Epi-mes :cell-cell interactions

Question 1

what plays an important role in defining the site specific nature of cell differentiation snd proliferation?

Answer 1

Interactions between Epithelial cells and connective tissue (mesenchyme) cells (fibroblasts) in the oral mucosa

Question 2

what are these interactions?

Answer 2

both dynamic and reciprocal

Question 3

what is connective tissue?

Answer 3

-Structural portions of body
-Hold the cells of the body together
-Framework or matrix for the body.
-Structural molecules collagen and elastin
(few cells, lots of matrix)

Question 4

what is the mesenchyme?

Answer 4

• Mesodermal origin
• loosely packed
• unspecialized cells
• gelatinous ground substance from which connective tissue, bone cartilage and the circulatory and lymphatic systems develop

Question 5

what differentiates in tooth to make enamel?

Answer 5

epithelium

Question 6

what are the 4 fundamental aspects of developmental biology?

Answer 6

• Proliferation/Growth-size : how cells divide
• Pattern formation: is the process by which cells in a developing embryo acquire identities that lead to a well ordered spatial pattern of cell activities.
• Morphogenesis-shape
• Differentiation-type

Question 7

what is sequentially?

Answer 7

timing of events

Question 8

what is dynamic?

Answer 8

happens quickly

Question 9

what is reciprocal?

Answer 9

one in control then the other

Question 10

what are the 2 general types of phenomena in tissue interactions?

Answer 10

• instructive

- permissive

Question 11

Describe instructive.

Answer 11

the ability of one tissue to determine specific patterns of morphogenesis and differentiation that will develop in an associated tissue

Question 12

Describe permissive (or facilitative).

Answer 12

the ability of an interacting tissue to provide certain conditions that is necessary for its committed partner tissue to progress to full expression of its pre-determined phenotype

Question 13

what are the 4 types of interactions used in experimental work?

Answer 13

• Homotypic: same time, place and species.
• Heterotypic: unrelated usually same time and species.
• Heterochronic: same type and species but different time.
• Heterospecific: similar areas but different species

Question 14

Describe organogenesis.

Answer 14

• Secondary inductions
• Patterning-right place
• Organ rudiment- morphogenesis and proliferation
• Organ specific structures- differentiation

Question 15

Name the stages of development of organogenesis.

Answer 15

• epithelial placode
• Bud
• morphogenesis
• adult organ (tooth)

Question 16

where do first signals directing organogenesis come from?

Answer 16

mesenchyme

Question 17

Name some experiments in cell-cell interactions.

Answer 17

• Early work on tissue recombination
• Organ culture using filters
• Organ culture using Trowell dish
• Bead implantation
• In situ hybridisation

Question 18

what happens in tooth development (mouse)?

Answer 18

day 9/10-initation
day 12- bud
day 14- cap
day 16-bell

Question 19

what is differentiation of cell types during tooth development?

Answer 19

• cells become more specialised
• Amorphous blobs-
• Various stages to get to final structures.
• These are dynamic, reciprocal and sequential in nature

Question 20

During differentiation of cell types, what interacts to initiate signal?

Answer 20

mesenchyme and epithelium

Question 21

What are cytokines and what happens during development?

Answer 21

• Small molecules transmitted over small distances.
• Drive all processes of tooth development at least 30 known in tooth development.
• Receptors and signalling.
• RNA synthesis of other cytokines and ECM molecules

Question 22

What is the Extracellular matrix and what happens in development?

Answer 22

• Important in morphogenesis and differentiation.
• Adhesion, migration, proliferation, polarisation and differentiation.
• Expression of type I, III, IV collagens, laminin, various proteoglycans- basement membrane of developing tooth
• Changes in fibronectin, tenascin, type I and type III collagen and syndecan.
• Changes in integrin expression especially alpha v beta 5.
• Need intact basement membrane for differentiation of mesenchyme to odontoblast

Question 23

Describe the stages in oral development.

Answer 23

• Interaction between oral ectoderm and mesoderm.
• Lots of epithelial mesenchymal interactions in development; salivary glands, palate formation, tongue and tooth development.
• In normal homeostasis these interactions continue in the adult

Question 24

what happens if you take out TGF B-3 in mice?

Answer 24

Growth factor is taken out so gene is not expressed and palatal shelfs haven’t fused so mouse develops cleft palate