Mineralization Mechanisms 2 and 3 Flashcards Preview

Biomedical Sciences Core > Mineralization Mechanisms 2 and 3 > Flashcards

Flashcards in Mineralization Mechanisms 2 and 3 Deck (64)
Loading flashcards...
1

Players in Osteogenesis

• Osteo___

• Osteo___

• Osteo___ 

• Osteoprogenitor cells come from the____  and are induced into becoming ____ and ____ cell.

• They will have all of the hallmarks of secretory cell (___ Golgi, __ ER, nucleus is___)

• Osteoblasts eventually get ___ into the ____ of bone and they become ____

• They become centralized and stuck in ___ ___  and form____l bone which is ___y and ___

• Initially you have ____ bone.

Woven bone is____

First bone that is laid down and its ___ ___ ___.

• Placing Implant: 1st 2 weeks you are dealing with woven bone so don’t go placing implant bc it will __ ___ __

o Have to go thru ____  to get more ___ bone called corticoid bone • This is very orderly

Players in Osteogenesis • Osteoblast • Osteoprogenitor • Osteoid • Osteoprogenitor cells come from the mesenchyme and are induced into becoming osteoblast and secretory cell. • They will have all of the hallmarks of secretory cell (big Golgi, big ER, nucleus is acentric) • Osteoblasts eventually get incorporated into the matrix of bone and they become osteoids • They become centralized and stuck in Haversion canals and form critical bone which is orderly and strong • Initially you have woven bone. Woven bone is irregular. First bone that is laid down and its not very strong. • Placing Implant: 1st 2 weeks you are dealing with woven bone so don’t go placing implant bc it will just come out o Have to go thru remodeling to get more orderly bone called corticoid bone • This is very orderly

2

Osteogenesis

• Two processes occur in bone:

o ___ ___ mineralization • Type I is major type

o ___ ___ ____ mineralization

Osteogenesis • Two processes occur in bone: o Collagen-based mineralization • Type I is major type o Matrix -vesicle mediated mineralization

3

Collagen-based Mineralization in Bone:

Build the ____

• Found in ____ bone and _____ dentin

Collagen of mineralized tissues is different than other collagen

• Little to no type ___

 • Increased____-____  o This helps with the ____ g and makes it strong

• High amt. of___ ____ bc of OH-K

• Intermolecular space ____ o How the fibers pack together o Type I has a lot more space in bw o What goes in those spaces? • ____

Collagen-based Mineralization in Bone: Build the scaffold • Found in Lamellar bone and circumpulpal dentin Collagen of mineralized tissues is different than other collagen • Little to no type III • Increased OH-lysine o This helps with the crosslinking and makes it strong • High amt. of cross-linking bc of OH-K • Intermolecular space greater o How the fibers pack together o Type I has a lot more space in bw o What goes in those spaces? • HAP

4

Triple Helix→ Collagen

Collagen ___

 Collagen____

From collagen molecules to higher order structures = bone

Collagen ____

 Mineralized ___

___

___

___

____

Triple Helix→ Collagen Collagen Fibril Collagen Fiber From collagen molecules to higher order structures = bone Collagen Molecule Mineralized Fibril Fiber Bundle Lamella Osteon

5

• Mineralization initiated within __ ___ in the collagen ____

o Helix is very ___ and fibrils pack in orderly fashion

o If you packing something and everything around it is orderly, it also has to be ____

• Early stage mineralization (on left) o Begins in ___ (using ___ ___ ___)

• Later stage mineralization o Grows as ___ in ___ dimensions • Doesn’t have anywhere else to grow

•____  acts as a scaffold and shows it the only places it can go

• Will get orderly structure of HAP bc of collagen base

• Mineralization initiated within hole zones in the collagen fibrils o Helix is very orderly and fibrils pack in orderly fashion o If you packing something and everything around it is orderly, it also has to be orderly. • Early stage mineralization (on left) o Begins in gaps (using Matrix vesicle mediated) • Later stage mineralization o Grows as plates in all dimensions • Doesn’t have anywhere else to grow • Collagen acts as a scaffold and shows it the only places it can go • Will get orderly structure of HAP bc of collagen base

6

Gather the ingredients

• ____ solution of calcium and phosphate o Need high enough conc for mineralization to occur. o Don’t want so high of conc that mineralization with spontaneously occur (without nucleator) o We have metastable saturation of Ca and PO4

• ____ to seed the first crystal growth

•___ ___s to___ the components together

Gather the ingredients • Supersaturated solution of calcium and phosphate o Need high enough conc for mineralization to occur. o Don’t want so high of conc that mineralization with spontaneously occur (without nucleator) o We have metastable saturation of Ca and PO4 • Nucleator to seed the first crystal growth • Bridging molecules to connect the components together

7

Matrix vesicle-mediated mineralization

• Found in endochondral cartilage, ___ __, ___ __, and most types of pathologic mineralization •

This forms our “drop”→ ____

• This takes place in that little hole (gaps) where mineralization is initiated •

This type of mineralization occurs in areas that we have very ___y, very ___ mineralization.

• Not very____, just going to occur very ___.

o Orderliness occurs as bone continues to grow

Matrix vesicle-mediated mineralization • Found in endochondral cartilage, mantle dentin, woven bone, and most types of pathologic mineralization • This forms our “drop”→ nucleator • This takes place in that little hole (gaps) where mineralization is initiated • This type of mineralization occurs in areas that we have very early, very rapid mineralization. • Not very orderly, just going to occur very quickly. o Orderliness occurs as bone continues to grow

8

• Matrix vesicle mediated mineralization

o ____ cells __ ___ to form a ___ bound ____ ____structure

o Contain ___ ____ and ___ ____

o Function as ____ for __ ____

o Eventually____and released into the ___, in between the ___ ___, promoting further ____.

• Further biomineralization is regulated by other___ ____

• Matrix vesicle mediated mineralization o Blastic cells bleb off to form a membrane bound extracellular vesicular structure o Contain acidic phospholipids and alkaline phosphatase o Function as catalysts for apatite formation o Eventually degraded and released into the ECM, in between the collagen fibers, promoting further mineralization • Further biomineralization is regulated by other bone proteins

9

Blebbing off of matrix vesicles from cell

• We have matrix vesicles • These are not really cells, they are vesicles __ ___ our ____ • Like a cytoplasmic inclusion • It will take these off from the cell

Blebbing off of matrix vesicles from cell • We have matrix vesicles • These are not really cells, they are vesicles blebbed off our osteoblasts • Like a cytoplasmic inclusion • It will take these off from the cell

10

• Inside of them, there is __ ___

. • It is just a little ____

• Mineralization can occur easier if we have a contained unit • Contain Ca and PO4 in ___ ___ to increase levels of Ca and PO4 and isolate it into a small area.

• This is our defined space • We are going to increase our Ca and PO4 levels to ___ ___ metastable. It is quite supersaturated in this area so that when we initiate the mineralization, it will work

• On the outside we have____ ____(____→ __ + ___) • Phosphates are ___to come ___ the matrix

• Inside of them, there is no nucleus. • It is just a little container. • Mineralization can occur easier if we have a contained unit • Contain Ca and PO4 in one area to increase levels of Ca and PO4 and isolate it into a small area. • This is our defined space • We are going to increase our Ca and PO4 levels to higher than metastable. It is quite supersaturated in this area so that when we initiate the mineralization, it will work • On the outside we have Alkaline Phosphatase. (R-PO4→ ROH + PO4) • Phosphates are free to come into the matrix

11

• We have shut off ___ ___ so no ___is pumped ___

 • Ca allowed to come in but not allowed to leave

•___ [] of Ca and by ____alone, all the available ___ will com in as well

o Attraction to + Ca inside • So now we have a bunch of Ca and PO4 inside

• We have shut off ATP pump so no Ca is pumped out • Ca allowed to come in but not allowed to leave • Increase [] of Ca and by diffusion alone, all the available PO4 will com in as well o Attraction to + Ca inside • So now we have a bunch of Ca and PO4 inside

12

• Across here we have a nucleation site

o It is created by ___ and___ ___sites o This is in the membrane

o Acts as our _____

• Now we have Ca, PO4 and nucleator so it should ____ly start to mineralize within this vesicle o ____ mineralization within the vesicle, but its controlled by the fact that its in a ___

• Across here we have a nucleation site o It is created by annexin and phosphatidyl seine sites o This is in the membrane o Acts as our grain of sand • Now we have Ca, PO4 and nucleator so it should spontaneously start to mineralize within this vesicle o Uncontrolled mineralization within the vesicle, but its controlled by the fact that its in a membrane

13

• Eventually we have to get it ____ of the membrane

• The crystals are going to ____ as we go thru threr.

• Then membrane starts_____

 • Once the membrane degrades, this is a crystal that acts to ____ other areas of mineralization.

• If this is sitting in my little gap region, this will act as a nucleator for more mineralization to occur in that gap region

• Spindles of hydroxyapatite can be seen in degrading matrix vesicles. •

• Eventually we have to get it out of the membrane • The crystals are going to proliferate as we go thru threre. • Then membrane starts degrading • Once the membrane degrades, this is a crystal that acts to nucleate other areas of mineralization. • If this is sitting in my little gap region, this will act as a nucleator for more mineralization to occur in that gap region • Spindles of hydroxyapatite can be seen in degrading matrix vesicles. •

14

Degradation of the vesicle allows ____ of the crystal to a physiological _____ solution in the body.

Crystals are able to ____ to grow.

They will grow in ___ fashion bc they are trapped in ___ ____

Degradation of the vesicle allows exposure of the crystal to a physiological metastable solution in the body. Crystals are able to continue to grow. They will grow in orderly fashion bc they are trapped in collagen matrix

15

• You get these clumps • We call them _____

• As they grow they make ___ of mineralization • Eventually what happens is these will ____ together and form bigger ___ ____

• You get these clumps • We call them calcospherules • As they grow they make globules of mineralization • Eventually what happens is these will coalesce together and form bigger mineralization plates

16

• Later stage mineralization

o More ___ of ___

o It will be ___

o Grows as plates in __ ___s

o ___, ___ and ____ of crystal growth is determined by ___ ___ ___ found in the ___

ECM proteins ____ the ___ and ____ components

• We also have other molecules (not just collagen) that regulate growth)

• Later stage mineralization o More deposition of mineral o It will be orderly o Grows as plates in all dimensions o Direction, size and speed of crystal growth is determined by non-collagenous proteins found in the ECM • ECM proteins interconnect the mineral and organic components • We also have other molecules (not just collagen) that regulate growth)

17

Important ECM proteins

• Signaling o____, ____

• SIBLINGs o _____ ____, _____

•_____

Important ECM proteins • Signaling o Osteocalcin o Fibronectin • SIBLINGs o Bone Silaoprotein o Osteopontin • Byglycan

18

Additional Proteins of Interest

• ___ ___ __(DMP)

• ___ __ ___ (osteocalcin, BGP)

• ___ __ ___ (MGP)

• _____OPN)

• ___ __ ___ (BMP)

Additional Proteins of Interest • Dentin matrix protein (DMP) • Bone gla protein (osteocalcin, BGP) • Matrix gla protein (MGP) • Osteopontin (OPN) • Bone morphogenetic proteins (BMP)

19

SIBLINGs S___ i___-b___ l___ N-___ g___

• Found in ___ and ___ (___ and ___ found in higher amounts in ___)

  • o Dentin Sialoprotein, Dentin Matrix Protein

• ____: ___ ____ o ___ ___ ____ o They all have this sequence o Integrin binding o May be a signal for ___ to ___ ___

• Osteoclast

o Signals “Be here”

• Gene _____ are similar

• Genes are clustered on ____  ___q21-23 o All found in same area of the csome

• Similar ___ __ ___

SIBLINGs Small integrin-binding ligand N-linked glycoprotein • Found in bone and dentin (DSPP and DMP-1 found in higher amounts in dentin) o Dentin Sialoprotein, Dentin Matrix Protein • RGD cell attachment o Arginine Glycine Aspartic Acid o They all have this sequence o Integrin binding o May be a signal for cell to attach here • Osteoclast o Signals “Be here” • Gene organizations are similar • Genes are clustered on chromosome 4q21-23 o All found in same area of the csome • Similar post-translational modifications

20

What is the nucleator? • We don’t know but its believed to be ___ ____

• ___ ____ of • 75 kDa.

• Contains ___ sequence, attaches to ____ on bone cell similar to OPN.

• _____ mineral formation, but inhibits it at ___ ___

o You need something to tell it to stop o Feedback mechanism

• Found in high amounts in ___, ___, ____. (Mineralized tissue)

What is the nucleator? • We don’t know but its believed to be Bone Sialoprotein • Phosphorylated glycoprotein of • 75 kDa. • Contains RGD sequence, attaches to integrins on bone cell similar to OPN. • Initiates mineral formation, but inhibits it at higher concentrations. o You need something to tell it to stop o Feedback mechanism • Found in high amounts in bone, dentin, cementum. (Mineralized tissue)

21

Dentin Matrix Protein-1 (DMP-1)

• ___ ___ has never been isolated.

___ ___ have been isolated (37Kd and 57Kd) o Protein is degraded!

Overexpression of Dmp-1 induces ___ of ___ ___ to ___t-like cells and ___ ____

• Ectopic addition of DMP-1 seems to have __ ___ on mineralization o So its ___ a ____

. Not osteo___

 • Majority of information comes from in vivo studies

• Initially found in___ but found in ___ too!

Dentin Matrix Protein-1 (DMP-1) • Intact protein has never been isolated. Proteolytic fragments have been isolated (37Kd and 57Kd) o Protein is degraded! • Overexpression of Dmp-1 induces differentiation of mesenchymal cells to odontoblast-like cells and enhances mineralization • Ectopic addition of DMP-1 seems to have no effect on mineralization o So its not a nucleator. Not osteoinductive. • Majority of information comes from in vivo studies • Initially found in dentin but found in bone too!

22

DMP-1 null mice

•__ ____ molar teeth

• Decreased layer of____

• ___ pulp

• Must be important for deposition.

May have to do with ___ cell differentiation.

DMP-1 null mice • Poorly forming molar teeth • Decreased layer of dentin • Larger pulp • Must be important for deposition. May have to do with less cell differentiation.

23

Osteopontin

• Reduction of OPN allows ___ ___ healing and ____ the ___ ___

• Matrix molecule found in ___

• Seems to have to do with inflammatory response

• If you injure a cell, you should see ___level of OPN being produced

• If you reduce OPN, response becomes more ___. You will have ability to allow that to heal more ____

___-___ healing if you ___ amt of OPN

• OPN indicates that you need ___ formation and repair • You need lower levels of OPN if you want orderly tissue

Osteopontin • Reduction of OPN allows more organized healing and decreases the inflammatory response • Matrix molecule found in bone • Seems to have to do with inflammatory response • If you injure a cell, you should see higher level of OPN being produced • If you reduce OPN, response becomes more orderly. You will have ability to allow that to heal more smoothly • Scar-free healing if you decrease amt of OPN • OPN indicates that you need rapid formation and repair • You need lower levels of OPN if you want orderly tissue

24

Osteocalcin

• ___ ___ dependent ____ of three ___ ___ residues (___ carbon)

o Vit K dependent→ Think ____ o In coagulation Vit K triggers carboxylation. Its involved in gamma carboxylation

o Normally those carboxyl groups are not 100% carboxylated but with Vit K dependent ones they will carboxylate the gamma

• Gla residues are on __ ___ ___

• Carboxylation→ more ___charged o ___ ___. Gets Ca into an area • Attract calcium ions o By charge alone, PO4 will follow • Around this molecule we have ____ [ ] of Ca and PO4 in that area o Getting molecules in right spot

___ to ____ o Create ___ ____

• A form that is not gamma carboxylated and found in ___  may have some ___ ____ functions

Osteocalcin • Vitamin K dependent carboxylation of three glutamic acid residues (gamma carbon) o Vit K dependent→ Think coagulation o In coagulation Vit K triggers carboxylation. Its involved in gamma carboxylation o Normally those carboxyl groups are not 100% carboxylated but with Vit K dependent ones they will carboxylate the gamma • Gla residues are on one planar surface • Carboxylation→ more negatively charged o Chelates Ca. Gets Ca into an area • Attract calcium ions o By charge alone, PO4 will follow • Around this molecule we have supersaturated [ ] of Ca and PO4 in that area o Getting molecules in right spot • Attaches to hydroxyapatite o Create intramolecular bridges • A form that is not gamma carboxylated and found in serum may have some hormonal regulatory functions

25

MGP:

Matrix Gla Protein

• Gla→ indicates that its ___ ____

• MGP Null Mice: See ____

o It ___ ____ In aorta and blood cells

MGP: Matrix Gla Protein • Gla→ indicates that its gamma carboxylated • MGP Null Mice: See mineralization o It inhibits mineralization In aorta and blood cells

26

Bone Morphogenic Protein-2

• ___ occurring protein

o Produced by ____

 o Stored in __ ___

 • ____ o Induce new bone formation without autogenous bone or bone marrow • Stick it in muscle→ will get bone • Can force mesenchymal cells to differentiate and make bone

• Produced in ___ ___o Same ____ as native protein o ____ feasible product • Used in dentistry

Bone Morphogenic Protein-2 • Nataurally occurring protein o Produced by Osteoblasts o Stored in bone mineral • Osteoinductive o Induce new bone formation without autogenous bone or bone marrow • Stick it in muscle→ will get bone • Can force mesenchymal cells to differentiate and make bone • Produced in recombinant form o Same activity as native protein o Commercially feasible product • Used in dentistry

27

Osteogenesis Imperfecta

• Mutations in the COL1A1, COL1A2, CRTAP, and LEPRE1 genes cause osteogenesis imperfecta. o ____ genes o Genes important for__ ___ of collagen

• Mutations in the COL1A1 and COL1A2 genes are responsible for more than ___ percent of all cases of osteogenesis imperfecta.

• Characterized by ___ ___

• “__ ___ disease” o Their bones break a lot o Think its abuse at first

Osteogenesis Imperfecta • Mutations in the COL1A1, COL1A2, CRTAP, and LEPRE1 genes cause osteogenesis imperfecta. o Collagen genes o Genes important for cross linking of collagen • Mutations in the COL1A1 and COL1A2 genes are responsible for more than 90 percent of all cases of osteogenesis imperfecta. • Characterized by blue sclera • “Brittle Bone disease” o Their bones break a lot o Think its abuse at first

28

Summary

• Biomineralization of bone occurs in___ ___

• Calcium and phosphates are brought into the ___ and____within the space

• ___ ___ act as scaffolds, nucleators, and regulators of the mineralization process

• ___ ____ is deposited in and among the collagen fibers

• Crystal ___ and ___ is regulated by macromolecules in the ___

Summary • Biomineralization of bone occurs in defined spaces • Calcium and phosphates are brought into the space and held within the space • Organic macromolecules act as scaffolds, nucleators, and regulators of the mineralization process • Mineralized hydroxyapatite is deposited in and among the collagen fibers • Crystal size and shape is regulated by macromolecules in the matrix

29

Denting

Composition

Dentin similar to bone

A lot of ___ proteins and____water

Comparison of % contribution of each component with respect to weight vs. volume.

• Wet weight : higher %inorganic, higher % water and organic compared to volume

• Volume: ____% inorganic, ____% water and organic

Differences suggest that there is ___ ___ of ____ elements between the ____ components

• Don’t have that much ____  matter but you are packing tons of stuff very tighly in bw inorganic matter

DentingComposition Dentin similar to bone A lot of organic proteins and some water Comparison of % contribution of each component with respect to weight vs. volume.

• Wet weight : higher %inorganic, higher % water and organic compared to volume

• Volume: lower % inorganic, higher % water and organic Differences suggest that there is tight packing of inorganic elements between the organic components • Don’t have that much inorganic matter but you are packing tons of stuff very tighly in bw organic matter

30

Dentinogenesis

• Odontoblasts: ___ __ ___

o Forms __ ___

o Does this in ____  to enamel

• They form in opposite directions

• Osteoblasts have to move ____ from enamel to deposit the dentin

• It will put down a predentin,____  matrix, like bone • At some time later, this will ____

• Very orderly because the __ ___ from odontoblast stays ____

o Dentin is still ____ bc you have process going to the surface o Have to numb patient to work on dentin o Enamel you don’t bc its not a live tissue.

Dentinogenesis • Odontoblasts: Dentin forming cell o Forms Pre-Dentin o Does this in opposition to enamel • They form in opposite directions • Osteoblasts have to move away from enamel to deposit the dentin • It will put down a predentin, unmineralized matrix, like bone • At some time later, this will mineralize • Very orderly because the dentin process from odontoblast stays in tact o Dentin is still alive bc you have process going to the surface o Have to numb patient to work on dentin o Enamel you don’t bc its not a live tissue.