Extracellular Matrix (ECM)

Which of the following is a SIBLING glycoprotein? a. Osteopontin b. Osteonectin c. Osteocalcin

A, OPN : inhibitor

Characteristic of Osteocalcin/Bone Gla Protein Except: a. decreased in metabolic bone disease w/ increased bone or osteoid formation b. involved in mineralization c. found in bone and dentin d. peptide hormone - glucose homeostasis

A. increased in metabolic bone diseases w/ increased bone or osteoid formation

What is the most abundant SIBLING protein of bone?

Bone sialoprotein (BSP)

What are the 2 main ways ECM is organized?

1. Basement Membrane/Basal Lamina 2. Interstitial ECM (IECM)/ Connective Tissue

What are the 3 steps to Formation of Mineralized ECM?

1. Production of organic ECM 2. Maturation of ECM 3. Mineralization of ECM

What are the 3 major groups of ECM macromolecules?

1. Structural proteins (collagens, elastin) 2. Protein-polysaccharide complexes (imbed structural proteins and have regulatory functions 3. Adhesive glycoproteins to attach cells to ECM (fibronectin, laminins)

All of the following are main fibrous ECM proteins EXCEPT: a. Integrins b. Collagens c. Laminins d. Elastins

A

(T/F) Osteonectin/SPARC is found in all of the following except: a. bone b. enamel c. dentin d. PDL

B, only found in tissues with high collagen turnover

Major ECM-degrading enzymes include all of the following except: a. MMPs b. collagenase c. ADAMTS d. Heparanase

B.

All of the following describe the Basal Lamina EXCEPT: a. thin (50-100) b. sheet-like particles c. pericellular matrix ( in close contact w/ cells) d. specialized for cell attachment to ECM e. allows for easy cell migration f. underlies epithelial and endothelial cells

E, barrier to cell migration

(T/F) Matric Gla Protein (MGP) increases mineralization and allows vascular calcification

False, MGP is a potent inhibitor of mineralization and prevents vascular calcification

(T/F) laminins are homotrimeric glycoproteins

False, heterotrimeric, composed of alpha, beta, and gamma chains

(T/F) Basal Lamina constitutes most of the extracellular mass in the majority of tissues

False, interstitial ECM

(T/F) Ground substance is rich in hyaluronic acid and glycosamino glycans

False, rich in hyaluronic acid and proteoglycans

(T/F) Integrins are unidirectional signal transmitters

False, they are bidirectional transmitting information from ECM to cells and intracellular stimuli can also activate integrins

(T/F) The first 4 types of classical OI are caused by production of abnormal collagen type 1

False, type 1 is caused by decreased production of collagen type 1 the remaining 3 are caused by production of abnormal collagen type 1

Which Fibrous ECM Protein has been termed the "master organizer"?

Fibronectin forms a bridge between cell surface receptors and ECM molecules plays essential role in assembly of fibrillin into structural network (microfibrils)

What are the non-fibrillar components of ECM?

GAGS proteoglycans glycoproteins

Which forms of osteogenesis imperfecta have defective dentin (dentinogenesis imperfecta type 1)

I-IV (classical forms)

TGF-Beta complex consists of what? And is connected via what type of bond?

TGF-beta latency associated protein (LAP) latent TGF-B-binding protein (LTBP) LTBP1 connects to fibrocectin fibers and fibrillin microfibrils disulfide

(T/F) The Basement membrane is highly cross-linked

True

(T/F) The function of connective tissue is determined by the physical properties of its extracellular matrix

True

(T/F) the ECM acts as a reservoir for various GFs, cytokines, and chemokines secreted from the cell

True

(T/F) Integrins, Dystroglycan, Discoidin domain receptor are all cell adhesion receptors

True Dystroglycan: receptor for several BM proteins like laminin, perlecan, agrin DDR1 and DDR2: receptors for native forms of collagen

What is the most predominant collagen type in the Basal Lamina?

collagen type IV

Where are Hydroxyapatite crystals initially deposited?

discrete sites in collagen fibrils (nucleation sites)

PDL is made up of which type of collagen?

fibril associated collagen type XII typical of CTs withstanding high tensile stress

What are the main components of Microfibrils?

fibrillin elastin fibulin (like fibula *swoon*)

What is Ehlers-Danlos Syndrome?

mutations in collagen-coding genes early-onset periodontitis hypermobility of TMJ fragility of oral mucosa and gingiva

What is Marfan Syndrome?

over activation of TGF beta signaling mutations in fibrillin 1 and 2 genes causes long arms, hypermobility of joins, aortic enlargement, problems w/ eyes narrow jaws and high arched palate

How does Oral Squamous Cell Carcinoma Invade?

produces matrix metalloproteases (MMPs) which degrade ECM proteolytic remodeling of the ECM facilitates cancer cell invasion

How is TGF-B activated?

proteases or other factors will degrade LAP which will release TGF-B from the complex and allow it to bind to its receptors

What are the 3 major groups of Non collagenous proteins that regulate mineralization?

proteoglycans glycoproteins Gla proteins (gamma-carboxyglutamic acid- containing proteins)

(T/F) Enhanced production of and deposition of ECM components can sometimes be harmful and cause fibrosis

true

(T/F) One of the BMs main functions is to regulate cell differentiation and function by interaction of cell surface receptors and molecules in ECM

true

(T/F) Osteonectin is important for tooth position within the alveolar bone and for absorbing forces generated by chewing

true

(T/F) Pyrophosphate is an inhibitor of mineralization

true

(T/F) The basement membrane is the first and most robust structural barrier to invasion of tumor cells

true

(T/F): Integrins are transmembrane proteins formed of heterodimers of alpha and beta subunits

true

All of the following are characteristic of Loose connective Tissue except: a. large amount of ground substance b. important in facilitating intercellular exchange c. Low elasticity and strength

C. moderate amounts of elasticity and strength in tissue and organs (irregular network of elastin fibers and collagen fibers)

What are the 3 main functions of the Basement Membrane?

Cell adhesion Diffusion for macromolecules Regulation of Cell differentiation and function