Lecture 19 - 20 Flashcards
What are the functions of bones?
Support
Protection
Leverage
Storage (calcium mainly)
Hematopoiesis
What are the 4 types of bones?
Long Bones
Irregular Bones
Flat Bones
Short Bones
What percentage of bone is inorganic and what are the top components (3)?
67%
Top inorganic components are calcium, phosphate, carbonate
What percentage of bone is organic and what are the top components?
33%
Collagen Type-1 and Proteoglycans
Osteon
fundamental functional unit of bone consisting of concentric layers of lamelle
Lamellae
concentric layers of compact bone
Osteocytes
mature cells - pass nutrients and gasses through canaliculi
Canaliculi
microscopic canals where osteocytes pass gasses
Lacunae
cavity/pits that hold osteocytes
Red bone marrow
site of blood production known as hematopoiesis
Yellow bone marow
stored fat
Osteoprogenitors
stem-cell like
Osteoclasts
breakdown bone
Osteoblasts
build bone; secrete osteoid
Osteoid
immature unmineralized gel-like component of bone; but will become mineralized
Intramembranous Osssification
mostly for flat bones; stem cells differentiate into osteoblasts; no cartilage precursor
Endochondral Ossification
mostly for long, short, and irregular bones; stem cells differentiate into chondroblasts (which lay hyaline cartilage) that die and form a cavity where osteoprogenitor cells invade the cavities and deposit osteoid
Ossification
bone formation
Adult Bone Remodeling Reasons
- adjust bone architecture to meet changing mechanical needs
- to repair microdamage and prevent accumulation of old bone
- to maintain plasma calcium homeostasis
autografts
patient; requires additional surgery for bone harvesting (high cost)
allografts
other patients; b/c of donor shortages but risk of immune rejections
xenografts
animal derived; immune rejections
What are 2 common metals for bone engineering?
stainless steel and titanium
What are 2 common ceramics for bone engineering?
HA (hydroxyapatite)
B (beta)-TCP
What are the 3 porous ceramic scaffold fabrication techniques?
polymer sponge
gel-casting
gel-polymer method
Polymer Sponge method
ceramic slurry + polymer sponge > organic burn out and sintering yields scaffold
Result: controllable microstructure, low mechanical strength
Gel-casting
ceramic suspension + monomer + initiator + foaming agents > scaffold
Result: poor microstructure, high mechanical strength
Gel-Polymer Method
ceramic suspension + monomer + initiator + foaming agents + polymer sponge > scaffold
Result: controllable microstructure, high mechanical strength
Why are chitosan/alginate composite materials superior to non-
composite chitosan materials.?
they are more biocompatible than synthetic polymers; stable at 7.4 pH; greater mechanical strength
What are tests for bone formation?
- Alcian Blue (identify cartilage)
- Alizarin Red (identify bone)
- Silver Nitrate (qualitative evaluation of Ca)
- ALP (staining)
What are the 3 types of cartilage?
hyaline (flexible and resilient; Collagen Type II)
elastic (highly bendable; Collagen Type II)
fibrocartilage (least elastic; Collagen Type I)
Perichondium
dense connective tissue sheath that covers cartilage
MACI Procedure
Cartilage TE regeneration Technique
- isolation of chondrocytes from patient
- culture of chondrocytes in vitro
- placement of chondrocytes onto a biomaterial (HA or collagen)
- implantation into lesion site and secured with fibrin glue
Regenerative Medicine
replaces or regenerates human cells, tissue, or organs, to restore or establish normal function
Cell therapy
administration of cells to the body to the benefit of the recipient
What is the goal of stem cell therapies?
transplanted stem cells come into contact with growth factors which program stem cells to differentiate into the tissue surrounding it
Hematopoietic stem cell transplantation
give rise to blood, lymphocytes and other cells of the immune system and are characterized by the presence of the CD 34 (cluster of differentiation) surface antigens
Hematopoietic Stem Cell Transplantation Uses
to treat cancer patients with leukemia, lymphoma, and sickle cell anemia and to provide a functional immune system to people with SCID
Cryobiology
Goal: cells are preserved at cryogenic temperatures, and then restored to original living states with sufficient survival rates, viability, and functionality
Cryoprotectants
chemicals that lower the freezing point of a solution; ability to form hydrogen bonds with water molecules minimizing water to water hydrogen bonding that is the basis of ice formation (preventing water from forming ice)
Penetrating Cryoprotectant Agents
intracellular cryoprotectants with low MWs that permeate the cells
Non-penetrating Cryoprotectant Agents
extracellular cryoprotectants with high MWs that do not penetrate cells; less probability of being toxic
Cell and Tissue Preservation Categories
- Freese-drying (lyophilization): does not allow effective preservation of primary cells and tissues.
- Cryopreservation: allow long term preservation of cells and tissues
3.Hypothermia: allows short term preservation of cells and tissues
Lyophilization (Freeze-Drying)
removal of ice or other frozen solvents from a material through the process of sublimation (when ice changes directly to a vapor)
Lyophilization Steps
- Freezing - product is completely frozen in a vial or flask and ice crystals form
- Vacuum - product is placed under deep vacuum where pressure is lowered
- Drying - heat is added to the material in order for water to sublime
What 4 parameters should be assessed when determining the toxicity of a cryopreservant
type of cryoprotectant
cryoprotectant concentration
time of exposure to cryoprotectant
temperature of exposure to cryoprotectant
Slow Cooling Procedure
cells are usually cooled in the presence of cryoprotectant at an optimal cooling rate; allows the cells to dehydrate by maintaining equilibrium with partially frozen extracellular solution
Purpose of vitrification
minimize ice formation/ bypass ice formation entirely
Cryopreservation safety and vapor storage
storage of samples in liquid nitrogen vapors reduce likelihood of contamination
