EXTRACELLULAR MATRIX (ECM) AND CELL-MATRIX INTERACTIONS. The ECM is a dynamic, constantly remodeling macromolecular complex synthesized locally, which assembles into a network that surrounds cells. It constitutes a significant proportion of any tissue.
1- Interstitial Matrix:
2- The basement membrane:
1- Mechanical support for cell anchorage and cell migration
2-maintenance of cell polarity
3- Control of cell growth
4- Maintenance of cell differentiation
5- Scaffolding for tissue renewal.
6- Establishment of tissue microenvironments.
7- Storage and presentation of regulatory molecules: FGF and HGF are excreted and stored in the ECM. This allows the rapid deployment of growth factors after local injury
(1) fibrous structural proteins such as collagens and elastins, which confer tensile strength and recoil
(2) water-hydrated gels such as proteoglycans and hyaluronan, which permit resilience and lubrication
(3) adhesive glycoproteins that connect the matrix elements to one another and to cells
a huge molecule composed of many disaccharide repeats without a protein core, is also an important constituent of the ECM. Because of its ability to bind water, it forms a viscous, gelatin-like matrix
1- tissuefibronectinformsfibrillar aggregates at wound healing sites
2- plasmafibronectin binds to fibrin to form the provisional blood clot of a wound, which serves as a base for ECM deposition and re-epithelialization
Mature scar tissue matrix, eventually resulting in the tissueGranulation tissue
Note: Blue represents collagen fibers stained by trichrome stain
1- Vasodilation in response to NO and increased permeability of the preexisting vessel induced by vascular endothelial growth factor (VEGF)
2- Migration of endothelial cells toward the area of tissue injury
3- Proliferation of endothelial cells
4- Inhibition of endothelial cell proliferation and remodelinginto capillary tubes
5- Recruitment of periendothelial cells (pericytes for small capillaries and smooth muscle cells for larger vessels) to form the mature vessel
1- is a potent fibrogenic agent.
2-TGF-β inhibits lymphocyte proliferation and can have a strong anti-inflammatory effect.