Ch 48 - Bone grafts and substitutes Flashcards
What lineages of differentiation are possible for mesenchymal stem cells?
- Osteoblastic
- Chondroblastic
- Adipocytic
- Tenocytic
- Myoblastic
Where are the most accessible sources of mesenchymal stem cells?
- Cambium layer of the periosteum
- Bone marrow
- Fat
What are the three mechanisms via which growth factors act on target cells?
- Autocrine: influences on cell of identical or similar phenotype in local environment
- Paracrine: Influences seen in adjacent cells of different phenotype
- Endocrine: Influences seen in different and remote populations of cells
List the main growth factors in relation to bone production
- Transforming growth factor-Beta (TGF-B)
- Bone morphogenic proteins (mostly BMP-2, -4, -7)
- Fibroblast growth factor
- Insulin-like growth factor
- Platelet-derived growth factor
In what tissues is TGF-B most commonly found?
- Bone
- Platelets
- Cartilage
From what superfamily are BMPs part of?
Transforming growth factor family
What is the main role of fibroblast growth factor?
What are the most abundant forms in the adult?
- Critical role in angiogenesis and proliferation of mesenchymal stem cells
- FGF-1 and FGF-2
What is the role is insulin-like growth factors?
- Facilitate bone and limb lengthening and cellular proliferation
Where is platelet-derived growth factor released from?
The alpha granules of platelets
What is gene therapy?
How it is delivered?
- The introduction of genetic material via noncellular or cellular material
- Introduced by physical mechanisms (electric pulsed or ultrasonic waves) or by viral vectors
What are the basic tenets of bone regeneration and grafting?
- Osteogenesis: directly supplies and supports bone-forming cells
- Osteoinduction: capacity to induce bone formation when placed into a site where no bone formation will otherwise occur
- Osteoconduction: Provides a scaffold for mesenchymal stem cells and their progeny to migrate into and proliferate
- Osteopromotive: A material or physical impetus that results in enhancement of regenerating bone
What are the 2 main forms of osteogenic material?
- Autogenous cancellous bone graft
- Bone marrow (not the same magnitude of osteogenesis)
What percentage of cells in autogenous cancellous bone graft survive at room temperature in normal saline for up to 3hr after harvesting?
When is maximum osteogenesis from autogenous cancellous bone graft?
- 60%
- Maximum osteogenesis at 8wk
What is the most common form of an osteoinductive agent?
How does it function?
What growth factors are present in the above agent?
- Demineralised bone matrix
Function:
- Recruit mesenchymas stem cells (chemoattraction and migration)
- Induce multipotent cells to multiply and become cells that make up the regenerating bony callus (proliferation and differentiation
Growth factors:
- TGF-B
- BMP-2, -4, -7
What are the characteristics of an osteoconductive agent?
Offer a scaffold for adherence of mesenchymal stem cells, osteoblasts, osteocytes, chondroblasts and chondrocytes with interconnecting porosity for cellular proliferation and, most important, vascular ingrowth