6. stem cells+regeneration dr ashutosh kumar
TRANSCRIPT
Q No 1
A 22-year-old woman nursing her newborn develops a tender erythematous area around the nipple of her left breast. A thick, yellow fluid is observed to drain from an open fissure. Examination of this breast fluid under the light microscope will most likely reveal an abundance of which of the following inflammatory cells?
(A) B lymphocytes
(B) Eosinophils
(C) Mast cells
(D) Neutrophils
(E) Plasma cells
Acute mastitis
Q No:2/5
A 5-year-old boy punctures his thumb with a rusty nail. Four hours later, the thumb appears red and swollen. Initial swelling of the boy’s thumb is primarily due to which of the following mechanisms?
(A) Decreased intravascular hydrostatic pressure
(B) Decreased intravascular oncotic pressure
(C) Increased capillary permeability
(D) Increased intravascular oncotic pressure
(E) Vasoconstriction of arterioles
Infl edema
Q No 3/9
A 36-year-old woman with pneumococcal pneumonia develops a right pleural effusion. The pleural fl uid displays a high specific gravity and contains large numbers of polymorphonuclear(PMN) leukocytes. Which of the following best characterizes this pleural effusion?
(A) Fibrinous exudate
(B) Lymphedema
(C) Purulent exudate
(D) Serosanguineous exudate
(E) Transudate
Diagnosis: Bacterial pneumonia, pleural effusion
Q No 4/11
A 10-year-old boy with a history of recurrent bacterial infections presents with fever and a productive cough. Biochemical analysis of his neutrophils demonstrates that he has an impaired ability to generate reactive oxygen species. This patient most likely has inherited mutations in the gene that encodes which of the following proteins?
(A) Catalase
(B) Cytochrome P450
(C) Myeloperoxidase
(D) NADPH oxidase
(E) Superoxide dismutase
Ans: D
Diagnosis: Chronic granulomatous disease
Q No 5/14
A 41-year-old woman complains of excessive menstrual bleeding and pelvic pain of 4 months. She uses an intrauterine device for contraception. Endometrial biopsy reveals an excess of plasma cells and macrophages within the stroma. The presence of these cells and scattered lymphoid follicles within the endometrial stroma is evidence of which of the following conditions?
(A) Acute inflammation
(B) Chronic inflammation
(C) Granulation tissue
(D) Granulomatous inflammation
(E) Menstruation
Diagnosis: Chronic endometritis
Q No. 6
Regeneration, repair and
wound healing
Regeneration:When healing takes place by
proliferation of parenchymal cells of same type.
Repair:When healing takes place by proliferation of
connective tissue elements resulting in FIBROSIS or
SCARRING.
Regeneration
requires intact extracellular matrix framework
In mammals : compensatory growth (hypertrophy and
hyperplasia) rather than true regeneration (eg. growth
after partial hepatectomy and nephrectomy)
Continuously cycling cells ( bone marrow, epithelium of
skin and GI mucosal epithelium) regenerate if stem
cells are intact
Cell types ( based on their proliferative
capacity) 1.
Labile cells ( continuously dividing cells)
Surface epithelia: skin, oral cavity, vagina, cervix
Excretory duct epithelia: saliv.glands, pancreas, biliary tract
Columnar epithelia: GI, uterus
Transitional epith: urinary tract
Bone marrow cells and hematopoietic cells
Derived from pleuripotent stem cells….
Cell types ( based on their proliferative
capacity) 2.
Stable cells ( quiescent cells)
They don’t but can enter G1
Liver, kidney, pancreas ( acini)
Fibroblasts, smooth muscle, endothelium,
lymphocytes etc.
Cell types ( based on their proliferative
capacity) 3.
Permanent cells ( nondividing cells)
Can’t enter the cell cycle
Neurons(?) ( neural precursor cells!)
Skeletal muscle(?) ( satellite cells!)
Myocardium
Stem cells
Prolonged self-renewal capacity and asymmetric replication
Embryonic stem cells, adult stem cells (bone marrow SC, tissue SC)
REGENERATIVE MEDICINE ( therapeutic cloning !)
New observations: Stem cells in the brain
Bone marrow stem cells – multiple developmental option (developmental plasticity)
Some tissue stem cells – similar to embryonic stem cells
Niches Eg. Base of colon crypts, hair follicle bulges, oval cells (liver
stem cells) in canals of Hering
Stem cells
self-renewal properties
capacity to generate differentiated cell lineages.
stem cells need to be maintained during the life of
the organism.
achieved by two mechanisms:
(a) obligatory asymmetric replication: one of the
daughter cells retains its self-renewing capacity…
(b) stochastic differentiation: 50- 50.. Depending on
luck factor…
Embryonic Stem Cells: uses
• To study the specific signals and differentiation
steps required for the development of many
tissues.
• To study various disease models with help of
knockout mice or “knock-in” mice.
• ES cells may in the future be used to repopulate
damaged organs.
Reprogramming of Differentiated Cells: iPS Cells
Differentiated cells of adult tissues can be reprogrammed
to become pluripotent by transferring their nucleus to an
enucleated oocyte.
oocytes implanted into a surrogate mother
Develop embryo and ultimately cloned animal
This technique is K/A reproductive cloning(dolly).
Similar is therepeutic cloning… but ethical issues…
Bone marrow stem cells
Hematopoietic stem cells
Stromal cells: have potentially important therapeutic
applications.
Multipotent adult progenitor cells
( adult counterpart of embryonic stem cells)
Tissue stem cells 1.
Liver - Oval cells
Niche: canals of Hering
Bipotential progenitors (→ hepatocytes and biliary cells)
Activated when hepatocyte proliferation is blocked (eg.
carcinogenesis, cirrhosis, fulminant hepatic failure)
Brain- Neural stem ( precursor) cells
Niche: the subventricular zone (SVZ) & dentate gyrus of
hyppocampus
Neurogenesis ?
Being studied for degenerative neural disorder…
Tissue stem cells
Skin:
located in the hair follicle bulge, interfollicular areas of the
surface epidermis, and sebaceous glands.
Skeletal muscle- satellite cells
Niche: beneath basal lamina
Diff. toward myocytes, adipocytes, osteocytes
Intestinal epithelium:
located immediately above Paneth cells in the small intestine,
or at the base of the crypt, as is the case in the colon\
Cornea: limbal scleral cells…
Growth factors
Bind to specific receptors
Initiate cell proliferation
Act on contractility, differentiation, locomotion,
angiogenesis etc.
Growth factors
EGF, TGFα
Mitogenic for epithelial cells, fibroblasts, hepatocytes
Bind EGFR→therapeutic target ( ERB B1 and ERB B2 or HER-2/neu)
Hepatocyte Growth Factor (HGF)
Vascular Endothelial Growth Factor (VEGF)
Vasculogenesis, angiogenesis
Platelet-Derived Growth Factor (PDGF)
Migration and proliferation of fibroblasts, smooth muscle cells
Activation of oval cells
Growth factors 3.
Fibroblast Growth Factor (FGF)
Angiogenesis, wound healing, hematopoiesis, development of
skeletal muscle etc.
TGF-β
Growth inhibitor for epithelial cells and leukocytes ( blocks the
cell cycle)
Stimulates the proliferation of fibroblasts and smooth muscle
cells, fibroblast chemotaxis, production of collagen, fibronectin
etc.→ FIBROSIS
Anti-inflammatory effect
SIGNALING MECHANISMS IN CELL GROWTH
Signal Transduction Pathways
Signaling from tyrosine kinase receptors
ECM
Networks of macromolecules outside the cell
Networks: Interstitial matrix and BM
Macromolecules:
1. Fibrous structural proteins ( collagens, elastin, fibrillin,
elastic fibres)
2. Proteoglycans and hyaluronic acid
3. Cell adhesion molecules ( integrins, selectins, cadherins,
osteonectin, tenascin etc.)
Extracellular matrix
Mechanisms by which ECM components and growth factors interact and activate
signaling pathways.
REPAIR
Replacemnt of injured tissue by fibrous tissue
includes the following basic features:
• inflammation
• angiogenesis,
• migration and proliferation of fibroblasts,
• scar formation
• connective tissue remodeling.
TWO PROCESS:
(A) GRANULATION TISSUE FORMATION
(B) CONTRACTION OF WOUND
The relative contributions of repair
and regeneration are influenced by:
(1) the proliferative capacity of the cells of
the tissue;
(2) the integrity of the extracellular matrix;
and
(3) the resolution or chronicity of the injury
and inflammation.
Granulation tissue
Hallmark of healing
~ term from macroscopy ( granular, pinkish)
Microscopy: angiogenesis ( new vessels leaky→ edema),
fibroblasts, macrophages, (ly, mast cells, eosinophils)
GRANULATION TISSUE
FORMATION
THREE PHASES
(A) phase of inflammation
(B) phase of clearance
(C) phase of ingrowth of granulation
PHASE OF INFLAMMATION
FOLLOWING TRAUMA BLOOD CLOT AT SITE OF
INJURY
ACUTE INFLAMMATORY RESPONSE WITH
EXUDATION OF PLASMA
INFILTRATION OF NEUTROPHIL AND SOME
MONOCYTE WITH 24 HOURS
PHASE OF CLEARANCE
PROTEOLYTIC ENZYME FROM NEUTROPHIL
AUTOLYTIC ENZYMES FROM DEAD TISSUE CELLS
PHAGOCYTIC ACTIVITY OF MACROPHASE
CLEAR OFF NECROTIC TISSUE DEBRIS & RBC.
PHASE OF INGROWTH OF
GRANULATION
TWO PROCESSES
(1.) Neovascularisation
(2.) Fibrogenesis
GRANULATION
TISSUE
Granulation tissue
GRANULATION TISSUE
FIBROBLAST
NUCLEI
BLOOD
VESSELS
NEOVASCULARISATION
Formation Of New Blood Vesseles
Proliferaton Of Endothelial Cells From Margins Of Severed Blood Vesseles
Under Influences Of
VEGF
PDGF
TGF – β
B FGF
Angiogenesis from Preexisting Vessels
• Vasodilation: in response to nitric oxide, and VEGF
• Proteolytic degradation of the basement membrane:by MMPs
• Migration of endothelial cells toward the angiogenic stimulus
• Proliferation of endothelial cells, just behind the leading front of migrating cells
• Maturation of endothelial cells,
• Recruitment of periendothelial cells (pericytes and vascular smooth muscle cells) to form the mature vessel
ANGIOGENESIS
FIBROGENESIS
COLLGEN FIBRILS BEGINS TO APEAR BY 6TH DAYS
AS MATURATION PROCEEDS MORE AND MORE COLLAGEN FORMED WHILE THE NO. OF FIBROBLAST & NEW BLOOD VESSELES DECREASE.
THIS RESULT FORMATION OF INACTIVE LOOKING SCAR CALLED AS CICATRISATION.
SCAR
FIBROBLAST NUCLEI
CONTRACTION OF WOUND
START AFTER -2-3 DAY
COMPLETED UP TO 14TH DAY
MECHANISM INVOLVES
(1.) DEHYDRATION – REMOVAL OF FLUID BY DRYING OF WOUND
(2.) CONTRACTION OF COLLAGEN
(3.) DISCOVERY OF MYOFIBROBLAST
CONTRACTION
W
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D
H
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A
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Healing by first intention
Healing by second intention
FACTORS INFLUENCING WOUND HEALING
•LOCAL Type, size, location surgical, blunt trauma
Blood supply face, leg
Infection delay, deforming scars
Irradiation inhibition of cell division
FACTORS INFLUENCING WOUND HEALING
SYSTEMIC
Age cardiovascular status
Metabolic diabetes infections, blood supply
status scurvy inhibition of collagen synthesis
Hormones cortisons, steroid, inhibition of collagen synthesis thyroid estrogens indirect actions androgens
Complications of wound healing
1. Deficient scar formation ( wound dehiscence,
ulceration)
2. Excessive formation of repair components (
hypertrophic scar, keloid, exuberant granulation,
desmoid or aggressive fibromatosis)
3. Contracture
Keloid
Healing of bone fractures