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'Tensegrity Hypothesis'


A. Matricelluar Protins:

  1. Not structural proteins
  2. Interact with matrix protein, cell surface receptors, other molecules
  3. Can disrupt cell- matrix interactions
    1. SPARC (secreted protein acidic and rich in cysteine)
      a. Tissue remodeling
      b. Absent angiogenesis
    2. Thrombospondin: Absent angiogenesis
    3. Osteopontin: regulates calcification Q ,  - Mediator of leukocyte migration
    4. Tenacin: Involved in morphogenesis & cell adhesion

B. Proteoglycans & Hyaluronans:

  1. Core protein linked to polysaccharides called glycosaminoglycans
  2. Named according to principal repeating disaccharide e.g. Chondroitin sulfate, heparan sulfate, dermatan sulfate
  3. Can also be integral membrane. Proteins, mediate cell growth & differentiation e.g. Syndecans family: Spans plasma membranes
  4. binds collagen, fibronectin, thrombospondin FGF to heparan sulfate - modulates GF activity:      
  5. Associated with actin cyto skeleton which maintain morphology of epithelial sheets

C. Hyalurons: in ECM    

  1. Repeats to disaccharides stretched end to end
  2. Serve as ligand for core proteins. e.g. Cartilage link protein
  3. Associated with cell surface receptors Binds H2O: viscous gel

D. Repair By Fibrosis: Q

  1. Formation of new Blood vessels:
  2. Migration and proliferation of fibroblasts
  3. Deposition of ECM
  4. Maturation and organization of fibrous tissue. Remodelling 'Granulation’ pink soft granular appearance on surface of wounds

E. Angiogenesis: Q

  1. Vasculogenesis: Primitive vascular network during embryonic dev. from angioblasts
  2. Angiogenesis / Neovascularization:
  3. Pre-existing vessels send out capillary binds/ sprouts to produce new vessels
    1. Chr. Inflammation  
    2. Tissue repair           
    3. Malignancies

F. Steps:

  1. Proteolytic degradation of BM of vessels
  2. Migration of endothelial cells towards angiogenic stimulus
  3. Proliferation of endothelial cells behind leading front
  4. Maturation of endothelial cells; Capillary tissue forming
  5. Recurrent of peri endothelial cells to support endothelial tubes

Fibroblast growth factor → is an angiogenic factor

Extracellular matrix proteins as regulators of Angiogenesis are:-

  1. Integrins - which stabilize the membrane
  2. Matricellular proteins examples
    1. -SPARC(secreted protein acidic and rich in cysteine) , tensacin, thrombosporidin → which destablise C-M interaction, promote angiogenesis
    2. Proteases
    3. Endostitis → which decrease angiogenesis (cleavage product)

G. Fibrosis:

  1. Emigration and proliferation of fibroblasts at site of injury - TGF, PDGF, EGF, FGF
  2. Deposition of ECM- affected by collagen deposition / degradation

Table: Vascular Endothelial Growth factor (VEGF)





Migration of endothelial cells

mitosis of endothelial cells

Methane monooxygenase activity

αvβ3 activity

creation of blood vessel lumen

creates fenestrations

Chemotactic for macrophages and granulocytes

Vasodilation (indirectly by NO release)


Embryonic angiogenesis (myocardial tissue, specifically)




Needed for the development of lymphatic vasculature surrounding lung bronchioles


Important for Vasculogenesis, Also needed for angiogenesis during ischemia, inflammation, wound healing, and cancer.

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