Lecture 6: tissue renewal

Question 1

Parenchymal cells

Answer 1

-functional cells of organ
-hepatocytes, myocytes

Question 2

stromal cells

Answer 2

-supporting structure of organs
-ECM, blood vessels, connective tissue

Question 3

Tissue regeneration

Answer 3

-replacement of injured tissue with cells of same type and function

Question 4

tissue repair

Answer 4

-when damage cannot be reverse by regenration alone

Question 5

Responses to Tissue INjury

Answer 5

-regeneration
-repair
-fibrosis

Question 6

Stages of healing

Answer 6

1. hemostasis
2. inflammation
3. proliferation
4. remodeling

Question 7

hemostasis

Answer 7

-minutes after injury
-local vasoconstriction
-activation of platelets and clotting factors to form fibrin clot
-creates scaffold for migrating cells

Question 8

Inflammation

Answer 8

-hours
-drived by platelet-derived mediators, bacteria, and chemoattractants

Question 9

Proliferation

Answer 9

-days
-mediated by macrophage and fibroblast-derived growth factors

Question 10

Remodeling

Answer 10

-weeks to months
-transition from type III to type I collagen
-restore tensile strength of tissue

Question 11

Determinants of Regeneration vs Repair

Answer 11

-nature of cells injured
-extent of injury
-any inflammation?
-underlying disease (diabetes)

Question 12

Primary intention

Answer 12

-wound closed with surgical intervention
-edges brought together
-best for clean wounds in vascularized areas

Question 13

secondary intention

Answer 13

-wound open
-left to heal randomly
-good for contaminated wounds
-increased scarring

Question 14

tertiary intention

Answer 14

-delayed primary closure
-good for initially infected wounds

Question 15

Cell proliferation

Answer 15

-driven by growth factors
-ability of cell to divide

Question 16

Cell numbers can be changed by:

Answer 16

-stem cell input rates
-apoptosis
-changes in rates of proliferation or differentiation

Question 17

Epidermal Growth Factor (EGF)

Answer 17

-from activated macrophages, keratinocytes
-stimulates keratinocyte migration and granuloma formation

Question 18

Common outcome of various signal transduction pathways of growth factors

Answer 18

change in gene expression

Question 19

Extracellular Matric (ECM)

Answer 19

-basement membrane
-intersitial matrix

Question 20

ECM and structural integrity

Answer 20

-related to tissue shape
-tissue specific mechanical properties
-facilitates tissue organization

Question 21

ECM dynamics

Answer 21

-ECM is a growth factor depot for other signaling molecules

Question 22

Cell-matric interactions

Answer 22

-ECM anchors cells via interactions with integrins
-related to adhesion and cell spreading
-faciliatates cell polarity and migration

Question 23

ECM signals vs cell response

Answer 23

-signals for homeostasis, proliferation, differentiation

Question 24

Basement membrane

Answer 24

-type IV collagen
-laminin
-proteoglycan

Question 25

intersitial matrix

Answer 25

-fibrillar collagens
-elastin
-proteoglycan and hyaluronan

Question 26

Fibrosis (scarring)

Answer 26

-severe damaged cells replaced with fibroblast
-repair begins within 24 hours

Question 27

Fibrosis mechanism

Answer 27

-angiogenesis
-migration and proliferation of fibroblasts
-deposition of ECM by fibroblasts
-maturation and remodeling done by macrophages

Question 28

Growth factors that regulate fibrosis

Answer 28

-produced by endothelial cells and by inflammatory cells esp macrophages
-PDGF
-TGFB
-FGF-2

Question 29

PDGF (platelet-derived growth factor)

Answer 29

-migration and proliferation of fibroblasts, smooth muscle cells, and macrophages

Question 30

TGFB (transforming growth factor)

Answer 30

-potent fibrinogenic factor that stimulates collagen, fibronectin, and proteoglycan synthesis
-inhibits collagen degradation
-inhibits lymphocyte proliferation
-anti-inflammatory

Question 31

Disease and fibrosis

Answer 31

-many diseases associated with fibrosis
-fibrosis regulation are targets for treatment