Endothelium in health and diseases

1. ENDOTHELIUM IN HEALTH AND
DISEASE
CHAIR PERSON: DR. AMEET . K
STUDENT : Dr. Vasanti .K

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

5.  Endothelium is thin layer of cells which lies theinterior
surface of blood vesselsand lymphatic vessels.
 Cellswhich form endothelium are called endothelialcells
(EC’s)
 Mesodermal in origin.
 It forms an interface between circulating blood/lymphin
the lumen and rest of thevesselwall.
 Most quiescent & genetically stable cells ofthe body-
turnover time usually 100days.

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

8. THE VASCULAR
WALL

9. Endothelial cells
/Sinuso
Liver

10. EMBRYOGENESIS

11. Centre of blood islands form
Hematopoeitic stemcells
( Precursor of all bloodcells)
Peripheral hemangioblasts form
Mesodermal cells
HEMANGIOBLAST
ANGIOBLAST(Precursor
of bloodvessels
FGF-2
VEGF

12.  Angioblasts proliferate and eventually induce to form
EC’s(by VEGF,secreted by surrounding mesodermcells)
 Once process of vasculogenesis estalishes aprimary
vascular bed, additional vasculature is added by
angiogenesis, the sprouting of new vessels(byVEGF)
 Maturation & modeling of thevasculature is regulated
by other GF’s( PDGF, TGF-b)

13. VEGF-A

14. VEGF
 Signalling protein- Mediates both vasculogenesis&
angiogenesis.
 Stimulates– EC mitogenesis
EC migration
Enhancesmicrovascular permeability/
Vascularpermeabilty factor
VEGF
VEGFR’s(tyrosine kinase receptors )- present on cellsurface

15. VEGFR-2/
Flk1/KDR
Mediates lymphangiogenesis

19. Microvasculature (C
EC’s
• Cont
• Multipotential capabilities- differentiate
to adipocytes, osteoblasts,phagocytes,
SMC’s
• Pericytes & SMC’srecruit to form
periendothelial layer- for vessel
maturation & stabilisation
apillaries & post capillary venules
Pericytes / Mural /Rouget cells
ractile function

21. STRUCTURE
ysSimple squamous epithelium
flat and elongate, have central nucleus,
aximum at the level of nucleus(2-3 µm),
diameter
hinner and laminar; in capillaries asthin as
the direction of theblood flow, especially
 Epithelial lining of the vascularsystem
 Almost alwa
 EC’sare very
thickness is m
10-20 µm in
 Elsewhere-t
0.2 µm
 Elongatedin
in arteries

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

24. TRANSCYTOTICVESICLE:
- in all ECsbut particularly present inexchangevessels
- shuttle small amount of extracellular fluid or blood
plasma acrossthe endothelial cytoplasm
-facilitates bulk exchange of dissolved gases,metabolites
and nutrients
-E.g.in the lung capillaries where there is veryefficient
movement of gases(carbon dioxide, oxygen and
anaesthetics etc)
.

25. CAVEOLE:
- Special type of transcytoticvesicle
- Typical in vesselsof smooth musclecells
- Vesicular invagination of cellsurface
- Associated with receptors, enzymesand ion
channels

26. WEIBEL-PALADEBODY:
-also known asrod-shaped (micro) tubulated bodies
-characterizes EC’s
- elongated cytoplasmic vesicle(3 x0.1) µm
single membrane; dense interior,
-stores adhesion molecule,
P-selectin
VonWillebrand factor( vWF )

27. INTERCELLULAR JUNCTION BETWEENADJACENT EC’s
Syndesmos

28.  Formedby
Cadherin-
trans membranegp
 Cell to cell
contact & with
cytoskeleton
 Cadherin 5/
VEcadherin/
Endothelial
specific cadherin

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

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

31. ENDOTHELIALHETEROGEINITY
 EC’sexhibit 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 tothe
classification of-
# continuous endothelium
# fenestrated endothelium
# discontinuous endothelium

32. Endocrine glands, Liver
GI mucosa Spleen
Glomerulus BM

33. BLOOD
 It is high
lipid inso
 BBBis fo
junction
 Tightne
astrocyte
 Circumve
BRAINBARRIER:BBB-
ly selective permeability barrier that prevent the entryof
luble substances to enter brain, SC& peripheralnerve
rmed by capillary EC’swhich are connected bytight
s& relative lack of transcytoticvesicle
ssof barrier depends upon the close appositionof
s(astrocyte cell projections surround the EC’sof BBB)
ntricular organs lackit.

34. BLOOD BRAIN BARRIER

35. LUNG:
 Respiratory membrane
 Have aselective phagocytic activity & are able toextract
substances from blood
KIDNEY:
 Finely fenestr
 Principle barr
podocyte ba
 And allows t
larger & thos
ated : functions asaselective filter
ier(≈33µm)--is the BM, the fused endothelium&
sal lamina
he passageof water, small molecules &ions; but not
e with -vecharge

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

39. 7B4antigen
ACE(angiotensin-converting enzyme)- endothelial enzyme
BNH9/BNF13
CD31(PECAM-1)
CD34(Gly CAM 1)
CD54(ICAM-1)
CD106(VCAM-1)
CD62P(p-SelectinGMP140)
CD105(Endoglin)
CD146(P1H12)
E-selectin
Endothelial cell autoantibodies
Endoglyx-1
FEW MARKERS

40.  Endosialin (tumor endothelial marker 1, TEM-1,FB5)
 (VEGFR-1)
 ICAM-2 (intercellular adhesion molecule2)
 Thrombomodulin (TM,CD141)
 VEGF(Vascular endothelial growthfactor)
 vWF(von Willebrand factor)

41. CLINICALASSESSMENTOFENDOTHELIAL
FUNCTION
 by both invasively and non- invasively
 involves evaluating measure of endothelial cellbehavior
in vivo viz endothelium dependentvasodilatation
 done using either pharmacological or mechanical
agonist that stimulates endothelium to releaseeffector
molecules that alter underlying SMcelltone.

42. INVASIVEPROCEDURE:
 Agonist that stimulate release of endothelial NOis
used e.g. acetyl choline & methacholine (shortlived
rapidly acting )
 Intracoronary infusion is given
 Changein coronary diameter ismeasured

43. NON-INVASIVEPROCEDURE:
 Assessedin the forearmcirculation
 Brachial artery blood flow is occluded with aBPcuff
 Then cuff isdeflated
 change in blood flow and diameteris measured ultrasonographically
 depends upon -
-shear stress-dependent changes in endothelial release of NO
following restoration of blood flow&
-the effect oftransient adenosine released from ischemic tissue.

44. RESULTS:
Normally the change is approx. 10%
Endothelial dysfunction( ED)is defined by- smaller
change & in extreme cases,a paradoxical
vasoconstriction effect is alsoseen.
Occursdue to direct effect of cholinergic agonist on
vascular SMC
EDseenin patients with atherosclerosis & risk
factors(HTN,↑cholesterolemia, DM, smoking etc)

46. PERMEABILITY BARRIER & TRANSPORT
 Provide barrier between the blood and rest ofthe
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, MHCcomplexes

47. SYNTHESIS
OF- NO
le in VASOMOTION-
Vasodilator
rostacyclin (PGI2) factors
ndothelium derived hyperpolarizing factor( EDHF)
itric oxide(NO)/ (EDRF)
Endothelin-1 Vasoconstrictive
Thromboxane (TXA2) factors
Angiotensin II
 Ro
1. P
2. E
3. N
NOS3 subtype present inEC’s
1.
2.
3.

48.  SecretesECMprotein-
1. Basallamina- 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’sbinds to ECMviaIntegrin)
 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

49. PECAM1(CD31)-
 found on the surface of endothelial cell intercellularjunctions,
platelets, monocytes, neutrophils, macrophages,
lymphocytes, megakaryocytes
 involved in leukocyte transmigration,angiogenesis
& integrinactivation
VCAM-1(CD106)-
 expressed on both large and small blood vessels only after EC’ are
stimulated bycytokines
 mediates the adhesion of lymphocytes, monocytes,eosinophil,
and basophils to vascularendothelium
 Major BM addressin for hematopoeitic progenitorcells expressing
VLA-4/ integrinα4β4

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

51. HEMOSTATICFUNCTIONS-
Intact endothelium
Homeostatic Phenotype
Damagedendothelium
Dysfunctional phenotype

52.  Anticoagulants- production of Thrombomodulin (CD141)-
(co-factor for thrombin)
 Anti thrombogenic agents- production of prostacyclin,
heparin, T PA, anti thrombinIII
 Pro thrombogenic agents( released after damage to cells)-
Tissue thromboplastin, vWF, PAI
ROLE IN CLOTTING

53. Roleof ECin normalhemostasis

54. 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
 Theleucocyte passby diapedesis.
 Hallmark of inflammation- Increased vascularpermeability
→edema
 Vascularleakage occurs due to contraction of EC(M.C.)

56. ENDOTHELIUM AS ANORGAN
 1-2 trillion EC’s, forming an almost 1.5 kgsorgan
 Uniquely contains Weibel-palade bodies (stores vWF)
 Not only apermeability barrier, alsomultifunctional
paracrine & endocrineorgan
 Involved in-
immune response,
growth regulation, coagulation
production of extracellular matrixcomponents
modulator of blood flow &blood vesseltone

57. ROLE INDISEASE
 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.

59. ENDOTHELIUM IN CVS DISEASE

63.  Angiotensin-converting-enzyme(ACE) is an endothelial
enzyme
 Converts angiotensinogen I to angiotensinogenII
 ANGIOTENSIN II is apotent vasoconstrictor
important in pathogenesis of
HYPERTENSION
Hypertension

64. ENDOTHELIAL
DYSFUNCTION
NADPH
OXIDASE
ROS
NITRIC OXIDE
PRODN OF ET 1PROSTANOIDS
OXIDATIVE
STRESS
VASCULAR
TONE
HYPERTENSION

65. SMOKING
 Nicotine- opens up intercellular junction & allow
large molecules to passthrough the wall.
 Such toxins canpotentiate degenerative changes
in the blood vessels& lead tovascular disease.
 Prolonged( years ) smoking of one pack of cigarettes
daily or more –daily, increase death rate from IHD by
200%
 Smoking cessation decreasesthat risk substantially.

66. SMOKING
Endothelial
dysfunction
TOXINS, FREE
RADICALS
ENDO
APOPTOSIS
.PLATELET
AGGREGN
.MONOCTYE
ADHESION
.COAGULABILI
TY OF BLOOD.
ATHEROSCLEROSIS,
CAD,PVD

67. ENDOTHELIUM & STROKE
 Production of EDCF-counteracts the normal
dilator effect of NO
 Reducedactivity of NOsynthase
 Presenceof Hemoglobin in SAH-
 inhibition of NO- vasospasm

68. DIABETES

69. L- ARGININE,Co
F-NADPH,Ca,
tBPH
ALTERS
PROSTAGLANDIN
SYNTHESIS
Oxidative stress
& INCRENO
DEGRADATION
ENDOTHELIAL
DYSFUNCTION
VASCULAR TONE
no
DIABETES

70.  ENDOTHELIUM & CKD

71. ENDOTHELIUM &SEPSIS

72. vonWillebrand disease
 VWFrequired for interaction & adhesion of platelets
to ECM
 Genetic absenceof this factor( AD,rareAR)→von
Willebrand disease

74. PHYSIOLOGICALANGIOGENESIS

75. TUMOR ANGIOGENESIS

76.  In disease, ECgrowth 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 in to tumor
-Formation of new capillaries
 Tumor vessels are
-tortuous
-dilated, uneven diameter
-excessive branching &shunting
-lack perivascular cells

77. ANTIANGIOGENICTHERAPY
 Acquired drug résistance of tumor – due to highintrinsic
mutation rate -- major causeof treatmentfailure
 But ECs are genetically stable ; ECsapoptosispathway
is intact
 ECprovides nourishment to many tumor cells;tumor
growth dependent on angiogenesis
 blockade of asingle GF(e.g. VEGF)may inhibit tumor
induced vascular growth

79. vonWillebrand disease
 VWFrequired for interaction & adhesion of platelets
to ECM
 Genetic absenceof this factor( AD,rareAR)→von
Willebrand disease

80. TheWHOclassification of vasculartumors
Benign-
1) Hemangiomas
-sub cut/deep
-capillary
-cavernous
-arteriovenous
-Venous
-intramuscular
-synovial
2) Epitheloid Hemangiomas
3) Angiomatosis
4) Lymphangioma
TUMOROFENDOTHELIALCELLS

81. 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

82.  EC’splay avital role in health and integrity of every
tissue of the bodybecauseapart from cartilage,
every cell lies within afewµm of acapillary.
 Thediffusion limit of oxygen in tissue is only ≈
100µm,and cannot crossblood vesselthicker than that
 fine capillaries ( 10-15 µm ) & consist merely of
endothelial cells and avery fine basal lamina, thus helps
in providing oxygen, nutrients & metabolites.
Summary

83.  Adjust their number & arrangement to accommodate
local requirement
 Thus,they are life-support tissue extending & remodeling
the network of blood vesselsto enable tissue growth,
 & repair.
 Dysfunction of EC hasbeen implicated in virtually
every type vascular disease(Atherosclerosis,HTN,DM
etc.)
 And hence integrity & proper function of ECellsis
essential for proper organ function and goodhealth.

84.  Pathological BasisOf Disease : Robbins & 9 Th Edition.
 Harrison’s Principles Of Internal Medicine: 19th Edition
 WHOclassification: tumors of soft tissue andbone
 Hematology : BasicPrinciples & Practise,5th e(Hoffman)
 Hemostasis and Thrombosis –Basic Principles & Practice, 5th e(
Colman , Goldhaber )
 Internet sites
References

85. THANK YOU ALL.