BMS314 Lecture Notes - Lecture 15: Cadherin, Pleiotropy, Morphogenesis
Outcomes of Injury
1. The injury overwhelms the patient and they die
2. The acute inflammatory response removes the injured tissue and any noxious agent, then the
tissue heals
3. The acute inflammatory responses fail to remove the injured tissue or a noxious agent persists,
then the inflammation becomes chronic
Healing/Repair and Regeneration
Healing/Repair: restoration of tissue architecture and function after injury
• Often if an organ is injured it cannot replace itself to what it was before injury (some form of
changes)
• Variable amounts of regeneration, and tissue replacement by connective tissue scar
Regeneration: proliferation of residual cells and maturation of stem cells
Healing, Regeneration and Repair
What determines whether a tissue will regenerate or repair?
i. Cellular Factors
ii. Chemical mediators: Growth Factors
iii. Stromal factors: ECM
iv. Additional factors
There is a population dynamic between the constituent cells, inflammatory cells and the structure of
the organs, and all of that works together to determine how much regeneration occurs and how
much scarring occurs
(try to understand how these mechanisms work together to affect healing and repair)
1. Classification of cells by proliferative potential
Labile cells: most epithelial cells and haematopoietic cells
If these cells get damaged they can seamlessly regenerate and repair the injury
Stabile cells: mesencyhmal cells, parenchymal cells (make up the connective tissue matrix). Cells are
in G0 but can be stimulated to return to G1
Can be induced from the resting phase to regenerate
Permanent Cells: cardiac myocytes, neurons (skeletal muscle). Cells have left the cell cycle
Limited regeneration in the body, muscle has to be repaired by scar tissue, impacting function
Cell Cycle
Cells are either actively undergoing mitosis, or are being prepared for mitosis
Stem Cells
1. Embryonic Stem Cells:
• 32 cell stage; pluripotential; asymmetric replication
• All of these cells can be taken out and turned into any type of cell (pluripotential).
Capable of differentiating into any cell type that exist in the body
• When the stem cell divides, one of the daughter cells will differentiate into
something else, while the other daughter cell will remain a stem cell (asymmetric
replication)
2. Adult Stem Cells:
• Bone marrow
• Haematopoietic (HSC), progenitor and stromal; broad differentiation potential
• Tissue Stem Cells
• Located in niches within most organ systems; multipotent adult progenitor cells
(MAPCS)
Organ Regeneration or Repair
1. Labile tissues: Replication or labile cells, niche stem cells
2. Stable cells: Return of stable cells to cell cycle, replication of niche stem cells
3. Permanent cells: limited/no replication of permanent cells or niche stem cells
Essential Cellular Elements of healing
