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1. ROLE OF
ENDOTHELIAL CELL
IN HEALTH &
DISEASE
SWEETY KALANTRI

4. Simple Squamous epithelium
(monolayer)
Thinnest possible type of membrane

5.  Endothelium is thin layer of cells which lies the interior
surface of blood vessels and lymphatic vessels
 Cells which form endothelium are called endothelial cells
(EC’s)
 Mesodermal in origin
 It forms an interface between circulating blood/lymph in
the lumen and rest of the vessel wall
 Most quiescent & genetically stable cells of the body-
turnover time usually 100 days

6. HISTORY
 Endothelium- 1st described by Virchow in capillaries
as a simple membrane with flattened nuclei
 Swiss Anatomist Wilhelm His- introduced the term
“endothelium”
 Waldayer -suggested the term restricting to those
cells that make up the innermost layer of blood
vessels and lymph vessels & posterior lining of cornea
 1st pro-angiogenic factor (bFGF)- purified in 1984
from tumor cells by Sching & Klagsbrun

8. The vascular wallThe vascular wall

9. Endothelial cells
Liver
/Sinusoidal

10. EMBRYOGENESIS

11.  Earliest blood vessels develop from Blood islands
(insulae sanguineae) which appear in mesoderm
surrounding the wall of the yolk sac at 3 weeks of
development

12. Centre of blood islands form
Hematopoeitic stem cells
( Precursor of all blood cells)
Peripheral hemangioblasts form
Mesodermal cells
HEMANGIOBLAST
ANGIOBLAST(Precursor
of blood vessels
FGF- 2
VEGF

13.  Angioblasts proliferate and eventually induced to form
EC’s (by VEGF, secreted by surrounding mesoderm cells)
 Once process of vasculogenesis estalishes a primary
vascular bed, additional vasculature is added by
angiogenesis, the sprouting of new vessels (by VEGF)
 Maturation & modeling of the vasculature is regulated
by other GF’s ( PDGF, TGF-b )

14. VEGF- A

15. VEGF
 Signalling protein- Mediates both vasculogenesis &
angiogenesis
 Stimulates-- EC mitogenesis
EC migration
Enhances microvascular permeability (aka
Vascular permeabilty factor
VEGF
VEGFR’s( tyrosine kinase receptors )- present on cell surface

16. VEGFR-2/
Flk 1/KDR
Mediates lymphangiogenesis

17. VEGF
Receptor
KDR ( kinase insert domain
receptor 2)- It is human gene
encoding Flk-1
VEGFR-2
KDR is designated as
CD 309
Flk -1
(fetal liver
kinase 1)

18.  Expression of flk-1 represents the earliest marker of
the developing endothelial lineage during
vasculogenesis
 SCL (Stem cell leukaemia) transcription factor/
TAL- 1 i.e T-cell acute lymphocytic leukaemia=
crucial for the development of blood cells and blood
vessels
 AC 133 / / Prominin - 1= Useful marker for
isolation of hematopoeitic & endothelial progenitor cell
 (homeobox gene)- marker for both
hemangioblast and angioblast
present only in endothelial precursors
flk-1
SCL
CD 133
Hex

21. CD133 is absent on mature endothelial cells and monocytic cells

23. Microvasculature (Capillaries & post capillary venules
EC’s Pericytes
• Contractile function
• Multipotential capabilities- differentiate
to adipocytes, osteoblasts, phagocytes,
SMC’s
• Pericytes & SMC’s recruit to form
periendothelial layer- for vessel
maturation & stabilisation
• Imp for BBB formation
/ Mural /Rouget cells

24. STRUCTURE
 Epithelial lining of the vascular system
 Almost always Simple squamous epithelium
 EC’s are very flat and elongate, have central nucleus,
thickness is maximum at the level of nucleus(2-3 µm),
10-20 µm in diameter
 Elsewhere-thinner and laminar; in capillaries as thin as
0.2 µm
 Elongated in the direction of the blood flow, especially
in arteries

25.  Cytoplasm is relatively simple with few organelles;
mostly concentrated in the perinuclear zone
 At ultra structural level, they have few characteristic
organelle
e.g.1) transcytotic/ pinocytotic vesicle
2) caveole
3) Weibel-Palade body

26. TRANSCYTOTIC VESICLE :
- in all ECs but particularly present in exchange vessels
- shuttle small amount of extracellular fluid or blood
plasma across the endothelial cytoplasm
-facilitates bulk exchange of dissolved gases, metabolites
and nutrients
-E.g. in the lung capillaries where there is very efficient
movement of gases (carbon dioxide, oxygen and
anaesthetics etc)
.

27. CAVEOLE :
- special type of transcytotic vesicle
- typical in vessels of smooth muscle cells
- vesicular invagination of cell surface
- associated with receptors, enzymes and ion channels

28. WEIBEL-PALADE BODY :
-also known as rod-shaped (micro) tubulated bodies
-characterizes EC’s
- elongated cytoplasmic vesicle(3 x 0.1) µm
single membrane; dense interior,
-stores adhesion molecule,
P- selectin
Von Willebrand factor( vWF )

29. INTERCELLULAR JUNCTION BETWEEN ADJACENT EC’s
Syndesmos

30.  Formed by
Cadherin-
trans membrane gp
 Cell to cell
contact & with
cytoskeleton
 Cadherin 5/
VE cadherin/
Endothelial
specific cadherin

31.  In large arteries &
brain vessels
 Composed of-
Occludin,
Claudin 5,
JAM’s( Junctional
adhesion molecules
 Present more at
the apical region
of the cell
 Function-Seals
neighboring cells
together to prevent
leakage of molecules
between them

32.  c/o Connexons-
mainly of 37, 40, 43
(detected in EC’s)
 Function-cell to cell
junction allowing
passage of small
water soluble ions &
molecules

33. ENDOTHELIAL HETEROGEINITY
 EC’s exhibit different phenotype- both in structure & function
 heterogeneity is linked to both intrinsic, i.e., genetic factor, and
extrinsic factors
 Structural heterogeneity- obtained following electron microscopy
observations where differences in intercellular junctions led to the
classification of-
# continuous endothelium
# fenestrated endothelium
# discontinuous endothelium

34. Endocrine glands,
GI mucosa
Glomerulus
Liver
Spleen
BM

35.  Specialized EC’s of post capillary venules
 plump cuboidal morphology, have large no. of lymphocytes
within their walls, basal lamina is continuous, 7-30µm
A) High Endothelial Venules (HEV)-
 HEVs are found in all secondary lymphoid organs except spleen
 HEVs enable lymphocytes to move in and out of the lymph
nodes from the circulatory system
HEV-expresses addressins (specific adhesion molecules)
eg CD34
Mad CAM1
Attaches to
L-selectin on
Lymphocytes

36. BLOOD BRAIN BARRIER:BBB-
 It is highly selective permeability barrier that prevent the entry of
lipid insoluble substances to enter brain, SC & peripheral nerve
 BBB is formed by capillary EC’s which are connected by tight
junctions & relative lack of transcytotic vesicle
 Tightness of barrier depends upon the close apposition of
astrocytes (astrocyte cell projections surround the EC’s of BBB)
 Circumventricular organs lack it.

37. LUNG :
 respiratory membrane
 have a selective phagocytic activity & are able to extract
substances from blood
KIDNEY :
 finely fenestrated : functions as a selective filter
 Principle barrier(≈33µm)--is the BM, the fused endothelium &
podocyte basal lamina
 And allows the passage of water, small molecules & ions; but not
larger & those with -ve charge

39. /PECAM-1
Receptor
for TGF-b
/CD105

40.  7B4 antigen
 ACE (angiotensin-converting enzyme)- endothelial enzyme
 BNH9/BNF13
 CD31(PECAM-1)
 CD34 (Gly CAM 1)
 CD54 (ICAM-1)
 CD106 (VCAM-1)
 CD62P (p-Selectin GMP140)
 CD105 (Endoglin)
 CD146 (P1H12)
 E-selectin
 Endothelial cell autoantibodies
 Endoglyx-1
FEW MARKERS

41.  Endosialin (tumor endothelial marker 1, TEM-1, FB5)
 (VEGFR-1)
 ICAM-2 (intercellular adhesion molecule 2)
 Thrombomodulin (TM, CD141)
 VEGF (Vascular endothelial growth factor)
 vWF (von Willebrand factor)

42. CLINICAL ASSESSMENT OF ENDOTHELIAL
FUNCTION
 by both invasively and non- invasively
 involves evaluating measure of endothelial cell behavior
in vivo viz endothelium dependent vasodilatation
 done using either pharmacological or mechanical
agonist that stimulates endothelium to release effector
molecules that alter underlying SM cell tone.

43. INVASIVE PROCEDURE :
 agonist that stimulate release of endothelial NO is
used e.g. acetyl choline & methacholine (short lived
rapidly acting )
 intracoronary infusion is given
 Change in coronary diameter is measured

44. NON- INVASIVE PROCEDURE :
 Assessed in the forearm circulation
 Brachial artery blood flow is occluded with a BP cuff
 Then cuff is deflated
 change in blood flow and diameter is measured ultrasonographically
 depends upon -
-shear stress-dependent changes in endothelial release of NO
following restoration of blood flow &
-the effect of transient adenosine released from ischemic tissue.

45. RESULTS:
 Normally the change is approx. 10%
 Endothelial dysfunction( ED) is defined by- smaller
change & in extreme cases ,a paradoxical
vasoconstriction effect is also seen.
 Occurs due to direct effect of cholinergic agonist on
vascular SMC
 ED seen in pat with atherosclerosis & risk factors(HTN,
↑cholesterolemia, DM, smoking etc.)

47. PERMEABILITY BARRIER & TRANSPORT
 provide barrier between the blood and rest of the body
tissues
 Simple diffusion- O2, CO2
 Active transport- Glucose, AA’s, electrolytes
 Pinocytosis- small molecules, soluble proteins
 Receptor mediated endocytosis (clathrin dependent
process)-
GF’s, Antibodies, LDL, Transferrin, MHC complexes

48. SYNTHESIS OF-
 Role in VASOMOTION-
1. Prostacyclin (PGI2)
2. Endothelium derived hyperpolarizing factor( EDHF)
3. Nitric oxide (NO)/ (EDRF)
Vasodilator
factors
1. Endothelin-1
2. Thromboxane (TXA2)
3. Angiotensin II
Vasoconstrictive
factors
NOS 3 subtype present in EC’s

49.  Secretes ECM protein-
1. Basal lamina- collagen, laminin, elastin, fibronectin
2. Glycocalyx - Proteoglycans
• Smoothness of endothelial surface- due to glycocalyx
• Negative charge on EC’s – due to GAG’s (mainly heparan
SO4)
(EC’s binds to ECM via Integrin)
 Secretion of growth stimulating factors-PDGF, FGF, GM-
CSF
 Secretion of growth inhibiting factors- heparin, TGF- β
 Secretion of IL-1, IL-6, IL-8

50. PECAM 1 (CD31)-
 found on the surface of endothelial cell intercellular junctions,
platelets, monocytes, neutrophils, macrophages,
lymphocytes, megakaryocytes
 involved in leukocyte transmigration, angiogenesis
& integrin activation
VCAM-1 (CD106)-
 expressed on both large and small blood vessels only after EC’s are
stimulated by cytokines
 mediates the adhesion of lymphocytes, monocytes, eosinophil,
and basophils to vascular endothelium
 Major BM addressin for hematopoeitic progenitor cells expressing
VLA-4 / integrin α4β4

51. ICAM (CD54)-
 is expressed by the vascular endothelium, macrophages,
and lymphocytes.
 is a ligand for LFA-1 (integrin) , a receptor found on
leukocytes.
 stabilizing cell-cell interactions and facilitating leukocyte
endothelial transmigration

52. HEMOSTATIC FUNCTIONS-
Intact endothelium
Homeostatic Phenotype
Damaged endothelium
Dysfunctional phenotype

53.  Anticoagulants- production of Thrombomodulin (CD141)-
(co-factor for thrombin)
 Anti thrombogenic agents- production of prostacyclin,
heparin, t PA, anti thrombin III
 Pro thrombogenic agents( released after damage to cells)-
# tissue thromboplastin, vWF, PAI
Clotting
Role in CLOTTING-

54. Role of EC in normal hemostasis

55. INFLAMMATION
 Leucocyte normally repelled by endothelium(for free
flow of blood )
 Inflammatory states - leucocytes are attracted to the
endothelium by leucocyte adhesion molecules( expressed
on EC’s)- leucocyte Margination
 They leucocyte pass by diapedesis
 Hallmark of inflammation- Increased vascular permeability
→ edema
 Vascular leakage occurs due to contraction of EC (M.C.)

57. ENDOTHELIUM AS AN ORGAN
 1-2 trillion EC’s, forming an almost 1.5 kgs organ
 Uniquely contains Weibel-palade bodies (stores vWF)
 Not only a permeability barrier, also multifunctional
paracrine & endocrine organ
 Involved in-
immune response,
growth regulation, coagulation
production of extracellular matrix components
modulator of blood flow & blood vessel tone

58. ROLE IN DISEASE
 Oxidative Stress leads to Endothelial dysfunction (ED)
 ED- 1) decreased NO
2) increased Endothelin ( ET-1 binds to Endothelin A and
B receptors in pulmonary vascular bed- potent vasoconstrictor)
 It is also a physiological process
 Takes place gradually by age and menopause.

60. ENDOTHELIUM IN CVS DISEASE

61.  Disease of large & medium sized muscular arteries
 Characterized by-
1. ED
2. vascular inflammation
3. Atheroma's/atherosclerotic plaque--build up of
cholesterol, lipids, cellular debris, calcium & fibrin within the
intima.intima

63.  Angiotensin-converting-enzyme(ACE) is an endothelial
enzyme
 Converts angiotensinogen I to angiotensinogen II
 A II is a potent vasoconstrictor: important in
pathogenesis of hypertension
Hypertension

64. SMOKING
 Nicotine- opens up intercellular junction & allow large
molecules to pass through the wall
 Such toxins can potentiate degenerative changes in
the blood vessels & lead to vascular disease
 Prolonged( years ) smoking of one pack of cigarettes
daily or more –daily, increase death rate from IHD by
200%
 Smoking cessation decreases that risk substantially

65. ENDOTHELIUM & STROKE
 Production of EDCF- counteracts the normal dilator
effect of NO
 Reduced activity of NO synthase
 Presence of Hemoglobin in SAH-
# inhibition of NO- vasospasm

66. DIABETES

67.  ENDOTHELIUM & CKD

68. ENDOTHELIUM & SEPSIS

69.  TTP & HUS are caused by insult that activates platelets
& deposited as thrombi in microcirculation
 Superimposition of endothelial injury may further
promote platelet micro aggregate formation : initiate
or exacerbate
Thrombotic microangiopathies

71. PHYSIOLOGICAL ANGIOGENESIS

72. TUMOR ANGIOGENESIS

73.  In disease , EC growth supports metabolic requirement
of tumor beyond few mm : growth of primary &
metastatic tumor
 Several steps=
-stimulation of EC
-degradation of ECM
-proliferation of EC & migration into tumor
-Formation of new capillary tubes
 Tumor vessels are=
-tortuous
-dilated, uneven diameter
-excessive branching &shunting
-lack perivascular cells

74. ANTIANGIOGENIC THERAPY
 Acquired drug résistance of tumor – due to high intrinsic
mutation rate -- major cause of treatment failure
 But ECs are genetically stable ; ECs apoptosis pathway
is intact
 EC provides nourishment to many tumor cells; tumor
growth dependent on angiogenesis
 blockade of a single GF (e.g. VEGF) may inhibit tumor
induced vascular growth

76. von Willebrand disease
 vWF required for interaction & adhesion of platelets to
ECM
 Genetic absence of this factor( AD, rare AR)→von
Willebrand disease

77.  The WHO classification of vascular tumors
A)Benign=
1) Hemangiomas
-sub cut/deep
-capillary
-cavernous
-arteriovenous
-Venous
-intramuscular
-synovial
2) Epitheloid Hemangiomas
3) Angiomatosis
4) Lymphangioma
TUMOR OF ENDOTHELIAL CELLS

78. B) Intermediate (locally aggressive)
-Kaposiform hemangioendothelioma
C) Intermediate (rarely metastasizing)
-retiform hemangioendothelioma
-papillary intralymphatic angioendothelioma
-composite hemangioendothelioma
-kaposi sarcoma
D) Malignant
-Epitheloid hemangioendothelioma
-Angiosarcoma of soft tissue

79.  EC’s play a vital role in health and integrity of every
tissue of the body because
apart from cartilage, every cell lies within a few µm
of a capillary
 The diffusion limit of oxygen in tissue is only ≈
100µm,and can not cross blood vessel thicker than that
 fine capillaries ( 10-15 µm ) & consist merely of
endothelial cells and a very fine basal lamina, thus helps
in providing oxygen, nutrients & metabolites.
Summary

80.  adjust their number & arrangement to accommodate
local requirement
 Thus, they are life-support tissue extending & remodeling
the network of blood vessels to enable tissue growth,
motion & repair.
 Dysfunction of EC has been implicated in virtually
every type vascular disease( Atherosclerosis,HTN etc.)
 and hence integrity & proper function of EC is
essential for proper organ function and good health.

81.  Pathological basis of disease : Robbins & Cotran,8th e
 Harrison’s internal medicine: 17th e
 WHO classification: tumors of soft tissue and bone
 Hematology : Basic Principles & Practise,5th e( Hoffman)
 Hemostasis and Thrombosis –Basic Principles & Practice, 5th e(
Colman , Goldhaber )
 Internet sites
References

82. THANK YOU