Study Set Content:
In situations where the proliferative capacity of hepatocytes is impaired, such as after chronic liver injury or inflammation, progenitor cells in the liver contribute to repopulation.
Liver regeneration from progenitor cells
Steps in Scar Formation:
- Inflammation
- Cell Proliferation
- Formulation of granulation tissue
- Deposition of connective tissue
Breakdown products of complement activation, chemokines released from activated platelets;
Inflammation
In the next stage, which takes up to 10 days, several cell types, including epithelial cells, endothelial and other vascular cells, and fibroblasts, proliferate and migrate to close the now clean wound.
Cell Proliferation
respond to locally produced growth factors and migrate over the wound to cover it up.
Epithelial Cells
proliferate to form new blood vessels, a process known as angiogenesis.
Endothelial cells & Pericytes
proliferate and migrate into the site of injury and lay down collagen fibers that form the scar.
Fibroblast
Migration and proliferation of fibroblasts and deposition of loose connective tissue together with the vessels and interspersed mononuclear leukocytes, form granulation tissue
Formation of Granulation Tissue
derives from the pink, soft, granular gross appearance, such as that seen beneath the scab of a skin wound.
Granulation Tissue
Granulation tissue is progressively replaced by deposition of collagen.
Deposition of connective tissue
The amount of connective tissue increases in the granulation tissue, eventually resulting in the formation of ____
stable fibrous scar
is the process of new blood vessel development from existing vessels.
Angiogenesis
Angiogenesis involves sprouting of new vessels from existing ones and consists of the following steps
- Vasodilation
- Separation of pericytes
- Migration of endothelial cells
- Proliferation of endothelial cells
- Remodeling into capillary tubes
- Recruitment of periendothelial cells
- Suppression of endothelial proliferation
in response to nitric oxide and increased permeability induced by vascular endothelial growth factor (VEGF).
Vasodilation
from the abluminal surface and breakdown of the basement membrane to allow formation of a vessel sprout.
Separation of pericytes
pericytes for small capillaries and smooth muscle cells for larger vessels) to form the mature vessel
Recruitment of periendothelial cells
The laying down of connective tissue occurs in two steps
- migration and proliferation of fibroblast
- deposition of ecm proteins
the most important cytokine for the synthesis and deposition of connective tissue proteins
TGF-β
promotes vasodilation by stimulating the production of NO and contributes to the formation of the vascular lumen.
VEGF (Vascular Endothelial Growth Factor)
The process of angiogenesis involves
- several signaling pathways
- cell-cell interactions
- ECM proteins
- tissue enzymes
