the inflammatory Stage a hematoma forms which signals a multitude of activity from lymphatics, to blood vessels, to the migration of MSCs.
This highlights the fact that blood flow is an essential component of the healing process. Drugs or substances which impeded inflammation or angiogenesis are detrimental to osseous repair.

15. Bone Healing Process Repair phase
Fibroblasts lay down stroma to support vascular in-growth
Collagen matrix developed
Osteoid secreted and mineralized creating soft callus which ossifies into woven bone
Stabilization essential!
Process inhibited by nicotine
MSCs differentiate into osteoblasts and become quiescent
During the Repair Phase, a callus develops and stabilization is essential as the tissues develop and repair.
MSCs differentiate into osteoblasts and become quiescent (dormant).

16. Bone Healing Process Remodeling Phase
Bone reformed to original shape, structure, and strength
Strength influenced by axial loading
3-6 months
Osteocytes are incorporated into the matrix
During the final remodeling phase the bone is reformed by osteoblasts and osteoclasts to its original structure and shape. In accordance with Wolff’s law, the strength of the bone is influenced by axial loading. Osteocytes are incorporated into the lacunae of the bone cortical bone.

17. Your first question please…
This concludes this lecture. If you have any additional questions, please never hesitate to contact your education manager. Best of luck!